This topic submitted by Laura Flores ( at 9:55 PM on 5/18/07.

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Tropical Field Courses -Western Program-Miami University


Laura Flores
Ecosystems of Costa Rica
Pre-Trip Research Paper
May 2007

Bats, bats everywhere! Or are they? Even though the overall bat population has been steadily declining over the last ten years, it is still possible to see a bat or two when camping, hiking or even just swimming in your own backyard at night. When people find them in attics their first instinct is to exterminate them. Bats are a mammal that strikes fear in the hearts of many people, mostly because of their ignorance in the mysterious ways of this nocturnal mammal.
The goal of this paper is to better inform the public about bats. Starting with the exploration of this mammal’s evolutionary history; the first recorded bat fossil and where it was found, what environments early bats might have preferred and their possible diets. A phylogenetic tree will also be added to help with family identity as well as to trace genetic shifts and speciation.
Once the reader has been familiarized with the evolutionary history of these nocturnal creatures, the discussion will shift to bats of today, and will include the number of known species, as well as their ranges and diets. This section will also cover habitat preferences and habits, including reproduction and family life.
The next section will focus on the tropical region of Costa Rica, exploring a number of known species in Costa Rica, where they are found, diet and ecological impact.
Hopefully some common misconceptions about bats and rabies can be dispelled in the next section by explaining exactly what rabies is and what it does to organisms that contract it. After gaining some understanding about rabies, the discussion will continue on to conservation efforts. This section will focus on why bat conservation is important, the benefits of bat conservation, and what people can do to help.
To conclude the discussion the final section will review the main facts from each section and their importance. Hopefully, the information presented in this paper will help educate the reader and create a more accepting view of this wonderful, winged, nocturnal mammal.

Evolutionary History

Bats first entered the scene during the early Eocene era, about 60 to 38 million years ago. The oldest known bat fossil was found in the Green River Formation, a geological site that is situated in three states: Colorado, Utah and Wyoming. The well preserved bat fossil found in this area dates back to about 50 million years ago. This was a very important find because it shows scientists that bats during the Eocene era had already evolved flight and possibly echolocation. Scientists today still are trying to discover if this is when the monophyletic order of Chiroptera began to diversify and echolocation began to emerge in the suborder Microchiroptera, or if echolocation evolved at several different periods and then diminished in the Old World bats, none of which use echolocation.
The fossil is a very well preserved specimen, as are most of the specimens from the Green River Formation. The bat was in a typical position that most dead bats are found in; its wings were folded and the femora were at a specific angle to the vertebral column. There is still some speculation as to how the bat died (Localities of the Eocene). This particular specimen is very special because it was found with its skeleton, membrane and cartilage still in tact. This enabled scientists to compare its anatomy with modern day bats. As you can see by the pictures below the skeletal structures are very similar.

From this fossil found in the Green River Formation scientists were also able to determine the bats diet. Along with the bats skeleton, membrane and cartilage, the bats full stomach was also included in the fossil, as well as waste not yet disposed (Localities of the Eocene). Contents of the stomach included some of the flora, algae, pollen, and arthropods of the time (Localities of the Eocene). A diet that is not very different from that of modern day bats.
The stomach contents as well as the surrounding soils were able to help scientists and paleontologists form conclusions about the environment of the area during the Eocene Era and the changes during the same period. From the fossils found along with the bat fossil it was determined that the area was at least 2200ft above sea level. This information, along with the contents of the bats stomach, help scientists determine the environments in which the organisms lived. During the Eocene the Green River Formation contained flora such as palms, cat-tails, sycamores, and many other plants that are familiar and located here in North America. According to the Localities of the Eocene article you would also have seen some flora more common or even restricted to eastern Asia. The climate is also believed to have been temperate or sub-tropical. The fossil can also be used to draw a more accurate phylogyny. Data collected from the Green River Formation bat fossil suggests that there has been no evolutionary change in the order Chiroptera in the past 50 million years. There are two sub-orders for the monophyletic order Chiroptera; Microchiroptera and Megachiroptera. The sub-order Megachiroptera consists entirely of the old world bats, or what are known as fruit bats in the family Pteropodidae and the old world bats included in the family Rhinolophoidea. Bats from the sub-order Megachiroptera are more closely related to their sister group primates than to the sub-order Microchiroptera.
Both of these phylogenetic trees include 5 out-groups and 5 families of chiropterans that are now extinct. Tree A illustrates where the different families originated. Tree B translates the two groups Laurasia and Gondwana into the actual continents from which the families originate (Teeling, et al 2005).

