Prime Transmitters of Rabies
Aggressive and Dangerous Animals
Blood Sucking Creatures
Pollinators and Seed Dispersers
Renewers of Rainforests
Providers of Habitats for Other Species and Lifegivers to Deserts
Essential for Commercially Important Plants
Anti-Coagulant for Heart Patients
Disturbance and Vandalism
Destruction of Natural Habitats and Foraging Areas
Closing Cave and Mine Entrances
Installation of Improper Bat Gates and Fences
Impoundment of Waterways
Flooding of Caves
Cave Collapse and Cave Entrance Closure
Species and Country Specific
Establishing Acquisition, Protection, & Management Agreements of Caves
Installation of Bat-Friendly Gates or Fences
Erecting Warning Signs
Meager Census of Population Trends
Inadequate Monitoring of Roost Sites
Bat Conservation International
North American Bats and Mines Project
Texas Bats and Bridges Project
Protection of Foraging Habitat
Monitoring of Roost Sites and Foraging Habitats
Increased Funding for Research
Develop and Apply an Ecosystem Approach
Continue Socio-Economic Valuation Research
Although traditionally not viewed as a charismatic species, bats are an invaluable natural resource. Except for the most extreme desert and polar regions, bats live in almost every habitat worldwide, just as they have for more than 50 million years. Nearly 1,000 different kinds of bats are known today, fully one-quarter of known mammal species. Despite their diversity, the world's only flying mammals remain among the least understood of animals.
Centuries of myth and superstition have made bats among the world's least appreciated wildlife. Decades of unwarranted human fear, misinformation, and persecution of bats at their roosts have pressed populations into severe decline nearly everywhere in the world and endangered many species. While for some species of bats it may already be too late, sound management practices can potentially save others. Countering human misperceptions and destructive actions as well as implementing an ecosystem level approach for their habitat protection are vital goals for the management and sustainability of these species.
This case study provides an illustration of how management initiatives can determine whether a species survives, or not. The first section is an exploration of why bats have been among the most intensely feared and relentlessly persecuted animals on earth. The next section discusses the various ecological and economic roles that bats play. The paper then addresses the susceptibility of hibernating bats and maternity colonies, as well as the importance of roosting sites to the survival of bats. The next two sections discuss the present status of bat populations and major factors influencing their decline. The final section presents current management initiatives and describes successful and unsuccessful management efforts. Here, the primary attention focuses on two endangered U.S. species and management efforts conducted by the world's largest bat conservation organization. The paper concludes by recommending management efforts and conservation measures that can help assure sustainable bat populations.
One of the most widespread misconceptions is that bats commonly carry diseases, especially rabies. Of the 30,000 humans that die from rabies each year worldwide, ninety-nine percent of these cases are due to contact with rabid dogs (Brass, 1994). Only a fraction of one percent of bats have rabies (Mazzotti and Brandt, 1990), and infected bats very seldom become aggressive as other mammals do. Up to now, only twenty-four people have contracted rabies from bat bites in the United States, largely as a result of picking up a sick bat (Gannon, 1992). One is more likely to die from food poisoning contracted at a church picnic than from getting rabies from a bat.
Another misconception is that bats are aggressive and dangerous: many photographs shown to the public have portrayed them as such. But, if not provoked into defensive behavior, bats are very gentle creatures. Correcting such images will become an influential force in their protection and conservation.
Movies have also harmed the public image of bats by portraying vampire bats as blood thirsty, ravenously sucking the blood from people's necks. People are led to believe that all bats, not only vampire bats, behave in such a way. However, this is far from the truth. Of all the bats around the world, approximately seventy percent are insectivorous, nearly thirty percent eat nectar or fruit, ten species are carnivorous, two species are fish-eaters, and only three species - the common vampire, the white-winged vampire, and the hairy-legged vampire - feed on blood (Altringham, 1996).
The three sanguivorous bats all live in Latin America. These species do not suck the blood from their prey, as commonly portrayed. Instead, they lap the blood from small incisions made with their teeth, with the prey hardly ever noticing the activity. While the hairy-legged vampire has a strong preference for bird blood, the common vampire has a preference for large mammals. The introduction of domestic horses, cattle, and pigs into the traditional vampires' foraging areas has been a contributing factor for the common vampire's population increase over the last 300 years. In addition, the booming human population is at times an occasional food source. But, as with other prey, vampire bats do not kill or transmit diseases to humans when they feed. Nevertheless, the instilled but unwarranted fear, along with the perception that bats are pests, killers of livestock, and carriers of rabies have contributed to the extirpation of bats of all types in those areas.
