Open Collections

Majid, Sultana

University of British Columbia

In the Okanagan valley of British Columbia, California bighorn sheep (Ovis canadensis california) populations have been declining, while facing an infestation of Psoroptes ovis mites starting in 2011. These mites cause debilitating skin diseases, which potentially impact bighorn sheep’s hearing ability, impairing awareness, and increasing sheep vulnerability predators such as cougars (Felis concolor). Empirical work on carnivore-parasite interactions with a common prey/host is scarce for large mammals. My study addresses this gap by examining the population ecology of bighorn sheep exposed to infection by mites and predation by cougars. Understanding the proximate causes of sheep mortality in relation to diseased and non-diseased landscape is essential for conserving future populations. Infection is currently contained to the sheep subpopulation on the west side of the valley due to landscape barriers (i.e., highways, towns, and lakes), and the east bighorn sheep subpopulation remains uninfected to date, presenting a unique comparative study opportunity. I have compared the mortality, survivorship and body condition of 82 GPS-collared sheep (43 west infected; 39 east uninfected). Recruitment and population growth were also examined, between 2016 and 2018, in collaboration with the Government of British Columbia, Ministry of Forests, Lands, Natural Resource Operations and Rural Development (FLNRORD) wildlife biologists. Results indicated no significant difference in survival, cause-specific mortality, or body condition, best supporting the Compensatory Mortality Hypothesis, where regardless of P. ovis infection other mortality causes were offset leading to no decrease in sheep survival. No difference was found in recruitment and population growth from 2017 to 2018, further indicating mites were not significantly detrimental to sheep in recent years. Both subpopulations have a declining population growth of <1, suggesting underlying conditions may be more strongly influencing sheep populations than mite infestation (e.g., poor range condition, predation, undetected disease). For effective management and better understanding of Okanagan sheep ecology, it is recommend for wildlife managers: 1) conduct habitat selection and movement analyses; 2) perform more intensive surveillance and monitoring; 3) assess range condition; 4) understand the role of cougar predation; and 5) resolve mite mitigation and treatment options.

Text

2021-08-13

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/79289

Biology

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/