Category Archives: Neuroscience/Behavior

Don Cowlione: How Cowbirds Run A Songbird Mafia

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If I were to imprint on you one main point stringing together every article I’ve ever written for Badass Biology, I hope it would be this: nature has produced no shortage of jerks. I say “jerk” like it’s a bad thing, but take the time to think about the word and you’ll realize “jerk” becomes a bit endearing when we’re talking about nature.

First, let’s review what it means to be called a “jerk” species. First, a jerk has to be abundant enough to merit some sort of attention or recognition, but not more abundant than non-jerks, otherwise the jerk strategy would be much less effective. This population size balance is very delicate, but jerks seem to manage it well.  Second, being a jerk means going against some established natural norm. Usually, jerks exploit some mutually beneficial arrangement between individuals, leaving another party to carry their weight for them. It’s a pretty clever strategy if I say so myself. Third, present a jerk with an opportunity and it’s likely to get snagged. Another admirable trait in favor of biological jerks

Back to the point, Planet Earth has lots of jerks. Consider the bluestreak cleaner wrasse. On Southeast Asian reefs, cleaner wrasse set up cleaning stations where they pick off the tiny parasites that live in the skin of larger fish. This arrangement seems to work for everyone (except the parasites, unfortunately); the wrasse get dinner while the larger fish get a good skin treatment. Some jerk wrasses, let’s call them “wrasseholes”, like to instead bite big chunks out of the mucus membranes on these fish instead, turning this mutualistic interaction into a parasitic one.

To be honest, it’s not that I find this interaction all that neat. The main reason I bring this up is to mention that it DID spawn an article in Discover Magazine with a really clever name: Cheater Cheater Mucus Eater.

Sure, jerks are great and all. My favorite? This little guy:

Awwwwww. SO PRETTYYYYYYY.

Adorable, right? What about now?

The Birdfather

Why yes, I AM proud of this joke.

Make no mistake. This stone cold killa is ruthless, even enough so that I’d put the word “killa” in an article that I’m reasonably sure a future employer will read.

So what about this little bird makes it so much of a wrassehole? To start, an introduction. This is the brown-headed cowbird, a member of the family Icteridae, which consequently means nothing at all to me but sounds pretty badass all the same. What distinguishes cowbirds is that they are notorious brood parasites. They find nests belonging to other aviary families, mostly songbirds but varying from hummingbirds to birds of prey, lay their eggs next to theirs, and let those other poor bird parents feed, raise, protect, bathe, clothe, and attend PTA meetings of cowbird babies. As of 1999, approximately 140 species of birds have been documented raising cowbird young.

Here’s what’s odd about this. I’m sure you’ve guessed that cowbirds are able to get away with this sneaky business because their eggs and young look an awful lot like the birds they’re parasitizing. They don’t. More often than not, cowbird eggs are either much larger than the eggs of their host AND a different color and pattern. Moreover, cowbird chicks are gigantic when they hatch, making little songbird chicks look tiny by comparison.

One of these eggs is a parasitic cowbird’s. Can you guess which one? Did you guess the one on the bottom left? You did!? Very good!

You may be asking yourself, “why do these other birds raise babies that aren’t their own?” Right now, I’m asking myself, “have I smelled like this all day?”, but that’s really of no consequence to anyone (except my wife, I guess).

Oddly, one theory explaining why the hosts hadn’t murdered these little guys is, and I’m serious, that the host birds don’t have the cognitive ability to recognize that these chicks are different from the others. It seems odd to me that the same birds can relocate their nests among thousands of other similar-looking forest objects with near-identical colors and patterns would not be able to recognize that one of their babies is a freakish monster.

Meanwhile, I only learned today that I live 5 minutes from a major interstate highway, but I’m confident that there’s no gigantic monster baby living in my house. One of our cats is pretty large, sure, but I’m not convinced I’m her father or anything.

