Science Briefs: Animal Activity Edition

A roundup of the latest news in strange animal traits

Graphic by Aldo Rios.

A recent study by scientists at Duke University, Kyoto University, and the Max Planck Institute for Evolutionary Anthropology has provided evidence that great apes (bonobos, chimpanzees, and orangutans) have even more in common with humans that previously thought.

It’s called “theory of mind,” and it’s the real-world equivalent to mind reading. When you can guess what someone else may be thinking, or assume what they’re going to say next, that’s theory of mind. It’s the ability to assume that other people possess thoughts and ideas, and that they may be different from your own. While this was originally considered to be a specifically human trait, new research shows what looks like a similar thought process happening in great apes.

The great ape experiment was framed similarly. This experiment, which was called a “litmus test” by Fumihiro Kano, the co-leader of the study, uses a greatly simplified version of the human test.

In the ape test, bonobos, chimps, and orangutans were treated to a movie and juice. Using a video monitor, they were shown two separate scenarios. In the first, a researcher in a gorilla suit would wildly attack a human researcher. The “gorilla” would then dramatically hide in one of two hay bales, then move to the other, and the video would make it obvious that the human researcher was aware of this. The researcher would leave, and while the researcher was gone, the gorilla would leave too. The researcher would then return brandishing a stick, searching for the gorilla in the hay bales. There were other scenarios used as well, one involving the gorilla hiding in the hay bales in a different order, and another involving the gorilla-suited character hiding a stolen rock.

With the use of an infrared eye-tracker, the researchers were able to track the ape’s eye movements, and used this to concur what they were thinking. In every test, the apes passed, meaning the apes looked at the place where the human researcher last saw the gorilla or the rock. Thus, according to researchers, correctly judging the researcher’s thought process, understanding that the human actor possessed a belief that the ape knew to be false, and anticipating that the human character was going to search for the gorilla or rock there.

“Great apes didn’t just develop these skills this year, of course, but the use of novel eye-tracking techniques allowed us to probe the question in a new way,” Christopher Krupenye, co-author of the study, wrote for the Conversation.

“By using methods that for the first time assessed apes’ spontaneous predictions in a classic false belief scenario – with minimal demands on their other cognitive abilities – we were able to show that apes knew what was going to happen.”

The experiment is not without its skeptics, however, with some suggesting that while the ape may realize that the human will look where the human last saw it, this does not necessarily imply that the ape consciously knows that the human possesses a “false belief.”

The authors of the study agree that more research is needed, but are hopeful that this discovery could lead to a heightened understanding of our closest relatives and of our own evolutionary timeline.

“At the very least, in several different scenarios, these apes were able to correctly predict that an individual would search for an object where he falsely believed it to be,” Krupenye writes.

“These findings raise the possibility that the capacity to understand others’ false beliefs may not be unique to humans after all.”


Naked mole rat’s superhuman ability an evolutionary trait

Naked mole rats are an interesting species. They survive in harsh conditions, weathering the dry grasslands of east Africa. They’re the first mammals ever discovered to exhibit eurosexuality, meaning that like bees or termites, they live in immense colonies and have a queen, which is the only naked mole rat to reproduce. Their average lifespan is into their thirties, and they almost never get cancer.

One of their most interesting qualities, however, is their incredible resistance to pain, and new research finally explains why the naked mole rat barely feels pain that would anguish nearly any other animal.

The study, published in the journal Cell Reports, suggests that through evolutionary adaptation, naked mole rats have developed to ability to only feel just enough pain to signal danger, but not much more.

These adaptations, caused by changes in the amino acids in their pain receptors, are the reason why despite the hot weather in east Africa, and the naked mole rat’s nakedness, they do not seem to suffer from the effects of thermal hyperalgesia.

Thermal hyperalgesia, which is basically heat sensitivity, is why it hurts more than usual if you put hot water on a burn, or step into the shower after a long day out in the sun. It occurs when a previous burn causes higher sensitivity in the skin affected by the burn. Naked mole rats get thermal hyperalgesia too – the constant skin-to-skin contact with other naked mole rats only exacerbates this – but they do not seem to feel the pain that we do.

Scientists have isolated the receptor that gives the naked mole rat their heightened pain resistance, called TrkA. This receptor receives something called nerve growth factor (NGF) molecules when the animal host experiences high heat temperatures. This in turn alerts sensory nerves to let the brain know that this level of heat is causing the body pain.

The TrkA receptor works differently in a naked mole rat, however. In this experiment, researchers exposed naked mole rat nerve cells to a chemical found in hot chili peppers, and found that due to the difference in their TrkA receptor’s amino acids, the naked mole rat was not able to feel pain due to heat sensitivity. In fact, it took 10 times the amount of a normal rat’s NGF for the naked mole rat to feel any pain at all.

Gary R. Lewin, professor at the Max-Delbruck Center for Molecular Medicine in Berlin and lead author on the study, believes that these findings could have a great impact on how we treat humans suffering with chronic pain in the future.

“This study is not going to tell them how to do that,” he said. “But I think it’s cool that 30 million years ago, the naked mole rat figured it all out. Evolution has already done it.”


Poachers suggested to have a direct effect on elephant development

A video posted just last week by the Howard Hughes Medical Institute (HHMI) suggests that more and more female African elephants are not growing tusks – and poachers are to blame.

While tusks are an important part of elephant’s development, and are used as tools by the elephant, around two to six per cent of female elephants never grow them.

Dr. Joyce Poole, who is featured in the HHMI’s video studying Gorongosa National Park in Mozambique, suggests that poaching has caused a sort of rapid natural selection to occur in elephants.

“Tusklessness, just like having tusks, is a natural trait,” Poole said. “And it’s inherited, like bigger ears or smaller ears, like brown eyes or blue eyes. It’s an inherited trait.”

Hunting elephants for their tusks, which are still used today to make ivory, was a large factor in Mozambique’s civil war, which lasted 15 years and ended in 1992. Researchers in Mozambique believe that the civil war changed the elephant population drastically.

“Gorongosa’s elephants are very special,” said Dominique Demille, a research fellow on the Gorongosa Restoration Project.

“The older ones still remember what happened in the past: the war, the soldiers that hunted elephants for their ivory.”

While two to six percent of all female elephants (male elephants need their tusks to fight, and are thus less likely to not grow them) are tuskless, about half of all female elephants that were alive during the civil war in Mozambique are tuskless. This, along with the fact that tusk growth in elephants in inherited, could be signs that all tusk growth in female elephants has been greatly affected by poachers. About a third of younger female elephants in Gorongosa National Park who were born after the civil war are tuskless.


To learn more about the destructive effects of poaching on elephants and other African wildlife, and what you can do to help, visit