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ORIENTATION AND SURVIVAL OF HATCHLINGS AND REPRODUCTIVE

ECOLOGY OF THE COMMON SNAPPING TURTLE

(Chelydra serpentina)

IN SOUTHERN QUEBEC

by

Candace Robinson

. A Thesis submltted to the Faeulty of Graduate Studles

and Researeh of MeGlll University in partial

fulfillment of the requlrements for

the degree of Master of Science

Wlldllfe Resoutees,

Department of Renewable Resourees,

Macdonald College of McGIII University,

Montreal. Quebee, Canada.

e CANDACE ROBINSON September 1989

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ABSTRACT

The o~Ientatlon and survlval of neonate enapping

tu~tles (CheJvdca secpentIna) were studled ln 1986 and

1987. Orientation mechanisms were tested ln an outdoo~

parabo1ic arena. These experlments suggested that

positIve geotaxis was a domInant eue direeting neonate

snapp1ng turtles to water.

Hatch Il ng surv 1 va 1 and movement from nest to

wate~ we~e studied ln Calumet, Ouebec uslng Isotope

tagglng.

A hlgh1y slgnlficant number of hatchJIngs (95%)

released on sJoped nest sites wer~ positiveJy

geotactlc. Hatchllngs released on leveJ ground moved ln

random dIrections.

Eighty-two percent of hatchllngs from nests

withln 18 m of the shorel In~ we~e successfuJ ln

reachlng water. IncIdence of mortallty was greatest for

hatchl1ngs from nests between 121 and 165 m from water.

Morta11ty resulted from vehlcles and p~edatlon by

bullfrogs (&ànà katesbieana) and meadow voles (Mlcrotus

~...cnsy 1 yan 1 eus) .

Female carapace length was posItlvely correlated

wlth clutch size and mean egg dlameter. Egg dlameters

were posltlvely correlated wlth hatchllng welghts.

II

o C~utch slzes of neete more than 100 m from water w~re

larger than thoS6 closer to water •

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ABREGE

L'o~ientatlon et la survie d~s to~tues

serpentInes (Chelydra serpentIijj) ap~ès l'~closIon,

furent étudIées en 1986 et 1987. Les méchanismes

d'orientatIon ont été étudIés dans une arène

extérieure. Le mouvement des to~tue~ dans cette arène

parabolique semblait indiquer que la géotaxie positive

~tait un facteur domInant dans l'orientation des Jeunes

tQrtues ve~s l'eau.

La survie et les déplacements des Jeunes tortues

du nid ~ l'eau ont été examinés à Calumet, Québec,

chaque Individu étant marqué à l'aide d'un Isotope

l"adloac. tif.

Quatre-vingt quinze pourcent des Jeunes tortues

sorpentines qui ont emergé des nids sur les sites

inclln~s ont montré une géotaxie positIve. Les tortues

qul ont emergé des nids en te~~alns plats se sont

dlspe~sées sans direction privilégiée.

Quatre-vingt deux pourcent des tortues qul ont

emergé des nlds à moins de 18 m de l'eau ont atteInt

l'eau avec succès. Le taux de mortallté fut plus grand

pour les tortues qui ont emergé des nids situés l 121

et 165 m de l'eau. Les causes de mo~tâl1té furent les

impacts causés par des véhIcules et la prédation par

o les grenoull les d/Am~rlque <BADA çatesbleoQA) et les

campagnols (Mlcrotus pennsylvanlcus).

Une corrélation positive fut établie entre la

taIlle de la couvée, la diamètre moyen des oeufs, et la

longeur de la carapace de 10 femelle. Une corrélation

positive fut aussi trouv~e entre les diamètres des

oeufs et le poids des Jeunes tortues. Les nids situés

~ plus de 100 m de l'eau contenaient plus d'oeufs que

ceux Eltués près de l'eau.

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TABLE OF CONTENTS

ACXNOWLEDGEMENTS .......... " .................... . VIII

LI ST OF T1\BLES ..........••....•............ f'I • • •• IX

LIST OF FIGURES •.•••.•..••....•••..• f, ••••••••••• X

PREFACE .......................••................ 1

REGULATION OF THESIS PRESENTATION ••••••••••••••• 3

SECTION 1. ORIENTATION eUES USED BY

NEONATE SNAPPING TURTLES

CCbeJydra serpentlna) ••••••••••••.•• 4

NOTE ••••••.••••••••..•••••••••••••.•••••••••• 5

LITERATURE CITED ......•.....•......•.•....•.• 11

FIGURE •.•..•••.••.....•..•••••••••••••••••••• 15

CONNECTING STATEMENT .•••........ ~ . . . . . . . . . . .. 16

SECTION 2. ORIENTATION AND SURVIVAL OF

HATCHLING SNAPPING TURTLES

CCbelydra serpentlna)

AS THEY HOVE FROM THE NEST

TC WATER •••••••••••••••••••••••••••• 17

ABSTRACT •••••.•••.•.••••••••••••••••••••••••• 1 e 1 NTRODUCT 1 ON ••••••••••••••••••••••••••••••••• 20

MATERIALS AND HETHODS •••..••••••••••••• ~ ••••• 23

RESULTa .••.••••••••..••••.••••••••.•••••••••• 27

DISCUSSION ..•.......••••...••.••••••••.•.•.•• 33

LITERATURE CITED •••...••...•••••••••••••••••• 40

VI

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TABLES •..•••••••••••.•••••.••••••.••••••••••. 45

FIGURES •..•••••..•..••••..•.•••••.••••.•.•••• 47

CONNECTING STATEMENT ••••..••••••••••.•••••••• 57

SECTION 3~ SOME ASPECTS OF REPRODUCTIVE

ECOLOGY IN RELATION TO NEST DISTANCE

TO WATER OF A NORTHERN POPULATION

OF THE COMMON SNAPPING TURTLE

(Chelydra aecpentlnA) ••••••••••••••••• 58

ABSTRACT •••••••• '............................ 59

1 tlTRODUCT ION ..•.•.....•......•...•••.•....... 61

MATER 1 A LS AND METHOnS •••.•.•••••.••••••••••.• 63

RESULTS , .••• ,................................ 65

DI SCUSS 1 ON ••••••••••••••••••••••••••••••••••• 67

LITERATURE CITED ••...•••....••...••.•••.•..•• 71

FI GURES •..•••••••••.•••••..••••..••••••••••.• 74

GENERAL CONCLUS ION •..•••....••..••..•••.....• 79

VII

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ACKNOWLEDGEMENTS

1 wou 1 d II ke to express my grat 1 tude and

apprec 1 at 1 on ta ,11 those who he 1 ped and adv 1 sed me

throughou t th 1 s proJ ec t • 1 wou 1 d II ke t 0 thank my

thesls dlrector, Dr. J.R. Bider, for hls support and

for edl t l ng the rough draf ts and fi na 1 manuscr 1 pts. 1

am also grateful to hlm and Jean Philippe Auvray for

construction of the parabollc test arena.

Thanks go to my frlend and col1e:ague, Monica

Borobl a, for her encouragement and construct 1 ve

commente on the manuecrlpts.

Michel Richard of the Centre Ecologique de

Harrlngton (C.I.P. Inc.> most klndly granted me access

to the Calumet ml 11 site. Harold and Mary Dzlelak,

Regi na 1 d and Hea ther Schef fie 1 d and Den 1 e Champagne

also generously allowed me access to thelr propertles.

1 thank Simon Nadeau for hie assistance ln

translatlng the abstract lnto french. 1 would also

llke to thank Robert Blssonnette for hie constant

support and assistance.

The Natura 1 Sc 1 ence and Engl neer 1 ng Research

Councll of Canada provlded fundlng for thls research.

VIII

o LIST OF TABLES

SECTION 2

TABLE 1. SUMMARY OF FATE OF PROTECTED

NESTS AND EGGS AT CALUMET, QUEBEC~ •••. 45

TABLE 2. THE FATE OF HATCHLING

Chelvdra serpentlna FROM NESTS

LOCATED WITHIN 18 M AND BETWEEN 122 .

AND 167 M FROM THE WATER .............. 46

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L,dT OF FIGURES

SECTION 1.

FIGURE 1. H~TCHLING DISPERSAL PATTERNS FROM

SECTION 2.

FIGURE 1.

FIGURE 2a.

FIGURE 2b.

FIGURE 2c.

FIGURE 3.

THE 4 RELEASE POINTS WITHIN THE

PARABOLIC ARENA ..........•........••• 15

LOCATION OF THE STUDY AREA AND

NESTING SITES IN RELATION TO THE

OTTAWA RIVER AT CALUMET, QUEBEC ..... . 47

HATCHLING DISPERSAL PATTERNS

FROM SLOPED NEST SITES LOCATED

BETWEEN 122 AND 167 M FROM WATER .... . 49

HATCHLING DISPERSAL PATTERNS

FROM 2 NESTS LOCATED ON LEVEL

GROUND ••••••••••••••••••••••••••••••• 51

HATCHLING DISPERSAL PATTERN

FROM SLOPED NEST SITES

LOCATED WITHIN 18 M OF WATER ........ . 53

THE RELATIONSHIP BETWEEN THE

ANGLE OF HATCHLING DISPERSAL

FROM THE NEST AND THE

SECTION 3.

FIGURE 1. THE RELATIONSHIP BETWEEN CLUTCH

SIZE AND FEMALE CARAPACE LENGTH •..... 73

FIGURE 2. THE RELATIONSHIP BETWEEN MEAN EGG

DIAMETER AND FEMALE CARAPACE LENGTH ... 75

FIGURE 3. THE FREQUENCY DISTRIBUTION OF

CLUTCH SIZE FOR NESTS LOCATED

< 100 M FROM WATER AND NESTS

LOCATED> 100 M FROM WATER .•••••..••• 77

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PREFACE

The common snapping turtle (Chelydra serpentina)

ls widely distrlbuted ln many permanent freshwater

habitats ln North America. Whlle many aspects of the

basIc blology of thla species have been studied,

knowledge of the orIentation and survival of hatchlings

as they emerge from the nee:t and move to wa ter i s

limited. In addition, whlle the characterlstlcs of nest

al tes have been frequent 1 y descr ibed, the ef fect of

nest site selection on reproductive success ia poorly

understood. The primary objectives of thls study

were:l) to examine the orientatIon cues used by neonate

snapplng turtles ln a setting where environmental

factors could be controlled; 2) to Investlgate the

orIentation and aurvival of neonate snapping turtles in

the field, as they travel trom the nest to water; and

3) to gain a better understanding of the reproductive

strategies of this species by examlnlng some female

reproductive characterlstics as they relate to nest

distance from water.