No, the real reason host don’t viciously murder cowbird young is pretty sinister. In 2007, two researchers from the University of Florida set up a field experiment where they manipulated cowbird presence in predator-free nests of host birds. In “ejector” nests, the researchers removed cowbird eggs from host nests, mimicking a host that rejected a cowbird egg,  whereas “acceptor” nests saw through the raising of a strange foreign cowbird hatchling. In all, 56% of ejector nests saw some the destruction of host bird eggs, but only 6% of acceptor nests were ruined. What happened?

Cowbirds happened. Females, actually. These jerks monitored the nests of their hosts, checking in on the progress of their young from time to time. If cowbirds found that their babies weren’t receiving the star treatment (or weren’t in the nest at all), the cowbirds would lay ruin to the eggs of the host bird. Essentially, these birds were exhibiting mafia behavior, laying down some pretty severe consequences if the host rejects the parasite.

What’s equally sinister is the explanation for destruction in the 6% of acceptor nests. Why kill the young of a nest that’s satisfactorily caring for your own young? Simple: murder creates room in the nest for more cowbirds.

In summation, I quite admire cowbirds. In a group of organisms whose ability to distinguish which egg is their own is questionable, these ladies are clever. It’s pretty rare to see such a sophisticated racket exist in animals with brains the size of beans. Think about the cognitive power cowbirds need to keep track of which nests are parasitized, then decide on whether to murder or not murder depending on what they see. I gotta say I’m impressed.

So, like a Don collecting tribute from his corner of Little Italy, cowbirds command respect. They’re clever, manipulative, aggressive, greedy, and all of it is so sinisterly bundled in a package that I’d rather enjoy petting.  Plus, it’s nice to know that some species out there gives others an offer they can’t refuse.

Alpine swifts’ 200-day non stop flight

Original photo credit: D. Occiato- http://www.pbase.com/dophoto

You know how damn exhausting it must be to fly? I don’t. Having never had the ability to fly without propulsion, I can’t say just exactly how hard it must be. Studying the metabolism of flying birds gives us some idea, and current evidence suggests flying is really really f**king hard.

A lot of people compare flying to swimming, which I think is a bit of a BS comparison. Water is a much more dense and heavy medium than air. Sure, it’s harder to move through water than it is to move through air, but long-distance travel through the oceans has the advantage of buoyancy to counteract the effects of gravity. Without having to spend energy from falling to the ocean bottom, all effort can be spent moving forward.

In contrast, flying truly is falling with style. Most of the forward energy generated from flight occurs because of gravity, or the downward force of the wing generating movement in the forward direction. Thus, flying animals are tasked with the mind-numbingly complex task of controlling their descent and forward travel, modifying body position as air currents change, all in an attempt to keep oneself from crashing into the ground in a puddle of crushing sadness.

Basically, it’s generally agreed that moving flying is more energetically demanding than swimming or walking. Migratory birds that choose to embark on long-distance flights typically rest for a while throughout the journey. Even the largest sea-faring gliders have to rest every few days to recover from their grueling haul.

Unless you’re the alpine swift. These aviary ass-kickers don’t stop for jack shit.

“But don’t birds have to land on the ground to eat, rest, or sleep?”. F**king nope, not the Alpine swift.

These birds are built for ass-kickery. They have a body design that’s conducive for long-distance travel, mixing flapping and gliding to travel long distances using little energy. And their yearly migration is a long one, beginning in the mountains of Western Europe across the Mediterranean and Sahara to their wintering sites in the African interior and back, a journey spanning some 2500 miles round-trip.

Migration routes and non-breeding range of three Alpine swifts breeding in Switzerland.

Migratory behavior of the three birds assessed in the study published by Leichti et al. Each bird is a different color, and the arrows represent periods of non-stop flight (Figure 1 in Leichti et al 2013, link below).

