Time filter

Source Type

Roseburg North, OR, United States

Cook R.C.,National Council for Air and Stream Improvement Inc. | Cook J.G.,National Council for Air and Stream Improvement Inc. | Vales D.J.,Muckleshoot Indian Tribe | Johnson B.K.,401 Gekeler Lane | And 15 more authors.
Wildlife Monographs

Demographic data show many populations of Rocky Mountain (Cervus elaphus nelsoni) and Roosevelt (Cervus elaphus roosevelti) elk have been declining over the last few decades. Recent work suggests that forage quality and associated animal nutritional condition, particularly in late summer and early autumn, influence reproduction and survival in elk. Therefore, we estimated seasonal nutritional condition of 861 female elk in 2,114 capture events from 21 herds in Washington, Oregon, Wyoming, Colorado, and South Dakota from 1998 to 2007. We estimated ingesta-free body fat and body mass, and determined age, pregnancy status, and lactation status. We obtained estimates for most herds in both late winter-early spring (late Feb-early Apr) and in autumn (Nov-early Dec) to identify changes in nutritional condition of individuals across seasons. Body fat levels of lactating females in autumn were consistently lower than their non-lactating counterparts, and herd averages of lactating elk ranged from 5.5% to 12.4%. These levels were 30-75% of those documented for captive lactating elk fed high-quality diets during summer and autumn. Body fat levels were generally lowest in the coastal and inland northwest regions and highest along the west-slope of the northern Cascades. Adult females in most herds lost an average of 30.7 kg (range: 5-62 kg), or about 13% (range: 2.6-25%) of their autumn mass during winter, indicating nutritional deficiencies. However, we found no significant relationships between spring body fat or change in body fat over winter with winter weather, region, or herd, despite markedly different winter weather among herds and regions. Instead, body fat levels in spring were primarily a function of fat levels the previous autumn. Thinner females in autumn lost less body fat and body mass over winter than did fatter females, a compensatory response, but still ended the season with less body fat than the fatter elk. Body fat levels of lactating females in autumn varied among herds but were unrelated to their body fat levels the previous spring. Within herds, thinner females exhibited a compensatory response during summer and accrued more fat than their fatter counterparts over summer, resulting in similar body fat levels among lactating elk in autumn despite considerable differences in their fat levels the previous spring. Level of body fat achieved by lactating females in autumn varied 2-fold among herds, undoubtedly because of differences in summer nutrition. Thus, summer nutrition set limits to rates of body fat accrual of lactating females that in turn limited body condition across the annual cycle. Pregnancy rates of 2- to 14-year-old females ranged from 68% to 100% in coastal populations of Washington, 69% to 98% in Cascade populations of Washington and Oregon, 84% to 94% in inland northwestern populations of Washington and Oregon, and 78% to 93% in Rocky Mountain populations. We found evidence of late breeding, even in herds with comparatively high pregnancy rates. Mean body mass of calves (n = 242) in 3 populations was 75 kg, 81 kg, and 97 kg, representing 55-70% of potential mass for 6- to 8-month-old calves on high-quality diets. Mean mass of 11 yearling females caught in autumn was 162 kg, approximately 70% of potential for autumn, and pregnancy rate was 27%. Mean mass of 28 yearlings caught in spring was 163 kg and pregnancy rate was 34%. Our data suggest widespread occurrence of inadequate summer nutrition. Summer ranges of just 3 herds supported relatively high levels of autumn body fat (11-13% body fat) and pregnancy rates (>90%) even among females that successfully raised a calf year after year. Most other summer ranges supported relatively low autumn levels of body fat (5-9% body fat), and reproductive pauses were common (<80% pregnancy rates). Overall, our data failed to support 2 common assumptions: 1) summer and early autumn foraging conditions are typically satisfactory to prevent nutritional limitations to adult fat accretion, pregnancy rates, and calf and yearling growth; and 2) winter nutrition and winter weather are the principal limiting effects on elk productivity. Instead, a strong interaction existed among level of summer nutrition, lactation status, and probability of breeding that was little affected by winter conditions - adequacy of summer nutrition dictated reproductive performance of female elk and growth as well as growth and development of their offspring in the Northwest and Rocky Mountains. Our work signals the need for greater emphasis on summer habitats in land management planning on behalf of elk. © 2013 The Wildlife Society. Source

Jackson L.S.,192 North Umpqua Highway | Carr F.M.,192 North Umpqua Highway | Meyer D.H.,III
North American Journal of Fisheries Management

