Tuesday, March 20, 2018

Physicists Determined That Cats Are a Liquid

Marc-Antoine Fardin, a physicist at Paris Diderot University, was inspired by a post at boredpanda.com called “15 Proofs That Cats Are Liquids” and set out to use the tools of his trade to determine if this is, in fact, true.

Figure from "On the Rheology of Cats": (a) A cat appears as a solid material with a
consistent shape rotating and bouncing, like Silly Putty on short time scales.
(b) At longer time scales, a cat flows and fills an empty wine glass.
(c-d) For older cats, we can also introduce a characteristic time of expansion and
distinguish between liquid (c) and gaseous (d) feline states.

Rheology is the branch of physics that studies the flow of matter. Matter can come in three forms: solid, liquid and gas. Under pressure or stress, solid matter deforms whereas liquid and gas matter flows. Liquid matter is incompressible, whereas gas matter is compressible. Thus, liquids are substances that conform to the shape of their containers (i.e. are fluid) and have constant volume (i.e. are incompressible).

Flow is the process of conforming to the shape of containers and has a set duration for different substances. In rheology, this duration is called the relaxation time. The ability to determine if a substance is a liquid depends then on whether you observe it for longer than its relaxation time. Based on the evidence provided in images, Marc-Antoine determined that cats can, in fact, conform to the shapes of their containers if given enough time. Therefore, cats are liquid.

But this leaves us with additional questions about how cats flow. For one thing, some fluids are more viscous (thicker) at some times and less viscous (runnier) at others. This property is called thixotropy. Do cats exhibit thixotropy? In other words, does the relaxation time of a cat depend on its age? And do they flow with vortices or with laminar flow? A substance flowing with vortices would spin around the container and start to climb of the walls of the container. A substance flowing in a laminar way would calmly follow the outline of their container. Cats may be a fluid that can do both.

Figure from "On the Rheology of Cats": (a) A cat spontaneously rotates in a cylindrical jar.
(b) Normal forces and Weissenberg effect in a young sample of Felis catus.

Clearly, more work needs to be done on this very important question. If you have a cat, you can explore this question with some photographic evidence of your own.

Want to know more? Check this out:

Fardin, M.A. (2014). On the Rheology of Cats. Rheology Bulletin, 83(2):16-17.

Tuesday, March 13, 2018

The Science Life 3

The science life is a stressful one, no matter what stage you're at. Take a music break and know you're not alone.

"Take Exams" by AcapellaScience (parody of "Shake it Off" by Taylor Swift):

"Part of Your Lab" by Florence Schechter (parody of "Part of Your World" from The Little Mermaid):

"Some Budding Yeast I Used to Grow" by Nathaniel Krefman (parody of "Somebody That I Used to Know" by Gotye):

Vote for your favorite in the comments section below. If you would like to see more music videos on the life of a scientist, check out The Science Life and The Science Life 2. And if you feel so inspired, make a video of your own, upload it on YouTube and send me a link to include in a future post!

Tuesday, March 6, 2018

Caught in My Web: Marine Technology

Image by Luc Viatour at Wikimedia Commons
For this edition of Caught in My Web, allow yourself to be amazed both by the range and depth of behaviors of marine animals, and by the incredible technologies we have used to learn these things.

1. Penguincams show that Gentoo penguins “talk” to one another while foraging and you can see some of the penguincam footage here.

2. Scientists built an 8-foot touchscreen for the dolphins at the National Aquarum in Baltimore and discovered they like to play “Whack-an-Angelfish”.

3. Using audio-recording tags, we learned that mother and baby humback whales “whisper” to one another to avoid predators.

4. Scientists created virtual reality holodeck for zebrafish.

5. Thanks to the fact that zebrafish larvae are transparent, scientists have discovered a way to image brain activity in an animal as it is behaving in real time. Humans may be cool enough to have developed this technology, but now we know that zebrafish have developed predator eversion strategies when they are still larvae.

What will we come up with next?

Tuesday, February 27, 2018

Risky Business: Ape Style

A repost of an original article from April 3, 2013.

