Tiny nocturnal lemurs recognize their dad’s cries amid the other sounds of the nighttime Madagascar forests, a new study finds. The research is the first to show that solitary animals may avoid inbreeding by keeping an ear out for familiar voices.
Previous studies have found that animals living in complex social groups have no trouble recognizing their own kin’s calls, particularly the sounds of maternal relatives. Even goat mamas keep a long-term memory for their baby’s calls, according to a study published earlier this year.
But less is known about how animals recognize their father’s calls, and the cries of the relatives on dad’s side of the family. Likewise, researchers know very little about how solitary-living animals avoid inbreeding with dad’s side of the family.
That’s where the gray mouse lemur (Microcebus murinus) comes in. These cartoonishly cute lemurs are raised by their mothers without help from dad. When they grow up, they head out of the nest to forage on their own. But male lemurs’ ranges are large, and they often overlap with that of their daughters’, suggesting the primitive primates have evolved some way to avoid accidentally mating with a relative.
To find out how, researchers led by Arizona State University’s Sharon Kessler played male mating calls and alarm cries for 10 adult female gray mouse lemurs housed at the University of Veterinary Medicine in Hannover, Germany. Each lemur heard her father’s cries as well as an unrelated male’s. The researchers recorded how attentive the lemurs were to each call. For example, an interested lemur might stare at or run over to the speaker playing the call.
The female lemurs paid equal attention to alarm calls from fathers and unrelated males, the researchers report in an upcoming issue of the journal BMC Ecology. But when it came to mating calls, lady lemurs perked up much more at unrelated male’s calls. Compared to when they heard a father’s cry, the lemurs approached the non-kin speakers faster, sooner and stayed longer looking for the source of the sound.
The take-away, Kessler and her colleagues wrote, is that recognizing dad’s voice requires neither a big brain nor a complex social life. In fact, ability to recognize kin may have preceded complex social structures in evolutionary history.
A Wayne State University School of Medicine researcher is one step closer to understanding the genetic basis that enable bonobos, one of humankind’s sibling species, to learn language, play music and use rudimentary tools.
Derek Wildman, Ph.D., led a team that isolated the DNA and sequenced the genome, or whole inherited genetic make-up, of Kanzi, a bonobo based at the Bonobo Hope Great Ape Trust Sanctuary in Des Moines, Iowa. The sequencing, only the second of its kind, was performed at both WSU and an off-site private company.
Dr. Wildman is associate professor of Molecular Medicine and Genetics, and of Obstetrics and Gynecology. He is the director of the Molecular Evolution Group at WSU’s Center for Molecular Medicine and Genetics.
Kanzi, 32, was raised from birth in a family of five humans and eight bonobos, and was trained to use and understand simple spoken English to communicate. He also plays music, makes fire, cooks simple meals, and makes and uses flint knives. The goal of sequencing Kanzi’s genome is to understand the unique abilities of Kanzi and the other bonobos living at the sanctuary.
“We can compare Kanzi’s genome to the genomes of humans, and other primates in order to see what is unique about Kanzi from a genetic perspective,” Dr. Wildman said. “We also can see what Kanzi shares with other primates. Because we have also sequenced his transcriptome we can build gene models that are more accurate, and we can see which genes are expressed in his blood, and in the placenta of Kanzi’s son, Teco. This is a very important first step in untangling nature from nurture in the cognitive development of bonobos.”
“Orangutans, of their own volition, act out incredibly detailed scenarios with their bodies, using the pantomime to communicate with humans and other apes, according to a new study.
The study, published in the latest Royal Society Biology Letters, adds to the growing body of evidence that orangutan mini charade-like displays feature characteristics of language and reveal just how creative, intelligent and manipulative these great apes can be.”
One of Washoe’s caretakers was pregnant and missed work for many weeks after she miscarried. Roger Fouts recounts the following situation:
"People who should be there for her and aren’t are often given the cold shoulder—her way of informing them that she’s miffed at them. Washoe greeted Kat [the caretaker] in just this way when she finally returned to work with the chimps. Kat made her apologies to Washoe, then decided to tell her the truth, signing "MY BABY DIED." Washoe stared at her, then looked down. She finally peered into Kat’s eyes again and carefully signed "CRY", touching her cheek and drawing her finger down the path a tear would make on a human. (Chimpanzees don’t shed tears.) Kat later remarked that that one sign told her more about Washoe and her mental capabilities than all her longer, grammatically perfect sentences."
(Note: Washoe herself lost two children; one baby died shortly after birth of a heart defect, the other baby, Sequoyah, died of a staph infection at two months of age.)
Chimpanzees have a bad reputation. Maybe it’s because humans have a thing about wanting to feel unique among primates. Some have argued that humans are the only species that truly behaves altruistically, the only species that actively helps out other individuals even when there is no direct benefit. Despite mounting evidence that other animals, including non-human primates, have various forms of theory of mind, many still believe that human altruism exists because we – and we alone among all the animal kingdom – can understand the goals of others. Or, if there are other animals that can understand the goals of others, perhaps we somehow do it more readily.