In 1986 and 1987 field data were collected on

the extent of nest failure, timing and patterns of

hatchling emeroence, hatchllng movement and

orientation and hatchling mortality. Radioactive

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o Isotopes we~e used to tag hatchllngs ln o~de~ to follow

thel~ movements f~om the nest to wate~. Most data on

female size, clutch slze, egg slze, hatchllng size and

nest dIstance to wate~ were eollected ln 1987.

As pe~mItted by the Faculty of G~aduate Studles,

thls thesls contains the texts of th~ee manusc~lpts to

be submltted to Jou~nals fo~ publication. The flrst,

presented in Section 1, deals wlth the o~Ientatlon eues

used by neonate snapplng tu~tles ln an outdoor

parabol:~ arena. The second, p~esented ln Section 2,

examInes the o~lentation and su~vlval of hatehling

snapp 1 ng tu~t 1 es 1 n the fie 1 d as they move from the

nest to wate~.- The thl~d, p~esented ln Section 3,

examines sorne aspects of ~eproductlve ecol ogy ,

Includlng female slze and clutch size, as they ~elate

to nest dIstance f~om wate~. The flret manuscript will

be sent to the Jou~nal of Herpetol ogy , the second to

Copela, and the thlrc! to Herpetologlca, with Dr J.R.

Bider as eo-autho~. The style of eaeh manuscrlpt le

that ol the Journal to whleh It will be submltted.

Data collection and analysls were ear~led out

1 ndependant 1 y by the ~uthor. Re f erences. t ab 1 es and

figures appea~ after the manuec~lpt ln whlch they a~e

clted.

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TH!SIS OFFICE STATEMENT

The candidate has the option, subJect to the

approva 1 of the Deptartment, of 1 nc 1 udl ng as part -of

the thesle the text of an original paper, or paper;e,

sultable for submlsslon to learned Journals for

publication. In thle case the thesls must still

conform to aIl other; requlrements explalned ln thle

document, and addltlonal materlal, (e.g. experlmental

data, detalle of equlpment and experimental design) May

need to be provlded. In Any case abstract, full

Introductlon and cnncluslon must be Included, and where

more than one manuecr;lpt appear;e, connectlng texte and

common abstract Introduction and conclusions ar;e

requlred. A mere co] 1 ect Ion of manuscr 1 pts 1 s not

ac'.:eptable~ nor can reprints of publlshed papers be

accepted.

Whlie the Inclusion of manuscrlpts co-author;ed

by the Candidate and others Is not prohlbl ted for a

test perlod, the candidate Is warned to make an

expllclt statement on who contrlbuted to such work and

to what extent, and supervisors and others will have to

bear wltness to the accuracy of such clalms befor;e the

oral commlttee. It should also be noted that the task

of the External Examiner 18 much more dlfflcult ln such

cases.

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SECTION 1

ORIENTATION CUES USED BY NEONATE SNAPPING TURTLES

• (Che)vdra lerpentlna)

-,.,,) . , , ' .....

* Note for submllslon to the Journal of Herpetology

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The maJorlty of etudies on the orientation of

hatch Il ng turt 1 es from the nest to water have

concentrat~d on marine specles. Research on the

orientatIon mechanlsm~ of the loggerhead turtle

(Caretta caretta) and green turtle (Chelonla rnvdae)

have focussed prlmarlly on vlsual eues InvolvIn~ llght

Intenslty, color and horIzon effeets (Hooker, 1908;

Parker, 1922; Daniel and SmIth, 1947; Caldwell and

Ca 1 dwe 11, 1962; MeFar 1 ane, 1962; Ehrenfe 1 d and Carr,

1957; Mrosovsky and Carr, 1967; Ehrenfeld, 1968:

Mrosovsky and Shettleworth, 1968; Mrosovsky, 1972).

OrIentatIon to magnetle fIelds has been ruled out as a

meehanlsm ln loggerhead hatehllngs (Parker, 1922).

Reports on the effeets of sI ope on hateh Il ng

orIentation are eontradietory. Parker (1922) found

loggerhead hatehllngs to be posltlvely geotaetle.

Other studies of sea turtles lndleated that lmpalrment

of vIs ion resu 1 t sIn a loss of or 1 en t a t Ion ab 1 II t Y

regardless of slope (Caldwell and Caldwell, 1962;

Ehre~feld and Carr, 1967; Ehrenfeld, 1968).

Terrestrlal orientation in freshwater hatehllnge

may oeeur over greater dIstances and ln the absence of

simple eues sueh as lhose assoelated wlth beaeh

topography (Ehrenfeld, 1979). Noble and Breslau (1938)

demonstrated that snapplng turtle hatchllngs exhlblted

negative geotaxis ln the dark. In a study of 3

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freshwater speeles, Anderson (1958) suggested that

orIentation proeesses might involve a negative response

to dark masses. A positive response to areas of bright

li ght, the posi t i r.:>n of the sun and hum! di ty grad! ents

have also been proposed as important eues for snapplr;

turtle hatehllngs, following laboratory tests (Noble

and B~eslau, 1938).

Five possible orIentation meehanisms have been

dlseu9sed ln the 1 Iterature: (1) visual eues, e.g.: the

slght of water, horizon effeets and Jight lntenslty,

(2) olfaetory eues, (3) orientation to magnet'e fields,

(4) a response to moi sture gradients, and (S) geotaxls.

In view of the mlx~d opinions, and prelimlnary tests on

a sma11 slope board whieh indleated that snapping

turt1es might be positively geotaetie, we sought to

study hatehling movement in an open (outdoor) arena

where at least geotaxis, orientatIon to magnetie flelQs

and the role of sorne visual eues might be evaluated.

The tests were eondueted ln a way that elimlnated the

vlsual eues associated with an open or bJoeked horizon

wlthout blIndlr.g the animaIs. In this !!I~ .. udy the term

positive ~eotaxls i9 defined as moving down a gravitv

gradient. The defininltlon of this term has

oecasionaJly been eonfused ln the literature.

Twenty snapplng turtle hatehllngs were observed

ln an outdoor arena loeated in the Macdonald College

wil dli fe area at Ste-Anne-de-Be 1 J evue! Gluebee. The

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parabolle clreular arena had a dlameter of 12 m and was

1 m deep (Flg.l). The maximum slope wae 100 whlle at

the base of the parabola, the slope decreaeed ta 20 to

form a relatlvely fIat area, 50 cm wlde. A fIat area

30 cm w 1 de ene 1 rc 1 ed the upper edge of the parabo 1 a.

The area was enclosed by a galvanlzed steel wall 0.5 m

ln helght. A chlld's plastic ewlrrmlng pool, 1.5 m ln

dlameter was eunk Into the center of the parabola. The

pool was filled with pond water and eorne aquatlc

veget:at Ion. Cl umps of 10w, herbaceous growth covered

approxlmately 60% of the arena.

Snapplng turtle eggs frorn 2 nests were collected

at Calumet, Quebec CLat. 450 38' Long. 740 39')

(Robinson and Bider. 1988) and were Incubated Indoors.

Ten emergl ng hateh II ngs were ee 1 eeted at randorn from

eaeh and an Identification number was palnted on the

baek of each hatchllng. Groups of 5 hatchJ Inge were

then reburled ln molst vermlcullte ln 4 Inch (10.16cm)

flower pots and the pots were burled Into the rlm ln

the aide of the parabola 4 m from the pool ln each of

tha 4 cardinal directions. The dIstance and direction

of each hatchling from the release poInt were recorded

every 5 min. untll It reached the water. Experimente

were conducted ln the late afternoon on clear sunny

days ln early September wlth temperatures ranglng

between 18-220 C.

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Upon emergl ng frcm the pote a 11 hatch li nge

paused and appeared to scan thelr surroundlngs. Each

ha tch 1 1 ng moved 1 ndependen t 1 Y of the others. AlI of

the hatchllngs moved downhll1 trom the pot towards the

pool, pauslng occaslonally. Thlrteen reached the water

dlrectly wlthout bypasslng the pool. Seven hatchllngs

passed wlthln 0.3 m of the pool edge, and contlnued up

the other sI de. Upon reach 1 ng the- ou ter edge of the

arena they elther turned around and contlnued down to

the pool, or they followed the arena wall for several

meters and then descended to the pool (Fig.l).

AlI hatchllngs eventually reached the water, and

once 1 n the poo 1 tended to rema 1 n submerged unt 1 1

removed hours 1 ater. The maximum and mInimum tlmes

taken to reach water were 161 and 6 min., respectlvely.

The mean t i me t aken by those wh i ch en tered the POv l

dlrectly was 13 mins (n=13; 5.E.=2.05) and the Mean

tlme taken by those whlch passed the pool was 72 mins

(n=7; S.E.=21.11). The average speed of aIl hatchlings

was 0.39 ml mIn. (S.E.=0.03).

Slnce aIl hatchllngs went downhl11 from the

release pOints and 35% did not go dlrectly to water, a

good deal of Inference may be made wlth regard to the 5

orientatIon mechanlsms mentloned in the 11terature.

The low parabo 1 a wa II created a constant,

unlnterrupted horizon, thus the horIzon was not bJocked

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nor was there a brlght open horizon assoclated wlth the

water. Neverthe 1 ess, aIl of the hatch II ngs r-eaehed

water. Whl1e these results do nct rule out the use of

the vlsual cues of blocked or open horlz~ns when they

oceur ln natural situations, they do Indleate that

hatehl1ngs can orient to water ln thelr absence. The

direct vlsual eue uf seelng the water had no bearlng on

orientation, sinee 7 of the 20 hatchllngs passed wlthln

a few centlmeters (and ln clear vlew) of the pool, yet

cont 1 nued up the other ~1 de of the parabol a wl thout

stopplng.

The 01 factory cues of water appeared to have

llttle effect on orientation, given the proxlmlty of

the 7 hatehllngs that bypassed the pool. This supports

the flndlngs of Noble and Breslau (1938) who noted that

snapplng turtle hatchl1ngs exhlblted no slgniflcant

r-esponse to the odor of river water or food.