There have been rumors for decades that some swifts never land for any reason, which honestly sounds ridiculous and stupid. So, to resolve the stupidity, a group of Swiss researchers placed sensors on six Alpine swifts, seeking outline their migration from the Swiss Alps to western Africa for the winter. What they found, described in a paper published in the October 2013 issue of the journal Nature Communcations, ended up being so mind-blowingly balls out that I myself can hardly believe they didn’t just make it the f**k up.

The transmitters they used collected only two parameters: light level to extrapolate position, and acceleration to determine other metrics like pitch (a measure of body position, indicating whether the animal was in flight and where it was traveling), flapping rate, metabolic activity, and a few others. They were also able to tell when and where birds were breeding, wintering, or migrating based on how the birds behaved and where they were located.

This is the tiny transmitter used by the authors to collect data over an entire year. Science! Source: https://www.sciencenews.org/sites/default/files/images/js_tiny-data-logger_free.jpg

Based on the distinct difference in activity between roosting and migrating metabolic activity and pitch, the researchers observed that the three birds they recaptured in Switzerland the following year had been on the wing for at least 200 days. Every bit of food they ate over the trip was snagged in the air during migration. And sleep? Well, the authors aren’t really sure whether swifts feel the harmful effects of sleep deprivation:

“In Alpine swifts there seems to be no necessity for physical inactivity to maintain any of the relevant physiological processes. However, our data indicate that there are distinct periods of increased and decreased activity, which could go along with some kind of sleep in flight.”

Such periods of decreased activity suggest swifts spend several nighttime hours gliding to conserve energy or perform other physiological functions. The researchers’ data backs this up too; swifts were most active and had highest flapping rates near sunrise and sunset, probably because they need to ascent to great heights to avoid gliding into the ground overnight, and probably had to work to recover this altitude at sunrise. How do they control their flight if they’re asleep? Nobody really knows, but they may only sleep one brain hemisphere at a time.

So, despite hours of grueling physical activity, swifts seem to recover without having to land on the ground or water. They travel huge distances over impossibly barren terrain, hauling ass with more long-term gusto than any land creature ever documented. They’re masters of endurance and champions of travel with a purpose.  Also, never challenge one to a “lets’s see who can fly the longest” contest. Literally every other organism on the planet will lose.

Want to suggest a topic? Write it  in the comments below!

Further reading:
https://www.sciencenews.org/article/alpine-swifts-fly-nonstop-more-six-months

http://www.livescience.com/40268-alpine-swifts-fly-nonstop.html

 

 

 

 

 

 

Tetrodotoxin

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It kills in hours, and it does so by exploiting your own nervous system. By weight, it’s 10,000 times deadlier than cyanide.  It leaves you zombified and helpless yet conscious as you meet whatever deity you believe awaits you in the afterlife. This death, dear readers, is the result of consuming tetrodotoxin.

You may have heard of a Japanese dish called fugu. In Japanese, fugu refers to both pufferfish and the dish that is prepared using it. Pufferfish harbor the growth of symbiotic toxin-producing bacteria (remember mutualism?) in exchange for the extremely potent tetrodotoxin (called TTX), which acts as a defense against nearly all natural predators. Several important parts of the fish contain the toxin, including the eyes, ovaries, and liver of the fish. In Japan and throughout the world, Fugu is a culinary rite of passage of sorts, tempting risk-takers and novelty-seekers with the deliciousness of the dish and the intriguing oral numbness that comes along. The dish apparently also gets people high, which is pretty strange. Many also consider it one of the world’s tastiest fish. Sounds awesome, where can I pay money for some?

Fugu can also kill the shit out of you, which kinda sucks.

How? Stand back as I attempt to summarize how your nervous system works in a single paragraph using words any 5-year old could understand. Ahem.

