Out in the Dark: Why Should We Look After Our Local Bat Fauna?

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NJ bat rescue

The first day of summer is about a week away. While many of us are looking forward to picnics in the park, beach trips, and vacations, a few are scrambling around with slightly different plans for the beginning of the season. Ever since the discovery of white nose syndrome (WNS) and the fungus that causes it (Pseudogymnoascus destructans [a.k.a. Pd]), scientists have taken the task of documenting, surveying, and exploring ways to find and hopefully eradicate it. This “cold-loving” fungus that has threatened bat populations in North America for over a decade is still expanding its range even in the warm summer months.

The first cases of WNS on North American bats quickly became a concern for scientists studying these flying mammals. Soon after the first ones were recorded in 2006 in New York State, WNS brought a devastating prognosis for one of the most important insect predators we have. WNS results from infection with the Pd fungus. European bats in the native range of Pd show immunity to the infection but North American bats are yet to benefit from that. This does not mean that our bat populations could never become resistant, but the process leading to it will be slow and given the mortality estimates, it will also leave its heavy mark of population loss. To put things into perspective, in just six short years after the first case of WNS, scientists estimated a loss of over 5.5 million bats (1), with colonies of little brown bats (Myotis lucifugus) losing over 90% of its members. Today, these losses are likely to remain high primarily because Pd has been spreading like wildfire across North America. Bats positive for WNS are now reported in 32 US states and 7 Canadian provinces (2). This year the first bat with WNS in Kansas was found and Pd was detected for the first time in South Dakota and Wyoming as reported by June 2018 (3). This list of places is likely to grow as bat researchers from all across North America gear up and head out to the field to catch and assess the health of their state’s bat populations and bat roosts.

Despite its proximity to the epicenter, the first report of WNS in New Jersey was made in 2009 about three years after the original report in New York. New Jersey is home to 9 bat species, all of them belong to the same family and also share an insatiable appetite for insects. Three of these species are generally known as “tree bats” (genera Lasiurus and Lasionycteris) (4), they are solitary and roost in trees alone. While tree bats can migrate, some of them fly only short distances and become torpid during the winter when insects are scarce. The other six are more typical evening bats. One is known as the tri-color bat (genus Perimyotis) and the rest are part of the “brown bats” (genera Eptesicus and Myotis) (4), which come in little & big sizes. These “six” all form colonies and generally roost in trees, caves, mines, and occasionally in buildings. They also are able to hibernate over the winter, which allows them to be year-round residents of New Jersey.

Interestingly, Pd affects almost all nine New Jersey bat species differently. None of the tree bats show symptoms of WNS, but the presence of Pd has been documented in two of them. On the other hand, all the evening bats have been affected by WNS, some of them to great extent. For example, the endangered Indiana bat (Myotis sodalis) in the northeast US lost over 75% of its population to WNS since 2007. Surveys of little brown bats in New Jersey show a 95% decline compared to estimates in 2009. While these dwindling trends are scary, recent studies show that Pd infection intensity is much lower in bat populations that persisted over a previous infection (7). This brings us the hope that some bats will recover and overcome this downward trend; yet small population sizes can easily become susceptible if not properly managed. Nonetheless, in today’s biodiversity crisis where the rate of species loss is comparable to those of a mass extinction… why does losing another species matter?

The truth is that a species is the smallest unit of biodiversity, and each species forms part of the broader network of interactions that after millions of years of evolution work to maintain a healthy sustainable planet. But even if this seems intangible, distilling this concept into its smallest unit allows us to appreciate the distinctiveness and importance of each piece of this puzzle. Our local bats dominate a unique nocturnal insectivore niche and some species are known to consume hundreds of insects every night. Take for instance, the diet of a little brown bat is made up of about 71% mosquitoes that belong to 17 different families, which means that they are not only eating a lot of them but also a greater diversity than previously known (8). Bats also provide an ecosystem service by consuming large amounts of insects that are agricultural pests, which help reduce the need for using chemical pest control. So, they are definitely saving us big bucks by eating up all of these insects because the estimated average value of this natural pest control is at least $3 billion annually in the U.S. (9) As if that was not enough, the guano produced after gobbling all of those insects is high in nitrogen and phosphorous, making it an excellent fertilizer. There is no doubt that even at a local scale we can accrue great benefits from healthy bat populations, so the least we can do is reward them for their unpaid service.

While Pd is generally described as a “cold loving” fungus that kills bats during hibernation, we should not underestimate its ability to spread during the summer months. In addition to bats changing summer roosts, humans visiting contaminated roosting sites significantly increase the potential of spore transfer. In a summer study conducted in 2012, scientists discovered that equipment brought into WNS-contaminated sites tested positive to Pd DNA in the lab. So, in other words, walking into bat roosts with unwashed boots or a backpack can result in further spread and the persistence of Pd. Developing awareness and respecting bat roosts is one way we can help our local bats overcome this hurdle. Pd is not harmful to humans. However, if you find yourself in a place with roosting bats, follow the proper decontamination protocols to reduce the likelihood of spreading Pd (10) and alert your local conservation center or state natural resource agency about the location of the roost so that it can be properly monitored and managed. Volunteering with conservation efforts to do summer bat counts is also a great way to get involved and make a difference by having the opportunity learn more and educate others about the importance of the bats in our backyard. These simple ways will ensure bats get their much deserved reward, while keeping our environment healthy and promoting sustainability on our planet for years to come.

– Angelo Soto-Centeno, guest writer @ FCW

Angelo is an evolutionary biologist and Assistant Professor of Biology at Rutgers University, Newark. He is interested in mammal biodiversity, particularly bats, and their biogeography. Angelo’s recent work tries to shed light into bat extinctions and the factors that contribute to bat population loss.

References:

  1. US Fish and Wildlife Service (2012). North American bat death toll exceeds 5.5 million from white-nose syndrome. News Release: https://www.whitenosesyndrome.org/sites/default/files/files/wns_mortality_2012_nr_final_0.pdf Accessed: 6/8/2018

  2. White-nose Syndrome occurrence map – by year (2018). Data Last Updated: 6/1/2018. Available at: https://www.whitenosesyndrome.org/resources/map Accessed: 6/8/2018

  3. White nose syndrome news (2018). Available at:  https://www.whitenosesyndrome.org/newsAccessed: 6/8/2018

  4. Maslo, B. & Leu, K. (2013). The facts about bats in New Jersey. https://njaes.rutgers.edu/fs1207/ Accessed: 6/8/2018

  5. US Fish and Wildlife Service (2017). 2017 Indiana bat (Myotis sodalis) population status update. https://www.fws.gov/Midwest/endangered/mammals/inba/pdf/2017IBatPopEstimate5July2017.pdf Accessed: 6/8/2018

  6. Conserve Wildlife Foundation of New Jersey (2017). Summer bat count report 2015.http://www.conservewildlifenj.org/downloads/cwnj_704.pdf Accessed: 6/8/2018

  7. Langwig, K.E., et al. (2017). Resistance in persisting bat populations after white nose syndrome invasion. Philosophical Transactions of the Royal Society B, 372:20160044.

  8. Wray, A.K., et al. (2018). Incidence and taxonomic richness of mosquitoes in the diets of little brown and big brown bats. Journal of Mammalogy, 99:668.

  9. Boyles, J. G., et al. (2011). Economic Importance of Bats in Agriculture, Science 332:11.

  10. National White Nose Syndrome Decontamination Protocol (2016).https://www.whitenosesyndrome.org/sites/default/files/resource/national_wns_decon_protocol_04.12.2016.pdf Accessed: 6/8/2018