Volume 10, Issue 3, Fall 1992


By Ochoa, Jose G.

by Jose Ochoa G.

Venezuela is a land of great diversity, both in topography and in the number of its plants and animals. The great central plains, or llanos, lie between the mountainous coast and the Guiana Shield of southern Venezuela that covers nearly half the country. Here the tepuyes rise steeply out of the lowland rain forests, unique sheer-walled islands of stone in an ocean of trees. This is the land of the famous Angel Falls, the world's highest at 3,212 feet, and Mt. Roraima where early explorers once imagined a lost world existed.

Roughly 15 percent of the country--some 57 million acres--is under protection in national parks, natural monuments, and faunal refuges. Although Venezuela has one of the highest amounts of land in Latin America included in national parks, its lowland rain forests, where bat diversity is at its highest, are scarcely represented in these protected areas. South of the Orinoco River, where the largest extension of Venezuela's rain forests lie, most of the national parks protect only the highland ecosystems of the tepuyes. In some cases, protected areas are simply not large enough to conserve the inherent diversity of the forests. Only the Andes and coastal mountains have an adequate system of protection.

The rain forests of Venezuela, like those in many other tropical countries, are very old and complex ecosystems maintained only by an intricate balance of plant-animal interactions. The world's tropical forests contain more than 90 percent of all terrestrial plant and animal species--our planet's richest biological diversity. Throughout both the Old and New World tropics, bat communities are an important part of this diversity. In Venezuela, about 330 mammal species have been recorded, almost half (150) of which are bats. Five of these were discovered in only the last ten years. Furthermore, the forests of southern Venezuela support at least 65 bat species and, by some estimates, as many as 80 could be present. In these ecosystems, bats comprise 50 percent of all mammal species, and they represent an important factor to consider in the conservation of mammal communities in the region.

For many years, biologists have disagreed over which animal groups are the most important to the ecological balance of tropical forests and which species should be given highest priority in conservation strategies. While the often heated controversy continues over whether large animals (such as jaguars or tapirs) or small creatures (such as birds and insects) need more attention, few biologists even mention bats.

Information is scarce, and it has been difficult to substantiate the status of any animal species, particularly bats. In many Latin American countries, including Venezuela, wildlife conservation has therefore been based primarily on the management and protection of medium- to large-sized vertebrates, because they are better known and their by-products, such as fur or meat, often have recognized economic value. But even some of these, such as jaguars and otters, are in trouble; many are now considered endangered by the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) and the International Union for the Conservation of Nature (IUCN).

Not only has the conservation status of bats received little attention, but their ecological contributions to neotropical forest dynamics have been largely ignored. In many Latin American countries, bats are excluded as key components in management programs for forests or as indicators in monitoring the health of these ecosystems. This results from several factors, but by far the most significant is a lack of education about the ecological and economic roles of bats and a lack of understanding of bats in general. Most Latin Americans believe that only a few bat species inhabit the forests and that all are noxious or are vampires. In addition, there are few regional bat specialists and only a small number of research programs devoted to the study of bats.

The high diversity of bats, combined with the fact that they are integral components in a number of food chains, indicates that bats are extremely important regulators of the complex ecological process of maintaining the health of neotropical forests. Insectivorous bats, for example, consume numerous insects each night. Some of these insects are significant consumers of many plants that are important both ecologically and economically. Seed-dispersing fruit bats are also primary reforesters in disturbed areas. In places where high deforestation rates have already been recorded, and where more timber exploitation is planned, bat seed dispersal is especially critical to forest regrowth.

In 1987, I began a project to evaluate how selective timber extraction has affected the structure and composition of mammal communities in the lowland rain forests in the Guayana region of northeast Bolivar State. Conducted in the Imataca Forest Reserve, the field work was supported by Wildlife Conservation International, the Audubon Conservation Society of Venezuela, the EcoNatura Association, and the Intecmaca Company. Using bats as indicators of environmental quality, the study identified some important factors that are now helping us to develop primary forest protection programs for the conservation of bats in that region.

In this field study, high population levels of several understory fruit-eating bats, such as yellow-shouldered bats (Sturnira lilium), were discovered in forests used for timber production. In these disturbed habitats, plants of the genera Vismia and Solanum are some of the first to grow in forest gaps, quickly becoming very dense and providing an important part of Sturnira's diet. The bats act as efficient "farmers," dispersing large quantities of seeds of these rapid-growing pioneer plants each night in forest gaps. Once these bat-dispersed plants are established, other animals use them for shelter and disperse yet more seeds, continuing the process of forest regrowth.

Although several studies on the co-evolutionary relations between bats and plants have been done, much more intensive research is needed. Educational programs must also be developed to inform both forest managers and the public about the value of bats to the regeneration of rain forests.

Despite clear documentation of bat roles, many forestry managers of natural areas producing timber and other resources ignore the ecological and evolutionary relationship between valuable commercial plants and bats. For example, two of the most important trees in the Venezuelan timber industry, kapok (Ceiba pentandra) and pochote (Bombacopsis quinata), are pollinated by several species of leaf-nosed bats. Unfortunately, management programs for these trees do not include monitoring the activities of their bat pollinators.

High biological diversity levels have been recorded in Venezuela's lowland rain forests. As a result of our study, priorities to conserve mammal communities, including bats, have been now identified. Priorities are based on the diversity of mammals, occurrence of a high number of endangered species, scarce representation in national parks, and the high ecological sensitivity of these forests.

Yet in these forests, an extensive area within reserves--some 46 million acres--has been marked for timber exploitation. Selective logging in reserves is controlled by government agencies and private concessions.