Desplte the dlfferent release tlmes and

locations of the 4 groups tested, aIl hatchllngs moved

downh III 1 n the dl rect Ion of the poo 1 . These resu 1 te

suggest that snapplng turt'e hatehllngs are not uslng

orientation to magnetic fields as a cue in thelr

approach to water , nor Is thelr movement affected by

the position of the sun. S!nce the hatchllngs

orlglnated from 2 nests loeated approxlmately 100 km

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from the test si te, or lentat ion to water cannot be

related to any Innate knowledge of the nestlng area.

Nob Je and Bres 1 au (1938) noted tha t enapp 1 ng

turtle hatchllngs dlsplayed a tendency to move towards

an area of greater huml dl ty. In thls experlment the

molsture gradient waS s11mlnated and yet hatchl1ngs

orlented successfully to water.

Noble and Breslau (1938) found that hatchJlngs

of thls species showed a marked tendency to move uphll1

ln the dark, a behavlor that mlght facllitate thelr

escape from the nest. We dld not test hatchl1ngs ln

the dark, however ln the dayllght aIl hatchllngs moved .

downhlll from the release poInt. In the re 1 at 1 ve 1 y

fIat areas at the base and around the upper rlm of the

parabola hatchl1ngs frequently changed direction,

moving away from the water.

In summary. our data are not consistent wlth the

use of visual eues, olfactory eues, orientation to

magnetlc fields, or molsture gradients as ori~lltatlon

mechaniems. Gravit y ln dayllght appears to be the

dominant eue dlrectlng snapplng turtles downhll1 to

water.

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LITERATURE CITED

Anderson, P.K. 1958. The photlc responses and

water-approach behavlour of hatchllng turtles.

Copela 1958: 211-215

Caldwell, M.C. and O.K. Caldwell. 1962. Factors ln the

abillty of the northeastern PacIfie green turtle to

orient toward the sea fram the land, a possible

coordlnate ln long range navigation. Contrlb. Sel.

60: 1-27.

Daniel, R.S. and K.U. SmIth. 1947. The sea-approach

behavlor of the neonate loggerhead turtle (Caretta

caretta). J. Comp. Physlol. Psychol.40: 413-420.

Ehrenfeld, D.W. 1968. The role of vIsIon ln the

sea-flndlng orientation of the green turtle

(Chelonia mydas) 2. OrIentation mechanlsm and

range of spectral sensltlvity. Anim. Behav. 16:

281-287.

Ehrenfeld, D.W. 1979. Behavlor assoclated wlth nestlng.

In: Turtles: perspectives and research. Edlted by M.

Harless and H. Morlock. John Wlley and Sons. New

York. pp.417-434.

Ehrenfeld. D.W. and A. Carro 1967. The role of vision

11

o ln the sea-flndlng orientation of the green turtle

(Che)QclA mydas). Anlm. Behav. 15:25-36.

Hooker,D. 1908. Prellmlnary observations on the

behavlor of seme newly hatched loggerhead turtles

(Tha)asso~eJya caretta). Yearbook CarnegIe Inst.

Wash. 6: 111-112.

McFarlane, R.W. 1962. Dlsorl~ntatlon of 10ggerhead

hatchllngs by artlflclaJ road 11ghtlng. Copela 1963:

153.

Hr.osovsky, N. 1972. The water-flndlng abllity of sea

turtles. Behavloral studles and physlologlcal

speculations. BraIn Behav. Evol.5: 202-225.

Hrosovsky, N. and A. Carr.1967. Preference for 1lght of

short wavelengths ln hatchllng green sea turtle

Cheloola mydas. tested on thelr natural nestlng

beaches. Behavlour 28: 217-231.

Hrosovsky, N. and S.J. Shettleworth. 1968. Wavelength

preferences and brIghtness cues ln the waterflndlng

behavlour of sea turtles. Behavlour 32: 211-257.

Noble, G.K. and A.M. Breslau. 1938. The senses Involved

ln the mIgration of young fresh-water turtle~ after

hatchlng. J. Camp. Psychol. 25: 175-193.

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Parker, G.X. 1922. The crawllng of young )oggerhead

turtJes toward the sea. J. Exp. Zoo). 36: 323-331.

Robinson, C. and J.R. Blder.1988. Nestlng synchrony - A

stategy to decrease predation of snapplng turtle

CChelvdra serpeotlna) nests. J. Herp. 22:470-473.

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-- ---------- ---_ .. _--------------------

FIGURE 1. HATCHLING DISPERSAL PATTERNS FRCM

THE 4 RELEASE POINTS WITHIN THE

PARABOLIC ARENA

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·--1 1

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, - - - - - - -.6 m. - - - - - 1 l:m .... -

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o 5 J ,

meters

R.P.-Release Point

o Pool

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CONNECTING STATEMENT

Section 1 descrlbed the orientation cues used by

hatchllng snapplng turtles ln an experlmental parabollc

arena.

Section 2 examines orientation, movement, and

survlval of hatchllng snapplng turtles ln the field •

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SECTION 2

ORIENTATION AND SURVIVAL OF HATCHLING SNAPPING TURTLES

(Cbelydro serpentIna) AS THEY MOVE FROM THE NEST TO

WATER

* For submlsslon to Copela

17

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~, .: ~' ...

ABSTRACT

The orIentation and survlval of hatchllng snapping

turtles was studied in 1986 and 1987 at Calumet.

Duebec. Seventy-f 1 ve percent of neste protected from

predators were partially successful wlth sorne

hatchllngs emerglng. while 25% falled completely.

Flfty-slx percent of eggs produced hatchllngs that

emerged successfully, 31% of embryos dled durlng

development and 12% of e~gs were Infertile.

The maJority of clutches (80%) emerged ln

September. The average number of days' trom egg

deposltlon to emergence was 96. Nlnety-flve percent of

hatchllngs emerged between 0700-1800 hours .

One hundred and flfty-slx hatchllngs (95%) whlch

emerged from sloped nest sItes moved downhill. There

was a slgnlflcant negatlve Ilnear relatlonshlp between

the angle of hatchllng dispersal from the nest and the

slope of the ne~t site. Vegetation dld not affect the

dl rect Ion of hatch II ng movement. Hatch Il ngs re 1 eased

on level ground dlspersed randomly from the nest.

Elghty-two percent of hatchlings frcm nests located

wlthln 18 m of the shorellne were successful ln

reachlng water. Mortallty was hlghest for hatchllngs

travelling from distant nests and was caused by

18

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preda t Ion and veh 1 c 1 es • !WO hatchllngs were preyed

upon by bullfrogs (RAnA catesbelAna) At the water's

edge and 8 hatchllngs were preyed upon by meadow voles

(Mlccotys pennsylYAnlcys) ln a grassy fIeld.

19

o 1 NTRODUCTI ON

The common snapplng turtle (ChelydrA .erpentina)

ls a long Ilved (Gibbons, 1987) and wldely dlstrlbuted

specles, ranglng Into 80uthern Canada west to the

Rockles and south to the Gulf of Mexico (Conant, 1975).

It occure ln many permanent freehwater habitats (Ernst

and Barbour, 1972; Conant, 1975;) and plays an

Important role ln marsh ecology (Hammer, 1969). Many

aspects of snapplng turtle blology have been studled,

lncludlng: adult movement and migration (Moslmann and

Bider, 1960; Hammer, 1969; Obbard And Brooks, 1980;

Obbard and BrC1oks, 1981b; Ga 1 bra 1 th et al., 1987) ,

reproductive ecology (Yntema., 1970: White and Murphy,

1973; Congdon et alo, 1987), neetlng ecology (Hamilton,

1940, Hammer, 1969; Wllhoft et al., 1979; Petokas and

Alexander, 1980; Obbard and Brooks, 1981A~ Congdon et

aJ., 1987; Robinson and BIder, 1988), population

denslty (Major, 1975; Galbraith et al., 1988), and

habitat preferences (Sexton, 1958; Froese, 1978; Obbard

and Brooks, 1981b). Few etudies, however, have

Investlgated the behavlor of turtle hatchllngs as the y

emerge fram the nest and make thelr way to water

(Burger, 1976). Whlle predation on nests appeaes to be

a major determinant of neet survlval (Ernst and

Barbou~, 1972; Tlnkle et al., 1981; Robinson and Bider,

20

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1988) other factors that mlght Influence nest success

and hatchllng survlval followlng emergence have

recelved Infrequent evaluatlon. Hatchllng emergence

was 1 ess than 20 " for undl sturbed nests 1 n South

Dakota (Hanmer, 1969) and an e.verage of 4.14 eggs or

embryos dled ln nests that esc4ped predation ln

MiChigan (Congdon et al., 1987). Obbard and Brooks

(1981a) have examlned the fate of overwintered clutches

ln an OntarIo populatIon and reported that of 129

clutches that dld not emerge ln the fall and escaped

predatIon, only one overwlntered successful1y.

Research examl n 1 ng ha tch 11 ng movement and

orientation to water has focussed prlmarlly on marine

specles. Knowledge of thls toplc concernlng freshwater

hatchllngs Is rudlmentary (Ehrenfeld, 1979). Noble and

Breslau (1938) tested a number of potentlal

water-flndlng cues under laboratory conditIons, us!ng

snapplng turtle, stlnkpot (SternotherYs odoratus), and

palnted turtle (Chrvsemys plcta) hatchllngs and

demonstrated a positive response to are as of brlght

Illumination and humidity gradIents. Two signiflcant

field studies ln thls area are those of Burger (1976)

on the diamondback terrapln (Malaclemys teerApln~. and

Anderson (1958), on the smooth sof tshe 1 1 (Trignyx

mut 1 eus). the Al abama map turt 1 e (GroptemYI!!I PY] chea),

and the ri nged eawback (Graptemys oey] 1 fera) • Burger

21

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( 1976), examl ned the emergence pat terne of hatch Il ngs

by followlng thelr tracks on the sand dunes. On sloped

sItes hatchlings moved downhlll, however the location

of the nearest vegetatIon was a stronger orientational

st Imu 1 us than 1 nc li ne. Anderson ( 1958) tested

or lentat Ion mechan 1 SlnS w i th mazes and by observ 1 ng

hatch 11 ng tracks 1 n the sand. The resu 1 ts of th 1 s

study suggested that hatchllngs exhiblted a negatlve

response to dat"k masses. These studl es re Il ed on the

observation of tracks or the direct and constant

observa t i on of each hatch 1 1 ng. Ne 1 ther study reported

on the success of hatchllngs in reaching the water, nor

on the type or extent of pr-edation suffered after­

leavlng the nest site •

The object 1 ves of the present study were to

Investlgate: (1) the extent of nest fallures when

predators are excluded: (2) the t!mlng and patter-ns of

hatchl1ng emer-gence; (3) the behavlor, mo"ement, and

orientation of hatchllngs over differ-ent terraIn and at

va['lous dlst~nces from the water; (4) the extent and

causes of mor-ta lit Y as hatch 11 ngs make the 1 [' way to

wate['. ThIs resea['ch Is the fi ['st IntensIve field

study of the o['lentatlon and sur-vlval of snapplng

tu['t 1 e ha tch 1 1 ngs as they move f['om the nest to water

and fIl 19 a gap ln our knowledge of the Ilfe hlstory of

thls specles.

