Category: Animal intelligence

Q: Why don’t apes have bigger brains? A: They can’t eat enough to afford them

By Ed Yong | October 23, 2012 9:00 am

As animals get bigger, so do their brains. But the human brain is seven times bigger than that of other similarly sized animals. Our close relative, the chimpanzee, has a brain that’s just twice as big as expected for its size. And the gorilla, which can grow to be three times bigger than us, has a smaller brain than we do.

Many scientists ask why our brains have become so big. But Karina Fonseca-Azevedo and Suzana Herculano-Houzel from the Federal University of Rio de Janeiro have turned that question on its head—they want to know why other apes haven’t evolved bigger brains. (Yes, humans are apes; for this piece, I am using “apes” to mean “apes other than us”).

Their argument is simple: brains demand exceptional amounts of energy. Each gram of brain uses up more energy than each gram of body. And bigger brains, which have more neurons, consume more fuel. On their typical diets of raw foods, great apes can’t afford to fuel more neurons than they already have. To do so, they would need to spend an implausible amount of time on foraging and feeding. An ape can’t evolve a brain as big as a human’s, while still eating like an ape. Their energy budget simply wouldn’t balance.

Read More

NOC, the white whale that tried to sound like a human

By Ed Yong | October 22, 2012 12:00 pm


Listen to this recording. It sounds like a drunkard playing a kazoo, but it’s actually the call of a beluga (a white whale) called NOC. Belugas don’t normally sound like that; instead, NOC’s handlers think that his bizarre sounds were an attempt at mimicking the sounds of human speech.

The idea isn’t far-fetched. Belugas are so vocal that they’re often called “sea canaries”. William Schevill and Barbara Lawrence – the first scientists to study beluga sounds in the wild – wrote that the calls would occasionally “suggest a crowd of children shouting in the distance”. Ever since, there have been many anecdotes that these animals could mimic human voices, including claims that Lagosi, a male beluga at Vancouver Aquarium, could speak his own name. But until now, no one had done the key experiment. No one had recorded a beluga doing its alleged human impression, and analysed the call’s acoustic features.

Read More

Smarter than the average crow, or just equipped with a face for fishing?

By Ed Yong | October 9, 2012 11:00 am

Our intelligence clearly surpasses those of our primate relatives, even though other apes and monkeys also rank within the highest tiers of animal smarts. Likewise, the corvids – the group of birds that includes crows, ravens, rooks, magpies and jays – have very sophisticated brains for birds, but one species reputedly outclasses the rest. It’s the New Caledonian crow.

Found in a Pacific island, this crow wields tools in a way that none of its relatives can match. It uses sticks to “fish” for grubs buried in dead wood, and can chosen the right tool for different jobs, combine tools together, and improvise from unusual materials. These abilities have fuelled the New Caledonian crow’s reputation as the top of the corvid class – an unusually intelligent member of an already intelligent family.

But what if it just has the right face?

If I wanted to fish for a grub, I can use my dextrous hands while moving my face around so I can see what I’m doing. The crow only has its beak, which is attached to its face. But Jolyon Troscianko from the University of Birmingham has shown that it has two features that make the job easier: an unusually straight bill, and an extreme overlap between what both eyes can see. These physical traits set it apart from other crows and corvids, and give it an edge when using tools.

Read More

Brainless creature solves problems with memories of slime

By Ed Yong | October 8, 2012 3:00 pm

Every time we walk through a field or forest, we imprint a memory onto the land by trampling the vegetation beneath our feet. These trails can be strengthened by the erosive feet of later walkers, or diminished by re-growing plants. Over time, they act as a collective memory of the routes taken by everyone who has previously walked in that area. The path from A to B has been etched into the ground; no single person needs to store it in their brain.

This sort of “externalised memory” is particularly helpful when you have no brain at all.

The slime mould Physarum polycephalum belongs to the same kingdom of life as the famous Amoeba. is a yellow blob that looks like it just oozed out of a B-movie, or possibly someone’s digestive tract. It has neither neurons nor brains, but it’s capable of seemingly “intelligent” behaviour – solving mazes, making decisions, and efficiently simulating the transport networks of various countries.

Now, Chris Reid from the University of Sydney has added another ability to the slime mould’s list: an external memory, written in trails of slime, that helps the creature navigate through its environment in sophisticated ways.  Reid suggests that these types of external memories may have preceded the evolution of our more familiar internal ones.

