Birds communicate with their eggs, shape-shifting proteins create memory, and dolphins have polite conversations. 2016 was a terrible year by many counts, but at least scientific research forged ahead. Below I have compiled a subjective list of the ten coolest findings in animal cognition in 2016. Happy New Year's Eve!
1. Birds sing to their eggs to tell future hatchlings about the weather. When it is hot out, Australian zebra finch parents sing an unusual song to their eggs to prepare their babies. Amazingly, birds incubated in hot temperatures grew more slowly if they were exposed to such calls. Further, those hatchlings grow up to have different thermal preferences and reproductive success than peers who did not get acoustic signals while in the egg. Study coauthor Mylene Mariette remarked that these birds “actually have a mechanism to prepare their offspring for high temperatures." This truly astounding finding demonstrates that birds are better at talking about climate change with their kids than we are.
2. Older monkeys have fewer friends, just like us. As we humans get older, we tend to focus our social efforts on fewer people. We hang out with close friends and family, instead of trying to forge new emotional bonds and maintain many acquaintances. Laura Almeling and her collaborators found that Barbary macaques are just like us in this regard: "elderly" monkeys only groomed about half as many partners as younger monkeys. In humans, scientists thought that we focus on fewer (more emotionally important) social contacts as we age because we are aware of our impending death. Now that we have seen the same result in monkeys, we must make one of two conclusions: (i) some other factor, not awareness of mortality, drives our decreased social interest, or (ii) monkeys, too, are aware of their own mortality. Several interviewed scientists choose (i), proposing that risk aversion, lower energy, or some other age-related effect drives social changes.
3. Ants mark their young rivals for assassination. Ants farm, go to war, create slaves, set aside "toilets", use tools, and unconcernedly adopt a number of other supposedly "human" traits. Now, researchers have observed several creepy, Machiavellian planned executions: adult male ants of the genus Cardiocondyla dispatch their potential rivals when they are very young by painting a bulls-eye on their backs. This lethal "kick me" sign is a cocktail of chemicals that instructs worker ants to kill the marked individual. Jürgen Heinze and his colleagues observed four such cases. In three, the older ant successfully dispatched the younger (via worker ant assassins), but in a fourth case, the young ant avoided assassination and was able to kill his older rival using the same "kiss of death" strategy. Scientists have long observed ants in this genus killing off their potential rivals, but this type of strategic, chemical warfare is novel.
4. Manta Rays goof off in front of a mirror, a sign of self-awareness. Researchers have long used the "mirror test" to search for self-awareness in animals. As the reasoning goes, if an animal acts like it recognizes itself in a mirror (instead of treating the mirror image like an intruder, or a friend), it must have some concept of "self." In the most rigorous version of this test, researchers place invisible or visible marks out of sight on animals, then give them a mirror. If the animals touch and explore the visible mark on their own body, having seen it in the mirror, they clearly understand what they are looking at. In addition to this test, researchers note that some animals start goofing off in front of the mirror-- dolphins blow bubbles and do waggle dances, elephants open their mouths wide and peer inside, and chimps check out their own butts. (To see videos of animals passing this test, click on these links: magpies,dolphins, great apes, and elephants.) When the manta rays were given a mirror, they started swimming in big circles, wiggling their fins, and blowing bubbles (video here). They behaved just like great apes and young children! If this was not a fluke (!), then this research shows that manta rays, a species of fish, have some concept of "self."
5. Killer whale culture drives genetic change. For the first time, researchers have documented the coevolution of genes and culture in a non-human species: the orca. In humans, we know of several cases where culture has driven evolution-- that is, where socially-transmitted behaviors impact genetic evolution. For example, lactose tolerance arose after humans started farming cows for dairy. In orcas, Andrew Foote and colleagues found that orca genomes differentiated along with their cultural hunting strategies. There are many hunting types, such as the Stranding Orcas of Patagonia (who launch their bodies onto land to kill elephant seal pups) and the Wave Generators (who wash prey into the water by coordinating swim-surges towards an ice floe), and these culturally transmitted behaviors have driven genetic divergence. Orcas, and humans are, so far, the only species where we have documented gene-culture coevolution. Who will be next?
