Early spring means more bat girls

May 5, 2012

There must be something in the warm breeze. A study on bats by a University of Calgary researcher suggests that bats produce twice as many female babies as male ones in years when spring comes early.

The earlier in the spring the births occur, the more likely the females are to survive and then reproduce a year later, as one-year olds, compared to later-born pups, according to Dr. Robert Barclay's research published in PLoS ONE.

"The early-born females are able to reproduce as one year olds, whereas male pups can't," explains Barclay, professor in the Department of Biological Sciences at the University of Calgary.

"Thus, natural selection has favoured internal mechanisms that result in a skewed sex ratio because mothers that produce a daughter leave more in the next generation than mothers who produce a son."

The length of the growing season has an impact on the ratio of female to male offspring and the time available for female pups to reach , the study found. This suggests that not only does sex-ratio vary seasonally and among years, but it also likely varies geographically due to differences in season length.

Barclay analyzed long-term data on the variation in offspring sex-ratio of the big , Eptesicus fuscus, a common North-American species that consumes insects.

"In this species, more eggs are fertilized than eventually result in babies, so there is some mechanism by which a female embryo is preferentially kept and male are resorbed early in pregnancy," says Barclay. But, he adds, the biochemistry behind the skewed sex ratio is unknown.

"Some other mammals and some birds have the ability to adjust the of their offspring," says Barclay. "Even human-baby ratios vary—there is a study showing that billionaires produce more sons than daughters, for example."

This is the first long-term study on sex ratios in bats, says Barclay and it "suggests some pretty interesting physiology."

Explore further: Female birds boost up their eggs when hearing sexy song

Related Stories

Female birds boost up their eggs when hearing sexy song

June 8, 2006

In a new study published in the latest issue of Ethology researchers show that female songbirds can alter the size of eggs and possibly the sex of their chicks according to how they perceive their mate’s quality.

Female Birds Boost Up Their Eggs When Hearing Sexy Song

July 17, 2006

In a new study published in the latest issue of Ethology researchers show that female songbirds can alter the size of eggs and possibly the sex of their chicks according to how they perceive their mate's quality. The researchers ...

Researcher finds Laysan albatross employs 'dual mommies'

May 28, 2008

What's a girl to do if there's a shortage of males and she needs help raising a family? The Laysan albatross employs a strategy called reciprocity, where unrelated females pair together and take turns raising offspring.

Manipulative mothers subdue show-off sons

September 12, 2011

The gaudy plumage and acrobatic displays of birds of paradise are a striking example of sexual selection, Charles Darwin's second great theory of evolution. But new research shows that this powerful process may collapse when ...

Recommended for you

Cuing environmental responses in fungi

May 26, 2016

Fungi can sense environmental signals and react accordingly, changing their development, direction of growth, and metabolism. Sensory perception lies at the heart of adaptation to changing conditions, and helps fungi to improve ...

Bacterial diversity in soils was shaped by ice ages

May 26, 2016

From a pharmaceutical perspective, few microbes have been as valuable as Streptyomyces: This genus of bacteria is the source of 80 percent of antibiotics in use today. A new study of its distribution in North American soils ...

Is aging inevitable? Not necessarily for sea urchins

May 25, 2016

Sea urchins are remarkable organisms. They can quickly regrow damaged spines and feet. Some species also live to extraordinary old ages and—even more remarkably—do so with no signs of poor health, such as a decline in ...

Why fruit fly sperm are giant

May 25, 2016

In the animal kingdom, sperm usually are considerably smaller than eggs, which means that males can produce far more of them. Large numbers of tiny sperm can increase the probability of successful fertilization, especially ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.