Know More about Bat Animal Including the Bat Classification

Bat belongs to the order Chiroptera. Chiroptera is the only mammalian group that can fly. Moreover, bats can navigate during the night by using an acoustic orientation system called echolocation. Due to such unique characteristics, bats are considered as one of the diverse groups of mammals. Scientists have discovered around 1200 species of bats, amongst which many are abundant.

For example, a recent study suggested that around 100 million Mexican free-tailed female bats make nursery colonies in summer for Texas. In these colonies, they give birth to about 100 million infants in five huge caves. The number of male members of this population equals the number of female members. However, not all members of this population venture into North Texas and prefer to be spread out in the tropical parts of America. All these numbers count for only one species so that it can be understood the total population of all the bat species.

General Features about Bats

Although all bats look similar in their flight movement, there are subtle differences amongst them. There are some general bat characteristics, while some are related to certain species.

• The similarity lies in the fact that all bats expand their wings to take off for flight. However, these bats differ in the size of their wings. Based on their wing sizes, bats can be classified into Megachiroptera and Microchiroptera. Megachiroptera are the Old World fruit bats that appear larger in size.

• However, the Microchiroptera are the smaller bats found worldwide. However, there are non-bat members of the Megachiroptera family. They are the flying foxes (Pteropus) who have an average weight of 2.2 pounds (1 kg) and a wingspan of 5 feet (1.5 meters). Amongst the bat family, the largest bat that devoured insects is the hairless, naked bat (Cheiromeles torquatus). The spectral bat (Vampyrum spectrum) is the largest carnivorous bat in the world. They are also called the tropical American false vampire bat. They have a wingspan of 24 inches (60 cm).

• The bumblebee bat with the tiny hog shaped nose (Craseonycteris thonglongyai) is considered the smallest mammals. They are native to Thailand. They have an average weight of 2 grams and have a wingspan of 6 inches (15 cm).

• Not only wingspan and weight, but bats vary in terms of the texture of fur and color. The facial appearances of the bat represented by the ears and the muzzles also vary between family and genera. In most families, the nose leaf, a complex fleshy surrounding of the nostrils, is present. Most scientists predict that these nose leaves help in directing the way of outgoing calls for echolocation.

• Also, the wing proportions in bats are modified according to the flight mode. The membrane between the legs and the tail also differs amongst bats and can be considered a result of flight, roosting, and feeding adaptations. They also vary in the postures they achieve during roosting, especially when they cling to the wall or are suspended from top support. They also differ in the manner they use or fold their wings.

Distribution of Bats

Bats are mainly found in tropical climates. Scientists have found above 30 genera comprising of around 100 species of bats in West Africa. They have also cataloged around 19 genera comprising 45 species of bats in the United States. Amongst the 18 families of the bat, the vesper bats ( belonging to the family Vespertilionidae), horseshoe bats (belonging to the family Rhinolophidae), and the free-tailed bats (belonging to family Molossidae) are found in the temperate zones.  Another member of the temperate zone bats is a few American leaf-nosed ones (belonging to the family Phyllostomidae). Some vesper bats are also found in Canada.

Know the Bat Classification

• Taxonomic Features

Bats are classified by several taxonomic features, which constitute the bat lower classifications. All the members of the order Chiroptera have marked pectoral specialization and elongated finger bones to support their flight. Another feature of order Chiroptera is the weak development of legs and pelvic regions. They have reduced ulna on their forearm. Claws are present only on the thumb and on the second finger on some species. The bats have outward and rearward directed knees. They have a minimum complement of permanent teeth of 20 and a maximum of 38.

• Annotated Classification

The annotated classifications for the bat are focussed on Mammal Species of the World (third edition), edited by DeeAnn M. Reeder and Don E. Wilson. However, more species have been added to the list upon their discovery and analysis of DNA.

Order Chiroptera

Amongst the members of the order Chiroptera, all the 1116 species are divided into 18 families and two suborders. The suborders are Microchiroptera and Megachiroptera. The suborder Microchiroptera consists of the family Phyllostomidae (e.g., vampire bats), Vespertilionidae (vesper bats), Rhinolophidae (e.g., horseshoe bats), Molossidae (e.g., free-tailed bats), Hipposideridae (e.g., Leaf-nosed bats-Old World), Nycteridae (e.g., slit-faced bats), Emballonuridae (e.g., sheath-tailed bats), Megadermatidae (e.g., false vampire bats), Mormoopidae (e.g., leaf-chinned bats), Natalidae (e.g., funnel-eared bats), Thyropteridae (e.g., disk-winged bats), Rhinopomatidae (e.g., mouse-tailed bats), Furipteridae (e.g., smoky bats), Mystacinidae (e.g., New Zealand short-tailed bats), Noctilionidae (e.g., bulldog bats), Myzopodidae (e.g., sucker-footed bats- Old World),  and Craseonycteridae (e.g., bumblebee bat).

The suborder Megachiroptera consists of only one family, Pteropodidae, and this family consists of the fruit bats of the Old World and the flying foxes. These animals are mainly found in the tropical and subtropical regions of the Old World, which includes several Pacific islands. The characteristics of these animals include small ears, large eyes with well-developed vision, large size, and show colonial behavior.

