Improving the science and practice of using artificial roosts for bats

Worldwide, artificial bat roosts (e.g., bat boxes, bark mimics, bat condos) are routinely deployed for conservation, mitigation, and community engagement. However, scant attention has been paid to developing best practices for the use of artificial roosts as conservation tools. Although bats readily occupy artificial roosts, occupancy and abundance data are misleading indicators of habitat quality. Lacking information on bat behavior, health, and fitness in artificial roosts, their conservation efficacy cannot be adequately validated. We considered the proximal and ultimate factors, such as evolutionarily reliable cues, that may prompt bats to preferentially use and show fidelity to suboptimal artificial roosts even when high-quality alternatives are available. Possible negative health and fitness consequences for artificial roost inhabitants include exposure to unstable and extreme microclimates in poorly designed roosts, and vulnerability to larger numbers of ectoparasites in longer lasting artificial roosts that house larger bat colonies than in natural roosts. Bats using artificial roosts may have lower survival rates if predators have easy access to roosts placed in conspicuous locations. Bats may be lured into occupying low-quality habitats if attractive artificial roosts are deployed on polluted urban and agricultural landscapes. To advance the science behind artificial bat roosts, we present testable research hypotheses and suggestions to improve the quality of artificial roosts for bats and decrease risks to occupants. Because continued loss of natural roosts may increase reliance on alternatives, such as artificial roosts, it is imperative that this conservation practice be improved.

Species-specific responses to white-nose syndrome in the Great Lakes region

White-nose syndrome is a fungal disease that is threatening bat populations across North America. The disease primarily affects cave-hibernating bats by depleting fat reserves during hibernation and causing a range of other physiological consequences when immune responses are suppressed. Since it was first detected in 2006, the disease has killed millions of bats and is responsible for extensive local extinctions. To better understand the effects of white-nose syndrome on various bat species, we analyzed summer acoustic survey data collected from 2016 to 2020 at nine US National Parks within the Great Lakes region. We examined the effect that white-nose syndrome, time of the year relative to pup volancy, habitat type, and regional variation (i.e., park) have on the acoustic abundance (i.e., mean call abundance) of six bat species. As expected, little brown bat (Myotis lucifugus) and northern long-eared bat (Myotis septentrionalis), both hibernating species, experienced a significant decline in acoustic abundance following white-nose syndrome detection. We observed a significant increase in acoustic abundance as white-nose syndrome progressed for hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans), both migratory species that are not impacted by the disease. Contrary to our predictions, we observed an increase in big brown bat (Eptesicus fuscus; hibernating) acoustic abundance and a decrease in eastern red bat (Lasiurus borealis; migratory) acoustic abundance following the detection of white-nose syndrome. We did not observe any significant changes after the onset of white-nose syndrome in the seasonal patterns of acoustic activity related to pup volancy, suggesting that production or recruitment of young may not be affected by the disease. Our results suggest that white-nose syndrome is affecting the acoustic abundance of certain species; however, these changes may not be a result of reduced reproductive success caused by the disease. In addition, species population dynamics may be indirectly affected by white-nose syndrome as a result of reduced competition or a foraging niche release. We also found that for parks located at higher latitudes, little brown bat and northern long-eared bat were more likely to experience greater declines in acoustic abundance as a result of white-nose syndrome. Our work provides insight into species-specific responses to white-nose syndrome at a regional scale and examines factors that may facilitate resistance or resiliency to the disease.

Assessing Global Efforts in the Selection of Vertebrates as Umbrella Species for Conservation

The umbrella-species strategy has been proposed as an attainable tool to achieve multi-species and community conservation with limited investment. There have been many umbrella-related studies since the concept's inception; thus, a summary of global study efforts and recommended umbrella species is important for understanding advances in the field and facilitating conservation applications. Here, we collated 213 recommended umbrella species of terrestrial vertebrates from 242 scientific articles published during 1984-2021 and analyzed their geographic patterns, biological features, and conservation statuses to identify global trends in the selection of umbrella species. We found a considerable geographic bias: most studies and, consequently, recommended umbrella species are from the Northern Hemisphere. There is also a strong taxonomic bias, with grouses (order Galliformes) and large carnivores being the most popular umbrella species and amphibians and reptiles being largely overlooked. In addition, wide-ranging and non-threatened species were frequently recommended as umbrella species. Given the observed biases and trends, we caution that appropriate species need to be chosen for each location, and it is important to confirm that popular, wide-ranging species are effective umbrella species. Moreover, amphibians and reptiles should be investigated for their potential as umbrella species. The umbrella-species strategy has many strengths and, if applied appropriately, may be one of the best options in today's conservation research and funding landscape.

Seasonal variation in home range size of evening bats (Nycticeius humeralis) in an urban environment

Despite the negative impacts of urbanization on bats, green spaces in urban environments, such as parks, cemeteries, and golf courses, have the potential to provide resources necessary for these animals. Water resources in these areas include natural or semi-natural ponds, streams, and drainage ditches. Such water resources, however, are frequently ephemeral when subject to prolonged periods of high temperatures and low precipitation. We hypothesized that home ranges of evening bats (Nycticeius humeralis) would increase in size or shift from urban green spaces into surrounding neighborhoods to access alternative resources, such as residential swimming pools, when water resources in green spaces are scarce. To explore whether seasonal variations in bat home ranges occurred, we radio-tracked resident evening bats in a local park system during their summer activity period 2017–2019 in Fort Worth, Texas, USA. We used Local Convex Hulls created by associating point locations with their nearest neighbor to estimate home range size, location, and the percentage area that fell within the surrounding neighborhood. We compared these variables to temperature and precipitation using various regression models. We successfully tracked 30 bats over the 3-year period and found a positive correlation between home range size and temperature. Home range sizes increased 6-fold when temperatures exceeded 30°C. Our study indicates the importance of urban neighborhoods surrounding green spaces in providing alternative resources, such as water, for bats. If managed appropriately, these urban areas have the potential to act as oases for bat populations.