Hoary bats (Lasiurus cinereus) are renowned as the longest distance migratory bat species in North America, but specific details on such movements are few. During autumn, hoary bats are vulnerable to impacts from wind turbine operation and engage in two activities vitally important to their annual life cycle: mating and moving between summer and winter habitat. In 2014, we began using a new generation of lightweight devices and a newly developed suture attachment method which allowed multi-month attachment and expanded the possibilities for understanding these movements in California. Over the years, we have used geolocators, connectivity tags, and lightweight GPS tags to gain insights into their movement ecology. In 2022, we began using tags compatible with the Motus automated radio-telemetry system and its burgeoning network of receivers throughout Pacific states to enhance our understanding of seasonal movements. We demonstrate the lack of predictability in autumn movements among individuals while at the same time identifying some potential hotspots of autumn activity by hoary bats. We also compare pros and cons of the various tracking devices we have used, concluding that advancing the Motus network is the best way to enhance our understanding of the seasonal movements of bats.

Raptor predation on bats occurs globally across a range of raptor and bat species. Colonially roosting bats that emerge in abundance are particularly vulnerable to avian predators. This threat likely constitutes selective pressure for bat nocturnality and preference for day-roosts that are out of reach of vision-oriented predators. Bats remaining well within crevice day roosts are generally considered safe from avian predation. We document novel daytime predation of roosting bats by adult Cooper’s hawk (Accipiter cooperii) from a maternity colony of Mexican free-tailed bats (Tadarida brasiliensis mexicanus). We observed this behavior repeatedly over several weeks late in the hawk nesting effort, during the colony’s pupping season. Based on the observed attack success rate, we anticipate the potential for colony-level effects. We seek other observations of bat predation within day roosts to assess the extent of this predation pressure on crevice-roosting bats more broadly, and to consider potential management implications for anthropogenic roost structures. Continued observations of our study roost may shed light on magnitude of impact to local predator-prey populations, prey species response, whether hawk offspring learn to take advantage of this foraging resource, and other intricacies of this potentially new relationship between two urban-tolerant wildlife species.

Legacy mining in California has left an estimated 200,000 hazardous abandoned mine features throughout the state. These mines, if left unremediated, pose a hazard for humans and the environment but are nonetheless critical habitat for bats and other wildlife. Several California Species of Special Concern, especially Townsend’s big-eared bat and California leaf-nosed bat use mines for hibernation, maternity, and other life history stages. The California Department of Conservation’s Abandoned Mine Lands Unit (AMLU) partners with federal, state, and local agencies to protect the public by closing mine entrances. Although maintaining bat habitat has long been a prime consideration when planning remediations, AMLU has revised our approach to consider bat habitat protection throughout the project lifecycle. We now employ a more bat-focused approach from the onset by conducting underground surveys of mines as early as the initial inventory phase to identify bat habitat for future remediation projects. By using a combination of historical bat surveys and our ongoing surveys, we can provide partners with the best remediation option for each feature by considering mine related habitat at a regional and statewide scale. Importantly, we can also identify wildlife friendly remediations that would benefit from continuous monitoring. This critical step can track changing conditions, caused by events such as human vandalism, wildfires, and unstable geology.

CDFW partners with other agencies, landowners, and academic and private sector biologists to conduct both active and passive surveillance for White-nose Syndrome (WNS), a deadly fungal disease affecting bats. CDFW’s “Report a Sick or Dead Bat” and “Report a Bat Colony” webpages provide opportunities for the public to report bats that may be affected by WNS. CDFW also screens hundreds of bats submitted to public health departments each year for signs suggestive of WNS. To date, WNS has not been detected through these passive surveillance channels. Active surveillance by qPCR testing of swab samples from live bats captured and released during early spring was conducted at 10 and 11 sites across California in 2022 and 2023, respectively. In 2023, while most samples returned negative results, swab samples from bats at 7 sites in 6 counties yielded high Ct value positive results (these are considered inconclusive results), and one site yielded two samples with low Ct value positives (true positives). These are the first true positive detections of Pd in California. The 2023 results from CDFW’s surveillance add to the low-level detections of Pd obtained by partner surveillance projects, with a total of 10 California counties now showing such results.

Public perceptions of bats have historically been negative, and the potential origins of the ongoing Covid-19 pandemic have further cast a negative light onto the Chiropteran order.  Since 2020, our group of volunteers has annually collected ultrasonic acoustic data on bat populations in Southern California under the framework of the North American Bat (NABat) program.  The process of adopting NABat cells, deploying acoustic detectors, and analyzing the data collected, has engaged a diverse group of volunteers and increased awareness among group members.  By initiating and engaging volunteers (professional and not professional) in bat acoustics associated with NABat, we have created ambassadors that promote bat population awareness.

Habitat destruction and degradation is one of the leading causes of bat population declines. In California, population growth has caused a loss of over 90% of the state’s wetlands while 95% of the riparian habitats of San Joaquin Valley have been converted to agriculture and development. Although some environmental laws help conserve bat habitat, there’s a need to restore lands to provide all aspects of bats’ habitat requirements. Each species of bat has a complex life history, and every aspect of its natural history and life cycle needs to be fully functioning. While most bat species do not typically use bat houses, many environmental documents require only bat houses to mitigate for lost bat habitat. Only rarely do restoration projects (such as for Hawaiian hoary bat and the pallid bat) attempt to fully restore bat habitat. Riparian and wetland habitat restoration is a huge step in the right direction to restore bat habitat; but ideally, habitat restoration for bats should be species specific, address every aspect of the target species’ habitat needs year round as appropriate, and should include long-term monitoring so that bat ecologists can learn from experiences.