Bats

Please Don’t Disturb Bats

Caves are often critical habitat for bats, providing them with safe and stable roosting opportunities where they can avoid disturbance and predation and allow for the ability to raise their pups.  While there are many thousands of caves in the US, it is estimated that less than 5% of them provide suitable environments for bats.  Many caves are special not just for their formations, but because they provide very unique and unusual habitat for animals, fungi and plants…. many species have evolved within these rare caves and exist nowhere else on earth!

There are 45 species of bats that live in the US, although only 16 can be found within Washington and Oregon.  All of them are insectivorous, feeding voraciously on insects all summer long.  Some females can consume up to 100% of their body weight in insects in one night, and need this energy to produce milk for their pup.  They also need to rebuild their fat reserves before winter so they can live off their fat during hibernation when there are no insects to eat.  Bats use caves for hibernation because these sites maintain stable, cold (but not freezing) temperatures with high humidity.  Bats require cold and humid caves for hibernation in the freezing regions of the country so that they can enter a deep state of torpor (hibernation) when insect prey is not available.  A couple species will fly south or west to California or Mexico during winter, but most species enter hibernation in the Pacific Northwest.  Bats may also use caves as maternity roosts to raise their pups, because they are usually safe from predators and disturbance.  Maternity roosts need to be much warmer than roosts used for hibernation, and very few caves in the PNW offer these warm temperatures.  Sometimes cold temperatures can be found deeper in a cave and be a good hibernation site, while other parts of a cave may be warmer and offer a good maternity roost site. 

Male and female bats will hibernate together in the same roost and usually mate in the autumn just prior to hibernation.  They may mate during winter as well, when they occasionally arouse from hibernation.  Once spring arrives, males and females usually segregate, with the females assembling in maternity colonies to raise their pups.  These maternity colonies may be in caves, trees, cliffs, buildings or other structures, with each species having their own preference for structure type.  . Bats select warm maternity roosts because generating body heat is metabolically expensive.  The females can utilize their energy to grow their fetus, rebuild fat and produce milk, rather than to maintain their body temperatures.  Pups are born virtually furless and need assistance with staying warm, so through the warm roost temperatures and the huddling of bats in the maternity roost, there are great benefits to the mothers and the pups.  Most bat species in the PNW only have 1 pup per year, which is helpless for many weeks and can’t fly for the first month of life.  They are completely dependent upon their mother for milk, and protection from disturbance and predators through mom having selected a good maternity roost.  Once they can fly, mom presumably teaches them how and where to search for food and how to use their echolocation skills.  Only one maternity cave is known in Mount St. Helens area leading experts to believe they are rare and of great importance to survival of the species.  A couple additional maternity roosts in caves were known to managers, but have been abandoned by bats due to disturbance by humans over the past century.  A single disturbance of a maternity colony can cause abandonment of the site within 24 hours by the mothers. This will result in death of the pups and loss of one year’s reproduction. If you see or suspect bats are using a cave as a maternity roost, leave the cave immediately and quietly, and then report what you have found to the appropriate managing authorities.  Please have discussions with the managers prior to additional entries to determine the best dates of visitation and avoidance.

Bats are extremely sensitive to disturbance while hibernating.  They need to lower their body temperatures and respiration rates, and scale down their immune systems when they are hibernating to conserve energy.  They have about “a pat of butter’s worth” of fat to live off of all winter long, and each time they arouse, they use up a large percent of that fat reserve.  It may take a bat as much as 30 minutes to raise its metabolism enough to be able to move around or fly. This slow reaction time has lead many cavers to believe they have not disturbed bats when in fact they have! Bats are not thought to be sleeping while in hibernation, and actually must arouse every couple of weeks to turn on their immune system, eliminate body wastes and perform other critical body functions.  There is evidence that they “sleep” once they arouse from hibernation!  Hibernation (also known as a deep state of torpor) is probably better described as a state of quasi-suspended animation.  When in this state they remain alert to possible danger. If a passing caver is heard or flashes a light in the direction of hibernating bats, the bats go into what can only be described as “slow panic.” They will burn part of their winter fat to come out of hibernation and move to a “safer” location. Unfortunately, the “safer” location can actually be more dangerous because of potential freezing or excessive warmth (bats need a very specific range of temperature and humidity to survive the winter). After several disturbances, so much fat may be used up that a bat will starve before the spring when insects are again available for food. If you encounter bats in a cave during the winter, leave the cave immediately. Bats only use the cave for hibernation part of the year (generally November 1-May 1 in the PNW), so you can postpone your trip until the bats leave.  Bats may also use caves as night roosts during spring through autumn, as swarming sites where they meet with other bats to mate in the autumn, or as temporary roosts along their migration route during autumn and spring.  Males and non-reproductive females which not form maternity roosts like pregnant females in the summer use undisturbed caves during spring, summer and autumn as well.