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MATERIALS AND HETHOnS

This study was carrled out at Calumet, OUebec

(1 at. 45 38' , long. 74 39' >. The si te Includes a

narrow, T shaped, malnly fIat plece of land (m111 site)

approxlmate1y 1 km ln length, that extends eouthward

Into the Ottawa RIver (Fig. 1>. To the north of the

mlll site the land slopes upward gradually. This area

extends east about 1 kl10meter to the flret houses ln

the vIllage. The land near the rallroad tracke Is sandy

and sparee 1 y covered w 1 th grasses, wh II e most of the

sI ope down t 0 the river cone 1 st s of ml xed hardwood

forest, endlng wlth a dense band of wll10w (Sallx mL.,)

and aIder (Alnys ~) at the water's edge. Much of

the old mlll sIte le covered wlth woody and herbaceous

pioneer vegetation. &,oad fIat areas of woodchlps wlth

little or no vegetation except lichen are present ln

the north-central area.

Fleld work wae conducted from 15 May to 5

Oc;-tober 1 n 1986 and 1987. The site was v 1 si ted da Il y

untll nestlng began, after which It was vlslted at

leaet twlce dally untll the end of the nesting season.

Each year, 10 nests were located and protected

tram predators uslng heavy metal screens that measured

60 by 90cm. The nest sites were se1ected on the basle

of thelr substrates, slopes and dIstance fram the

23

,0 river. Nest sites have been found either close to the

water « lBm) or far from lt (121-165m) and the sample

reflects the relatIve proportIon of nests at each sIte.

Where nests cou 1 d not be adeq'.Jate 1 y protected from

vehlcles, they were collected and lncubated Indoors at

240 C, ln flowerpots fl11ed wlth vermlcullte.

After the nestlng season, the protected nests

were checked every second day. Durlng the second and

th 1 rd weeks of August the screens were rep 1 aced wl th

cyllndrlcal baskets (30 cm dlameter, 16 cm helght)

constructed of 0.5 inch (1.27cm) rnesh hardware clotho

Each cyllnder was burled to a depth of 8-10 cm ln order

to contaln emerglng hatchl1ngs. Followlng the f lrst

si gn of emergence, each nest was checked da Il yin the

mornlng and at nlght. The date and tlrne of day when

hatchllngs emerged were recorded and they were rernoved

from the enc 1 osure. Nests were aIl excavated dur 1 ng

the fi rst week of October and 2 unhatched eggs from

each were dlssected. If these eggs were found to

con ta 1 n lIve embryos the nest was rebur 1 ed and 1 ef t

Intact untll the following sprlng. When no live

embryos were found, the remalnlng eggs were dlssected.

The number of i nfert Il e eggs, dead embryos and dead

hatchllngs was recorded for each nest.

24

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AB many aB 10-15 individu.la were aelected at

random from each nest group and identification numbers

were palnted ente their carapaces. Snapplng turt 1 e

hatchl ings are very cryptic and ln thlck vegetatIon

they become virtually Invisible to the human observer.

For th 1 s reason ha t ch 1 1 ngs were a 1 se marked w!th the

radl oact 1 ve 1 sotope, Zn 65. The tag was prepared by

comblnlng a smal1 quantlty of Metal based palnt with

radIoactive ZnCI dry salts. The mixture was then

applled onto a strlp of plastic wrap. The strlp was

wrapped around a spool and small chIps were cut off as

needed. A chlp measurlng approxlmately 3 mm2

contalning 0.02 mlcrocurles of radIoactive material was

attached to the dorsal surface of a marginal scute on

each hatchling wi th acryllc adheslve. This procedure

took approxlmately 10 mIn durlng whlch tlme hatchlings

were handled as little as possible.

Marked hatch 1 i ngs were re 1 eased at the nest

site. The initial direction in whlch each was faced

for release was chosen at random by slldlng hatchllngs

out of a container; no partlcular directIon was

favoured. Every 10 minutes durlng the day each

hatchllng was located uslng a sclntilator counter,

(Ludlum 3 survey meter) wlth a 2 in (5.08cm) dlameter

prObe (mode 1 4410) • Slnce hatchllngs remalned

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re 1 at 1 ve 1 y 1 nact 1 ve at ni ght, they were on 1 y tracked

from 0700-1800 hrs. Wherever possible, hatchllngs were

monltored for 2 days after the y entered the water. The

detect Ion range of the counter was approx Imate 1 y 1 m

and ha tch Il ngs were f ound by sweep 1 ng the area 1 n an

1 ncreas 1 ng arc. Once il hatch! Ing was located, the

position was marked wlth a ~take and the distance and

dl~ectlen from the nest were recorded. AlI hatchl1ngs

were fo)) owed unt Il they el ther r~ache:d the water, were

kllled o~ were lest. Wheneve~ possible the causes of

mortallty were determlned. In 2 Instances, 3 Longworth

traps were set out ln an attempt to identlfy pr~dators

whlch had killed and carried hatchllngs underground.

26

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RESULTS

Hest Survlval

Of a total of 20 nests protected from predators,

5 falled completely and none hatched aIl of the eggs

wlthln (Table 1>' Of the falled nests, 3 located on

woodchlp substrate contalned embryos that died early ln

the 1 r deve 1 opment and 2 located on grave 1 substrate

contalned eggs wlth living embryos that still had not

hatched by J ate fa 1 J and presumabJ y dl ed over wl nter.

One nest observed ln 1986 contained embryos that were

almost fully developed ln October. The fol10wlng

sprlng 2 live hatchllngs ernerged trom thls nest.

Overa Il, emergence 1 ncreased f rom 47.4% 1 n 1986

te 64.2% ln 1987. Most deaths (30.8%) occurred ln the

embryonlc stages. Infertl10 eggs accounted for 12% of

losses and 1.3% of eggs hatched but did not emerge.

Hatchllng Emergence

The Mean numbeL of days from the deposltlon of

eggs 1 n the spr 1 ng to ha tch Il ng emergence in the fa 11

was 96 (N=14: range 82-107: SE= 1.09). On 1 y one nest

produced hatchllngs ln the sprlng. Emergence fram the

nest that overwlntered eccurred sornet Ime prlor to 18

May. The t Ime taken by hatch Il ngs to emerge from

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""----------------

Indlvldual nesta varled. Synchronoua emergence la

deflned here as aIl hatchllngs havlng emerged wlthln a

perlod of 24 hrs while asynchronous emergence refers to

hatchllngs having emerged over a perlod greater than

24h. Hatchlings emerged asynchronously from 9 (64.3%)

nests over a period of 2-4 days, whlle emergence from 5

(35.7%) nests was synchronous. There was no

slgnlflcant difference ln the proportion of nests from

which emergence was synchronous and asynchronous (X2 =

1.14 P> 0.05). Most hatchl1ngs emerged between

0700-1800 hours dur i ng day Il ght • Only 16 hatchllngs

(4%) from 3 of the 14 nests emerged between 1800-0700 .

Movement and OrIentatIon of Hatchllngs

A total of 180 hatch I1ngs were marked and

followed from the ne st sI te. Dispersal patterns from

17 nests were mapped (Fig 2-a.b,c). Three of these

nests were 1 ncubated 1 ndoors but hatch 11 ngs were

released at the original nest sites. Flfteen (88%) of

the nest si tes were on sI opes rangl ng from 40 to 380 •

A hlghly slgniflcant number of hatchllngs, 156 (95.1%),

observed on sloped nest sites were posltlvely

geotactlc. (X2 =133.56: P<O.OOl).

There was a slgnlflcant negatlve llnear

relatlonshlp between the angle of hatchllng dlspersal

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fram the nest wlthln the flret 10 m, and the slope at

the nest site CSlmple Ilnear regreaelon; F 1,1S- 15.76:

P<O.OI; Fig. 3). !wo of the sloped nest sites were

characterlzed by land sloplng away ln 2 directions

(FIg.2a). thus when measur 1 ng the angl e of hatch II ng

dlepersal, each slope was consldered separately.

The 16 hatchllngs released on fIat nest sites

moved ln aIl dlrectl~ns CFIg.2b). Calculatlons of the

mean angle of dlsplacement were followed by evaluatlon

of the angular dispersion Cclrcular standard

devlatlon>. Uslng Raylelgh~s test lt was determlned

that there was no elgnlflcant mean dlrectlonallty ln

the dlpersal of hatchllngs on each of the 2 fIat nest

sites (Rayleigh/a test, nest 1 z-O.242 P>0.05; ne st 2

z-O. 972. P>O. 05,. Hatch II ngs from 2 nests 1 n 1986

dlspersed wldely as they crossed a fIat section of road

CFlg 2a>.

Hatchllngs were most active between 0700-1800

hours and very Ilttle movement was observed after dark.

When fi ret re 1 eased at the nest si te, a JI hatch 11 nge

remalned immobile, extended thelr necks and appeared to

scan the area. This stop and scan behavlor wae

exhlblted perlodlcally, and was observed whl)e

hatch II ngs weie both 1 n the open or under cover. 1 t

appeared to be performed most frequently when there was

movement ln the hatchllngs~ llne of vision. The hlgh

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denslty of vegetation around many neste made It

dlfflcult to determlne whether or not hatchllngs were

movlng towards the nearest coyer. The 2 neete on leve1

ground, however, were located ln woodchlp fields wlth

only eparse clumps of vegetation, and as prevlously

lndlcated, hatchllngs at theee sites exhibited no

preference for Any specific direction.