Read More

CATEGORIZED UNDER: Animal intelligence

Same gene linked to bigger brains of dolphins and primates

By Ed Yong | September 11, 2012 7:00 pm

Every whale and dolphin evolved from a deer-like animal with slender, hoofed legs, which lived between 53 and 56 million years ago. Over time, these ancestral creatures became more streamlined, and their tails widened into flukes. They lost their hind limbs, and their front ones became paddles. And they became smarter. Today, whales and dolphins – collectively known as cetaceans – are among the most intelligent of mammals, with smarts that rival our own primate relatives.

Now, Shixia Xu from Nanjing Normal University has found that a gene called ASPM seems to have played an important role in the evolution of cetacean brains. The gene shows clear signatures of adaptive change at two points in history, when the brains of some cetaceans ballooned in size. But ASPM has also been linked to the evolution of bigger brains in another branch of the mammal family tree – ours. It went through similar bursts of accelerated evolution in the great apes, and especially in our own ancestors after they split away from chimpanzees.

It seems that both primates and cetaceans—the intellectual heavyweights of the animal world—could owe our bulging brains to changes in the same gene. “It’s a significant result,” says Michael McGowen, who studies the genetic evolution of whales at Wayne State University. “The work on ASPM shows clear evidence of adaptive evolution, and adds to the growing evidence of convergence between primates and cetaceans from a molecular perspective.”

Read More

Unlike humans, chimpanzees only punish when they’ve been personally wronged

By Ed Yong | August 27, 2012 3:00 pm

When Delta Airlines refused to let Arijit Guha board a plane because his T-shirt made passengers uncomfortable, others made Delta aware of their outrage. When Samsung infringed Apple’s copyright, a jury of independent peers awarded Apple more than $1 billion in damages. When Republican Todd Akin claimed that women could stop themselves from becoming pregnant if raped, people called for his head.

These recent events all illustrate a broad human trait: we seek to punish people who do wrong and violate our social rules, even when their actions don’t harm us directly. We call for retribution, even if we have nothing specific to gain from it and even if it costs us time, effort, status or money to do so. This “third-party punishment” is thought to cement human societies together, and prevents cheats and free-riders from running riot. If you wrong someone, and they’re the only ones who want to sanction you, the price of vice is low. If an entire society condemns you, the cost skyrockets.

Do other animals do the same thing? It’s not clear, but one group of scientists believes that our closest relative – the chimpanzee – does not. Katrin Riedl from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany found that chimpanzees will punish individuals who steal food from them, but not those who steal food from others. Even if the victim was a close relative, the third party never sought to punish the thief. These were the first direct tests of third-party punishment in a non-human animal, and the chimps got an F.

Read More

Dolphins that help humans to catch fish form tighter social networks

By Ed Yong | May 1, 2012 7:00 pm

In the coastal waters of Laguna, Brazil, a shoal of mullet is in serious trouble. Two of the most intelligent species on the planet – humans and bottlenose dolphins – are conspiring to kill them. The dolphins drive the mullet towards the fishermen, who stand waist-deep in water holding nets. The humans cannot see the fish through the turbid water. They must wait for their accomplices.

As the fish approach, the dolphins signal to the humans by rolling at the surface, or slapping the water with their heads or tails. The nets are cast, and the mullet are snared. Some manage to escape, but in breaking formation, they are easy prey for the dolphins.

According to town records, this alliance began in 1847, and involves at least three generations of both humans and dolphins. Today, there are around 55 dolphins in the neighbourhood, and around 45 per cent of them interact with the fishermen.

Now, Fabio Daura-Jorge from the Federal University of Santa Catarina, Brazil studied Laguna’s dolphins to learn how their unusual collaboration has shaped their social networks. He spent two years taking photographs of the local dolphins, and noting where they travelled and who they were associated with. As is typical for bottlenose dolphins, the Laguna individuals formed a ‘fission-fusion’ society – they all belonged to the same large group, but they had specific ‘friends’ whom they would spend more time with.

The dolphins roughly split into two separate groups, based on their tendency to hunt with humans. Those that co-operated with the fishermen were more likely to spend time with each other than the uncooperative individuals. Likewise, the uncooperative dolphins showed a tendency to stick to their own clique.

One individual even seemed to act as a “social broker”, and spent time with individuals from both groups.

Of the two groups, the human-helpers seemed to form stronger social ties. It is not clear if helping humans means they spend more time together, or vice versa. But certainly, their close associations increase the odds that one dolphin will learn the hunting technique from its peers.

