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

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 of 91 deaths attributed to CWD and 27 of 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 deer that died of starvation. 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 that 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 four 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.