Trapjaw ants, filmed at 600 frames per second

By Adrian Smith; taken from Myrmecos.

The smell of rain: what is petrichor?

  1. a pleasant smell that frequently accompanies the first rain after a long period of warm, dry weather.
    “other than the petrichor emanating from the rapidly drying grass, there was not a trace of evidence that it had rained at all”

After the goofy first 40 seconds, this video lists two things that make up the ‘smell of rain’: ozone and petrichor.

Petrichor is the decomposing plant matter that rain causes to erupt from the soil. This same substance is – supposedly – a signal to plants that the soil has been dry and will prevent seeds from sprouting.

But when I went looking for more scholarly information on petrichor I found it…practically non-existent. There were no articles that mentioned it in the 2000s. There was one article that mentioned it in the 1990s. There were a few articles that mentioned referred to a specific article from the 70s. In fact, the were only two original research articles that I could find investigating petrichor as a scientific concept, both by the same two authors: IJ Bear and RG Thomas. These are “Petrichor and Plant Growth” and “Genesis of Petrichor“. As far as I can tell, none of the research was followed up on or replicated though the idea has occasionally been taken up in other contexts.

Petrichor clearly exists as a smell, but it turns out that there is precious little knowledge of what it actually is.

[via Ed Yong]

The sound of silence

Sensory neurons receive input from the outside world and send these signals on to the rest of the nervous system. This makes the concept of ‘silence’ fairly intriguing: what happens when there is very little sensory signal for the rest of the brain to process? It is well known that, after a while, no sensory stimulation means massive hallucinations. But quiet – brief periods of weak or no relevant stimulus – is different:

In the mid 20th century, epidemiologists discovered correlations between high blood pressure and chronic noise sources like highways and airports. Later research seemed to link noise to increased rates of sleep loss, heart disease, and tinnitus. (It’s this line of research that hatched the 1960s-era notion of “noise pollution,” a name that implicitly refashions transitory noises as toxic and long-lasting.)

Sound waves vibrate the bones of the ear, which transmit movement to the snail-shaped cochlea. The cochlea converts physical vibrations into electrical signals that the brain receives. The body reacts immediately and powerfully to these signals, even in the middle of deep sleep. Neurophysiological research suggests that noises first activate the amygdalae, clusters of neurons located in the temporal lobes of the brain, associated with memory formation and emotion. The activation prompts an immediate release of stress hormones like cortisol. [neuroecology: really? all noises?]

…He found that the impacts of music could be read directly in the bloodstream, via changes in blood pressure, carbon dioxide, and circulation in the brain. (Bernardi and his son are both amateur musicians, and they wanted to explore a shared interest.) “During almost all sorts of music, there was a physiological change compatible with a condition of arousal,” he explains…But the more striking finding appeared between musical tracks. Bernardi and his colleagues discovered that randomly inserted stretches of silence also had a drastic effect, but in the opposite direction. In fact, two-minute silent pauses proved far more relaxing than either “relaxing” music or a longer silence played before the experiment started.

In light of this, I found the experiences of a hermit who has been living alone since the 1980s fascinating:

He explained about the lack of eye contact. “I’m not used to seeing people’s faces,” he said. “There’s too much information there. Aren’t you aware of it? Too much, too fast.” (Note: he may have asperger’s)

“But you must have thought about things,” I said. “About your life, about the human condition.”

Chris became surprisingly introspective. “I did examine myself,” he said. “Solitude did increase my perception. But here’s the tricky thing—when I applied my increased perception to myself, I lost my identity. With no audience, no one to perform for, I was just there. There was no need to define myself; I became irrelevant. The moon was the minute hand, the seasons the hour hand. I didn’t even have a name. I never felt lonely. To put it romantically: I was completely free.”

…”What I miss most,” he eventually continued, “is somewhere between quiet and solitude. What I miss most is stillness.” He said he’d watched for years as a shelf mushroom grew on the trunk of a Douglas fir in his camp. I’d noticed the mushroom when I visited—it was enormous—and he asked me with evident concern if anyone had knocked it down. I assured him it was still there. In the height of summer, he said, he’d sometimes sneak down to the lake at night. “I’d stretch out in the water, float on my back, and look at the stars.”