This fits with what we know about bottlenose dolphins. They are extremely intelligent animals and different populations have developed their own quirky foraging traditions by learning from one another. Some use sponges to guard their snouts when they root about the ocean floor for food. Others can prepare a cuttlefish meal by sequentially killing and stripping them.

Daura-Jorge now wants to understand why only some of the dolphins help the fishermen, given that doing so clearly provides them with benefits, and all of them have the opportunity to help. By analysing the dolphins’ genes, he hopes to piece together their family trees, and work out if mothers pass on the behaviour to their calves.


Reference: Daura-Jorge, Cantor, Ingram, Lusseau & Simoes-Lopes. 2012. The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen. Biology Letters

Bonus: There are several cases around the world where dolphins feed on the discarded remains of fish thrown away by humans. But the Laguna animals do far more than that – the fisherman wouldn’t catch any fish at all without their help. A similar alliance takes place half a world away in Burma, where Irrawaddy dolphins also fish cooperatively with humans.

More on dolphin behaviour:

How orangutan engineers build safe and comfortable treetop beds

By Ed Yong | April 16, 2012 3:00 pm

We normally think of nests as the creations of birds, but our ape cousins build nests too. Orangutans, gorillas, chimpanzees and bonobos all build tree beds, by weaving branches, twigs and leaves together into a bowl-shaped cradle. These nests may provide safety from predators, or help the apes to sleep warm.* But it seems that their main function is to provide a good night’s rest. Sleeping against a tree bough is hard on a large ape, and nests offer a more comfortable option.

Of all the apes, orangutans reputedly create the sturdiest and most elaborate nests. By studying the physical properties of these treetop bunks, Adam van Casteren from the University of Manchester has found that the apes are skilled engineers. As befits animals of their intelligence, they don’t just mash branches together. Instead, they seem to have an impressive amount of technical knowledge about their construction materials.

Orangutans build their nests between 11 and 20 metres up. Once they choose a good spot on a sturdy branch, they bend or break other branches in towards them, and weave them in place to create a basic foundation. On top of that, they add smaller branches to create a ‘mattress’. That’s the basic model, and some orangutans add deluxe features. They can create blankets, by covering themselves with large leafy branches, or pillows, by clumping such branches together. They can loosely braid branches above their heads to make a roof, or even create a secondary ‘bunk-nest’ over the main one.

Like all apes, orangutans construct new ones every day. This means that intrepid scientists have plenty of old discarded nests to study. Van Casteren, along with Julia Myatt from the Royal Veterinary College, found 14 such nests in the Sumatran rainforest. They hoisted themselves into the canopy, attached ropes to different parts of the nests, and lowered these to the ground where team members were waiting with force gauges. “Climbing up into the high canopy is breathtaking,” says van Casteren. “You enter an area of the forest that isn’t used to having humans hang around in it.”


Van Casteren found that orangutans use thicker branches in the structural foundation of the nest, and thinner branches in the mattress. The structural ones are four times stronger and four times more rigid, and they make the nest sturdy. The mattress branches are thinner and more flexible for comfort.

The orangutans also break the two types of branches in different ways. If you bend a dense branch, it will only break halfway – this is known as a “greenstick fracture (see below). That’s what van Casteren found in the structural part of the nest. Once broken like this, it’s surprisingly hard to fully snap a branch in two, even for a powerful animal like an orangutan. The trick is to twist the branch. The fracture extends outwards until the two halves come apart, producing two pieces with long tapered ‘tails’.  Van Casteren filmed the apes using this technique, and the found plenty of the distinctive tailed branches in their mattresses.

There are plenty of questions about the nests left to answer. For example, orangutans don’t choose their trees randomly, and actually avoid the most common species. What’s special about the ones they pick, and does that factor into the properties of the nests? The apes also learn their craft from adults, so do immature orangutans build nests with less distinctive foundations and mattresses? Van Casteren also wants to look at the nests of other great apes, and of other architects such as beaver or birds, to see if he gets similar results.

But for now, his data already show that orangutans make sophisticated technical choices when they build their nests. He thinks that they account for the different properties of the materials in their environment, and use those properties to make bunks that are both safe and comfortable. While many studies of animal intelligence focus on the use of tools, he argues that nest-building is no less mentally demanding.

Roland Ennos, who was involved in the study, says, “I hope helps to show how the evolution of intelligence can be driven by the need to deal with the mechanical environment, rather than the prevailing orthodoxy that it’s only the social environment that’s important.”

