updated 8/31/2010 7:41:46 PM ET 2010-08-31T23:41:46

To most human males, the thought of your mother anywhere near your sex life is probably horrifying. Not so for the bonobo, one of our closest primate relatives. A new study confirms that hanging out with mom boosts male bonobos' chances of getting intimate with a fertile female.

The study found that when their mothers are around, low- to mid-ranking bonobo males get more opportunities to mate. Mothers facilitated sons' presence in their social circle so they were able to interact with more females, and also chased away rival males who might try to break up their sons' blooming relationships.

The mothers aren't just busybodies, say the researchers. In fact, taking an active interest in their sons' love lives helps mothers pass on their own genes.

"If they support their sons, they can have more grandkids," study researcher Martin Surbeck, a biologist at the Max Planck Institute for Evolutionary Anthropology in Germany, told LiveScience.

Bonobo mama's boys
As any newlywed can tell you, parental interest in offspring's reproduction is common. Orcas are known to form strong mother-son bonds, and according to a study published in August in the journal Nature Communications, being born to a high-ranking mom gives male hyenas a reproductive boost later in life.

In primates, mothers have been shown to improve the survival of their daughters' offspring. But mother-son bonds are harder to measure, because most primate males leave their mother's side at puberty. Bonobos, a cousin to chimpanzees, are an exception. Bonobo communities are female-dominated, and males stick with their mothers in adulthood.

Researchers have long known that the status of bonobo males is linked to the status of their mothers, and field observations suggested that moms were taking an active role in facilitating their sons' mating, said Surbeck. To figure out the maternal role, he and his colleagues used DNA information to tease out the relationships between the bonobos in their field area at Salonga National Park in the Congo. Then they observed the bonobos over a 10-month period, watching how often they fought, mated and became fertile.

Maternal matchmakers
They saw that while the primates split into different "parties" during the day, sons stuck with their mothers between 81 percent and 92 percent of the time. When moms weren't around, the dominant male was responsible for about 41 percent of sexual encounters with fertile females. But when the mothers of low-to mid-ranking males were present, that proportion dropped to 25 percent. In other words, moms kept the dominant male from monopolizing the most fertile females, allowing their own sons to mate, too.

Sometimes, the moms interfered, chasing unrelated males away from females or backing up fights involving their sons. Other times, they stood guard while their sons mated, keeping competitors at bay.

But in large part, the mom's role may be more like that of a matchmaker. Since females have lots of social status in bonobo communities, Surbeck said, a mother's presence allows a son to play a more central role in the group. Being in the center of the social group means more interactions with females and more opportunities to mate.

Evolutionary cousins
The study, published this week in the journal Proceedings of the Royal Society B, "confirms largely what we've known for a long time" about the importance of mothers in bonobo communities, said Jo Thompson, the director of the Lukuru Wildlife Research Project in the Democratic Republic of the Congo.

Thompson, who researches bonobos but was not involved in the current study, said the research raises new questions about the influence of a mother's social rank on her son's success, as well about how other family members, like brothers, might influence mating. She also warned that while the current study showed low- and mid-ranking males got to mate more with fertile females when their moms were present, it didn't investigate whether they actually had more offspring.

"This is a good solid study that continues to build on the knowledge we have, and leads to more questions," Thompson said. "The next step is where we really get interesting."

Studying bonobos is important for conservation reasons, as the animals are threatened by habitat loss and poaching, said University of California Los Angeles anthropologist Joan Silk, a primate researcher who was not involved in the study. But because humans share an evolutionary ancestor with bonobos, the studies may also give us hints about our own evolutionary background, Silk said.

"Seeing both chimpanzees and bonobos gives us an idea of the range of possibilities of our ancestors'" behavior and social structure, Silk said. "They help us imagine what early human ancestors might have been like."

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Explainer: 10 peeks at sex in the wild

  • Image: scroll fragment
    Jerome Maison  /  AP file / Warner Independent Pictures

    Emperor penguins endure some the harshest conditions on the planet — the Antarctic winter — to satisfy their primal urge for sex. The annual ritual begins with a days-long, up to 75-mile slog to their inshore breeding grounds. Once there, an elaborate courtship of calls and poses reunites old mates and enables young lovers to form lasting bonds.

    Copulation itself occurs under the cover of the dark of the polar night. Then the true sign of their devotion begins: Males huddle together to incubate the eggs as the females waddle back out to sea to feast, fattening up to provide for their newly hatched young. Once she returns, males depart in the first of a tradeoff that may, eventually, allow for healthy offspring.

    Click on the "Next" label for nine more peeps at sex in the wild.

