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

Douglas J. Krause ,Kyler Abernathy,Michael E. Goebel ,Greg Marshall

doi:10.1186/s40317-015-0028-9

Abstract

Leopard seals are apex predators that can alter the community structure of Antarctic coastal ecosystems. Previous behavioral studies were limited to land-based, daytime observations of foraging leopard seals. Consequently, foraging tactics, social behaviors, and indirect ecosystem impacts are poorly understood. Here, we present the first analysis of animal-borne HD video footage for foraging leopard seals. Each CRITTERCAM was deployed with Fastloc GPS and time-depth recorder instruments providing fine-scale habitat context for observed foraging behavior. We analyzed seven deployments obtained in January and February of 2013 and 2014 from adult female leopard seals near mesopredator breeding colonies on Livingston Island, Antarctica. The average deployment length was 4.80 ± 2.45 (range 0.86–9.12) days, which covered a total of 16 foraging trips. Habitat use, along with 39 prey capture attempts, and 11 leopard seal social encounters were scored from 50.3 h of video data. We obtained 3,833 post-filter GPS positions, accurate to within 70 m, and the mean dive depth was 14.84 ± 8.98 m. Leopard seal foraging focused on four prey items: Antarctic fur seals, Antarctic fur seal pups, pygoscelid penguins, and demersal notothen fishes. Ambush tactics used only by a subset of leopard seals drove high capture success rates of fur seal pups. We identified novel prey-specific foraging tactics including stalking and flushing notothen fishes. Leopard seals have been described as generalist apex predators; however, video and movement data suggest that leopard seals employ specialized prey-specific hunting tactics. Although preliminary, our findings indicate that leopard seals can affect coastal ecosystems through pathways beyond direct predation, including intraspecific kleptoparasitism and facultative scavenging/food caching. Our results suggest that position-integrated video data will be vital in quantifying the ecological impact of this abundant and versatile apex predator.

Highlights

Leopard seals are apex predators that can alter the community structure of Antarctic coastal ecosystems
Despite variance between individual seals in the percent time they spent in each behavioral state (Additional file 4), leopard seals consistently spent most of their in-water time searching for prey (50.4 ± 26.9%) or immobile and resting (23.2 ± 21.1%, Fig. 2)
Feeding behavior was focused on four prey items: Antarctic fur seals, Antarctic fur seal pups, demersal notothen fishes, and Pygoscelid penguins (Fig. 3)

Summary

Introduction

Leopard seals are apex predators that can alter the community structure of Antarctic coastal ecosystems. Previous behavioral studies were limited to land-based, daytime observations of foraging leopard seals. The foraging behavior of apex predators can alter marine coastal ecosystems through direct and indirect pathways of predation [1,2,3]. Leopard seals (Hydrurga leptonyx) are large, abundant, top predators with a circum-Antarctic. Leopard seal research has largely focused on identifying top-down ecosystem effects through direct predation. Previous studies of leopard seal predation on fur seals [13, 17, 18] and penguins [8, 19,20,21,22] were informative, but limited to opportunistic, land-based, daytime observations. The preferred prey items, hunting tactics and success rates of leopard seals are poorly known

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Discussion

Conclusion