Evolution 2014, watch the talks!

I am really behind on this, but there is a spreadsheet with videos of most (?) of the talks from the Evolution 2014 conference.

Here are the talks that are relevant to the interests of the blog:

Flexible decision-making in a variable environment: when do foraging honeybees rob nectar?

Evolution of female song production in Drosophila virilis group species

Continue reading

Can we predict evolution?

Is evolution random, or predictable?

But Gould had a deeper question in mind as he wrote his book. If you knew everything about life on Earth half a billion years ago, could you predict that humans would eventually evolve?

Gould thought not. He even doubted that scientists could safely predict that any vertebrates would still be on the planet today. How could they, he argued, when life is constantly buffeted by random evolutionary gusts? Natural selection depends on unpredictable mutations, and once a species emerges, its fate can be influenced by all sorts of forces, from viral outbreaks to continental drift, volcanic eruptions and asteroid impacts. Our continued existence, Gould wrote, is the result of a thousand happy accidents.

If Gould were right, the pattern of evolution on each island would look nothing like the pattern on the other islands. If evolution were more predictable, however, the lizards would tend to repeat the same patterns…For the most part, though, lizard evolution followed predictable patterns. Each time lizards colonized an island, they evolved into many of the same forms. On each island, some lizards adapted to living high in trees, evolving pads on their feet for gripping surfaces, along with long legs and a stocky body. Other lizards adapted to life among the thin branches lower down on the trees, evolving short legs that help them hug their narrow perches. Still other lizards adapted to living in grass and shrubs, evolving long tails and slender trunks. On island after island, the same kinds of lizards have evolved.

The article also discusses Lenski’s work with the evolution of E. coli. He has a fantastic blog that you should be reading if you care about evolution at all.

A big theme in behavior right now is prediction – how well can we guess what an animal will do based on what it’s done in the past, and what it’s experienced? It turns out on an individual level, you can do a lot better than you’d think.

Naked mole rats, star-nosed moles, and tentacled snakes: the research of Ken Catania

mole rate somatosensory cortex

A classic paper about Naked Mole Rats was passed around on twitter recently and I thought that it would be a good time to revisit some of the greatest hits of Ken Catania, wonder neuroethologist.

There is tons of interesting neuroscience questions that pertain to the strange animals you’ll find in the wild but very few people able to do that research – I suspect because of the lack of funding. But look at the list of animals that Ken Catania studies according to his web page: star-nosed moles, tentacled snakes, water shrews, crocodiles, worm-grunting, and more. Who else will show us videos of moles attempting to smell in stereo? Or of tentacled snakes in action? It’s worth your time to watch this lecture of some of his fascinating neuroethology research:


Chimps stick grass in their ears to be cool: notes on cultural transmission

grass in ear

1. In 2010, a female chimpanzee named Julie began repeatedly stuffing a stiff blade of grass into her ear. This Grass-in-ear behavior has affectionately been dubbed “GIEB” by the scientists who observed it.

2. Out of a group of twelve chimpanzees, eight engaged in GIEB. In three other groups of chimpanzees found in other locations in the same forest, only one was ever seen to GIEB.

3. The more that an individual associated with Julie, the more likely they were to GIEB.

4. After the inventor of GIEB died – if one could be said to invent a thing like putting grass in one’s ear – two chimpanzees continued to engage in the activity. They were never seen to do it together, let alone put grass in the other one’s ear.

5. A young monkey named Imo once noticed that her sweet potatoes were covered in sand and that if she dunked them in the water they would become clean. Within a few years, every monkey on her island was dunking sweet potatoes. She later learned that if she dunked them in the ocean instead, plunging them in after every bite, they would taste even better. The lesson? Monkeys love seasoned potatoes.

