The New York State Department of Environmental Conservation (DEC) has announced the results of last winter’s survey of the hibernating bats in New York. The survey was a cooperative effort among state wildlife officials, the U.S. Fish and Wildlife Service and numerous volunteers to monitor the effects of white-nose disease, a fungal infection that has devastated regional bat populations since it was first documented in a cave near Albany (in Schoharie County) in 2006. Since then white nose disease has spread throughout the South, Midwest, and eastern parts of Canada. Earlier this month new cases were identified for the first time west of the Mississippi in Missouri.
According to a study in Science, little brown myotis, a once common local species, has experienced a population collapse that could lead to its extinction in the northeastern US within 20 years. The Forest Service recently estimated that the die-off from white-nose will leave 2.4 million pounds of bugs uneaten and a financial burden to farms. A growing scientific consensus agrees the cause is Geomyces destructans; there is still debate over whether or not it was introduced from Europe by cavers.
Some encouraging observations came from the bat surveys of the five hibernation caves where the disease was first discovered. Previous reports have suggested that little brown bat counts at these sites seem to be stabilizing in recent years.
This year’s surveys saw substantial increases in little brown bats at three out of five of these caves. The largest and best documented of these sites saw an increase from 1,496 little brown bats in 2011 to 2,402 this year. It is premature to conclude that population recovery is underway for this species, however, because of the small number of hibernation sites that have experienced increases and the fact that alternate explanations are plausible. Bats are highly social animals and observed increases could be the result of consolidation of individuals from other hibernation sites, for example.
In 2010, Larry Master explained for the Almanack the impact of the disease on the nine local species of bats: “Little Brown Myotis (Myotis lucifugus), which as recently as four years ago comprised 85% of our bats, have been especially hard hit along with Northern (Long-eared) Myotis and Eastern Pipistrelles,” he wrote. “These bats are now among the rarest bats in New York.” Prior to the arrival of white-nose disease, the little brown bat was the most common bat species in New York State and has been observed hibernating in more than 100 caves and mines here. Statewide losses for the species attributed to white-nose disease remain at approximately 90 percent.
Bat populations that were already low face a devastating crisis. “60% of the known world-wide population of Small-footed Myotis (Myotis leibii) occur in the winter in just two mines in New York, the largest of those in Essex County,” Master said. Based on this year’s survey, total observed declines in population attributed to the disease for tri-colored bats have been revised upward. Prior to the arrival of white-nose disease in 2007, a total of 2,285 tri-colored bats were counted at 37 representative hibernation sites in the state. Since that time, a total of 112 bats were observed during surveys of those same sites, suggesting a statewide decline of 95 percent for the species.
Northern long-eared bats have also been affected with a 98 percent observed decline (18 individuals observed in 36 sites compared to a pre-disease total of 911 bats at the same sites). Although neither bat was considered a threatened species prior to the arrival of white-nose disease, both species are now extremely rare in New York.
No surveys were performed this year for the federal and state endangered Indiana bat. Previous surveys indicate that losses for this species have totaled 71 percent statewide (15,650 individuals remaining, down from a high of 54,689). The population status of Indiana bats in New York will be reassessed in 2013.
Records of small-footed bats, a rare species even prior to the disease, show only a relatively small decline of 13 percent. This species is difficult to count due to its secretive habits when hibernating, but focused survey efforts this season have bolstered previous observations that the impact of the disease is far less severe for small-footed’s than for most other hibernating bats.
More information on Adirondack bats and white nose syndrome:
Mary Thill wrote about witnessing the the die-off first hand in 2009. [Link]
Larry Master reported on the local situation in 2010. [Link]
Ellen Rathbone wrote about each of the Adirondack bat species in 2010. [Link]
Phil Brown reported on a visit to a Hague cave in January 2011. [Link]
Tom Kalinowski wrote about the science behind the surveys in the last fall. [Link]
You can read all the Almanack‘s stories about bats here.
Photo: A little brown bat with white-nose syndrome. Courtesy Al Hicks, NYS DEC.