River otters in Prince William Sound and Kenai Fjords National Park:

Distribution, relative abundance, and minimum

population size

Merav Ben-David

University of Wyoming

Howard Golden

Alaska Department of Fish and Game

Michael Goldstein

US Forest Service

Ian Martin

National Park Service

Other Personnel: Jessica Boyd, University of Wyoming

David Crowley, Alaska Department of Fish and Game Heidi Hansen, University of Wyoming

Dan Logan, US Forest Service Kaithryn Ott, University of Wyoming

Aaron Poe, US Forest Service Todd Rinaldi, Alaska Department of Fish and Game

James Wendland, Alaska Department of Fish and Game

Financial and Logistical support: Alaska Department of Fish and Game

National Park Service - SWAN Oil Spill Recovery Institute – Prince William Sound Science Center

University of Wyoming US Forest Service

Why monitor river otters?

River otters are top fish predators in the nearshore environment

P = 0.16

25 32

Low sociality High sociality

-18

-17

-16

-15

-14

-13

-12

Under fur

Guard hair

d13C

P = 0.006

P = 0.26

P = 0.16

25 32

Pelagic

Intertidal

Adopted from Blundell et al.

(2002)

Otters can serve as sentinels for changes in the nearshore environment

Regime shift in the gulf of Alaska Adopted from Piatt and Anderson (1996)

River otters are sensitive to environmental pollution

Bleed session

Oil administered

capture June July Aug SeptI SeptII Oct NovI NovII Dec Jan FebI FebII

11.0

12.0

13.0

14.0

15.0

16.0

17.0

Control

Low

High

10 10.4 10.8 11.2 11.6 12 12.4 12.8 13.2 13.6 14 14.4 14.80

4

8

12

16

20

24

28

32

36

40

44

48

Ox

yg

en

co

ns

um

pti

on

(m

l O

2.k

g-1

.min

-1)

R2 = 0.4

Exercise

At rest VO2 = 61.10 - 2.01(Hb) Results in a 37.6% increase in

energetic cost of running in river otters with low hemoglobin levels

Ben-David et al. (2000)

11.2 11.5 11.8 12.1 12.4 12.7 13 13.3 13.6 13.9 14.2 14.5 14.8 15.1 15.4 15.7 16 16.3 16.6 16.9 17.2

0

50

100

150

200

250

300

350

400

450

Hemoglobin (g/dL)

Hemoglobin levels were positively related to post-release survival of captive (n = 15) river otters.

( ) represent missing animals; ( ) represent animals dying of starvation. (Proportional hazard regression P = 0.045)

Ben-David et al. (2002)

River otter link the marine and terrestrial ecosystems

How much nitrogen can otters transfer from sea to land?

If otter densities are 1 per 1.3 km of shoreline deposition at latrines can be as high as 160 g/m2/year

Atmospheric deposition in Alaska

= 0.01-0.3 g/m2/year

Ben-David et al. (in press)

a b Land

Nitrogen deposition at latrines in Herring Bay in g/m2/year at different latrines based on actual visitation rate determined

from radio-telemetry. (a) assuming group size of 4, (b) assuming group size of 7

Ben-David et al. (in press)

-3-113579

111315171921

-5-3-113579

1113151719

-5-3-113579

1113151719

-36 -32 -28 -24 -20 -16 -12

Elderberry

Spruce

Alder

Salmonberry

Grass

Devil’s club

Blue berry

Fern

Moss

d13C

d15N

d15N

d15N

Incorporation of marine derived nitrogen into terrestrial vegetation (n ranges between 4 and 12 samples per plant species; closed symbols represent plants growing on river otters latrine sites, open symbols plants growing at random sites)

Ben-David et al. (1998)

0

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50

60

70

80

90

100

Plant

% o

f sit

es

Differences in community composition of plants between river otter latrines (n = 12) and nonlatrines (n = 9)

Ben-David (unpublished data)

Differences in percent N in soil and soil respiration rate between river otter latrines (n = 5) and nonlatrines (n = 3)

Random Latrine

0

2

4

6

8

10

12

14

16

18

20

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Re

sp

ira

tio

n r

ate

(u

g C

-CO

2/g

*h

)

%N

Ben-David and Gulledge (unpublished data)

How to monitor river otters?

They are hard to observe and difficult to re-capture

Distribution and relative abundance: Latrine site surveys a. latrine density

b. fecal deposition rate c. habitat selection

Location Dates Length of shoreline (km)

Latrine density

Fecal deposition rate

Kenai Fjords NP

7/5-10/04 354 0.432 1.94

Prince William Sound

8/9-21/04 945 0.269 1.80

Distribution of river otter latrine sites in Kenai Fjords National Park as determined during a survey in July 2004

Distribution of river otter latrine sites in Prince William Sound as determined during a survey in August 2004

Are “latrine density” and “fecal deposition rate” accurate indices of river otter

abundance/density?