Besides the moral, ethical, and aesthetic justification for the conservation of bats, these species are ecologically and economically important. They are among nature's most beneficial animals, and undoubtedly, many are keystone species (BCI, 1989). Without them, thousands of other animal and plant species could die out, threatening entire ecosystems from rainforests to deserts.
Bats play key ecological roles as primary predators and are by far the most important natural controllers of night-flying insects (Bat Conservation International, 1989). While many of the insects consumed are serious crop pests, including kinds that cost American farmers and foresters billions of dollars annually (BCI, n.d., www address), other insects are responsible for spreading disease to humans and livestock.
A single bat can eat thousands of insects each night (ranging from 1,000 to 3,000), and may consume up to 50% their own body weight in insects in a single evening (Australian Nature Conservation Agency, n.d.) As an illustration, a little brown bat, one of North America's most abundant species, is capable of capturing 600 mosquitoes in just one hour. In addition, one colony of 20 million Mexican free-tailed bats in central Texas consumes nearly a half million pounds of insects each night (BCI, 1989). A colony of 150 large brown bats can eat approximately 38,000 cucumber beetles in a single summer. The corn worms which are produced by these beetles can, in turn, potentially destroy corn, spinach, and vine plants, costing U.S. farmers up to $1 billion annually in lost productivity (Environment, 1994).
By controlling huge numbers of night-flying insects, bats unequivocally form an integral link in ensuring environmental health. When bat populations are destroyed, insect pests, unchecked by their natural predators, multiply at an alarming rate. The loss of insectivorous bats leaves humans increasingly dependent on pesticides, which already threaten our environmental and personal health. With over 850 million pounds of pesticides applied to crops in the United States alone, not only is the groundwater increasingly contaminated, but runoff is further damaging wildlife habitat.
Not only do bats participate in public entomological services, but, as elaborated below, also play key roles as pollinators and seed dispersers.
Bats are well-equipped to disperse tree seeds far and wide through a forest (Allen, 1996). Throughout tropical regions, fruit and nectar-eating bats are vital to the survival of rainforests, which in turn play an essential role in the stability of world climates. Preservation of these rainforests is also critical as they contain the Earth's richest biological diversity; more than 90% of all terrestrial plant and animal species are found there (Wilson, 1992).
Without bats to pollinate flowers or disperse seeds, the diversity of rainforest animals and plants would be greatly reduced, thereby threatening delicate ecological balances with unknown consequences. In West Africa, for example, bats carry 90-98% of the seeds of "pioneer plants" that are essential for initiating forest regrowth on cleared land. These hardy trees and shrubs, which grow rapidly, soon attract other mammals and birds that, in turn, bring seeds of different plants. Such cycle of rainforest regeneration might never take place without bats (BCI, 1989).
Bats also play key roles in other tropical rainforests from Latin America to Asia to Australia. After Hurricane Hugo devastated a Puerto Rican rainforest in 1989, it was found that red fig-eating bats (Stenoderma rufum) played the largest role in helping that area in the Luquillo forest to recover after the hurricane (Miller, 1994). It is believed that this type of bat is the only agent for dispersing the seeds of at least one of the dominant species of tree in that forest, the Manilkara bidentata. Without those trees present, it is doubtful that the forest could return to its previous state.
The giant baobab on the savannas of East Africa is known as the "Tree of Life" because so many other plants and animals depend on it for their survival. That tree itself depends on bats for its survival. Because its flowers only open at night, they are specifically adapted to be pollinated by bats. This critically important tree could die out without bats, triggering a chain of linked extinctions and threatening plant and animal life throughout the region.
In the Sonoran Desert of the southwestern United States and Mexico, long-nosed bats play a similarly vital role in the lives of several species of agaves (century plants) and cardon, the world's largest cactus. As with Africa's baobab tree, the giant cacti provide food and shelter for innumerable creatures (Fleming, 1994). Not until recently was it discovered that the long-nosed bat is their prime pollinator and seed disperser, but also that this type of bat is now endangered. Their decline threatens entire southwestern desert ecosystems, potentially signifying the end of plants and the wildlife that rely on them.
