Habitat selection and demography of bobcats (Lynx rufus) in Iowa

Date
2006-01-01
Authors
Koehler, Stephanie
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Ecology, Evolution, and Organismal Biology
Abstract

Since the mid-1900s, bobcats have been rare throughout the Corn Belt of the Midwest because of historic habitat loss and unregulated harvest. Recently, reports of bobcat occurrences have increased in Iowa, motivating study of the mechanisms enabling them to re-colonize this fragmented, agricultural landscape. I determined habitat selection of bobcats by radio-collaring 44 bobcats in south-central Iowa during 2003-2005. Annual home range size of males (56.36 km2) was larger than that of females (20.16 km2). Females used smaller home ranges during April-September (15.64 km2), as compared to October-March (26.30 km2). Similarly, core size of males (8.75 km2) was larger than that of females (2.26 km2), and females used smaller cores in the April-September (1.66 km2) as compared to October-March (3.09 km2). Compositional analysis along with standardized selection ratios illustrate that bobcats were selecting forest habitat about twice as frequently than any other habitat class, including grassland and CRP, at both landscape and within home-range scales. Predictive models indicated that home range and core area was smaller in landscapes where forest and grassland habitat was less fragmented. Predictive models indicated home range shape was more circular in landscapes with low forest patch density within the home range. I estimated demographic parameters from 265 bobcat carcasses and the live-captures. The proportion of females in the population was 0.46. Mean age was 1.29 years and the oldest bobcat was aged at 9 years. Bobcats [less than or equal to 2 years of age comprised 66% of the age distribution. Mean litter size as determined from placental scars ranged from 2.50-3.00. Pregnancy rates of adult females ranged from 0.76-1.00. Annual survival of 44 radio-collared bobcats was 0.82. Automobile collisions (33%) and incidental trapping (22%) were the 2 most common causes of death. Annual survival as calculated from the age distribution (0.56) was considerably lower than that estimated from the radio-collared bobcats. Population growth estimates determined from life table analysis indicated a rate of annual growth ranging from 1.13-1.52, depending on assumptions.

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