John W. Laundré

Numerical and Demographic Responses of Pumas to Changes in Prey Abundance: Testing Current Predictions

Abstract Information on factors affecting population size of pumas (Puma concolor) can be important because their principal prey over most of the western United States are valued big game species (e.g., mule deer [Odocoileus hemionus], elk [Cervus elaphus], and bighorn sheep [Ovis canadensis]). Based on the hypothesis that puma numbers are limited by their food supply, puma populations should track changes in prey abundance by growing exponentially with increases in prey and by declining with a lag response when prey decreases. Additional predictions proposed by researchers are that body mass of pumas, female productivity, kitten survival, and adult survival should decrease after a prey decline. We used a 15-year database from a hunted population of pumas in southern Idaho and northwestern Utah to test these predictions. During the 15-year time span of the database, a major decline in mule deer abundance occurred. Estimates of puma numbers and demographic characteristics came from intensive capture and radiocollaring efforts. We calculated kitten and adult survival with MICROMORT software. We found that adult puma numbers increased exponentially at r = 0.07 during a period of increasing mule deer numbers. Four years after the mule deer abundance declined, puma numbers decreased at a rate of r = −0.06. Body mass of female pumas was lower after the decline in puma numbers (42.6 ± SE = 1.2 kg, n = 40 vs. 40.1 ± 0.64 kg, n = 34, t = 5.06, P = 0.045). Kitten survival was less after the decline in deer abundance (0.573 ± 0.016, n = 30 vs. 0.856 ± 0.015, n = 25, Z = 2.40, P < 0.01). Survival of resident females was significantly less after the decline in puma numbers (0.783 ± 0.03 vs. 0.929 ± 0.019, U = 55.0, P = 0.009). Female productivity did not differ before or after the decline in deer abundance. Our results supported the majority of the predictions concerning the impact of changing deer abundance, which supported the hypothesis that the abundance of mule deer limited our population of pumas.

Predicting the suitability of habitat in southeast Idaho for pygmy rabbits.

A geographic information system (GIS) model was developed for pygmy rabbit (Brachylagus idahoensis) habitat in southeastern Idaho. Areas of potential use by pygmy rabbits were determined from appropriate vegetation and geological classes in a GIS analysis. Sites most likely to be occupied within potential vegetation and geologic habitat were determined by including appropriate slope and aspect measurements. Randomly selected areas within and outside of predicted areas were searched for pygmy rabbit sign. This resulted in a 57% probability of predicting areas occupied by pygmy rabbits and a 100% probability of predicting areas not occupied. Our model may be useful in identifying areas unsuitable for pygmy rabbits and it is a useful first step in identifying appropriate habitat for the pygmy rabbit, potentially throughout their range.

TEMPORAL VARIATION IN COYOTE VOCALIZATION RATES

J. Wildl. Manage. 45(3):1981 in dingos (Canis familiaris dingo) (Corbett and Newsome 1975) and wolves (C. Zqus) (Zimen 1975). Observations on rates of vocalization in coyotes (C. latruns) indicate that seasonal as well as die1 patterns may exist (Bueler 1973, Gier 1975). However, documentation of these observations is lacking in the coyote literature. The objective of this paper is to document seasonal and die1 variation in coyote vocalization rates.

Bottom-up regulation of desert grassland and shrubland rodent communities: implications of species-specific reproductive potentials

Abstract We conducted an 11-year comparative study on temporal variation in rodent density, biomass, and species composition dynamics from adjacent grassland and shrubland environments in the Chihuahuan Desert of North America, in relation to rainfall and plant production. We found that rodent assemblages from those environments were only 14% similar in overall species composition, but consisted of different species in the same genera with similar ecological attributes. Each rodent community was numerically dominated by a different species of granivorous kangaroo rat, and the 2 rodent communities paralleled each other in body sizes and trophic structure. Rodent species compositions changed little over the 11-year period, despite considerable variation in rodent densities and biomass and in rainfall and plant production. Rodent abundance and biomass from both communities increased in relation to temporally variable rainfall and plant production, especially resulting from a series of El Niño and La Niña Southern Oscillation events. However, the grassland rodent community exhibited more rapid within-1-year lag-time responses to plant production, and prolonged high densities for 1 year before declining, whereas the shrubland rodent community exhibited primarily 1-year lag responses and immediate rapid decline in densities. Changes in rodent densities and biomass from both communities were significantly predicted by the production of annual grasses and forbs. Measured rodent reproductive activity was greater and happened sooner after rain and plant production events at the grass site than at the shrub site, and differences in the timing of rodent bottom-up responses between the grassland and shrubland habitats appeared to result from differences in the reproductive potentials of the 2 dominant rodent species. Dipodomys ordii, the dominant grassland rodent species, is known to produce more offspring than Dipodomys merriami, the dominant rodent in the shrubland community. We conclude that differences in the reproductive potentials of these 2 dominant rodent species likely accounted for the quicker and prolonged response of the grassland rodent community to bottom-up influences, rather than differences in the timing of plant production between the sites. Variation in reproductive potentials among rodent communities is likely a key factor affecting the timing of overall rodent community dynamics relative to changes in environmental resources.

The feasibility of the north-eastern USA supporting the return of the cougar Puma concolor

The cougar Puma concolor was part of the pre- European fauna of the north-eastern USA. It was extirpated in the late 1800s and since the late 1900s there have been discussions concerning its reintroduction to the region. One site considered is Adirondack State Park in northern New York. In 1981 an assessment of the feasibility of returning cougars concluded that the Park had adequate prey and forest cover to support a small population of cougars but that conflicts with humans would cause the demise of this population within 10 years. Thus reintroduc- tion at that time was not advised. Since then knowledge of cougar ecology and how cougars interact with humans has increased substantially. Based on information compiled since the 1980s I conducted a landscape-scale analysis to assess whether cougars could live in the Park. The results indicate that cougars could occupy 15,300-17,000 km 2 (61- 69%) of the Park, with minimal contact with human habitation. Based on reported cougar densities the Park could support a population of 150-350 cougars. These cougars would consume ,10% of the adult deer population annually and fawn production would be sufficient to replace these losses. Human and road densities in the Park are similar to those of the Black Hills, South Dakota and southern Florida, both of which have viable populations of cougars. I concluded that Adirondack State Park could supportapopulationofcougars. Whatisnowrequiredisthe will to bring them back.

Vertical distribution of soil removed by four species of burrowing rodents in disturbed and undisturbed soils.

Burrow volumes were determined in disturbed and undisturbed soils for four species of rodents in southeastern Idaho. Comparisons were made between soil types for the average volume and the proportion of the total volume of soil excavated from 10-cm increments for each species, and the relative number of burrows and proportion of total soil removed from beneath the minimum thickness of soil covers over buried low-level radioactive wastes. Burrows of montane voles (Microtus montanus) and deer mice (Peromyscus maniculatus) rarely extended below 50 cm and neither volumes nor depths were influenced by soil disturbance. Townsends ground squirrels (Spermophilus townsendii) had the deepest and most voluminous burrows that, along with Ords kangaroo rat (Dipodomys ordii) burrows, were more prevalent beneath 50 cm in disturbed soils.