Many of the world's most economically important plants rely on bats for pollination. Some of these crops are valued in the millions of dollars each year and are crucial to the economies of cash-poor developing countries. In the Old World tropics alone, over 300 plant species rely on bats for seed dispersal and pollination, of which more than 450 commercial products come from these plants (BCI, 1989). In Africa, rapidly declining flying foxes are the only known seed dispersers for the iroko tree whose timber is worth millions of dollars annually. The durian fruit of Southeast Asia adds $120 million to local economies. Furthermore, many of our cultivated crop plants still rely on bats for their survival in the wild. These include fruits such as bananas, avocados, dates, figs, peaches, plantain, breadfruit, and mangoes. Even though most of these plants are now commercially cultivated, wild stocks remain essential as they are the only source of diverse genetic material for development of disease-resistant strains and for producing new, more productive plants in the future.
Although guano may be viewed as a nuisance for some, especially in urban settings, it is actually an excellent fertilizer. In some developing countries guano is harvested since it provides an inexpensive method to nourish the soil. A monastery in Southeast Asia makes approximately $100,000 per year by selling harvested guano to local farmers (Documentary, 1992).
Not only is guano a rich fertilizer for crops and other plants, but it also supports whole ecosystems of organisms which may be commercially important for humans. In addition, recent research indicates that the different bacteria contained in guano may actually provide important medicinal materials and prove to be efficient for breaking down industrial waste, preventing disease in animals, and provide for improvements in antibiotics (Documentary, 1992).
Saliva from vampire bats has been shown to be an excellent anti-coagulant. It has been shown to open clogged arteries twice as fast as standard pharmaceutical remedies, while restricting its activity to the area of the clot (The Futurist, 1993). In essence, this may become a critical product for helping to prevent heart attacks in patients suffering from cardiac disease.
Torpor, used on a daily basis for energy budgeting, or for long periods of hibernation, is an important and integral component of the life history strategy of bats in both temperate and tropical regions. While daily torpor is used to a limited extent by many tropical insectivorous bats whose food supply is unreliable and often low in energy (McNab, 1982), full hibernation is vital for bats living in regions with severe winter conditions.
The appropriate hibernacula and suitable hibernating conditions are very critical elements for the continued existence of bats. Because bats are endotherms like most mammals, they maintain high body temperatures by metabolizing their food to generate heat internally. This requires high metabolic rates as well as high food intakes (Altringham, 1996). Since foods consumed by bats are seasonal in some regions, bats hibernate to cope with this shortage of food. By the time winter begins, bats have stored up to 35% of their body weight as fat, and survive by slowly using up this body fat (Oliver, 1997).
Disturbing bats when they are in deep hibernation stages poses a serious threat to their survival since they have to use up stores of energy every time they are awakened. Each arousal can cause a bat to expend as much as 68 days of hibernation fat supply in a single disturbance (Thomas et al., 1990). In some species, stored fat reserves must last for at least 6-7 months (Tuttle, 1976). This is a critical factor for the management of bats.
In addition, species have different microclimatic requirements for successful hibernation. The success or failure of a bat to survive the winter is therefore also dependent to a large extent on finding the right hibernacula conditions.
Although most species of bats mate during the fall or early winter, fertilization does not take place until early spring, with birth occurring in late spring or summer. Because calcium demand on reproductive females is high but calcium availability in most diets is low, it is believed that this is a primary factor restricting the number of births per female per year (Barclay, 1995). Most bat species give birth to a single pup, a lower reproductive rate than any other small mammal. Also, some bat species are not capable of reproducing until they are 2 years old (Tuttle, 1976). Although bats can live longer than other mammals comparable in size, up to 30 years for some species (Altringhman, 1996), their low reproductive rates are definitely a prime management consideration, especially as entire colonies can be easily extirpated in short periods of time by human activities or natural disasters.
Just as with hibernating bats, disturbance in maternity colonies may have severe repercussions. Interference can lead to mass mortality as frightened females may drop their pup to flee from the intruder or cause them to abandon their young altogether.
