The Depths We Go… to Study Bats

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Bat Conservation International, TPWD Nongame and Rare Species Program, and Texas A&M University biologists and volunteers during bat surveys in the Texas Panhandle.

Texas bats are in danger. White-nose syndrome (WNS), a devastating fungal disease, is almost here. The disease is caused by a fungus that thrives in the cold environments where bats hibernate. Hibernating bats with WNS often display white fungus on their noses and other hairless parts of their bodies, including their wings.The fungus isn’t always visible to the naked eye, however, and usually is not seen on bats found flying or dead outside of their hibernacula or at their summer roosts.

White-nosed syndrome kills bats during hibernation by agitating their skin which causes them to wake up and preen. This expends their extremely limited energy reserves needed to sustain them for the entire winter and can eventually lead to starvation.

White-nosed syndrome was first discovered in New York in 2006 and has since spread westward towards Texas at a rate of about 200 miles a year. The disease is responsible for the deaths of nearly six million bats across North America. It is now just 170 miles from the Texas border in Arkansas and was just recently found in eastern Oklahoma. White-nosed syndrome does not affect humans.wns_map_20160216.jpg

Texas hosts 32 species of bats, more than any other U.S. state. Three species of Texas bats are known to be impacted by WNS and five others have been found with the fungus but exhibit no disease symptoms. The effects of WNS on the remaining 25 bat species in Texas are not known.

Many bats can live for 20 years or more and are very slow to reproduce. Stressors, such as introduced diseases like WNS, can result in significant population declines and push species towards regional extirpations or even extinction. The loss of bats due to WNS could have wide-ranging impacts to the ecosystem services provided by these night-flying, insectivorous mammals. From a human perspective, bats provide billions of dollars in pest control to agriculture annually through their insect feeding activities. Loss of bat populations would likely raise agricultural costs and increase pesticide applications.

Fortunately, the Mexican free-tailed bats, which roost in the millions in Bracken Bat Cave, Old Tunnel State Park, and the Congress Avenue Bridge in Austin, migrate instead of hibernate during the winter months. While this will likely shield them from the worst effects of the disease, Mexican free-tailed bats could still spread the fungus to more susceptible species across the western U.S.

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Biologist examines a bat in a Texas Panhandle cave.

The Nongame and Rare Species Program at Texas Parks and Wildlife Department is partnering with Bat Conservation International and Texas A&M University to monitor bat populations and the spread of WNS. In early February 2016, biologists from both groups, along with some dedicated volunteers, met in the Texas Panhandle (Childress County) to test bats in several caves for WNS. Caves in this region of Texas are thought to contain environmental conditions (cold, humid) conducive to WNS infection.

Biologists searched caves for bats and when found, counted and swabbed individuals to test for WNS infection. The biologists are currently looking for additional caves in northern Texas to sample for the disease. This work is being supported by a grant through the U.S. Fish and Wildlife Service’s White-nose Syndrome Grants to States and the Pittman-Roberson Grants Programs. For more information about this disease visit White-nose Syndrome.org.

 

Desert Massasauga: Results of Recent Genetic Work

massassauga_Hibbitts_copyrightThe Massasauga (Sistrurus catenatus) consists of three subspecies: the Eastern (S. c. catenatus), Western (S. c. tergeminus), and Desert Massasaugas (S. c. edwardsii).  Relationships among these subspecies pose challenges for conservation and management in Texas where both Western and Desert Massasauga subspecies occur.  The Western Massasauga has no special state or federal status, while the Desert Massasagua has been petitioned for federal listing under the U.S. Endangered Species Act.

In 2012, to better define the status of Massasauga subspecies in Texas, the Nongame and Rare Species Program at Texas Parks and Wildlife Department funded a genetic study conducted by researchers with the Institute of Renewable Natural Resources at Texas A&M University. This work was made possible through TPWD’s State Wildlife Grant Program.  Ryberg et al. (2013) used nuclear and mitochondrial DNA variation to define the geographic relationships between Western and Desert Massasaugas in Texas and adjacent states.  The researchers also assessed baseline population structure throughout the state and discussed the establishment of potential management units for Desert Massasauga should listing occur.

They found strong evidence that the Western and Desert Massasaugas are genetically indistinguishable for the genes investigated. Within the Western-Desert Massasauga group, they found some evidence of population structure among five population segments. These five distinct population segments could be considered for listing, but with no clear evidence suggesting relationships among these disjunct populations, they recommend that more research using other molecular markers be conducted to provide a measure of genetic connectivity capable of revealing more detailed taxonomic and population level structure for identifying potential conservation units.

Regardless of federal ruling, the overall rarity of Massasaugas in south Texas and their geographic isolation from other populations in the Western-Desert Massassauga group means that they deserve continued attention. The researchers recommend continued survey efforts in this region to provide information on the distribution and abundance of this Massasauga population and to monitor changes to its habitat over time.

Ryberg, W.A., A. Blick, J.A. Harvey, T.J. Hibbitts, and G. Voelker.  2013.  Genetic determination of the Desert Massassauga distribution in Texas.  State Wildlife Grant Report to Texas Parks and Wildlife Department.