Historically, the Saint Helens caves are known to have sheltered six species of bats. Myotis evotis (western long-eared myotis), M. lucifugus (little brown bat), M. volans (long-legged bat), M.yumanensis (Yuma myotis), Eptesicus fuscus (big brown bat), and Corynorhinus townsendii (Townsend’s big-eared bat). All of these species have been found using trees as roosts during summer months as well as using caves.  Historically, they may have used large snags with large decayed cavities for roosts, but large trees and snags are scarce in this century due to former timber harvesting practices.  Unfortunately, many factors have led to population declines for bat species, including: historic timber harvesting practices; agricultural practices; the draining of wetlands; the conversion of habitat from natural to agriculture, urban and suburban areas; the disturbance or exclusion from roosts and hibernacula; and the negative myths surrounding bats.  When it comes to bats and caves, visitors to the caves should treat all bats the same, by leaving them alone and undisturbed.  Letting land managers know they are there is helpful for their protection as well.

TOWNSEND’S BIG-EARED BAT (Plecotus townsendii)

Townsend’s big-eared bat is listed as a species of special concern throughout all of the western states, with legal status varying slightly between states.  The species is of concern due to historic surveys indicating population declines were taking place.  This species is generally associated with older forested habitat and uses caves, mines and tree snags as roosts.  It may also use human structures that are undisturbed as roosts on occasion (abandoned cabins or barns).      Reasons for their declines likely included the harvesting of old growth forests and larger diameter trees, low snag recruitment or maintenance, cave roost and hibernacula disturbance, habitat conversion to urban and suburban areas, and possibly pesticides that kill their primary prey species (moths).    It appears that reducing disturbance at cave hibernacula and the one remaining maternity roost cave has led to small increases in their colonies over the past decade!

Quiet passage of a just one caver can be enough to cause arousal of the bats from hibernation during the winter. This requires burning fat reserves, which can lead to starvation or the loss of the fetus for a pregnant female. Any unnecessary burning of fat reserves may make the difference between death and survival.

Unfortunately this species appears to be sensitive during the summer months if the maternity colony is disturbed. Dead young were noted in Mt. Adams area caves following disturbance by cavers during the 1972 National Speleological Society Convention. To protect these bats in the Mt. St. Helens area, all cavers are asked to stay out of Bat Cave, Spider Cave, Dollar and a Dime Cave, Beaver Cave, and the upper end of Ole’s Cave during the period from October to May. Utterstrom’s and Powerline caves should not be visited (even just stopping at the entrance can be detrimental) from April until October.

Cave Closure List

 

(Reprinted from the Willamette Valley Grotto Website) – Updated November 2000

 

SOUTHWEST WASHINGTON CAVES THAT HAVE BATS AND OTHER SENSITIVE CAVE FAUNA

Mark Perkins, a cave biologist from Oregon, has studied the bats and other creatures in the lava tube caves of both Washington and Oregon. As a result of his research, he drew up a list of caves which have particularly sensitive bat colonies and other cave fauna and therefore should be avoided at certain times of the year to protect them. The following is an old list I had from him of some of the sensitive caves near Mt. St. Helens and Mt. Adams so you can plan your trips accordingly. Since bats tend to move around due to disturbance by humans and other factors, you may find other caves with several bats in them.

