No abstract

Range expansion and population increase by coyotes (Canis latrans), reduced hunting and trapping, and intensified agricultural practices in the Midwest have altered red fox (Vulpes vulpes) mortality, although relative impacts of these factors are unknown. We examined mortality causes and survival of red foxes in urban and rural agricultural areas of Illinois, using radio telemetry data from 335 foxes (Nov 1996 to May 2002). We used Akaike's Information Criterion to evaluate six survival models for foxes reflecting 1) environmental effects, 2) intrinsic effects, 3) temporal effects, 4) behavioral effects, 5) social effects, and 6) a global model. Environmental and intrinsic models of survival were optimal for adult foxes. Adult foxes with low (0‐20%) and high (80‐100%) percentages of row crops in their home ranges had higher survival than adults with moderate percentages (40‐70%). Heavier adults at capture also survived better. A global model (all covariates) was optimal for juvenile foxes. Higher juvenile survival associated with larger litters, lower body fat, and reduced dispersal time. Yearly survival ranged from 0.18 for rural male juveniles to 0.44 for rural female adults. Adult survival rates (0.35) were 11% higher than juvenile survival rates (0.24). Yearly survival varied for urban foxes due to cyclic outbreaks of sarcoptic mange (Sarcoptes scabei). Thus, summer survival (May‐Sep) of urban juveniles ranged from 0.10 (mange present) to 0.83 (no mange recorded). Mange was the most common (45% of all fatalities) source of mortality for urban foxes, followed by road kill (31%). We recorded only 4 mange fatalities (2%) for rural foxes. Rural foxes experienced low hunting mortality (7%) and equivalent road kill and coyote predation fatalities (40% each). Sources of mortality for midwestern foxes have dramatically changed since the 1970s when hunting was the major cause of mortality. Coyote predation has effectively replaced hunting mortality, and cyclic patterns of mange outbreaks in urban fox populations might indicate a dynamic source or sink relationship to surrounding rural fox populations. Absent mange, urban areas might provide refugia for red foxes where coyote populations persist at high densities in rural areas. Managers of sympatric urban and rural wildlife populations must understand survival dynamics influencing the population at the landscape level.

Historically, bobcats (Lynx rufus) were found throughout the Corn Belt region, but they nearly disappeared from this area due to habitat loss and unregulated harvest that occurred during the century after European settlement. Reports of bobcat occurrences have been increasing in Iowa, USA, and biologists would like to understand the mechanisms enabling bobcats to recolonize this fragmented agricultural landscape. We determined space use and habitat selection of bobcats by radiocollaring 68 bobcats in south‐central Iowa during 2003–2006. We triangulated 12,966 locations and recovered an additional 1,399 3‐dimensional locations from Global Positioning System collars. We used a fixed kernel estimator to calculate 95% utilization distributions (UDs) for home ranges and 50% UDs for cores. Annual home range area of males (x̄ = 58.6 km2, 95% CI = 49.2–69.9) was nearly 3 times that of females (x̄=19.9 km2, 95% CI = 17.0–23.3). Females used smaller home ranges during April‐September when they were suspected to have kittens with them (x̄ = 16.8 km2, 95% CI = 13.7–20.7), as compared to October‐March (x̄ = 24.1 km2, 95% CI = 19.0–30.7), whereas home ranges of males did not differ between seasons. Similarly, core area of males (x̄ = 7.7 km2, 95% CI = 6.2–9.6) was larger than that of females (x̄ = 2.3 km2, 95% CI = 1.9–2.7). Females used significantly smaller cores in April‐September (x̄ = 1.8 km2, 95% CI = 1.4–2.3) as compared to October‐March (x̄ = 2.8 km2, 95% CI = 2.2–3.7), whereas males did not. For both sexes, compositional analysis indicated that forest habitat was ranked higher than all other habitat classes at both the landscape and local scale. Standardized habitat selection ratios illustrate that female and male bobcats selected forest habitat about twice as frequently as any other habitat class, including grassland and Conservation Reserve Program land. Predictive models indicated that home range and core area was smaller in landscapes where perennial forest and grassland habitats were less fragmented. Predictive models indicated home ranges were more irregular in shape in landscapes where row crop patches were less aggregated within home ranges. Our results have practical implications for wildlife managers regarding expected bobcat habitat use and distribution as the species becomes more abundant in the agricultural landscape of the Midwest.

No abstract

With intensive farming, planting and harvest are the primary disturbance factors driving cover dynamics that influence wildlife communities. A top predator, coyotes ( Canis latrans Say, 1823) impact other wildlife when populations are high. Thus, knowledge of coyote demographics in agricultural habitat is critical to understanding ecosystem dynamics. We studied survival of 59 radio-collared coyotes (28 juveniles, 31 adults) from 1996 to 2001 in intensively farmed central Illinois. Logistic regression suggested that age and year were important covariates, but sex was not. Divergence in age-specific Kaplan–Meier survival functions occurred during fall harvest because of higher mortality among juveniles. Annual survival (30 April – 29 April) was 0.59 (95% CI = 0.47–0.71) for adults and 0.13 (0.06–0.20) for juveniles captured after June 1. Shooting (58% of mortality) was the principal cause of mortality, followed by road kills (24%) and other mortalities. Mortality of juveniles following agricultural harvest probably occurs because of inexperience, dispersal through unfamiliar territory, intense human activity, and catastrophic loss of agricultural cover. In contrast, we recorded no shootings of coyotes during the growing season when agricultural cover was highest (14 June – 29 September) despite a year-round open hunting season on coyotes in Illinois.