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24 May 2017
Evening Sedition

A Pre-Prandial Stroll Whets the Appetite

Vampire Bat Locomotion

Montage of Vampire Bat Locomotion

It turns out that Republicans aren't the only bloodsucking species capable of two-legged locomotion:

Vampire bats' thirst for blood has driven them to evolve an unexpected sprinting ability. Most bats are awkward on the ground, but the common vampire bat can bound along at more than 1 metre per second."

"Vampire Bats Have a Clear Run" by Narelle Towie, Nature, 16 March 2005

The video (QuickTime) — also available from the author's Website at Cornell — illustrates their remarkable gait:

Not only are vampire bats unusual because they run, but also in the way that they power their gait. "Unlike most animals which use their hind legs as a source of power, these exceptional creatures power their run with their forelimbs," Hermanson explains. Getting most of the push from their long forelimbs -- actually their wings and therefore very strong -- the bats run more like a small gorilla than a comparable four-legged creature like a mouse. They run up to about 2.5 miles per hour. Although many of the 1,100 species of bats are known to walk, the common vampire is the only one so far to pass Riskin and Hermanson's treadmill test and break into a running gait.

With the introduction of large herds of livestock into their native environments of Central and South America, these bats don't need to hurry to catch the cattle from which they extract perhaps a tablespoon of blood at a time for sustenance. They feed while their prey are sleeping, spending perhaps 10 minutes drinking from the small cuts they make. However, running may help them avoid being stepped on, Riskin suggests. More likely, the researchers say, the ability to run evolved long ago, when vampire bats had to prey on faster South American athletes such as the agouti, a rodent about the size of a hare, which might wake up and take a swipe at the nocturnal visitor. It remains unclear exactly what the native prey were before the introduction of cattle, he adds.

"Unlike other bats, vampire bats keep out of trouble by running, Cornell researchers find" Cornell University News Service, 17 March 2005

How did this behavior evolve? Well, it reduces the energy needed to feed:

In the wild, vampire bats feed on the blood of large animals such as cattle, horses and pigs. They sneak up over the ground and make small incisions in the skin (usually the heel) of sleeping prey.

"Bats take a long time to feed," explains Colin Catto of the London-based Bat Conservation Trust. "If they were trying to hover for all that time they would expend an awful lot of energy."

The bats are most likely to run when moving between animals, and may have acquired the skill before the arrival of domestic livestock, at which point dinner became an easier meal.

Riskin believes that the top speed of these nimble creatures could be even more impressive than demonstrated. "If they weren't in the tight confines of a cage, the bats would run faster as they would be able to jump higher," he says.

Coupled with being agile and deft, Riskin's bats were also quick learners. After one short walk on the treadmill the bats mastered both the dynamics of the machine and recognized the purr of the motor. "Vampire bats are ridiculously smart," Riskin says. "As smart as a dog."

"Vampire Bats Have a Clear Run" by Narelle Towie, Nature, 16 March 2005

Now, what's also interesting is that while vampire bats are a plague if you ranch cattle, they may be a lifesaver to ordinary people. Like the anticoagulants secreted by leeches, medicine is starting to harness the clot busters produced by the vampire bat to keep the host's blood from clotting at the wound site:

A potent clot-busting substance originally extracted from the saliva of vampire bats may be used up to three times longer than the current stroke treatment window – without increasing the risk for additional brain damage, according to research reported in today’s rapid access issue of Stroke: Journal of the American Heart Association.

The vampire bat saliva-derived clot buster is called Desmodus rotundus salivary plasminogen activator (DSPA) or desmoteplase. DSPA targets and destroys fibrin, the structural scaffold of blood clots, says senior author Robert Medcalf, Ph.D. NH & MRC senior research fellow at Monash University Department of Medicine at Box Hill Hospital in Victoria, Australia.

“When the vampire bat bites its victim, it secretes this powerful clot-dissolving (fibrinolytic) substance so that the victim’s blood will keep flowing, allowing the bat to feed,” Medcalf explains.

In the mid-1980s, Wolf-Dieter Schleuning, M.D., Ph.D., now chief scientific officer of the German biotechnological company PAION GmbH, found that the vampire bat enzyme was genetically related to the clot buster tissue plasminogen activator (t-PA) but was more potent. Medcalf and Schleuning were pioneers in the cloning and the study of gene expression of t-PA and were among the first scientists to spot its potential use for heart attack."

"Vampire bat bite packs potent clot-busting potential for strokes", American Heart Association, 10 January 2005

I'm particularly impressed by their intelligence: "Vampire bats are ridiculously smart, as smart as a dog." That's a whole lot smarter than your average red-state American, and they suck a whole lot less blood out of us blue-staters.

Sources and Further Reading

  1. "Vampire Bats Have a Clear Run" by Narelle Towie, Nature, 16 March 2005
  2. "Unlike other bats, vampire bats keep out of trouble by running, Cornell researchers find" Cornell University News Service, 17 March 2005
  3. "Biomechanics: Independent Evolution of Running in Vampire Bats", by Daniel K. Riskin and John W. Hermanson, Nature, 434, 292, 17 March 2005
  4. "Vampire bat bite packs potent clot-busting potential for strokes", American Heart Association, 10 January 2005
  5. "Vampire Bat Salivary Plasminogen Activator (Desmoteplase) Inhibits Tissue-Type Plasminogen Activator-Induced Potentiation of Excitotoxic Injury", Reddrop et al., Stroke, 2005;36:1241

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