In 2024, the fungus that causes white-nose syndrome in bats was detected in several counties across California, although bats with visible signs of the disease have yet to be observed in the state. White-nose syndrome has killed millions of bats since it was first detected in New York in 2006. Hibernating bats like little brown myotis, Yuma myotis, and cave myotis are especially vulnerable to the disease. White-nose syndrome develops when the fungus Pseudogymnoascus destructans invades bat skin cells, damaging delicate wing tissue. Bats with white-nose syndrome end hibernation early when water and insect prey resources are scarce, which often results in dehydration and depletion of fat reserves. As a result, infected bats often perish. In 2023, the California Department of Fish and Wildlife first confirmed presence of the fungus in a bat roost in Humboldt County. In 2024, the fungus was also confirmed present in Sutter, Placer, Amador, and Inyo counties. Inconclusive laboratory results suggest the fungus may also be present in several other counties. Presence of the fungal pathogen suggests the disease could manifest in California’s hibernating bats within the next few years. Sustained efforts to monitor bat populations will be critical to understanding and managing this devastating disease.

Loss of roosting habitat is widely understood as one of the major causes of declining bat populations worldwide. While some species of bats have adapted to the use of anthropogenic structures (e.g., bridges and culverts) for roosting, this behavior also renders these bat colonies vulnerable during structure widening, seismic retrofit, maintenance, and replacement projects. Efforts made to minimize and mitigate impacts to bats are not always successful because many biologists and environmental planners developing mitigation are not knowledgeable about the natural history or ecology of bats or how to provide appropriate mitigation, there is little published literature available on successful mitigation strategies, and because “one size fits all” mitigation measures are not applicable to bat roosts. After designing and implementing dozens of successful mitigation projects for bats in Southern California, we have developed an informal protocol for creating effective mitigation strategies for transportation projects involving bat roosts. This presentation discusses examples of ways in which mitigation for bats can fail and how to avoid the most common pitfalls. This presentation also proposes a systematic, stepwise approach that can be used for a variety of transportation infrastructure and even other types of projects to minimize and mitigate potential impacts to bats.

Silver-haired bats (Lasionycteris noctivagans) are one of the most widely distributed forest bats in North America. Although wildfires have been increasing across their range, how they respond to wildfire is understudied. Previous studies on silver-haired bats and fire predominantly focused on roosting behavior in low-severity controlled burns or used acoustics to understand activity levels post-wildfire. Quantifying how silver-haired bats use the physical structures created by high-severity wildfires is critical in the face of rapidly shifting fire regimes. During the summer of 2023 and 2024 we radio-tracked 68 male and 23 female silver-haired bats to 41 roosts on the Lassen National Forest. Preliminary results indicate that bats used taller and larger-diameter trees compared to randomly selected trees on the landscape. Of these roosts, 87% were in stands burned at high severity. With fire frequency and severity forecasted to increase in the coming years, it is important to understand how areas that were thought devoid of life are potentially used by bats and inform post-fire management efforts

Bats comprise one-fifth of all mammal species and are critically important to maintaining healthy ecosystems yet are often misunderstood by the public. Bats are ecosystem indicators, meaning that their presence or absence implies the conditions of their habitat. Importantly, we can use bats as a proxy for determining the status of recovery of habitats following natural disasters like fire. While wildfires are a natural part of California’s landscape, the fire season in California and across the West starts earlier and ends later each year, with climate change considered to be the key driver of this trend. To understand how wildfire is affecting the diversity and abundance of bats, I conducted echolocation surveys in 2021-2022 within the SQF Complex, which burned in Sequoia National Forest and adjacent areas in August 2020. The goal of the study was to determine how the number of bat species and composition of bat species in a habitat change in response to the degree of fire severity. This information is crucial to understanding how bats are adapting to fires, encouraging appropriate habitat management and conservation efforts of an order facing numerous threats.