V. IMPORTANCE OF ROOSTING SITES
Because bats spend most of their lives in their roosts, comprehension of their roosting ecology is fundamental to an understanding, and therefore management, of bats. Roosting habitats influence local and global distribution, densities, foraging and mating strategy, social structure and seasonal movements, and even the morphology and physiology of bats (Kunz, 1982). Bat roosting sites consist of caves, rock crevices, tree-bark cracks, foliage and other temporary roosts, and man-made roosts.
The most important survival benefits of a suitable roost include: protection from the weather; protection from predators; cheaper thermoregulation, such as energetic savings during hibernation; reduced commuting costs to foraging sites; improved mating opportunities; improved maternal care; and competition avoidance, since few other vertebrates make use of most bat roost sites.
VI. MAJOR FACTORS FOR DECLINE
Numerous factors have contributed to the decline of bat populations. The primary known causes are the direct and indirect actions of humans.
Disturbance and vandalism of roost caves are detrimental to the survival of bats. Whether disturbing bats is intentional or not, such as the case with recreational cavers and researchers, human activity causes bats to arouse from hibernation, thereby depleting their stored fat reserves, and endangering their lives. Additionally, there have been documented cases of females dropping their pup to the ground to flee from intruders or abandoning their young as a result of human disturbance.
Direct mortality due to human vandalism has led to very serious repercussions. As an illustration, an estimated 10,000 Indiana bats were killed in a cave located in a Kentucky state park by three juveniles who tore masses of bats from the ceiling and trampled and stoned them to death (Mohr, 1972.) Activities like this single act of vandalism can decimate thousands, or even millions, at a time, having significant impact on the survival of an entire species.
In addition, continued disturbance of roosting sites may cause bats to abandon that roost altogether. Contrary to popular belief, bats may have a difficult time finding alternative roosts that meet their requirements. While some have adapted to anthropogenic structures, such as mines and buildings, many others may be left homeless, and, therefore, unable to survive as they cannot find the appropriate hibernating or maternity roosting sites.
Destruction of natural habitats and foraging areas also are responsible for decimating entire colonies, especially if the bat population has strong site fidelity. In addition, some bats have highly specific roosting requirements in terms of temperature, proximity to foraging areas, and location and type of cave. For instance, it is believed that the endangered gray bat has the most narrowly restricted cave habitat requirements of any U.S. mammal (Hall and Wilson, 196; Barbour and Davis, 1969; Tuttle, 1976). Therefore, the unavailability of such roosting sites can decimate entire populations. Harvesting of roost trees also has been responsible for declining populations.
Bats are susceptible to killing by humans due to fear and ignorance. There are many documented cases of such occurrences, such as when the Texas Department of Transportation used blow torches to burn bats found in bridge crevices in 1992 in an attempt to eradicate the entire bat colony (BCI, 1994-95). Prior to 1960, half a million gray bats were killed with torches in 2 Tennessee summer caves by the cave owner and his assistant (Brady et al., 1982).
Many documented cases exist where caves and mines have been closed off intentionally. Such actions have resulted in either suffocation of bats or have forced bats to abandon their caves.
In the past few years, thousands of old mines have been closed due to human safety concerns. This has been detrimental to many bat populations. In North America, many of the largest bat populations now live in abandoned mines. They have come to utilize these roosts because their original homes in caves or tree hollows have been vandalized or destroyed (BCI, 1994-95). Abandoned mines now accommodate more than half of the 44 U.S. bat species, including many of the largest populations of endangered species. Mine closures place many North American bat populations at extreme risk. Evidence indicates that millions of bats have already been lost due to these closings.
Although there have been some benign efforts to keep people out of caves and mines by installing gates or fences, many of these have led to serious repercussions for bats. Erection of improper structures have been documented to actually exclude bats from their homes and have resulted in deaths due to changes in air flow and modification of climate inside the caves or mines (Richter et al, 1993). Exclusion of Indiana bats from caves and changes in air flow had been the major cause of population death in Kentucky roosts since the 1950s, resulting in an estimated 200,000 deaths at 3 caves (Clawson, et al., 1996). Additionally, modifications that affect bat movements inside or outside caves or mines has facilitated predation of bats.
While a gate or fence may contain the appropriate specifications for a hibernacula, the same type may be inadequate for maternity colonies. Pregnant female gray bats or grey bat females with young are incapable of flying though a full gate or fence (Brady, 1982). In such instances, only half-gates would be suitable.
