Stanley H. Anderson

Influence of prerelease experience on reintroduced black-footed ferrets (Mustela nigripes)

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 eAcient. We assessed postrelease behaviors and survival of three groups of black-footed ferrets, each with diAerent prerelease experience. Eighteen ferret kits60 days of age were moved with their dams from cages to 80-m 2 outdoor pens with prairie dog burrows. These animals were compared to animals reared in standard cages (na 72), some of which were given experience killing prairie dogs (na 32). Ferrets were released onto white-tailed prairie dog (Cynomys leucurus) colonies in Wyoming, USA, in fall, 1992. Radio-tagged cage-reared ferrets made longer nightly moves and dispersed further from release sites than their pen-reared counterparts. The band return rate was 4-fold higher for pen-reared animals than for cage-reared animals during surveys conducted about 1 month after release. We recommend routine use of quasinatural outdoor pens for prerelease conditioning of black-footed ferrets. Published by Elsevier Science Ltd.

GREATER SAGE-GROUSE NESTING HABITAT SELECTION AND SUCCESS IN WYOMING

Abstract Nesting habitat degradation and its negative effect on nesting success might contribute to the recent population and distributional declines of greater sage-grouse (Centrocercus urophasianus) throughout North America. We used radiotelemetry to locate greater sage-grouse nests in 7 different areas of central and southwestern Wyoming between 1994 and 2002; we studied each area for 2 to 4 years. Using binary logistic regression, we compared microsite vegetal data collected at nests (n = 457) and random (n = 563) sites and successful (n = 211) and unsuccessful (n = 238) nests to test hypotheses concerning greater sage-grouse nesting habitat selection and vegetal conditions associated with nesting success. We used Akaikes Information Criterion (AICc) and model averaging to make inference about the weighted support for the importance of individual habitat variables through the comparison of sets of competing models. Selected nest sites were located in areas with increased total shrub canopy cover (relative importance [RI] = 1.00), residual grass cover (RI = 0.47), and residual grass height (RI = 0.77) compared to random sites. Successful nests had increased residual grass cover (RI = 0.43) and height (RI = 0.48) relative to unsuccessful nests. Additionally, annual nest success rates (i.e., above vs. below our studys average) were related to the preceding years spring (Apr–May; RI = 0.44) and winter–early spring (Jan–Jun) precipitation (RI = 0.32). Correct classification rates for weighted average models that we derived through the 3 comparisons were between 60 and 70%, suggesting the variables adequately differentiated between plot types. However, high model selection uncertainty (i.e., the total number of models included in the sets of AICc-selected models) suggested that nest site selection and nesting success may be influenced by factors not considered in the modeling process. Management strategies that protect dense sagebrush stands and enhance residual grass cover and height within those stands should be used to maintain nesting habitat and increase nesting success of greater sage-grouse.

SPATIAL DISTRIBUTION OF GREATER SAGE-GROUSE NESTS IN RELATIVELY CONTIGUOUS SAGEBRUSH HABITATS

Abstract Degradation of nesting habitat has been proposed as a factor contributing to Greater Sage-Grouse (Centrocercus urophasianus) population declines throughout North America. Delineating suitable nesting habitat across landscapes with relatively contiguous sagebrush cover is difficult but important to identify areas for protection. We used radio-telemetry to locate Greater Sage-Grouse nests in relatively contiguous sagebrush habitats in Wyoming to investigate the spatial arrangement of nests relative to lek and other nest locations. Nest distributions were spatially related to lek location within 3 and 5 km of a lek, and a 5-km buffer included 64% of the nests. There was no relationship between lek size and lek-to-nest distance, suggesting that accurate population trend evaluation might require lek surveys in addition to lek counts. Closest known lek-to-nest distance was greater for successfully hatched compared to destroyed nests, and closely spaced nests tended to experience lower success and have higher probabilities of both nests experiencing the same fate compared to isolated nests, suggesting that a mechanism of enhanced prey detection occurred at higher nest densities. A low probability that a given individuals consecutive-year nest spacing occurred randomly suggested nesting site-area fidelity. Although a grouped pattern of nests occurred within 5 km of a lek, the proportion of nesting females located farther than 5 km could be important for population viability. Managers should limit strategies that negatively influence nesting habitat regardless of lek locations, and preserve adequate amounts of unaltered nesting habitat within treatment boundaries to maintain nest dispersion and provide sites for philopatric individuals.

