File(s) under permanent embargo

Geographic variation in at-sea movements, habitat use and diving behaviour of female Cape fur seals

journal contribution
posted on 2020-09-10, 00:00 authored by J A Botha, S P Kirkman, John ArnouldJohn Arnould, A T Lombard, G J G Hofmeyr, M A Meÿer, P G H Kotze, P A Pistorius
Knowledge of animal foraging behaviour has implications for management and conservation. While Cape fur seals Arctocephalus pusillus pusillus comprise a major proportion of the southern African marine predator biomass, little is known about their at-sea movements. We investigated foraging distribution, habitat use and diving behaviour for 35 adult female Cape fur seals from 3 breeding colonies experiencing contrasting oceanographic regimes. Animals from Black Rocks, the smallest and eastern-most colony, undertook shorter foraging trips and utilised shallower waters over the shelf. In comparison, animals from the larger west coast colonies, at Kleinsee and False Bay, travelled further and utilised deeper shelf and shelf-slope waters. However, across colonies, females typically preferred depths of <500 m and slopes of <5°. Kleinsee and False Bay seals selected sea surface temperatures within the range typically preferred by pelagic prey species such as round herring, sardine and anchovy (14-19°C). Black Rocks individuals showed bimodal preferences for colder (16°C) and warmer waters (>22°C). Dive behaviour was similar between Kleinsee and False Bay individuals (unavailable from Black Rocks), with both pelagic and benthic foraging evident. Diel patterns were apparent at both sites, as dive depth and benthic diving increased significantly during daylight hours, likely reflecting vertical movements of prey species. We provide the first assessment of Cape fur seal movement behaviour for the South African component of the population. Observed geographic differences likely reflect the availability of suitable habitat but may also indicate differences in foraging strategies and density-dependent effects throughout the range of this species.

History

Journal

Marine ecology progress series

Volume

649

Pagination

201 - 218

Publisher

Inter-Research Science Center

Location

Halstenbek, Germany

ISSN

0171-8630

eISSN

1616-1599

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal