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Wildlife managers in northwestern Colorado have had difficulty accurately estimating numbers of subadult male elk (Cervus elaphus) by sampling winter population densities and sex ratios. We investigated emigration and survival of telemetered 2-year-old male elk in a trophy hunting area in a northwestern Colorado Game Management Unit (GMU) to evaluate management strategies. We hypothesized that skewed numbers of males resulted from high subadult mortality or dispersal of subadult males. We used telemetered elk and Kaplan-Meier staggered entry methods to estimate emigration probability of 0.56 and 0.33 in 1995 and 1996, respectively. Maximum distances moved by emigrants from their capture point averaged 87 km (median...
We conducted a 2-year field experiment to determine whether archery and muzzleloading hunting seasons caused elk to move prematurely onto private land during late summer. The study site was divided into north and south areas, and each area received both an early- and late-opening treatment. Early-opening treatment was an archery season that opened 1 week earlier (23 Aug) than the historical opening, and late-opening treatment was an archery season that opened 2 weeks later (13 Sep), yielding a 21-day difference in opening dates. We relocated 80 radiocollared female elk, captured at random locations on summer ranges, approximately 2 times per week for a 3-month period surrounding early- and late-opening dates each...
Movement of Rocky Mountain elk (Cervus elaphus nelsoni) to private land in Colorado, USA, is problematic for population management because once on private land, elk are largely unavailable for harvest. We evaluated the relative effects of reducing hunter numbers and changes in opening dates of early-season hunting (archery) on elk movement to private land during a 4-year field experiment. Our study area was divided into north (NTA) and south (STA) treatment areas. Eighty adult female elk were captured and radiomarked during July 1996. From 1996 to 1999, we relocated radiomarked elk 2 times per week for a 2- to 3-month period surrounding archery season opening dates, and we classified each elk location as being on...
Age, sex, and body and reproductive condition of 631 burros (Equus asinus), and sex of 79 burro fetuses were determined from the Mohave Desert, California. The age distribution was skewed to young age classes in both sexes. Twelve individuals lived >10.5 years, and males lived longer than females. The postnatal sex ratio (61 M: 100 F) was skewed, whereas the prenatal sex ratio (68.1:100) did not differ significantly (P > 0.05) from parity. Males had better body condition than females. Poor female body condition was associated with costs of pregnancy and/or lactation. Females of reproductive age (≥1.5 years) had a 61.9% pregnancy rate and a 35.2% lactation rate. Sixty percent of lactating females were also pregnant,...
The southwestern willow flycatcher (SWFL; Empidonax traillii extimus) is an endangered songbird whose habitat has declined dramatically over the last century. Understanding habitat selection patterns and the ability to identify potential breeding areas for the SWFL is crucial to the management and conservation of this species. We developed a multiscaled model of SWFL breeding habitat with a Geographic Information System (GIS), survey data, GIS variables, and multiple logistic regressions. We obtained presence and absence survey data from a riverine ecosystem and a reservoir delta in south-central Arizona, USA, in 1999. We extracted the GIS variables from satellite imagery and digital elevation models to characterize...
Chukar partridges (Alectoris graeca) in separate groups were fed rations consisting of caryopses of downy brome (Bromus tectorum) and medusahead (Taeniatherum asperum), and commercial game farm pellets. The birds readily ingested the caryopses of both grasses. The caryopses of medusahead appeared to be largely indigestible. Severe weight losses occurred when birds were fed caryopses of either species. Birds fed downy brome appeared in better condition than those fed medusahead. Published in The Journal of Wildlife Management, volume 33, issue 4, on pages 975 - 978, in 1969.