Entity

Time filter

Source Type

La Grande, OR, United States

Clark D.A.,Oregon State University | Johnson B.K.,401 Gekeler Lane | Jackson D.H.,192 N Umpqua Hwy
Northwest Science | Year: 2015

Cougar (Puma concolor) kittens are a substantial proportion of resident cougar populations and their survival has important implications for population dynamics of the species. To better understand effects of age and sex on cougar kitten survival, we estimated age specific (mo.) survival rates of cougar kittens (n = 72) radiocollared during three studies conducted in Oregon from 1989-2011. Cougar kittens were entered into the dataset based on age (mo.) at capture and fates were determined at monthly intervals. We analyzed survival in Program MARK using known-fate models of radiocollared individuals. We tested for effects of sex and linear, log-linear, and quadratic effects of age. Our best model indicated survival rates of cougar kittens were similar between sexes and increased in a linear manner with age. Annual survival estimates of cougar kittens were 0.66 (95% CI = 0.42-0.84). Our second ranked model was the null model, that indicated constant survival over time and between sexes with an annual survival rate of 0.78 (95% CI = 0.62-0.88). All other models in our candidate model set were not considered further because they ranked below the null model and contained non-informative parameters where the estimated effect broadly overlapped zero. Fates of littermates were dependent due to high levels of mortality at nursery sites which likely reduced the potential importance of sex on survival rates. We expect patterns of increased kitten survival with age and lack of differences between sexes to be consistent across the geographic range of cougars. © 2015 by the Northwest Scientific Association. All rights reserved. Source


Rearden S.N.,Oregon State University | Anthony R.G.,Oregon State University | Johnson B.K.,401 Gekeler Lane
Journal of Mammalogy | Year: 2011

We investigated the effects of predation risk on birth-site selection by Rocky Mountain elk (Cervus elaphus nelsoni) during summer in 2002-2004 in northeastern Oregon at macrohabitat (3rd-order selection) and microhabitat (4th-order selection) scales. This study describes vegetative characteristics of birth sites selected by female elk when young <4-5 days old used the hiding strategy and predation sites when most predation events occurred on young >5 days old that used the fleeing strategy. At the macrohabitat scale we observed no evidence that female elk were influenced by predation risk when selecting a birth site on the basis of variables measured in this study. Females chose birth sites with less overhead cover than random sites, suggesting that they might have been influenced more by forage availability than predation risk. At the microhabitat scale females selected birth sites that had more overhead canopy cover and greater visibility at ground level than paired random sites, which suggested that birth-site selection at this scale was influenced by predation risk. Together, these results suggested that female elk selected areas for parturition at the macrohabitat scale that likely had forage to meet high nutritional demands of lactation and at the microhabitat scale selected areas that provided visibility to detect predators and reduce the risk of predation. Predators, mainly cougars (Puma concolor), killed young in areas closer to vegetative edges at the macrohabitat scale and with more visibility at the microhabitat scale. These areas were likely conducive to cougar hunting where sight and cover from forest edges can be important for stalking calves that are traveling with their mothers and family groups. © 2011 American Society of Mammalogists. Source


Johnson B.K.,401 Gekeler Lane | Coe P.K.,401 Gekeler Lane | Green R.L.,118 NE Vandenberg Avenue
Journal of Wildlife Management | Year: 2013