The river was not visible frorn a hatchllng's

perspectlv~ for 6 of the 17 nests and Indlvlduals frorn

9 nests passed through dense vegetat Ion through wh 1 ch

ne 1 ther the water nor a br 1 ght open hor 1 zon cou 1 d be

seen.

When hatch II ngs stopped mov 1 ng for extended

periode of tlme <usually overnlght), the y burrowed Into

the ground and were vlrtually Impossible to see.

Movemen t was observed dur 1 ng heavy prec 1 p 1 ta t Ion, as

we lIas on Wl.rm sunny and coo 1 overcast days. Sorne

hatchllngs occaslonally stopped movlng for several

hours, and euch behavlor was observed on both wet and

dry days, and through a wlde range of temperatures.

The average tlme taken by hatchllngs to reach

water was 2 hrs. 56 mine. for nests located less than

18 m from water, and 65 hrs. 15 mlns. for nests

sltuated between 121-167 m fram water.

After f Irst entering the river, hatchllngs

remalned ln ehallow areas « 15cm deep) and elther

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burrowed Into the substrate or moved lnto nearby

aquatlc vegetation. The maJorlty of hatchllngs (82%)

etayed wlthln 10m of where they entered the water for

the 2 days they were monltored.

Hatchllng Survlval

The fate of hatchllngs from nests located less

than 18 m fram the water was determlned (Table 2). A

maJorlty of hatchl Inge from these neste (72.5% and

82.5% ln 1986 and 1987 respectlvely) were successful ln

reachlng water. Wh1le no Instances of predatlon were

observed 1 n 1986, 2 ha t ch 11 ngs were preyed upon by

bu llfrogs CRAnA catesbe 1 ana) 1 n 1987. 1 n both cases

hatchllngs were preyed upon as they entered the water.

On another occasIon, although no predation occurred, a

) arge garter snake (Thamnophls Sirta"ils alrtalls) was

observed followlng a hatchl1ng for several meters

through dense vegetation. Great blue herons (Ardea

herod1as) were frequently seen feedlng ln the shallows

where hatchllngs dlsappeared fram, but emlgratlon

cannet be [yled out.

The fate of hatch 11 ngs from nests located

between 122-167 m fram water le summarlzed ln Table 2.

Hatchllngs from these nests suffered hlgher mortallty

th an those from nests that were close to water.

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Mortall ty was caused by both predat Ion and paeslng

vehlcles as turtles crossed the road. AlI Instances of

predation ln 1986 occurred overnlght whlle hatchllngs

were wlthln 20 m of the r.est sites. Seven partlal1y

eaten hatchllng carcasses were found ln a network of

burl"ows 'C.hat wel"e 1 ocated 1 n an sandy meadow. Three

longworth traps, balted wlth dead hatchllngs, were set

near the burrow entrances for 2 nlghts. One meadow vole

(Mlcrotys pennsylyanlcus) was caught durlng thls

perlod. Only ~ne hatchl1ng was preyed upon ln 1987 and

th ls predat ion occurred overn 1 ght 40 m fran the nest

site on a graesy slope. The remalns of thls hatchllng

were also found ln a burrow. The condition of the

carcass was slmllar to those found ln 1986, however,

nothlng was caught ln 4 nlghts of trapping. These 1987

nest sites were sltuated on the gravel shoulder of a

road, over 60 m east of the 1986 nest sites. In 1986,

4 hatch 11 ngs were run over as they crossed a fIat

section of the road on thelr way to water. Nests ln

1987 were J ocated al ong a sloped sect 1 on of the road

and 4 hatchllngs fram these nests were kl11ed as they

moved down thls slope.

The fate of hatchllngs that were lost by the

observer- ln thlck vegetation Is llsted as unknown ln

Table 2.

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DISCUSSION

Nest Survlval

Hatchllngs emerged from 15 of the 20 protected

neste whlch Is a conslderably hlgher euccess rate than

was reported for South Dakota (Hammer, 1969) wher-e

hatch Il ngs elnerged from on 1 y B of 22 protected nests.

Nest predatIon ls an important factor reduclng

nest surv 1 va lin th 1 s popu 1 at Ion of snapp 1 ng tur-t 1 es

(RobInson and BIder. 1988), and It le apparent that the

pr-esence of lnfertlle eggs, as weIl as the mortal1ty of

developlng embryos and hatchl1ngs also serve to

decrease nestlng success.

Two types of complete nest fallur-e were observed

ln th 1 s study. In the f 1 ret type embryos appeared to

have dl ed ear) y dur 1 ng the 1 ncubat Ion peI' 1 od. Slnce

only nests deposlted ln the woodchlp substrate suffered

th 1 s type of f a Il ure, 1 t seems Il ke) y tha t the

substrate was ln sorne way r-esponslble. Decomposing

s01,twood chIps are acldlc and perlodlc examlnatlon of

th i s substrate throughout the sunmer revea) ed that 1 t

remalned very wet below 4 cm.

In the second type of nest fal1ur-e, embryos wer-e

a Il ve al though not fu Il y deve 1 oped ln the fa Il and

33

o mor-ta 11 ty was pr-esumabl y caused by fr-eez 1 ng 1 n the

wlnter. Embryos ln these nests may have had

Insufflclent tlme to develop slnce the partlally

shaded condl t Ions at the nest si te may have lowered

temperatures Inslde the nest. These results are

comparable to those of Congdon et al.(1987), who

suggested that low Incubation temperatures related to

fully shaded nests caused 11.8% of nest tallures ln

those nests that escaped predation.

Hatchllng Emergence

The average number of days fram egg deposltlon

to hatchllng emergence ln the Calumet populatIon (96

days) was slmllar to that reported for- southern

MichIgan (93.2 days; Congdon et al. 1987) and the range

of 90-119 days reported for 3 hests in Ontario (Obbard

and Brooks, 1981b). AIl but one clutch emerged ln the

fall and the clutch that emerged ln the sprlng pr-oduced

on 1 y Z II ve hatch II ngs. These hatch Il ngs may have

avolded fr-eezlng because the nest was located at the

slde of the rallr-oad tracks where snow Is pl1ed deep ln

wlnter-. Obbard and Brooks (1981a) clted a slmllar- hlgh

snow accumulation for the 1 nest that successfully

overwlntered ln thelr study. While delayed emer-gence

has been reported for thls specles (Toner, 1940;

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Bleakney, 1963; Ernst, 1966; GIbbons and Nelson, 1978,

Obbard and Brooks, 1981a) Most hatchllngs ln Ontario

(Obbard and Brooks, 1981a), Michigan (Sexton,1957;

Congdon et al., 1987) and South Dakota (Hanmer, 1969) ,

emerge ln the fall.

Hatchllngs ln thls study emerged synchronously

and asynchronously as dld hatchllngs ln Michigan

(Congdon et al., 1987). Ninety-six percent of

hatchlings ln this study emerged durlng dayllght hours.

Burger (1976) reported simllar emergence times for

dlamonclLack terrapln hntchllngs. In contrast, green

sea turtle ~Chelonla mvdas) hatchlings exhlblt

nocturnal emergence, controlled by thermal lnhlbl tlon

of activity (Morovsky, 1968).

Movement and OrientatIon of Hatchl1ngs

Hatchlings fram nests on slopes moved downh111

whlle hatchllngs on fIat la~ld moved randanly,

exhlbItlng no dlrectlonal preference. Burger (1976)

documented slmi lar dispersal patterns for dlmondback

terrapln hstchl1ngs, but noted that the location of

nearest vegetation was a stronger directional stimulu~

than 1 nc Il ne. Snapp 1 ng turt 1 e hatch Il ngs showed no

preference for the directIon of the nearest vegetation

ln fIat areas, and It therefore seems unl1kely that the

35

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location of cover ls Important ln the orientation of

thls specles. Noble and Breslau (1938) conducted

laboratory tests on the e-ffect of slope on snapplng

turtle hatchllngs ln the dark and noted that hatchllngs

exhlblted a marked tendency to move uphill. Whl1e thls

behavlor may facllitate emergence fram the nest (Noble

and Breslau. 1938>. lt would appear to have llttle

effeet on hatchllngs as they move to water. slnee Most

hatch Il ngs emerged 1 n day Il ght and ceased mov 1 ng by

ni gh t fa Il • In contrast, dlamondback terrapln

hatehllngs emerged durlng the day but made thelr way

rapld1y to the nearest vegetation where they remalned

untll nlghtfall (Burger, 1976).

The angle of snapplng turtle hatchllng dispersal

from the nest varled Inversely wlth the slope at the

nest site. Hatchllngs dlspersed fram as much as 1580

on cl slope of 40 to as llttle as 26° on a slope of

38°. Slmllarly, Burger (1976) reported that

dlamondback terrapln hatchllngs dld nct disperse more

than 300 on slopes greater than 100 , whereas, on s10pes

of less than 100 the y dlspersed more than 750 •

Noble and Breslau (1938) demonstrated that

anapplng turtle hatchllngs were attraeted to areaa of

hlgh humldlty and brlght Illumination. They euggested

that an open hor 1 zon, the presence of humldl ty

gradients and the position of the~ sun mlght be

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important eues for orientatIon. A negatlve response to

dark masses of vegetation may also be Involved in the

orientation of sorne freshwater hatchllngs (Anderson,

1958). Humldlty gradients dld not appear to be

neceesary for orientation in thle etudy, eince

hatchllngs moved successfully to water through

eaturated areas, and durlng heavy precipitation. Over

half of the hatchllngs passed through dense vegetation

which obscured any vlew of the water, the sun or the

open horizon. Nevertheless, hatchlings contlnued to

orient slJccessfully to water. The results of thls

study suggest that positive geotaxls 115 the most

Important factor dlrectlng snapplng turtle hatchllngs

to water.

Once ln the water hatchllngs tended to remaln ln

the shal10ws whlch ls consistent wlth the 11mlted

swlmmlng abllity reported for thle age group (Hammer,

1969). Hatchllngs elther burrowed Into the substrate

or moved to aquat 1 c vegetat 1 on. Such behavlor may

provlde enhanced protection, concealment (Froese, 1978)

and ln the case of vegetation, physlcal support

(Sexton, 1958).