Bats of Today
As of today bats and rodents vie for the right to claim the second largest group of mammals. In some tropical habitats bats outnumber all other kinds of mammals. There are approximately 925 known species of bats today that inhabit all continents except for the Polar Regions and some isolated islands. All 925 known species can be classified in the following families: Craseonycteridae (bumblebee bat and the hog-nosed bat), Emballonuridae (sac-winged bats, sheath-tailed bats and their relatives), Furipteridae (smoky bats and thumbless bats), Megadermatidae (false vampire bats), Molossidae (free-tailed bats), Mormoopidae (ghost-faced bats, moustached bats and naked backed bats), Mystacinidae (New Zealand short-tailed bats), Myzopodidae (Old World sucker-footed bat), Natalidae (funnel eared bats), Noctilionidae (bulldog bats), Nycteridae (slit-faced bats), Phyllostomidae (New World leaf-nosed bats), Pteropodidae (flying foxes and Old World fruit bats), Rhinolophidae (horseshoe bats and Old World leaf-nosed bats), Rhinopomatidae (mouse-tailed bats), Thyropteridae (disc-winged bats), and finally the Vespertilionidae (evening bats and vesper bats) (Wund and Myers, 2005).
The dietary preferences vary by family. The ancestors of the Microchiroptera sub-order were mainly insectivores (Novick, p 104). Their diet consisted of only insects, as to which the bat diet today does also. Most bats feed on a variety of insects, but some species have more specialized tastes and hunting techniques, for example the Maylasian free-tailed bat is said to be so selective that it seeks out ants engaged in their nuptial flight (Novick, p 104). One way naturalists help to identify bats they are observing is by gauging the altitude at which they hunt. The place of preference in which the bat prefers to hunt insects is also a factor, whether it is over cultivated fields, water, or under the jungle canopy. The amount of insects a bat is able to eat is not really known. In laboratory studies moustache bats can consume two fruit flies each second for short periods of time, or 15 to 20 per minute over longer periods of time. In nature Little Brown Bats are estimated to catch 150 large insects or 5000 very small insects per hour. The Mexican free-tailed bat in Texas is estimated to eat around 6,600 tons of insects a year (6 million kg). Some small bats may be able to consume half of their body weight in insects each night (Novick, p 104). While the majority of Microchiropterans are insectivores, some, like the Megaderma lyra, have turned to preying on small vertebrates such as tree frogs, lizards, small birds, mice, shrews, and small bats. The other known carnivores are the false vampires and their relatives from the family Phyllostomatidae (Novick, p 105).
There are two main families that contain many genera that feed on fruit. All Megachiropterans eat fruit, at least part of the time. The fruit eating bats must vary their diets or migrate because many of the fruits have a short ripening season. Migration in those bats that migrate are dictated, or determined by the seasonal ripening of wild crops, as well as seasonal variations in the weather. The Megachiroptera also feed to some extent on flowers. The subfamily Macroglossinae feeds principally on pollen, nectar and petals. The other two groups that feed substantially on pollen and nectar are Glassophaginae and Phyllonycterinae. The Members of all three of these groups share certain characteristics (Novick, p 105-106).
For most people the scariest bat is the Vampire bat. It is widely assumed that vampires are aggressive. According to Alvin Novick, the author of The World of Bats, vampires are shy and cautious. They lick the site of the potential bite and if the prey is disturbed or moves they quickly abandon the meal. In his book he writes about an ethologist named Konrad Lorenz who visited the lab when they were working with vampires. “When he heard that none of us had yet been bitten by a vampire, he replied that he would like to experience such a bite himself. After failing to discourage him, I suggested that he corner and prod one of the bats in order to provoke it. Try as he would, he could induce no more than some angry cries and a great many scrambling escape attempts” (Novick, p108). Most vampires feed mainly on animals, favoring herd animals such as goats and cattle.
The habitat that a genera of bat lives in is predictably in sync with its choice of sustenance, for example, an insectivorous bat will live near an open field with a water supply close by, a frugivorous bat will most likely live in the neo-tropics as will a carnivorous bat, who may also be found hunting small rodents in the desert. An herbivorous bat (one that feeds on pollen nectar, and sometimes petals) can be found in the neo-tropics or around prairies. Typical habitats where bats can be found are: tropical forests, temperate forests, and deserts, open fields, agricultural areas, suburban and urban areas (Wund and Myers, 2005).
Reproduction and Family Life
Mating takes place in the fall during the aggregation to the location of their winter hibernation. Mating habits vary among the genera, but most genera of bats are either promiscuous or polygynous. Promiscuous bats usually gather in large groups in one or more trees and mate with nearby individuals. In the polygynous genera one or two males usually keeps a small harem of females and secure all matings with females in the harem, until supplanted by another male (Wund and Myers, 2005).
