Is males' attraction to trucks and balls genetically based?

 Young chimps. Photo: Delphine Bruyere 

My husband and I raised one girl and one boy, close together in age. We tried hard to avoid gender-stereotyping our young kids in any way. They had the same toys, many of them gender neutral, for some time.

Our son clung to the baseball fence, drooling
As it happened, our yard backed up to a school athletic field. From late winter on, we daily heard the THWOCK of  bats hitting balls during baseball practice. Our son was barely able to walk when he began toddling out to the playing field alone, to watch the students play baseball.  He'd hang on the baseball fence with his tiny fingers for hours, mesmerized and drooling. Soon he was into trucks - at the age of 2, he memorized the name of 33 different kinds of trucks from the truck library books he clamored for.  Our daughter's interests were varied, but she showed no inkling of his fascination with balls and trucks. We couldn't understand it. He wasn't in preschool, and my husband and I cared nothing for vehicles of any kind (although Ken is a baseball fan).

We share 98% of our DNA with chimps
So last week I was intrigued to see a paper in the online journal Current Biology about gender-stereotyped roles in young chimps. Since chimps are our closest relatives, sharing 98% of our DNA, any observations about chimp behavior could have implications for the origins of our own behavior.
 

Young female chimps "play mothering" more than young males

Author Sonya Kahlenberg, a biological anthropologist at Bates College in Maine, observed chimps in Kibale National Park in Uganda over 14 years. She and co-author Richard Wrangham, a biological anthropologist at Harvard, noted that 67% of young females carried sticks while only 31% of young males did. Sticks are used sometimes as weapons or as tools, to probe holes for food or water. But the young chimps also cradled long thick sticks as if a stick were a baby, carrying it around for no particular reason. They sometimes carried the stick as long as 4 hours, and took it with them to their nests for sleep. The authors felt that the stick-carrying was "play-mothering." The males who did it stopped as they got older. The females stopped when they gave birth to real babies, whereas use of sticks for other purposes continued after motherhood.

In her recent article, Kahlenberg cited previous research in which captive young male monkeys preferred wheeled toys, while female monkeys, like human girls, showed greater variability in preferences. The male monkeys also showed more rough-and-tumble play than females. The authors of this study (published in PubMed) hypothesized that these differences are hormonally influenced.

Some have speculated that boys, including some male primates, prefer toys like balls and trucks because these toys are associated with more freedom of movement than, for example, playing with dolls.

Evolutionary advantage for human males to prefer movement?
Could it be true that very young male humans are drawn to balls and trucks because playing with them involves more movement?  It's not clear at all to me that male attraction to movement would be more advantageous evolutionarily than female attraction to movement. Even while carrying infants, our female prehistoric ancestors still were compelled to move around gathering plants for food, I would think. And keeping up with mobile children certainly involves movement. But if males were the defenders of early human tribes, and if they went on long hunts for food, then perhaps males could have evolved a hormone-based propensity to be more active.

I don't know, it's an interesting question. Culture has so much to do with it. A few decades ago, girls rarely if ever participated in team sports at school (at least in the U.S.). Today they do, when given the opportunity.

One more reason to protect wild apes
I'd love to see more field observations of gender-based behavioral differences in young primates. That's one more reason we need to protect chimpanzees and other primates from the illegal poaching that threatens all populations of wild apes.

For more information about what you can do to protect wild apes, see these links to primate conservation NGOs:
Jane Goodall Institute
Orangutan Outreach
Sumatran Orangutan Society
Dian Fossey Gorilla Fund International
Orangutan Land Trust
International Primate Protection League
TRAFFIC:the wildlife trade monitoring network

Some of my previous posts about primates and primate conservation:
Hunting may threaten orangutans even more than habitat loss Dec 6, 2010

Wildlife trade rivals drug trade in profits September 20, 2010
Laws flaunted: flourishing pet trade threatens orangutans' survival August 23, 2010
My search for a wild orangutan in Borneo and Sumatra August 16, 2010
Orangutans dwindle as Borneo, Sumatra converted to palm-oil plantations August 3, 2010

The great apes are losing ground. March, 2010
The U.S. imports 20,000 primates per year. February, 2010
Baboons are Africa's most widespread primate. Females rule! December 30, 2009
Mama monkeys give in to tantrums....when others are watching. April 23, 2009
Angry chimp reveals a "uniquely human" ability. March 21, 2009

Monkeys and parrots pouring from the jungle. September, 2008
Chimps' short-term memory is better than humans'  April 2, 2008
Chimps share human trait of altruism August 3, 2007

Keywords: chimpanzees chimp behavior animal behavior gender stereotypes chimps and dolls chimps and sticks Sonya Kahlenberg Kibale National Park Richard Wrangham

Animals making tools...what else are they capable of?

