Students hard at work on the "Mangrove Challenge"! (Sierpe River, SW Costa Rica)
Biodiversity is a word synonymous with Costa Rica. Given this biodiversity, it may come as a surprise that Costa Rica has only 200 species of mammals. The most abundant mammal found in Costa Rica is the bat, with 110 species (Baker). Bats are an essential element in rainforest ecology. This paper will explore the methods Costa Rica is utilizing in conserving its bat populations, as well as the challenges which are presented to this prevalent and essential creature.
Costa Rica is a Central American country which is experiencing a conflict between human growth and environmental health. In previous years, the deforestation rate in Costa Rica skyrocketed. While deforestation has subsided, and conservation efforts have been enacted, human activities continue to have an impact on bat populations. Increased agriculture not only clears land of bat habitat, but also depends heavily on pesticides. These pesticides have a detrimental effect on bats by accumulating substantial amounts of pesticides in the bat’s stored fat due to the consumption of pesticide laden insects. When the fat is metabolized during hibernation or migration, the pesticide concentrations can reach deadly levels, especially in the brain. Additionally, these pesticides are passed from mother to offspring through milk, adding to the effects the offspring will undoubtedly encounter through its lifetime (McCracken).
Human produced synthetic chemicals are not the only pressure on bat populations, human disturbance through urban development and misconceptions of bats also play a crucial role in declining bat populations. Don Clark when asked about his opinion on environmental contaminants on bat populations states, “it is doubtful that the combined adverse effects of all the various chemical and metal pollutants have been as serious as the total impact of disturbance, vandalism, and habitat destruction.” (McCracken). This statement echoes the importance of human influences on bat populations worldwide.
The greatest threat to bat populations is habitat loss. Humans seal up caves, cut down forests, and destroy many bat roosting sites. Human disturbances to hibernating bats also pose a serious threat. Disturbing hibernating bats causes the bats to use up precious stored energy when emerging from the state of hibernation. The common misconception that all bats carry rabies and are vampires lead to the careless destruction of valuable roosting sites and senseless killing of beneficial bats (Hardman).
The aforementioned factors of habitat loss, pesticide use, and misinformation all have a substantial impact on declining bat populations. Certain species of bats have been seriously impacted resulting in a threatened or endangered status. The following paragraphs describe these such vulnerable bat species.
The Honduran white bat (Ectophylla alba) is a rare bat species found in Costa Rica. It is among one of the 15 species of tent making bats. These group of bats collapse leaves to form roosting sites. During roosting hours the bats are well camouflaged and appear to be a pale green. These bats like most bats in the tropics are frugivores (eat fruit and nectar) (http://www.batcon.org/batsmag/v12n1-10.html).
Another fascinating bat of Costa Rica is the vampire bat (Desmodus rotundus). Out of the one thousand bat species, there are only three species of vampire bats. Vampire bats commonly feed on large birds, pigs, horses and cattle. In Pre-Columbian times vampire bats existed in small numbers, but due to European colonization and introduction of cattle, these bats flourished with an almost limitless supply of food. Today, deforestation to raise cattle exacerbates this problem. In true Dracula fashion, these bats prefer to hunt in darkness. When the moon is full, these bats will not be seen flying. Vampire bats spend a considerable time on the ground, and therefore can walk, run and jump on their hind legs. Vampire bats can even crawl on all fours when their wings are folded using their thumbs as forelimbs (Bellwood).
An important bat in Costa Rica is the Talamancan yellow-shouldered bat (Sturnira mordax). This species is rare and is only found in the mountains of Costa Rica and in small areas in Panama. These bats are important seed dispersers. While birds tend to disperse seeds in mature areas, bats tend to drop seeds in open cleared areas, which is important in succession. Yellow-shouldered bats rely heavily on the fruit of Solanum rugosum. These shrubs are pioneer species which further adds to the biological importance of these bats (Merlin D. Tuttle).
Bats are vital in maintaining ecosystem balance. Microchiropteran (insectivorous) bats provide an important service of pest control, which benefits farmers and many people alike (Toufexis). Bat’s contribution to commercial agriculture through natural insect control is worth millions of dollars annually (Toops).
