BATS: CHARACTERISTICS, MORPHOLOGY, BEHAVIOR - BIOLOGY - 2025

The bats are mammals belonging to the order Chiroptera whose forelimbs, which were adapted as wings, will allow sustained flight. Members of this species are the only mammals with the ability to fly, being able to reach speeds of up to 160 km per hour.

Because their skeleton is very delicate, they did not fossilize well. The oldest fossil is Onychonycteris, which lived 52.5 million years ago, during the Eocene

The great flying fox (Pteropus vampyrus). Source: pixabay.com

Bats are distributed in a wide variety of regions on Earth, with the exception of the Arctic, Antarctica, and some oceanic islands. They are usually found in crevices, caves and in a kind of "tents" that they build using leaves. Their diet varies, they can eat insects, fruits and some, like the common vampire, feed on blood.

Most bats make sounds to create echoes. Your nervous system compares these impulses, creating an "image" of the environment where you are. Thanks to this they can locate their prey in the dark.

Some species are sensitive to the Earth's magnetic field, which is known as magnetoreception. This makes it easier for them to orient themselves on night flights.

Bats and man

Bats provide humans with various benefits. Their manure, which has a high percentage of nitrates, accumulates massively in the places where they live, forming guano. This is extracted from caves and is used as a natural fertilizer.

The positive impact that the use of guano brings in agriculture is invaluable, because it significantly reduces environmental pollution, by reducing the use of chemical fertilizers.

Bats help spread plant seeds and pollinate flowers. In addition, since insects are included in their diet, they reduce the need to use pesticides to control pests in a field.

The caves they inhabit, where they are usually found in very large groups, can become tourist attractions in a region, representing an important economic income.

In some regions of the Asian and African continent, they are used as food, in special dishes of the local cuisine.

However, not everything is beneficial. Bats are natural carriers of rabies, and because they move through various geographic areas and are long-lived, they can easily spread this serious disease.

General characteristics

Size

Its size is varied. The smallest species, the pig-nosed bat, measures between 29 and 33 millimeters, weighing approximately 2.5 grams.

The largest bats, including the Philippine flying fox, could weigh 1.6 kilos and measure 1.5 meters in front, with their wings understood.

Skull

The shape of the head may differ in each species. In general, they have large eye sockets and their snouts are long, which may be associated with a diet based on flower nectar. In vampires, the snout is reduced to make way for large incisor and canine teeth.

Teeth

Small, insect-eating species may have up to 38 teeth, while vampires only have 20. Specimens that eat insects with shells have fewer teeth, but their canines are long and have a robust lower jaw.

Wings

In the process of embryonic development, the bat's front leg toes are extended, creating specialized limbs for flight.

With the exception of the thumb, the phalanges of the front legs are elongated in order to support a thin, wide and flexible membrane of skin called the patagium, which allows it to stay in the air.

Ear

The ears of bats have, on their inner surface, a very specific geometry that helps them focus the echolocation signals and listen to any other sounds produced by the prey.

View

Some species have poor visual acuity, but they are not blind. Most have mesopic vision, detecting only light at low levels, others have photopic vision, allowing them to see objects in color.

Taxonomy

Animalia Kingdom. Edge: Chordata. Class: Mammalia. Subclass: Theria. Infraclass: Eutheria. Clade: Boreoeutheria Epitheria. Superorder: Laurasiatheria.

Traditionally, based on morphology and behavior, the Chiroptera order was divided into two suborders: the Megachiroptera and the Microchiroptera. But recently the investigations yielded results of a new subdivision proposal.

Morphological, behavioral, molecular and fossil evidence has led researchers to propose the subdivision of this order into Yincopiochiroptera and Yangochiroptera. These new suborders are supported by statistical evidence and by phylogenetic analysis based on the sequence of the genome.

Traditional taxonomic hierarchy

Chiroptera Order

Sub order Megachiroptera (Dobson, 1875)

-Family Pteropodidae.

Sub order Microchiroptera (Dobson, 1875)

Superfamily Emballonuroidea

-Family Emballonuridae.

Superfamily Molossoidea

-Families: Antrozoidae, Molossidae.

Superfamily Nataloidea

-Families: Furipteridae, Myzopodidae, Natalidae.

Superfamily Noctilionoidea

-Families: Mormoopidae, Mystacinidae, Phyllostomidae.

Rhinolophoidea Superfamily

-Families: Megadermatidae, Nycteridae, Rhinolophidae.

Rhinopomatoidea Superfamily

-Family Craseonycteridae.

Superfamily Vespertilionoidea

-Family Vespertilionidae.