Unfortunately, biodiversity levels in many forest reserves have been drastically reduced as a result of badly conducted forestry programs, mining activities, agriculture, and urban expansion. Not only has this diversity been lost forever, but the development activities that caused it have not been very successful. The high ecological sensitivity of forests and soils, use of wood production technologies not appropriate for the ecosystem, and an extremely deficient research program on the ecological effects of forest exploitation all have limited the success of rain forest development on a sustainable basis.

As the structure of forests change after logging, the composition of the bat communities changes also. Overall, we discovered a 30 percent reduction in bat diversity in areas that had been logged. Some bats, however, were collected with high frequencies in the exploited habitats. When logging produces gaps and modifies the primary condition of the forests, some insectivorous bats of the canopy (free-tailed or mastiff bats and sheath-tailed bats) are able to move down to feed in the understory where they catch a high number of insects displaced by forest disturbance. With forest gaps, we also noted an increase in the number of aerial insectivores and an absence of some gleaning and carnivorous bat species.

Thirteen of the 66 bat species recorded in forests from this region were discovered to be restricted to primary, or undisturbed, habitats. One important thing we learned is how closely three insectivorous leaf-nosed bats (Tonatia bidens, T. sylvicola, and Micronycteris daviesi) are associated with the primary condition of forests. They appear to have very specific requirements for the type of prey they eat, as well as their habitat and roost sites, none of which is available after logging. When forests are cut, these species simply disappear.

We learned a great deal from these three bats of the primary forest, in addition to learning from other arboreal mammals such as the kinkajou, porcupine, and small rodents. Their needs helped us to design a system of primary forest corridors in the Imataca Reserve. Connecting sections of primary forest helps conserve biological diversity in exploited areas and presents an alternative to leaving remaining forest in isolated patches. Because commercially valuable trees are present only in low densities in the sectors selected for protection--mostly riparian areas--this will not adversely affect the economic interests of logging businesses.

As a result of our studies, forestry management plans for private company logging in the reserve will now include these corridors. The proposed system of corridors will also allow the Imataca's forests to be connected with other natural forest areas such as Canaima National Park, where Angel Falls is located.

Given the importance of bats to rain forests, the implications of reduced numbers of certain bats or the extinction of any bat species must be considered in forest conservation and management. Some species are highly vulnerable because of specific ecological requirements, such as habitat, food, or roosts. Known from only a few specimens, such bats have restricted distributions in relatively small forest areas, often under high development pressure. Consequently, a number of species need immediate attention and should be included in at least some of the IUCN Red Data Book categories.

One example is the rare leaf-nosed bat, Lonchorhina fernandezi, Venezuela's only endemic bat. Formerly known only from a small number of male specimens collected from a restricted area in the Orinoquia in the northwest Guiana Shield region, it was discovered when technicians with the Venezuelan Agriculture and Cattle Ministry were implementing a vampire control program. They applied the vampiricide poison, an anti-coagulant paste, to all captured bats, regardless of species; L. fernandezi was found among those pasted with the deadly substance. While this vampire control technique ultimately is the best approach, responsible guidance and training of technicians on how to distinguish vampires from beneficial bats must be implemented [BATS, Spring 1991].

Although we are making progress, there are many problems to be solved and questions to be answered. For example, what kind of biological processes influence the structure of bat communities in a rain forest? Why, in some areas, do several species show relatively low densities or abundances? What are the ecological requirements of these species? What criteria do we need to consider for their protection?

If we are to conserve lowland rain forest environments in Venezuela, ecological studies of fruit- and nectar-eating bats will be especially important in addition to ensuring that forest management plans include bats. Greater knowledge and awareness of bat roles will be critical in designing future programs to conserve biological diversity in tropical ecosystems. Rain forests simply cannot be utilized on a grand scale or conserved without attention to the unique needs of bats.

Jose Ochoa is a research advisor for the Sociedad Conservacionista Audubon de Venezuela, the Instituto Nacional de Parques, and the Corporacion Venezuelana de Guayana.

[footnote 1]
* This winter, through Texas A&M University's International Bat Research and Education Center, Bat Conservation International will participate in a conference in Venezuela to discuss the importance of education to the conservation of Latin American bats. In addition, BCI is donating several copies of their new Spanish-language audiovisual program, "Los Murcielagos de America Latina," for use in Venezuelan conservation education programs.

[footnote 2]
** Sturnira lilium, Artibeus literatus, Uroderma magnirostrum, Diclidurus spp., and some molossids.

[footnote 3]
*** Saccopteryx gymnura, Balantiopteryx infusca, Diclidurus isabellus, Micronycteris pusilla, Lonchorhina fernandezi, L. orinocensis, L. marinkellei, Rhinophylla alethina, Choeroniscus periosus, Scleronycteris ega, and Sturnira nana.

Above: Yellow-shouldered bats are among the most important fruit-eaters of the rain forest understory, each night dispersing large quantities of seeds, thus maintaining forest health. The fruit of plants in the genus Solanum, among the first to grow in disturbed and cleared areas of the forest, form a significant part of their diet.

As logging of rain forests changes plant diversity (above left), many animal species apparently cannot adapt to the new conditions. Tonatia sylvicola, an insectivorous gleaning bat (above right), is highly dependent on the primary forest for its survival. After forests are cut, these bats simply disappear.

The rare Lonchorhina fernandezi, Venezuela's only endemic bat, has come under increasing threat from forest logging and has also been a victim of indiscriminate vampire control. Its close cousin, Lonchorhina aurita, is shown here (below).

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