Deforestation of areas near roost entrances and between foraging areas have affected populations detrimentally. During evening emergence, bats may fly in the protection of forest canopy enroute to foraging areas. If forests are unavailable, predators may take advantage of the unprotected bats. Forests are also used by some young bats for resting places and in between foraging, as they are very slow and clumsy fliers during their first week of flight.
Caves near rivers are very vulnerable to inundation by man-made impoundments. Such actions have resulted in the extirpation of thousands of bats. Even if bats have escaped that initial destruction of their roost, survival of displaced populations are questionable due to some bat population's strong site attachment and narrow ecological requirements, such as those of the gray bat.
Pesticides have been implicated in the declines of several insectivorous bats in North America (Mohr, 1972; Reidinger, 1976; Clark and Prouty, 1976; Geluso et al., 1976). Samples of guano have indicated potentially dangerous levels in some species.
A possible cause of decline in some species may involve chemical pollution over areas which bats forage. The gray bat, for instance, forages primarily over rivers, streams, and reservoirs. The three types of insects which constitute its main food source - mayflies, stoneflies, and caddisflies - are quite sensitive to aquatic pollution (Brady, 1982). Insect population decreases are directly correlated with the survival of gray bats.
In some developing countries, bats are considered a delicacy and an aphrodisiac. Consequently, human consumption of bats has already caused extirpation of some species.
Although human activities are the main factor for declining bat populations worldwide, there are a number of natural hazards which have also contributed to the loss of bat populations.
Cave flooding resulting in drowning of bats in hibernacula is by far the most important natural calamity faced by some bats. An estimated 300,000 Indiana bats drowned as a result of this in the 1960's (Hall, 1962).
Cave-ins or gradual fill-in of sinkhole entrances have rendered some cave entrances or important passages too small for a large bat colony to pass through without greatly increasing the danger of predation. This has resulted in abandonment of caves or in the entombment of colonies.
Occasions have arisen where some bats are frozen to death during severe winters. Species who hibernate in cool portions of caves or mines that are near entrances or where cold air is trapped are particularly susceptible (Richter et al., 1993).
Bats around the world are in severe decline. In the United States, for instance, nearly 40% of the 43 bat species are endangered or threatened (Environment, 1994; New Scientist, 1993). At the turn of the century, gray bats were among the most abundant animals in the U.S.; now they are on the endangered species list. Indiana bats, also endangered, declined by 55% in less than 10 years (Clawson, 1996 and BCI, 1989). In the early 1960's, Eagle Creek Cave in Arizona housed the world's largest known bat colony, consisting of approximately 30 million Mexican free-tailed bats. But, in only 6 years, they declined 99.9%.
The same tragic losses are evident elsewhere. In Australia, mass hunts have killed thousands of flying foxes at a single event, even though many of Australia's most economically important timber trees rely heavily on bats for pollination or seed dispersal. Flying fox populations are also in jeopardy throughout Southeast Asia and the Pacific and Indian Ocean Islands. On Guam, where bats are considered a delicacy, one of the island's two flying fox species recently became extinct without even being listed as endangered.
Also in Southeast Asia, Dawn bats, the primary pollinators of the $120 million durian crop, have been declining rapidly from loss of cave roosts and uncontrolled harvest for human food. In Latin America, the proliferation of vampire bats contributed to the indiscriminate killing of all bat species by poorly trained government agencies and local farmers who are unaware that the majority of the other 270 species are highly beneficial. In Europe, bats that were common only twenty years ago are now endangered.
This list of declining bat populations is by no means all- inclusive. In several places, once vast populations now survive as mere remnants. Many of the bat species necessary in large numbers to maintain the balance of nature are, instead, at such low population levels that they are almost ecologically irrelevant. While for some bat species it may be too late, for others immediate protective action may save them from extinction.
The current management of bats is species and country specific. There are no set standardized management techniques shared by nations worldwide. Management depends on many factors, such as whether a particular bat species is endangered, whether the species has received any attention due to circumstances jeopardizing its survival, availability of funding, and whether people's misconceptions and fears about bats have been allayed.
Although many management initiatives have come about haphazardly, all efforts are essential for the sustainability of bat populations.
