понедельник, 23 декабря 2013 г.

12 images and facts about misunderstood bats

12 images and facts about misunderstood bats
12 images and facts about misunderstood bats

Bat flying by trees in a jungle
Due to their love of fruits and nectar, bats play a vital role in pollination and seed-spreading. (Photo: kajornyot/Shutterstock)

Bats can be a little scary-looking, but these winged mammals are as varied and interesting as we humans are. Below are 11 facts about these environmentally valuable creatures.

1. Bats account for about 20 percent of all mammal species

Painted bat of southest Asia
The painted bat of Southeast Asia, like many other microbats, relies on echolocation to find food. (Photo: PITOON KITRATANASAK/Shutterstock)

With more than 1,200 species included in the order Chiroptera, bats represent one of the largest orders of mammals. They are surpassed only by the order Rodentia, which boasts a whopping 2,277 species — 40 percent of all mammalian species.

Chiroptera is separated into two suborders: Megabats and microbats. Megabats, commonly known as fruit bats or flying foxes, have excellent vision and feast on fruit and nectar. Microbats, like the painted bat of Southest Asia (Kerivoula picta) (pictured), are characterized by their use of echolocation and an appetite for insects or blood.

2. Bats are found across the planet

Bats flying in a large pack at sunset
Bat thrive in every continent on Earth except for Antarctica. (Photo: Sarun T/Shutterstock)

Like birds, flight has allowed bats to travel and settle in all corners of the Earth, with the exception of the Arctic and Antarctic. Bats generally roost in caves, crevices, foliage and man-made structures like attics or under bridges.

At least 45 species of bats are present in the United States alone, with the most common species being the little brown bat, the big brown bat and the Mexican free-tailed bat.

3. Microbats use echolocation to hunt prey

Close-up of a Mediterranean horseshoe bat
The Mediterranean horseshoe bat's nostrils help it focus on soundwaves. (Photo: Ivan Kuzmin/Shutterstock)

Although microbats are not blind, their true perceptive strength lies in their ability to use echolocation, also known as biosonar.

As bats forage for food, they emit a continuous stream of high-pitched sounds audible only to other bats. When the sound waves collide with a nearby insect or object, the interrupted waves echo back, generating an acute sonic vision of the bat's surroundings. This ability is so sensitive that it can detect objects as thin as a single human hair.

Some species are equipped with specific characteristics that allow for more fine-tuned biosonar readings. For example, the Mediterranean horseshoe bat (pictured) is named for its peculiar, horseshoe-shaped noseleaf — a fleshy, complex structure surrounding the nostrils that helps focus sound waves. Likewise, long-eared bats possess prominent ears with geometric inner ridges that sharpen echolocation signals and allow for passive listening of sound produced by prey, such as the fluttering of moth wings.

Bats aren't the only animals that can use biosonar. Shrews, dolphins and some cave-dwelling birds also use echolocation to navigate their surroundings and hunt for prey.

4. Bats 'waggle' their heads to hear better

You know how a dog cocks its head as if to better understand what a human is saying? Well, bats do the same thing, only they do it while they're flying. As you can see in the video above, the motion is similar to what dogs, cats and even humans do, but bats do it for a different reason: to fine tune the location of prey as they're echolocating.

The Christian Science Monitor — which artfully compares the motion to a tiny flying puppy — explains the research of Melville Wohlgemuth of Johns Hopkins University. Wohlgemuth, a neuroscientist whose specialty is echolocation, sums it up relatively simply. The bat has to sort out the clutter, and turning its head allows it to do that.

5. Bat colonies save billions of dollars a year in agricultural pest control

Gray long-eared bat against a white background
Bats are natural and environmentally-sound form of pest control. (Photo: Eric Isselee/Shutterstock)

There's no need to use harmful pesticides when you have a robust colony of bats nearby. A single bat can eat more than 600 bugs an hour — making bats a perfect choice for organic pest control. Without them, humans might as well be bowing down to insect overlords.

The agricultural value of these flying mammals cannot be overstated, but scientists predict this could all change within the next decade as North American bat populations face an uncertain future as a result of emerging threats — from habitat loss to disease.

6. Female bats can control when they get pregnant and give birth

A newborn bat rests on a human's hand
Bats can delay the development of a fetus so a birth can coincide with high production of fruit or insects in the environment. (Photo: Mnolf/Wikimedia Commons)

To ensure external conditions are optimal for a newborn bat, mother bats are equipped with a variety of biological tactics that allow them to put off fertilization, implantation or development of the fetus.

In some species, mating will occur in the fall, but females will store sperm in their reproductive tract before finally fertilizing their eggs when spring arrives. In other species, the egg is fertilized immediately after mating, but instead of implanting to the wall of the uterus, it floats around until favorable conditions arrive. Yet another adaptation exhibited in some bats is delayed fetus development, in which fertilization and implantation occurs as usual, but the fetus remains in a dormant state for a long period of time.