* In writing this story, I stumbled across a wonderful study by Fiona Stewart from the University of Cambridge, who tested the value of chimpanzee nests, by sleeping in them. She spent several nights in Senegal either sleeping in newly made chimp beds or on the bare ground. She was warmer in the nests, and received fewer insect bites. She didn’t get any more sleep, but what she got was less disturbed. “Terrestrial animals, including hyenas, were more concerning during ground sleep, although snakes were always a concern,” she writes, in a wonderfully deadpan way. Van Casteren, however, never tried to sleep in the orangutan nests that he studied. They are higher than a chimp’s and he was “too worried about falling out mid-dream”.

Reference: Van Casteren, Sellers, Thorpe, Coward, Crompton, Myatt & Ennos. 2012. Nest-building orangutans demonstrate engineering know-how to produce safe, comfortable beds. PNAS

Images courtesy of Adam van Casteren

More on orangutans


Will we ever… talk to dolphins?

By Ed Yong | March 27, 2012 9:00 am

Here’s the fourth piece from my new BBC column

“What’s that Flipper? The treasure is over there?” So went a typical plotline for the popular TV series featuring the cute, bottlenosed dolphin who could communicate with his human guardians, and who – in the time-honoured fashion – used his animal powers to apprehend criminals.

The idea that animals like Flipper can communicate with humans is not just the preserve of the small and big screen. History is littered with celebrity animals who have communicated with human scientists, with varying degrees of success. Many apes, including Washoe and Nim the chimps, and Kanzi the bonobo, have learned to communicate by using sign language or symbols on a keyboard. Alex, an African grey parrot learned over 100 English words, which he could use and combine appropriately; his poignant last words to Irene Pepperberg, his scientist handler, were “You be good. I love you. See you tomorrow.”

Dolphins hold a particular fascination; we are captivated by their intelligence and beauty, and swimming with dolphins features regularly on lists of things to do before you die. Denise Herzing has a lifetime of such experiences. For the last 27 years, she has been swimming with a group of Atlantic spotted dolphins in Florida as part of the Wild Dolphin Project. She can identify every individual and they, in turn, seem to trust and recognise her. It is a solid foundation for the boldest attempt yet to talk with dolphins.

One-way chat

“Talk” is tricky to define. A SeaWorld trainer who prompts a dolphin to jump for fish is arguably communicating with it. But such simple one-way interactions are a far cry from the conversational world of Dr Doolittle. Here, the dolphin responds, but says nothing intelligible back. Herzing’s vision is much more ambitious – she wants to establish two-way communication with her dolphins, with both species exchanging and understanding information.

The idea of talking to dolphins has a long and chequered history. It was widely publicised in the 1960s by John Lilly, who argued that dolphins have such large brains that they must be extremely intelligent and have a natural language. All we had to do was to “crack the code”. Much of Lilly’s work was highly questionable. He once flooded a house to keep a captive dolphin, instigated failed attempts to teach them spoken English, and even gave the animals LSD (while taking the drug himself). But there is no denying his influence in popularising the idea of two-way dolphin communication. “He said that in a few years, we will have established complex dialogue with them,” says Justin Gregg from the Dolphin Communication Project. “And he was saying that every few years.”

Lilly was right about dolphin intelligence, but not dolphin language. A true language involves small elements that combine into larger chains, to convey complex, and sometimes abstract, information. And there is no good evidence that dolphins have that, despite their rich repertoire of whistles and clicks.

Little less conversation

Wild dolphin communication is hard to study. They are fast-moving and hard to follow. They travel in groups, making it hard to assign any call to a specific individual. And they communicate at frequencies beyond what humans can hear. Despite these challenges, there is some evidence that dolphins use sounds to represent concepts. Each individual has its own “signature whistle” which might act like a name. Developed in the first year of life, dolphins use these whistles as badges of identity, and may modulate them to reflect motivation and mood. This year, a study showed that when wild dolphins meet, one member of each group exchanges signature whistles.

But beyond this, dolphin chat is still largely mysterious. “To communicate with dolphins, we need to understand how they communicate with each other in the natural world,” says psychologist Stan Kuczaj at the University of Southern Mississippi. “We still don’t know basic things like what the units of dolphin communication are. Is a whistle the equivalent of a “word” or a “short sentence”? We don’t know.”