Abstract: Fifteen years of video census data from a fishway at Winchester Dam on the North Umpqua River, Oregon, were used to evaluate sampling designs to estimate abundance of spring- and fall-run Chinook Salmon Oncorhynchus tshawytscha, summer- and winter-run steelhead O. mykiss, Coho Salmon O. kisutch, and Pacific Lamprey Entosphenus tridentatus. Five probabilistic sampling designs were evaluated via simulation, with variation in the number of days and the number of hours within a day that were sampled over a 1-year period. For most species, stratified one-stage and two-stage cluster designs were more accurate at estimating abundance than simple random sampling designs. There was very little gain in accuracy beyond sampling 8 h per day for all species. The stratified two-stage cluster nonuniform probability design was more accurate than the stratified two-stage cluster uniform probability design at estimating the abundance of steelhead, spring Chinook Salmon, and Coho Salmon, whereas using uniform probabilities resulted in more accurate estimates of abundance for Pacific Lamprey and fall Chinook Salmon. Additionally, the stratified and nonuniform probability designs can be adjusted for high-priority species through allocation of the sample and assigning selection probabilities of secondary sampling units that optimize efficiency for those species. The consistency in patterns observed among species suggests that the results of this study can be applied to other systems where the abundance of multiple species is of interest. Received December 5, 2014; accepted March 28, 2015 © 2015, © American Fisheries Society. Source

Whitney L.W.,Oregon State University | Anthony R.G.,Oregon State University | Anthony R.G.,U.S. Fish and Wildlife Service | Jackson D.H.,192 North Umpqua Highway
Journal of Wildlife Management

We studied resource partitioning between sympatric populations of Columbian white-tailed (CWTD; Odocoileus virginianus leucurus) and black-tailed (BWTD) deer (O. odocoileus hemionus columbianus) in western Oregon to understand potential mechanisms of coexistence. We used horseback transects to describe spatial distributions, population overlap, and habitat use for both species, and we studied diets with microhistological analysis of fecal samples. Distribution patterns indicated that white-tailed and black-tailed deer maintained spatial separation during most seasons with spatial overlap ranging from 5%-40% seasonally. Coefficients of species association were negative, suggesting a pattern of mutual avoidance. White-tailed deer were more concentrated in the southern portions of the study area, which was characterized by lower elevations, more gradual slopes, and close proximity to streams. Black-tailed deer were more wide ranging and tended to occur in the northern portions of the study area, which had higher elevations and greater topographical variation. Habitat use of different vegetative assemblages was similar between white-tailed and black-tailed deer with overlap ranging from 89%-96% seasonally. White-tailed deer used nearly all habitats available on the study area except those associated with conifers. White-tailed deer used oak-hardwood savanna shrub, open grassland, oak-hardwood savanna, and riparian habitats the most. Black-tailed deer exhibited high use for open grassland and oak-hardwood savanna shrub habitats and lower use of all others. The 2 subspecies also exhibited strong seasonal similarities in diets with overlap ranging from 89% to 95%. White-tailed deer diets were dominated by forbs, shrubs, grasses, and other food sources (e.g., nuts and lichens). Columbian black-tailed deer diets were dominated mostly by forbs and other food sources. Seasonal diet diversity followed similar patterns for both species with the most diverse diets occurring in fall and the least diverse diets in spring. High overlap in habitat use and diets resulted in high trophic overlap (81-85%) between white-tailed and black-tailed deer; however, the low spatial overlap reduced the potential for exploitative competition but may have been indicative of inference competition between the species. Diverse habitat and forage opportunities were available on the study area due to heterogeneous landscape characteristics, which allowed ecological separation between white-tailed and black-tailed deer despite similarities in diets and habitat use. We make several recommendations for management of CWTD, a previously threatened species, based on the results of our study. © 2011 The Wildlife Society. Source

Immell D.,192 North Umpqua Highway | Jackson D.H.,192 North Umpqua Highway | Boulay M.C.,192 North Umpqua Highway
Western North American Naturalist

Knowledge of home-range size and subadult dispersal activity of American black bears (Ursus americanus) is essential for understanding the complexity of how bears interact within populations and the environment. During 1993-1998, we monitored 95 radio-collared black bears in the Cascade Range of western Oregon to estimate homerange sizes and dispersal movements. Composite fixed-kernel home ranges were calculated for 37 bears. Mean home-range size differed between genders (189.7 km2 for males and 33.6 km2 for females); however, there was no difference in mean home-range size between subadult and adult males or subadult and adult females. We monitored 40 subadult bears (29 M, 11 F) to detect dispersal activity. We did not detect any dispersal of subadult females. One subadult male dispersed as a 2 year old, one dispersed as a 3 year old, and one as a 4 year old. The greatest dispersal distance of any subadult was 34 km by a 2-year-old male. © 2014. Source

Discover hidden collaborations