Using Noninvasive Genetic Sampling to Assess and Monitor Grizzly Bear Population Status in the Northern Continental Divide Ecosystem

Wildlife managers need reliable estimates of population size, trend, and distribution to recover at–risk populations, yet obtaining these estimates is costly and often imprecise. The threatened grizzly bear (Ursus arctos) population in northwestern Montana has been managed for recovery since 1975, yet no rigorous data were available to evaluate the program’s success. We assessed population status using data from a large noninvasive genetic sampling project and 33–years of physical captures. Our abundance estimate, Nˆ= 765 (CV = 3.8%), was more than double the working estimate. Based on our results, the total known, human–caused mortality rate was 4.6%, slightly above the 4% level considered sustainable. Genetic diversity approached levels seen in relatively undisturbed populations, with the only signal of population fragmentation that aligned with landscape features being across U.S. Highway 2. I used these encounter data to parameterized a series of simulations to assess the ability of noninvasive genetic sampling, specifically surveys of naturally occurring bear rubs, to estimate population growth rates. I used data on 379 grizzly bears identified from bear rub surveys in a range of Pradel model simulations in program MARK. I evaluated model performance in terms of: (1) power to detect declines in population abundance, (2) precision and relative bias of estimates, and (3) sampling effort required to achieve 80% power to detect a decline within 10 years. Simulations suggest that annual bear rub surveys would exceed 80% power to detect a 3% annual decline within 6 years. Robust design models with 2 surveys per year provide precise and unbiased estimates of trend and abundance. Designs with 1 survey per year are less expensive but only yield trend and apparent survival estimates. I provide recommendations for designing a program to monitor population trends by sampling at bear rubs. Systematic bear rub surveys may provide a viable alternative to telemetry–based methods for monitoring trends in grizzly bear populations. This study illustrates the power of molecular techniques to rapidly assess population status and trends at landscape scales and provide detailed demographic and genetic data to guide and evaluate recovery efforts

Estimating Abundance of Adult Trachemys scripta with Camera Traps: Accuracy, Precision and Probabilities of Capture for a Closed Population

Low and variable rates of capture are common problems when estimating abundance of freshwater turtles with capture-mark-recapture (CMR). We speculated camera traps would allow us to obtain reliable estimates of abundance by re-sighting marked Trachemys scripta elegans (Sliders) as they basked on man-made rafts during a 20-day surveillance period. We evaluated the method by releasing Sliders in a fenced enclosure to compare estimates from CMR to true abundance. We also evaluated probabilities of detection and retention of marks. Permanence of marks applied with marine epoxy satisfied assumptions for CMR. Camera traps detected 23 of 25 Sliders. Our ability to discern marks from photos was good (110 of 114 re-sightings). The proportion of marked Sliders detected per day was 0.22; detection varied with day of surveillance (1–20) and maximum air temperature the preceding day. All CMR models providing valid estimates of abundance included the true number of marked Sliders in their confidence intervals and yielded point estimates within 27% of the true value. An estimate of abundance from the top CMR model exceeded the true value by 22%, with a wide confidence interval. Model averaging improved the point estimate (17% over true) and produced a narrower confidence interval. A favorable comparison of estimated and true abundance validated camera traps as a tool for estimating abundance of adult Sliders. We believe camera traps could prove useful for detecting biases caused by primary methods of capture, refining estimates of abundance from other methods and collecting data at multiple locations consistently, simultaneously and frugally compared to manual methods alone

Abundance and genetic structure of two black bear populations prior to highway construction in eastern North Carolina

A 19.3-km segment of U.S. Highway 64 in Washington County, North Carolina is being re-routed and upgraded to a 4-lane highway in what is considered to be crucial black bear (Ursus americanus) habitat. To lessen the impacts on bears and other wildlife, 3 passageways are currently under construction in this segment of highway. In 2000, I began research on a project to determine the effects of the 4-lane highway on black bear ecology and to determine whether wildlife passageways can mitigate impacts of such highways. Research was divided into 2 phases: before highway construction (phase I; June 2000-June 2001) and after the anticipated completion of the highway (phase II; 2005). In addition to the treatment area (area of the proposed highway) a control area was established. I collected baseline information during phase I by estimating population abundance and density on the 2 study areas with DNA from hair samples collected from barbed-wire enclosures. Microsatellite analysis of the DNA was used to identify individual bears for mark-recapture estimates. I examined 3 different groups of closed population estimation models (modified Lincoln-Petersen, Bailey\u27s triple catch, and multiple mark-recapture models). A multiple mark-recapture model with varying capture probabilities provided the best fit to the data and produced the most precise population estimates. Population estimates for the treatment and control areas were 85 (1.20 bears/km2) and 165 (1.78 bears/km2), respectively. Differences in density may be related to differences in hunting pressure; however, both densities were high because of large tracts of forests interspersed with agricultural food crops. Additionally, I used the microsatellite data to compare genetic relatedness, population structure, and gene flow between the treatment and control areas, between areas north and south of the proposed highway within the treatment area, and between areas north and south of a fictitious highway within the control area. The genetic distance between the north and south populations within the treatment area was greater than the genetic distance between the treatment and control areas and between areas north and south of the fictitious highway within the control area. Unrooted neighbor-joining trees constructed from the genetic distance analyses suggested some subpopulation structure. The FST values (0.029, 0.040, and 0.006 for the 3 scales, respectively), which measure the reduction in heterozygosity of subpopulations relative to the entire population, indicated that the amount of population structure was low, but slightly greater within the treatment area than between the 2 study areas or within the control area. Gene flow rates also supported those results, with fewer individuals traveling north and south of the proposed highway (3.3 migrants per generation) than between the 2 study areas (4.6 migrants per generation) or between the north and south populations within the control area (7.6 migrants per generation). I examined isolation-by-distance with Mantel tests to determine relationships between genetic distance and geographic distance based on sample locations. Male bears showed less isolation-by-distance (r = 0.06) than female bears (r = 0.26), probably because of larger home range sizes, which may also explain why the overall population structure was low. Thus, because of the relatively small scale of the study, the unrooted trees likely depict family structure rather than population structure. Finally, I used a geographic information system (GIS) to map allelic diversity throughout the 2 study areas. Allelic diversity was positively correlated with forest density (r = 0.29), indicating that the size and, possibly, the connectivity of habitat patches plays a role in gene exchange, even on a small scale. The density and genetic structure patterns I observed for black bears on the 2 study areas before highway construction will be crucial to understanding the potential impacts of the highway on black bear ecology. However, it may be some time before potential genetic impacts can be detected once highway construction is completed