Japanese macaque stone handling

6. Some Japanese macaques like to play with stones, clicking and clacking them, rolling them along their hands, cuddling or pushing or throwing them. This was first invented by a young female monkey named Glance in 1979. Her playmates learned it first, followed by theirs. What began as transmission among friends has transformed into transmission among generations: now babies learn it from their mothers.

7. There are at least 11 mutations of this stone handling behavior, including “Rub With Hands”, “Grasp Walk”, and “Flinting”. These variations appear to be transmitted between tribes of monkeys when males migrate from one to another. Additionally, each generation appears to add complexity as each individual inadvertently contributes some new idea.

8. Monkeys are not the only animals with social transmission of ideas; many other animals do, though it may not necessarily be for the best. When young guppies are learning where to eat, they follow an older fellow to a source of food. Slowly, they learn from the older guppy which route to take to their food. As time goes on, one guppy learns from another and a route is set. However, this can be maladaptive when there is a faster route available: follow the group even if they know there is a quicker way.

9. One can digitize animals and ask how their theoretical equivalents toss around cultural traits. What causes these electronic cultures to die out? Simple: small groups, high mortality, poor transmission, and costly traits. Prestigious traits, or traits with group consensus, die out just as quickly as any other. In other words, a culture held in high esteem is just as mortal as any other.

10. The connections between members of a group aren’t uniformly random. Instead, they tend to form small worlds, where any two members are just a few steps away from each other. Thank you, Kevin Bacon. In any random network, as the set of connections reaches half the number of members, a “percolation” process causes many small groups to begin congealing into one large group. Much can be learned about sociality and culture using these ideas.

11. It is possible to classify social learning mechanisms in ten distinct ways: stimulus enhancement, local enhancement, observational conditioning, social enhancement of food preferences, response facilitation, social facilitation, contextual imitation, production imitation, observational response-stimulus learning, and emulation.

12. A computer tournament revealed that even indiscriminate copying is often better than trial and error learning. Copied individuals will often perform the best available behavior, and the better the behavior the more likely they were to survive. Thus, survival itself made behavior a non-random sample of the best behavior. Individuals were themselves highly useful filters of information waiting to be copied.


Huffman, M., Nahallage, C., & Leca, J. (2008). Cultured Monkeys: Social Learning Cast in Stones Current Directions in Psychological Science, 17 (6), 410-414 DOI: 10.1111/j.1467-8721.2008.00616.x

van Leeuwen, E., Cronin, K., & Haun, D. (2014). A group-specific arbitrary tradition in chimpanzees (Pan troglodytes) Animal Cognition DOI: 10.1007/s10071-014-0766-8

Laland, K., & Williams, K. (1998). Social transmission of maladaptive information in the guppy Behavioral Ecology, 9 (5), 493-499 DOI: 10.1093/beheco/9.5.493

Nunn, C., Thrall, P., Bartz, K., Dasgupta, T., & Boesch, C. (2009). Do transmission mechanisms or social systems drive cultural dynamics in socially structured populations? Animal Behaviour, 77 (6), 1515-1524 DOI: 10.1016/j.anbehav.2009.02.023

Stocker R, Green DG, & Newth D (2001). Consensus and cohesion in simulated social networks Journal of Artificial Societies and Social Simulation, 4 (4)

Rendell L, Fogarty L, Hoppitt WJ, Morgan TJ, Webster MM, & Laland KN (2011). Cognitive culture: theoretical and empirical insights into social learning strategies. Trends in cognitive sciences, 15 (2), 68-76 PMID: 21215677

Animals in zoos are often on antipsychotics

Zoos just plain drive animals crazy:

In the mid-1990s, Gus, a polar bear in the Central Park Zoo, alarmed visitors by compulsively swimming figure eights in his pool, sometimes for 12 hours a day. He stalked children from his underwater window, prompting zoo staff to put up barriers to keep the frightened children away from his predatory gaze.* Gus’s neuroticism earned him the nickname “the bipolar bear,” a dose of Prozac, and $25,000 worth of behavioral therapy…

