When generalists behave as specialists: local specialization by American badgers (Taxidea taxus)

Differentiating species according to their relative niche breadth is a common approach in community ecology that can enhance understanding about how species relate to the environment. Although a species might exhibit a generalized ecology across its entire range, on a local scale, individuals might function as specialists. American badgers (Taxidea taxus (Schreber, 1777)) are terrestrial carnivores that have been described most often as generalists. We compared patterns of habitat selection by badgers at 3 scales to test the hypothesis that badgers would exhibit behaviors more closely aligned with specialists than generalists when inhabiting landscapes with black-tailed prairie dogs (Cynomys ludovicianus (Ord, 1815)). At a course scale, badgers selected for prairie dog colonies across the landscape. At an intermediate scale, we documented significantly greater use of prairie dog colonies within the home ranges of badgers. At fine scales within colonies, badgers used areas that had relatively high densities of prairie dog burrows, where prey was presumably abundant. On multiple scales, badgers exhibited a narrow use of resources in comparison to the resources available. Our study provides additional evidence that badgers behave as specialists when burrowing rodents are highly concentrated and predictable over space and time.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Differential sex-related winter energetics in free-ranging snowshoe hares.

Animals spend considerable time and energy acquiring food to meet their metabolic requirements, but if energetic or fitness costs are substantive, such as during winter, some individuals may limit daily energy expenditure by reducing foraging duration. To date the prevalence and magnitude of such compensatory foraging responses are poorly known. We examined energy balance compensation in free-ranging snowshoe hares (Lepus americanus (Erxleben 1777)) via a food supplementation experiment to determine whether individuals reduced their daily energy expenditure (DEE) and activity periods in response to increased food availability. Overall, food supplementation had no effect on diel activity patterns, although males had higher DEE compared to females. During early- and mid-winter, hares did not alter their activity periods in response to food supplementation, but during late-winter, when natural food availability declined, food-supplemented females (but not males) were ~11% less active compared to controls. Natural food likely was sufficient and could have been acquired at relatively low energetic cost, but because males likely have higher DEE due to mating behavior, whereas females may limit their activity (and thus DEE) to reduce predation risk, we conclude that gender-specific life history demands can over-ride predicted responses to supplemental food when baseline food abundance is adequate.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Transition of Vegetation States Positively Affects Harvester Ants in the Great Basin, United States

Invasions by non-native plants can alter ecosystems such that new ecological states are reached, but less is known about how these transitions influence animal populations. Sagebrush (Artemisia tridentata) ecosystems are experiencing state changes because of fire and invasion by exotic annual grasses. Our goal was to study the effects of these state changes on the Owyhee and western harvester ants (Pogonomyrmex salinus Olsen and P. occidentalis Cresson, respectively). We sampled 358 1-ha plots across the northern Great Basin,which captured unburned and burned conditions across 1-31 years postfire. Our results indicated an immediate and consistent change in vegetation states fromshrubland to grassland between 1 and 31 years postfire. Harvester ant occupancy was unrelated to time since fire, whereas we observed a positive effect of fire on nest density. Similarly, we discovered that fire and invasion by exotic annuals were weak predictors of harvester ant occupancy but strong predictors of nest density. Occupancy of harvester ants wasmore likely in areas with finer-textured soils, low precipitation, abundant native forbs, and low shrub cover. Nest densitywas higher in arid locations that recently burned and exhibited abundant exotic annual and perennial (exotic and native) grasses. Finally,we discovered that burned areas that received postfire restoration had minimal influence on harvester ant occupancy or nest density compared with burned and untreated areas. These results suggest that fire-induced state changes from native shrublands to grasslands dominated by non-native grasses have a positive effect on density of harvester ants (but not occupancy), and that postfire restoration does not appear to positively or negatively affect harvester ants. Although wildfire and invasion by exotic annual grasses may negatively affect other species, harvester ants may indeed be one of the few winners among a myriad of losers linked to vegetation state changes within sagebrush ecosystems. © 2016 The Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information