The foraging ecology, diet, and mass estimation of an apex predator, the leopard seal (Hydrurga ...

217 Pages·2016·5.79 MB·English

by  Douglas Krause

UC San Diego
UC San Diego Electronic Theses and Dissertations
Title
The foraging ecology, diet, and mass estimation of an apex predator, the leopard seal
(Hydrurga leptonyx), at Livingston Island, Antarctic Peninsula
Permalink
https://escholarship.org/uc/item/7mp1s7bw
Author
Krause, Douglas
Publication Date
2016
Supplemental Material
https://escholarship.org/uc/item/7mp1s7bw#supplemental

Peer reviewed|Thesis/dissertation
eScholarship.org Powered by the California Digital Library
University of California
UNIVERSITY OF CALIFORNIA, SAN DIEGO

The foraging ecology, diet, and mass estimation of an apex predator, the leopard seal
(Hydrurga leptonyx), at Livingston Island, Antarctic Peninsula.

A dissertation submitted in partial satisfaction of the requirements for the degree Doctor
of Philosophy

in

Oceanography

by

Douglas John Krause

Committee in charge:

Lisa Ballance, Co-Chair
Paul Dayton, Co-Chair
Michael Goebel
Ryan Kastner
Carolyn Kurle
Paul Ponganis
George Watters

2016
Copyright

Douglas John Krause, 2016

All rights reserved
The Dissertation of Douglas John Krause is approved, and it is acceptable

in quality and form for publication on microfilm and electronically:

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________

_____________________________________________________________________
Co-Chair

_____________________________________________________________________
Co-Chair

University of California, San Diego

2016

iii
DEDICATION

To the two most brilliant women I have ever met: My mother, Joan, who stirred a lifelong
passion by encouraging me to investigate the curious patterns we found in nature. And,
my wife Rachel whose love, patience, and encouragement made this work possible.
That Oxford comma was for you.

iv
EPIGRAPH

“We defend the places that we love, we love the places that we understand, and we have
to experience these places, see them, feel them, touch them, smell them and then think
about them very holistically to understand them.

This has to be done in nature. It is the only way to develop the sense of place so
important to our sense of self and to our sense of stewardship of our environment.”

Paul K. Dayton

v
TABLE OF CONTENTS

Signature Page ................................................................................................................... iii
Dedication .......................................................................................................................... iv
Epigraph ...............................................................................................................................v
Table of Contents ............................................................................................................... vi
List of Tables .................................................................................................................... vii
List of Figures .................................................................................................................... ix
List of Supplemental Files ................................................................................................ xii
Acknowledgements .......................................................................................................... xiii
Materials Published/Prepared for Publication in the Dissertation .................................. xvii
Vita ................................................................................................................................. xviii
Abstract of the Dissertation ...............................................................................................xx
INTRODUCTION ...............................................................................................................1

CHAPTER 1: Novel foraging strategies observed in a growing leopard seal
(Hydrurga leptonyx) population at Livingston Island, Antarctic
Peninsula. ...................................................................................................14

CHAPTER 2: Summer diving and haul-out behavior of leopard seals (Hydrurga
leptonyx) near mesopredator breeding colonies at Livingston
Island, Antarctic Peninsula ........................................................................59

CHAPTER 3: The diet of leopard seals (Hydrurga leptonyx) at Cape Shirreff,
Antarctic Peninsula examined with scat and stable isotope analysis .......113

CHAPTER 4: An accurate and adaptable photogrammetric approach for
measuring the size, mass, and body condition of a large
pinniped using an unmanned aerial system .............................................154

CONCLUSION ................................................................................................................194
vi
LIST OF TABLES

Table 1-1: Deployment dates, lengths and the number of foraging trips are
are listed per individual ....................................................................................51

Table 1-2: Definitions based on a literature review of carnivore hunting tactics ............52

Table 2-1: Individual seal identification and summary deployment statistics for
time-depth records recovered from leopard seals between 2008 and
2014 (n=21) ...................................................................................................106

Table 2-2: Summary statistics and descriptions of the 4 dive types output from
k-means cluster analysis (n=38,338)..............................................................107

Table 3-1: Individual seal identification and summary foraging statistics for
leopard seals sampled for blood and scat in 2013 and 2014 at Cape
Shirreff (n=19) ...............................................................................................144

Table 3-2: Carbon to nitrogen ratios and relative isotope values for all prey
samples by year and group ............................................................................145

Table 3-3: Carbon to nitrogen ratios and relative isotope values for leopard seal
tissues by year and capture ...........................................................................147

Table 3-4: Estimated proportions of leopard seal diets for 2013 and 2014 based
on scat and visual observation data ...............................................................147

Table 3-5: Results of K nearest-neighbors randomization tests of proximity in
isospace for all prey source groups from 2013 .............................................148

Table 3-6: Means, SDs and 95% credible intervals (CI) of mixing model posterior
distributions for the four sources ..................................................................148

Table 4-1: A summary of pinniped mass estimation studies .........................................185

Table 4-2: Photogrammetric (P) and manual (M) measurements used in
regression models ..........................................................................................186

vii
Table 4-3: % Error, ANOVA, and Tukey’s HSD test results of PSL compared
to SL for each category of photographs ........................................................187

Table 4-4: Comparison table of regression models, and equations from two
previous studies .............................................................................................188

viii
LIST OF FIGURES
Figure 1-0: Scatology is a powerful, though potentially biased, technique for
investigating the diet of marine mammals. ...................................................18

Figure 1-1: A Map of the US-AMLR study area. The black star marks the location
of Cape Shirreff on Livingston Island near the Antarctic Peninsula .............52

Figure 1-2: Percent of total time per behavior, based on scored CRITTERCAM
video. “Low Light” refers to any video segment that was too dark,
or obscured to reliably identify behavior ........................................................53

Figure 1-3: Number of attempts and captures per target prey species. Adult
and juvenile Antarctic fur seals, “Adult FS” (N=3), Antarctic fur
seal pups, “FS pup” (N=17), demersal notothen fishes, “Demersal fish”
(N=14), and penguins (N=1) ..........................................................................54

Figure 1-4: Prey capture success rates by hunting tactic. Target prey were:
a) Antarctic fur seal pups and b) notothen fishes ..........................................55

Figure 1-5: Foraging locations and elongation distributions for 401Y and 397G ..........56

Figure 1-6: Re-visitation and duration behavior plots for 397G .....................................57

Figure 1-7: Fate of all prey interactions by species ........................................................58

Figure 2-1: Cape Shirreff, Livingston Island, Antarctica. The black star in the
right pane indicates the location of Cape Shirreff in the western
Antarctic Peninsula region .........................................................................108

Figure 2-2: (A) Empirical haul-out probability distributions for leopard seals
at Cape Shirreff. (B) A polynomial linear regression (solid line) with
y = haul out probability and dLAN = time (h) from local apparent
noon; 95% confidence intervals (dashed lines) ...........................................108

Figure 2-3: The mean proportion (with SD whiskers) of dives that were classified
into each dive type (1-4) for all dives in the cluster data set (n=38,338) ...109

ix