Not all bats are promiscuous or polygynous. Some are monogamous. In the monogamous community the male, female and offspring roost together with the male contributing to the protection and care of the offspring. Some the monogamous species include: Vampyrum spectrum, Lavia frons, Hipposideros galeritus, H.beatis, Nycteris hispida, N. arge, N. nana, and some of the Kerivoula species (Wund and Myers, 2005).
One species of Megachiropteran, the Hypsignathus monstrosus use a lek mating system where the males compete in a lekking arena. In other species courtship behavior is nonexistent. Some males will mate with hibernating females who do not react at all to the copulation (Wund and Myers, 2005).
As with almost all mammals, the young need care from the mother. Female members of promiscuous genera will form a nursery colony and roost together. This helps with protection and care of the young. Another reason for the large nursery colonies is to help keep the young warm at a smaller metabolic expense of the mothers (Novick, p 76). In a monogamous pair, as stated in the previous paragraph, the male, female and offspring will set up a single roost.
It is not known why some bats species choose to live in large colonies and others choose to live in smaller colonies, or even solitarily. Bats that live in large colonies can number into the millions; like the Mexican free-tailed bat in Texas and New Mexico (Novick, p 76). In groups such as the Jamaican fruit-bat, which is common throughout most of tropical America, usually forms colonies of only a few hundred individuals (Novick, p 76).
Bat species that seem to have significantly smaller populations appear to be solitary, some returning to the same roost not only each night but also year after year (Novick, p 76). Since these species of bats roost alone and they have such a wide distribution it is hard to estimate their populations. Some examples of solitary bats are both Lasiurus species of North America (the red bat and the hoary bat), the large African fruit bat, Hypsignathus and the Philippine bat, Myotis jeannei.
In some species of chiroptera there is also segregation by sex. In Mexican free-tailed bats only meet to mate. In the spring when they begin their migration north, males and females will meet en route, and basically have a one night stand in roosts located in buildings, caves or hollow trees. Eptesicus and Myotis roost in colonies but each colony whether they are cave dwellers or outdoor-roosters the colonies are either male or female, even when not mating (Novick, p 77).
Bats of Costa Rica
In Costa Rica there are 103 known species of bats. These 103 species can be broken down as follow: 43 insectivorous species, 25 frugivorous species, 11 nectivorous species, 3 sanguivorous species and 18 species that feed on some combination of all the previous categories.
The family groups that these bats belong to include the Emballonuridae, Furpteridae, Molossidae, Mormoopidae, Natalidae, Noctilionidae, Phyllostomidae, Thyropteridae and Vespertilionidae. Habitat distribution varies among these families.
The Family Emballonuridae is found sheltering in rocky crevices, caves, ruins, houses, trees, leaves and hollow logs. This family tends to use roosts that are more exposed than those found in some other bat families (Hester and Myers, 2001). An example of a bat from this family is the sac-winged bat. The picture to the right is of a sac-winged bat pup. The members of this family are primarily insectivorous, but have been observed to eat fruit on occasion. The hunt while in flight. This method of catching insects is called “hawking”.
Another family that is represented in Costa Rica is the Furipteridae. This family is made up of two genera that each contains one species, one is the smoky bats and the other is the thumbless bats. The Furipteridae are members of the super family vespertilionidea (Weinstein and Myers, 2001). These bats are strictly insectivorous and may be further limited in diet to moths and butterflies (Weinstein and Myers, 2001). Furipterids live in diverse habitats from lowland rainforest to the extremely arid western deserts of South America. Colonies range from 100 to 300 individuals and are known primarily caves and man-made structures (Weinstein and Myers, 2001).
The Molossidae family, which consists of free-tailed bats, is another of the bat families that resides in the neo-tropical region. Molossids reside in the New World, ranging from the central United States south to southern Argentina. All members of this family are insectivorous, catching their prey by hawking. Their roosting habits range from solitary to living in immense colonies of millions of bats, usually in caves. This family contains approximately 85 species that are placed in about 12 genera.
Continuing in alphabetical order, the next family is Mormoopidae. It consists of two genera that branch out to eight different species. The Mormoopids range from Brazil to the southern United States. Members of this family are strictly insectivorous and mostly live near water. They roost in groups that are sometimes very large colonies. Some species from this family are thought to roost exclusively in caves. Mormoopids can be found in habitat types that range from rainforest to arid deserts.
