First Bat Proposed as Endangered Due to White-nose Syndrome
Not surprisingly, the Service received a petition to list two bats as threatened or endangered due to potential impacts of white-nose syndrome. White-nose syndrome is a devastating disease that has killed millions of bats in the northeastern United States and is spreading into the Southeast and Midwest. A map documenting the spread can be seen at http://www.whitenosesyndrome.org/resources/map. Since finding evidence of white-nose syndrome in 2006, biologists have feared the consequences – and each year their worst fears have been realized. They observed mortality rates of up to 90 to 100 percent at hibernacula in the Northeast and documented newly affected caves and mines as the disease spread from state to state; and the high mortality rate seems to be maintaining as the disease spreads.
Species petitioned for Endangered Species Act protection were the northern long-eared and eastern small-footed bats. In response to the petition to list these bats, Jill Utrup from the Minnesota-Wisconsin Ecological Services Field Office compiled information and conducted an analysis of threats for the northern long-eared bat, while Melinda Turner from State College, Pennsylvania, Ecological Services Field Office did the same for the eastern small-footed bat. Based on their work, a final decision was made that the eastern small-footed did not warrant listing but the northern long-eared bat should be proposed as endangered.
The northern long-eared bat is one of the bats most affected by white-nose syndrome; its numbers have declined by 99 percent in northeastern caves and mines where it hibernates (collectively called hibernacula). Summer surveys have confirmed this level of decline at 93 to 98 percent. Also, although some bat populations have stabilized post-white nose syndrome (albeit at drastically reduced levels), we have no evidence that this is the case for the northern long-eared bat. For example, each of 14 populations surveyed in New York, Vermont, Connecticut and Massachusetts became locally extinct within two years due to disease, and no population remained 5 years after white-nose syndrome.
In contrast to the northern long-eared bat, white-nose syndrome did not significantly reduce numbers of hibernating eastern small-footed bats. Interestingly, eastern small-footed bats appear less susceptible to white nose syndrome, possibly because of their hibernating behavior. They are among the last bats to enter hibernacula in fall and the first to emerge in spring, and during mild winters they may not enter caves and mines at all. More time spent outside of caves and mines means less time for the fungus to grow. Within hibernacula, eastern small-footed bats tend to hibernate in drier areas with greater temperature fluctuations – less ideal conditions for fungal growth. In contrast, northern long-eared bats enter hibernation earlier in fall, leave later in spring and they tend to hibernate in the most humid areas.
The northern long-eared bat is found in 39 states (including the District of Columbia) as well as in all Canadian provinces from the Atlantic coast west to the southern Northwest Territories and eastern British Columbia. Despite this large range, the population decline in the Northeast is of particular concern because the East was considered the core of its range, where it was most common before white-nose syndrome. It has always been less common to rare in the southern and western edges of its range.
While northern long-eared bats hibernate in caves and mines during winter, they spend summer in wooded areas. During the day they roost alone or in small colonies underneath bark, in cavities or in crevices of both live trees and snags. At dusk they emerge from roosts to fly through the understory of forested hillsides and ridges feeding on insects. Although white-nose syndrome threatens the existence of this bat, because it is a proposed endangered species, all sources of mortality and harm are being evaluated.
Due to the species’ large range and its summer habitat requirements, many Ecological Services field offices and federal action agencies are concerned about the impact of this listing – both in terms of our ability to conserve this bat and how Endangered Species Act listing will affect work load. In future articles we will talk about what we are doing to ensure conservation of the northern long-eared bat and why.
-- Kim Mitchell,