Hatchling Orientation During DispersalHatchling Orientation During Dispersalfrom Nests

Experimental analyses of an early life stagecomparing orientation and dispersal patterns of hatchlings that emerge from nests close to and far from wetlands

Weaver Dunes, Minnesota

Blanding’s Turtles (Threatened) Nests far from marshBlanding s Turtles (Threatened) – Nests far from marsh(mean = 622 m, 70 -1380 m, n = 138)

Snapping Turtles (Special Concern) – Nests close to marsh( )(mean = 75 m, 5 – 270 m, n = 87)

Painted Turtles (Harvested) – (mean = 65 m, 2 – 190 m, n = 113)

Life Histories• Age specific schedules of reproduction and death• Longevity and long reproductive lifespan

D l d l i• Delayed sexual maturity• Low annual fecundity• High and unpredictable nest mortality ratesg p y• in most cases.• For some species:

Indeterminate growth (older = larger)– Indeterminate growth (older = larger)• High average annual survival of juveniles from

– age 1 to first reproductiong p“Evolutionary life history patterns are just as much a part of what

organism is as are its anatomy, physiology, and morphology.” George Williams

Why hatchling orientation is important in the t t f lif hi t icontext of life-histories

Stable populations of long lived organisms with lowStable populations of long-lived organisms with low fecundity and delayed sexual maturity (i.e. turtles), require high average annual survivorships ) q g g pof juveniles.

Average juvenile survivorships of Blanding’s and S i t tl b th > 0 72 (C d t lSnapping turtles were both > 0.72 (Congdon et al. 1993, 1994).

Factors that handicap hatchlings during dispersalFactors that handicap hatchlings during dispersal from nests (and cause increased mortality) will result in requiring higher survivorships at

bsubsequent ages.

After emerging from nests, most hatchling freshwater turtles face a majorhatchling freshwater turtles face a major problem - finding suitable wetlands

The abilities and tactics of water finding by hatchlings co-evolvedfinding by hatchlings co evolved with the nesting tactics of females

Therefore, patterns of co-evolution of nesting tactics and hatchling orientation and dispersal

h ld b id ishould be evident among species and and families of turtles.

Relative constraints on terrestrial movementsRelative constraints on terrestrial movements

EB CS CPEB CS CPAdults Hats Adults Hats Adults Hats

• Predator + + + +• Predator - + - + + +• Desiccation - - + + - -

Potential Mechanisms

Random dispersal (the null hypothesis)

POTENTIAL CUES FOR NON-RANDOM DISPERSALNegative geotaxis (go down hill)PhototaxisChemotaxis (olfaction)H iditHumidityAuditory cuesSocial facilitation (scent trailing)Social facilitation (scent trailing)

DEVELOPED SKILLSPiloting based on landmarks gCompass orientation (e.g., sun compass)True navigation (requires a map and compass)

Weaver Dunes

Dunes600 h Miss

Marshes1200 h

Miss.River

1200 h

Weaver Bottoms

1500 h

Experimental protocols for eggs and hatchlings: ensuring hatchlings are “naïve” g g

- eggs from nests or oxytocin incubated in natural protected area and removed in dark under tarp

- transport to a dark room in light proof containers

- after hatching (n = 2575), individuals marked by cohort # and assigned to a release bucket in the dark (red bulb)

Experimental release protocols (arenas ~ 90 m diameter)- Fall and Spring

NE

S

West Newton Field(90 x 280 m)

Release hatchlings at center of arena in light-proof bucket with 4 release holes facing N, E, S & W (remove in 45 min.)

WalkWalk fence

Record time, location, clutch i.d. of hatchlingsRecord time, location, clutch i.d. of hatchlings found in buckets or at the fence

Experimental protocols (analysis)N = 0

Fence locations at 16 points(+ fractions) converted to degrees E = 4W = 12degrees

Results analyzed and plotted S = 8esu s a a y ed a d p o edwith Oriana™ package for circular statistics 15

12.5107 5

0McCarthy WMA - 2002

Patterns of orientation in a i t f it ti ( t l

20

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015 1512.5 12.510 107.5 7.5

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Snapping turtles

variety of situations (natural and unnatural) were examined to infer environmental cues

20 2015 1510 10

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1512.510

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Blanding’s turtlesto infer environmental cues being used by hatchlings

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McCarthy WMABlanding’s and

Ma Blanding s and

Snapping turtles(2001 & 2002)

ars Dunes

2001 S w ale

2002 F la t

hes

NPond(175 m)

SPHBlanding’s turtleMcCarthy 2001 N

Pond (280 m)SPH (220 m)Snapping turtles

(95 m)

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McCarthy

LPH (175 m)

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pp gMcCarthy (2002)N = 82

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WATSON-WILLIAMS F-TESTS: F = 4.615,p = 0.033, df = 1, 224 280 m

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Non-native Pine RowRiparian Tree-line

WNF – Blanding’s, Snapping and Painted Turtles12.5

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Blanding’s turtles (Sun Compass) Hwy 84

Hatchlings

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Congdon, Pappas, Brecke. Fig. 4.