Until recently the Mormoopids were thought to be closely related to the Phyllostomidae, another family of bats that can be found in Costa Rica. This family ranges from the southwestern United States south to northern Argentina and the West Indies. The phyllostomids include around 143 species that are placed in 49 genera. Extant phyllostomids are categorized into 7 or 8 sub-families. Diet varies between species in this family. They include carnivorous, insectivorous, frugivorous, nectar feeders, as well as 3 species of vampires that rely solely on blood for food.
The funnel-eared bats from the family Natilidae make up a single genus containing 5 species. They can be found in the New World in tropical lowlands ranging from northern Mexico south to Brazil. Natilids also occur in the West Indies. These bats are quite common in some areas and can be found roosting in caves and mines. Social groups range in number from very large to fewer than ten. Natilids have a distinctive flight; it can be described as fluttery and moth-like. Funnel-eared bats feed exclusively on small insects (Weinstein and Myers, 2001).
Members of the Noctilionidae Family are very distinctive. They are commonly called the Bulldog or Mastiff bat. There are 2 species that are categorized in a single genus. Both of the species in this family feed on insects, but N. Leporinus also feeds on fish, frogs and crustaceans. These bats use echolocation to locate fish that are swimming just below the surface of the water. They have also been said to have a musky odor, or smell like fish. Roosting sites are usually in hollow trees or deep cracks in rocks that are near water. Bulldog bats home ranges from northern Mexico through Central America south to Paraguay and northern Argentina.
The largest family in the order chiroptera is the Vespertilionidae. This family consists of 35 genera with 318 species. To make working with this family easier taxonomists and some authors have divided it into subfamilies. This is cause for some confusion because there is little agreement on the composition of these taxa. As well as being the largest family, Vespertilionidae is also the widest ranging family. Vesper bats inhabit tropical forests, deserts and temperate zones. The only regions where one would not find vesper bats are the Polar Regions and some remote islands. Vespids are mainly insectivores. Along with the wide range of distribution they also show a wide range of wing shapes, roosting behavior, and foraging strategies (Hester and Myers, 2001).
Ecological Importance
After discussing some of the different families that inhabit Costa Rica, one might ask “Why are bats so important?” In a tropical setting such as Costa Rica the frugivores play an important role in pollination and seed dispersal. Insectivorous and carnivorous bats play a role in controlling their prey populations. Bats are a keystone species in some communities, especially in the tropics.
Some other important ecological factors about bats that are not well known are how insectivorous bats can help with agricultural pests such as root worms, or disease spreading insects such as the mosquito. Bat guano is often used as a fertilizer for crops. Each year many tons of guano is mined from caves where large bat colonies reside. Some of the plants that are pollinated by nectar feeding bats are of economic importance to humans. These are plants such as agave and bananas. The large species of bats from the Pteropodidae family are sometimes eaten by humans.
In medicinal studies of anticoagulants for stroke patients, scientists are studying “Desmoteplase” an anticoagulant found in the saliva of vampire’s. The purpose is to help prevent blood clots in humans.
Rabies is a virus that is transmitted through saliva. Rabies is a deadly viral disease of the central nervous system that is transmitted through the saliva of an infected animal. The most common misconception of this disease is that you have to be bit to contract it. This is not true; bites are just the most commonly known method of transmission. If an infected mammal’s saliva comes into contact with mucous membranes, or into an open cut, the virus is passed. Another common misconception is that bats carry rabies. In fact, about only 0.5% of bats ever contracts rabies. Bats also suffer the symptoms of rabies, as well as die from rabies.
Statistics from 1995 show that over 1,000 people died of Malaria in that year. This is ironic because Malaria is a disease that is spread by mosquitoes, which are a main food source for bats. That same year there were a total of 9 people who died from rabies (Bat Conservation). According to statistics from the CDC (Center for Disease Control) through May 15, 2006 there were 48 cases that were confirmed as a result of bat rabies, 46 deaths confirmed as a result of bat rabies in the past 55 years, or since 1951, this averages out to less than one death per year, with four of the deaths were results of transmission through organ transplants. Another interesting thing that can be discerned in the report is that in all cases that were discovered in patients with the ability to answer questions, they all had purposefully picked up a bat and handled it. No reports of a bat purposefully attacking were noted. One of the biggest reasons that bats do not become aggressive when they contract rabies is because they usually suffer from the paralytic type of rabies. This is why it is suggested that you not handle a bat that looks like it has been hurt with out proper experience, and safety equipment.

