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captcat
1st Mar 2006, 08:31
Size does matter in bats' evolution
By William Kates, Associated Press Writer | January 24, 2006

SYRACUSE, N.Y. --For some male bats, sexual prowess comes with a price -- smaller brains. A research team led by Syracuse University biologist Scott Pitnick found that in bat species where the females are promiscuous, the males boasting the largest testicles also had the smallest brains. Conversely, where the females were faithful, the males had smaller testes and larger brains.

"It turns out size does matter," said Pitnick, whose findings were published in December in "Proceedings of the Royal Society: Biological Science," an online journal.

The study offers evidence that males -- at least in some species -- make an evolutionary trade-off between intelligence and sexual prowess, said David Hoskens, a biologist at the Centre for Ecology and Conservation at the University of Exeter in England and a leading authority on bats' mating behavior.

"Bats invest an enormous amount in testis, and the investment has to come from somewhere. There are no free lunches," said Hoskens, who did not participate in the study.

The relationship between the breeding system and relative brain size has received little investigation, said Pitnick, who teaches evolution and population biology and researches topics such as sexual selection and sexual conflict.

Bats are the second largest group of mammals (behind rodents) with about 1,000 known species. Because of their exceptional navigational and flying abilities, bats have been the subject of countless studies, providing Pitnick and his colleagues -- Kate Jones of Columbia University and Gerald Wilkinson of the University of Maryland -- with a bounty of data without having to slink off into caves.

Pitnick's team looked at 334 species of bats and found a convincing contrast in testes size. In species with monogamous females, males had testes starting at 0.11 percent of their body weight and ranging up to 1.4 percent. But in species where the females had a large number of mates, Pitnick found testes ranged from 0.6 percent to 8.5 percent of the males' mass (in the Rafinesque's big-eared bat).

"If female bats mate with more than one male, a sperm competition begins," Pitnick said. "The male who ejaculates the greatest number of sperm wins the game, and hence many bats have evolved outrageously big testes."

Promiscuity is known to make a difference in testicle size in some other mammals. For example, chimpanzees are promiscuous and have testicles that are many times larger than those of gorillas, in which a single dominant male has exclusive access to a harem of females.

Large brains, meanwhile, are metabolically costly to develop and maintain. Pitnick's research suggested that in those bat species with promiscuous females, the male's body used more of its energy to enhance the testes -- giving it the greater adaptive advantage -- and lacked the energy it needed to further develop the brain.

The study found that in more monogamous species, the average male brain size was about 2.6 percent of body weight, while in promiscuous species, the average size dipped to 1.9 percent.

27mm
1st Mar 2006, 08:37
I'm deeply disappointed - this can only mean that Buster Gonad (he with the unfeasibly large testicles) - is not the intellectual giant I imagined him to be....

Virgilio
1st Mar 2006, 08:53
...and cuckholded, with that :suspect:

allan907
1st Mar 2006, 10:07
I don't get that post - whatz a testis?:confused:

RiskyRossco
1st Mar 2006, 12:40
Somebody from Yorkshire asking for directions . . .?

Not a deliberate dig. . honest. . . only the phonetics apropos recent comments. . well. . it sorta sounded similar. .
:ouch: :O :ooh:
buckles on kevlar and tinfoil hat, tightens parachute harness, leaps for the door. . .

frostbite
1st Mar 2006, 13:03
Pitnick seems a strangely appropriate name for this sort of study.

bear11
1st Mar 2006, 13:34
"The relationship between the breeding system and relative brain size has received little investigation, said Pitnick".

Hmm, I wonder why? I've always wondered about the motivation and sanity of the type of people who spend years studying 334 species of bat's balls. You can imagine the dinner conversation if he asked you out on a date.

I had a mate in school who did a PhD in music after - his thesis was on some kind of medieval music who apparently only 4 other people in the world understood. Still, I suspect even he'd think twice about going into bat's balls in excruciating detail.

Anyone else have mates who did something equally obscure?