Identifying individuals from ‘DNA Fingerprints’ of

nuclear microsatellites in feces

LOCUS 1 LOCUS 2

Estimating population size with mark-recapture methods of individuals identified from feces: Latrine site surveys a. collect all fresh feces (< 12 hours old) on first visit (marking occasion) b. collect all fresh feces on second visit (re-capture occasion) c. preserve all feces in 100% ethanol and keep cool

Extracting and amplifying otter DNA from feces

• Samples are sieved to remove prey remains

• Excess EtOH evaporated

• Extracted using Qiagen

• Prescreened with 2 best primers (Lut701, RIO05)

• Samples that do not amplify after 3 PCRs are discarded

Location Number of fresh feces collected on

first occasion

Number of fresh feces collected on second occasion

Total Discarded

KEFJ 267 NA 267 166

PWS 302 263 565 377

Is this a low success rate?

Species Location Success rate

River otters KEFJ (AK) 38%

PWS (AK) 33%

Green River (WY) 34%

Eurasian otters Scotland (UK) 15%

Brown Bears Captive (WA) 20%

All studies 31%

Effects of diet on genotyping success

crayfish fish sucker carp anal jelly other

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

+PCRs

Samples discarded

Fe

ca

l S

am

ple

s

Diet composition

Hansen (2004); supported by a graduate fellowship from the Oil Spill Recovery Institute

overstory

120100806040200-20

SU

CC

ES

S

1.2

1.0

.8

.6

.4

.2

0.0

-.2

ASPECT

1086420

SU

CC

ES

S

1.2

1.0

.8

.6

.4

.2

0.0

-.2

VEGSLOP

706050403020100

SU

CC

ES

S1.2

1.0

.8

.6

.4

.2

0.0

-.2

Effects of habitat characteristics on genotyping success

None of 12 habitat variables could explain differences in genotyping success (logistic regression with successful sites coded as 1 and unsuccessful sites coded 0)

1271512219N =

DATE

10-JUL-0409-JUL-0408-JUL-0407-JUL-0406-JUL-0405-JUL-04

PE

RC

SU

CC

120

100

80

60

40

20

0

-20

35

1271512219N =

DATE

10-JUL-0409-JUL-0408-JUL-0407-JUL-0406-JUL-0405-JUL-04

NE

WC

OL

L

22

18

14

10

6

2

-2

71

70

37

1

43

No difference in the number of feces collected per day in Kenai Fjords National Park in July 2004 (ANOVA, P = 0.38)

Effects of environmental conditions on genotyping success

Significant reduction in genotyping success (percent success) per day in Kenai Fjords National Park in July 2004 (ANOVA, P = 0.009)

1012151016121213137616N =

DATE

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-04

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-04

PE

RS

UC

120

100

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0

-20

62

1012151016121213137616N =

DATE

21-AUG

-04

20-AUG

-04

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17-AUG

-04

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-04

NE

WC

OL

L

22

18

14

10

6

2

-2

138

141

139

130

131108

118

96

83

91

75

43

31

32

26

15

9

No difference in the number of feces collected per day in Prince William Sound in August 2004 (ANOVA, P = 0.86)

Effects of environmental conditions on genotyping success

No difference in genotyping success (percent success) per day in Prince William Sound in August 2004 (ANOVA, P = 0.25)

0

10

20

30

40

50

60

10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0

Average Daily Temperature

Pe

rce

nt

ge

no

typ

ing

su

cce

ss

PWS

Effects of environmental conditions on genotyping success

0

10

20

30

40

50

60

70

10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0

KEFJ

Pe

rce

nt

ge

no

typ

ing

su

cce

ss

Average Daily Temperature

No effect of temperature alone on genotyping success in Kenai Fjords National Park in July 2004 (Regression, P = 0.41)

No effect of temperature alone on genotyping success in Prince William Sound in August 2004 (Regression, P = 0.27)

0

5

10

15

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25

30

10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5

Temperature – Humidity Index

Nu

mb

er

of

sa

mp

les

su

cce

ssfu

lly g

en

oty

pe

d

Effects of environmental conditions on genotyping success

0

10

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70

10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5

Pe

rce

nt

ge

no

typ

ing

su

cce

ss

Temperature – Humidity Index

Reduction in genotyping success with increasing temperature humidity index in Kenai Fjords National Park in July 2004 (Linear regression)

R2 = 0. 40, P = 0.18

R2 = 0.66, P = 0.05

Observer bias? NO!

HH MBD KEO0

10

20

30

40

50

60

Ge

no

typ

ing

su

cce

ss

Observer

No difference in genotyping success of feces collected by different observers in Kenai Fjords National Park in July 2004 (ANOVA, P = 0.38)

Effects of intestinal parasites on genotyping success

Location Prevalence of parasites

Percent of genotyping success in infested feces

Percent of genotyping success in non-infested feces

KEFJ 36% 19.8% 49.1%

PWS 10% NA NA

Future work: 1. Determine diet composition to evaluate its effect on

genotyping success 2. Complete amplifications with all 9 hypervariable primers

to obtain individual fingerprints 3. Evaluate the need for double sampling (mark and re-

capture occasions) 4. Estimate otter population size and density in KEFJ and

PWS 5. Assess the relation between latrine density and fecal

deposition rate to otter density