Measuring spatial predator-prey overlap to understand changing trophic interactions

Dr Gemma Carroll1, Dr Kirstin Holsman3, Dr Stephanie Brodie1,2, Dr James Thorson3, Dr Elliott Hazen2, Dr Steven Bograd2, Dr  Rebecca Selden4

1Universiy Of California Santa Cruz, Monterey, United States, 2NOAA Southwest Fisheries Science Center, Monterey, United States, 3NOAA Alaska Fisheries Science Center, Seattle, United States, 4Rutgers University, New Jersey, United States

Global environmental change is causing species distributions to shift at an accelerating rate. However, species are not shifting one at a time or in isolation. Understanding changes in spatial overlap between interacting species such as predators and their prey may give deeper insight into how species redistribution affects food web dynamics. A number of overlap metrics have been developed for application in an ecological context, that define the overlap between two populations based on concepts such as spatial co-occurrence, niche partitioning and encounter probability. Here we outline a suite of these metrics and illustrate their utility at describing various scenarios of changing predator and prey distributions. We show how different metrics may be useful for different applications, e.g. for inferring changes in encounter probability for ecosystem modelling, or for assessing important geographic regions of overlap for spatial conservation planning. We then illustrate their application to a case study of predator-prey dynamics in a community of ground fish in the Eastern Bering Sea, Alaska, over 36 years. By reviewing predator-prey overlap metrics and assessing their utility at describing direct predator-prey interactions, we hope to contribute to an improved understanding of how shifting species distributions may alter ecosystem dynamics.


Gemma’s primary research interest is in understanding the relationships between predators and their prey in dynamic and changing environments. She has studied predator-prey dynamics in diverse contexts, including using biologging technology to understand how a strengthening warm water current influences prey consumption by penguins. She is currently based in Monterey, California, investigating ways of measuring and understanding climate-induced changes in predator-prey overlap in commercially important species of fish in Alaska and California.

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