37

o

_. -- ._ .... _._---------.,

Hatchllng Survlval

The type and extent a'! hatch 11 ng marta II ty

appeared ta be lnfluenced by at lea!lt 3 factorts: (1)

the amount of tlme that hatchllngs were vulnerable to

predation, (2) the type of habitat through whlch

hatchllngs travel1ed and the predators assoclated wlth

those habl tats, and (3) the presence of roads near

nestlng areas. Hatchllngs fram distant nests spent at

1 east one n 1 gh t on 1 and and a II preda t 1 on on these

Indlvlduals was nocturnal. Hatchl1nga fram nests that

were close ta water usua 11 y reached the river before -nlghtfal1 and were therefore not vulnerable ta

nocturnal terrestrlal predators. AIl nacturna 1

predation, apparently by meadow voles, occurred ln

sandy, weIl dralned fields, whereas diurnal predation

by bullfrogs occurred along the water's edge. Due to

the presence of the observer, the resulte of thls study

may underestlmate the extent of diurnal predation. lt

1 saI sa possi bl e that sorne of the hatch II ngs lost 1 n

thlck vegetation were preyed upon. Law diurnal

predation however, would be consistent wlth the d1urnal

emergence and actlvlty patterns observed for most

hatch Il ngs.

38

(

(

(

Vehlcles passlng on a road accounted for some

hatchllng mortallty ln each of the 4 nests located near

1 t. Hatch Il ngs mov 1 ng on the road decreased the 1 r

chances of surv! va 1 by stopp 1 ng and scann 1 ng the area

every tlme a vehlcle passed, and thereby remalnlng on

the road for a considerable length of tlme. Whlle It

la dlfflcult to determine the purpoae of the stop and

scan behavlor, It appeared to be assoclated Most often

wlth movement ln the hatchl1ngs' llne of vision and

thus, mlght be related to predator avoldance.

In conclusion, the survlvorship of neonate

snapplng turtles was affected by a number of factors

related to female ne st site selection includlng: nest

dl stance from water, the type of habl tat surroundl ng

the nest and the presence of nearby roade. Further

research le needed however, to underetand the factors

whlch affect survlval of hatchllngs once they reach the

water.

39

o LITERATURE CITED

Ande~son, P.l. 1958. The wate~-app~oach behavlor of

hatchllng tu~tles. Copela 1958: 211-215.

Bleakney. J.S. 1963. Notes on the dlst~lbutlon and life

hlsto~les of tu~tles ln Nova Scotla. Cano FIeld-Nat.

77: 67-76.

Bu~ge~, J. 1976. BehavioL of hatchllng diamondback

te~~aplns (Malaclemys te~rapln) ln the fIeld.

Copela 1976: 742-748.

Conant, R. 1975. A FIeld GuIde to Reptiles and

Amphlblans of Easte~n and Cent~al No~th Ame~lca. 2nd

Edition. Houghton Mlfflln, Boston.

Congdon, J.O., G.L. Breitenbach, R.C. Van Loben Sels,

and D.W. Tlnkle. 1987. Rep~oduction dnd nestlng

ecology of snapplng tu~tles (Chelydra serpentlna)

ln southeaste~n Michigan. He~petologlca 43: 39-54.

Ehrenfeld. D.W. 1979. Behavlor assoclated wlth nestlng.

In: Tu~tles: pe~spectlves and ~esea~ch. Edlted by

M. Ha~less and H. Mo~lock. John Wlley and Sons. ~ew

Yo~k. pp.417-434.

40

(

(

(

• ft SI'

Ernst, C.H. 1966. Overwlnterlng of hatchllng Chelydra

serpentlna ln southeastern PennsylvanIa.

PhIl. He~petol. Soc. Bull .14: 8-9.

Ernst, C.H. and R.W. Barbour. 1972. Turtles ~f the

United States. Unlvet'sity Pt'ess of Toronto, Toronto.

Ft'oese, A.D. 1978. HabItat preferences of the common

snapplng tut'tle, Chelydra set'pentlna (Reptilla,

Testudlnes, Chelydrldae). J. Herpetol. 12: 53-58.

Galbra1th, D.A., C.A. B1shop, R.J. Brooks, W.L. Slmser

and K.P. Lampman. 1988. Facto~s affectlng the denslty

of populations of common snapplng turtles (Chelydra

aorpentina serpeutlna). Cano J. 2001. 66:

1233-1240.

GalbraIth, D.A., M.W. Chandler and R.J. Brooks. 1987.

The fIne structut'e of home ranges of male Cbelydra

serpentina: are snapplng tut'tles terrItorial? Cano

J. Zool. 65: 2623-2629.

GIbbons, J.W. 1987. Why do turtles lIve so long?

BloSclence 37: 262-267.

GIbbons, J.W. and D.H. Nels~n. 1978. ~he evolutlonary

slgnlflcance of delayed emergence ft'am the nest. by

hatchllng turtles. EvolutIon 32: 297-303.

41

o Hamilton, W.J., J~ .1940. Observations on the

reproductive behavlor of the snapping tu~tle.

Copela 1940: 124-126.

H~e~, D.A. 1969. Parametere of a marsh snapplng

turtle population, Lacreek Refuge, South Dakota. J.

WIldl. Manage. ~3:995-1005.

MaJor, P.D. 1975. Denslty of enapplng turtles,

Chelvdra serpentlna, ln western West Vlrglnla.

He~petologlca 31: 332-335.

Moslmann, J.E. and J.R. Bider. 1960. Variation, sexual

dlmorphlsm, and maturlty ln a Quebec populatIon of

the common snapplng turtle, Chelvdra serpentina.

Cano J. Z~ol. 38: 19-38.

Morovsky, N. 1968. Nocturnal eme~gence of hatchl1ng sea

tu~tles: control by thermal Inhibition of actlvlty.

Nature ~20: 1338-1339.

Noble, G.K. and A.M. Breslau. 1938. The senses Involved

ln the migration of young fresh-water turtles after

hatchlng. J. Comp. Psychol. 25: 175-193.

Obbard, M.E. and R.J. Brooks. 1980. Nestlng migrations

of the common snapplng turtle Chelvdra

aerpentlna. Herpetologica 36: 158-162.

42

(

(

_____ • 1981a. Fate of overwlntered clutches of the

commen snapplng turtle (CheJydr~ serpentlnl) ln

Algonquin Park, Ontario. Cano Field-Nat. 95:

350-352.

_____ . 1981b. A radlo-telemetry and mark-recapture

study of actlvlty ln the eommon snapplng turtle.

~~ .erpentlna. Copela 1981: 630-637.

Petokas, P.J. and M.M. Alexander. 1980. The nestlng of

Cbelydra .erpentlna ln northern New York. J.

Herpetol. 14: 239-244.

Robinson, C. and J.R. Bider. 1988. Nestlng synchrony- a

strategy to decrease predation of snapplng turtle

(Cbelydra .erpentlna) nests. J. Herpetol. 22:

470-473.

Sexton, O.J. 1957. Notes eoncernlng turtle hatchllngs.

Capela 1957: 229-230 •

. 1958. The relatlonshlp between the habitat

preferences of hatchllng Cbelydra serpentIn. and

the physlcal structure of the vegetation. Ecology 39:

751-754.

Tlnkle, D.W., J.D. Congdon. and P.C. Rosen. 1981.

Nestlng frequency and suceess: Implications fer the

demography of painted turtles. EcoJogy 62: 1426-1432.

43

o Toner, G.C. 1940. Delayed hatchlng ln the snapplng

turtle. Capela 1940: 265.

White, J.B. and G.G. Murphy. 1973. The reproductive

cycle and sexual dlmorphlsm of the common snapplng

turtle, Chelydra .erpentlna serpentlna.

Herpetologlca 29: 240-246.

Wllhoft, D.C., M.G. Del Bagllvo and M.D. Del Bagllvo.

1979. Observations on mammallan predatlon of snapplng

turtle neste (Reptllla, Testudlnes, Chelydrldae). J.

Herpetol. 13: 435-438.

Yntema, C.L. 1970. Observations on females and eggs of

the common enapplng turtle Chetydra serpentlna.

Am. MidI. Nat. 84: 69-76.

44

(

~ 1

1

" f

,

f , (: l-

f" f . 1-

~ ,

(

TABLE 1: SUMMARY OF FATE OF PROTECTED NESTS ~ND

EGGS AT CALUMET, QUEBEC

1986 1987

TOTAL NUMBER OF NESTS PROTECTED 10 10

NUMBER OF FAILED NESTS 3 2

TOTAL NUMBER OF EGGS 350 360 IN ALL NESTS

N % N %

HATCHLINGS EMERGED 166 47.4 231 64.2

INFERTILE EGGS 26 7.4 59 16.4

DEAD EMBRYOS 149 42.6 70 19.4

DEAD HATCHLINGS (IN NEST) 9 2.6 0 0.0

45

TOTAL

20

5

710

N %

397 55.9

85 12.0

219 30.8

9 1 .3

o

f) ........

TABLE 2: THE FATE OF HATCHLING Cbelydra serpentlna

FROM NESTS LOCATED WITHIN 18 M AND BETWEEN

122 AND 167 M FROM THE WATER

NUMBER 'OF HATCHLINGS FROM NESTS < 18 M FROM WATER

1986

58

N " REACHED WATER 48 72.5

PREYED UPON 0 0.0

UNKNOWN 10 27.5

NUMBER OF HATCHLINGS FROM NESTS 23 BETWEEN 122-167 M FROM WATER

N " REACHED WATER 6 26.0

PREYED UPON 7 30.5

KILLED BY VEHICLES -4 17.5

UNKNOWN 6 26.0

46

1987 TOTAL

79 137

N " N " 64 82.5 112 81.7

2 2.5 2 1.5

13 15.0 23 16.8

20 43

N " N " 15 75.0 21 48.8

1 5.0 8 18.6

4 20.0 8 18.6

0 0.0 6 14.0

c

(

(

FIGURE 1. LOCATION OF THE STUDY AREA AND

NESTING SITES IN RELATION TO THE

OTTAWA RIVER AT CALUMET, QUEBEC

47

(

(

(

FIGURE 2a. HATCHLING DISPERSAL PATTERNS

FROM SLOPED NEST SITES LOCATED

BETWEEN 122 AND 167 M FROM WATER

(Each 11ne Indlcates the path of

one hatchl1ng)

49

o

t)

w a.. ~=7#~=~

, ,

, , ,

w C-o ..J (/)

, ,

, ,

" , .. -

, .... / ..

.....

SLOPE----Ir~ v~

- ~/'-- ~ (./ 1'- ~ _ _ u... - .... -.......... , ..................... /"" ~- .... _ ..... .

ln

... .. .. .. ... :'

....

