Roger A. Baldwin

Use of Maximum Entropy Modeling in Wildlife Research

Maximum entropy (Maxent) modeling has great potential for identifying distributions and habitat selection of wildlife given its reliance on only presence locations. Recent studies indicate Maxent is relatively insensitive to spatial errors associated with location data, requires few locations to construct useful models, and performs better than other presence-only modeling approaches. Further advances are needed to better define model thresholds, to test model significance, and to address model selection. Additionally, development of modeling approaches is needed when using repeated sampling of known individuals to assess habitat selection. These advancements would strengthen the utility of Maxent for wildlife research and management.

Den-site characteristics of black bears in Rocky Mountain National Park, Colorado

Abstract We compared historic (1985–1992) and contemporary (2003–2006) black bear (Ursus americanus) den locations in Rocky Mountain National Park (RMNP), Colorado, USA, for habitat and physiographic attributes of den sites and used maximum entropy modeling to determine which factors were most influential in predicting den-site locations. We observed variability in the relationship between den locations and distance to trails and elevation over time. Locations of historic den sites were most associated with slope, elevation, and covertype, whereas contemporary sites were associated with slope, distance to roads, aspect, and canopy height. Although relationships to covariates differed between historic and contemporary periods, preferred den-site characteristics consistently included steep slopes and factors associated with greater snow depth. Distribution of den locations shifted toward areas closer to human developments, indicating little negative influence of this factor on den-site selection by black bears in RMNP.

DISTRIBUTION, OCCUPANCY, AND HABITAT CORRELATES OF AMERICAN MARTENS (MARTES AMERICANA) IN ROCKY MOUNTAIN NATIONAL PARK, COLORADO

Abstract A clear understanding of habitat associations of martens (Martes americana) is necessary to effectively manage and monitor populations. However, this information was lacking for martens in most of their southern range, particularly during the summer season. We studied the distribution and habitat correlates of martens from 2004 to 2006 in Rocky Mountain National Park (RMNP) across 3 spatial scales: site-specific, home-range, and landscape. We used remote-sensored cameras from early August through late October to inventory occurrence of martens and modeled occurrence as a function of habitat and landscape variables using binary response (BR) and binomial count (BC) logistic regression, and occupancy modeling (OM). We also assessed which was the most appropriate modeling technique for martens in RMNP. Of the 3 modeling techniques, OM appeared to be most appropriate given the explanatory power of derived models and its incorporation of detection probabilities, although the results from BR and BC provided corroborating evidence of important habitat correlates. Location of sites in the western portion of the park, riparian mixed-conifer stands, and mixed-conifer with aspen patches were most frequently positively correlated with occurrence of martens, whereas more xeric and open sites were avoided. Additionally, OM yielded unbiased occupancy values ranging from 91% to 100% and 20% to 30% for the western and eastern portions of RMNP, respectively.

Perceived damage and areas of needed research for wildlife pests of California agriculture.

Many wildlife species cause extensive damage to a variety of agricultural commodities in California, with estimates of damage in the hundreds of millions annually. Given the limited availability of resources to solve all human-wildlife conflicts, we should focus management efforts on issues that provide the greatest benefit to agricultural commodities in California. This survey provides quantitative data on research needs to better guide future efforts in developing more effective, practical and appropriate methods for managing these species. We found that ground squirrels, pocket gophers, birds, wild pigs, coyotes and voles were the most common agricultural wildlife pest species in California. The damage caused by these species could be quite high, but varied by agricultural commodity. For most species, common forms of damage included loss of crop production and direct death of the plant, although livestock depredation was the greatest concern for coyotes. Control methods used most frequently and those deemed most effective varied by pest species, although greater advancements in control methods were listed as a top research priority for all species. Collectively, the use of toxicants, biocontrol and trapping were the most preferred methods for control, but this varied by species. In general, integrated pest management practices were used to control wildlife pests, with a special preference for those approaches that were efficacious and quick and inexpensive to apply. This information and survey design should be useful in establishing research and management priorities for wildlife pest species in California and other similar regions.

Foods and nutritional components of diets of black bear in Rocky Mountain National Park, Colorado.

We used scat analysis to determine diets and relative nutritional values of diets for black bears (Ursus americanus Pallas, 1780) in Rocky Mountain National Park, Colorado, from 2003 to 2006, and c...