If you spot several individual bats of the same or different species in a cave not listed below, please report it to the Washington Department of Fish and Wildlife Diversity Division (Gerry Hayes 360-902-2371) or the USFS land manager, and notify the rest of us through the regional list server so, we can add information to this list..

Caves to Avoid All Year

(Bat Nursery Sites from March-August/Winter Hibernation Sites October-March)

Mt. St. Helens

• Power Line Cave (gated)

Mt. Adams/Trout Lake

• Christmas Tree Cave (gated)
• Poacher’s Cave
• Big Cave — Note: Don’t confuse with Big Trench Cave, which is quite a ways east of Big Cave. But, Big Trench Cave is a bat hibernaculum and should be avoided from October-March but is ok to visit during the summer months. (See below.)

Wind River Ranger District between St. Helens and Trout Lake

• Curly Creek Cave

Caves to Avoid in Winter

These caves should be avoided in winter between November 1  and May 1. Actual closure dates vary according to agency jurisdiction and weather.

Some, such as Pictograph, are closed from October 15 through May 1. By visiting the caves listed below only during the summer months you will be helping protect Townsend’s big-eared bats and other bat species.
 Cave and wildlife conservation is the first priority so just go ahead and make up some save the date cards and plan to visit these great caves outside of the closed dates. In the mean time, other caves are available for exploration until these open.

Charcoal Cave in Central Oregon is closed from April 15 to September 1 to protect the bat maternity colony.

Mt. St. Helens Cave Area

• Bat
• Beaver
• Blue Ribbon
• Breakdown Cave (per Kim Luper)
• Dollar and a Dime
• Little People’s
• Ole’s
• Prince Albert
• Spider

Mt. Adams Cave Area

• Back Bone
• Big Trench
• COG
• David’s Den Annex
• Goose
• Ice Rink
• Ice Rink Annex
• Jug (east tube)
• Madison’s Fence
• Poacher’s
• Red Cave System
• Christmas Tree

Wind River, Falls Creek caves.All caves in the falls creek area should be avoided in winter.

Saddle Butte Cave Area

• Burns
• Coyote Trap
• Owyhee
• Rattlesnake #2
• Tire Tube
• Kitty Pooh II
• Kitty Pooh Extension
• Raven Pit

Central Oregon Cave Area

• Bat
• Bat Crack
• Charlie the Cave (lower passage)
• Deg
• Lava River
• Lee’s
• Lower QMC
• Officer’s
• Pictograph
• Skylight Cave #1
• Stookey Ranch
• Wind

Western Oregon Cave Area

• Scott Mtn. Talus
• Blue River
• Mowich
• Grant’s Park
• Fish Creek

Bat Natural History in the Pacific Northwest

Ella Rowan, MS

Wildlife Biologist

Townsend’s Big-eared Bat (Corynorhinus townsendii)

Bats are some of the most fascinating mammals globally and have developed some of the most extreme adaptations.  Unusual adaptations such as echolocation, flight, torpor, hibernation, and delayed pregnancy are a few strategies that have allowed bats to master their niches across the world and especially in the more temperate regions.  There are over 1,100 species of bats worldwide, and they account for about 1 out of every 4 mammal species.  Bats comprise the Order Chiroptera, which is split into two suborders – Megachiroptera and Microchiroptera.  Megachiropterans are “fruit bats”, and they are all found near, or south of the equator in Africa, Asia and Australia.  Microchiropterans are found on all continents except Antarctica, and at all but the most extreme latitudes.  Most microchiropterans consume insects and play a huge role in maintaining insect populations under control, but some also consume fruit, nectar, pollen, and small animals.  There are only 3 species of vampire bats worldwide that consume blood, all of which live in Central and South America.  The United States is home to over 45 species of bats, and almost all of them prey upon insects.  Only a few in the extreme south consume fruit or nectar.  Nineteen species of bats are known to inhabit the Pacific Northwest (Washington, Oregon, and Idaho), but others may make rare visits.