".

o 50 , , meters

ROAD

(

(

(

FIGURE 2b. HATCHLING DISPERSAL PATTERNS

FROM 2 NESTS LOCATED ON LEVEL

GROUND

(Each l1ne Indlcates the path of

one hatch 11 ng)

51

o

\ , ,

o 50 1 ~--:--_..JI

meters

o , meters

10 1

(

(

(

FIGURE 2c. HATCHLING DISPERSAL PATTERNS

FROM SLOPED NEST SITES

LOCATED WITHIN 18 M OF WATER

(Each 11ne Indlcates the path of

one hatchl1ng)

53

o

w Cl.. o ..J rn

w C-O ..J rn

10"

o 10 , , meters

o 5 1 1

meters

l f 1 }

l !

(

(

(

FIGURE 3. THE RELATIONSHIP BETWEEN THE

ANGLE OF HATCHLING DISPERSAL

FROM THE NEST AND THE

SLOPE AT THE NEST SITE

o

180 N -17

..J Y·136.14 - 2.93X < 160·

(/) • r - 0.72 a: w 140

, c.. • (/) • -c 120 C) Z

100 ;j, -..J d J:

U 80 ~ ::c 11.. 60 0 W 40 ..J C) z 20 <

0 0 10 20 30 40

SLOPE (degrees)

(

(~

r.i ,

(

CONNECTING STATEMENT

Section 2 consldered the orientation, movement

and survlval of hatchllng snapplng turtles ln the

field. The results obtalned durlng the flrst field

season of th 1 s study, al ong \ri lth genera 1 observa t ions

made durlng prevlous years, Indlcated that 20% to 25%

of females nest at distances greater than 100 m from

water. The advantages of thls behavior, If Any, are

unknown.

Section 3 deals with selected aspects of female

snapplng turtle reproductive ecology including clutch

size and reproductive effort ln relation to nest

dIstance from water.

57

o

SECTION 3

SOME ASPECTS OF REPRODUCTIVE ECOLOGY IN RELATION TO

NEST DISTANCE TO WATER OF A NORTHERN POPULATION OF THE

COMMON SNAPPING TURTLE (Cbelydrl serpentinl)

*For submlsslon to Herpetologlca

(~

ABSTRACT

Aspects of the reproductIve ecology of a

i'opulatlon of common snapplng turtles (Chelydra

aerpentlna) were studied from May to October (1987) ln

Calumet, Ouebec. During 3 years of observatIon It was

noted that 20-25% of snapplng turtle nests were

deposited at distances greater than 100m from water.

The reasons for dIstant nesting were not apparent,

wh1ch led to the examlnatlon of some of the

reprOductive characteristlcs of nestlng females. The

nests wer-e protected from predators. Hatchllngs wer-e

we 1 ghed upon emergence in the fa Il • The carapace

1 engths of 19 repr-oduct 1 ve fema les r-anged fr-om 211 -

348 mm. The mean clutch size was 33.78 while the mean

egg dlameter was 27.20 mm. Clutch size and Mean egg

dlameter- wer-e posItlvely related to female carapace

length. There was a slgnlficant positIve correlation

between egg dl ameter and hatch Il ng we 1 ght. The mean

straight Ilne dIstance from nests to the nearest

aquatlc habitat was 45 m, (range 4.86 - 173.00 m). The

maJorlty of nests (74%) were located wlthln 42 m of the

water whlle 26% of nests were 10cated between 121 - 173

m. Four of fi ve dl stant nesters were 1 arge fema 1 es.

There was a slgnUlcant dlfference between the mean

59

o cJutch size of nests located close to water and those

Jocated far fram lt, wlth distant nests havlng Jarger

clutches.

( INTRODUCTION

The character 1 st 1 cs of snapp 1 ng turt 1 e nest

sItes have been descrlbed ln the literature (Lonke and

Obbard, 1977: Petokas and Alexander, 1980; Congdon et

al. , 1987; Rob i nson and Bi der, 1988). Neverthe 1 ess,

the relationship between nest site selection factors

and reprOductive success are poorlY understood. Whi1e

sorne females nest relatlvely far from water (as far as

181m in Michigan) these nests are not reported to have

Increased survlvorshlp by decreaslng nest predatIon

(Congdon et al.,1987). Over several years It has been

observed that between 20% to 25% of females at Calumet,

nest far (> 100m) from water. The advantages of th 1 s

are not apparent, however the costs of travel could be

balanced by reproductive characterlstlcs such as better

incubation conditions at the nest site, increased

hatchl1ng survlval following emergence, or safety from

floodlng.

Whlle the common snapping turtle has been wldely

studled (White and Murphy, 1972) it ls a specles for

whlch many parameters of reproduction are poorly known

CPetokas and Alexander, 1980). Mean clutch sizes for

different reglons vary from 19.9 to 49 eggs/ clutch

CHanmer, 1969: Yntema 1970: White and Murphy, 1973:

61

o

----------------------

Lonke and Obbard, 1977: Petokas and Alexander, 1980;

Congdon and Gibbons, 1985: Congdon et al., 1987) and

posl t 1 ve re 1 at lonsh Ips ex 1 st between adu 1 t body slze

and the clutch size of Many polkl10therms (Bluewelss et

al., 1978>' A positive relatlonshlp between female

body size and clutch slze has been demonstrated ln a

number of snapplng turtle populations (Vntema, 1970:

White and Murphy, 1973: Congdon and Gibbons, 1985:

Congdon et al., 1987), as weIl as a positive

relationshlp between femaJe slz~ and egg size (Yntema,

1970; Congdon and Gibbons, 1985; Congdon et al., 1987).

There are very few publlshed data documentlng hatchllng . sI ze for th 1 s spec 1 es. Morr 1 s et al. (1983) observed

that larger eggs tended to produce larger hatchllngs ln

the labot"atot"y.

The purpose of this study was: (1) to examine

the t"elatlonships between female size and clutch sIze,

egg size and hatchllng slze, (2) to examine nest

distance from water as it t"elates to clutch size and

femaJe reprOductive effort.

62

(

(~

(

METHODS AND MATERIALS

The study was conducted ln 1987 at Calumet,

Quebec (Lat. 45 38', Long. 74 39'). The study site was

vlslted dally from mld May untll the onset of the

nestlng aeason. Durlng the nestlng season fram 29 May

to 20 June the site was vlslted 3 tlmes dally, before

0800 hours, at noon and 1 hour before dusk. Followlng

the nestln; season, the nest sites were vlsited every

second day untll the first sion of hatchling emergence,

after whlch nest sites were checked mornlng and evenlng

untll mid October.

When a female had completed nestln;, she was

captured and carapace len;th and wldth vere measut'ed

uslng a metric ruler. Eggs were carefully removed and

counted. and egg dlameters wet'e measured to the nea~est

0.01mm uslng callpers. Followlng excavation eggs vere

returned ta the egg chamber and the solI vas replaced.

Four of the 19 nests were not excavated because females

nested synchronousl y and the obset'ver vas unabl e to

excavate some of these nesta dlrectly after deposltlon.

It wes feared that handllng the eggs from these nests

1ater on mlght reduce hatchabl1lty. Heavy metal

ecreens measur 1 ng 90 by 60 cm were p laced over the

nests. The distance fram the nest to the nearest water

o was recorded. For analysls of the relatlonshlp between

clutch size and nest distance fran water, addltiona}

data gathered ln 1986 were comblned wlth data fram thls

study ln order to obtaln a larger sample.

1 n ml d August the screens were removed and

rep 1 aced wl th _cy II ndr 1 ca 1 baskets constructed of 0.5

Inch (1.27 cm) hardware cloth measurlng 30 cm ln

dlameter and 18 cm ln helght. Cyllnder walls were

burled to a depth of 8 to 10 cm ln order to prevent

emerglng hatchllngs from escaplng. Upon emergence,

hatchllngs were welghed uslng a triple beam balance . accurate to 0.1 gm.

(

(

(

RESULTS

Female Size and Clutch Parameters

Female carapace length averaged 279mm and ranged

from 211II1I'I to 348nvn (N 1: 19: SE == 8.89). The mean

carapace wldth was 233.6mm ranglng fram 179 - 295mm (N

- 19; SE == 7.05). The mean clutch slze was 33.78 (N =

19: range = 18 - 52: SE = 2.32). A slgnlflcant

positive llnear relatlonshlp was found to exlst between

clutch slze and female carapace length (Simple llnear

regresslon: Fl.17 • 41.33: P (0.01. Flg.1).

The overall mean for egg dlameters fram 15 clutches

was 27. 20nvn ( N = 521; range == 23.50 - 32.31; SE -

0.05). Mean egg diameter exhlblted a slgnlflcant

positive 11near relatlonshlp wlth female carapace

length (simple llnear regresslon: F1,13 e 10.44: P (

0.01. Fig. 2>-

Hatchllng welghts from 12 clutches had a mean of

8.1g (N 1: 291: range z 4.5 - 10.3g: SE = 0.09). There

wae a slgnlflcant correlatIon between egg dlameter and

hatchllng welght (Spearman's r = 0.62; 0.01 < p <

0.05) •

The maJorlty (63%) of clutches contalned between 20

to 40 eggs whlle 10.5% had fewer than 20 eggs and 26%,

more than 40.

o

-; i. " l

Nest DIstance From Water

The mean straight line dIstance fram nests to

the nearest permanent water was 45m (N = 19: range =

4.86 - 173.00; SE = 13.21), The major 1 ty of nests

(74%) were 10cated wlthln 42m of the water, whi1e the

remalning mests (26%) were situated between 121 to 173m

from water.

The relatlonshlp between female size and nest

distance from water was not 1inear, however 4 of the 5

most distant nesters were large fema1es whi1e those

nestlng close to water were bath large and small. Sorne

data gathered in 1986 on clutch slze and nest dIstance

from water for 12 nests were comblned wl th the data

from thls study ln order to obtaln a 1arger eamp1e.

There was a slgnl flcant dlfference between the mean

clutch elze of nests located wlthin 100 m of the water

and the mean clutch slze of those located further than

100 m from water CStudent"s t: t= -2.41, p<O.05>.

Distant nests contained primarlly large clutches white

both 1 arge and sma Ile 1 utches were located close to

water (Fig. 3). Given the positive relatlonshlp

between clutch elze and female slze, It le probable

that the distant nesters were large females.