Every single nervous system on the planet, from tiny fruit fly brains to our mondo-sized noggins, works exactly the same at the level of the cell. The workhorses of nervous tissues are cells called neurons that send one-directional signals, called action potentials, to other neurons. In a way, these cells talk to each other using electrical signals. Neurons become electrically excited on one end of the cell, but they have to transfer it to a completely different part of the cell in order to send the signal to the next neuron in the line. These signals move from one end to the other by opening ion channels, little gates in the cell membrane that allow tiny charged ions to move in or out of the cell. Sodium and potassium are the two most important ions in this process, so neurons have sodium channels and potassium channels that allow only those ions to pass through. Without these ion channels, the neuron cannot move ions and change its charge, making it impossible to talk to the next neuron in the circuit. Click here for a more visual explanation of how this works.

How does tetrodotoxin kill you to death? It simply clogs sodium channels. There’s a site on the sodium channel where tetrodotoxin sticks, and it sticks there freakishly strong. Because of that, tetrodotoxin hangs out and screws shit up for a really really long time. While similar toxins interact with sodium channels on the nanosecond scale (one billionth of a second), tetrodotoxin can stick to a single ion channel for f**king tens of seconds. THAT’S AT LEAST 100 MILLION TIMES AS LONG.

If I were tetrodotoxin, I’d be all over that sexy-looking voltage-gated sodium channel. Just look at dat TTX binding site. MMMMMMmmmm.

With no sodium passing through the channel, the neuron cannot generate an action potential. Not having neurons communicate can be pretty harmless sometimes, producing numbness or dizziness if the number of affected neurons is small. Plus, blocked channels don’t cause the neuron any harm, so it’s not like the toxin is killing nerve cells after it wears off. So what’s the deal, why is this toxin so fatal?

Well, the earth seems to have gotten pretty good at killing us. Most deaths today are due to conditions that attack two of our most important organs: the heart and lungs. In 2012, heart disease, stroke, COPD, lower respiratory infections, and lung cancers were the top 5 causes of death worldwide, totaling 21.9 million fatalities. This is not a small number. In fact, these five diseases alone are responsible for almost 2 of every 5 deaths.

If you were  trying to design a toxin that could kill large mammals like ourselves, you’d be right to target the heart, lungs, and anything necessary to make those work properly. You know how breathing requires you to move your diaphragm to suck in air and blow it out? Try it now, breathe without moving your diaphragm. If you think it’s impossible, you’d be right. If you aren’t moving your diaphragm and have not been for a long while, please call an ambulance. You have likely died.

Tetrodotoxin works so beautifully (for organisms that defend themselves with it, that is) because it shuts down our ability to control the muscles that move air into and out of our lungs. Without those, we suffocate to death, slowly and consciously. Nope. No, no way, no thank you, I’m out, screw that, better luck next time slugheads.

This is a particularly nasty death. Symptoms of toxicity begin with facial numbness, followed by facial paralysis. Then, gradually, the rest of the body goes numb, but not until after convulsions, loss of speech, respiratory and cardiac arrhythmia, and severe mental impairment occur. Then, fully-body paralysis results in either asphyxiation or cardiac arrest, during which patients are lucid or have only until recently lost consciousness.

How much toxin does it take to induce this? About 1/1500th of a teaspoon. Just one friggin milligram.

Fear tetrodotoxin. Fear it with every sodium channel you have.

For further reading:
http://www.chm.bris.ac.uk/motm/ttx/ttxv.htm
http://io9.com/5879406/how-the-puffer-fish-gets-you-high-zombifies-you-and-kills-you
Image credits:
http://i.telegraph.co.uk/multimedia/archive/01803/fish_1803259c.jppg
http://www.ch.ic.ac.uk/local/projects/quek/alfasub.jppg

Bat Echolocation

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Vision is awesomely complicated. A lot of animals, like the hawk, use vision to detect important environmental cues from vast distances. They use complex eyes and even more complex brains to locate prey, or figure out where the ground starts, or I dunno, check out lady hawks. Hearing is like vision’s less-popular but talented younger brother, the often-forgotten Luigi to evolution’s Mario. Hearing is amazing, yes, but our hearing kinda sucks. We’re not good at it, and so we discount its importance. Instead, we glorify vision as the pinnacle of evolutionary achievement, the ultimate sensory weapon against a hostile world. Yes, vision is awesome, and it is reliable, and it is useful for things like looking at steak. I f**king love steak. But other animals use hearing to see their steaks oh man that sounded really stupid so now it’s a run-on sentence now I don’t know how to end it oh no I’m embarrassed lol. The bat is one of the few animals that can accomplish this awkwardly-written steak hearing, and it does so using methods that absolutely amaze me.