Acquisition of roosting sites, both hibernacula and summer caves, has been a primary management objective, especially for endangered North American bat species. In addition, protection by Federal, state, or private organizations or implementation of management agreements with private landowners has been another primary goal for the protection and conservation of bats in the United States. In other parts of the world, some type of protective measure for roosting sites is also attempted. For instance, in the United Kingdom, all bat species and roosts are protected by the Wildlife and Countryside Act (Jones, 1995).
In order to ensure that hibernacula and summer roosting caves or mines are not disturbed or vandalized by humans, efforts are underway to install gates and fences which will not impede bats' entrance or exit out of roosting areas. While some initial structures were detrimental to the survival of bats, much research has been done since then in an effort to erect gates and fences with suitable specifications to meet both the needs of hibernacula and maternity colonies.
Warning signs have been posted in some caves to alert people that either hibernating or maternity colonies are present in the caves. Although the signs are an attempt to keep people out, in many instances this presents a challenge to some, and consequently proves to be counterproductive.
Census of some bat species has been done to monitor status of population trends. However, in many cases, this is not done on a regular basis due to lack of funds or personnel. Consistent surveying is further complicated as most bat species use several hibernacula and summer roosts. Even though species may exhibit site fidelity year after year, lack of funds and personnel make surveying of all known sites very difficult. Securing an accurate population count may also prove to be near impossible if all sites are not known or very difficult to locate. Such is the case with Indiana bats, who tend to disperse and form very small colonies in the summer months, roosting under tree barks.
Because of the potentially lethal repercussions associated with disturbance of hibernating and maternity colonies, conducting a census is problematic. Additionally, obtaining population counts may vary depending on which methodology was used in a particular year and whether different individuals performed the counts. (Keith Hudson, 1997).
While some monitoring is performed at some of the roosting sites for some bat species, particularly the endangered populations in the U.S., it is by no means conducted on a regular basis. Inadequate funding and lack of personnel for such activities are the primary reasons. Also, many countries, because of the bad connotations they still associate with bats, are unwilling to spend their resources overseeing bat habitats.
Although research has been conducted on bat biology, much still needs to be learned. To date, this group remains one of the least understood of animals. In many occasions, while one aspect of its life history may be well understood, such as its winter habitat, other aspects, such as its summer or foraging requirements, may not have received adequate attention. To illustrate this, relatively little is known about the summer ecology of Indiana bats because they are very difficult to locate (Clawson et al., 1996). In the United Kingdom, basic biological foraging information is lacking for most species, and consequently, little attention has focused on the protection of feeding habitats (Jones et al., 1995).
While governments have typically lacked the necessary funding to sponsor adequate research, nonprofit organizations have tried to relieve this pressure. Bat Conservation International (BCI), the world's leading bat conservation organization, has sponsored various research projects worldwide since its inception in 1982. These have been critical in illustrating the ecological and economic importance of bats. Although scientific understanding is a major goal of BCI, it cannot possibly be the substitute for all other countries.
Available funding dictates many of the management initiatives that can be performed. Not only has insufficient funding been accountable for lack of research initiatives in many countries, but it has also played a role in inadequate censusing of bat populations and monitoring of roosting sites.
Educating the populace is an essential ingredient for lasting conservation progress. While governments have done relatively little, BCI has been proactive in this effort. As elaborated in the next section, a primary goal of BCI has been to educate people at all levels about the importance and benefits of bats and the need to protect them (BCI, 1989). Providing accurate information, citizen training programs, workable solutions to problems, and the instruction of educators and wildlife managers are all part of BCI's education program.
To illustrate the success of management initiatives, two U.S. endangered bat species will be discussed. While one is considered a success story in that the species has been recovering, the other one, thus far, is not. In addition, management efforts initiated by the world's largest bat conservation organization will be examined and an assessment made as to whether these have been successful in the conservation and sustainability of bat populations.
The endangered gray bat populations occupy a limited geographic range in limestone karst areas of the southeastern United States. Research shows that this particular species may be the most restricted to cave habitats of any U.S. mammal, requiring deep and vertical caves for hibernacula and very specific caves located within a certain distance from rivers or reservoirs during the summer (Brady et al., 1982). Fewer than 5% of available caves are suitable for occupation by gray bats due to highly restricted roost and habitat requirements.
