Increasing the effectiveness of monitoring abundance, migratory patterns, and border impacts of an endangered pollinator, the lesser long-nosed bat

In 2010-2011 and a decade later in 2021, University of Arizona Professor Robert J. Steidl partnered with the National Park Service on a DS-CESU project to study the lesser long-nosed bat. The project, Increasing the effectiveness of monitoring abundance, migratory patterns, and border impacts of an endangered pollinator, the lesser long-nosed bat, investigated whether changes in climate and increases in border protection activities and infrastructure in the southwestern U.S. were associated with changes in the phenology of the lesser long-nosed bat. In partnership with University of Arizona collaborator A. Elizabeth Arnold, Steidl’s project had three main goals: (1) to characterize seasonal variation in abundance of bats and phenology of their food plants at roosts throughout the border region, (2) mark individuals with PIT tags to evaluate movements, and (3) provide a proof-of-concept for using fecal DNA to identify individual bats as a potential strategy for long-term monitoring. The investigators reported tangible results through rigorous research, study, and experiments. 

Between 2010-2011 and 2021, Steidl and Arnold, along with their graduate students John Walker and Ana Cerro, characterized phenology of bats along the Arizona-Mexico border by video-recording emergences every 7-14 days from maternity roosts and transient roosts. To evaluate synchrony of the bats’ phenology with that of their key food plants, they estimated abundance of bats and the proportion of food plants in flower and fruit. They found that peak abundance of bats decreased at maternity roosts by an average of 7% and increased at transient roosts by 42% over the study period. Across the same timeframe, they observed slight changes in flowering and fruiting phenology of Saguaro and Organ Pipe cacti, two key food plants for breeding lesser long-nosed bats. They observed only modest changes in phenology of bats and their key foods in the border region between 2010-2011 and 2021. 

Steidl and Arnold, along with students, volunteers, partners, homeowners, agencies, and colleagues that included Sandy Wolf and Dave Dalton of Bat Research and Consulting, tagged 196 bats with PIT tags to observe their movement across the landscape. They observed several marked individuals moving between maternity roosts on both sizes of the border during the breeding season. In 2018 and 2019, they marked bats with PIT tags at a maternity roost in Organ Pipe Cactus National Monument (ORPI) and at hummingbird feeders across southern Arizona. They installed equipment to detect PIT tags at three roost locations: ORPI, Coronado National Memorial, and Saguaro National Park. They also teamed up with biologists at Fort Huachuca Military Reservation who monitored bats at a roost on the land they manage. With help of Mexican collaborators, the team observed multiple females moving between roosts at ORPI and a roost across the border in the Pinacate Reserve, Sonora, Mexico. These observations illustrate the high mobility of the species as well as the power of PIT-tagging as a technique when sufficient bats are marked and roosts are monitored. 

To evaluate a potential strategy for long-term monitoring, Steidl and Arnold developed and optimized an inexpensive, non-invasive approach based on microsatellite analysis of DNA from feces to ‘fingerprint’ individual lesser long-nosed bats. In their initial screening, five focal loci distinguished more than 400 individuals reliably, with a genotyping error rate of <2%. The researchers generated a DNA library of over 1500 DNA extractions and >15,000 fecal samples. DNA from feces of animals that forage on nectar and fruit, including many bats, often is low in quality and quantity, so it was not clear whether fecal DNA could be used to identify individuals and therefore be used to inform movements or to estimate abundance. They learned, however, that non-invasive genetic sampling can be a cost-efficient and practical approach for studying bats without having to capture, handle, injure, or otherwise disturb them. The findings from this NPS-sponsored project provide a proof-of-concept for reliably identifying individual lesser long-nosed bats via a non-invasive and low-cost DNA fingerprint, with a general workflow that is readily transferable to other species of nectivores and frugivore that may be of conservation concern.  

Together, these efforts have generated new information on the abundance, movements, and methods to study lesser long-nosed bats, which pollinate columnar cacti and agave across much of Mexico and the southwestern U.S. These studies also provide a baseline estimate of bat abundance across key roosts in the region, setting the stage for future monitoring efforts.