A pair of rooks. Photo by Christopher Bird, news.bbc.co.uk

Animals are at it again. Acting human. Or rather, exhibiting behaviors that we once thought were exclusively human. We once believed, I might say, that these behaviors defined humans as better, different, smarter than all other living things.

I'm talking about tool use. As it turns out, tool use has now been observed in dozens of nonhuman species, including otters, monkeys, chimps, and 39 species of birds!

The most recent study involves rooks, a crow-like European species common in folklore. They're in the same family as our American crows, ravens, jays, and magpies.

The rooks in this study, reported just today (May 28) in the Proceedings of the National Academy of Sciences, were given access to food that could only be obtained by pushing a small rock off of a ledge into a tube. They quickly mastered that task. Christopher Bird of the University of Cambridge and Nathan Emery of Queen Mary College, London, challenged the birds further by moving the small rock farther away. Before long, a female rook, Fry, figured out picking up the stone and carrying it to the ledge. Her mate, Cook, followed her actions, then a second pair did.

The birds mastered various other tasks involving tools such as sticks and wires. They even figured out how to bend a wire to fashion a hook necessary to retrieve items. Although wild New Caledonian crows have been observed fashioning hooks in the past, the authors assert that this is the "first unambiguous evidence of animal insight, because the rooks made a hook tool on their first trial we know that they had no previous experience of making hook tools from wire because the birds were all hand-raised." The New Caledonian crows were known to use tools in the wild.

I love research that shows how smart animals are, and how we're not the supreme beings we think we are. What else are animals capable of that we don't know about yet? They deserve more respect, more of the world's remaining resources, than they're getting from their human relatives.

My previous post about New Caladonian crows making tools.

All my previous posts about tool use (or making tools) in animals.

Sources:
Christopher D. Bird and Nathan J. Emery. Insightful problem solving and creative tool modification by captive nontool-using rooks. May 28, 2009. Proceedings of the National Academy of Sciences.

Randolph E. Schmidt, Associated Press. Rooks figure out how to use tools. May 28, 2009. Charlotte Observer

Key words:: birds tool use rooks animal behavior making tools bird behavior animal intelligence

Mama monkeys give in to tantrums...when others are watching

Photo by Stuart Semple
Female rhesus macaques and their babies cluster amiably, but an infant tantrum can disrupt the scene

Have you ever been in a public place when your toddler throws a tantrum? I have and it's pretty embarrassing. Not because of the crying, per se, but because onlookers may glare. In fact, I admit to occasionally looking with disapproval myself at other parents who ignore their babies' loud distress. It's distressing to me to listen to it.

Does the presence of disapproving onlookers have any effect on how human moms react to tantrums? You bet.

Turns out the same dynamic goes on in troops of monkeys.

Behavioral scientist Stuart Semple & his colleagues studied monkey tantrums and bystander reactions by watching rhesus macaques that roam freely on the island of Cayo Santiago, Puerto Rico. Baby monkeys wanting to be nursed when mom wasn’t willing often started shrieking. For more than 300 outbursts of baby crying, the scientists noted which other monkeys, if any, were within two meters. The team also noted how mom, baby and the bystanders interacted.

The researchers found that the monkey mothers are twice as likely to let a howling infant have its way during very public tantrums than during more private moments, says Stuart Semple of Roehampton University in London.

Not a bad decision on mom’s part. A baby rhesus monkey makes a high-pitched, grating shriek that Semple calls “pretty harsh stuff.” Onlookers get restless and irritable; in fact, a mom and unhappy baby are 30 times more likely to suffer aggression from a bystander during a crying bout than they would in quiet times. Onlookers within two meters made threatening gestures, or even chased, grabbed or bit the mother or the infant.

Most of the aggression came from monkeys that weren't close relatives and outranked mom in the social hierarchy. Her relatives proved more tolerant.

When moms and babies weren’t close to other monkeys, rebuffed babies that started shrieking were allowed to nurse 39 percent of the time, the researchers found. With just relatives nearby, the babies’ luck rose to 53 percent. But with unrelated onlookers that outranked mom in the dominance hierarchy, babies won the tantrum 81 percent of the time.

Photo by Stuart Semple
If baby cries when they're alone, the tantrum has only a 39% chance of changing mom's mind.

