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Floodplains are presumed to be important rearing habitat for the endangered razorback sucker (Xyrauchen texanus). To help recover this endemic Colorado River Basin species, the Upper Colorado River Endangered Fish Recovery Program implemented a floodplain acquisition and enhancement program. Levee removal was initiated in 1996 as one component of this floodplain restoration program. The goal of the Levee Removal Study was to evaluate the system responses to levee removal and make specific recommendations concerning the value of floodplain/river reconnecting for endangered species (specifically razorback sucker) recovery.
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Captive breeding is increasingly being used to create supplies of endangered animals for release into natural habitats, but rearing strategies vary and debates arise over which methods are most efficient. We assessed postrelease behaviors and survival of three groups of black-footed ferrets, each with different prerelease experience. Eighteen ferret kits ≤60 days of age were moved with their dams from cages to 80-m2 outdoor pens with prairie dog burrows. These animals were compared to animals reared in standard cages (n=72), some of which were given experience killing prairie dogs (n=32). Ferrets were released onto white-tailed prairie dog (Cynomys leucurus) colonies in Wyoming, USA, in fall, 1992. Radio-tagged...
We estimated survival rates of greater sage-grouse (Centrocercus urophasianus) in North Park, Colorado, USA, from band-recovery data of 6,021 birds banded during spring, 1973-1990, with recoveries through 1993. Average annual adult female survival ((S) over bar = 0.59, SE = 0.011) was greater than average adult male survival ((S) over bar = 0.37, SE = 0.007), and average subadult (<1 yr old at time of banding) female survival ((S) over bar = 0.77, SE = 0.030) was greater than average subadult male survival ((S) over bar = 0.63, SE = 0.034). Four weather covariates (spring and winter precipitation and temperature) did not contribute to predicting annual survival. Published in Journal of Wildlife Management, volume...
This report represents a river reach application of the reset concept to examine survival and growth of larval razorback sucker and bonytail in floodplains. The floodplain reset concept refers to eliminating residual fish populations from floodplains prior to their connection to the river during spring flood flows. Despite drought conditions, sufficient river flows allowed the evaluation of the reset concept to enhance larval razorback sucker Xyrauchen texanus and bonytail Gila elegans survival during 2003-2004. Species composition in study floodplains shifted from communities dominated by riverine species to to those preferring lentic conditions following recruitment within floodplains. The number, biomass, and...
Invasion by nonnative brook trout (Salvelinus fontinalis) often results in replacement of cutthroat trout (Oncorhynchus clarki) in the inland western United States, but the underlying mechanisms are not well understood. We conducted a four-year removal experiment to test for population-level mechanisms (i.e., changes in recruitment, survival, emigration, and immigration) promoting invasion success of brook trout and causing decline of native Colorado River cutthroat trout (O. c. pleuriticus). We chose 700–1200 m segments of four small mountain streams where brook trout had recently invaded cutthroat trout populations, two each at mid elevation (2500–2700 m) and high elevation (3150–3250 m), and annually removed...
Translocations of greater sage-grouse (Centrocercus urophasianus) have been attempted in 7 states and one Canadian province with very little success. To recover a small remnant population and test the efficacy of sage-grouse translocations, we captured and transported 137 adult female sage-grouse from 2 source populations to a release site in Strawberry Valley, Utah, USA, during March-April 2003-2005. The resident population of sage-grouse in Strawberry Valey was approximately 150 breeding birds prior to the release. We radiomarked each female and documented survival, movements, reproductive effort, flocking with resident grouse, and lek attendance. We used Program MARK to calculate annual survival of translocated...
Razorback sucker (Xyrauchen texanus) larvae from adults exposed to selenium at three sites near Grand Junction, Colorado, for 9 months were used in a 30-day waterborne and dietary selenium study. Selenium concentrations in water averaged <1.6 microg/L from 24-Road, 0.9 microg/L from Horsethief, 5.5 microg/L from Adobe Creek, and 10.7 microg/L from the North Pond. Selenium in dietary items averaged 2.7 microg/g in brine shrimp, 5.6 microg/g in zooplankton from Horsethief east wetland, 20 microg/g in zooplankton from Adobe Creek, and 39 microg/g in zooplankton from North Pond. The lowest survival occurred in larvae fed zooplankton rather than brine shrimp. Survival of larvae at Adobe Creek and North Pond was lower...
Tree loss is increasing rapidly due to drought- and heat-related mortality and intensifying fire activity. Consequently, the fate of many forests depends on the ability of juvenile trees to withstand heightened climate and disturbance anomalies. Extreme climatic events, such as droughts and heatwaves, are increasing in frequency and severity, and trees in mountainous regions must contend with these landscape-level climate episodes. Recent research focuses on how mortality of individual tree species may be driven by drought and heatwaves, but how juvenile mortality under these conditions would vary among species spanning an elevational gradient—given concurrent variation in climate, ecohydrology, and physiology–remains...
Multiple factors likely influence natal dispersal behavior of juvenile mammals, which is typically male-biased. Because of their small body size and specific habitat requirements, pygmy rabbits (Brachylagus idahoensis) are expected to exhibit limited dispersal. We predicted that dispersal would be male-biased, that juveniles born later in the year would disperse farther, and that juveniles would be more likely to disperse away from areas of higher habitat saturation. We used radiotelemetry to study dispersal of 61 juvenile pygmy rabbits (31 males and 30 females) from shortly after emergence from natal burrows (April?July) to the beginning of the next breeding season (mid-March) during 2004?2006. Juveniles dispersed...
Elevated selenium concentrations documented in water, sediment, and biota in irrigation drain water studies by U.S. Department of the Interior agencies and academia have raised concerns that selenium may be adversely affecting endangered fish in the upper Colorado River basin. The objective of the study was to determine the effects on endangered razorback sucker (Xyrauchen texanus) larvae from exposure to selenium and other trace elements in water and zooplankton collected from sites adjacent to the Colorado River near Grand Junction, CO. A 30-day study was initiated with 5-day-old larvae exposed in a 4�4 factor experiment with four food and four water treatments, and the biological endpoints measured were survival,...
Fisheries managers have often suggested that survival of trout during the winter is a major factor affecting population densities in many stream ecosystems in the Rocky Mountains. In Wyoming, trout population reductions from fall to spring in excess of 90% have been documented in some reservoir tailwaters. Though biologists have surmised that these reductions were the result of either mortality or emigration from some river sections, the specific mechanisms have not been defined and the factors leading to the trout loss are unknown. This is a review of four studies that were conducted or funded between 1991 and 1998 by the Wyoming Game and Fish Department to understand the extent of overwinter losses, identify some...
    map background search result map search result map Influence of prerelease experience on reintroduced black-footed ferrets (Mustela nigripes) Influence of prerelease experience on reintroduced black-footed ferrets (Mustela nigripes)