An unprecedented global increase in wildfires has disrupted ecosystems and has displaced wildlife through habitat and resource loss. Despite this, recent studies have suggested that some bats, specifically the California myotis (Myotis californicus), take advantage of a post-fire landscape's increased foraging and roosting opportunities. To understand how bats adapt to living in a post-fire landscape, we used telemetry to radio-track bats to roosts within the Mosquito fire burn scar in Tahoe National Forest, June-August 2024. Roost selection was quantified as a function of burn severity as well as tree characteristics. Burn severity is defined by the Rapid Assessment of Vegetation After-Fire Index (RAVF). Additionally, temperature-sensitive dataloggers were placed in an around roost trees to thermally profile the preferred microclimate of M. californicus to understand how roost microclimate affects roost selection. I hypothesize that roost selection of the California myotis is influenced by roost microclimate, which can be altered by fire. Results from this study will help inform wildlife managers how to manage landscape for more optimal roosting habitat of the California myotis, and will further elucidate the complex relationship between bats and wildlife in California.

Electronic nose (e-nose) devices analyze volatile organic compound (VOC) signatures and may be used to determine the Pd-infection status of bats early in the hibernation period and prior to visible symptom development without the need for tactile captures or handling which disturb bats. An e-nose investigation of whole-body VOC emissions from Tricolored bats (Perimyotis subflavus), sampled noninvasively within 13 caves and 2 mines in Arkansas, showed that most tricolored bats are relatively disease free when first entering caves, but acquire Pd-infections over time, often leading to WNS disease development at variable rates prior to the exiting of surviving bats from caves in the Spring. Healthy bats exhibited significantly different E-nose smellprint signatures than Pd-infected bats, both prior to and following disease and associated WNS symptom development. These differences in VOC emissions were indicative of Pd-induced pathophysiological changes that occur in bat metabolic pathways associated with pathogenesis during the progression from healthy to early and late WNS disease states. The e-nose approach provides a new noninvasive tool for monitoring changes in bat physiological processes that occur from healthy to diseased states during winter hibernation periods, allowing for earlier confirmation of disease and treatment applications.

Since 1968 I have been studying and banding Macrotus californicus in the low deserts of California and Arizona. With a narrow thermal-neutral zone, this species doesn't hibernate or migrate, relying primarily on behavioral adaptations and roost selection. I will share insights into their social system including stable female groups, leks in the fall and delayed embryonic development. They glean large insects and lizards from vegetation using combinations of echolocation, vision and prey-produced sounds. Threats to this species include the exploration of caves and closure of mines, and the loss of foraging habitat through development, most recently solar farms.

Pesticides in the environment lead to issues in human health, environmental degradation, and inhibited wildlife function. Natural forms of pest control include carnivores and insectivores that consume agricultural pests. Studying the diet of bats within the agricultural landscape will reveal if they are eating agricultural pests. Documentation of bat quantities and species presence in known roosts, along with diet, will assist in estimating pest suppression impact on local growers. The results of this study will fill essential gaps in western bat knowledge and inform agricultural pest management on the benefits of decreasing their usage of chemical pesticides and increasing the utilization of bats as natural pest management. This may lead to a natural pest management plan that will promote an organic way of growing food for the health of wildlife, the environment and produce consumers. Once a month for a year we will collect guano and estimate colony size and species composition from four known bat bridge roosts across Ventura County’s Santa Clara River Valley (California). We will use metabarcoding, to identify agricultural pests, pollinators, and vectors in the diet of four bat species: the Mexican free-tailed, Pallid bat, Big brown bat, and Myotis spp. Revealing bat diet may determine if grower’s pesticides target the same pests that bats consume. Quantifying bat abundance, species composition, and identifying diet each month can also inform growers in what months is most beneficial to use less pesticides. Lacking knowledge on diet and bat behavior, throughout the seasons will be illuminated through studying a potential facilitative relationship between agriculture and wildlife this will uncover what major agricultural pests are being consumed by bats.