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Feline Avian Vocal Mimicry (or chattering cats)

4/28/2016

In the cute (and somewhat hilarious) video below some may recognize the chattering sound these cats are making, having spotted a bird through a window. There are several hypotheses regarding the purpose of this behavior.

One common idea is that cats are attempting to lure birds closer or capture their attention in the interest of predation by mimicking their vocalizations. In such a case, this behavior would amount to more than chatter, as chatter implies nonsensical sounds.

The trifecta of cats in the preceding video appear intently focused on this task, and the cat in the center at times appears fatigued. Whether this is a result of intense concentration, a different reason, or not even tiredness at all remains in the realm of speculation and fancy.

Another hypothesis purports that these vocalizations are a result of either excitement at seeing potential prey, or frustration at not being able to acquire said prey via a vocal displacement of this frustration.

Another example of cat chattering, this time a solo individual:

Observations of wildcats in the Brazilian Amazonian jungle by field biologists do, however, lend some credence to the hypothesis of genuine mimicry. In 2005 researchers from the Wildlife Conservation Society (WCS) observed Margay wildcats emitting calls to pied tamarin monkeys.

These calls not only sounded identical to typical tamarin calls, but elicited observable recognition and confusion in the monkeys. Fabio Rohe, one of the researchers involved in wildlife conservation in the Brazilian Amazonian jungle, believes domestic felines have this copycat ability as well.

Excerpts from the 2005 WCS Margay project

The Margay wildcat is a small species native to Central and South America. Margays are known to mimic almost exactly the calls of pied tamarin monkeys

So the next time you see a domestic cat (felis catus) engaged in this behavior, there's a good likelihood that what you're witnessing is not a random activity or individual cat histrionics. Rather, it could well be a cunning predation tactic informed by several million years of felid evolution!

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Xerxes I: 300 Lashes for the Sea

4/26/2016

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When suitably enraged, the Achaemenid Persian king Xerxes I didn't limit the administration of corporal punishment to animate objects. During the second Persian invasion of Greece in 480 BC the pontoon bridges his army engineers had laid across the Dardanelles straight were destroyed by a storm. In frustration Xerxes I famously "retaliated" by having soldiers flog the very waters of the straight itself with 300 lashes!

Soldiers from Xerxes I's vast army "punish" the waters of the Dardanelles straight itself by flogging with 300 lashes

Xerxes I was the son of Darius I and reigned as King of Persia spanning 486–465 BCE during the Achaemenid dynasty. The Achaemenid Empire is probably best known as the Persian dynasty that was founded by Cyrus the Great.

Relief in rock, Xerxes I. Naqsh-e-Rustam, Iran, near Persepolis

The video snippet below is from the 2006 film 300, which is based on one of the major battles of the second Persian invasion of Greece, the Battle of Thermopylae, which took place in 480 BC. In this scene the Spartan king and military commander Leonidas meets Xerxes I. It goes without saying that the accuracy of cinematic reenactments of historical events should be taken with a grain of salt :

Xerxes I's military incursion into the Greek mainland was a continuation of his father Darius I's first Greek invasion, spanning 492 to 490 BC. During that campaign in 490 BC, in a particular military engagement known as the Battle of Marathon, the Persian army was defeated. Darius died while preparing for a second invasion, thus leaving the leadership of the campaign to his son Xerxes I.

The army fielded by Xerxes I, according to recent historical accounts, numbered over 60,000 combatants. According to other accounts this number was much higher. This was a very diverse force, consisting of Thracians, Jews, Babylonians, Egyptians, Greeks, Macedonians, and even 20,000 Arab camelry and Libyan charioteers!

Between 480–479 BC a number of Greek cities were laid siege to and many razed by this massive force. The Greek standing infantry and naval forces eventually provided such formidable resistance that Xerxes I retreated back to Persia with the remnants of his army. Thus this second invasion was ultimately considered unsuccessful, as the Persian forces retreated without leaving a garrison in the Greek mainland.

Major battles and routes of the second Persian invasion of Greece, 480-479 BC

Cuneiform tablet found near Van , in eastern Turkey. The message is purportedly from Xerxes I paying homage to the Zoroastrian deity Ahura Mazda. The languages inscribed are a combination of old Persian, Babylonian and Elamite

By Nicholas Moreau - By Rei-artur pt en Rei-artur blog , CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=838446

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Kava Kava

4/24/2016

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Kava Kava is a perennial shrub with heart shaped leaves whose roots are used as an intoxicant and soporific in many parts of Oceana and other Island regions of the Pacific. The resultant drink, also referred to as Kava Kava, or just Kava, has sedative, anxiolytic, and muscle relaxant properties. Many describe the intoxication from Kava Kava as a combination of body/muscle relaxation and a psychoactive effect that can be described as a relaxed state of reverie absent significant cognitive impairment.