The decisions of this chimpanzee living in the
Tchimpounga Chimpanzee Sanctuary are affected
by his social situation. Photo by Alex Rosati.
If you have a choice between a prize that is awesome half the time and totally lame the other half of the time or a mediocre prize that is a sure-thing, which would you choose? Your choice probably depends on your personality somewhat. It may also depend on your needs and your mood. And it can depend on social contexts, like if you’re competing with someone or if you’re being watched by your boss or someone you have a crush on.

All animals have to make choices. Some choices are obvious: Choose the thing that is known to be of high quality over the thing that is known to be of low quality. But usually, the qualities of some options are uncertain and choosing them can be risky. As with us, the likelihood of some primates, birds, and insects to choose riskier options over safer ones can be affected by outside influences. And we aren’t the only species to have our risk-taking choices influenced by social context.

Anthropologists Alex Rosati and Brian Hare at Duke University tested two ape species, chimpanzees and bonobos, in their willingness to choose the riskier option in different social situations. They tested chimpanzees living in the Tchimpounga Chimpanzee Sanctuary and bonobos in the Lola ya Bonobo Sanctuary, both in the Democratic Republic of Congo. Most of the apes living in these sanctuaries are confiscated from poachers that captured them from the wild for the pet trade and for bushmeat. In these sanctuaries the animals live in social groups, generally spending their days roaming large tracts of tropical forest and their nights in indoor dormitories. This lifestyle rehabilitates their bodies and minds, resulting in psychologically healthy sanctuary inhabitants.

It is in these familiar dormitories that Alex and Brian tested the apes’ propensity for making risky choices. For their experimental set-up, an experimenter sat across a table from an ape and offered them two options: an overturned bowl that always covered a treat that the apes kinda like (peanuts) versus an overturned bowl that covered either an awesome treat (banana or apple) or a lousy treat (cucumber or lettuce). In this paradigm, the peanut-bowl represents the safe choice because whenever the ape chooses it, they know they’re getting peanuts. But the other bowl is the risky choice, because half the time they get fruit (yum!), but the other half of the time they get greens (bummer).

This figure from Rosati and Hare's 2012 Animal Behavour paper shows Alex demonstrating the steps they would go through before the ape chose one of the two options.
After spending some time training the apes to be sure they understood the game, the researchers tested their choices in different social situations. In each test session, the ape was allowed to choose between the two bowls (and eat the reward) multiple times (each choice was called a trial). But before the test session began and in between choice trials, another experimenter sat with the ape for two minutes and did one of three things: In one group, the experimenter sat at the table and silently looked down (they called this the “neutral condition”). In another group, the experimenter repeatedly offered the ape a large piece of food, pulling it away and grunting whenever the ape reached for it (they called this the “competitive condition”). In a third group, the experimenter tickled and played with the ape (they called this the “play condition”).

Alex and Brian found out that whereas bonobos chose the safe option and the risky option about equally, the chimpanzees were significantly more likely to choose the risky option. But despite this species difference, both species chose the risky option more often in the “competitive condition”. Neither species increased their risk-taking in the “play condition”.

The graph on the left shows that wheras bonobos chose the safe option and the risky option each about 50% of the time (where the dashed line is), the chimpanzees chose the risky option much more often. The graph on the right shows that both species chose the risky option more often in the "competition condition" than they did in the "neutral condition". Figure from Rosati and Hare's 2012 Animal Behavour paper.
These are interesting findings, especially when you consider the natural behaviors and lifestyles of these closely related species. Bonobos can be thought of as the hippies of the ape world, happily sharing and using sex to settle disputes and strengthen relationships. In comparison, chimpanzees are more like gangsters, aggressively fighting over resources and dominance ranks. So in general, the more competitive species is more likely to take risks. But when the social environment becomes more competitive, both species up the ante. This effect doesn’t seem to be simply the result of being in a social situation, because the apes didn’t increase their risk-taking in the presence of a playful experimenter.