Does Repeated Human Intrusion Cause Cumulative Declines in Avian Richness and Abundance

Human intrusion, the mere presence of people in the environment, has be- come a dominant form of disturbance in many landscapes. Some forms of intrusion from recreationists and other groups occur repeatedly and can seriously alter avian reproduction, survival, and habitat use. Accordingly, repeated intrusion has the potential to cause impacts that accumulate through time and that are manifested as progressive declines in avian richness and abundance. From 1989 to 1993, we experimentally assessed whether or not temporally cumulative impacts occurred in Wyoming bird communities as a result of re- peated intrusion by solitary hikers; the intrusions lasted 1-2 h each week during 10 con- secutive weeks of each years breeding season. We tested a priori hypotheses about declines in overall richness and abundance, relative richness and abundance for sets of common and uncommon species, richness and abundance for six guilds, and separate abundances of four common species. Relative richness and abundance for the set of common species were the only metrics to exhibit significant declines between years during the 5-yr period. The declines in these variables, however, were not cumulative. At a statistical power level of 0.85, minimum detectable differences for many variables were small enough to have allowed easy detection of substantive declines, had any occurred. The yearly effects we detected for some richness and abundance variables may not have led to cumulative declines because individuals displaced one year may have been replaced in subsequent years, and some individuals each year may have habituated to or learned to tolerate the intrusions. For the avian communities and intrusion levels we studied, managers should focus on trying to preclude or ameliorate short-term impacts. Attempts to identify the types and intensities of intrusion that actually cause cumulative declines in richness and abundance should continue. Data about intrusions that do not generate cumulative declines, such as those presented here, are just as important as data about intrusions that do cause cumulative declines; managers need both to define the scope of intrusion disturbances that can lead to cumulative impacts in avian communities. Information about the cumulative effects of intrusion should be used by conservation biologists, wildlife managers, and land-use plan- ners to decide whether or how to control intrusion.

Juvenile survival and population regulation of the Jackson elk herd

Elk (Cerous elaphus nelsoni) that summer in Grand Teton National Park (GTNP) are part of the migratory Jackson Elk Herd. They are fed in winter on the National Elk Refuge (NER) and have been hunted in portions of GTNP since 1950 to control population size. However, the number of elk in the Jackson Elk Herd has grown from about 8,000 in 1984 to >16,000 in 1997. We captured and radiocollared 164 newborn calves during 1990-92 to quantify juvenile mortality and its role in regulating the Jackson Elk Herd. Elk captured in GTNP (5.9 elk/km 2 ) and on adjacent national forest lands of lower elk densities (2.4 elk/km 2 ) were radiomonitored through May 1994. Mortality of calves was similar during summer (15.2%), fall (15.3%), and winter (16.5%) 1990-92. Most deaths resulted from predation, hunting, and winter mortality associated with increased precipitation, duration of winter, and epizootic disease. Survival of calves supplementally fed in winter exceeded survival of calves not fed (P = 0.039). All but 1 of 16 deaths of elk ≥1 year old (n = 122) resulted from hunting. Early-born calves experienced higher winter survival (P = 0.02) than late-born calves. Annual calf survival (x = 0.579) was inversely related to birth date (P 0.47). Because much of the variation in juvenile survival was density independent, we recommend management that reduces the dependence of elk on supplemental feed and increases harvests of female elk.

The Effect of Suburban and Agricultural Development on the Activity Patterns of Coyotes (Canis latrans)

Abstract We compared the activity patterns of coyotes (Canis latrans) in a suburban/agricultural area to those in an adjacent undeveloped area in northwest Wyoming from August 1998 to August 1999. Activity patterns were recorded using variable-pulse radio-collars. Correlation of recorded activity and observed activity indicated differences in the sensitivity of the collars. The mean percent of active signals for coyotes in the suburban/agricultural area was significantly lower during diurnal periods and significantly higher during nocturnal periods than the mean percent of active signals in those periods for coyotes in the undeveloped area. No differences between the two areas were observed during crepuscular times. Environmental stimuli, such as human activity, increased the amplitude of the circadian rhythms of coyotes. This increase in amplitude is a result of increased nocturnal activity and decreased diurnal activity.

Bird Tolerance to Human Intrusion in Wyoming Montane Forests

Human intrusion can be a serious problem for birds because it can cause displacement, prevent access to resources, and reduce reproduction and survival. The factors that influence avian tolerance to intrusion are poorly understood. We studied passerine responses to intrusion in Wyoming montane forests during the breeding season by using two indices of intrusion tolerance: detectability period, the amount of time that a bird remains near its initial flush point; and approach distance, how close one can get to a bird before it flushes. A solitary observer experimentally approached focal individuals and recorded detectability period, approach distance, the seasonal and daily timing of intrusion, number of nearby conspecifics, number of nearby heterospecific individuals, and surrounding vegetation conditions. Using data from the literature, we also assessed influences of migratory status, body mass, conspicuousness, and height above the ground at which species are active during the breeding season. Detectability period was significantly shorter, indicating intrusion tolerance was lower, when fewer conspecifics were nearby. Approach distance was significantly longer, indicating tolerance was lower, for more-conspicuous species and for species that are active closer to the ground. Effects of other variables studied were not significant. These results demonstrate that social and biological factors can influence tolerance to intrusion. Intrusion-induced behaviors such as nest abandonment and decreased nest attentiveness have led to reduced reproduction and survival in species that are intolerant of intrusion. With knowledge of factors that influence tolerance, the risk of disturbing birds that are sensitive to intrusion could be reduced.