Conservation Efforts
At the current time there are no actual conservation efforts being taken for these wonderful miracles of nature because there is so little known about them. The Indiana bat is one that is on the endangered species list and it and its habitats are protected by federal law.
Individuals can help by learning ways to eliminate bats from spaces where they are not wanted by a method called exclusion. This simply means that the bat can exit, but not return. It also helps to give them an alternate housing option, such as a bat house. Also, by learning about these creatures and being better educated about their lifestyles helps to create a better understanding of why they are so important. For more information on conservation efforts you can go to,, or

As you can see from the previous information there has been little evolutionary change in this monophyletic order for the past 50 million years. Even with so little change it is still unknown how many species there are in the world. Also the populations of some species are hard to estimate because of the particular species migratory and group habits. Bats are also a very diverse group in that they cover all links in the food chain.
Once all of the gaps have been filled in as completely as scientifically possible, this wonderful, natural pesticide (that has no adverse effects when used properly) may be a huge advancement in many areas such as technology: sonar equipment, medicine for humans: preventing blood clots in stroke patients, pest control: strategically placed bat houses to make the most of their large appetites, and most importantly, how it is possible for one species to exist for so long with so little evolutionary change in their order.

Works Cited
Baker, Robert J., J. K. Jones, Jr., and Dilford C. Carter. Biology of Bats of the New World Family Phyllostomatidae, Part II. Lubbock: Texas Tech P, 1977.

Brenes, Kaytee, Micah Fleming, Nalini Rao, and Lani Smith. "Localities of the Eocene: the Green River Formation." Green River Formation. 29 Aug. 1999. Dept. of GLG, Berkeley U. 23 Mar. 2007.

Clemens, P. 2002. "Glossophaga Commissarisi." (On-line), Animal Diversity Web. Accessed February, 22 2007 at http://animaldiversity.ummz.umich,edu/site/accounts/information/Glossophaga_commissarisi.html

"Green River Formation." The Paleontology Portal. 23 Mar. 2006 .

Haack, M. 2002. “Furipterus horrens” (On-line), Animal Diversity Web. Accessed February 22, 2007 at

Kricher, John C. A Neotripical Companion an Introduction to the Animals, Plants and Ecosystems of the New World Tropics. Princeton: Princeton UP, 1989.

Myers, P., R. Espinosa, C.S. Parr, T. Jones, G.S. Hammond, and T.A. Dewey. 2006. The Animal Diversity Web (On-line). Accessed March 06, 2007 at

Novick, Alvin. The World of Bats. New York, Chicago, San Francisco: Holt, Rinehart and Winston, 1969.

Potchynok, A. and P. Myers. 2006. “Diclidurus albus” (On-line), Animal Diversity Web. Accessed February 22, 2007 at

Sears, Karen E., Richard R. Behringer, John J. Rasweiler, Iv, and Lee A. Niswander. "Development of Bat Flight: Morphologic and Molecular Evolution of Bat Wing Digits." PNAS 103 (2006). 06 Mar. 2007 .

Taylor, Peter J. Bats of Southern Africa Guide to Biology, Identification and Conservation. Pietermaritzburg: University of Natal P, 2000.

Teeling, Et Al., Emma C. "A Molecular Phylogeny for Bats Illuminates Biogeography and the Fossil Record." Science 307 (2005): 580-584. 19 Mar. 2007

Thompson, J. 2004. “Hylonycteris underwoodi” (On-line), Animal Diversity Web. Accessed February 22, 2007at

"What is Rabies?" University of Iowa Hygienic Laboratory. 2007. Iowa Universtiy. 13 May 2007.

"What is Rabies?" State of Michigan. 02 Dec. 2002. State of Michigan. 13 May 2007

Wund, M. and P. Myers. 2005. “Chiroptera” (On-line), Animal Diversity Web. Accessed March 06, 2007 at

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