The heart shaped leaves of the Kava Kava shrub

Comparisons of the psychoactive effect of Kava to alcohol intoxication fall short for a couple of reasons. The subjective effects from Kava are more pacifying and introspective than ethanol. It's well known that people intoxicated by alcohol can become hostile, or even violent due to lowered inhibitions. This is unheard of with Kava. In fact, as more Kava is consumed over time, any possible feeling of hostility or anger that may have been present before consumption will disappear almost entirely.

The botanical name of the Kava Kava shrub is piper methysticum, piper = Latin "pepper", and methysticum = Latinized Greek for "intoxicating." Thus Kava Kava belongs to the genus of plants that include the common black pepper plant, piper nigrum.

The common black pepper plant, piper nigrum. Note the relative similarity between the Kava and pepper plant leaves, although the Kava Kava leaves are more heart shaped

In areas of the Pacific the drinking of Kava Kava is a highly ritualized and social affair. Story telling is common, as some of the initial effects of Kava intoxication include an increase in loquaciousness. In some Islands of the South Pacific, such as Fiji, many ceremonies or functions, both private and public, cannot be properly consummated without the ritualized drinking of Kava Kava.

Over a period of hours, depending upon how much is consumed, this initial loquaciousness transforms into a more somnolent state, sometimes resulting in an almost irresistible urge to sleep. The sleep is known to be deep and rejuvenating, often replete with very vidid dream imagery.

Kava Kava ceremonies, clockwise from upper left: Hawaii, Vanuatu, Fiji, and Tonga.

The psychoactive constituents of Kava Kava are a family of phytochemicals known collectively as kavalactones. Although there are many kavalactones in Kava, there are six principal kavalactones that are thought to be behind most of the effects. Unlike many other psychoactive compounds, kavalactones are not alkaloids, that is, the kavalactone molecules don't contain a nitrogen atom. Rather, they are classified as lactones.

Desmethoxyyangonin (in the image below) is thought to boost dopamine levels in the brain, resulting in the more euphoric effects. It's also a muscle relaxant. Kava also has local anesthetic effects, thought to be a result of Kavain. Dihydrokavain is thought to be responsible for the anti anxiety, or anxiolytic effects.

The six major kavalactones responsible for the psychoactive effects of Kava Kava

There are many different chemotypes of Kava Kava. The relative proportions of kavalactones in different rootstock from different geographical areas can result in perceptibly different effect profiles. Thus, certain Kavas can result in deep muscle relaxation without overmuch euphoric effects, and others, primarily those with a higher Kavain content, can result in a more euphoric, initially stimulating effect.

A ceremonial Kava Kava serving vessel from Fiji

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Ketchup and Thixotropy

4/21/2016

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It's happened to most of us at one time or another: a desperate struggle to dispense ketchup or some other viscous condiment from a bottle comes up short, or worst yet, results in a huge mess.

George Costanza struggles with time-dependent viscosity

The culprit behind this struggle is a rheological phenomenon called thixotropy. First, a word about rheology; rheology is a sub discipline of mechanics, specifically the study of the properties of materials which determine their response to mechanical force, as well as the deformation and flow of matter.

The word rheology is derived from the Greek rheos, meaning "flowing stream, or current." Rheology straddles both main branches of mechanics: solid mechanics and fluid mechanics.

The term thixotropy, like many of it's fellows in scientific nomenclature, derives from Greek as well: thixis "touching" and trope "turning." In a nutshell, thixotropy is a property of certain materials wherein they behave as fluids when agitated but are semi-solid or solid when undisturbed.

In more technical terms, fluids with a high viscosity, or resistance to flow, are thixotropic if they exhibit time-dependent shear thinning. That is, when subject to shear stress over a period of time (for example the agonizing few seconds of vigorous ketchup bottle shaking) these materials will become less viscous. Then, when undisturbed, they will return to the equilibrium of their original viscous state within a fixed amount of time.

Common items that are thixotropic include yogurt, printer ink toner, whipped cream, and many cosmetic gels and colloidal creams.

There are even some fluids that are anti-thixotropic, wherein shear stress applied over time results in an increase in viscosity, or even solidification. This property is referred to as rheopecty.