Mom herself gets agitated by the baby’s crying. Analyzing records of mothers' behavior, the researchers calculated that a female on average was 400 times more likely to get aggressive toward her baby when it was crying than when it wasn't. Wow! That surprised me! Must be lots of adult monkeys out there with unresolved "issues" with mom! I tend to think of non-human mammals as always being kind and attentive to their young. But I guess not...

Studies of communication often focus on just two parties, the one sending the message and the intended receiver, Semple says. But the real world is full of other eyes and ears, ones that senders and receivers often react to. “We need to start thinking about communication in more realistic terms,” he says.

Research has found that nonhuman primates pay attention to eavesdropping bystanders, “but this is the first demonstration that communication between mother and infant is affected by an audience,” says behavioral biologist Dario Maestripieri of the University of Chicago.

Other baby primates besides humans and macaques throw tantrums, says behavioral biologist Liesbeth Sterck of Utrecht University in the Netherlands. The Thomas langurs she watches certainly do. However, she points out that langurs do more "allomothering," caring for infants other than their own, than rhesus macaques do. That behavior may affect the dynamics in this and other species, she says.

Semple and his colleagues report online March 10 in Proceedings of the Royal Society B. time.

Source: Susan Milius. Public tantrums defeat monkey moms too. Science News. April 11, 2009. Vol. 175 #8

Keywords:: monkey behavior rhesus macaques Stuart Semple Sally Kneidel maternal behavior monkey aggression primate behavior primate aggression primate mothering

Links to some of my previous posts on this blog about monkeys and chimps:
(to find others, enter "primates" in the search bar above)

Angry chimp reveals "uniquely human" trait

Monkeys and parrots pouring in from the jungle

Almonds or pizza? Capuchins are smarter than we thought

Exciting new discovery: chimps' short-term memory is better than humans'

Chimps share the human trait of altruism

Monkeys can estimate numbers as well as Duke students

U.S. labs import thousands of wild-caught primates

Chimps and gibbons have human elements to their speech

Research shows older females preferred as mates

Top 6 ways to protect wildlife from commercial trade

Wildlife trade, forestry, and the value of activism

Monkeylala (by Ken Kneidel)

Wild monkeys use tools - and choose the right one for the job

The first monkeys I ever saw in the wild were white-faced capuchins in Costa Rica. Or maybe black howlers were first. But the capuchins were much more charming than the howlers. I fell in love with them. We were on the beach at Manuel Antonio Parque Nacional the first time, and my son Alan had a banana in his pocket. The capuchins were interested in us because of the banana, and they had no fear. The howlers and spider monkeys and squirrel monkeys will stay up in the trees, far away from you, no matter what you have or do. But the capuchins come right down. They even ran out on the beach and snatched things from people's picnic baskets. The capuchins, with their human-like faces and hands, sat in the trees eating bags of crackers and throwing the cellophane wrappers down.

A white-faced capuchin at Manuel Antonio Parque Nacional in Costa Rica, smelling the banana in Alan's pocket
Photo by Sally Kneidel

As a biologist, I know that's not a good thing at all. But yet, I could see myself in the capuchins. I also do what I'm not supposed to do, eat things I know aren't good for me, make choices that endanger my well-being. We were tempted to give the capuchins the banana, but we didn't. We didn't give them anything to eat, we knew better than that. Monkeys that eat human food get sick eventually from malnutrition.

But the next day, we asked the ranger what time the troop of capuchins usually moved through the trees over the beach, on their daily foraging rounds. Our Spanish communication wasn't precise, but he told us and we got the idea. We waited for the monkeys. They came. And they were mad that Alan and I were standing under the trees while they were cavorting from branch to branch, just overhead. The head honcho, a male capuchin, came down and bared his teeth at us and shook the branches to frighten us. We trembled with delight instead.... the pleasure of recalling it even now makes my heart beat fast. We took his photo while he railed at us, infuriated. I was sorry to distress him, but I couldn't help it. Monkeys are territorial, they get angry just like anyone whose space is invaded. It wouldn't hurt him to bare his teeth and shake a few branches. His social stature with his troop may have benefitted from the display.

