Examination of the interaction between age‐specific predation and chronic disease in the Greater Yellowstone Ecosystem

Brandell, Ellen E.; Cross, Paul C.; Smith, Douglas W.; Rogers, Will; Galloway, Nathan L.; MacNulty, Daniel R.; Stahler, Daniel R.; Treanor, John J.; Hudson, Peter J.

doi:10.1111/1365-2656.13661

Cited by 7 publications

(15 citation statements)

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“…Determining the relationship between predation and disease prevalence in prey species has the potential to inform monitoring and management of both predators and prey. For example, monitoring of the ratio of adult to juvenile predator mortality could be indicative of disease burdens in the population (Brandell et al, n.d.). An increase in predation rates of adults likely indicates a change in their vulnerability, potentially due to disease.…”

Section: Figurementioning

confidence: 99%

“…The GYE has a diverse predator population, is well studied providing empirical parameters for the model, and had CWD emerge in 2018 (Krumm et al, 2010; Miller et al, 2008; Smith et al, 2020). In this system, the novel model was used to determine the effect of predation by wolves and cougars on CWD prevalence in elk and deer given variation in both disease prevalence and predation with age (Brandell et al, n.d.). Unsurprisingly, the model indicated that predator cleansing effects were greatest when predators selected upon the age class with the most infections.…”

Section: Figurementioning

confidence: 99%

“…The ability to model when predators have a role in reducing disease prevalence establishes a clear framework for future empirical studies in large mammal systems (Brandell et al, n.d.). Much of the understanding of the predator cleansing effect has stemmed from aquatic systems, where elegant experiments coupled with field studies have revealed complexities and a lack of consistent patterns across species (Duffy et al, 2005; Lopez & Duffy, 2021).…”

Section: Figurementioning

confidence: 99%

“…However, the role this plays on the predator cleansing effect was largely unknown. To investigate this, Brandell et al (2022) developed models to explore how prey selection and disease distribution across age classes will influence predator-driven reductions in prevalence of Chronic Wasting Disease (CWD). CWD is an always fatal prion disease spreading in deer and elk populations across North America.…”

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confidence: 99%

“…Thus, an increase in predator populations is something management agencies have the direct ability to influence. The model developed by Brandell et al (2022) indicates that increased kill rates, as a function of increased predator populations, reduces CWD prevalence; however, the authors caution that empirical data are needed as the model produces a range of results. Importantly, human tolerance for increased predators may be limited and disease reduction should only be considered among of suite of factors.…”

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confidence: 99%

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Modelling the role of predation on disease burdens of prey

Gagne

2022

Journal of Animal Ecology

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Predation can alter disease dynamics in prey. If predators select for infected individuals, they can reduce disease burdens. In other cases, predators can increase disease burdens via various mechanisms such as altered prey behaviour. The influence of predation on disease dynamics is a result of interactions among various traits of the predators, prey and the pathogen itself. For example, pathogens tend to vary with age and predators typically select for certain age classes. Thus, the overlap between ages selected by predators and those infected will likely contribute to any effects of predation on reducing disease burdens. In this paper, Brandell et al. (2022) develop a model to evaluate the predator cleansing effect given age-based variation in pathogens and predation. The model was developed for Chronic Wasting Disease (CWD) infections in deer and elk facing predation by cougars and grey wolves in the Greater Yellowstone Ecosystem. The results indicatethat predators can reduce CWD outbreak size, especially if selecting for infected individuals. CWD is an always fatal disease and this work suggests that predators could reduce disease burdens in cervids. The model is also applicable to other systems and promises to further our understanding of the role of predation on disease in prey, as well as drive future empirical studies.

