ArticlePublisher preview available

Environmental drivers of oceanic foraging site fidelity in central place foragers

May 2020
Marine Biology 167(6)

DOI:10.1007/s00227-020-03685-y

Authors:

Dahlia Foo

University of Tasmania

Mark A Hindell

University of Tasmania

Clive R McMahon

Sydney Institute of Marine Science

Simon D Goldsworthy

South Australian Research and Development Institute

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Finding food is crucial to the survival and reproductive success of individuals. Fidelity to previous proftable foraging sites may bring benefts to individuals as they can allocate more time to foraging rather than searching for prey. We studied how environmental conditions infuence when lactating long-nosed fur seals (Arctocephalus forsteri) adopt a risky (low fdelity) or conservative (high fdelity) foraging strategy at two intra-annual temporal scales when foraging in a highly variable oceanic environment. Core foraging areas (CFAs; n=534; 30×30 km cells) of consecutive foraging trips were obtained from geolocation tracks of 12 females from summer to winter in 2016 (n=5) and 2017 (n=7). We used the spatial variability (standard deviation) of CFAs between or among oceanic foraging trips as a proxy for individual foraging site fdelity (IFSF). Over the entire oceanic foraging period (n=12), IFSF in the latitudinal axis increased with stronger sea-surface temperature gradient (SSTgrad), but decreased with greater SSTgrad and sea-surface height gradient variability. Over a period of two consecutive oceanic foraging trips (n=66), IFSF decreased with greater SSTgrad variability in the earlier foraging trip. LNFS show evidence that they use IFSF as a strategy to potentially optimise food acquisition, and that this behaviour is infuenced by mesoscale oceanographic parameters.

Timeline of the types (oceanic or shelf) of foraging trips made by individual seals. Each observation only indicates the start of the foraging trip. The solid rectangle is an example of the entire oceanic foraging period. The dashed rectangle is an example of a pair of consecutive oceanic foraging trips

…

Examples of sequential foraging tracks (trip number above each plot) from an individual seal (#353). Core foraging cells (90th percentile of time spent in cell of each trip) are red and non-core foraging cells are opaque white. The red triangle represents the colony at Cape Gantheaume, Kangaroo Island. Tracks are overlaid onto a sea-surface height gradient (SSHgrad; units: change in m per 0.25 × 0.25° pixel) and b sea-surface temperature gradient (SSTgrad; units: change in °C per 0.25 × 0.25° pixel). Environmental values show the average values during the period of each foraging trip. High values of SSHgrad and SSTgrad represent areas of strong eddy and frontal activity, respectively. See SFig. 1. for additional examples

…

Effect plots of a SSTgrad SD, b SSTgrad, and c year on latitude SD; and d SSHgrad on longitude SD over the entire oceanic foraging period of individual seals. The solid black lines and dots represent the predicted effect. Shaded bands and error bars represent the 95% confidence intervals. Grey circles represent raw data points

…

Effect of SSTgrad_SD on distancefidelity (distance between mean core foraging areas of consecutive pairs of oceanic foraging trips). The solid black lines and dots represent the predicted effect. Shaded bands and error bars represent the 95% confidence intervals. Grey circles represent raw data points

…

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Vol.:(0123456789)

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Marine Biology (2020) 167:76

https://doi.org/10.1007/s00227-020-03685-y

ORIGINAL PAPER

Environmental drivers ofoceanic foraging site delity incentral place

foragers

DahliaFoo1 · MarkHindell1· CliveMcMahon2· SimonGoldsworthy3· FredBailleul3

Received: 10 September 2019 / Accepted: 27 March 2020 / Published online: 5 May 2020

Abstract

Finding food is crucial to the survival and reproductive success of individuals. Fidelity to previous proﬁtable foraging sites

may bring beneﬁts to individuals as they can allocate more time to foraging rather than searching for prey. We studied how

environmental conditions inﬂuence when lactating long-nosed fur seals (Arctocephalus forsteri) adopt a risky (low ﬁdelity)

or conservative (high ﬁdelity) foraging strategy at two intra-annual temporal scales when foraging in a highly variable oce-

anic environment. Core foraging areas (CFAs; n = 534; 30 × 30km cells) of consecutive foraging trips were obtained from

geolocation tracks of 12 females from summer to winter in 2016 (n = 5) and 2017 (n = 7). We used the spatial variability

(standard deviation) of CFAs between or among oceanic foraging trips as a proxy for individual foraging site ﬁdelity (IFSF).

Over the entire oceanic foraging period (n = 12), IFSF in the latitudinal axis increased with stronger sea-surface temperature

gradient (SSTgrad), but decreased with greater SSTgrad and sea-surface height gradient variability. Over a period of two

consecutive oceanic foraging trips (n = 66), IFSF decreased with greater SSTgrad variability in the earlier foraging trip. LNFS

show evidence that they use IFSF as a strategy to potentially optimise food acquisition, and that this behaviour is inﬂuenced

by mesoscale oceanographic parameters.

Introduction

The marine environment is highly dynamic with physical

parameters determining the spatial and temporal distribu-

tion of primary productivity, thereby resulting in patchily

distributed food resources. Marine predators, therefore, face

the challenge of locating the prey which their survival and

reproductive success depend on in this heterogeneous envi-

ronment (Oosthuizen etal. 2015). From an optimal foraging

perspective, there may be long-term breeding and survival

beneﬁts (Bradshaw etal. 2004) for animals which use prior

knowledge about where food is (i.e., predictable) and return

to the same foraging area, rather than randomly searching

for food (Call etal. 2008). Indeed, many marine species,

such as sea birds (Weimerskirch 2007), sharks (Espinoza

etal. 2011), whales (Yates etal. 2007), turtles (Tucker etal.

2014), and seals (Oksanen etal. 2014; Arthur etal. 2015;

Abrahms etal. 2018a), display individual foraging site ﬁdel-

ity. However, repeated use of the same foraging patch may

lead to prey depletion and/or the prey distribution and the

density may have changed over time, thereby resulting in site

ﬁdelity being a sub-optimal foraging strategy (Pichegru etal.

2010; McIntyre etal. 2017; McHuron etal. 2018). Thus,

this illustrates a trade-oﬀ between a conservative strategy

of sticking to what one already knows and another riskier

strategy of switching and searching for new and potentially

more proﬁtable foraging patches.

Income-breeding marine predators provisioning off-

spring (Houston etal. 2007), such as fur seals (Staniland and

Boyd 2003), sea lions (Womble etal. 2009), and seabirds

(Croll etal. 2006; Rayner etal. 2010), can be considered as

Responsible Editor: D.E. Crocker.

Reviewed by B. Abrahms and undisclosed experts.

Electronic supplementary material The online version of this

article (https ://doi.org/10.1007/s0022 7-020-03685 -y) contains

supplementary material, which is available to authorized users.

* Dahlia Foo

dahlia.foo@utas.edu.au

1 Institute forMarine andAntarctic Studies, University

ofTasmania, Hobart, TAS7004, Australia

2 Sydney Institute ofMarine Science, Mosman, NSW2088,

Australia

3 Aquatic Sciences Centre, South Australian

Research andDevelopment Institute, WestBeach,

SouthAustralia5024, Australia

Content courtesy of Springer Nature, terms of use apply. Rights reserved.

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