“Host dispersal responses to resource supplementation determine pathogen spread in wildlife metapopulations”

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Daniel J. Becker, Celine E. Snedden, Sonia Altizer, and Richard J. Hall (Oct 2018)

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How does resource supplementation and infection affect infectious disease spread in wildlife metapopulations?

Easy meals alter animal movement and disease spread

American white ibis (Eudocimus albus), a waterbird that moves nomadically among wetlands to track optimal feeding conditions, now occupies urban parks for extended periods in response to human food provisioning, potentially leading to increases in transmission of pathogens such as enteric Salmonella.
(Credit: Richard Hall)

Urban parks, backyards, landfills, and agricultural fields provide wildlife with access to novel food sources. Food provided by humans in these locations can dramatically alter patterns of animal site fidelity and movement between habitats, with consequences for pathogen spread across the landscape. To better understand how the extent of food-subsidized habitat affects wildlife distributions and infection patterns, researchers at the University of Georgia developed a mathematical model that assumes that animal dispersal and the duration of site occupancy will depend on food availability and abundance at a given site as well as animal infection status.

The authors found that both wildlife distributions across the landscape, and pathogen infection prevalence, depend on how productive food-provisioned patches are relative to natural patches. If habitats with human-provided food are occupied for longer by animals and produce more dispersers (such as might occur if animals survive better and produce more offspring when food is abundant and reliable), then infection becomes more widespread as more of the landscape is provisioned. However, if habitats with human-provided food produce fewer dispersers (such as might occur if animals stop moving as much when abundant food is present), then infection prevalence declines as more sites become provisioned. Reducing opportunities for pathogen spread can in turn increase landscape-level occupancy by wildlife.

These results highlight that when wildlife are fed by humans, whether at landfills or through recreational wildlife feeding, this can alter the spread of pathogens across a landscape. To determine if food provisioning is beneficial or detrimental for wildlife abundance and health, future work is needed to examine how births, deaths, and movement behavior respond to human-provided resources. These results are especially applicable to highly mobile, nomadic, urban-feeding species such as flying foxes, white ibis (pictured), and many other birds and mammals.

The research was led by Daniel Becker, a recent PhD graduate from the University of Georgia, overseen by University of Georgia faculty Sonia Altizer and Richard Hall, and resulted from a summer undergraduate research project from recent UC Berkeley undergraduate Celine Snedden.


Abstract

Many wildlife species occupy landscapes that vary in the distribution, abundance, and quality of food resources. Increasingly, urbanized and agricultural habitats provide supplemental food resources that can have profound consequences for host distributions, movement patterns, and pathogen exposure. Understanding how host and pathogen dispersal across landscapes is affected by the spatial extent of food-supplemented habitats is therefore important for predicting the consequences for pathogen spread and impacts on host occupancy. Here we develop a generalizable metapopulation model to understand how the relative abundance of provisioned habitats across the landscape, and host dispersal responses to provisioning and infection, influence patch occupancy by hosts and their pathogens. We find that pathogen invasion and landscape-level infection prevalence are greatest when provisioning increases patch attractiveness and disperser production and when infection has minimal costs on dispersal success. Alternatively, if provisioning promotes site fidelity or reduces disperser production, increasing the fraction of food-supplemented habitats can reduce landscape-scale infection prevalence and minimize disease-induced declines in host occupancy. This work highlights the importance of considering how resources and infection jointly influence host dispersal for predicting how changing resource distributions influence the spread of infectious diseases.