In a new paper just published in PNAS, primatologist Shinya Yamamotoa and colleagues point out that while chimpanzees are known to help others, they don’t usually help when it would mean giving up things like food, even if they’ve got more food than they need. Even between a mother and her infant!
Why do chimpanzees seem so reluctant to help others? One possible explanation is that they’re unable to understand the goals of another individual, resulting in an inability to create any sort of shared intentionality between two individuals. To that end, the researchers write, “many still believe that humans are unique in this respect because we are the only animal species endowed with unique ‘theory of mind’ abilities enabling us to understand the goals and to share the intentions of others.”
Yamamotoa and the other researchers set up an experiment designed explicitly to address this possibility. The first chimpanzee was given a task to accomplish in order to receive a juice reward. The task required the use of one of two types of tools: a stick or a straw. The stick and the straw, however, as well as five other items were found not in the first chimpanzee’s booth, but in the second chimp’s booth. There was a small opening between the two booths where the second chimp could pass the necessary tool to the first. By itself, this could test whether or not the second chimp was willing to help the first chimp.
But to see whether the ability to understand the goal of another individual modulates the potential to help, the researchers created two further conditions: half the time, the barrier separating the two booths was a transparent window, and half the time it was a completely opaque wall. If chimpanzees modulate their responses to a help request based on whether or not they can see the goal of another individual, then they should give the appropriate tool more often when in the transparent window condition.
During the transparent window condition, the chimpanzees were more likely to offer up the appropriate tool (e.g. a stick during the stick condition, or a straw during the straw condition) than any of the other tools. This result itself shows that the chimpanzees were able to understand which tool their partner would need in order to solve a given task. Importantly, ninety percent of tool offers occurred only after a request was given by the first chimpanzee, suggesting that while chimpanzees may not spontaneously engage in helping behaviors, direct requests are effective in soliciting assistance.
Chimps know what tools others need to get work done and can help them select the right instruments, suggesting the apes have the ability to understand the minds of others, scientists find.
The capability to consider the goals and share the perspective of others, known as “theory of mind,” has long been considered unique to humans. This aptitude may be why humans cooperate in an altruistic, “prosocial” manner to develop societies.
“Humans sometimes help others just upon witnessing others’ predicaments — donations for tsunami and earthquake victims are a typical case,” said researcher Shinya Yamamoto, a primatologist at Kyoto University in Japan.
The Philippine tarsier, a small nocturnal animal, has the world’s highest pitched primate vocalization ever documented.
The distinctive tiny tarsier possesses large eyes relative to its body as well as the world’s highest frequency primate call. Hear that call here.
"Tarsiers are among only a handful of mammals that are known to communicate in the pure ultrasound,” lead author of a paper in the Royal Society’s Biology Letters, Marissa Ramsier, told Discovery News. “No other primate is known to produce and detect signals as high as the tarsier.”
Ramsier, co-director of the Biological Anthropology Research Lab at Humboldt State University, and her colleagues, made the determination after studying six tarsiers that were captured in the vicinity of Motorpool, Surigao del Norte, Mindanao, Philippines.
To estimate auditory sensitivities, the researchers first used a minimally invasive brainstem response test. This showed that the primates can hear in the ultrasound range, up to 91 kHz. For comparison, humans have a high-frequency detection limit of only about 20 kHz.
Next, the scientists recorded vocalizations made by the tarsiers. In some cases, the tarsiers were opening and closing their mouths, looking like they were communicating, but no sound was heard. Sensitive high tech recording equipment revealed that the primates were indeed communicating, but in ultrasound frequencies.
Philippine tarsiers join a select group of mammals that have this ability. The group includes certain bats, rodents, cetaceans and even domestic cats. Ramsier explained that “kittens produce a pure ultrasonic call from about 2-6 weeks of life when they are first exploring their environment, and a mother cat produces its own purely ultrasonic call in response to the kitten.” Cats at these times of life can therefore communicate in ways not detected by their owners, “unless they follow them around with a bat detector.”
All of these ultrasound-producing animals can then communicate within their own private “channel,” which could prevent detection by predators, prey and competitors. It could also enhance energetic efficiency and improve detection against low-frequency background noise.
Humans, on the other hand, may have no evolutionary advantage to producing and detecting ultrasound.
"Humans are big and noisy," Ramsier said. "If a predator is nearby, it will likely see and hear us."
Conversely, tarsiers are small and active during the night, so it is relatively easy for them to use masked vocalizations as a covert strategy. Ramsier thinks they do this by constriction of their larynx and rapid opening and closing of their vocal chords. They probably have special auditory features that enable hearing of ultrasound.
