APR 24, 2015 06:13 AM PDT

For Baboons, It May Not Be All About the Bass

The female baboon, much like a Kardashian, has always been known for having a very prominent bottom. Scientists have tended to connect the size of a female baboon's hindquarters to the attraction of male baboons, but there could more to the story. A new study out of Southern Kenya might show otherwise however.
Noodle, a female baboon in Kenya shows off her swollen red bottom
A team of researchers from Duke University and Princeton was able to take measurements of female baboons in the wild and their results were unexpected. The study appears online in the journal Animal Behaviour.

Baboons breed throughout the year, and part of the biological signal that a female is ready to mate is the size and deep color of her behind. This is in an indicator of ovulation, which goes on for approximately 10 to 20 days per month. The tissue shrinks back to normal when the hormones have stopped surging.

To precisely measure this variation in female baboons, researchers had to get creative. Understandably, female baboons would not appreciate scientists getting up close and personal on their lady parts. Duke University researcher Courtney Fitzpatrick adapted a camera technique that was originally developed to measure large animals like elephants and bison from a distance.

Fitzpatrick outfitted a telephoto zoom lens with a digital caliper, which allowed her to know how far away a baboon was from the camera. Then by counting pixels in the resulting digital images of baboon bottoms and converting them to millimeters, Fitzpatrick was able to estimate the size of each swelling.

As with humans, size did vary. Measurements from 34 females revealed that some females swell more than others. The biggest bottom belonged to a female named Vow, whose rump swelled by 6.5 inches as she approached ovulation. The smallest belonged to a female named Lollipop, whose bottom only increased by four inches.

"Some females are just bigger than others," Fitzpatrick said.

The team combined these measurements with large amounts of long-term data on the offspring of each female. When factors such as the female's age and rank were accounted for they were surprised to find that females with bigger backsides don't necessarily make better mothers. The baboons with larger behinds did not produce more surviving infants than their smaller counterparts.

The researchers also documented male courtship behavior during the time when females were swollen. This is where their findings deviated from what was expected. They found that big-bottomed females were no more likely to attract mates than their smaller-bottomed counterparts.

Instead of going for larger and more prominently swollen backsides, most males preferred females that had cycled more times since their last pregnancy.

Female baboons are similar to human females in that after having a baby, ovulation does not return right away. Usually after a baboon infant has weaned, a female baboon will be ready to mate again. Pregnancy is less likely to occur while a baboon mother is still feeding her infant, another similarity to human mothers.

The study results suggest that male baboons are attracted to those females who are more biologically ready for a baby than just those who are swollen to larger sizes. Rather than rump dimensions, it seems that males go for females who have had more post partum cycles.
"It's almost as if the males are counting," Fitzpatrick said. "Our study suggests that, at least in part, males follow a rule along the lines of 'later is better' rather than 'bigger is better.'"

Since baboon mating is largely driven by the need to produce offspring more likely to survive, the study may have uncovered additional factors that male baboons notice when mating and that these considerations go beyond the very visual signal of a large red bottom. The team hopes to do further research to determine if females actually mate with more males after they've had more postpartum menstrual cycles, and whether that translates to higher survival for their offspring.
About the Author
  • I'm a writer living in the Boston area. My interests include cancer research, cardiology and neuroscience. I want to be part of using the Internet and social media to educate professionals and patients in a collaborative environment.
You May Also Like
AUG 21, 2018
Plants & Animals
AUG 21, 2018
Animals Have Changed a Lot Since Humans Began Breeding Them
People first started breeding animals about 10,000 years ago, and it’s safe to say that many bred animals have changed a lot since then. After people...
AUG 28, 2018
Earth & The Environment
AUG 28, 2018
African savannas are emitting three times the CO2 than thought
The Miombo woodlands extend over 2.5 million square kilometers across Africa, passing through Angola, Zambia, Tanzania and Mozambique. This ecosystem provi...
AUG 28, 2018
Plants & Animals
AUG 28, 2018
Migrating Monarch Butterflies Are Experiencing Elevated Parasitism Risks
Monarch butterflies don’t take too kindly to the colder Winter months. The insects naturally avoid the cold by migrating to places that stay warm yea...
SEP 24, 2018
Plants & Animals
SEP 24, 2018
All-Female Termite Colonies Observed for the First Time
In the case of most animal species, it takes both a male and a female for reproduction to take place. But a few exceptions to this rule do indeed exist, pa...
OCT 25, 2018
Cannabis Sciences
OCT 25, 2018
So Why Does Weed Even Have THC?
If you have been following the science on marijuana, you are probably acquainted with the chemical delta-9-tetrahydrocannabinol      ...
OCT 30, 2018
Plants & Animals
OCT 30, 2018
Scientists Discover New Swallowtail Butterfly Species on Vanua Levu
While perusing the Pacific Island of Vanua Levu in Fiji last year, researchers happened upon a precellular butterfly that captivated their attention. Given...
Loading Comments...