Denning Chronology of Black Bears in Eastern Rocky Mountain National Park, Colorado

ABSTRACT. Understanding factors influencing the timing of den entrance and emergence of black bears (Ursus americanus) provides insight for bear management. We determined den entrance and emergence dates for bears in Rocky Mountain National Park (RMNP) and related these dates to vegetative productivity, weather, habitat, and demographic factors to assess the influence of these factors on denning chronology. Date of den entrance was most strongly influenced by age class, precipitation, and proportion of human-use areas in annual home ranges. Den entrance was typically later for adult bears during wetter years and when annual home ranges contained a greater proportion of human-use areas. Sex and presence of human-use areas were most strongly related to den emergence. Male bears typically emerged from dens before females, and bears emerged from dens earlier when human-use areas composed a greater proportion of annual home ranges. Collectively, our results suggest that denning behavior of black bears in RMNP was strongly influenced by presence of human-use areas, likely because of foods associated with such areas. Managers of black bears in RMNP can use precipitation to predict relative dates of den entrance, thereby allowing for more efficient strategies to combat potentially negative human—black bear encounters.

An efficacy test of cholecalciferol plus diphacinone rodenticide baits for California voles (Microtus californicus Peale) to replace ineffective chlorophacinone baits

California voles cause damage to pastures and rangelands, orchards and nurseries, and a wide variety of field crops, including artichokes. The anticoagulant rodenticides (chlorophacinone and diphacinone) typically used for voles are becoming less effective in controlling their populations. Consequently, there is a need to identify new rodenticides that will have a high efficacy on California voles so that agricultural production losses to rodents can be substantially reduced. We tested a new formulation containing two active ingredients (cholecalciferol and diphacinone) as a control method for California voles. Both a pelleted bait and an oil-coated artichoke bract bait were very palatable and efficacious against wild-caught, captive California voles. Efficacy levels of 70%–80% were achieved in the two-choice feeding trials. Additionally, the days-to-death (5–6 days) were less than the time-to-death with anticoagulant only baits. We recommend that a field efficacy study be conducted with cholecalciferol plus diphacinone bait formulations to determine their field performance in the reduction of agricultural damage by California voles.

HABITATS OCCUPIED BY ELK (CERVUS ELAPHUS) IN DESERT GRASSLAND-SCRUBLANDS OF NORTHWESTERN NEW MEXICO

Abstract We studied habitat relationships of elk (Cervus elaphus) at scales of landscape, home range, and site on and adjacent to Chaco Culture National Historical Park, San Juan and McKinley counties, New Mexico. Across scales, use of habitats was driven by needs for cover. Pinyon–juniper and rocky habitats were used most often. Accrual of body fat was related most strongly to lactation and precipitation but also was influenced by several habitats, most strongly by semi-desert shrub-steppe. Habitats positively related to accrual of body fat were used less than available at scales of landscape and home range. Conversely, habitats preferentially included and used in home ranges were related negatively to accrual of body fat, further highlighting the importance of cover. At the level of site, feeding sites had greater cover by shrubs (≥23% versus 25% versus <11%) than did bedding sites, whereas bedding sites had higher overstory cover (≥46% versus ≤4%). Bedding sites most frequently ...

Novel and current rodenticides for pocket gopher Thomomys spp. management in vineyards: what works?

BACKGROUND Rodenticides are often included as part of an integrated pest management approach for managing pocket gophers (Thomomys spp.) given that they are relatively quick and inexpensive to apply. Strychnine has historically been the most effective toxicant for pocket gophers, but its use is currently limited in the United States; alternative registered toxicants have not proven effective. Recent research with baits containing cholecalciferol plus anticoagulant toxicants proved effective against pocket gophers in a lab setting. Therefore, we established a field study to compare cholecalciferol plus anticoagulant combinations [0.03% cholecalciferol plus 0.005% diphacinone (C + D), 0.015% cholecalciferol plus 0.0025% brodifacoum (C + B1), 0.03% cholecalciferol plus 0.0025% brodifacoum (C + B2)] with strychnine (0.5%) for pocket gopher management. RESULTS Strychnine treatments resulted in 100% efficacy after two treatment periods. Both C + D and C + B2 resulted in efficacy significantly greater than 70% after two treatment periods (83 and 75% respectively). Efficacy from C + B1 (85%) was not significantly greater than 70%, but did yield high overall efficacy as well. CONCLUSION Although strychnine remains the most effective rodenticide for pocket gopher control, the cholecalciferol plus anticoagulant baits tested would be a good alternative when strychnine is unavailable. C + D may be the best option given that it uses a first-generation anticoagulant as the synergist.

Use of external characteristics for rapid identification of gender of pocket gophers

Abstract. Pocket gophers are of great importance both for their function in ecological systems and for their impact on anthropogenic environments. Managing pocket gopher populations requires a fundamental understanding of population demographics, specifically sex ratios; yet quick and reliable techniques for visually identifying gender of pocket gophers are lacking. We developed a visual identification method based on external characteristics of genitalia and mammae that allows for rapid, yet correct assessment of gender in pocket gophers. This approach was particularly accurate (>99%) for visual identifications in the field. Our approach was also accurate (>98%) for frozen specimens, although care must be taken when identifying gender of frozen, immature pocket gophers. Although our results pertain specifically to Thomomys talpoides and Thomomys bottae, we believe that our methodology can be broadly applied to additional pocket gopher species.