Complementary network-based approaches for exploring genetic structure and functional connectivity in two vulnerable, endemic ground squirrels

The persistence of small populations is influenced by genetic structure and functional connectivity. We used two network-based approaches to understand the persistence of the northern Idaho ground squirrel (Urocitellus brunneus) and the southern Idaho ground squirrel (U. endemicus), two congeners of conservation concern. These graph theoretic approaches are conventionally applied to social or transportation networks, but here are used to study population persistence and connectivity. Population graph analyses revealed that local extinction rapidly reduced connectivity for the southern species, while connectivity for the northern species could be maintained following local extinction. Results from gravity models complemented those of population graph analyses, and indicated that potential vegetation productivity and topography drove connectivity in the northern species. For the southern species, development (roads) and small-scale topography reduced connectivity, while greater potential vegetation productivity increased connectivity. Taken together, the results of the two network-based methods (population graph analyses and gravity models) suggest the need for increased conservation action for the southern species, and that management efforts have been effective at maintaining habitat quality throughout the current range of the northern species. To prevent further declines, we encourage the continuation of management efforts for the northern species, whereas conservation of the southern species requires active management and additional measures to curtail habitat fragmentation. Our combination of population graph analyses and gravity models can inform conservation strategies of other species exhibiting patchy distributions

Factors influencing the road mortality of snakes on the Upper Snake River Plain, Idaho

This study documents the magnitude of road mortality on snake species that occur in sagebrush steppe habitat, provides insight into how susceptibility to this mortality differs among species as well as by sex and age class of individuals, and examines how different landscape variables influence road-kill aggregations using a logistic regression model. I collected data by road cruising a 183-km road loop on the upper Snake River Plain in southeastern Idaho from May through October of 2003. I conducted 56 total routes, traveling 10,248 km and encountering a total of 253 snakes (0.025 snakes/km) over the six-month survey period; 93 percent of these animals were found dead on the road surface (DOR). The majority of observations belonged to two species, with gophersnakes (Pituophis catenifer) comprising 75 percent of all road records, and western rattlesnakes (Crotalus oreganus) comprising 18 percent of all road records. Monitoring data from three of the largest snake hibernacula on the site indicate that rattlesnakes are the most abundant snake species, comprising 50 percent of all captures at trapping arrays since 1994. This suggests that gophersnakes may be more susceptible to road mortality due to higher vagility, or that our monitoring efforts do not effectively estimate their populations; this question remains to be explored. Overall, I documented more traffic casualties of adults than any other age class, the majority of which were males (64%). Road mortality varied seasonally by age and sex classes for both gophersnakes and rattlesnakes. More adult male gophersnakes were discovered DOR in May and June, while the death of adult females did not exhibit a trend. I documented a significant pulse of subadult mortality during the month of September. The seasonal trends in mortality of rattlesnakes differed from gophersnakes, but were not significant. This indicates that individuals may be more susceptible to road mortality during specific movements, such as mating or migration. The logistic regression indicated that increased cover of grass along roadsides, basalt piles, and mean distance to den were positively associated with gophersnake occurrence on roads. As most grasses on the site are invasive, this result implies that habitat change due to invasive species may be increasing susceptibility of gophersnakes to mortality

A Review of the Broad Effects Generated by Roads on Herpetofauna

Although, several reviews, bibliographies, and texts describing the effects of roads on natural systems have been published, amphibian and reptile taxa remain underrepresented.An array of studies document that roads generate ecological disturbance and destruction at multiple scales across the landscape. As conflicts between roads and wildlife become increasingly common, experts seek to understand the interactions in the search for solutions. Although, several reviews, bibliographies, and texts describing the effects of roads on natural systems have been published (Andrews 1990, Forman and Alexander 1998, Trombulak and Frissell 2000, Forman et al. 2003, White and Ernst 2003) amphibian and reptile taxa remain underrepresented. The extent of the direct and indirect effects of roads on these species has been revealed in numerous studies, with excessive rates of mortality (thousands) documented, and changes in behavior, movement, survival, growth, and reproductive success of individual animals reported. Cumulatively, effects may incur population-level consequences, or influence the overall species richness and diversity in an area. The goals of this presentation are to: 1) provide examples of physiological, ecological, and behavioral traits inherent among herpetofauna that enhance their susceptibility to environmental changes associated with development and roads, 2) summarize the prevalence of direct mortality data for herpetofauna, 3) identify the diversity of indirect effects documented in the literature, 4) infer larger-scale impacts on population and community levels, 5) recommend areas of future research that are to date undocumented, but for which herpetofauna are likely susceptible, and 6) present proactive approaches for addressing conflicts

A Review of the Broad Effects Generated by Roads on Herpetofauna

Although, several reviews, bibliographies, and texts describing the effects of roads on natural systems have been published, amphibian and reptile taxa remain underrepresented.An array of studies document that roads generate ecological disturbance and destruction at multiple scales across the landscape. As conflicts between roads and wildlife become increasingly common, experts seek to understand the interactions in the search for solutions. Although, several reviews, bibliographies, and texts describing the effects of roads on natural systems have been published (Andrews 1990, Forman and Alexander 1998, Trombulak and Frissell 2000, Forman et al. 2003, White and Ernst 2003) amphibian and reptile taxa remain underrepresented. The extent of the direct and indirect effects of roads on these species has been revealed in numerous studies, with excessive rates of mortality (thousands) documented, and changes in behavior, movement, survival, growth, and reproductive success of individual animals reported. Cumulatively, effects may incur population-level consequences, or influence the overall species richness and diversity in an area. The goals of this presentation are to: 1) provide examples of physiological, ecological, and behavioral traits inherent among herpetofauna that enhance their susceptibility to environmental changes associated with development and roads, 2) summarize the prevalence of direct mortality data for herpetofauna, 3) identify the diversity of indirect effects documented in the literature, 4) infer larger-scale impacts on population and community levels, 5) recommend areas of future research that are to date undocumented, but for which herpetofauna are likely susceptible, and 6) present proactive approaches for addressing conflicts

Ecological Effects of Roads Infrastructure on Herpetofauna: Understanding Biology and Increasing Communication

Roads are the ultimate manifestation of urbanization, providing essential connectivity within and between rural and heavily populated areas. Roads permeate national forests and other established wilderness areas; consequently, no areas in the U.S. are protected from this expanding infrastructure. The ecological impacts roads have on herpetofauna across temporal and spatial scales are profound, beginning during the early states of construction and progressing through to completion and daily use. Herpetofauna have the potential to be negatively influenced from roads as a consequence of urbanization, either directly from on-road mortality or indirectly as a result of a variety of ecological impacts and enabled human accessibility. The quality and the potential severity of indirect impacts of roads and urban development on amphibians and reptiles far exceed those incurred from direct mortality and wildlife although our understanding of these indirect consequences is premature. Our objective for this presentation is to: 1) summarize the prevalence of data on direct mortality of herpetofauna, 2) to characterize the diversity of indirect effects from roads, 3) to suggest larger-scale impacts on population and community levels, and 4) to recommend areas of future research for impacts that are undocumented but for which herpetofauna are likely susceptible based on their ecological strategies. Lastly, we present approaches for resolving and preventing conflicts between wildlife and roads. While some on-road mortality can be minimized in some instances for some species with road crossings, the mitigation of indirect effects such as pollution can be accomplished with these measures. In light of the many indirect effects that have been identified and the many more that remain to be documented, proactive transportation planning, public education, and communication among the professional sectors of society are the most effective way to minimize and mitigate road impacts and the only effective mechanism for avoidance of road impacts