By the time this species became Federally listed in the late 1970's, and the first Recovery Plan prepared by the U.S. Fish and Wildlife Service (FWS) in 1982, the total population of the nine major hibernacula was less than 1.6 million (Brady et al., 1982). Prior to major declines, individual hibernating populations contained anywhere from 100,000 to 1.5 million bats.
Since gray bats are cave-dwellers throughout the year, with highly specific roost and habitat requirements, original management objectives focused on the protection of caves utilized by the species, both hibernacula and maternity sites, to reduce or eliminate human disturbance. This made a critical difference in reversing the gray bat declining population due to its highly narrow habitat requirements. To date, many of the caves used by gray bats have been acquired by the Federal government, protected, or a management agreement has been established with the private landowner. Located in Alabama, Fern Cave and Blowing Wind Cave, the most important hibernacula and summer caves of gray bats, respectively, were purchased by the U.S. FWS.
Gating, fencing, and posting signs at roost sites to prevent human intrusion have also been instrumental in the stabilization and the increase of the gray bat populations (Currie, 1997 and Toops, 1995). This has included erecting one-half fences or gates at maternity colonies, versus the full-sized ones used at gray bat hibernacula (Currie, 1997). Encouraging progress has thus been made by implementing these original cave management objectives.
Even though not part of the initial management efforts, it is speculated that two other factors may have helped with the recovery of the gray bat. Although not documented, banning of DDT may have played a role in curbing the dwindling population (Currie, 1997). In addition, with the implementation of the Clean Water Act (CWA), more aquatic insects are now able to survive in streams (Patrick, 1992). Since the main feeding source of the gray bat consists of three aquatic insects who are in turn very susceptible to aquatic pollution, execution of the CWA may have indirectly contributed to their survival.
Officially listed as an endangered species in 1967, the Indiana bat, unlike the gray bat, has not been showing signs of recovery. During winter, the Indiana bat is restricted to suitable hibernacula in caves or mines that are located in karst areas of the east-central United States (Clawson et al., 1996). In the summertime, the primary roosting and foraging habitats include floodplain, riparian, and upland forests. The survival of Indiana bats during this season may be governed by the availability of natural roost structures in forests, such as living trees or dead trees with loose bark (Clawson et al., 1996).
Maternity colonies have been shown to exhibit strong roost site fidelity. Not only have females been documented returning to the same roosts from one year to the next, but research has shown that males will also return to summer foraging habitat occupied during prior seasons.
Original management efforts have concentrated on winter habitat of the Indiana bat. A primary objective has been the acquisition and protection of hibernacula. To date, due to initiatives both at the state and federal levels, 43% (or 54 ) of the 127 caves and mines with populations of over 100 bats are under public ownership or control (Clawson et al., 1996). Another initial management effort has been cave gating. So far, 36% (or 46) of the 127 hibernating caves are either gated or fenced.
Although original hibernacula management initiatives have been successful in implementing protective measures at many of those sites, such measures have not produced the desired result of recovery of that species. It is the consensus of the Indiana bat Recovery Team that neither identified problems and threats during the hibernating season, nor protective structures placed at hibernacula, are primary factors causing the present population declines (Clawson et al, 1996 and McKenzie, 1997).
Present understanding of Indiana bat summer ecology and summer habitat requirements is very limited. In addition, barely anything is known about their migration. It is speculated that current declines may thus be occurring during those times.
Management efforts must therefore implement a comprehensive ecosystem approach to understand the entire life history of the Indiana bat and not only focus on winter habitats. It is vital to consider the entire ecosystem used by this species (Talbot, 1996) in an effort to reverse its declining population trend. Research conducted in the summer and migration seasons may indicate that losses are occurring due to pesticide contaminants, destruction/harvesting of summer roost sites, decreased foraging areas, or reduction of forests which are commonly traversed during migration routes.
Started by Merlin Tuttle in 1982, Bat Conservation International (BCI) has been very proactive in its goal to protect and sustain bat populations worldwide. BCI strives to work cooperatively with all sectors of society and to emphasize broad ecosystem health, and therefore, an ecosystem approach, rather than focus on individual species.
