Michael L. Wolfe

Response of understory vegetation to variable tree mortality following a mountain pine beetle epidemic in lodgepole pine stands in northern Utah

We examined the response of understory vegetation beneath monotypic, even-aged stands of lodgepole pine to increasing tree mortality following an epidemic of mountain pine beetles. we hypothesized that understory biomass would increase continually as the tree canopy was reduced and competition with trees for light and soil moisture decreased, but that plant species diversity and heterogeneity would peak at intermediate levels of beetle-caused tree mortality. Mean understory biomass clipped from 50 1-m2 circular plots/stand was an order of magnitude greater (40 g m-2) in beetle-killed stands, with typical levels of overstory tree mortality (50–70%), than in unaffected stands (4 g m-2); and it increased exponentially with disturbance severity. Frequency of fruit occurrence was positively related to increasing tree mortality, but was highly variable. Understory plant species richness and, to lesser degrees indices of diversity that incorporate evenness, peaked in stands with moderate mortality. Measures of vegetation patchiness (the coefficient of variation in mean plot biomass and an index of habitat interspersion) also peaked in stands with intermediate levels of disturbance. The response of understory plant species diversity to increasing disturbance severity is consistent with the pattern predicted by the intermediate disturbance hypothesis. However, other explanations of this pattern are discussed. Although understory plant community richness was higher in beetle-killed stands than in unaffected stands, new species were not abundant and therefore did not contribute substantially to greater evenness in understory plant diversity.

Effects of Habitat Characteristics on Gadwall Nest Predation and Nest-Site Selection

We compared characteristics of successful gadwall (Anas strepera) nests and those destroyed by mammalian predators (i.e., striped skunks [Mephitis mephitis]). Lateral cover density, understory cover height, species richness, vegetative penetrability, and patch size were significant determinants of the fate of a nest. Nest success was also influenced by 3 nonvegetative variables: minimum distance to water, dike width, and nest initiation date. Predation rates on nests differed (P 1.0 m), dense biennial and perennial weeds such as thistle (Cirsium arvense), stinging nettle (Urtica dioica), and teasel (Dipsacus spp.), and lacked well-developed understory (ground vegetation). The proportional occurrences of habitats A, B, and C were 33, 42, and 25%, respectively. Beginning in late May, we located nests by flushing females with a slow moving truck and occasional bursts of the trucks horn. This procedure was effective because all nests occurred within 10 m of the dike road. Density of waterfowl nests on the study area was determined by a complete enumeration verified by intensive ground searches in each area. Data recorded for each nest included species, number of eggs, stage of development (Weller 1956), and habitat. Pin flags were placed perpendicular to each nest at the edge of the road. One hundred seventy artificial nests were placed at random distances perpendicular to the dike road at regular intervals along the dike. They consisted of 2 chicken eggs the size of gadwall eggs placed in a shallow, excavated bowl. The same procedures employed for natural nests were used for artificial nests. Because predation rates for natural nests This content downloaded from 157.55.39.186 on Tue, 12 Apr 2016 09:03:55 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 53(1):1989 HABITAT NEST PREDATION * Crabtree et al. 131

Cougar Exploitation Levels in Utah: Implications for Demographic Structure, Population Recovery, and Metapopulation Dynamics