J erarquía modern taxonomic

Chiroptera Order

Sub order Yangochiroptera (Koopman, 1984)

Emballonuroidea super family

-Families: Emballonuridae, Nycteridae.

Super family Noctilionoidea

-Families: Furipteridae, Mormoopidae, Mystacinidae, Myzopodidae, Noctilionidae, Phyllostomidae, Thyropteridae.

Super family Vespertilionoidea

-Families: Cistugidae Miniopteridae, Molossidae, Natalidae, Vespertilionidae.

Sub order Yincopiochiroptera (Springer, Teeling, Madsen, Stanhope and Jong, 2001)

-Family Pteropodidae.

Rhinolophoidea super family

-Families: Craseonycteridae, Hipposideridae. Lydekker, Megadermatidae, Rhinolophidae, Rhinopomatidae.

Morphology

As it is the only vertebrate that flies, its body is adapted for this, especially in the formation and structure of its skeleton.

Bat bones are light and thin. Those that make up the skull are fused, allowing greater luminosity. They have a keel on their sternum, where the pectoral muscles that help raise and lower the wings during flight are anchored.

The wing membrane is supported by the arm and by the 4 fingers. This membrane extends to the hind legs and tail, where a flap is formed, which helps the animal to take prey that it will then take to its mouth.

The first digit on the wing of this mammal is small and has claws that are used for climbing trees or walking on land.

The skin that covers the body of the bat has two layers: the epidermis and the dermis. In addition, it has hair follicles, sweat glands, and a subcutaneous fatty tissue.

Around their mouth and nose they have fleshy parts whose function is to direct and control the echoes sent by the bat, which allow it to "scan" the area where they are.

Rest

While bats are not flying, they hang upside down by their feet, a pose known as resting. Some species do so with the head bent towards the belly, others rest with the neck turned towards their back.

To achieve this position they use the tendons found in their heels, which are directly attached to the body. Due to the force exerted by the weight of the body, the tendon remains closed, without any muscle intervening.

Behavior

Social structure

Some specimens are solitary, while others form large colonies. This form of grouping allows them to reduce the risk of predation to which they are subjected.

Bats that have their habitat in temperate zones migrate when temperatures begin to drop. These hibernation sites are used for reproductive adults to mate with their peers from other groups.

When they are grouped together, relationships such as food exchange and hygiene are established between them.

Cooperation between males

There is evidence of some alliance behaviors between males, in order to monopolize the females. In dominant polygynous species, males can tolerate the presence of less dominant males, which will help keep dominant males away from other groups.

In exchange for this, subordinate males may have greater access to females and greater possibility of acquiring a more dominating status. These alliances could last around two years.

Defense of the young

Mothers have special vocalizations, known as isolation calls, that allow them to find, recognize, and retrieve their young when they have fallen. It is very common for the hatchlings to fall to the ground, but they will die if they do not recover.

In studies carried out it was evidenced that mothers found their young through these calls, which they inspected up to 342 times. If they don't, the other females in the group could bite them and drag them to their deaths.

This behavior is typical of females, since the males completely ignore the fallen young.

Communication

Bats emit long-range, low-frequency sounds. These are used in cases of fights for food, to make a call to the group inviting them to sleep and to find a partner. These animals diffuse different sounds to communicate with single bats, especially if it is of the opposite sex.

During the flight they make vocalizations that warn others how the "traffic" is. In this sense, bulldog bats (Noctilio albiventris) warn when they perceive a possible collision with another specimen.

Communication also occurs by other means. The Sturnira lilium species has a gland on its shoulders that secretes a specific scent during the reproductive season.

The bats of the species Saccopteryx bilineata have a kind of sacs on their wings, where secretions such as saliva mix, creating a perfume that they spray on the places destined to rest. This behavior is known as salty and is usually accompanied by a song.

Birth

A few minutes after birth, the baby looks for the mother's nipple and begins to breastfeed, for an approximate period of two months, until they fly on their own and get their food.

In this period, the mother requires a great deal of energy, because in addition to nursing the baby, she must carry it on her back or hanging on her belly. This is because the wings of newborns are not functional until a few weeks later.

The young are born hairless, blind and defenseless. They cling to the mother in search of warmth.

At birth, small bats have teeth, reaching up to 22 of them. They grow very fast in size and you quickly develop their wings and fur. At two months, the young is completely independent, being able to fly alone, moving away from the mother to defend themselves.

In the vast majority of bat species, the females are the primary caregivers of the young. However, in some cases the males play an active role, building shelters and defending the mother and the young.

Circulatory system

Bats have a heart made up of four cavities, their circulation being double and complete. The circulation is divided into two: pulmonary and corporal, each of these being independent.

