Northern Long-eared Bats Survive White-nose Syndrome in Man-made Habitats

Published in August 2021 @HarvestingNature

Since its first identification in a cave in New York in 2006, white-nose syndrome (WNS) in bats has caused significant population declines. White-nose syndrome is caused by a fungus, Pseudogymnoascus destructans, that infects the skin of the muzzle, ears, and wings of hibernating bat species across 35 states and seven Canadian provinces at present[1]. The fungus thrives in cold, damp conditions, perfectly suited for winter cave hibernacula. As it grows, the fungus causes changes in hibernating bats that make them become more active than usual and burn fat they need to survive the winter[2].

Northern long-eared bats (Nyctophilus arnhemensis) suffered a 95 percent population decline in New England between 2006-2012 due to WNS, and are now listed as “threatened” under the Endangered Species Act. Similar declines have been document in the little brown bat (Myotis lucifugus), among others.

While studying WNS and bats in their winter hibernacula, researchers tracked a small number of bats hibernating in home crawl spaces, basements, and other structures like concrete culverts in Martha’s Vineyard, Nantucket, and Long Island, New York. Luanne Johnson with Biodiversity Works reported that these bats were surviving the winter even when affected by WNS.

Crawl-spaces with dirt floors and homes with block foundations and BILCO style hatch doors are attractive bat hibernacula. Uninsulated foundations provide the proper temperature and humidity, allowing bats to hibernate all winter, where insulated foundations were used occasionally. Bats were tracked leaving the hibernacula occasionally in late winter in Martha’s Vineyard where water was available year-round, but the bats returned to continue hibernation and survived to spring.

Unlike WSN-affected bats wintering in cave hibernacula, bats also affected by WSN and utilizing man-made hibernacula maintained good weight and overall health throughout the winter. Some bats were tracked for up to three years without suffering severe complications from WNS. Another behavioral distinction between cave-dwelling bats and those selecting human homes is that the bats wintering in crawl spaces were tracked foraging much later in the fall, meaning these bats may have entered hibernation with better fat stores for a shorter hibernation period.

Additionally, Auteri and Knowles (2020)[3] found genetic evidence of little brown bats evolving with WNS. Allelic frequencies showed significant shifts in survivors for regulating arousal from hibernation, fat breakdown, and vocalizations.  Studies by Biodiversity Works and their partners suggest that bats hibernating in homes are less likely to succumb to WNS, allowing more time for bats to evolve to survive the disease. Therefore, Biodiversity Works is working with homeowners tolerant of bats to potentially treat the WNS fungus on their property and construct new hibernacula onsite if homeowners want the bats out of their basement. Also, they are working with contractors and homeowners to heighten awareness of bats hibernating in homes to minimize potential harm from construction or remodels.


[1] White-Nose Syndrome (usgs.gov)

[2] White-Nose Syndrome (whitenosesyndrome.org)

[3] First genetic evidence of resistance in some bats to white-nose syndrome, a devastating fungal disease — ScienceDaily

Tree Removal Benefits Greater Sage Grouse Population Growth

Tree Removal Benefits Greater Sage Grouse Population Growth – Harvesting Nature

Woody plant expansion into shrub and grasslands poses a significant ecosystem issue for multiple uses. In the Great Basin of North America, pinyon–juniper expansion into the sagebrush biome is threatening the greater sage grouse, a sagebrush obligate species, as well as pronghorn, mule deer, and livestock grazing due a major shift in the vegetation community and associated ecosystem components.

According to Brianna Randall of the Sage Grouse Initiative (SGI), “More than one million acres of sagebrush grazing lands in the Great Basin have turned into pinyon-juniper forests in the past two decades alone.”

This is problematic for sage grouse because they avoid landscapes with trees, likely because trees provide raptor perching and nesting habitat. Additionally, trees crowd out and take precious water from perennial grasses, forbs, and other plants that a variety of wildlife rely on, and can effectively reduce habitat carrying capacity and suitability, causing species to relocate.

Protecting and restoring the sagebrush ecosystem is at the forefront of the Natural Recourse Conservation Service (NRCS) mission. Through the NRCS Working Lands for Wildlife program, the SGI was born and includes partnerships with other land management agencies, universities, and landowners. As a collective, these entities work to enhance the sagebrush ecosystem for cooperative wildlife and agricultural uses.

Sage grouse on the lek. (Photo credit USFWS)

Since approximately 2011, a pinyon–juniper removal effort has been underway in the Warner Mountains in south-central Oregon. Concurrently, researchers GPS-tracked 417 hen sage grouse over a 109,000-acre “treatment” area with active tree removal.

Study results published in June (Olsen et al. 2021) show that within the treatment area, sage grouse population growth rates increased approximately 12 percent within five years of tree removal compared to a population within an adjacent 82,000-acre “control” or area with no tree removal. Similarly, a 2017 SGI report identified that 29 percent of tracked hen sage grouse in Oregon returned to restored nesting habitats within four years post-restoration. Encouraging results for the future of sage grouse and the sagebrush ecosystem.

The rarity in seeing such positive population results from habitat management was summarized appropriately by Olsen et al. (2021).

“Examples of positive, population-level responses to habitat management are exceptionally rare for terrestrial vertebrates, and this study provides promising evidence of active management that can be implemented to aid recovery of an imperiled species and biome.”  

References

Olsen, AC., JP Severson, LD Maestas, DE Naugle, JT Smith, JD Tack, KH Yates, and CA Hagen. 2021. Reversing tree expansion in sagebrush steppe yields population-level benefit for imperiled grouse. Ecosphere https://doi.org/10.1002/ecs2.3551.

Sage Grouse Initiative. 2017. Conifer Removal Boosts Sage Grouse Success. Science to Solutions Series Number 12. Conifer Removal Boosts Sage Grouse Success – Sage Grouse Initiative