Some very clever folks at MIT have apparently devised a solution to this rather annoying mechanical property called LiquiGlide, a substance that could be applied to the inside of containers such as ketchup bottles that would make the contents easily pourable:

MIT engineering solution to stuck ketchup bottles

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Masters of Camouflage

4/18/2016

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I know this is my second consecutive post featuring a zoological biology topic, and I really do prefer to mix up my topics more. However, I simply couldn't resist, as the cuttlefish is simply too amazing a species and thus cannot be denied. The cuttlefish is a cephalopod that bears a resemblence to, and is sometimes mistaken for it's relative the squid. However, cuttlefish and squid are quite different, both taxonomically and morphologically.

Images of the cuttlefish. Note the striking color variation. Cuttlefish are able to change color rapidly due to an extremely intricate network of specialized cells called chromatophores (and others) that contain sacs of pigment activated by muscle contractions.

As I alluded to above, cuttlefish are cephalopods, a contraction from greek meaning "head-foot." To me this nomenclature is counter intuitive, as there are 8 arms and 2 tentacles projecting from their heads. Nowhere is the term "foot" used in the anatomical description.

The cephalopods are part of the class of invertebrates that include octopuses, squids, and nautiluses, all grouped under the phylum of mollusk. The speciation of cuttlefish and other cephalopods is quite complex, as can be seen in this Encyclopedia of Life link. The common cuttlefish is known as sepia officinalis.

Squid eye Cuttlefish eye (note the "W" shape)

There are any number of excellent articles on the differences between the cuttlefish and other cephalopods/molluscs. I would like to jump straight into the topic of the post title, that is, camouflage. Cuttlefish exhibit a capacity to blend into their background by changing color within a half second. In addition to changing color, they can also modify the texture of their skin. for example, spiky-like protuberances in the photo below:

A cuttlefish displaying skin protuberances that help it blend into it's surrounding rocky background

The biological mechanism behind this intricate and fast acting camouflage capability includes a network of more than 20 million specialized cells called chromatophores that contain sacs of pigment. As in Figure 1 below, the chromatophore cells are attached to muscle fibers that connect to the cell body radially and are innervated with nerve axons.

The colors of the chromatophore pigmentation are yellow, red, and brown. There are other cells involved in cuttlefish coloration, but the chromatophores are the most kinetic of the set owing to their nexus with the neuromuscular system.

Figure 1: Chromatophore

In the illustration in Figure 2 below, we see on the left a chromatophore cell at rest. On the right we see the cell activated via expansion of the radial muscle fibers. Note how the yellow pigment sac in this instance is stretched out by the strands of muscle, increasing it's surface area sufficiently to render the color visible.

A chromatophore cell at rest Figure 2 An activated chromatophore

As might be expected in nature, this mechanism is more complicated in practice and relies upon other supporting pigmentation cells. Firstly, there are several layers of chromatophore sheets, and below these are oval shaped iridescent cells called iridophores that reflect the colors blue, green, red, and pink. All this structure, finally, undergirded by a network of yet more cells rendering white coloration called leucophores!

This color palette ensures that the cuttlefish can produce virtually any color in the color spectrum. When you're an extant species belonging to a biological class that originated in the Ordovician era, between 485 and 444 million years ago, there's been much time for evolution to solve certain adaptation problems.

Relative positions of chromatophores, iridophores, and leucophores

Although the issue is not definitively settled, the current consensus among marine biologists appears to be that cuttlefish process their background environment visually, via their "W" shaped eyes.

That visual sensory input subsequently undergoes highly sophisticated neural processing, sending commands to the radial muscle fibers attached to the chromatophore cell bodies. Specifically, on how to expand in the correct sequence and combinations in order to produce the desired skin color and body shape. The fact that this process is coordinated at so many levels of organization so quickly staggers the imagination.

Obviously the ability to innervate over 20 million cells in order to produce complex colors and shapes, informed by background color/textures cues no less, requires gargantuan neural processing power. It turns out that cuttlefish, along with other cephalopods, have large brains and a high encephalization quotient. This metric is thought to be a predictor of sorts of the intelligence of an animal.

The PBS NOVA video embedded below from 2007 offers a fascinating glimpse into the behavior and biology of this magnificent animal, and is well worth the time.

If you don't have sufficient time to view the entire video, make sure to see the section on how chromatophores produce color, around 9:30 into this video:

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Random factoid

Feline Avian Vocal Mimicry (or chattering cats)

Xerxes I: 300 Lashes for the Sea

Kava Kava

Ketchup and Thixotropy

Masters of Camouflage

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Feline Avian Vocal Mimicry (or chattering cats)

Xerxes I: 300 Lashes for the Sea

Kava Kava

Ketchup and Thixotropy

Masters of Camouflage

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