Interception of moving organisms: influences of patch shape, size, and orientation on community structure

Island biogeographers have predicted that in oceanic systems, oblong islands oriented perpendicular to the dispersal paths of organisms should intercept more species and individuals than (1) circular islands of the same size, and (2) oblong islands of equal area oriented parallel to the direction of travel. Landscape ecologists expect similar relations with habitat patches in a terrestrial matrix. Yet in neither situation is there adequate empirical information to permit conclusions about the prevalence of such effects. To test the hypothesis that intercept-related patch variables influence community structure on the landscape scale, we studied relations between the richness and abundance of cavity-nesting birds and patch shape, size, and orientation relative to a northerly migration path. The influences of other patch features on nest abundances were removed analytically. Multiple regression indicated that the mean and total number of nesting species, and nest abundances for migrants were significantly associated with patch orientation or a patch area x orientation interaction, but not patch shape. Nest abundances for permanent residents were not associated with patch shape or orientation, although area effects, possibly reflecting dispersal interception, were evident. These results are consistent with the hypothesis that stochastic interception of migrating or dispersing organisms influences patch community structure. In addition to richness and abundance effects apparent in this analysis, the sex ratio, age structure, growth rate, social structure, and genetic features of patch populations may also be influenced. The interception of moving organisms by patches may thus be a key factor influencing population and community persistence in reserves. If so, landscape structure could be manipulated to maximize the interception of dispersing or migrating organisms, or minimize it if the effects are undesirable.

Seasonal changes in Yuma clapper rail vocalization rate and habitat use

Yuma clapper rails (Rallus longirostris yumanensis) are protected under the Endangered Species Act, and 90% of the U.S. population occurs within 2 wetland complexes. Assessment of impacts on, and mitigation measures for, Yuma clapper rails are required by law, yet managers lack quantitative information on habitat requirements. Seasonal habitat requirements provide resource managers with the information necessary to assess effects of development and water use practices on Yuma clapper rails in the Southwest. Playback recordings are commonly used to survey rail populations, yet their accuracy has not been evaluated. Consequently, we examined survey techniques and seasonal habitat requirements of Yuma clapper rails during 1985-87 on the lower Colorado River in southwestern Arizona to provide the recovery team and resource managers with reliable population estimates and habitat requirements

Effects of human intrusion on song occurrence and singing consistency in subalpine birds

-In 1989, 1990, and 1991, we conducted experiments on 30 circular 1.0-ha sites to assess whether human intrusions during a 10-week period influenced the occurrence and consistency of primary song in breeding subalpine birds. Using only those weekly censuses during which a species was present at a site, we computed song occurrence as the percentage of censuses during which a species sang, and we calculated singing consistency as the maximum number of consecutive censuses during which a species sang. An intrusion bout involved one person who walked through a site for 1 or 2 h. We used a priori contrasts, involving habitat covariates when appropriate, to assess differences in song occurrence and singing consistency between control and intruded sites and between sites at which the inner 25% of the site was disturbed (S25) and those at which 100% of the site was disturbed (S100). Singing by a number of species did not appear to be influenced by intrusion. For several species, however, song occurrence and singing consistency were higher on control sites than on intruded sites, indicating intrusion reduced singing activity. Song occurrence was higher on S100 relative to S25 sites as well. This latter pattern may have emerged because all of the individuals using the S100 sites were able to observe us during repeated intrusions and discern that we were not predators, whereas most of the individuals using the S25 sites likely did not have this opportunity. Thus, some of the individuals using S25 sites may have reduced their singing to avoid detection by us. Because song is essential in territory defense, mate acquisition, and in other reproductive activities, levels of intrusion that alter normal singing behavior have the potential to lower the reproductive fitness of males that are sensitive to this form of disturbance. Received 16 October 1992, accepted 28 January 1993. PRIMARY SONG is loud and far-reaching, occurring most often during the early breeding season and less frequently while young are being raised (Welty and Baptista 1988:224). Two important functions linked to primary song in breeding males are territory defense and mate attraction (Krebs 1977, Eriksson and Wallin 1986, McDonald 1989). Indirect evidence for the territorial function includes observations that most singing occurs during periods of territory establishment and maintenance and is restricted to defended areas (Falls 1988, Welty and Baptista 1988:227, 252). In addition, males countersing with conspecific males on adjoining territories (Wasserman 1977a), and they can be induced to sing with auditory playbacks that 4 Present address: John E. Conner Museum, Texas A&M University-Kingsville, Box 2172, Station 1, Kingsville, Texas 78363, USA. 5 Present address: 1306 Fox Street, Bossier City, Louisiana 71112, USA. simulate territorial intrusion (Falls 1981, 1988). The territory-defense role has been demonstrated experimentally through the surgical muting of males (Peek 1972a, Smith 1979, McDonald 1989), the tranquilizing of males (Peek 1972b), and the use of recorded playbacks (Krebs 1977, Falls 1988). The mate-attraction function of song has been corroborated with observations that singing activity is higher in males before they pair with females than after pairing (Wasserman 1977b). Experimental removal of females from pairs caused significantly higher singing rates by associated males (Wasserman 1977b, Krebs et al. 1981, Cuthill and Hindmarsh 1985). Moreover, males that were surgically muted were unable to attract females (e.g. McDonald 1989), even when such males possessed territories in good habitat and unmated females were present in the area (Peek 1972a). Because singing is important in territory defense and mate attraction, human disturbance that alters singing behavior may influence a