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Modelling the role of predation on disease burdens of prey

Gagne

2022

Journal of Animal Ecology

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Chronic wasting disease alters the movement behavior and habitat use of mule deer during clinical stages of infection

Barrile,

Cross,

Stewart

et al. 2024

Ecology and Evolution

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Integrating host movement and pathogen data is a central issue in wildlife disease ecology that will allow for a better understanding of disease transmission. We examined how adult female mule deer (Odocoileus hemionus) responded behaviorally to infection with chronic wasting disease (CWD). We compared movement and habitat use of CWD‐infected deer (n = 18) to those that succumbed to starvation (and were CWD‐negative by ELISA and IHC; n = 8) and others in which CWD was not detected (n = 111, including animals that survived the duration of the study) using GPS collar data from two distinct populations collared in central Wyoming, USA during 2018–2022. CWD and predation were the leading causes of mortality during our study (32/91 deaths attributed to CWD and 27/91 deaths attributed to predation). Deer infected with CWD moved slower and used lower elevation areas closer to rivers in the months preceding death compared with uninfected deer that did not succumb to starvation. Although CWD‐infected deer and those that died of starvation moved at similar speeds during the final months of life, CWD‐infected deer used areas closer to streams with less herbaceous biomass than starved deer. These behavioral differences may allow for the development of predictive models of disease status from movement data, which will be useful to supplement field and laboratory diagnostics or when mortalities cannot be quickly retrieved to assess cause‐specific mortality. Furthermore, identifying individuals who are sick before predation events could help to assess the extent to which disease mortality is compensatory with predation. Finally, infected animals began to slow down around 4 months prior to death from CWD. Our approach for detecting the timing of infection‐induced shifts in movement behavior may be useful in application to other disease systems to better understand the response of wildlife to infectious disease.

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Investigating tritrophic interactions using bioenergetic demographic models

Passoni,

Coulson,

Cagnacci

et al. 2023

Ecology

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A central debate in ecology has been the long running discussion on the role of apex predators in affecting the abundance and dynamics of their prey. In terrestrial systems, research has primarily relied on correlational approaches, due to the challenge of implementing robust experiments with replication and appropriate controls. A consequence of this is that we largely suffer from a lack of mechanistic understanding of the population dynamics of interacting species that can be surprisingly complex. Mechanistic models offer an opportunity to examine the causes and consequences of some of this complexity. We present a bioenergetic mechanistic model of a tritrophic system where the primary vegetation resource follows a seasonal growth function, and the herbivore and carnivore species are modelled using two integral projection models (IPMs) with body mass as the phenotypic trait. Within each IPM, the demographic functions are structured according to bioenergetic principles, describing how animals acquire and transform resources into body mass, energy reserves and breeding potential. We parameterise this model to reproduce the population dynamics of grass, elk and wolves in northern Yellowstone (USA), and investigate the impact of wolf reintroduction on the system. Our model generated predictions that closely matched the observed population sizes of elk and wolf in Yellowstone prior to and post wolf reintroduction. The introduction of wolves into our basal grass‐elk bioenergetic model resulted in a population of 99 wolves, and a reduction in elk numbers by 61% (from 14,948 to 5,823) at equilibrium. In turn, vegetation biomass increased by approximately 25% in the growing season and more than 3‐fold in the non‐growing season. The addition of wolves to the model caused the elk population to switch from being food‐limited to being predator‐limited, and had a stabilising effect on elk numbers across different years. Wolf predation also led to a shift in the phenotypic composition of the elk population, via a small increase in elk average body mass. Our model represents a novel approach to the study of predator‐prey interactions. Explicitly considering and linking bioenergetics, population demography and body mass phenotypes can provide novel insights into the mechanisms behind complex ecosystem processes.

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Examination of the interaction between age‐specific predation and chronic disease in the Greater Yellowstone Ecosystem

Cited by 7 publications

References 73 publications

Modelling the role of predation on disease burdens of prey

Modelling the role of predation on disease burdens of prey

Chronic wasting disease alters the movement behavior and habitat use of mule deer during clinical stages of infection

Investigating tritrophic interactions using bioenergetic demographic models

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