Tag Archives: Macaques

Japanese monkeys are apparently having sexual intercourse with deer

Nature is really messed up sometimes.

Adolescent female Japanese macaque on the back of a male sika deer. Courtesy of Noëlle Gunst

Researchers from the University of Lethbridge in Canada first spotted the behavior earlier this year, but it was a single anecdotal episode. It wasn’t clear why or even exactly what was happening.

“Even the sexual nature of this interaction was not clearly demonstrated,” said Noëlle Gunst.

So she and her colleagues did what you’d expect from scientists: they went back to look for more evidence. They looked at different types of sexual relationships, particularly between adolescent female monkeys and male deer.

“We observed multiple occurrences of free-ranging adolescent female Japanese macaques (Macaca fuscata) performing mounts and sexual solicitations toward sika deer (Cervus nippon) at Minoo, central Japan,” researchers write in the study.

Japanese macaques and sika deer have complex relationships. The macaques sometimes ride deer just like humans ride horses. The deer seem to tolerate it in exchange for grooming and leftover food. But this particular relationship is quite different.

Researchers liken it to homosexual monkey-monkey interactions, where female macaques mount each other. The females also mount the deer, using the same type of movement and the same vocalizations — so the deed appears sexual, at least for the monkeys. The deer, on the other hand, don’t seem as involved.

Some deer shook the macaques off. But others, especially adult male deer, let them do their thing. Some don’t even stop eating while the monkeys are humping them. Still, the acts were persistent and went way beyond mere thrusting or humping. The “monkey-to-deer solicitations … were persistent and conspicuous,” the researchers write. All in all, researchers documented 13 successful pairings and 258 separate mounts. So… what does it all mean?

Interspecies sexual relationships are not unheard of in the animal world, though generally, they’re between closely related species — nothing like this. The purpose of the act can’t possibly be reproductive, so the macaques are doing it for a different reason. Researchers have a few ideas.

The first is that this is a way for adolescent monkeys to start “learning sex” and/or explore their own sexuality. It could also just be a way for them to obtain sexual stimulation with no strings attached — something I’m sure many of us can empathize with. Younger female macaques have also been reported to have intercourse with each other, presumably for the same reasons. Another possibility is that they just don’t have any sexual partners available. Adolescent females are routinely rejected and are not considered desirable among the population.

Lastly, it could also be a non-sexual display. It might be a cultural phenomenon, a social fad. Time will tell, researchers say. They plan on carrying out more observations to detail the nature and purpose of this unusual behavior.

Journal Reference: Noëlle Gunst, Paul L. Vasey, Jean-Baptiste Leca. Deer Mates: A Quantitative Study of Heterospecific Sexual Behaviors Performed by Japanese Macaques Toward Sika Deer.

Macaques may have just entered the Stone Age

It took macaques in Thailand just 13 years to learn how to crack open nuts with rocks.

Yum yum! Image credits: Lydia Luncz.

There’s no official age for the beginning of the human Stone Age, but most anthropologists agree it started somewhere around 3.4 million years, ending 10,700 to 4,000 years ago, with the advent of metal working. Well, macaques seem to be entering that same period of their evolution. For over a century, macaques on the shore have been opening shells with rocks. Some of them moved inland and appeared to have figured out (and taught others) how to use rocks to open oil palm nuts.

What makes this behavior even more impressive is that oil palms have only been introduced to the area for 13 years. This means that within the span of 13 years, macaques figured out how to use rocks in a different setting. This could even mean that they’ve been in a Stone Age for a long time, since they have a deeper grasp of the rock-using process.

Using tools is not unheard of in the animal kingdom; on the contrary, there are a number of species which employ tools, from chimps to crows. But using stones is quite uncommon. In fact, only three species are known to do so: the western chimpanzees of West Africa, the bearded capuchins of Brazil and the long-tailed macaques of Thailand. But researchers thought this is strictly dependent on their particular environment — if they can move around and take the behavior with them, it paints a very different story.

“The chimpanzees live in tropical rainforest, and the capuchins in a dry savannah area,” says Lydia Luncz at the University of Oxford.