Chris Kirk, an associate professor in the department of anthropology at the University of Texas at Austin, told Discovery News that this “study is important because it expands the number of primate species that concentrate a large part of the acoustic energy in their vocal communications within the ultrasonic range.”
Kirk continued that one of the documented tarsier calls look to be a classic “ventriloquial” call, meaning a vocalization that conceals the location of the sender.
"In fact, it looks an awful lot like the ‘seet’ alarm calls or (those of) passerine birds, but scaled up to a higher frequency range," he said.
Ramsier and her team also suspect that the tarsier ultrasound calls are alarms, especially since the little primates only emitted the vocalizations when they were near humans during the study.
Lead researcher Dr Bridget Waller explained that non-human primates have two expressions “that shed light on our smiling”.
Their “playface”, she explained, appears to be a foundation of human laughter.
Dr Waller told BBC Nature: “[During play, gorillas] open their mouths and cover their teeth as if to say, ‘I could bite you but I’m not going to’.”
Another expression the primates use, where they reveal both rows of “sparkly white teeth” is believed to show one of the origins of human smiling.
This is not a playful expression, Dr Waller said. “It’s a greeting; a subordinate display.”
The different contexts in which gorillas use these facial expressions reveals that smiling and laughing are probably rooted in very different “ancestral displays”, as Dr Waller explained.
"People think we smile when we’re happy, but that’s not true," she told BBC Nature.
"You smile when its appropriate in a situation. You smile at someone in the corridor - you don’t laugh at them."
Dr Waller and her colleagues wanted to find out more about the contexts in which these two expressions combined; when gorillas flashed their upper teeth as they played.
Watching the animals revealed that they would do this during particularly “rough” and intense play and they would play for longer when they bared their teeth.
"It’s possibly because, when play gets rough, you need an extra signal to show each other that [you’re] just playing," Dr Waller said.
The findings, she said, showed the foundation of people’s social laughter; when humans laugh along in conversation to put one another at ease.
"I always think of facial signals as about reducing uncertainty," said Dr Waller. "We use [these] non-verbal signals all the time."
Prof Richard Byrne, an expert on primate communication and behaviour from the University of St Andrews said it was interesting to study the facial expressions of non-human primates because most of our our own expressions “seem to be ‘primitive’, in the main”.
"Superficially [their] expressions may look a bit different because the ape or monkey faces are so different to our own," he said.
"But when examined properly, most human expressions have proved to be shared with quite distantly related primate species - and therefore must derive from an ancient shared ancestor."
Chimpanzees appear to consider who they are “talking to” before they call out.
Researchers found that wild chimps that spotted a poisonous snake were more likely to make their “alert call” in the presence of a chimp that had not seen the threat.
This indicates that the animals “understand the mindset” of others.
The insight into the primates’ remarkable intelligence will be published in the journal Current Biology.
The University of St Andrews scientists, who carried out the work, study primate communication to uncover some of the origins of human language.
To find out how the animals “talked to each other” about potential threats, they placed plastic snakes - models of rhino and gaboon vipers - into the paths of wild chimpanzees and monitored the primates’ reactions.
"These [snake species] are well camouflaged and they have a deadly bite," explained Dr Catherine Crockford from University of St Andrews, who led the research.
"They also tend to sit in one place for weeks. So if a chimp discovers a snake, it makes sense for that animal to let everyone else know where [it] is."
The scientists put the snake on a path that the chimps were using regularly, secreting the plastic models in the leaves.
"When [the chimps] saw the model, they would be quite close to it and would leap away, but they wouldn’t call," she told BBC Nature.
"It wasn’t a knee-jerk reaction."
After leaping away, each chimp immediately, very carefully, approached the snake again. And this time, they would make a soft “hoo” sound if they were close to a chimp that was not aware the snake was there.
"We monitored the snake all day, so we knew which animals had seen it and which hadn’t," Dr Crockford explained.
She added that when the primates called out, They were “very focused on their audience”.
"That’s not entirely new," she said.
"Lots of animals give alarm calls and are more likely to give an alarm call [when another animal is present]."
But what is new here, she continued, is that “they seem tuned, not into who the audience is, but to what the audience knows”.
These findings, Dr Crockford said, provide an important insight into a factor that may have “kick-started” complex communication.
She explained: “Why would I bother to communicate something to you unless I realised that you didn’t already know it?”
"Now we have seen that these chimps, human’s close relatives, seem to recognise ignorance and knowledge in others.
And they’re motivated to communicate missing and relevant information to that individual.
It’s one of the things that’s been missing from the evolution of language story.”
Matthew Cobb, professor of zoology at the University of Manchester, explained that “imagining what another individual is thinking” is a crucial part of human language.
"This study gives us some insight into how this amazing ability may have evolved," he told BBC Nature.
"In the wild, faced with a natural stimulus, our close cousins the chimps alter their communication depending on what other chimps know.
It appears that humans aren’t quite so unique, after all.”