Megachiropteran bats, or fruit eaters, are exceptional pollinators and seed dispersers (Toufexis). Bats pollinate many types of fruit such as bananas, avocados, dates, figs, cashews, and mangos (Toops). Bats also pollinate flowering plants. Although flowering plants in the tropics have varied morphologies, plants pollinated by bats are usually characterized by nocturnal flowers, inflorescences arranged away from foliage to provide easier access to flowers, a musky aroma, and a nectar rich in hexose sugar (Simmons). As previously stated, bats play an important role in the recolonization of plants into large gap areas. Bats ingest the fleshy fruits, digest the pulp and defecate the seeds usually in flight. The fruits eaten by bats are typically from plants that are pioneer plants, which help in the renewal of vegetated areas. Bat’s guano also aids in re-growth because it is rich in nutrients and acts as a fertilizer (Simmons).
Although bats are extremely beneficial to ecosystems and economies, they also cause damage. Vampire bats are especially a problem in Costa Rica. Each year there are about two outbreaks of paralytic bovine rabies, with a total loss of 30 animals annually, which takes a toll on the cattle industry. It is estimated that the cattle industry has lost more than $600,000 in the past 15 years. The Costa Rican government operates a vampire elimination program that takes action in areas where rabies is reported. Often people take matters into their own hands to try and control the situation. For example fruits and bananas are sometimes laced with poison, which kills fruit-eating bats that are essential to ecosystem health and regeneration. Since Costa Rica is a country which is heavily dependent on its natural environment for revenue, forest regeneration and pollination are crucial to the country’s economy, therefore effective conservation strategies are needed (LaVal).
Costa Rica is taking action to conserve its bats. A new program entitled Programa para la Conservacion de los Murcielagos de Costa Rica (the Program for the Conservatio of Costa Rican Bats) is one serious effort Costa Rica is taking to preserve its vital bat species. Although bats of Costa Rica have been extensively studied, little is known about the basic biology of most bats, therefore specific conservation plans cannot be developed. However, in March 2000 Bernal Rodrigez-Herra began to build public enthusiasm for bats by designing a bat exhibit featuring live bats. The program focuses on elementary school-aged children and is located by national parks where education programs already exist. Bat workshops are being developed and presented to children as apart of these education efforts (LaVal).
In addition to educational programs, research and data collection are also vital elements in the conservation of Costa Rica’s bats. PCMCR continues to collect data on distribution, abundance, and biology of Costa Rica bats. Researchers use bat detectors which translates echolocation frequencies to aid in the identification and study of bats. The use of mists nests are also being utilized to study insectivores and frugivores (LaVal).
Costa Rica may also pursue conservation efforts which include captive breeding once threatened and endangered species are identified, and also legislation to protect bat species. PCMCR is faced with many challenges, but the few committed staff members and aid from Bat Conservation International and Mexico’s program for migratory bats will undoubtedly will have an impact of the conservation of bats throughout Costa Rica and the rest of the tropics.
Baker, Christopher. Costa Rican Handbook. Available from world-wide web at http://photo.net/cr/moon/mammals.html. Accessed 26 April 2005.
Belwood, Jacqueline J. and Patricia A. Morton(1991). Vampires: The real story. Bat Conservation International Magazine. Vol. 9:11-16.
Hardman, Chris. Going to Bats. Americas Nov/Dec97, Vol;. 49, Issue 6.
LaVal, Richard K., and Bernal Rodrigez-Herra. Comserving Costa Rica’s Bats; A New Program Takes 110 Bats Species Under its Wing. Bat Conservation International Magazine. Available from world-wide web at http://www.batcon.org/
McCracken, Gary F. (1986). Why are We Losing Our Mexican Free-tailed Bats? Bat Conservation International Magazine. September. Vol. 3:1-2.
Toufexis, Anastasia, and Sam Allis. Bats New Image. Time Magazine. Vol. 146. Issue 8.
Tuttle, Merlin D. (1989). Cover photo and description. Bat Conservation International Magazine. Summer. Vol. 7:1-2.
Simmons Nancy B., Robert S. Voss, and Scott A. Mori. Bats as Pollinators of Plants in the Lowland Forests of Central French Guiana. Available from world-wide web at http://www.botanypages.org/mori/batsplants/batpollination/pollination_frameset.htm. Acessed 6 May 2005.
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