Since the primary factor responsible for the decline of terrestrial wildlife is due to the loss or degradation of habitat (Talbot, 1996), a major management objective of BCI has been to protect habitats of bats. BCI's efforts in education, research, and partnerships with governments and private groups have been very instrumental and successful in achieving such goals. There are currently various projects initiated by BCI which have been invaluable in safeguarding populations of bats all around the world (BCI, 1994-95 & 1995-96 and French, 1997). These include:
Although bat populations have suffered extensively and severely from human actions, establishment of certain management initiatives and conservation measures can help assure their sustainability. The major criteria discussed in this section are a key to their future survival.
Protection and conservation of natural and anthropogenic roosting sites are critical for the survival of bat populations, especially as some species exhibit strong site fidelity and others have very narrow habitat requirements. For caves and mines, these management efforts can be achieved by acquisition, protection, or by establishing management agreements with owners of those roost sites. Installation of gates, fences, and warning signs are also essential as part of protective measures. For other anthropogenic structures, such as bridges or buildings, education will be the key component in securing protection of the bat colony.
Equally important to the protection of roost sites is the preservation of bats' foraging habitats. Inaccessible or destruction of foraging areas may prove to be a disastrous event, especially if a bat species displays very narrow feeding requirements or exhibits strong site foraging fidelity.
Bats are very vulnerable species. A single tragic event could prove to be disastrous. Destruction of hibernacula, maternity sites, and foraging areas may wipe out several hundred or thousands species at one time. Thus, after roost sites and foraging habitats are protected, periodic monitoring of these areas is necessary to identify potentially damaging changes and activities. Also, monitoring is essential to determine whether the method of protection is effective and to assess whether changes in management are needed.
Increased Funding for Research
For the most part, research of bats is lacking. Bats continue to be one of the least understood of all animals; much is still not known about their habitat and foraging requirements.
Attempts to sustain populations will require the development and application of an ecosystem approach. As illustrated by the Indiana bats, protection of their winter habitat has been unsuccessful in their population recovery. Evidence suggests that other factors occurring during the summer months or during migration are the contributing factors for the continuing, declining population.
Investigations on the effects of environmental disturbance are essential. Determination has to be made, for example, whether water pollution, siltation on aquatic insect life, pesticide contamination, and local deforestation are having impacts on populations. Without a thorough understanding of the entire life history, potential impacts by other species or effects on the ecosystem itself may never be realized; and therefore, conservation needs may never become known before a bat population becomes extinct.
Full documentation of the ecological and economic values of bats are essential for their protection in many countries. The substantiation of more than 450 economically important products from bat-dependent plants in the Old World tropics had a major impact in regional conservation planning. In many cases, proving the value of bats may be their only ticket for survival. Since humans have a tendency to do what they perceive to be in their best interest, people must perceive that it is in their best interest to manage bat populations in a sustainable way (Talbot, 1996). Otherwise, the inclination will be to utilize them for maximum and immediate gain at the expense of sustained or long-term benefits.
Another primary goal is to educate people at all levels about the importance of bats and the need to protect them. Countering negative images and changing false perceptions which have plagued bats for centuries is a key determinant essential for their lasting protection, and ultimately, their conservation. As illustrated by some of BCI's educational initiatives, people have changed how they view bats, consequently halting a stop to their eradication and prompting a willingness to protect them. All of these are necessary ingredients for sustaining bat populations worldwide.
Still unknown to be the case by most people, bats are among nature's most beneficial creatures. Years of bad reputation and abysmal public relations have led to a lack of respect and concern for this group of species. Poor or nonexistent conservation efforts, coupled with human hostility and fear, have resulted in declining bat populations.
Recent findings are illustrating the critical economic and ecological roles bats play in ecosystems. Evidence shows that bats perform a leading role in the complex web of life; they are essential allies in nature's delicate system of checks and balances. Without them, entire systems of life may die with them. This loss would not only be felt by other animal species, but by humans as well.
Although some bat species have already become extinct, there is hope for the remaining populations. Management initiatives which focus on protection and monitoring of roosts and habitats demonstrate that recovery of populations can be achieved. Still, other endeavors, such as educational and research activities, play an influential role in changing peoples's negative attitudes about bats and in prompting conservation efforts. Development and implementation of an ecosystem approach leads to a better understanding of a bat's complete life history and makes for better recommendations to counter declining bat populations. All of these techniques are believed to be essential for the successful management of bat populations; some have already proven that management of bat populations can be successful and that sustainability of this group is possible and not an unattainable goal.
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