Understanding the relative effects of the many factors that may influence recruitment of ungulates is fundamental to managing their populations. Over the last 4 decades, average recruitment in some populations of elk (Cervus elaphus) in Oregon, USA declined from >50 to <20 juveniles per 100 females, and several competing hypotheses address these declines. We developed a priori models and constructed covariates spanning 1977-2005 from hunter-killed elk, elk population estimates, cougar harvest, and weather statistics to evaluate abiotic, bottom-up, and top-down factors that may explain annual variation and long-term trends of pregnancy, juveniles-at-heel in late autumn, and recruitment of juvenile elk in spring. In models of pregnancy status, August precipitation, age, and cougar index had positive effects, whereas previous year (t - 1) winter severity or winter precipitation(t-1) and elk density had negative effects. In models of juvenile-at-heel in late autumn, August precipitation, August precipitation(t-1), cougar index × elk density(t-1), and age had positive effects, whereas cougar index, elk density(t-1), and winter precipitation(t-1) had negative effects. Juvenile recruitment was best explained by positive effects of August precipitation(t-1), lactation rate, and cougar index × elk density(t-1) and negative effects of cougar index and elk density(t-1). Winter severity, precipitation, and temperature were not significant in explaining variation in elk recruitment. Annual variation in pregnancy, juvenile-at-heel, and recruitment was most influenced by August precipitation, whereas long-term trends in recruitment were most influenced by cougar densities with relatively weak effects of elk density. These results provide insight into causes of year-to-year and long-term trends of elk recruitment and provide a basis for more rigorous evaluation of factors affecting recruitment of elk. Copyright © 2012 The Wildlife Society. Source


Warren M.J.,401 Gekeler Lane | Wallin D.O.,Western Washington University
Conservation Genetics | Year: 2016

Population structure, connectivity, and dispersal success of individuals can be challenging to demonstrate for solitary carnivores with low population densities. Though the cougar (Puma concolor) is widely distributed throughout North America and is capable of dispersing long distances, populations can be geographically structured and genetic isolation has been documented in some small populations. We described genetic structure and explored the relationship between landscape resistance and genetic variation in cougars in Washington and southern British Columbia using allele frequencies of 17 microsatellite loci for felids. We evaluated population structure of cougars using the Geneland clustering algorithm and spatial principal components analysis. We then used Circuitscape to estimate the landscape resistance between pairs of individuals based on rescaled GIS layers for forest canopy cover, elevation, human population density and highways. We quantified the effect of landscape resistance on genetic distance using multiple regression on distance matrices and boosted regression tree analysis. Cluster analysis identified four populations in the study area. Multiple regression on distance matrices and boosted regression tree models indicated that only forest canopy cover and geographic distance between individuals had an effect on genetic distance. The boundaries between genetic clusters largely corresponded with breaks in forest cover, showing agreement between population structure and genetic gradient analyses. Our data indicate that forest cover promotes gene flow for cougars in the Pacific Northwest, which provides insight managers can use to preserve or enhance genetic connectivity. © 2016 Springer Science+Business Media Dordrecht Source


Dick B.L.,Pacific Northwest Research Station | Findholt S.L.,401 Gekeler Lane | Johnson B.K.,401 Gekeler Lane
Wildlife Society Bulletin | Year: 2013

It is a challenge to use collars on male cervids because their neck size can increase substantially during the rut and also because of growth as the animal matures. We describe how to build a self-adjusting expandable collar for yearling or adult male Rocky Mountain elk (Cervus elaphus) to which very high frequency transmitters and global positioning system (GPS) units can be attached. We evaluated performance and durability of 35 expandable collars placed on male elk from 2009 through 2011 within the Starkey Experimental Forest and Range enclosure, Northeast Oregon, USA. Twenty-four (69%) collars remained on elk throughout our sampling period for GPS fixes from March or April to 1 November each year. Eight (23%) collars broke before 1 November and 3 (9%) collars were removed when males were harvested by hunters. Six of 8 collars that broke before 1 November came off during the rut. Mean date these collars broke was 19 September (SE=7.1 days, 95% CI=1 Sept. to 7 Oct.). Excluding 1 collar still being worn by a male elk and those collars either recovered when males were harvested by hunters (3) or removed from adult males on the winter feed ground (7), mean number of days collars stayed on was 279 (SE=25.5, 95% CI=225.8-331.3 days). No deaths or injuries were attributed to the collars. Because these collars can break, especially during the rut, we recommend sample sizes of males be increased ≥25% to compensate for collars that may come off during that period. Collars are not recommended for multi-year studies of male elk without substantial modifications to our design and further testing. © 2013 The Wildlife Society. Source

Discover hidden collaborations