Meanwhile, the macaques live by Thailand’s seas, or at least spend a lot of time on the coast. However, they also like to roam inland. Luncz and colleagues followed the macaques through the Yao Noi Island in Thailand’s southern parts. They were ultimately led through an abandoned oil palm plantation, finding what appeared to be tools used to break nuts (hammer and anvil type rocks). Several broken nuts were found around the rocks. So they set up camera traps to see what was going on.

Thailand macaques have been cracking shells by the sea for decades. Image credits: Lydia Luncz.

Over the course of three weeks, they witnessed both male and female macaques visiting the sites, carefully placing the nuts on the anvil rocks and hitting them with the hammer rocks, until the delicious kernel was exposed. The fact that they’ve transferred this knowledge from sea shells to inland nuts is remarkable, but that they’ve done so in only 13 years at most is even more impressive.

It indicates that they understand the process. It might mean that they’ve truly entered the Stone Age.

“We know the macaques use stone tools at the shore – we believe they have transferred that behaviour to a new food source,” says Luncz. “They’ve applied what they know from the shore to a different ecosystem.”

“So this is the first nut-cracking macaque generation on the island,” she says.

A stone hammer and anvil used by macaques. Image credits: Lydia Luncz.

Elisabetta Visalberghi at the Institute of Cognitive Sciences and Technologies in Rome, Italy, says this is not surprising behavior, and macaques are known to be highly adaptable and intelligent. They exhibit a wide array of manipulative behaviors in order to get food, she says. She also points out that macaques have also been spotted cracking sea almonds produced by trees along the shore, so maybe it’s not such a large mental leap.

Yet even so, it’s an intriguing behavior which researchers would like to understand. Luncz and collaborators will now try to see how (if at all) the macaques’ stone usage is changing. Identifying an evolution would be a significant breakthrough, and the anthropogenic impact could greatly accelerate this evolution.

Journal Reference: Lydia V. Luncz Magdalena S. SvenssonMichael HaslamSuchinda MalaivijitnondTomos ProffittMichael Gumert. Technological Response of Wild Macaques (Macaca fascicularis) to Anthropogenic Change.  DOI: 10.1007/s10764-017-9985-6

Humans are not unique in understanding the basics of language

A paper published recently in Nature Communications details how a team led by Dr. Ben Wilson and Professor Chris Petkov used a brain imaging technique to identify the neuronal evolutionary origins of language. Their findings help us understand how we learn to speak, and could allow new treatments for those who lost this ability from aphasia following a stroke or dementia.

Image via wikimedia

By scanning the brains of macaque monkeys, the researchers identified an area in the front of the brain that, in both humans and macaques, recognizes a sequence of sounds as speech, and is responsible for analyzing if the sounds are in legal order or in an unexpected, illegal order.

“Young children learn the rules of language as they develop, even before they are able to produce language. So, we used a ‘made up’ language first developed to study infants, which our lab has shown the monkeys can also learn. We then determined how the human and monkey brain evaluates the sequences of sounds from this made up language,” said Professor Petkov.

Human and monkey subjects were played an example sequence from the made-up language, to hear the correct order in the sequence of sounds. After this they were played new sequences, some of which were in an incorrect order, and the team scanned their brains using fMRI. In both species, there was neuronal response in the same region of the brain — the ventral frontal and opercular cortex — when the sounds were correctly ordered.

The findings suggest that this region’s functionality is shared between humans and macaques, revealing a common cerebral evolutionary source. This brain region seems to monitor the orderliness or organization of sounds and words, which is an important cognitive function, at the core of the more complex language abilities of humans. The findings are the first scientific evidence that other animals share with us at least some of the functions this area serves, which include understanding language in humans.

“Identifying this similarity between the monkey and human brain is also key to understanding the brain regions that support language but are not unique to us and can be studied in animal models using state-of-the-art neuroscientific technologies,” Professor Petkov explains.

“This will help us answer questions on how we learn language and on what goes wrong when we lose language, for example after a brain injury, stroke or dementia.”

Building on these developments, the Newcastle University team, with their neurology collaborators in Cambridge and Reading Universities have begun a project to study the function of this brain region and its role in language impairment in aphasic patients with stroke, which might lead to better diagnosis and prognosis of language impairment.