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The diversity of species, complexity and ecological importance of bats are unknown to most people.

Image: James Wainscoat on Unsplash

The word bat comes from the Latin, in which muris means mouse, and coecus, blind. In Greek, the name verpertilium is related to the nocturnal habit of these small mammals.

The symbology associated with these animals is varied. The early settlers' narratives of the existence of vampire bats in South America contributed to harmless species being seen in Europe as frightening and dangerous. However, there are several species of bat, each with different eating habits and great importance for ecosystems.

Ancestry and evolution

The difficulty of linking bats to any other group of mammals suggests a very ancient origin and obscure ancestry. The fossils found do not convey information about the initial period of evolution of bats, as they have delicate structures, which are not well preserved in forests.

The oldest complete fossil of a true bat was found in Eocene rocks (60 million years old) of the formation. green river from Wyoming in the United States.

It is speculated that bats evolved with the beginning of the diversification of flowering plants, which resulted in an abundance of insects. In this way, insectivorous mammals also established themselves and exerted strong predation pressure against the ancestors of bats, as they preyed on small mammals. For this reason, it is assumed that these bat ancestors were nocturnal, having evolved from a small, arboreal mammal.

Bat classification and diversity

• Kingdom: Metazoa
• Phylum: Chordata
• Class: Mammalia
• Order: Chiroptera
• Suborders: Megachiroptera and Microchiroptera

Bats are represented by two major suborders: Megachiroptera and Microchiroptera. In Brazil, these animals are also called andira or guandira by indigenous cultures. In addition, they represent the second highest order among mammals, being surpassed only by the order of rodents (Rodentia).

Because they have nocturnal habits, most bats primarily use echolocation to find their way around. It is a sophisticated biological ability to detect the position and distance of objects or animals through the emission of ultrasonic waves, in air or water. Therefore, bats have small eyes and large, well-developed ears.

During the echolocation process, they transmit high-frequency sounds through the mouth or nose, which are reflected by surfaces in the environment, indicating the direction and relative distance of objects. Bats also use sound for other purposes such as communication and mating. However, some sounds emitted by bats are not audible for the human species.

Megachiroptera bats are represented by the family Pteropodidae, which has 150 species distributed among tropical regions of Africa, India, Southeast Asia and Australia. Due to the similarity of their faces to those of foxes, they are popularly known as flying foxes. These bats use vision for navigation and therefore have large eyes. In addition, they do not have facial and nasal ornaments, as they do not have the echolocation system.

Microchiroptera are composed of 17 families and 930 species in the world. In Brazil, nine families, 64 genera and 167 species are known, which inhabit the entire national territory, including the Amazon, Cerrado, Atlantic Forest, Pantanal, the Gaucho pampas and even urban areas. Brazilian families are: Emballonuridae, Phyllostomidae, Mormoopidae, Noctilionidae, Furipteridae, Thyropteridae, Natalidae, Mollossidae and Vespetilionidae.

Among all mammals, bats have the most varied diet, feeding on fruits and seeds, small vertebrates, fish and even blood. Most are insectivores and the rest are basically frugivores. There are only 3 species that feed exclusively on blood, being called hematophagous. Therefore, bats contribute to the structure and dynamics of ecosystems, acting in pollination, seed dispersal, insect predation - among which many are agricultural pests - and nutrient supply in caves, but they are also agents of transmission of numerous wild diseases .

body structure

The greatest peculiarity of these animals, common to all species, is their ability to fly. The bat is the only mammal that moves through the air and, for that, uses its upper limbs (arms and hands) that biological evolution has turned into wings. The bone structure of the bat's hand is similar to that of the human hand. In bats, the phalanges are thin and long, almost the size of the body. The fingers are joined by an elastic membrane, which is also attached to the legs. To fly, just spread your fingers and move your arms up and down.

Although some mammals can glide over long distances, bats are the only group capable of true flight. In the course of evolution, thin, elastic membranes developed between their toes, stretching to the distal part of their legs, giving them maneuverability and making them great flyers.

As their wings have a large surface area, dehydration is faster than in other animals of the same weight. Therefore, bats need more water than other mammals of the same weight.

Bats have also developed the ability to hang for rest, upside down, clinging to cave surfaces, logs, and branches with their sharp, curved nails. The cervical vertebrae, just as they allow the head to remain up during flight, keep it up during rest so that the environment does not appear inverted.

For these nocturnal animals, a bright color would be of little use and, therefore, there are only variations in skin color between black and brown, with some red or yellowish species. Even so, white coats can occur, as in the species of Diclidurus.

Although there are several animals that can prey on bats, such as owls, hawks, falcons, raccoons, cats, snakes, frogs and large spiders, only one African eagle is really specialized in bats. The most surprising thing is that some bats feed on others, although they are not cannibals, as they capture species different from yours.

food

Bats are divided into seven groups according to their diverse eating habits. Among them are: carnivores, frugivores, hematophagous, insectivores, omnivores, piscivores, polynivores and nectarivores.

Carnivores are predators of large insects and small vertebrates, such as birds, amphibians, reptiles and even small mammals. Among Brazilian bats, carnivores are among the largest.