In addition, venous and arterial blood never mix in the ventricles, in the right there will always be blood without oxygen and in the left, oxygenated blood. Blood always circulates through blood vessels.

Your circulatory system has special valves that prevent blood from pooling in your head.

The muscles used by the bat to fly require more energy than the rest of the body's musculature. Along with this, the required oxygen levels in the blood are also high. Therefore, the circulatory system must be efficient, so that it meets the requirements of the animal.

Compared to other mammals, the bat's heart could be up to 3 times larger, pumping much more blood. A bat in flight is likely to reach a heart rate of 1000 beats per minute.

Thermoregulation

The vast majority are homeothermic, having a stable temperature throughout their bodies. However, there are species that are heterothermic, whose body temperature may vary.

The organism of bats has a high degree of thermal conductivity. Its wings have blood vessels, losing heat when it extends and moves while flying. This is why they avoid doing it during the day, so as not to overheat their body due to solar radiation.

These animals have a system of sphincter valves near the arteries that make up the vascular network, located at the edge of the wings. When they are open, oxygenated blood flows through the network, if they contract, the blood is diverted to the capillaries. This allows you to release heat while you are flying.

Respiratory system

Animals that belong to this group of mammals have an efficient respiratory system, adjusted to the requirements of the organism during prolonged flight. This is necessary because extra energy and a continuous supply of oxygen are needed to ensure the functionality of each organ.

This implies modifications in some organs that make up the respiratory system. Some of these are the reduction of the thickness in the blood-brain barrier, increase in the volume of the lungs and changes in the geometry corresponding to the bronchial tree.

The fact that the lungs are larger, increases the gas exchange surface and with this the effectiveness of the breathing process. Along with this, these organs have their own characteristics that prevent them from flying at high altitudes.

Furthermore, the structure of the bronchioles and pulmonary alveoli results in a wider exchange surface, thus increasing the bat's respiratory capacity.

The wings are made up of a very thin membrane, which has subcutaneous vessels very close to the surface. This greatly contributes to the efficiency of the oxygen and carbon exchange that takes place in the respiratory process.

Reproduction

Male Sex Organs

In males, the sexual organs, present in almost all species, are: epidymis, ampullary gland, seminal vesicle, prostate, Copewer's gland, urethral and para-anal glands, testes and penis.

Penis

There are variations in the posture of the penis: caudal or cranial. Despite this, they have common characteristics, such as being enclosed by an ischicavernosus muscle.

The skin of the glans, which often has dermal spines, is usually covered by a foreskin, which usually has additional erectile tissue. Almost all species have a baculum, with variations in shape and size between each family.

Location of the testicles

• Permanently abdominal: in some species this organ is kept in the cavity of the abdomen.
• Permanently inguinal or scrotal: this type of testicle is present in the Taphozous longimanus. In those species that do not have a scrotum, the testes are inguinal (Pteronotus parnelli).
• Migratory: the testes of some specimens may migrate from the abdomen to the scrotum, through the inguinal canal.
• External: there are species where the testicles are found on the crest of the pubis, near the base of the penis.

Female sexual organs

Females have two ovaries, two oviducts, the gestational portion of the uterus, the cervix, and the vagina. There are functional differences between each specimen. For example, when ovulation occurs frequently in the same ovary, it tends to be larger.

Types of uterus

• Duplex: has two separate tubes, often joined externally at the cervical end.
• Bicorneal: it has two horns, which can join caudally, forming a uterine body, which joins the vagina through a cervical canal.
• Simple: it has a single body, communicating with the vagina through the cervical canal.

Mating and gestation

Bats usually reach their sexual maturity between 12 and 14 months of life, the mode of mating varying between each species. Some of them are promiscuous, being able to join a male with several females, managing to maintain and defend “harems” of females.

Other species, such as the Vampyrum spectrum and Nycteris hispida, are monogamous. In this case, the male, the female and their offspring live together in family groups, all collaborating protecting and feeding the offspring.

Courtship as a mating behavior exists among the vast majority of bats, however, in some species it does not occur. Before copulation, the male can woo the female by gently biting her neck or rubbing his head against hers.

The female has specific behaviors when it comes to the mating and birth of the young. In order for them to have a better chance of survival, she considers having high levels of food, as well as having favorable environmental factors.

For this reason, the female may delay the internal process of fertilization of the eggs. She can store sperm in a reproductive tract or it could also delay the implantation of the egg.

When female bats are ready to give birth, they usually congregate in maternity colonies. These colonies vary in size, being able to house up to 20 million bats in a cave.

References

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