6. Dolphins don't interrupt each other when conversing. For a long time, researchers have been trying to understand dolphin communication. For example, a recent study found that dolphins chatter to each other more when they are working together on a tricky task-- suggesting that they are communicating information about the task to each other. Most recently, Vyacheslav Ryabov and colleagues analyzed the chattering of two black sea dolphins using mathematical tools. They found that each dolphin would speak a "sentence" composed of individual pulses, or words, while the other listened before responding. Ryabov said: “Essentially, this exchange resembles a conversation between two people." The variety of "words" present in dolphin communication, and its consistency or inconsistency across contexts, suggests that they are indeed conveying real information and having conversations, just like us. Except unlike people, dolphins don't interrupt each other.
7. A shape-shifting protein is critical for fruit fly memory. The basis of memory is a long-standing mystery, but research research suggests that prions play a critical role. Prions are a type of protein most famous for the diseases they cause, such as the infamous Mad Cow disease. Prions are unusual because they have two possible shapes-- a standard shape, and an alternate configuration that forms chains (and triggers the same shape-shifting in other nearby prions, too). Prions are not exactly alive, because they don't reproduce. But since they can trigger nearby proteins to "misfold," they are often cited as a "grey area" between alive and not-alive. In any case, recent research has uncovered a surprising role for prions: they are required for long-term memory in fruit-flies. Liying Li and colleagues found that a prion called Orb2 allows fruit flies to form, maintain, and express long-term memory. The amount of Orb2 correlates with memory strength, and new molecular tools allowed these researchers to actually visualize memory at the molecular level. Nobel laureate Eric Kandel once asked "do you think God created prions just to kill?" Kandel's work, in combination with this recent paper, seem to suggest that prions are the molecular basis for-- as Liying Li and colleagues wrote with a welcome and poetic turn of phrase-- the "perduring yet malleable nature of memory."
8. 400-year old shark is the oldest vertebrate. Julius Nielsen and colleagues used radiocarbon dating in the Greenland shark's eye-lense to discover that this titan lives to be at least 400 years old. Their method was particularly clever: when humans tested nuclear bombs in the 1950s, we released a pulse of carbon-14 which became incorporated into the sharks' eye-lenses. Just as a forest fire leaves a distinctive mark on tree rings, allowing us to date the tree, this pulse of carbon-14 helped Nielsen discover the age of these sharks. These sharks are gigantic, comparable in size to the great white, and they do not reach sexual maturity until age 150. They have incredibly slow metabolisms and a low swimming speed of about 1 foot per second (less than one mile per hour!), perhaps earning their scientific family the name "sleeper sharks." What is it like to be a silent behemoth swimming sleepily in arctic seas for centuries? Empires have risen and fallen in their wake. What will the world look like in 150 years, when today's newborn Greenland shark finally becomes a "teenager?"
9. Bats pretty much constantly argue. Yosef Prat and colleagues used a machine learning algorithm to decode the cacophony of squeaks coming from bat huddles. When bats are huddled together in a roost, they squeak continuously. By analyzing 15,000 calls that were directed from one individual to another, these researchers concluded that bat squeaks "carry ample information about the identity of the emitter, the context of the call, the behavioral response to the call, and even the call’s addressee". Further, they found that calls fell into four categories (each one argumentative): arguing about food, disputing positions within the huddle, males making unwanted mating advances, and getting annoyed about another bat sitting too close. The researchers point out that as we try to decode animal communications, we should probably pay more attention to "everyday chit-chat" like what was studied here.
10. Chimps who travel are more likely to use tools. A group of researchers led by Thibaud Gruber followed a group of 70 chimps for several years, pairing behavioural observations with experiments to investigate what leads to tool use. When they gave these chimps an opportunity to use tools to extract honey from logs, only 10 chimps figured out how to use tools to do so. Gruber and his colleagues examined their activities leading up to the experiment to look for correlations, and they found that chimps who travelled more and who ate fewer ripe fruits were more likely to use tools to get the honey. This is likely because chimps who were well-fed, and who did not have to travel as much, were less motivated by the honey. Studies like this one help us understand how tool use originates; which individuals are more likely to innovate? It seems that at least in this case, it is not the comfortable alpha male. Sometimes necessity is the mother of invention*.
Thanks to Stacey Chen and Elliott Bannan for sending along some of these findings!
*Of course, compare this to tool use in crows-- both known instances arose in island species who were presumably isolated from predators and given ample time to explore and fool around and develop technology (see research on New Caledonian and Hawaiian Crows).
Photo: Mark MacEwen/Naturepl.com ; Link