    - John Roach, contributor

  • Captive pandas require help to get it on

    Image: Pandas
    Wichai Taprieu  /  AP file

    In the wild, biologists say pandas get it on without too much of a hitch. But since the wild population in China's mountain forests hovers around just 1,600, there's a push to boost the panda population in zoos around the world. And that's where the problems lie. Many pandas lack interest in their arranged mates and some inexperienced males who give it the old college try fail to engage the proper body part. As an aid, some zoo keepers attempt to arouse the bears and teach them appropriate technique with specially made DVDs, a.k.a. panda porn. When that fails — and it often does — artificial insemination is considered a last resort. These tricks combined with a better understanding of what makes the panda libido tick are beginning to pay off. The captive population has boomed in recent years.

  • Male macaques groom for sex

    Image: Japanese Macaque monkeys
    Shuji Kajiyama  /  AP

    Male macaques groom females in exchange for sex, according to a study that examined the market underpinnings of monkey sex. According to the research, based on 20-months of observation in an Indonesian nature reserve, a female is three times more likely to mate with a male if he grooms her first. Supply and demand also comes into play: Males spend more time grooming when competition for female attention is greater. Scientists refer to this practice as a biological market.

  • Male antelopes play hard to get

    Image: Antelopes
    Jakob Bro-Jorgensen / Zoological Society of London

    For highly-desired male topi antelopes in Africa, the frenzied six-week-long mating season is exhausting. Any given female is receptive for about a day, thus she wants to mate as many times as possible, especially with the fittest males. This creates intense competition for high quality antelope sperm, allowing those that possess it to be picky. A study of the phenomenon found the choosy males deliberately select the least mated females and fend off aggressive females they've already mated with. The aggressive female in the center of this image is attacking the male on the left as another female eyes the scene.

  • Sumatran rhinos tussle before they tango

    Image: Newborn rhino
    Tom Uhlman  /  AP

    Mating for the typically solitary and territorial Sumatran rhinoceros is a drawn-out affair. Studies of the critically endangered species in captivity show that when a female becomes receptive to a male's approach, she'll exhibit increased urine spraying, tail raising and swinging, and vocalizations. Foreplay includes head and genital butting, which can be a bit too much when a female isn't quite ready to tango with a young and aggressive male. But when the tussle is successful, a male will mount, often riding his mate for up to an hour. The image here shows the results of a successful mating at the Cincinnati Zoo. Such captive breeding efforts are a silver lining for conservationists hoping to keep the Sumatran rhino alive — just 300 are thought to remain in the wild.

  • Burliest walrus bulls get the harem

    Image: Walrus
    Liz Labunski  /  AP

    With a cacophony of clicks, clacks, whistles, and bellows, male walruses swim around the chilly Arctic waters vying for the attention of ice-bound females. Males will also fight off other males that get too close, sending the loser packing. Once the fussing and fighting is done, female harems surround the burliest males in the water for an underwater romp. Though scientists know little about what actually happens under the cover of the waves, they do know walruses are endowed with the mammal world's largest penis bone, called a baculum, which extends up to 30 inches.

  • Dolphin mating is brief, but bountiful

    Image: drainage channel
    Noaa  /  NOAA

    For playful dolphins, mating seems just like another carefree and pleasurable way to pass away the day. Along with some typical male posturing for access to females, there's plenty of chasing, rubbing, nuzzling and stroking that constitutes as foreplay. The belly-to-belly copulation act itself lasts less than a minute, though is often repeated several times over the course of an hour.

  • Virgin female spiders risk all for a big mate

    Image: archaeological site in Masada

    For some male spiders, sex is the ultimate sacrifice: females eat them as part of the reproductive ritual. But among the East African blood-gorging jumping spider Evarcah culicivora, shown here, males possess the coital-infused cannibalistic urge. Nevertheless, female virgins opt to be deflowered by bigger males before settling in with a small guy for the long haul. Scientists suspect females gamble with their fate once in hopes of producing larger, fitter offspring, but decide not to double down after the flirtation with danger.

  • Sappy sex for beetles of all sizes

    Kensuke Okada

    As this picture shows, Japanese sap beetles come in big, medium, and small sizes. Generally, in the beetle world, mating success is only bestowed on males with the biggest bodies because they can beat out the competition with brute force. Big sap beetles successfully employ this strategy, but when they do, the medium guys take to the air with their extra long wings and survey for sites where big males are absent. But the little guys have the biggest testicles. This allows them to hang with the big guys and sneak sex behind their backs. Since the little beetles have such big testes, they produce more competitive sperm, upping their chances at siring offspring when they get a shot.

  • Cycads have 'hot' plant sex

    Irene Terry  /  Univ. of Utah

    Hot sex has ancient roots. The males in a group of plants called cycads, which have been around for at least 250 million years, get all hot and bothered as a means to compel pollen-covered insects deep in their cones to flee forth and find a female to pollinate, according to scientists. The plants begin the process by emitting a fragrance that lures little insects called thrips into their cones. After a few hours of the thrips feasting and rolling around in there, the cycads heat up as much as 25 degrees Fahrenheit, which turns their sweet smelling fragrance into a stench. The thrips flee, some landing on benign-smelling female cycads and thus completing the pollination cycle.


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