Bats have adapted to certain habitats and have specific foods they forage upon…they are very diverse!  In the Pacific Northwest, species may forage within intact forests or forest-edge habitat, open areas or shrub-steppe habitat, over bodies of water, or along riparian areas.  Some forage on ground insects, some are fast fliers high above the canopy or shrub-steppe, some are slow fliers that are more maneuverable and can glean insects off of plants in tight spaces.  Each species has physical adaptations such as the shape of their wings and ears, and the frequency of their echolocation calls which have developed to master catching insect prey in a particular habitat type or manner.

Mating and reproductive strategies are very unusual for our northwestern species, and they defy typical rules found in mammals in a few ways.  First, most small mammals reproduce their first year and have numerous large litters.  Bats, however, usually do not reproduce until they’re at least one year old, and most species only have 1 pup per year.  Second, many species mate in the autumn or winter and the females store the sperm until the spring.  Some species of bats can even allow the egg to become fertilized in the autumn and then delay its implantation in the uterine wall until the spring.  Gestation lasts 2-3 months, with the pups being born during June or July.  The pups are nursed for 1-2 months and they can usually fly within a month or two.  Offspring will follow their mothers for a couple weeks to learn to forage & probably learn about roost sites and social behaviors.

Another reason bats are unusual is that they can live an incredibly long time for animals their size.  One species of Myotis found in Siberia has an individual that was at least 41 years old the last time it was captured.  That population hibernates up to 9 months a year, which may be the key to longevity.

Roosting behavior is a complex subject for bats, with few species fitting into neat categories.  Trees, caves, mines and other structures provide valuable roosting and hibernating sites for many of our North American species.  Some species are solitary, some are semi-social, and some are communal.  Most species can change their habits throughout the year in response to maternity season, hibernation season, or mating season.  Some of the more solitary species will form maternity colonies for short durations, but then return to solitary roosting after the pups are weaned.  Generally, only females and their pups are found in maternity colonies.  Roost sites are critical for bats to exist, and disturbance may lead to the death of these animals through abandonment of pups or the loss of an optimal location.

     Hibernation is an extremely important and dangerous time for bats, with disturbance of any sort potentially killing them.  Most bats in the northern US hibernate or have to migrate to where the food (insects) is during winter.  Usually they even have to migrate to where they can hibernate. They have very specific microclimate requirements for hibernation, so they often have to travel long distances to find ideal caves, mines, trees, or other structures.  Hibernation can last 5-8 months, depending on species and latitude.  If caves are used, they often need to have temperatures between 35-49º F (2 – 9º C) and high humidity with minimal wind current. Exact requirements are species-specific and can vary greatly.  Some species migrate north, or up in elevation in the winter to find just such caves.  It is estimated that less than 5% of caves are suitable for bat hibernation, due to these specific microclimate requirements.

Scientists are constantly finding new and unusual answers to questions regarding bat hibernation, such as indications that bats do not sleep while they are hibernating.  All hibernating species slow their metabolism drastically and alter many of their physiological processes.  Their heart rates drop from up to 400 beats per minute down to around 25 bpm, and their respirations drop to as little as 2 per hour.  Their temperature drops to within a few degrees of the ambient cave temperature.  By slowing their metabolisms and remaining cold, they can live off their fat reserves for many months until their insect prey returns in the springtime.  Bats must arouse every 2-3 weeks to drink and urinate, and they often just lap condensation off of themselves.  When they arouse, they may also go to sleep for a period of time since they do not appear to truly sleep during hibernation.

Bats require sufficient fat reserves to sustain them through their long winter of hibernation, but can’t gain too much fat to fly.  If they are disturbed by noise, light, predators, diseases, climate changes or other factors, they will arouse to try to protect themselves.  Arousing requires re-warming their body temperatures by burning fat, and can take as long as a few hours to accomplish.  They enter hibernation with enough fat to arouse every few weeks to urinate, defecate, sleep, and perform physiological processes, but any additional unplanned arousals will cause them to use up their fat and they will die of starvation before spring and their insect prey return.  It takes a bat as much as 5 days worth of fat (energy) to arouse (Speakman et al 1991).  Even non-tactile disturbances cause arousals that will last for up to 9 or more hours (Thomas 1995).