Estimating Grizzly and Black Bear Population Abundance and Trend in Banff National Park Using Noninvasive Genetic Sampling

We evaluated the potential of two noninvasive genetic sampling methods, hair traps and bear rub surveys, to estimate population abundance and trend of grizzly (Ursus arctos) and black bear (U. americanus) populations in Banff National Park, Alberta, Canada. Using Huggins closed population mark-recapture models, we obtained the first precise abundance estimates for grizzly bears ( = 73.5, 95% CI = 64–94 in 2006;  = 50.4, 95% CI = 49–59 in 2008) and black bears ( = 62.6, 95% CI = 51–89 in 2006;  = 81.8, 95% CI = 72–102 in 2008) in the Bow Valley. Hair traps had high detection rates for female grizzlies, and male and female black bears, but extremely low detection rates for male grizzlies. Conversely, bear rubs had high detection rates for male and female grizzlies, but low rates for black bears. We estimated realized population growth rates, lambda, for grizzly bear males ( = 0.93, 95% CI = 0.74–1.17) and females ( = 0.90, 95% CI = 0.67–1.20) using Pradel open population models with three years of bear rub data. Lambda estimates are supported by abundance estimates from combined hair trap/bear rub closed population models and are consistent with a system that is likely driven by high levels of human-caused mortality. Our results suggest that bear rub surveys would provide an efficient and powerful means to inventory and monitor grizzly bear populations in the Central Canadian Rocky Mountains

Evaluation of the Effects of Stage Fluctuations on Overwinter Survial and Movement of Young Colorado Pikeminnow in the Green River, Utah, 1999-2002

Each component of the Flaming Gorge Winter study had specific objectives to address oncerning the effects of winter operations of Flaming Gorge Dam on the survival, distribution, and ursery habitats of age-O Colorado pileeminnow. n Table I, study objectives for each project are resented and the reader is directed to the relevant draft report. The Colorado River Fish Project-Vernal, tah, was responsible for conducting field investigations (i.e., population estimates, winter fish sampling, nd monitoring stage fluctuations) in the alluvial reach occupied by age-O Colorado pileeminnow. olorado State University was responsible for characterizing movement rates under simulated winter onditions; and developing and eValuating a bioenergetics model for age-O Colorado pileeminnow

A decade of humpback whale abundance estimates at Bermuda, an oceanic migratory stopover site

We constructed annual abundance of a migratory baleen whale at an oceanic stopover site to elucidate temporal changes in Bermuda, an area with increasing anthropogenic activity. The annual abundance of North Atlantic humpback whales visiting Bermuda between 2011 and 2020 was estimated using photo-identification capture-recapture data for 1,204 whales, collected between December 2009 and May 2020. Owing to a sparse data set, we combined a Cormack-Jolly-Seber (CJS) model, fit through maximum likelihood estimation, with a Horvitz-Thompson estimator to calculate abundance and used stratified bootstrap resampling to derive 95% confidence intervals (CI). We accounted for temporal heterogeneity in detection and sighting rates via a catch-effort model and, guided by goodness-of-fit testing, considered models that accounted for transience. A model incorporating modified sighting effort and time-varying transience was selected using (corrected) Akaike’s Information Criterion (AICc). The survival probability of non-transient animals was 0.97 (95% CI 0.91-0.98), which is comparable with other studies. The rate of transience increased gradually from 2011 to 2018, before a large drop in 2019. Abundance varied from 786 individuals (95% CI 593-964) in 2016 to 1,434 (95% CI 924-1,908) in 2020, with a non-significant linear increase across the period and interannual fluctuations. These abundance estimates confirm the importance of Bermuda for migrating North Atlantic humpback whales and should encourage a review of cetacean conservation measures in Bermudian waters, including area-based management tools. Moreover, in line with the time series presented here, regional abundance estimates should be updated across the North Atlantic to facilitate population monitoring over the entire migratory range