Abstract Currently, 11 western states and 2 Canadian provinces use sport hunting as the primary mechanism for managing cougar (Puma concolor) populations. Yet the impacts of sustained harvest on cougar population dynamics and demographic structure are not well understood. We evaluated the effects of hunting on cougar populations by comparing the dynamics and demographic composition of 2 populations exposed to different levels of harvest. We monitored the cougar populations on Monroe Mountain in south-central Utah, USA, and in the Oquirrh Mountains of north-central Utah from 1996 to 2004. Over this interval the Monroe population was subjected to annual removals ranging from 17.6–51.5% (mean ± SE = 35.4 ± 4.3%) of the population, resulting in a >60% decline in cougar population density. Concurrently, the Oquirrh study area was closed to hunting and the population remained stationary. Mean age in the hunted population was lower than in the protected population (F = 9.0; df = 1, 60.3; P = 0.004), and in a pooled sample of all study animals, females were older than males (F = 13.8; df = 1, 60.3; P < 0.001). Females from the hunted population were significantly younger than those from the protected population (3.7 vs. 5.9 yr), whereas male ages did not differ between sites (3.1 vs. 3.4 yr), suggesting that male spatial requirements may put a lower limit on the area necessary to protect a subpopulation. Survival tracked trends in density on both sites. Levels of human-caused mortality were significantly different between sites (χ2 = 7.5; P = 0.006). Fecundity rates were highly variable in the protected population but appeared to track density trends with a 1-year lag on the hunted site. Results indicate that harvest exceeding 40% of the population, sustained for ≥4 years, can have significant impacts on cougar population dynamics and demographic composition. Patterns of recruitment resembled a source–sink population structure due in part to spatially variable management strategies. Based on these observations, the temporal scale of population recovery will most likely be a function of local harvest levels, the productivity of potential source populations, and the degree of landscape connectivity among demes. Under these conditions the metapopulation perspective holds promise for broad-scale management of this species.

Gene flow estimates in Utah's cougars imply management beyond Utah

We present results from a study of genetic variation in Utahs cougar population. Estimates were based on data for 50 animals at nine microsatellite loci with five individuals sampled for each of ten management units throughout Utah. Levels of variation were moderate (average genetic diversity across populations was estimated to be 0.4687 for all 50 individuals), and comparable with other large mammals. But this level of variation for the microsatellite loci translated into an inbreeding effective population size of only 571 animals, much lower than the current estimates of census sizes of around 2000-3000. A lack of differentiation among the sampled populations across Utah (average N e m = 6.2) indicates that gene flow occurs over a large area. Since cougars are capable of movement beyond the Utah state borders (and certainly across management units), a better understanding of migration rates and patterns of dispersal will be achieved by sampling a much larger geographic region incorporating much of the western USA. Successful management and conservation of this species will then require a far more integrated approach, involving agencies across a number of states, as opposed to current management practices involving individual units within states.

Evaluation of Cougar Population Estimators in Utah

Abstract Numerous techniques have been proposed to estimate or index cougar (Puma concolor) populations, but few have been applied simultaneously to populations with reliable estimates of population size. Between 1996 and 2003, we evaluated the relative efficacy and accuracy of multiple estimation and index techniques for populations at 2 locations in Utah, USA: Monroe Mountain and the Oquirrh Mountains. We used radiotagging followed by intensive monitoring and repeated capture efforts to approach a complete enumeration of the populations. We used these benchmarks to evaluate other population estimates (Lincoln–Petersen mark–recapture, helicopter-survey probability sampling, catch-per-unit-effort) and indices (scent-station visits, track counts, hunter harvest). Monitoring over 600 scent-station-nights using different attractants June–September in 1996 and 1997 yielded a single cougar visit. Summer track-based indices reflected a 54–69% reduction in population size on the Monroe site and a numerically stable population on the Oquirrhs, but relationships between indices and the benchmark population estimates varied among techniques. Aerial track surveys required sufficient fresh snowfall accumulations for adequate tracking coverage of a given unit, conditions that were met only once on one study site in each of 3 years. Population estimates derived from helicopter-survey probability sampling exceeded reference population estimates by 120–284%, and bootstrapped estimates of standard error encompassed 25–55% of the population estimates (e.g., 5.6 ± 1.4 cougars/100 km2). Despite poor performance in predicting cougar population sizes, track-based estimates may provide better indices for monitoring large changes in population trends (i.e., with low precision). However, we recommend using multiple indices after determination of a more rigorous initial population estimate for managing populations of conservation concern and when considering connectivity to determine potential refuge sites for regional management (e.g., management by zones).

Long-Distance Dispersal of a Female Cougar in a Basin and Range Landscape

Abstract We used Global Positioning System technology to document distance, movement path, vegetation, and elevations used by a dispersing subadult female cougar (Puma concolor) through the fragmented habitat of the Intermountain West, USA. Over the course of 1 year, female number 31 moved 357 linear km, but an actual distance of 1,341 km from the Oquirrh Mountains, Utah to the White River Plateau, Colorado, constituting the farthest dispersal yet documented for a female cougar. This cougar successfully negotiated 4 major rivers and one interstate highway while traversing portions of 3 states. Our data suggest that transient survival, and therefore total distance moved, may be enhanced when dispersal occurs during the snow-free season due to low hunting pressure and greater access to high elevation habitats. Long-distance movements by both sexes will be required for the recolonization of vacant habitats, and thus inter-state management may be warranted where state boundaries do not coincide with effective dispersal barriers.