We may not be able to understand them yet, but we know that dolphins can learn to understand us. In the 1970s, Louis Herman taught an invented sign language, complete with basic syntax, to a bottlenose dolphin called Akeakamai. For example, if he made the gestures for “person surfboard fetch”, Akeakamai would bring the board to him, while “surfboard person fetch” would prompt her to carry the person to the board. His experiments showed that dolphins could understand hundreds of words, and how those words could be combined using grammatical rules.

What’s my motivation?

Herman’s work was groundbreaking, but this was still one-way communication. It focused on comprehension, not conversation. In the 1980s, Diana Reiss had more luck by showing that dolphins could use underwater keyboards to make basic requests. When they prodded keys with their snouts, a whistle would play and Reiss gave a reward like a ball. Eventually, the dolphins used the artificial whistles to ask for the associated rewards.

But as conversations go, these were shallow ones. “The dolphins were only really interested in communicating about needs that they had, like a tool they needed or a fish they wanted,” says Kuczaj, who was involved in a similar project at DisneyWorld’s EPCOT Center. “We hoped they would also comment on other things going on in the aquarium but they didn’t.”

It is difficult persuading dolphins to learn some arbitrary signals, like a whistle signifying a ball, and then use them in a social context, admits Gregg. “They don’t seem to run with it the same way that chimps or bonobos have. The big stumbling block is motivation. Dolphins don’t seem to care.”

Herzing disagrees. She notes that captive animals, which often lack stimulation, will respond to systems like the underwater keyboards. She thinks that these experiments disappointed because they were cumbersome. “The dolphins swim very fast and went to where they were requested, but humans are very slow in the water. There wasn’t enough real-time interaction.”

Chat line

Herzing is trying to solve that problem with Cetacean Hearing and Telemetry (CHAT) – a lighter, portable version of the underwater keyboards. It consists of a small phone-sized computer, strapped to a diver’s chest and connected to two underwater recorders, or hydrophones. The computer will detect and differentiate dolphin sounds, including the ultrasonic ones we cannot hear, and use flashing lights to tell the diver which animal made the call.

The CHAT device can also play artificial calls, allowing Herzing to coin dolphin-esque “words” for things that are relevant to them, like “seaweed” or “wave-surfing”. She hopes the dolphins will mimic the artificial whistles, and use them voluntarily. By working with wild animals, and focusing on objects in their natural environment, rather than balls or hoops, Herzing hopes to pique their interest.

Herzing emphasises that her device is not a translator. It will not act as a dolphin-human Rosetta stone. Instead, she wants both species create a joint form of communication that they are both invested in. She hopes that CHAT will tap into the “natural propensity” that dolphins have “for creating common information when they have to interact”. For example, in Costa Rica, distantly related bottlenose and Guyana dolphins will adopt a shared collection of sounds when they come together, using sounds that they don’t use when apart.

As with past projects, all of this depends on whether the dolphins play along. Kuczaj says, “It’s a remarkable challenge because she is working with wild dolphins so they’ve got the option to participate or not.” Here, Herzing has an edge, since the animals know her, and vice versa. “We’ve been observing them underwater every summer since 1985,” she says. “I know the individuals personally – their personalities and relationships. We’ve got a pretty good handle on what they’d be interested in.” Perhaps this combination of cutting-edge technology and old-school fieldwork will finally produce the conversations that have eluded scientists for so long.

Why humans stand on giant shoulders, but chimps and monkeys don’t

By Ed Yong | March 1, 2012 2:00 pm

We are like dwarves standing on the shoulders of giants. This metaphor, famously used by Isaac Newton, describes how humans build on what has come before. Everything in our culture is the result of knowledge and skills that have slowly accumulated over time. Without this “cumulative culture”, we wouldn’t have our deep scientific knowledge, rich artistic traditions, or sophisticated technology. Simply put, you can’t make a car from scratch – first, you need to invent the wheel.

Are we alone in this respect? Certainly, many other animals can learn knowledge and skills from each other, and many of them have cultural traditions. But Newton’s metaphor involves not just the spread of knowledge, but its gradual improvement. We build on the past, rather than just passing it along. As generations tick by, our culture becomes more complex. Do other species show the same ‘cultural ratchet’?

Lewis Dean from the University of St Andrews tried to answer that question by presenting human children, chimpanzees and capuchin monkeys with the same task: a puzzle box with three, increasingly difficult stages, each one building on the last.

Read More


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Not Exactly Rocket Science

Dive into the awe-inspiring, beautiful and quirky world of science news with award-winning writer Ed Yong. No previous experience required.

See More

Collapse bottom bar