Geology topics

John T. Hast

Publications and source records attributed to John T. Hast.

3 recordsLinked to original sources

USGS2022

Density, harvest rates, and growth of a reintroduced American black bear population

Less than 30% of all species reintroductions have been successful and it is important that factors associated with success or failure be identified. Officials experimentally translocated 14 adult female American black bears ( Ursus americanus ) from Great Smoky Mountains National Park, North Carolina and Tennessee, USA, to Big South Fork National River and Recreation Area in the Cumberland Plateau of Kentucky and Tennessee, USA, in 1996–1997. Since that time, the reintroduced bear population has continued to expand in size and range so our study objective was to use spatially explicit capture-recapture methods across a wide spatial extent to estimate bear population abundance and growth. We constructed 440 (223 in KY, 217 in TN) hair traps in our primary sampling area in 2019 arranged in clusters of 4–9 traps/cluster, which we augmented with data from 138 hair traps in a secondary sampling area in Tennessee collected in 2018. We extracted and genotyped DNA from hair samples to construct spatially explicit capture histories, using spatial covariates to model inhomogeneous densities. Population abundance estimates across our 36,035-km 2 study area were 411 males and 406 females excluding cubs. Based on an initial standing population of 18 adult and subadult bears, the mean annual growth rate ( λ ) from 1998 to 2019 was 1.199. The mean annual harvest rate in Kentucky from 2013 to 2019 was 5.1% and in Tennessee from 2014 to 2019 was 13.2%. Based on simulations, the hunting seasons reduced mean λ from 1.217 to 1.199, but growth was rapid despite harvest. Genetic diversity was retained, with similar expected heterozygosity as in the source population. The lack of conspecifics, highly productive habitat, and an initial age and sex distribution that was skewed toward the most fecund members of the population likely contributed to the rapid growth and high levels of gene retention in this bear population.

Kentucky, Tennessee↗

USGS2019

Early genetic outcomes of American black bear reintroductions in the Central Appalachians, USA

Habitat loss and overexploitation extirpated American black bears (Ursus americanus) from most of the Central Appalachians, USA, by the early twentieth century. To attempt to restore bears to the southwestern portion of this region, 2 reintroductions that used small founder groups (n = 27 and 55 bears), but different release methods (hard versus soft), were conducted during the 1990s. We collected hair samples from black bears in the reintroduced Big South Fork (BSF) and Kentucky–Virginia populations (KVP), their respective Great Smoky Mountains (GSM) and Shenandoah National Park (SNP) source populations, and a neighboring population in southern West Virginia (SWV) to investigate the early genetic outcomes of bear reintroduction. Despite having undergone genetic bottlenecks, genetic diversity remained similar between reintroduced populations and their sources ~15 years after the founder events (ranges: AR = 4.86–5.61; HO = 0.67–0.75; HE = 0.65–0.71). Effective population sizes of the reintroduced KVP and BSF (NE = 31 and 36, respectively) were substantially smaller than their respective SNP and GSM sources (NE = 119 and 156, respectively), supporting founder effects. Genetic structure analysis indicated that the hard released (i.e., no acclimation period) KVP founder group likely declined considerably, whereas the soft released BSF founder group remained mostly intact, suggesting superior effectiveness of soft releases. Asymmetrical gene flow via immigration from the SWV has resulted in the KVP recovering from the initial founder group reduction. Sustained isolation, small NE, and small population size of the BSF may warrant continued genetic monitoring to determine if gene flow from neighboring populations is established or NE declines. For future bear reintroductions, we suggest managers consider sourcing founders from populations with high genetic diversity and soft-releasing bears to locales that are, if possible, within the dispersal capability of extant populations to mitigate the potential consequences of founder effects and isolation.

Central Appalachians↗

USGS2015

Rapid growth and genetic diversity retention in an isolated reintroduced black bear population in the central appalachians

Animal reintroductions are important tools of wildlife management to restore species to their historical range, and they can also create unique opportunities to study population dynamics and genetics from founder events. We used non-invasive hair sampling in a systematic, closed-population capture-mark-recapture (CMR) study design at the Big South Fork (BSF) area in Kentucky during 2010 and Tennessee during 2012 to estimate the demographic and genetic characteristics of the black bear ( Ursus americanus ) population that resulted from a reintroduced founding population of 18 bears in 1998. We estimated 38 (95% CI: 31–66) and 190 (95% CI: 170–219) bears on the Kentucky and Tennessee study areas, respectively. Based on the Tennessee abundance estimate alone, the mean annual growth rate was 18.3% (95% CI: 17.4–19.5%) from 1998 to 2012. We also compared the genetic characteristics of bears sampled during 2010–2012 to bears in the population during 2000–2002, 2–4 years following reintroduction, and to the source population. We found that the level of genetic diversity since reintroduction as indicated by expected heterozygosity ( H E ) remained relatively constant ( H E(source, 2004)  = 0.763, H E(BSF, 2000–2002)  = 0.729, H E(BSF, 2010–2012)  = 0.712) and the effective number of breeders ( N B ) remained low but had increased since reintroduction in the absence of sufficient immigration ( N B(BSF, 2000–2002)  = 12, N B(BSF, 2010–2012)   = 35). This bear population appears to be genetically isolated, but contrary to our expectations, we did not find evidence of genetic diversity loss or other deleterious genetic effects typically observed from small founder groups. We attribute that to high initial genetic diversity in the founder group combined with overlapping generations and rapid population growth. Although the population remains relatively small, the reintroduction using a small founder group appears to be demographically and genetically sustainable.

Kentucky, Tennessee↗