Roads present formidable barriers to dispersal. We examine movements of two highly mobile carnivores across the Ventura Freeway near Los Angeles, one of the busiest highways in the United States. The two species, bobcats and coyotes, can disappear from habitats isolated and fragmented by roads, and their ability to disperse across the Ventura Freeway tests the limits of vertebrates to overcome anthropogenic obstacles. We combine radio-telemetry data and genetically based assignments to identify individuals that have crossed the freeway. Although the freeway is a significant barrier to dispersal, we find that carnivores can cross the freeway and that 5-32% of sampled carnivores crossed over a 7-year period. However, despite moderate levels of migration, populations on either side of the freeway are genetically differentiated, and coalescent modelling shows their genetic isolation is consistent with a migration fraction less than 0.5% per generation. These results imply that individuals that cross the freeway rarely reproduce. Highways and development impose artificial home range boundaries on territorial and reproductive individuals and hence decrease genetically effective migration. Further, territory pile-up at freeway boundaries may decrease reproductive opportunities for dispersing individuals that do manage to cross. Consequently, freeways are filters favouring dispersing individuals that add to the migration rate but little to gene flow. Our results demonstrate that freeways can restrict gene flow even in wide-ranging species and suggest that for territorial animals, migration levels across anthropogenic barriers need to be an order of magnitude larger than commonly assumed to counteract genetic differentiation.

Urbanization and habitat fragmentation are major threats to wildlife populations, especially mammalian carnivores. We studied the ecology and behavior of bobcats (   Lynx rufus ) and coyotes ( Canis latrans ) relative to development in a fragmented landscape in southern California from 1996 to 2000. We captured and radiocollared 50 bobcats and 86 coyotes, determined home ranges for 35 bobcats and 40 coyotes, and measured their exposure to development (  “urban association”  ) as the percentage of each home range composed of developed or modified areas. Both species occupied predominantly natural home ranges. Adult female bobcats had low levels of urban association, significantly lower than coyotes, adult male bobcats, and young female bobcats. Home‐range size was positively correlated with urban association for coyotes and adult male and young female bobcats, suggesting that human‐dominated areas were less suitable than natural areas in some important way. Animals more associated with non‐natural areas had higher levels of night activity, and both bobcats and coyotes were more likely to be in developed areas at night than during the day. Survival rates were relatively high and were not related to urban association, at least for animals>6–9 months of age. Mortality rates from human‐related causes such as vehicle collisions and incidental poisoning were also independent of urban association. In this region, even the few animals that had almost no human development within their home range were vulnerable to human‐related mortality. Carnivore conservation in urban landscapes must account for these mortality sources that influence the entire landscape, including reserves. For bobcats, preserving open space of sufficient quantity and quality for adult females is necessary for population viability. Educating local residents about carnivores is also critical for conserving populations in urban areas.

Humans introduce many toxicants into the environment, the long‐term and indirect effects of which are generally unknown. We investigated exposure to anticoagulant rodenticides and evaluated the association between notoedric mange, an ectoparasitic disease, and anticoagulant exposure in bobcats (Lynx rufus) and mountain lions (Puma concolor) in a fragmented urban landscape in southern California, USA. Beginning in 2002, an epizootic of notoedric mange, a disease previously reported only as isolated cases in wild felids, in 2 years reduced the annual survival rate of bobcats from 0.77 (5‐yr average) to 0.28. Anticoagulants were present in 35 of 39 (90%) bobcats we tested, multiple compounds were present in 27 of these 35 (77%), and total toxicant load was positively associated with the use of developed areas by radiocollared animals. Mange‐associated mortality in bobcats showed a strong association with anticoagulant exposure, as 19 of 19 (100%) bobcats that died with severe mange were also exposed to the toxicants, and for bobcats with anticoagulant residues >0.05 ppm, the association with mange was highly significant (X2 = 10.36, P = 0.001). We speculate that concomitant elevated levels of rodenticide exposure may have increased the susceptibility of bobcats to advanced mange disease. Bobcats were locally extirpated from some isolated habitat patches and have been slow to recover. In 2004, 2 adult mountain lions died directly from anticoagulant toxicity, and both animals also had infestations of notoedric mange, although not as advanced as in the emaciated bobcats that died with severe disease. Two other mountain lions that died in intraspecific fights also exhibited exposure to 2‐4 different anticoagulants. These results show that the effects of secondary poisoning on predators can be widespread, reach even the highest‐level carnivores, and have both direct and possibly indirect effects on mortality. Further research is needed to investigate the lethal and sub‐lethal effects of anticoagulants and other toxicants on wildlife in terrestrial environments.

Genetic parameters for Columbia, Polypay, Rambouillet, and Targhee sheep were estimated using REML with animal models for prolificacy, weight, and wool traits. All bivariate analyses included a covariance between additive genetic effects for the two traits plus appropriate additional covariances. Number of observations by breed ranged from 5,140 to 7,095 for prolificacy traits, from 7,750 to 9,530 for weight traits, and from 4,603 to 34,746 for wool traits. Heritability estimates ranged from .03 to .11 for prolificacy traits (litter size at birth and litter size at weaning), from .09 to .26 for weight traits (birth weight and average daily gain), and from .25 to .53 for wool traits (fleece weight, fleece grade and staple length). Estimates of direct genetic correlations among prolificacy and among weight

Predation by coyotes (Canis latram) on domestic sheep is a problem for many livestock producers throughout the United States Intermountain West. We examined whether surgical sterilization of coyote packs would modify their predatory behavior and reduce predation rates on domestic sheep as compared to coyote packs with pups. From June 1997 to December 1997, we gathered baseline information on coyote pack size and movements. In winter 1998, we surgically sterilized and radiocollared members of 5 coyote packs. We also captured and radiocollared members of 6 packs that remained intact (i.e., reproductive). During summer 1998, only 1 sterile pack killed a lamb, while 3 intact packs killed 11 lambs. When only sheepkilling packs were included, sterile packs killed an average of 0.35 lambs/week, while intact packs killed 1.53 lambs/week in 1998. Duringwinter 1999, we monitored 4 sterile and 8 intact packs. In summer 1999,3 sterile packs killed 3 lambs, while 4 intact packs killed 22 lambs. Considering only sheepkilling packs, sterile packs killed on average 0.38 lambs/week, while intact packs killed an average of 2.95 lambs/week in 1999. Coyotes were more likely to kill lambs that were on the edges of coyote territories as compared to core areas. Lambs of less than average weight were also more likely to be killed by coyotes. The available rodent biomass in each territory was not an influence on the differential kill rates exhibited between sterile and intact packs, nor did the amount of available alternate prey influence annual coyote predation rates on sheep. We conclude that we could use surgical sterilization to modlfy the predatory behavior of coyotes associated with pup production and provisioning of pups. Sterilization successfully reduced, but did not eliminate, coyote predation on domestic sheep. The amount of losses averted in the first year exceeded the costs associated with surgically sterilizing a coyote pack, which indicates that surgical sterilization could prove beneficial on small-scale livestock operations.