Bat Body Parts

• Belonging to the mammalian group, bats share several mammalian characteristics. However, they have well-defined characteristics of their own. They have two sets of limbs, where their front limbs are modified into wings for flight. The thoracic region is large with well-developed muscles. The muscles help to provide power and support to the wings. Additionally, they have slender legs and hips since these body parts are not used to support the body’s weight.

• The other features of the bat body include the wing shape, which shows diverse variety in terms of the relative length of fingers and forearms. All the fingers except the thumbs are elongated with a membrane present in between their fingers. This membrane extends to the side of the legs and body from the posterior border of the upper arm and forearm. This membrane consists of two skin layers that are hairless and darkly pigmented. They also contain nerves and blood vessels. When the wings are not extended, they are folded with the help of muscle fibers and elastic connective tissues. The third finger, and sometimes other fingers, can fold over when the bat is not flying.

• In most cases, the wings fold into the undersurface of the body. Some species of bats use their thumbs for climbing or walking, while others use them for holding food. Sometimes, the thumb and the index finger have claws. They even have suction disks or pads on their thumbs and wrists. Some female bats use these pads to form a hammock when they give birth to their offspring.

• Some bats have a membrane between their legs as well. This membrane is called the interfemoral membrane. The tail supports this membrane along the midline. This membrane is properly developed in carnivorous, insectivorous, and fish-eating bats. 

• The ear is the most striking feature of a bat in its resting position. The necks are generally short and cannot be moved. The external ear of the bats has a projecting portion that can be funnel-shaped. Some bats who feed on terrestrial arthropods have oversized ears. These ears are highly mobile and can be flicked back and forth in different directions.  

• Bats have a fox-like or rodent-like face. They might also have a puglike appearance. The nectar feeders have an elongated snout and extensible tongue. Several bat species have nose leaf made up of the skin and connective tissue. Several bats have large-sized dermal glands, although they differ in their location in the body. The secretions from these glands function as pheromones in several species. Pheromones are sex recognition signals in some bats. These glands might also secrete oil for waterproofing their fur or conditioning their skin.

Bat Food Habits

• Bats can also differ based on their food habits. Several bats are insectivorous. The best way to understand the prey species is by studying the discarded pieces of food found under the night roosts. Bats use echolocation to detect their prey. The larger insect prey are caught with the help of wing membranes and pulled into the buccal cavity. Bats generally feed on arthropods like spiders, scorpions, or large insects. Bats prefer to land on their prey and kill them before picking them up with their teeth. Bats can also hold their prey in their mouth while flying.

• Both Myotis and Noctilio have one species that feed on crustaceans and small fishes. These fish-eating species also have flying insects. These bats have large hind limbs and sharp claws to catch the fishes.

• One important feature about the bats belonging to the order Megachiroptera and several Phyllostomid genera is that they feed on brown or green fruits. These fruits hang far from the main trunk of the trees and can have a musky odor. The Macroglossinae subfamily of the Old World fruit bat feeds on the pollen and nectars. These bats pollinate tropical flowers during their feeding activity. These flowers generally open at night and are white in color. They even have a rotten, sour, or mammalian odor that grows on pendulous branches or wood. The Glossophagine bats can also feed on flowers.

• Several genera belonging to megadermatidae or phyllostomidae are mainly carnivorous. They feed on other bats, shrews, small rodents, tree frogs, lizards, and sleeping birds. The actual vampire bats feed on the blood of larger mammals and birds. They attack the exposed regions of the skin on the victim- generally around the anus, nostril or the ear edges, and even the toes. They make a superficial, scooping bite on the body, ensuring that the blood comes out freely. They take in the blood with specialized movements of the tongue. The vampire bats take in around 15 ml of blood every night.

• The food habits of the bats have several ecological impacts. Several plants require bats for pollination. Other plants require bats to disperse their seeds. A recent study shows that two families of moths use the bat pulses to understand heavy predation nearby and take several actions to evade such danger or protect themselves from it.

Locomotion

All bats consider a flight to be their primary mode of locomotion. Some groups like free-tailed bats prefer to fly at high altitudes or in open spaces. Their wings are narrow and long and adapted to swift flight. They also have a big turning radius.  The slit-faced bats and the false vampire bats have similar hovering actions when they feed on flowers or pick prey from vegetations. These bats have broad, short wings with a small turning radius adapted for slow flight.

Some bats take off from the ground easily, for example, the genus Macrotus by simple flapping, while the vampire ones first leap in the air and then spread their wings to fly. The free-tail bats first take off, then fall before they become airborne. Therefore, one can understand that the bats vary greatly in the type of flight that they undertake.

Recent studies have revealed that the dual nature of bats, both terrestrial and airborne, has important significance in determining their immunity. Bats harbor several pathogens that do not affect them. Some of the pathogens include Hendra virus, Rabies virus, and lyssavirus. Several of these pathogens have proved to be detrimental to human health.

Several ongoing types of research are still going on with bats. They are an important subject to study because of their unique adaptations, lifestyle, food habits, locomotion, body structure and immunity. It is an important study for all students to have an idea about unique adaptations of bats, which can be used to understand how to adapt to nature’s variations.