Many animals cope with unstimulating or small environments through stereotypic behavior, which, in zoological parlance, is a repetitive behavior that serves no obvious purpose, such as pacing, bar biting, and Gus’ figure-eight swimming. Trichotillomania (repetitive hair plucking) and regurgitation and reingestation (the practice of repetitively vomiting and eating the vomit) are also common in captivity. According to Temple Grandin and Catherine Johnson, authors of Animals Make Us Human, these behaviors, “almost never occur in the wild.” In captivity, these behaviors are so common that they have a name: “zoochosis,” or psychosis caused by confinement…

Drugs are another common treatment for stereotypic behavior. “At every zoo where I spoke to someone, a psychopharmaceutical had been tried,” Braitman told me. She explained that pharmaceuticals are attractive to zoos because “they are a hell of a lot less expensive than re-doing your $2 million exhibit or getting rid of that problem creature.” But good luck getting some hard numbers on the practice. The AZA and the Smithsonian National Zoo declined to be interviewed for this article, and many zookeepers sign non-disclosure agreements. Braitman also found the industry hushed on this issue, likely because “finding out that the gorillas, badgers, giraffes, belugas, or wallabies on the other side of the glass are taking Valium, Prozac, or antipsychotics to deal with their lives as display animals is not exactly heartwarming news.” We do know, however, that the animal pharmaceutical industry is booming. In 2010, it did almost $6 billion in sales in the United States.

It is like a bored person locked in a room, pacing around the room while waiting to get out.. If you want to see this kind of repetitive behavior in action, here are some short movies illustrating them. Repetitive behaviors are also often seen in people with developmental disabilities, especially autism, where external stimulation is hypothesized to be a motivating reason. Here is a review of some of the neural mechanisms of stereotypy.


Is it okay to eat fish if they don’t have any feelings? (Updated)


When a scientific paper begins its list of keywords with “fish cognition”, you know you’re in for a good read.

Culum Brown is tired of people eating fish, and he’s not going to take it anymore. Fish, he says, are smarter than you think. We need to cast off our view of them as dumb slimy creatures and recognize what they can really accomplish.

First, we have to realize that though they may have separated from us evolutionarily more than half a billion years ago, they are not ‘primitive’; it is not as if they stopped evolving. If a fish had stopped evolving could it do this:


That’s right – this bad boy, the cutlips minnow, gathers stones to build a mound to attract mates. And these aren’t the only ‘fishy masons’ (as Brown calls them). The jawfish builds itself a wall in front of its burrow, searching for rocks that fit together like lock and key, leaving only a hole just big enough for them to scurry through.  The Rockmover Wrasse builds itself a stone house every night. It also hunts in pairs, one member pushing rocks around so that the other can watch carefully in order to grab any prey that is revealed.

Fish also have sophisticated social intelligence. Take, for instance, the Cleaner Wrasse. They occupy stations – which I’ll generously call a storefront – where other client fish come by to have parasites and dead skin removed by the Cleaner. Brown points out that the fish have the option of several cleaners, so it is important to have a good reputation; should a Cleaner accidentally bite a client, they’ll chase after their fleeing clients and give them a good back rub to make up for it. They also prioritize certain customers over others. Model that, economists.

cleaner wrasse

Many other fish can recognize multiple individuals, and can count the number of fish in a group at a glance.

Some fish also use tools: a number of species use rocks to break open shellfish, or glue their eggs to leaves that they can them drag around as they go about their errands.

I actually came away impressed from this paper; I hadn’t known most of these fishy facts. Yet despite how smart fish are, people will still eat them; after all, they’re pretty okay eating piggies (they’re pretty smart). What matters more than any kind of intellectual empathy is a anthropomorphic one. After all, which would be more okay to eat: a really dumb monkey or a really smart (but ugly) fish?