This still leaves us with some questions to ponder though. Are apes more likely to take risks when an experimenter is offering food and taking it away because of a heightened sense of competition, or is this the result of frustration? And would we see the same effect if the “competitor” were another ape of the same species, rather than a human experimenter? How would their behavior change if they were hungry? These questions are harder to get at, but this research does demonstrate that like in humans, the decision-making process in chimpanzees and bonobos is dependent on social context.

Want to know more? Check this out:

Rosati, A., & Hare, B. (2012). Decision making across social contexts: competition increases preferences for risk in chimpanzees and bonobos Animal Behaviour, 84 (4), 869-879 DOI: 10.1016/j.anbehav.2012.07.010

Wednesday, February 21, 2018

The Love Chemical of 2018

Hello and welcome to the Love Chemical Pageant Results Show! The voting results are in, and today we get to crown the Love Chemical of 2018… Vasopressin! Now let’s get to know Vasopressin a little bit better.

Vasopressin (also known as Antidiuretic Hormone) is a molecule that is widely involved in the balance of water and ions (such as salts) in mammals. (Other taxonomic groups have variations of it as well). But this chemical has gone to our heads, influencing behavior as well.

In the brain, vasopressin acts on a specific receptor type, called vasopressin 1a receptor (V1aR). There are lots of V1aR receptors in brain areas that regulate social and emotional behaviors. When vasopressin binds to many of these receptors, it can result in aggression, territoriality, and fight-or-flight responses. It is also involved in the formation of memories that are necessary to avoid danger. Interestingly, males and females usually have different patterns of where in the brain these V1aR receptors are.

Although we often think of love and aggression as opposites, the life-preserving roles of vasopressin have made it well-suited to become an important chemical of love. In animals, pair bonding (the formation of a strong and unique connection between mates of a socially monogamous species) is often accompanied by an increase in aggression towards non-mates. This aggression can serve to protect the mate and family, but also to reject competitive suitors towards either partner.

Photo of a prairie vole pair from Young, Gobrogge, Liu and Wang paper
in Frontiers in Neuroendocrinology (2011)

Researchers often use several closely-related vole species to study how the brain regulates pair bonding; While prairie voles and pine voles are monogamous, raise their offspring with their partners, and defend their homes and families, montane voles and meadow voles are promiscuous and females raise their young by themselves. Oddly, giving monogamous vole species vasopressin increases their preference for spending time with their mate, their parental behaviors, and their selective aggression against outsiders, but giving promiscuous vole species vasopressin does not. Vasopressin is also more likely to increase these monogamous behaviors in males more than in females. Both males and females respond differently to vasopressin depending on their reproductive status.

It turns out, the pattern of V1aR receptors in the brain is similar between the monogamous prairie and pine voles, but different from the promiscuous montane and meadow voles. Genetic factors drive this difference, and if you alter the gene for the V1aR of a promiscuous species to be more like the prairie vole’s version of the gene, the previously promiscuous species behaves in a monogamous way! The reason promiscuous vole species don’t behave in a monogamous way when given vasopressin is because they don’t naturally have the V1aR receptors in certain brain regions to respond to it that way.

We are still learning about the role of vasopressin in pair bonding behaviors. Much of what we know has focused on these vole species, and we know much less about vasopressin’s involvement in pair bonding in other species. We also don’t know as much about the role of vasopressin in females across different reproductive stages. But one thing is for sure: Love wouldn’t be the same without Vasopressin!

Want to know more? Check these out:
Carter, C.S. (2017). The Oxytocin–vasopressin Pathway in the Context of Love and Fear. Frontiers in Endocrinology, 8(356): 1-12.

Phelps, S.M., Okhovat, M. and Berrio, A. (2017). Individual Differences in Social Behavior and Cortical Vasopressin Receptor: Genetics, Epigenetics, and Evolution. Frontiers in Endocrinology, 8(537): 1-12.

Tickerhoof, M.C. and Smith, A.S. (2017). Vasopressinergic Neurocircuitry Regulating Social Attachment in a Monogamous Species. Frontiers in Endocrinology, 8(265): 1-10.