Scale-dependent foraging behaviour and habitat associations of two sympatric marine top predators

Matt I. D. Carter; Geert Aarts; Sophie M. J. M. Brasseur; Gordon D. Hastie; Simon E. W. Moss; Jacob Nabe-Nielsen; Jonas Teilmann; Dave Thompson; Paul M. Thompson; Cécile Vincent; Debbie J. F. Russell

doi:10.1007/s10980-025-02281-z

Scale-dependent foraging behaviour and habitat associations of two sympatric marine top predators

Matt I. D. Carter^*, Geert Aarts, Sophie M. J. M. Brasseur, Gordon D. Hastie, Simon E. W. Moss, Jacob Nabe-Nielsen, Jonas Teilmann, Dave Thompson, Paul M. Thompson, Cécile Vincent, Debbie J. F. Russell^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Context: Theoretical research has considered how animals should optimise foraging strategies to maximise fitness, adapting search scale to exploit different habitats and minimise competition. Empirical studies have described multi-scale area-restricted search (ARS) strategies for some species, but the physical and biological mechanisms underpinning such behaviour are rarely studied.
Objectives: Our objectives were to quantify the presence, prevalence, and habitat associations of scale-dependent foraging for two sympatric seal species, accounting for regional variation across the seascape.
Methods: We analyse a GPS telemetry dataset of 116 grey (Halichoerus grypus) and 325 harbour seals (Phoca vitulina) tracked throughout the North Sea. We test the existence of multi-scale ARS, comparing hidden Markov models (HMMs) with two ARS states against more conventional HMMs (one ARS state). We quantify regional variation and examine the scale-dependence of foraging habitat associations using post-hoc “use-encounter” models.
Results: Both species exhibited nested broad-scale and focussed ARS. Accounting for scale resulted in increases of up to 25% and 46% in inferred ARS for grey and harbour seals respectively. The prevalence and habitat associations of different ARS scales varied in a regional species-specific manner.
Conclusions: We demonstrate the first application of HMMs to capture multi-scale ARS from animal-borne tracking data. Overlooking scale-dependence may mask individual variation and underestimate ARS, with consequences for ecological understanding and conservation applications. We hypothesise that seals employ different search scales for different habitats, competition levels and/or prey types. We call for further research to elucidate the prevalence and ecological significance of this phenomenon in other aquatic predators.

Original language	English
Article number	21
Pages (from-to)	1-22
Number of pages	22
Journal	Landscape Ecology
Volume	41
Issue number	2
Early online date	27 Dec 2025
DOIs	https://doi.org/10.1007/s10980-025-02281-z
Publication status	Published - Feb 2026

Keywords

Area-restricted search (ARS)
Central-place forager
Habitat association model
Hidden Markov model (HMM)
Pinnipeds
Seascape ecology

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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1 Active
2 Finished

SMRU NERC NC NPG Round 2 2024-2029
Sparling, C. (PI) & Russell, D. J. (CoI)
NERC
1/04/24 → 31/03/29
Project: Standard
EcoSTAR: EcoSTAR: Ecosystem level importance of Structures as Artificial Reefs
Russell, D. J. (PI), Hammond, P. (CoI), Hastie, G. (CoI) & Smout, S. (CoI)
29/06/20 → 28/06/23
Project: Standard
NERC NC National Public Good 2018 - 2023: Sea Mammal Research Unit NC-NPG activities to fulfill NERC's statutory duties.
Sparling, C. (PI) & Hall, A. (CoI)
1/04/18 → 31/03/23
Project: Standard

Cite this

Carter, M. I. D., Aarts, G., Brasseur, S. M. J. M., Hastie, G. D., Moss, S. E. W., Nabe-Nielsen, J., Teilmann, J., Thompson, D., Thompson, P. M., Vincent, C., & Russell, D. J. F. (2026). Scale-dependent foraging behaviour and habitat associations of two sympatric marine top predators. Landscape Ecology, 41(2), 1-22. Article 21. https://doi.org/10.1007/s10980-025-02281-z

@article{dc3da864c14f48e5b935aaa669a6b8e0,

title = "Scale-dependent foraging behaviour and habitat associations of two sympatric marine top predators",

abstract = "Context: Theoretical research has considered how animals should optimise foraging strategies to maximise fitness, adapting search scale to exploit different habitats and minimise competition. Empirical studies have described multi-scale area-restricted search (ARS) strategies for some species, but the physical and biological mechanisms underpinning such behaviour are rarely studied. Objectives: Our objectives were to quantify the presence, prevalence, and habitat associations of scale-dependent foraging for two sympatric seal species, accounting for regional variation across the seascape. Methods: We analyse a GPS telemetry dataset of 116 grey (Halichoerus grypus) and 325 harbour seals (Phoca vitulina) tracked throughout the North Sea. We test the existence of multi-scale ARS, comparing hidden Markov models (HMMs) with two ARS states against more conventional HMMs (one ARS state). We quantify regional variation and examine the scale-dependence of foraging habitat associations using post-hoc “use-encounter” models. Results: Both species exhibited nested broad-scale and focussed ARS. Accounting for scale resulted in increases of up to 25\% and 46\% in inferred ARS for grey and harbour seals respectively. The prevalence and habitat associations of different ARS scales varied in a regional species-specific manner. Conclusions: We demonstrate the first application of HMMs to capture multi-scale ARS from animal-borne tracking data. Overlooking scale-dependence may mask individual variation and underestimate ARS, with consequences for ecological understanding and conservation applications. We hypothesise that seals employ different search scales for different habitats, competition levels and/or prey types. We call for further research to elucidate the prevalence and ecological significance of this phenomenon in other aquatic predators.",