Herbivorous mammals along a montane sere: Community structure and energetics

All common herbivorous mammals were censused along a successional gradient in northern Utah in order to assess some of the changes in ecosystem attributes predicted to occur by Odum (1969). Biomass (B) and energy flow [Production (P), Respiration (R), and P + R (e)] through each of nine species in each of four serai stages (montane meadow, Populus -dominated forest, Abies -dominated forest, and Picea -dominated forest) were estimated. Tests of eight predicted trends were supportive in five cases (P/R ratio, P/B ratio, B/e ratio, net community production, and species richness), inconsistent in two cases (total organic matter and species evenness/general diversity) and ambiguous in one (size of organism). Community stability, as measured by changes in average community biomass between years of relatively normal and extremely low precipitation, increased with ecosystem maturity. Individual species, however, fluctuated greatly in biomass between the 2 years. Our results are consistent with the hypothesis that mammals are determinants of successional patterns only insofar as they affect plant colonization. However, a continuum probably exists between completely passive species and those that strongly influence successional patterns in plant communities through their effects on plant recruitment and/or mortality. Changes in the plant community in turn affect the composition of the herbivorous mammal community.

Age Determination in Moose from Cemental Layers of Molar teeth

A method is described for age determination in moose (Alces alces) from growth layers in the cementum of molariform teeth. The technique was used to determine the ages of 140 moose over 1 year old from Isle Royale. The findings indicate that the method described provides a more reliable basis for age determination in the older age-groups than estimates of mandibular tooth wear. It also has a wide range of application because any molariform tooth may be used. Ecological investigations of moose require a precise technique for age determination. Estimates of age on the basis of the mandibular tooth-wear classes, established by Passmore et al. (1955), do not provide the necessary degree of accuracy in the older age-groups for studies of this nature. This paper describes a method for age determination in moose by growth layers in the cementum of molar teeth.

Climate and density-dependent drivers of recruitment in plains bison

Abstract In semiarid ecosystems ungulate densities can compound the effects of drought on forage availability, which can feed back to regulate reproduction and offspring recruitment. Climatic changes in the frequency and severity of drought could thus exacerbate these effects. Here, we use long-term data sets to examine the dual influences of population density, cohort, and climatic variation on recruitment in the Henry Mountains bison (Bison bison bison) population. We found that 1-year lagged annual precipitation had a positive effect on recruitment (&bgr;  =  0.032, SE  =  0.009) and population density had a negative effect (&bgr;  =  −0.0023, SE  =  0.0004), but did not detect cohort effects. Furthermore, the effect of population density seemed to be more severe in dry relative to wet conditions, indicating that competition for forage could be severe in drought conditions. These results could help managers gain insight into the effects of climate change on bison population dynamics, and help guide the management of bison abundance on rangelands shared with cattle.

Potential Impacts of Coyotes and Snowmobiles on Lynx Conservation in the Intermountain West

Abstract Researchers and managers have hypothesized that coyote (Canis latrans) incursions into deep snow areas, facilitated by packed trails created by snowmobiles, may negatively impact lynx (Lynx canadensis) populations through interference or exploitation competition. In response to this hypothesis, federal agencies have limited snowmobile use within potential lynx habitat. We used aerial track counts and ground tracking to compare coyote activity in deep snow areas with and without snowmobile trails on the Uinta Mountain Range of northeastern Utah, USA, and 3 comparable sites in the Intermountain West to test this hypothesis. Our analysis suggests that snowmobile trail presence is a good predictor of coyote activity in deep snow areas. Over 90% of coyote tracks observed in our study areas associated with a snowmobile trail were within 350 m of the trail. Snow depth and prey density estimates influenced whether a coyote returned to a snowmobile trail. Our results suggest that restrictions placed on snowmobiles in lynx conservation areas by land management agencies because of the potential impacts of coyotes may be appropriate.