(My biggest take-away from this is not to eat a Wrasse; those guys are pretty smart, and have a much larger brain for their size than you’d expect.)

via Marginal Revolution

Update: Ed Yong happened write an article today on this very subject! Lionfish are strategic, social hunters:

During night dives, Lönnstedt often saw teams of two to four lionfish positioning themselves around schools of smaller fish and using their fan-like pectoral fins to corral their prey “like fishermen with their nets”. The hunters then take turns to dart into the school of prey, picking them off one at a time…

“Fish social behaviour is much more complex than previously assumed. Moving away from a stimulus of major interest—prey—in order to actively recruit a partner that is initially out of sight suggests planning and awareness of objects that [they can’t see].”…But in these pursuits, the two partners are merely hunting next to each other and relying on their complementary abilities. The lionfish are doing something more impressive: they’re working together to corral their prey and taking turns to go in for the kill.


Brown C (2014). Fish intelligence, sentience and ethics. Animal cognition PMID: 24942105

Humans are animals. But humans aren’t animals.

One day, a few anthropomorphized liquid water molecules got together for some coffee and started debating the Exceptionality Hypothesis: that liquid water was fundamentally different from other types of water.

“This is ridiculous,” one exclaimed. “Scientists have shown that water vapor and water ice are made of the same atoms that we are, structured in the same way, and follow the same physical rules that we do. Sure, we stay on the ground but so does water ice! And water vapor may be in the air but it moves around freely – just like us! There’s nothing special about being a liquid water molecule.”

A second rolled their (fictional) eyes. “I can’t believe we’re talking about this. I don’t feel like a gas or a solid. I suppose I agree that we share some things in common with those other two – but we’re fundamentally different!”

The first snorted. “Sure. How?”

Obviously, liquids, gases, and solids behave differently; despite being made of the same molecules following the same rules, if you vary the temperature you get fundamental changes in behavior due to phase transitions. Even if things are made up of the same constituent parts that vary in proportion, you can get fundamentally different behaviors.

OK, so this is a silly little parable. But there’s an article going around the tweetersphere by Annalee Newitz titled “Yes, Humans Are Animals — So Just Get Over Yourselves, Homo sapiens“. I’m sure you get the point:

Yet we have many other behaviors that we share with our fellow animals. Darwin wrote about this in one of his lesser-known works, The Expression of the Emotions in Man and Animals. Today, hundreds of scientific studies have offered solid evidence that animals from chimps to rats share the same kinds of emotions and motivations that we do.

Many animals also make tools the way humans do too. We’ve long known about tool-making among other primates, but recently scientists have found evidence of tool-use among dolphins, crows, and even sea otters.

Humans may not use tools and express emotions exactly like other animals, but that doesn’t exempt us from animal status. No two species share exactly the same sets of behavior. But we also share far too much in common to pretend that we are some form of life that transcends animal status.

Humans are animals, clearly. We are mammals with an evolutionary lineage that can be traced back just like any other animal on Earth. But there’s a double-use of the word going on: animals as biological entities and animals as moral entities.

It seems what may – may – separate us from other animals is along a moral and cognitive axis. We certainly do have neural structures for decision-making and learning about value that are the same as rats and monkeys, but so do bees and other insects. Yet if you were to tell me that insects are able to master the same cognitive tasks as most mammals I’d wonder about you. You see this implicitly in how we treat other classes of animals: insects are not fish are not mammals. We are fundamentally different.

So we should think about what makes us distinct from other animals. Let’s take a few of the examples in the article. Ants build massive cities, milk (and raise!) aphids for food, and tend fungus gardens. But besides us, ants are unique in this; and as far as I’m aware, these were most likely done on a longer evolutionary timescale and was not done consciously. Yes other animals use tools, but prodding something with a stick is a little different from a using jackhammer or even a mass-produced screwdriver (let alone building and designing these tools to begin with). Other animals may share the same kind of motivations and decision-making, but I have yet to see another animal read a mass-produced text on the other side of a planet in order to guide their decisions. More, there is no other animal that has consciously launched itself into space with dreams of living there.

Even if the biological and neurological components required to, say, design and build a computer are present in bits and pieces of other animals, it is their confluence that is found in us. Perhaps every animal is different in its own way, but let’s be clear: as a species, we can do things that other animals could never even dream of. We have the ability to liberate ourselves from our biology and change our environment in conscious ways that all other animals cannot. We may be animals, but we’re not animals.