Snapping turtle (time of day)- day vs. evening releaseday vs. evening release

AM

PMPM

Random 28 non-random vs. 3 random (EB’s)All hatchling release dispersal patterns (n = 31)

(dispersals are species-specific) Geotaxis no evidence

Horizon Painted and Snapping turtles (light-open)

Horizon Blanding’s turtles(dark -closed)

Olfaction no evidence

Social facilitation (scent trailing) no evidence

Humidity no evidenceHumidity no evidence

Learning (encoding) Blanding’s (others not tested)

After nest dispersal – Recruitment habitatShallow water with minimal depth and current with vegetation structure for protection from predators, abiotic

t (fi t i t i ) d f f dextremes (first overwintering) and source of food

•Acquisition and management of species•Acquisition and management of species specific or common aquatic recruitment h bihabitat

20081938

marshes“reservoir aging”

marshesmarshes

Habitat Alteration (silviculture & agriculture)

Nesting Dunes

Fire Suppression & Soybean Field Nesting Dunes

Conservation and Management Issues

1) Identify altered habitats that may interfere with orientation and navigation of adults and hatchlings

C i i d di l f h t hli iConsequences: impaired dispersal of hatchlings increasesa) distance traveled, b) time on land, c) risks (predators, roads abiotic extremes and not finding aquaticroads, abiotic extremes and not finding aquatic recruitment habitat)

2) Research to determine whether head starting programs that do not allow hatchlings to move to water naturally,

b l l i i i d i i killsubsequently results in impaired navigation skills

Conservation MeasuresIdentify and protect component areas to promote increased y p p psurvivorship of embryos in nests and hatchlings during dispersal: a) major nesting areas b) potential refuges for the dispersing hatchlings c) aquatic recruitment areas

NESTING AREAS :NESTING AREAS : 1. remove invasives, overgrown woody plants and dense

pine standspine stands2. reduce the extent of agricultural fields and feed plots (for

game species) in typical turtle nesting areas and subsidize farmers who increase the years fields lie fallow

3. Use road signs to increase awareness of hatchlings i d d d d li it h hi hcrossing roads and reduce speed limits where high

densities of hatchlings occur

Weaver Dunes, MN (600 ha of duneterraces, juveniles abundant, Pop. > 5,000)

Valentine Refuge, NB.(29 000 ha of sand hills(29,000 ha of sand hills,juveniles abundant, Pop. ~100,000)

E. S. George Reserve, MI (565 h f ld fi ld d d(565 ha of old fields and woods,juveniles rare, Pop. ~ 250)

Hatchling Blanding’s turtles orient toward far dark horizons (Pappas et al. 2009). Hypothesis: Rare occurrence of juveniles and low population sizes in many forested areas (i.e. northeastern populations) are caused by reduced nesting areas and poor hatchling survivorship during dispersal from nests because dark horizons

d i d i l l d h l i f l dare predominant and not consistently related to the location of wetlands.

On the ESGR, nesting areas used by Blanding’s turtles are characteristically located where - 1) wetlands are seldom visible from nesting areaswhere 1) wetlands are seldom visible from nesting areas

2) near and / or dark horizons are abundant and in all directions

“There is no magic to it, - protect our habitats!”- protect our habitats!

Weaver Dunes - 1938

Marshes

Dunes

Weaver Bottoms

Weaver Dunes 2009

MarshesMarshes

DDunes

Weaver Bottoms

Road Mortalitymale bias- male bias

- population declines

- male bias

- population declines

Blanding’s Turtle Nesting Habitat

Pond, Marsh & Potholes,

Nesting Dune

Nesting distances – Weaver Dunes (Minnesota)

Nesting distances – E. S. George Reserve (Michigan)

1 0

1 5

2 0

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D i s t a n c e f r o m n e s t t o w e t l a n d ( m )0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0

02

2 5A ( 3 7 7 )

A comparison of body temperatures during dispersal of hatchling Blanding's turtles during experimental releases and from natural nests.

ampl

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Nesting behavior of females and hatchlings

nest dispersal patterns co e ol ednest dispersal patterns co-evolvedFemales:- morphology and physiology (body size, mobility, risk of predation, desiccation

rates)

- wetland habitat and availability of nesting areas

Hatchlings:Hatchlings:- morphology and physiology (body size, mobility, risk of predation, desiccation

rates, and ability to stay on land for extended periods (yolk reserves)rates, and ability to stay on land for extended periods (yolk reserves)

- emergence from nests in Fall or Spring

- distance from wetlands

- habitats types between nests and wetlands

- wetland type (marsh, lake, stream, river)

Snapping turtles (2007-08)

CS CORN REL 2. NAÏVE - RANDOM NOT SIG DIFF FROM EACH OTHER

CS CORN REL 2 NAÏVE RANDOM NOT SIG DIFF FROM EACH OTHER

DEG - NN0

DEG - DOT0

CS CORN REL 2. NAÏVE - RANDOM NOT SIG DIFF FROM EACH OTHER

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DEG N DEG A DEG PDEG - N

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EB CORN BY CATEGORY - BOTH EXP. ARE NON RANDOM, NAÏVE ARE RANDOM --- ALL CATEGORIES ARE DIFF

Impact of Nesting in Agriculture Fields(t rtles ith TSD)(turtles with TSD)

i d l i i ( l- Biased population sex ratios (can lower effective population sizes, lead to eggs being i f il d i i h i linfertile, and over time, increase the potential for population declines)

d i d d i- Increase or decrease in nest depredation- Altered orientation and nest dispersal

i h hli i l d l iimpacts hatchling survival and population recruitment

SoftshellsSnapping

S i S thMaps

Spiny - SmoothBlanding’s

Painted

Ouachita - Common - False