Genetic Mark–Recapture Improves Estimates of Maternity Colony Size for Indiana Bats

Abstract

Genetic mark–recapture methods are increasingly being used to estimate demographic parameters in species where traditional techniques are problematic or imprecise. The federally endangered Indiana bat Myotis sodalis has declined dramatically and threats such as white-nose syndrome continue to afflict this species. To date, important demographic information for Indiana bats has been difficult to estimate precisely using traditional techniques such as emergence counts. Successful management and protection of Indiana bats requires better methods to estimate population sizes and survival rates throughout the year, particularly during summer when these bats reproduce and are widely dispersed away from their winter hibernacula. In addition, the familial makeup of maternity colonies is unknown, yet important for understanding local and regional population dynamics. We had four objectives in this study. For the first two objectives we investigated the potential use of DNA from fecal samples (fecal DNA) collected at roosts to obtain genetically based mark–recapture estimates of 1) colony size and 2) survival rates, for an Indiana bat maternity colony in Indianapolis, Indiana. The third objective was to compare our genetically based colony-size estimates with emergence counts conducted at the same roost tree to evaluate the genetic mark–recapture method. Our fourth objective was to use fecal DNA to estimate levels of relatedness among individuals sampled at the roost. In the summer of 2008, we collected fecal pellets and conducted emergence counts at a prominent roost tree during three time periods each lasting 7 or 8 d. We genotyped fecal DNA using five highly polymorphic microsatellite loci to identify individuals and used a robust-design mark–recapture approach to estimate survival rates as well as colony size at the roost tree. Emergence count estimates at the roost tree ranged from 100 to 215, whereas genetic mark–recapture estimates were higher, ranging from 122 to 266 and more precise. Apparent survival was 0.994 (SE = 0.04) between sampling periods suggesting that few bats died or permanently emigrated during the course of the study. Relatedness estimates, r, between all pairs of individuals averaged 0.055 ranging from 0 to 0.779, indicating that most individuals were not closely related. We demonstrate here the promise of using fecal DNA to estimate demographic information for Indiana bats and potentially other bat species.

Possibility for reverse zoonotic transmission of SARS-CoV-2 to free-ranging wildlife: A case study of bats

“…Examples of other “hands-off” methods applicable to both bat disease and conservation research include the following: virus discovery and characterization focused on existing specimens archived in scientific museums or through partnerships and collaboration with established national bat disease monitoring or surveillance programs [ 147 , 148 ]; monitoring echolocation calls to determine the occurrence, distributions, and seasonal or nightly activity patterns of bats [ 133 , 149 ]; digital imaging methods for counting bats and studying physiology and behaviors in the context of disease [ 90 , 108 ]; sampling guano from below bat roosts to determine bat species and individual identity, population dynamics, and daily or seasonal patterns of bat occupancy and pathogen shedding [ 71 , 150 – 152 ]; and mathematical modeling to predict susceptible host species, virus sharing among hosts, spread patterns, or to estimate mortality in affected populations [ 5 , 70 , 122 , 135 ]. Promising areas for innovation include making technologies for bat research more accessible to a broader global user base, less expensive, easier to use, and scientifically reproducible through open-source hardware, software, and laboratory methods [ 153 , 154 ].…”

Seasonal and Elevational Differences by Sex in Capture Rate of ‘Ōpe‘ape‘a (Lasiurus semotus) on Hawai‘i Island

“…The low rate of ‘ōpe‘ape‘a recapture evident in our study provides insight into the difficulty of mark-recapture studies in Hawai‘i. However, demographic and longevity data for ‘ōpe‘ape‘a could be expected to improve with long-term mist-net monitoring, use of genetic methods (Oyler-McCance et al 2018; Wright et al 2021; Van Harten et al 2022), or persistent marking techniques such as passive integrated transponder (PIT) tags.…”

Estimation of bat colony size even with low recapture rates: an example based on the Cormack-Jolly-Seber model in Oaxaca, México

“…The Light Detection and Ranging (LiDAR) scanning system allows to estimate the number of individuals per species by scanning the roosts and visually recognizing and labelling the areas occupied by each species (Shazali et al, 2017); however, the cost of this system is currently too high for its generalized use. Very recently, genetic tag-recapture methods are expensive but seem to offer advantages over other more invasive methods, although it is only recommended for species that show high fidelity to the refuge and that do not form colonies of thousands or millions of individuals (Oyler-McCance et al, 2018). Therefore, we consider that the estimation method used in the present study provides a low-cost, and reasonably reliable option for the estimation of bat colony size, especially for roosts occupied by more than one species.…”