The migration and hibernation habits of bat species in the Pacific Northwest are not well known.  Townsend’s big-eared bats and numerous Myotis species hibernate in caves and occasionally mines, but appropriate caves are very difficult to find due to the specific microclimates required.  Townsend’s big-eared bats are a species of special concern in the United States due to dramatic declines in their populations.  They are even more sensitive to disturbance than most other species.

Two diseases that people can contract from bats native to the United States include histoplasmosis and rabies.  Histoplasmosis is more prevalent in the southern and southeastern US and is caused by a fungus (Histoplasma capsulatum) that can grow in dried bird and bat feces.  If people stir up the dried feces when sweeping attics or sheds, they can breathe in the spores and develop symptoms similar to the flu with respiratory involvement.  This is rarely lethal, but one must visit a doctor if symptoms arise.  Rabies is a lethal virus that affects the nervous system and it can be contracted by any mammal species.  The route of transmission is generally through a bite wound, where an infected animals’ virus-laden saliva can enter the bloodstream of another mammal.  It is generally only carried by a few carnivore species (raccoons, skunks, fox, coyotes), but can also be carried by bats.  It is estimated that less than 1 out of 1,000 bats has rabies (varies by species), but precautions must be taken at all times when handling bats due to the lethal nature of the disease.

A new disease known as White-nose Syndrome (WNS) has killed over six million bats in the eastern and midwestern United States and Canada since 2006, although there is no indication that WNS affects humans or other animal species.  White-nose Syndrome was first detected in bats at Howe Cave in New York in February of 2006, but has spread as far west as Missouri, and as far north as Ontario , Canada (as of April 2013).  Bats have been found with the associated fungus as far west as Oklahoma as of 2010, but none have fallen victim to WNS as of yet.  WNS is named after the whitish fuzzy fungus (Geomyces destructans; Gd) that tends to grow on bat’s muzzles, wings and ears when they are overwhelmed with the fungus during winter hibernation.  The fungus may be present, but not obvious until it has grown substantially.  Nine different species of bats have been found with this fungus on them thus far, but it appears to be only affecting certain cave-hibernating species.  Extensive research has eliminated all known viruses and bacteria as the primary factors related to the deaths of these bats, with the fungus being the causative factor.  Geomyces species are cold-loving fungi, but G. destructans can survive temperatures up to 100°F (38°C) for up to 8 days, and up to 86°F (30°C) for up to 15 days (W. Stone, NYSDEC, documented in USFWS June 2009 Disinfection Protocol).  Additionally, dryer heat of 120°F (49°C) increases spore germination and does not kill the fungus (H. Barton, Northern Kentucky University, documented in USFWS June 2009 Disinfection Protocol).  Fungal conidia (spores or “seeds”) typically are able to live for years at temperature extremes, are very difficult to kill and are resistant to desiccation.  Fungi typically do not kill animals, but bats are unusual in that they slow down their metabolisms, physiological functions and immune systems while hibernating.  They are possibly not able to fight the fungus, which invades their tissues.  Bats infected with WNS tend to arouse frequently and burn up their fat reserves, possibly in attempt to groom the fungus off themselves or start up their immune systems.  They are found flying outdoors in late winter while snow is still on the ground and there are freezing temperatures….times of year when no insect prey are available to consume.  The bats are usually emaciated and found dead outside their hibernacula.

