Graduate Thesis Or Dissertation
 

Short-tailed weasel space use in managed forests of western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/6395wb619

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  • Although short-tailed weasels (Mustela erminea) are important predators of small mammals, little is known about their space use, habitat selection, or vulnerability to predation in North America. To evaluate the effects of forest management and social structure on home range size and habitat selection of short-tailed weasels, I conducted a telemetry study in the Coast Ranges of western Oregon, USA. I used fixed kernel utilization distributions, multiple linear regression, and weighted compositional analysis to assess factors associated with home range size and habitat selection for 25 radio-marked short-tailed weasels. The radio-collared weasels selected early seral forest (5-15 years post-harvest) over closed canopy forest (>16 years postharvest). Females showed the strongest selection for early seral forest and had smaller home ranges than males (♀♀ x̄ = 10.4 hectares, 95% CI = 6.6-14.1 ha; ♂♂ x̄ = 53.3 hectares, 95% CI = 30.4-76.2 ha). Based on these observations, I proposed that weasels in my study exhibited a competitive hierarchy whereby the best exploitation competitors (females) selected the most productive cover types (early seral, fields) and appeared to be unaffected by interference competition from the larger males. Additionally, while radio-tracking weasels, I observed several mortalities, most of which I attributed to owls (4 out of 5 confirmed mortalities). Using Kaplan- Meier analysis, I estimated the estimated survival rate for the 9 month period of my study (June 2012-March 2013) was 0.36; 95% CI = 0.13-0.6. This estimate indicated an annual survival rate that was similar to the mean for 6 studies elsewhere in temperate North America in which the fate of weasels (Mustela spp.) was tracked (x̄ = 0.31 ± 0.09). I concluded that predation was an important factor limiting short-tailed weasel populations. Furthermore, strong selection for early seral cover, an ephemeral cover type, indicated that habitat for weasels in my study area may be limited to relatively short time periods. This may be due to forest management practices, including high density re-planting of conifers to accelerate the re-establishment of conifer trees after timber harvest. I suggest that reducing tree planting densities would favor weasel occupancy of managed forest by increasing the duration in which early seral vegetation is available.
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