These tactics, which contribute to the slow birth rate of bats, are timed to coincide with high production of fruit or insects in the environment.

7. Yes, some bats live off blood

A vampire bat in a cave bares its teeth
Even the famed vampire bat doesn't actually suck its prey blood. It does lap the blood up with its tongue, though. (Photo: Michael Lynch/Shutterstock)

However, contrary to popular belief, vampire bats don't actually suck blood. Instead, they use their razor sharp teeth to make a small incision in the skin of a sleeping animal and then consume the blood as it runs from the wound.

Unlike the monsters of popular vampire lore, bats only require approximately two tablespoons of blood a day, so the victim's loss of blood is negligible and seldom causes harm. Additionally, bat saliva has a similar anesthetic quality to that of a mosquito, which helps prevent the victim from even feeling the cut.

8. Megabats prefer a vegetarian lifestyle

Black flying fox bat hangs upside down in a tree
Despite their reputation for blood lust, many bats, including the black flying fox pictured here, prefer fruits and nectar. (Photo: EcoPrint/Shutterstock)

About 70 percent of all bats are insectivores (with the exception of a small percentage that drink blood or eat fish), but megabats are mostly frugivores that feast on fruit, pollen and nectar.

Also known as flying foxes, these fruit bats play important roles in the pollination of flowers and the dispersal of fruit seeds. Their dietary habits are beneficial for rainforests, which contain a large variety of flora available for consumption.

Unfortunately, due to deforestation and the inherently fragile state of rainforest ecosystems, nectar-feeding bats are especially prone to extinction.

9. Bats hang upside down to conserve energy

Fruit bat hangs upside down from a tree
The nature of bats' circulatory systems means that they don't experience the same side effects of hanging upside down like humans do. (Photo: gallimaufry/Shutterstock)

If humans hung upside down from a tree for several hours, it wouldn't take long before they passed out. So, how do bats manage it?

For starters, human and bat circulatory systems are fundamentally different. Because our blood pumps in the direction of our brain, the stress of gravity transfers even more blood to the head when upside down. A bat's circulatory systems pumps the opposite way — away from its head. Also, while all mammals have valves in their veins that prevent blood from flowing backwards, bats possess these valves in their arteries, as well. All of these adaptations ensure that blood is evenly distributed throughout the bat's body.

It also just happens to be more energy efficient for bats to hang by their feet. As opposed to defying gravity and standing upright, no energy has to be expended while hanging due to the lightweight structure of their leg muscles and bones that were developed for flight.

10. Bats are the only mammals that can truly fly

A bat flies through the air, wings spread wide open
Sorry, flying squirrels. Bats are the only mammals capable of actual flight. (Photo: Erik Zandboer/Shutterstock)

While some mammals like flying squirrels, sugar gliders and colugos can glide through the air for short distances, bats are capable of true, sustained flight.

Unlike birds, which move their entire forelimbs, bats fly by flapping their webbed digits. The membrane of the wings is sensitive and delicate, and while it can be easily ripped, it can just as easily regrow.

11. Bats often share their home with thousands or even millions of other bats

Bats hang in a group along a rockface
Bats like to hang out together in their habitats. (Photo: Meaning/Shutterstock)

The world's largest natural bat colony is the Bracken Bat Cave in Texas, which houses 20 million bats. Over the course of one night, the entire colony can consume a whopping 200 tons of bugs. There's so many bats that when they collectively depart their cave to go foraging, a dense cloud composed of their bodies is visible on weather radar.

The site of the world's largest urban bat colony is in Austin, Texas, where up to 1.5 million Mexican free-tailed bats roost underneath the Ann W. Richards Congress Avenue Bridge. After spending their winters in Mexico, the bats migrate to Austin from March to November, during which they put on a nightly show for residents and tourists eager to witness them taking off to forage for food.

12. White nose syndrome is wreaking havoc on America's bats

Fuzzy bats sleep in a pile on the ground
Little brown bats are the most at risk when it comes to white nose syndrome. (Photo: Boyan Dimitrov/Shutterstock)

In February 2006, a caver exploring Howe Caverns near Albany, New York, discovered white fungus accumulating around the muzzles of hibernating bats. The disease spread rapidly over the next several years, and is now documented in more than 115 bat colonies across the eastern half of North America.

With a mortality rate of 95 percent, white nose syndrome is responsible for the deaths of at least 6 million bats. Although the fungus has been identified as Geomyces destructans, scientists remain stumped about how to stop it from infecting more bats.

Unless scientists are able to find a solution, the little brown bat, the most common bat species in North America, is on track for extinction.

This story was originally published in May 2013 and has been updated with more recent information.

Original article and pictures take http://www.mnn.com/earth-matters/animals/stories/bat-pictures-11-images-and-facts-about-a-misunderstood-creature site

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