Bats dominate the native mammalian diversity on Jamaica. Although known locally as 'Ratbats,' bats actually are more closely related to primates than they are to rodents. Their scientific classification, Chiroptera, comes from the Greek roots cheir (hand) and pteron (wing). As the name implies, the wing of a bat is a highly modified hand, with elongated fingers and forearm over which a thin, elastic skin is stretched (see drawing).
Being mammals, all bats have eyes and can see more or less well. But they also use echolocation to help navigate in the dark. There are twenty one species representing 6 families which are present across the island (Griffiths and Klingener 1988).
Recent visitor, Dr Uli Schnitzler, has suggested that we can group bats according to their use of the auditory environment:
Eleven extant species
are endemic to the West Indies and four are endemic to Jamaica (19%
species-endemism). Fifteen of Jamaica's 21 bat species are obligate
cave dwellers, including three of the four endemics. Their colonies
occupy less than 17% of caves documented island-wide and nearly one
third of these bat caves are recorded in the environs of Cockpit Country
Three additional species are known from the fossil record (Tonatia bidens, Brachyphylla nana, and Mormoops megalophylla).
Species richness in the majority of documented caves is low, with nearly 60% of bat caves occupied by fewer than four species. Fewer than 10 caves account for all the known colonies of some of the rarest species, such as Phyllonycteris aphylla. Several caves in the Cockpit Country (e.g., Windsor Great Cave (where a bat research project has been initiated), Marta Tick Cave) are notable for their high diversity, which includes representation of insectivores, frugivores, and specialized nectivores. Others, such as Wallingford Sink and Oxford Cave, are noted for the collapse of their bat faunas over the past 70 years, quite likely due to excessive disturbance associated with guano harvesting and tourism (McFarlane 1986) -see threats to caves. Of species that are not obligate cave-dwellers (i.e., roost in tree hollows or manmade structures), the endemic Hairy-tailed bat (Lasiurus degelida) is of particular scientific and ecological interest as this is the only genus of bat in which more than two young per birth are common (Nowak 1994).
The largest bat colonies are dominated by the moustached bats of the genus Pteronotus, of which three occur in Jamaica. While P. parnellii has been collected extensively for bioacoustic research (Kobler et al. 1985, Henson and Henson 1991), there exists no ecological or demographic information for this species to reliably assess the sustainability of harvesting rates. There are, in fact, few published studies on the ecology of any of Jamaica's cave bats. Information on breeding biology is limited to data collected from museum specimens. Most published accounts have been based on very limited collecting, often strictly for taxonomic or biogeographic research. Collections have been taken repeatedly from a small number of well-known caves while the composition of the majority of bat colonies in caves remains unknown.
The economic importance of bats
Insectivorous bats consume enormous quantities of nocturnal insects, including many that are harmful to crops and pests to humans. For example, a bat the size of Pteronotus parnellii (14g) would be capable of consuming over 1,000 insects per night, including mosquitoes. A colony of 50,000 individuals of this species, as is the estimated population for Windsor Great Cave, would consume nearly 18 billion insects per year.
Fruit-eating bats are the most important seed-dispersing mammals in the tropics. Because they generally defecate in flight, seeds are dispersed away from the mother tree, thus increasing a seedling's chances of survival. In forest regeneration studies in Africa, Mexico, and Asia, bats were responsible for dispersing 75-95% of all seeds, with birds, primates, and other animals accounting for the balance (Medellin and Gaona 1999 and references therein, Vermeulen and Whitten 1999).
Nectar-feeding bats, along with some fruit bats that visit flowers, pollinate thousands of bat-dependent tropical trees and shrubs. Among commercially-valuable plants, bats are responsible for pollinating banana, mango, guava, avocado, fig, and cashew.
Guano is rich in phosphate and used as fertilizer and organic mulch. Commercial harvest must be assessed carefully to ensure excessive disturbance does not cause the bats to abandon the cave, with the recognition that other suitable cave environs may not be available in the area.
Scientific, aesthetic and cultural value of bats
Echolocation and bioacoustic studies dominate the scientific research of Jamaica's bats. The Pteronotus parnellii are particularly used because they emit at a constant frequency of about 60KHz and use the doppler effect (the frequency shift of echoes) to "see" their prey. Their ear passage has thus evolved with a particularly long section which is tuned to the 60KHz region, making the researchers' task easier.
The evening emergence of large bat colonies enables visitors to observe bats without disturbing roosting and nesting colonies within the caves.
HEALTH CAUTION FOR CAVE EXPLORATION IN JAMAICA (Fincham 1997):
Histoplasmosis is a human fungal disease resulting from
infection with the organism Histoplasma capsulatum, and is a
potential hazard to anyone entering a tropical cave. Pulmonary
histoplasmosis causes flu-like symptoms and, in severe cases,
requires hospitalization. The fungus is considered common in
Jamaican caves and is closely-linked with, but not exclusive to,
cave-dwelling bats. A brief exposure is likely to result in
infection. This was first recognized in 1978 when, a group of
visitors were taken into a Jamaican cave; 25 of the 28 subsequently
showed some symptom of the infection, including a woman and her
son, aged 4yrs, who had remained at the cave entrance (Fincham
1978). Histoplasma spores may be present in dry guano piles
even if the cave is no longer occupied by bats. Any persons known
to be immunologically compromised should not expose themselves to
the risk of histoplasmosis and all visitors to Jamaican caves
should be aware that infection probabilities are high.