There are still many unknowns regarding this syndrome, but important research findings relative to the role humans may play in transferring this fungus to new locations include:

The genetically identical fungus (G. destructans) has been found on numerous species of bats in European countries.  The European bats are not dying in large numbers like those in North America, which is indicative of a new pathogen being brought into a naïve population.  This fungus may have been brought to Howe Cave in the United States on a human that had recently been in a European cave.  Research is addressing this question. (Wibbelt 2010, Puechmaille 2010)

Bats can contract the fungus from the environment.  A study brought 79 uninfected bats from Wisconsin to 2 sealed eastern mines where infected bats had died from WNS or been excluded.  All of the Wisconsin bats died or became sick, with indications they had contracted WNS. (Hicks et al 2010)

Spores of the fungus G. destructans can attach to clothing and gear, and can be airborne in infected caves.  Swabs of gear and clothing, as well as the rinse water after cleaning, were found positive for conidia.  Air samples and guano samples in infected caves during hibernation season tested positive for conidia.  (Okoniewski et al 2010).  Finding the conidia on gear after leaving infected caves indicates it can be carried to new locations by humans.

     Bats are estimated to use less than 5% of available caves to hibernate, because they require strict microclimate conditions that very few caves possess.  Eastern bats may fly from 5 or more states to hibernate in one cave far away.  Northwestern bats may fly hundreds of miles across state lines to find ideal places to over-winter.   If we continue to lose as much as 100% of bats at each of these caves, we are looking at significant population declines and potential extinctions of species.  Bats usually only have one pup per year, so it would take a very long time to rebuild their populations.  White-nosed syndrome has advanced at a rapid pace across the eastern US.  The causative fungus is now found in Myotis velifer, a species whose range extends as far west as California.  We need to do all we can to prevent Geomyces destructans  from infecting new caves and mines, as well as new species.  It may be very easy for humans to inadvertently introduce the fungus to the northwestern US and elsewhere globally.

Don’t disturb bat colonies during the summer months.

¨       Please follow the decontamination protocols established by the US Fish and Wildlife Service to clean your clothing and caving gear after each cave you visit.  Check for updates to the protocol often.

¨       Please do not use clothing, boots, or any gear in states that are free from WNS, if they have been used in states or provinces where WNS or G. destuctans has been found.

¨       Please notify the US Fish and Wildlife Service and the state’s Department of Fish and Wildlife immediately if you see bats exhibiting any unusual fungal growth, or unusual behaviors (such as flying outside of hibernacula during winter months when there are freezing temperatures), or appear sick in some other way.

¨       Please notify your states Department of Fish and Wildlife any time you discover hibernacula or other large roosts (more than 10 bats).  Washington Department of Fish and Wildlife (WDFW) hopes to upload a Bat Observation Form available on the Cascade Grotto website and the WDFW website.

Great links for more information:

Bat Conservation International

http://www.batcon.org/

US Fish and Wildlife Service

Living with wildlife Bats .

http://www.whitenosesyndrome.org/

Western Bat Working Group

http://www.wbwg.org/

References

Speakman, J.R., Webb, P.I. and P.A. Racey.  1991.  Effects of Disturbance on the Energy Expenditures of Hibernating Bats.  J. of Applied Ecology, 28 (3), pp 1087-1104.

Thomas, D.W.  1995.  Hibernating Bats are Sensitive to Nontactile Human Disturbance.  J. of Mammology, 76(3), pp 940-946.

Research presented during the White-nose Syndrome Symposium May 25-27, 2010, in Pittsburgh, PA:

Investigations into the Environmental Transmission of WNS to Hibernating Myotis lucifugus

Alan Hicks, Joseph Okoniewski, Scott Darling, David Redell, Ryan Smith, Ryan Von Linden, Kate Langwig, Thomas Ingersol, Joel Flewelling and Carol Meteyer

Geomyces destructans in Europe

Gudrun Wibbelt

The Potential Threat of White-nose Syndrome to European Bats: An Action Plan

Sebastien Peuchmaille on the behalf of the White-Nose Syndrome Consortium

Detection of the Conidia of Geomyces destructans in Northeast Hibernacula, at Maternal Colonies, and on Gear – Some Findings Based on Microscopy and Culture

Joseph Okoniewski, John Haines, Alan Hicks, Kate Langwig, Ryan Von Linden and Christopher Dobony

 

How to build a bat House