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Category Archives: zoology

Nest-making orangutans build for comfort and strength

Great apes are our closest relatives, and they are constantly surprising us with their human-like abilities and tendencies; here at Ars, we've seen studies showing that they plan ahead, they engage in wars over territory, and they respond to being tickled, just to name a few. Now, a new study in PNAS adds to the growing list of ways in which great apes are similar to us: they value a good night’s sleep, and they have the technological know-how to build pretty impressive beds from some very basic materials.

Many species of great ape, including chimpanzees, gorillas, bonobos, and orangutans, build nests in the forest canopy. Generally, these nests are slept in for just one night, then abandoned. The nests are thought to benefit the apes in several ways: sleeping above the ground reduces disturbances, protects them from predators, leaves them less vulnerable to mosquitoes and other pests, and generally increases the quality of their sleep. However, we know very little about how these nests are actually constructed. To figure out how much skill goes into nest-building, a group of scientists studied nests made by Sumatran orangutans in Indonesia.

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Bowerbirds woo mates with a lot of effort and a little illusion

Inherently, there’s a problem with the way we view the world: our world is three dimensional, while the image projected onto our retinas is just two dimensional. Therefore, without even being aware of it, we use clues to figure out distance and perspective in our environment. When an object gets smaller, it is becoming farther away; when it gets larger, it is approaching us.

New research in Science this week shows that we aren’t the only species that uses visual clues as a means to an end: male bowerbirds’ mating success depends on their ability to create a false sense of perspective.

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Bees reach consensus by headbutting dissenters

The human brain is wonderfully complex. Within it, there are billions of neurons, each collecting information and determining whether to respond to it. In some cases, groups of neurons compete for an outcome; when a group reaches a certain level of activity, its output ends up being chosen. To help make their case, these neurons can send positive signals to each other, and they can inhibit others with different agendas. Ideally, this system improves the chances of reaching an optimal decision; it’s an elegant way to make sense of lots of competing input.

As if we didn't think bees were cool enough already, Science reports this week that this approach to decision making is echoed in the behavior of honeybee swarms. Just as our neurons emit inhibitory signals, bees can hinder other hivemates that are advocating a different course of action. As with neurons, the swarm’s collective decision is made when a particular threshold is reached. But, unlike neurons, the bees have a very physical means of inhibiting those with a competing message: they headbutt them.

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Wasps with many queens will remember your face as they sting you

For most of us humans (and other species), the ability to recognize faces comes so naturally that we don’t even think about it. However, many other animals lack the ability to distinguish between individual faces, even when they are faces of their own species. Even closely related species within a single genus sometimes display variability in this type of individual recognition. So what determines whether an animal can learn to identify the faces of its conspecifics?

New research in Science suggests that face learning may be shaped by the specific ecology of individual species. To study this, researchers used Polistes fuscatus, a species of paper wasp, that is excellent at facial recognition. P. fuscatus has all the ingredients necessary for this cognitive ability: they have excellent vision, their nests are well-lit, their facial features are highly variable, and (perhaps most importantly) they have multiple queens. 

This life history detail may be the key to their facial recognition skills. Since there is more than one queen in each nest, having a hierarchy becomes important; wasps must learn who is who in order to avoid conflict and keep the colony stable.

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