It must not come to a shock to you that bats use echoes from their own calls to create a mental picture of the world around them. Bats hear with the precision of a rocket-tipped arrow, which sounds totally stupid because that implies the rocket should blow the arrow backwards and that’s not where the pointy end is, but this is not important. I will explain to you how they use variable auditory frequencies, interaural timing, Doppler shift, and badass brain parts to make a map of their world. In short, they use magic. Bottom line, bats are badass.

PARTS OF THE ECOCHOLOCATION PROCESS THAT ARE BALLS-OUT INSANE BECAUSE THEY GIVE BATS THE HEARING PRECISION OF A ROCKET-TIPPED ARROW.

1) The call
Did you also know that bats are really damn good at determining object size, velocity, shape, and even if it’s fluttering? I bet you didn’t, Mr. Fact Learner. You need to learn up all of your facts except that fact because you know for a fact that this fact is a fact, and that’s a fact.

Small bats usually emit two types of calls. First up are frequency-modulated (FM) sweeps, and bats use these to locate objects in the space around them. These calls are usually quick, and the pitch rapidly drops. This allows bats to emit a range of frequencies to the nearby area. The amount of time an FM sweep takes to return to the bat allows the bat to determine distance. Bats also use the time disparity between frequencies in the left and right ears to tell where objects are on the azimuth, or how left/right they are relative to the head.  The pointy shape of their ear also allows bats to use FM pulses to gauge the elevation of objects.

We got three properties down in one paragraph: azimuth, elevation, and distance. Isn’t that enough? Hells nah. They use some of them AT THE SAME TIME. For instance, bats can tell the size of an object by determining how loud the echo is. They can then use all of this information to tell the difference between something like a bird that’s far away and a moth that’s up close. FM calls are sweet.

The second type of call allows bats to tell how fast an object is moving. Constant-frequency (CF) pulses are typically longer, though the pitch does not drop. This allows, and yes I’m serious, bats to determine slight deviations in pitch due to the Doppler effect; a CF echo from an approaching object is slightly higher in pitch. This raises a good question: How can a bat do this if it’s flying toward an object? Wouldn’t the act of approaching an object make the CF pitch higher simply because the bat is moving towards it?

This next experiment sounds kind of insane, but I promise it really happened.

Scientists strapped a bat to a swing, pointed the swing at a wall, hooked up some microphones, and let loose. Sure enough, a bat swinging at a wall lowers the pitch of its emitted call. So, bats can compensate for their own movement through space by dropping the pitch of their call, making the pitch of the echo ALREADY ACCOUNT FOR DOPPLER SHIFT BY THE TIME IT GETS BACK TO THE BAT. Totally. Friggin. Badass.

2) The ear and auditory pathway
“Auditory pathway? Ughsheesh. That sounds boring. I don’t want to read about that.” said nobody awesome ever.

Our inner ears are pretty complicated. Without getting stained with details, sound transduction works basically like this:

1) Sounds, which are essentially air pressure waves, vibrate tiny bones in the middle ear that then convert those vibrations into pressure for the inner ear.

2) The basilar membrane, a bendy flap of tissue in the cochlea that looks like an industrial-strength file, vibrates in different spots based on the frequency of these vibrations.

3) The bending basilar membrane causes tiny hair cells adjacent to the cochlea to bend. These hair cells are connected to neurons that can detect when these hair cells bend.

What did we learn here? Basically, pitch matters. Low pitches vibrate different hair cells than high ones. Bats are crazy though. Really crazy. I once saw one bite the head off a human.

