Study tracks movement and pathogen exposure in California donkeys
Bottom line
A new study in Animals maps how free-roaming female donkeys in southern California move across arid landscapes and asks whether animals that encounter each other more often are also more likely to carry two pathogens of veterinary interest: asinine herpesvirus 5, or AHV-5, and Streptococcus equi subsp. zooepidemicus, or SEZ. Using telemetry and disease testing from donkeys in Fort Irwin National Training Center and Death Valley National Park between 2020 and 2022, the researchers found that home ranges were larger in the cool, wet season than in the hot, dry season, though the difference was not statistically significant. Across seasons, donkeys selected flatter areas closer to water, with more herbaceous cover favored in the wet season and lower heat loads in the dry season. The study also found that dyads with higher encounter rates were not more likely to test positive for AHV-5 or SEZ. (mdpi.com)
Why it matters: For veterinary professionals, the paper adds field ecology to a disease conversation that has often centered on capture, transport, and clinical presentation. Earlier work in recently captured Death Valley donkeys detected AHV-5 and SEZ and noted that stress and commingling may raise the risk of latent infection flare-ups or respiratory disease. This new analysis suggests landscape use, season, elevation, slope, and proximity to water may be more informative than simple donkey-to-donkey encounter frequency when thinking about pathogen exposure in free-roaming populations. That matters for surveillance planning, biosecurity around gathers and holding, and conversations with land managers overseeing feral equids in the West. (mdpi.com)
What to watch: Watch for follow-up work that links movement data to clinical outcomes, broader pathogen panels, or management decisions in California desert donkey populations. (mdpi.com)
A newly published Animals study offers a closer look at how free-roaming donkeys in southern California use desert habitat and how that movement may, or may not, relate to pathogen exposure. The researchers tracked female donkeys in Fort Irwin National Training Center and Death Valley National Park from 2020 to 2022 and paired GPS collar data with nasal swab testing for AHV-5 and SEZ. Their headline finding: donkeys predictably clustered around key resources such as water and flatter terrain, but higher encounter rates between pairs of animals did not correspond with higher odds of testing positive for either pathogen. (mdpi.com)
The paper builds on a growing body of work around free-roaming equids in the western U.S., especially research led by some of the same investigators. A 2024 PLOS One paper from this group supported the use of telemetry collars in free-roaming horses and burros, finding no consequential physical effects in 89% of burro observations and concluding that, with monitoring and remote-release mechanisms, collars can be a practical way to study spatial ecology and behavior. That methodological foundation matters here, because this latest study depends on collar-derived movement data collected every four hours. (journals.plos.org)
The newly released USGS data package adds useful operational detail. According to USGS, the study dataset includes GPS locations and disease-status data from donkeys in the two California sites, with testing performed at UC Davis using nasal swabs collected when animals were collared. Handling was carried out by trained staff from Peaceful Valley Donkey Rescue under capture contracts with Fort Irwin and Death Valley, and the work was conducted under institutional animal care approvals. (usgs.gov)
On the ecology side, the Animals paper reports that mean home ranges were larger in the cool, wet season, November through March, at about 318 square kilometers, versus roughly 159 square kilometers in the hot, dry season, April through October, although that seasonal difference was not statistically significant. Donkeys selected flatter areas closer to water year-round, shifted toward greater herbaceous cover in the wet season, and used lower-heat-load areas in the dry season. The pathogen-specific habitat associations were more nuanced: SEZ-positive donkeys selected lower elevations in the wet season and areas closer to water in the dry season, while AHV-5-positive donkeys selected areas farther from water in the wet season and steeper slopes in the dry season. (mdpi.com)
That last point is especially interesting because it pushes against a simple contact-driven disease story. The study found no relationship between dyad encounter rate and pathogen presence for either AHV-5 or SEZ. In other words, being near another donkey more often did not, by itself, predict whether an animal tested positive. That suggests exposure dynamics in free-roaming donkeys may be shaped more by environmental conditions, resource concentration, latent infection biology, or unmeasured stressors than by straightforward proximity metrics alone. That is an inference from the study’s findings, rather than a direct conclusion stated by the authors, but it fits the pattern they report. (mdpi.com)
There’s relevant background for both pathogens. A 2020 Animals study of recently captured feral donkeys from Death Valley found AHV-5 and SEZ among the detected agents and noted that relocation stress and social commingling could increase the likelihood of outbreaks of latent infections. Broader equine infectious disease literature also treats SEZ as more than a benign commensal in every context; CDC has described severe zoonotic infections linked to close horse contact in humans, underscoring why the organism remains clinically and occupationally relevant even when carriage in equids may be asymptomatic. (mdpi.com)
Why it matters: For veterinarians, this study is less about immediate clinical practice change and more about sharpening risk context. Free-roaming donkeys are often discussed through the lens of population management, welfare, or environmental impact, but this paper adds a movement-and-exposure layer that could inform how veterinary teams think about pre-gather screening, transport biosecurity, quarantine design, and respiratory disease monitoring when feral animals enter closer contact with domestic equids or people. It also reinforces that positive pathogen detection in free-roaming populations does not automatically map onto simple transmission assumptions. Surveillance strategies may need to account for season, water access, terrain, and management events, not just animal density or observed social contact. (mdpi.com)
What to watch: The next step will be whether researchers can connect these movement patterns to clinical signs, longitudinal shedding, or management interventions, and whether agencies use the new USGS dataset and this paper to refine how, where, and when free-roaming donkey populations are monitored or gathered in California. (usgs.gov)