Tagging Bats in Great Basin National Park

This article was originally published in The Midden – Great Basin National Park: Vol. 15, No. 2, Winter 2015.

Park biologists, in cooperation with partners from state agencies and academia, have learned a variety of cutting edge bat survey techniques, such as radio telemetry and PIT tagging.

These methods would be applied to understand the landscape ecology of cavernicolous bats such as this Townsend big-eared bat (Corynorhinus townsendii), prior to the predicted arrival of WNS in the Pacific West region by 2021.
Photo by Jenny Hamilton

By Dylan Rhea-Fournier, Biological Science Technician, Bryan Hamilton, Wildlife Biologist, and Meg Horner, Biologist

Bats are incredibly valuable to humans in terms of ecosystem services. As suppressors of agricultural pests they provide an estimated $40 to $53 billion worth of pest control services per year in the US alone. Yet bats are threatened by a variety of anthropogenic factors. The most pressing issue facing bats in North American is disease. White-nose Syndrome (WNS) has killed millions of bats in the northeastern US in the last decade. Unprecedented levels of mortality have led to the listing of several bat species under the Endangered Species Act.

WNS is predicted to reach White Pine County, NV, in which Great Basin National Park (GRBA) is located, within 10 years. In light of these predictions, the need for baseline information on species presence across the range of habitats, locally available roosts, and bat seasonal activity in the park are imperative. Cave dwelling (cavernicolous) colonial bats, several species of which occur in GRBA, are most susceptible to WNS due to the climate within caves and close proximity of individuals within colonies, making them of special concern.

The study of bats can often present several unique challenges. Their adaptations to nocturnal activity make them difficult to observe, and their ability to fly allows them to cross large landscapes in relatively short times, which along with their behavior of roosting out of plain sight make them difficult to track. However, advancements in wildlife research technology and the growing range of applicability of such equipment is providing researchers with new, highly useful tools.

Passive integrated transponder (PIT) tags are a form of radio-frequency identification (RFID) technology. A transponder is a device that receives an ‘interrogation’ radio signal and immediately responds with a different signal. We may be more familiar with this technology in everyday life in its use to ‘microchip’ our pet dogs and cats to help Photo by Jenny Hamilton identify them if they end up with animal control, electronic payment methods such as for public toll roads, electronic locks such as at hotels, or the new high-tech ski passes that permit them to be scanned in your pocket on a cold day.

NPS staff assist the Nevada Department of Wildlife during the annual Nevada Batweek, an event designed to gather data about bats in an area. In 2015 it was held in and near Great Basin National Park.

NPS Photo by Gretchen Baker

PIT tags were developed in the 1980s by fish biologists to track the migration of their subject species, mostly in freshwater systems.

The tag consists of an electronic microchip enclosed in glass. While still a fairly new technology for use in bats, PIT tags have proven to be a valid method of collecting vital ecological data for fish and other vertebrates with no adverse effects on growth or survival. The tags are inert, carrying no battery of their own, but instead are excited by the electromagnetic field of a reader or antennae designed for reading PIT tags (hence, passive) that activates the tag and induces an immediate response of an alphanumeric code. PIT tags offer a very reliable unique identifying number similar to a barcode, for the lifetime of the individual, and analysis of the data can provide information on sex ratios and age structure at the population level.

The utility of PIT tags in studying bats is enormous. External tags or other methods of marking are useful in other studies and with other subject animals; however, for hairy mammals like bats that periodically molt and have the ability to groom themselves or roost mates, the chance of tags attached to the fur or skin to be easily removed is high. PIT tagging can be especially useful for the study of cave dwelling bats as tag readers can be attached to an antenna that encircles the opening/exit to the cave, allowing the unique ID of each tagged bat to be read each time it exits or enters the cave.

In July, park biologists attended a workshop in Colorado with experienced Colorado Parks and Wildlife staff to learn the methods of inserting the tags subcutaneously in bats. In GRBA a total of 207 bats comprising seven different species were PIT tagged this summer at nine different sites. Several individuals were recaptured during subsequent trapping sessions. Researchers were able to confirm the ability of the bats to recover and cope with the implanting of the tag, with many bats barely showing external evidence of the insertion within a month of first capture.

Our focal species this summer was the Townsend’s Big-eared bat (Corynorhinus townsendii), a cave and mine obligate and the most abundant species in Lehman Cave. This species is both difficult to trap in mist nets at foraging sites and difficult to pick up acoustically, the two methods most often utilized by bat researchers. However, trapping them at their roosts as they exited proved successful and over 150 C.townsendii individuals were tagged this summer.

A PIT tag reader and antenna have been installed at the Lehman Cave natural entrance, with installations planned for several other caves known to be roosts. These PIT tag arrays will provide the park with useful information: the number of bats using each cave, what time of year bats use certain caves, what level of roost fidelity is exhibited, sex ratio of bats using monitored caves at different times of the year (maternity roost identification), and if multiple species of bat are using monitored caves at the same time. With the number of bats tagged at Lehman Cave and other sites this summer, park researchers and managers hope to gain life history and behavioral information from these individuals over the next decade.

This project was made possible by money from the NPS Natural Resource Stewardship and Science WNS response funding in both 2014 and 2015. The park’s Natural Resources team would like to thank all park staff that participated in capture events and for those expressing interest in the research and conservation of bats in our park.