Huang, Y.-H., H. Joel, M. Küsters, Z. Barandongo, C.C. Cloete, W.M. Getz, A. Hartmann, P.L. Kamath, J.W. Kilian, J.K.E. Mfune, G. Shatumbu, R. Zidon, and W.C. Turner. 2021. Disease or drought: environmental fluctuations release zebra from a potential pathogen-triggered ecological trap. Proceedings of the Royal Society of London, B. Biological Sciences, 288: 20210582. https://doi.org/10.1098/rspb.2021.0582
Habitat selection that exposes hosts to areas of high disease risk can have an adverse effect on host populations. When a transmission hotspot for an environmentally persistent pathogen establishes in otherwise high-quality habitat, the disease may exert stronger impact on the host population, and potentially forms an ecological trap. However, fluctuating environmental conditions lead to heterogeneity in habitat quality and animal habitat preference, which may interrupt the overlap between selected and risky habitats. We evaluated spatiotemporal patterns in anthrax mortalities in a plains zebra (Equus quagga) population in Etosha National Park, Namibia, incorporating remote-sensing and host telemetry data. A higher proportion of anthrax mortalities was detected in open habitats than in other habitat types. Resource selection functions showed that the zebra population shifted habitat selection in response to changes in vegetation productivity and rainfall. Average to high rainfall years supported larger anthrax outbreaks, with animals congregating in preferred open habitats, while a severe drought forced animals into otherwise less preferred habitats, leading to few anthrax mortalities. Thus, the timing of anthrax outbreaks was congruent with preference for open plains habitats and a corresponding increase in pathogen exposure. Given shifts in habitat preference, the overlap in high-quality habitat and high-risk habitat is intermittent, reducing the adverse consequences for the population.