66

(

(~

(

DISCUSSION

Female elze and Clutch Pa~amete~s

The mean clutch slze found ln thls study (33.8)

1 s compa~abJ e to thoee repo~ted for othe~ northern

localltles Includlng: 33.9 ln Ontario (Lonke and

Obba~d, 1977); 30.9 ln northe~n New York (Petokas and

Alexander, 1980) and 27.9 ln Michigan (Congdon et aJ.,

1987>' Fu~ther south howeve~, clutches appear to be

smaller wl th reported mean clutch slzes of 19.9 ln

Tennessee (White and Mu~phy, 1973) and 23.6 ln No~th

Carol Ina (Congdon and Gibbons, 1985).

A elgnlflcant positive reJatlonshlp between female

body slze and clutch size was found ln this study whlch

corresponds wlth prevlous reports of thls relatlonshlp

ln enapplng turtJes (Congdon et aJ., 1987; Yntema,

1973; Congdon and GI bbons, 1985: Wh 1 te and Murphy,

1973), and ln othe~ freshwater turtle specles (Gibbons,

1982>'

The mean egg dlameter (27.20 mm) le smaller than

the means of 28.4 mm reported by Petokas and Alexander

(1980) ln New York, and 31.00 mm reported by Congdon et

al., (1987) ln Michigan, but greater than the means

26.8 mm reported by Yntema (1973), and 25.78 mm

reported by Congdon and Gibbon (1985) in No~th

Carol Ina. The demographlc slgnlflcance of these

measurements ls unclear. Mean egg dlameter exh1blted a

slgn1f1cant positive relatlonship with female carapace

length. This ls slmllar to reports by Congdon et al

(1987), Congdon and Gibbons (1985), and Yntema (1970) ,

al1 of whom found a positive relatlonshlp between

female bOdy size and egg size but used dlfferent

measurements (body Maas, egg Maas and plastron length)

for their comparisons.

The '.lean hatchllng we1ght of 8.1 g. ls slmllar

to the Mean hatchl1ng welght of 8.9 g. reported by

Congdon et al. (1987) ln Michigan. Larger eggs tended

to produce 1 arger hatch II ngs and th i S corresponds to

the findings of Morris et al. (1983) who measured these

trends under control1ed laboratory conditions. Morris

et al., (1983) suggested that hatchl1ng size could be

Influenced by the slze of the eggs at ovlposltlon, and

by the hydr 1 c condl t Ion of the nest substrate chosen.

In the present study the dlfference ln hatchl1ng slze

due to egg size and female size was observed regardless

of the variable hydrie conditions of the weIl dralned

up 1 and nest si tes and the mol st nest si tes located

closer to water. Thus hydrie conditions at the nest

si tes di d not appear to compensate for the observed

differences ln hatchllng slze related to egg slze.

l

(

(~

(

Nest Distance from Water

Whlle the maJorlty of females nested close to .

the water_ seme travelled much farther and over rougher

terrain to nest <Robinson and Blder,1988). The results

of thls study Indlcate that while both large and small

clutches are deposited close to water, lt Is prlmarl1y

large clutches, presumably lald by large females, that

are located far from water. Larger females produce

larger cJutches and Jarger eggs whlch, ln turn, produce

larger hatchlings. It seems llkely that larger females

and larger hatchllngs would be best able to cope wlth

the rlsks assoclated wlth dIstant neBts. Females expend

more energy and lncur a greater rlsK from predation and

water loss ln these longer trips as do the hatchllngs

that emerge from these nests. It therefore seems

llkely that some beneflt could be derlved to compensate

for these costs. However, nests that are both near and

far from the water are equaJly susceptible to predatIon

(Congdon et al., 1987). Hatchlln~ survlval does not

appear to be lncreased at distant nest sItes and

hatchllngs fram distant nests suffer higher mortality

caused by both predators and vehlcles (Robinson and

BIder, SectIon 2). The advantages of distant nestlng

may be re 1 ated to lmproved 1 ncubat Ion' condl t Ions at

these well-drained open sites.

o

-

Inte~estingly, at least 3 females we~e killed

between 1984 and 1987 on a 0.5 km st~etch of road whlle

crosslng durlng the nestlng season. In vlew of thls

mortallty and that of emerglng hatchllngs (Robinson and

BideL, Section 2) due to tLafflc, It 19 appa~ent that

the road has a steady negative Impact on tULtles

nest1ng faL from wateL. Thus, although rlghts of way

create good, open nest1ng habitat at sorne distance from

wateL, they may be ecological tLaps that negate Any

advantages that could be galned fram better incubation

conditions.

(

---- -- ------____ ., __ ._il:lM .... ,-.... sr. _________________ •

LITERATURE CITED

Blueweles, L., H. Fox, V. Xudzna, D. Nakashlma, P.

Petera, and S. Sams. 1978. Relatlonshlps between

body slze and some 11fe hlstory parameters.

Oecologla 37: 257-272.

Congdon, J.D., G.L. BreItenbach, R.C. Van Loben Sels,

and D.W. Tlnkle. 1987. Reproduction and nestlng

ecology of snapplng turtles Chelvdra .erpentlna

ln southeastern Michigan. Herpetologlca 43: 39-54.

Congdon, J.D. and J.W. Gibbons. 1985. Egg components

and reproductive characterlstlcs of turtles:

retationships to body size. Herpetologlca 41:

194-205.

Gibbons, J.W. 1982. Reproductive patterns ln freshwater

turtles. Herpetologlca 38: 222-227.

Hammer, D.~. 1969. Parameters of a marsh snapplng

turtle population: Lacreek Refuge South Dakota. J.

Wlldllfe Mgmt. 33: 995-1005.

Lonke, D.J. and M. Obbard. 1977. Tag success,

dImensions, clutch slze and nestlng fldellty for the

anapplng turtle, Chelydra B.C,2entlna, ln

Algonquin Park, OntarIo, Canada. J. Herpetol. 11:

242-244.

71

o Morris, K.A .• G.e. Packard, T.J. Boardman. G.L.

Paukstis and M.J. Paekard. 1983. Effeet of the hydrie

envlronment on growth of embryonle enapplng turtles

(Chelvdra serpentlna). Herpetologlea 39:

272-285.

Petokas, P.J. and M.M. Alexander. 1980. The nestlng of

Chelvdra serpentina ln northern New York. J.

Herpetol. 14: 239-244.

Robinson, C. and J.R. Bider. 1988. Nesting eynehrony -

a etrategy to deer&ase predation of snapping turtle

(Chelydra serpentlnl) nests. J. Herpetol.

22:470-473.

White, J.B. and G.G. Murphy. 1973. The reproductive

cycle and sexual dlmorphlsm of the common snapplng

turtle. Herpetologlea 29: 240-246.

Yntema, C.L. 1970. Observations on females and eggs of

the common snapplng turt1e, Chelydra serpentlna.

Am. MidI. Nat. 84: 69-76.

(

FIGURE 1. THE REL~TIONSHIP BETWEEN CLUTCH

SI2E (y) ~ND FEMALE CARAPACE LENGTH (X)

(~

( 73

o

(1) N v; .!:. U -.2 U

.....

--

4J

3J

y= -27.55 + O.22x r = 0.84 n= 19

• •

10 ~--r-~--T-~--~~--~~--~~---~~I----~I--~

220 240 200 320 ~

Carapace Length (mm)

FIGURE 2. THE RELATIONSHIP BETWEEN MEAN EGG

DIAMETER (y) AND FEMALE CARAPACE LENGTH ex)

(~

(

75

o

'29 Y = 2.34 + O.OO13x r = 0.66 - n = 1:5 E • • • E 28 • ....." ...

(l) --Q.) • E • • 0 27 -. • -- • ëS ........

f 0> ---.. ".. 0 UJ • C • 0 26 • Q.) • ~

25 1 1

2X) 220 24J 2éO 200 lX) 320

Carapace Length (mm)

(

(~

FIGURE 3. THE FREQUENCY DISTRIBUTION OF

CLUTCH SIZE FOR NESTS LOCATED

< 100 M FROM WATER AND NESTS

LOCATED > 100 M FROM WATER

77

o

Nests located < lOOm frem water 5

4 n=22

3

2

0 o 10 15 Al 25 ::0 35 4) 45 5.J 55 8J - >-

i~ (J "" .. c

Q) ... .... cr Q) ~

LI..

Nests Iccated > 100m from WOTer

5 n=9

4

3

2

o~--------------~--~~~~--~--~-----5 10 15 2) 25 J) 35 4) 45 5J 55 éD

Clutch Size

(

(~

-, ft

GENERAL CONCLUSION

In a test ar'ena, positive geotaxls ln dayllght

eeemed to be the dominant eue dir'ectlng snapplng tUr'tle

hateh Il ngs dO\Jnh 111 to water' wh II e v 1 sua 1 and 01 faetor-y

eues, orientation by magnetic fields and molstur-e

gradl ei1ts appear'ed to be of li t t 1 e Impor'tance. The

maJor-ltyof hatehl1ngs movlng from sloped nest sites ln

the field wer'e also posltlvely geotaetie. In fIat

areas hateh Il ngs di sper'sed 1 n ail dl r'eet Ions and were

not attracted to near'by vegetation.

Infertile eggs and the death of hatehllngs and

developlng embr'Yos r'esulted ln the failure of almost

half of aIl eggs observed and ther-efore appear to be

Important factor's in overall nest sUr'vlvor-ship.

Furthermore, the type and extent of hatehling

mortality fol lowlng emer-gence appear-ed to be Influeneed

by the distance of the nest from water and thus, the

amount of tlme hatchlings wer-e vulne["able to p["edatlon.

the typP. of habItat through whleh hatchllngs tr'avelled,

the pr-edato["s assoclated wl th those habl tats and the

pr'esence of r-oads near the nestlng Ar-ea.

An examlnatlon of sorne female r'epr-oduetlve

characterlstics lndieated that clutch slze and Mean egg

diameter' wer-e positlvely related to female car'apace

79

o

-\ ~ "

-l,

length. There was a positive correlation between egg

d1emeter and hatchl1ng welght. Whlle the maJorlty of

females nest close to water, approxlmately 20" to 25"

nest farther than 100 m from water. The mean clutch

si ze of dl stant nests () 100 m) was 1 arger than the

mean cl utch si ze of nests located cl oser to water.

Glven the relatlonshlp between clutch elze and fernale

slze, distant nesters were probably large females.

80