Bat basilar membranes, the part of the ear that transduces sounds into nerve impulses, are wider on the part of the cochlea where they detect the frequencies of their echoes. This helps for a number of reasons: 1) It increases the volume of noise in this frequency range, 2) It allows bats to become more sensitive to their own echoes, and 3) it helps reduce sensitivity to their own calls, reducing the odds of confusing those calls (or other sounds) with echoes. It’s also pretty cool to point out that bats contract muscles in their ears when they screech, dampening the sound of their calls further. All in all, bats are pretty much deaf to their own calls but highly sensitive to their echoes. Also, different bats are sensitive to different frequencies, limiting the odds of cross-talk between species.

Alright, this is about to get nuts. I recommend not reading this if you’ve just had a heavy meal, because you may be so amazed that you’ll spew half-digested mush all over your keyboard.

3) The brain
I’m so excited to tell you about bat brains that I’m literally going to get some Oreos. It turns out I was actually excited about the Oreos all along.

The auditory cortex is the part of the brain where auditory information is processed. You and I both have auditory cortexes. This is where information from the ears is organized and sent to other parts of the brain to aid in functions like cerebral processing, speech, and motor function. It’s also the part of the brain that allows us to differentiate between a high E flat played by a piano and a high E flat played by a chainsaw.

Bats have auditory cortexes too. Theirs do many of the same things as ours. But there’s got to be a reason I’ve decided to spend an entire section on their brains. Trust me, there is.

Remember how the cochlea can organize sounds by frequency? We tend to keep nerve impulses of similar frequencies bundled together as we send sound information from our ears to the auditory cortex through various brain structures. So, different parts of the auditory cortex become active when we hear different pitches, giving us somewhat of a tonal map of our sounds. Bats do this too, as do many animals.  Here’s the difference: bat brains are capable of producing an ACTUAL map based on sounds.

The bat auditory cortex has two pretty badass regions. One is the FM-FM region. Remember FM pulses? Those are the calls bats use to determine where things are in the space around them. This function is done here. Neurons in the FM-FM area respond to the amount of time in the delay of a call and the harmonics of the call’s echo? What is a harmonic? Click here to find out.

Think of the FM-FM area of the auditory cortex like a 2-D map. Each harmonic excites different horizontal sections from top to bottom, while the left-right axis responds to different delays. So, if the bat detects an echo from the 2nd harmonic after 8ms, neurons in a specific area of the FM-FM area will start firing. Enough of these allow a bat to tell how the large size and distance of the object is.

Bats auditory cortexes can also produce a mental map of sounds based on their velocity. Recall that bats use CF-CF calls to detect  the Doppler Shift of sounds and tell whether they’re moving. They process this information in the CF-CF area of the auditory cortex. Like the FM-FM area, certain cells become active when sound properties are just right. Bands of cells respond to certain CF frequencies, and other bands respond to the velocity, or Doppler shift, of the sounds encoded. What bats end up with is a map of awesome.

So what’s the point? Oreos can get me really excited. And to be specific, I’m talking about the golden ones. For some reason the regular Oreos get stuck in my teeth and I can never seem to get them out. Not that regular Oreos aren’t good, I’m just a little bit more partial to the ones that don’t annoy me. And bat brains, those are cool too. I wonder how they make the crème on the inside of the cookie. DO they keep it in big vats? I wonder how much would I have to bribe a guard to swim in that vat for 20 minutes.

Could you imagine if I ended the article that way? Hahahahaha. I am so funny. But seriously, I am actually going to end the article this way. You don’t get a summary of what I said earlier.

Comic

Want to suggest a topic for Badass Biology? Want to tell me how awesome a person you think I am? Interested in funding me? I didn’t think so. Anyway, leave a comment below and I might talk to you about stuff.

A big shout-out to “Behavioral Neurobiology” by Thomas Carew for much of the information and figures used in this article. Dr. Carew, if you’re reading this, you seem like a cool guy. Email me and we will go grab a beer and some Oreos.