The capuchin was angry that we were standing under the trees in his foraging route. He bared his teeth aggressively.
Photo by Sally Kneidel

Anyway, I started this post to write about a news story that just came out about capuchins. Capuchins used to be "organ grinder" monkeys. These days they're sometimes trained as "helping hand" monkeys for people with paraplegia or quadriplegia. They're very smart monkeys. This recent piece of research shows that capuchins in Brazil are adept at tool use - an ability that used to be attributed only to humans but has now been demonstrated by numerous species from birds to apes. The capuchins use stones to crack open hard-shelled nuts. But the research goes far beyond just demonstrating tool use. The capuchins don't just grab the nearest rock at hand. They select the best tool for the job. Primatologist Elisabetta Visalberghi of the Institute of Cognitive Sciences and Technologies in Rome has shown that these monkeys draw on knowledge of a variety of nuts and stones to select the most effective implement. She studied the monkeys in the wild and observed that they generally approached two or three stones that differed in hardness, size, or weight. In nearly every case, the monkeys chose the most appropriate stone.

"The present findings make capuchins a compelling model to track the evolutionary roots of stone-tool use," says Visalberghi. Because capuchins shared a common ancestor with humans 35 million years ago, Visalberghi feels that their behavior may demonstrate that the capacity for tool use evoloved earlier than thought.

But primatologist Frans de Waal of Emory University has a different interpretation. He says the work highlights the monkeys' capacity for trial-and-error learning, that planning may not have been a part of their tool preferences. The monkeys may be simply applying life lessons about the success of various stones at cracking nuts.

Capuchins in Brazil selecting stones for cracking nuts, from Wired Science

Whether their discriminatory skills are the result of planning or of learning, they're still a step beyond simple tool use. They demonstrate in a non-human animal the ability to select and apply an appropriate tool for a particular job. We humans are not so unique after all. Do we really deserve to claim the whole planet all for ourselves and crowd out every other species of animal, leaving only the pest species, the livestock, and the companion species? I hope not. I hope the capuchins will always be alive and well in Costa Rica and Brazil, not displaced by cattle pastures.

Source:
Bruce Bower. Monkeys pick the right rock. Science News. February 14, 2009.

Keywords:: capuchins tool use animal behavior monkeys Costa Rica

Dolphins learn tool use from their moms

Dolphin with sponge to protect sensitive snoot while foraging

Not too long ago, scientists used to believe that "tool use" was one of the characteristics that set humans apart from all other animals.

We now know that animals do use tools. The list of species observed not only using tools, but making tools, continues to grow.

Chimpanzees were the first species observed with tools - Jane Goodall saw chimps using sticks to extract edible termites from underground tunnels. More recently, chimps have been observed making and using spears on other prey.

Bird species also make tools to forage. A warbler species on the Galapagos uses thorns to probe under bark, and scrub jays make and use hooks to retrieve edible items - to name a couple of examples.

Marine biologists have also documented bottlenose dolphins using tools. Scientists say that dolphins in Australia's Shark Bay wear marine sponges on their beaks like a glove, to protect their sensitive beaks when foraging along rugged ocean bottoms. Poking around in deep water carries the risk of stings from bottom dwellers.

(Sponges are animals on the ocean floor whose skeletons are flexible and absorbent.)

The boater who first saw a sponge on a dolphin thought it was a tumor. But the tumor turned out to be a sponge.

As marine biologists have studied the tool use, they've discovered something even more interesting. Only the dolphins in the Shark Bay location use the sponges, and only a fraction of the dolphins in that bay use them. The scientists have studied the family relationships of the dolphins in the bay and have now determined that the spongers belong almost exclusively to a single maternal lineage. The sponge behavior is being transmitted from mothers to offspring.

But... the sponging doesn't follow any of the patterns that would be expected if it were genetically based.

The scientists have concluded that the spongers are learning the behavior from their mothers - the only interpretation that fits the observed family relationships of the spongers. Whether the spongers are learning from observing their mothers, or are being intentionally instructed by their mother remains to be seen.

This is not the first example of what is known as "cultural transmission" of behaviors in animals - behaviors transmitted to other individuals by way of observation or instruction. At least one population of macaque monkeys regularly wash their grains in pools of water, and that behavior is known to be culturally transmitted, for these particular monkeys.

Macaque washing food
photo courtesy of www.animalplanet.com.au

What more will we learn in future years about the traits we share with our animal relatives?

These discoveries are, for me, all the more reason to do whatever we can to stop the environmental degradation that threatens wildlife species worldwide.

See my previous post for three things you can do to slow habitat loss from global warming.

Source:
Susan Milius. "Sponge moms: dolphins learn tool use from their mothers." Science News, June 11, 2005

Keywords :: bottlenose dolphins marine biology tool use cultural inheritance cultural transmission animal intelligence animal behavior macaques