There are predominantly frugivorous bats, but they also include insects in their food. In Brazil, they belong to the family Phyllostomidae and are considered harmful to fruit trees because they attack the fruits of orchards in regions where all the forests have been destroyed. However, the damage caused by bats to the fruit industry is little or no relevance. Regarding their biological importance, frugivores play an important role in seed dispersal.

The hematophages feed exclusively on the blood of mammals or birds. To do this, these bats use their specialized incisor teeth to make small cuts in the animals. In the process, they release an anticoagulant with their saliva and sip the blood that flows out. Once sated, these bats separate the liquid part of the blood with their specialized kidneys and urinate, eliminating excess weight before returning to their shelters.

Insectivores capture most of the insects they feed on as they fly. Bats in this group act as controllers of insect populations, as many are harmful to crops or can transmit diseases such as dengue. Because they are at the end of the food chain, insectivores are subject to greater accumulations of insecticides and sublethal poisoning, which causes their sterility.

Omnivores are adapted to various eating habits. They feed on insects, pollen, nectar and fruits, and sometimes on small invertebrates. Piscivores are skilled at fishing. They live near watercourses and fish through echolocation.

Polynivores and nectarivores are bats of the family Phyllostomidae which extract carbohydrates from nectar and proteins from plant pollen, but which can also ingest insects. They are easily recognizable by their elongated muzzle and long tongue. Bats in these groups have specialized facial and body hair for carrying pollen.

Bat-borne diseases

Among bat-borne diseases, rabies and histoplasmosis are the most common.

Anger

Although rabies is common in vampire bats, an epidemiological study of human rabies carried out in the Amazon concluded that these animals have no significant role in the transmission of the disease. On the other hand, cattle-related rabies is more relevant, as 2 million heads were contaminated by bats in all Central and South American countries, except Chile and Uruguay, in 1972.

Disease control in ruminants should be done with an anti-rabies vaccine and with a reduction in the population of transmitting bats, the hematophagous. Given the little knowledge on the subject, it is common to incriminate all species of bats. For this reason, beneficial species are often unjustly accused and exterminated.

Histoplasmosis

Histoplasmosis is a systemic mycosis caused by the fungus Histoplasma capsulatum, an ascomycete that lodges in moist soils rich in bird and bat droppings . These feces have a high nitrogen content, which makes the soil pH acidic and creates the ideal ecological niche for this fungus.

The main sources of infection for H. capsulatum they are caves, chicken coops, hollow trees, basements, attics, unfinished or old buildings and rural areas. The contagion occurs mainly through inhalation of the fungus spores.

It is noteworthy that infection by Histoplasma capsulatum it is not restricted to caves and caves. Farmers, landscapers, gardeners, people who work in civil construction, raising birds and controlling pests are also exposed to the risk of being infected and developing the disease.

Covid-19

Although the new coronavirus pandemic vector is not known, all eyes are on the bat. These animals had already been the origin of other coronavirus epidemics. At the beginning of this century, they were the cause of the transmission of severe acute respiratory syndrome, better known as Sars, which infected more than 8,000 people.

In the mid-2010s, bats were the origin of another similar respiratory disease: the Middle East Respiratory Syndrome (Mers), responsible for infecting around 2,500 people. As for this new coronavirus, Chinese authorities believe it originated in a Wuhan market that sold seafood and meat from wild animals, including bats and vipers.

However, an analysis carried out by researchers in Scotland concluded that bats and rodents can transmit a multitude of viruses to the human species. According to ecologist Daniel Streicker, from the University of Glasgow, the amount of virus is proportional to the number of species contained in these groups. Therefore, he advocates broader studies that are able to identify threats from animal sources in several species, not just in a specific group. The ideal would be to focus on regions of high biodiversity.

The vice president of EcoHealth Alliance, Kevin Olival, also believes the finding that species diversity corresponds to viral richness is a compelling reason to expand surveillance on bats, rodents and other groups of mammals.

Reproduction and habitat

On average, bats have one young per year, which they take care of for three months. Pregnancy lasts from 44 days to 11 months and birth occurs at the time of greatest food supply.

In preserved areas, bats shelter in caves, rock burrows, tree hollows, trees with trunks similar to their coloration, leaves, fallen trees, roots on the banks of rivers and termite mounds. In Brazil, in urban areas, it is possible to find bats on bridges, in the lining of buildings and masonry houses, in fluvial pipes, in abandoned quarries, inside barbecue grills and even in air conditioners.

Importance

Bats are extremely useful to humans, serving them as research material in epidemiological, pharmacological, disease resistance mechanisms and vaccine development studies. They also serve as a food resource for some peoples in Africa and even for some tribes in Brazil.

They are often considered harmful because of the diseases they can carry and transmit, such as viruses and mycoses.

Preservation

In Brazil, there is legislation that guarantees the protection of bats. Even so, little has been done for its conservation. Currently, five species from two families are listed as endangered: Family Phyllostomidae - Lonchophylla bokermanni, Lonchophylla dekeyseri, Platyrrhinus and family Vespertilionidae - lasiurus ebenus and Myotis ruber.

An enlightened society should carry out an unbiased wildlife conservation program that does not only include animals that are popular with the public. Bats are threatened by insecticides, deforestation and even legends and superstitions about them.