keywords = "Area-restricted search (ARS), Central-place forager, Habitat association model, Hidden Markov model (HMM), Pinnipeds, Seascape ecology",

author = "Carter, \{Matt I. D.\} and Geert Aarts and Brasseur, \{Sophie M. J. M.\} and Hastie, \{Gordon D.\} and Moss, \{Simon E. W.\} and Jacob Nabe-Nielsen and Jonas Teilmann and Dave Thompson and Thompson, \{Paul M.\} and C{\'e}cile Vincent and Russell, \{Debbie J. F.\}",

note = "Funding: NERC (NE/T010614/1, NE/Y006194/1); Department for Energy Security and Net Zero; NERC (NE/R015007/1)",

year = "2026",

month = feb,

doi = "10.1007/s10980-025-02281-z",

language = "English",

volume = "41",

pages = "1--22",

journal = "Landscape Ecology",

issn = "0921-2973",

publisher = "Springer Science and Business Media B.V.",

number = "2",

}

TY - JOUR

T1 - Scale-dependent foraging behaviour and habitat associations of two sympatric marine top predators

AU - Carter, Matt I. D.

AU - Aarts, Geert

AU - Brasseur, Sophie M. J. M.

AU - Hastie, Gordon D.

AU - Moss, Simon E. W.

AU - Nabe-Nielsen, Jacob

AU - Teilmann, Jonas

AU - Thompson, Dave

AU - Thompson, Paul M.

AU - Vincent, Cécile

AU - Russell, Debbie J. F.

N1 - Funding: NERC (NE/T010614/1, NE/Y006194/1); Department for Energy Security and Net Zero; NERC (NE/R015007/1)

PY - 2026/2

Y1 - 2026/2

N2 - Context: Theoretical research has considered how animals should optimise foraging strategies to maximise fitness, adapting search scale to exploit different habitats and minimise competition. Empirical studies have described multi-scale area-restricted search (ARS) strategies for some species, but the physical and biological mechanisms underpinning such behaviour are rarely studied. Objectives: Our objectives were to quantify the presence, prevalence, and habitat associations of scale-dependent foraging for two sympatric seal species, accounting for regional variation across the seascape. Methods: We analyse a GPS telemetry dataset of 116 grey (Halichoerus grypus) and 325 harbour seals (Phoca vitulina) tracked throughout the North Sea. We test the existence of multi-scale ARS, comparing hidden Markov models (HMMs) with two ARS states against more conventional HMMs (one ARS state). We quantify regional variation and examine the scale-dependence of foraging habitat associations using post-hoc “use-encounter” models. Results: Both species exhibited nested broad-scale and focussed ARS. Accounting for scale resulted in increases of up to 25% and 46% in inferred ARS for grey and harbour seals respectively. The prevalence and habitat associations of different ARS scales varied in a regional species-specific manner. Conclusions: We demonstrate the first application of HMMs to capture multi-scale ARS from animal-borne tracking data. Overlooking scale-dependence may mask individual variation and underestimate ARS, with consequences for ecological understanding and conservation applications. We hypothesise that seals employ different search scales for different habitats, competition levels and/or prey types. We call for further research to elucidate the prevalence and ecological significance of this phenomenon in other aquatic predators.

AB - Context: Theoretical research has considered how animals should optimise foraging strategies to maximise fitness, adapting search scale to exploit different habitats and minimise competition. Empirical studies have described multi-scale area-restricted search (ARS) strategies for some species, but the physical and biological mechanisms underpinning such behaviour are rarely studied. Objectives: Our objectives were to quantify the presence, prevalence, and habitat associations of scale-dependent foraging for two sympatric seal species, accounting for regional variation across the seascape. Methods: We analyse a GPS telemetry dataset of 116 grey (Halichoerus grypus) and 325 harbour seals (Phoca vitulina) tracked throughout the North Sea. We test the existence of multi-scale ARS, comparing hidden Markov models (HMMs) with two ARS states against more conventional HMMs (one ARS state). We quantify regional variation and examine the scale-dependence of foraging habitat associations using post-hoc “use-encounter” models. Results: Both species exhibited nested broad-scale and focussed ARS. Accounting for scale resulted in increases of up to 25% and 46% in inferred ARS for grey and harbour seals respectively. The prevalence and habitat associations of different ARS scales varied in a regional species-specific manner. Conclusions: We demonstrate the first application of HMMs to capture multi-scale ARS from animal-borne tracking data. Overlooking scale-dependence may mask individual variation and underestimate ARS, with consequences for ecological understanding and conservation applications. We hypothesise that seals employ different search scales for different habitats, competition levels and/or prey types. We call for further research to elucidate the prevalence and ecological significance of this phenomenon in other aquatic predators.

KW - Area-restricted search (ARS)

KW - Central-place forager

KW - Habitat association model

KW - Hidden Markov model (HMM)

KW - Pinnipeds

KW - Seascape ecology

U2 - 10.1007/s10980-025-02281-z

DO - 10.1007/s10980-025-02281-z

M3 - Article

SN - 0921-2973

VL - 41

SP - 1

EP - 22

JO - Landscape Ecology

JF - Landscape Ecology

IS - 2

M1 - 21

ER -

Scale-dependent foraging behaviour and habitat associations of two sympatric marine top predators

Abstract

Keywords

UN SDGs

Access to Document

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Projects

SMRU NERC NC NPG Round 2 2024-2029

EcoSTAR: EcoSTAR: Ecosystem level importance of Structures as Artificial Reefs

NERC NC National Public Good 2018 - 2023: Sea Mammal Research Unit NC-NPG activities to fulfill NERC's statutory duties.

Cite this