Category Archives: Ecology

Saltwater Crocs: Showing How Dinosaurs Are Evolutionary Pansies Since 200,000,000 BCE

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In the waning years of the World War II Pacific campaign, British Marines and the 36th Indian Infantry Brigade landed on the shores of Ramree Island, Burma, after hours of aggressive naval bombardment. A swampy mud-soaked coastal island housing a wide variety of deadly wildlife and diseases, Ramree was key to gaining an Allied foothold on mainland Burma and reversing the spread of Japanese aggression in the region. The few thousand Japanese forces entrenched on Ramree repelled the Allied invasion during the initial weeks of heavy fighting.

January 26th, 1945, the battle turned when a force of about 1,000 Japanese defenders was routed by Allied forces. Surrounded on three sides by enemy units and hoping to rejoin the larger Japanese battalion on the other side of the island, the retreating Japanese opted for the most direct path; a beeline through the thick mud of a dense mangrove swamp. Their retreat was marred not only by the pursuing Allies but also by starvation, dehydration, mosquitos, scorpions, snakes, and one of the most infamously prolific people-murderers outside of the human species: saltwater crocodiles.

This is the last thing I’d want to run into at night in a warzone after being shot at for the past few weeks. Image source: unknown

It doesn’t take a vivid imagination to figure out that saltwater crocodiles are nothing short of gifted killers. At up to 22 feet long and more than two tons, they’re the largest reptile alive today. Saltwater crocs inhabit salty, brackish, and some fresh waters from the Indian peninsula through northern Australia and Southeast Asia, historically spanning northward to Japan. These waters are some of the most densely-populated human areas on earth, meaning the rate at which crocs and people meet face-to-face is higher than more fear-inspiring predators like sharks, hippos, bears, lions, tigers, wolves, cheetahs, dragons, mermaids, and unicorns.

Saltwater crocs, or salties, are primarily ambush predators, meaning they lay elaborate traps (jaws) in high-traffic areas (any volume of murky water larger than 5 liters) and wait for unsuspecting prey (anyone that will be dearly missed) to wander closely by (within 6-10 miles). Saltwater crocs in particular have the widest diet variety of any living crocodile. Crocs are typically apex predators in their communities, meaning they have the ability to catch, consume, and digest pretty much any other animal species from lower levels of the food web. Their prey includes smaller animals such as fish, crustaceans, and birds, but they’ve also been documented feeding upon larger mammals like deer, antelope, domesticated livestock, and humans. Given their size and musculature, it’s a wonder that saltwater crocs are surprisingly not voracious eaters and can go for weeks between meals. Let that thought give you comfort as you’re devoured alive.

Not only do salties eat nearly anything that moves, they also strike with deadly aggression.

Their bite force is the highest ever recorded; a large Australian saltwater croc broke the record with a bite force of 36,000 newtons. By contrast, this is about 40 times the force a human exerts and almost 8 times that of lions, tigers, and  hyenas. This number even rivals that of another famous predator, breaking into the lower estimates for that of T. rex. Scientists studying the evolution of crocodiles noted that the skull took on its characteristic shape, musculature, and bite before the emergence of other croc-like traits like body size, shape, joint structure, and limb placement, indicating that the bite force of crocs was a primary driver of crocodilian evolution.

On the other hand, saltwater crocs have very poor opening strength, and according to the Wikipedia article on their bite musculature, a few layers of duct tape can hold a saltie’s jaws shut. I’m not trying that anytime soon.

Once saltwater crocs get a hold of their prey, it may perform a famous behavior called the death roll. Keeping their strong hold on their prey, the croc will spin until the animal becomes separated or until the croc no longer detects movement. Most theorize that the death roll is largely an attempt to drown terrestrial prey, making them easier to consume. Others speculate that the purpose of the behavior is to rend torso from limb and produce manageable portions for easier digestion. Either way, the death roll is something with which the retreating Japanese on Ramree Island became all too familiar.

British scouts documented the horror the Japanese experienced in their retreat across Ramree. Screaming and desperate splashing were common sounds heard by the Allies in the night, sometimes punctuated by the characteristic sound of Japanese gunfire. Many speculated what horrors befell the dehydrated, starving, mosquito-plagued Japanese. Few outsiders witnessed and documented the event. Among the British forces scouting the Japanese retreat from outside the swamp was naturalist Bruce Stanley Wright. In his 1962 book Wildlife Sketches Near and Far, Wright elaborates on the event:

“The crocodiles, alerted by the din of warfare and the smell of blood, gathered among the mangroves, lying with their eyes above water, watchfully alert for their next meal. With the ebb of the tide, the crocodiles moved in on the dead, wounded, and uninjured men who had become mired in the mud.

The scattered rifle shots in the pitch black swamp punctured by the screams of wounded men crushed in the jaws of huge reptiles, and the blurred worrying sound of spinning crocodiles made a cacophony of hell that has rarely been duplicated on earth. At dawn the vultures arrived to clean up what the crocodiles had left…Of about 1,000 Japanese soldiers that entered the swamps of Ramree, only about 20 were found alive.”

Though many admittedly doubt the accuracy of Wright’s reported number of casualties, the statistic has earned the Guinness World Record for “most fatalities in a crocodile attack”. If Wright’s numbers are accurate, Ramree would be the deadliest attack by any animal on human beings in recorded history.

Few doubt the capability for saltwater crocs to bring that degree of torture upon humans. Many attacks like these occur in remote regions among populations of humans that fail to reliably collect attack data. Much of what we know about croc attack numbers comes from Australia where news reports and eyewitness accounts are more accurately described and distributed to the public. In Australia’s Northern Territory alone, 18 lethal croc attacks have taken place since 1987. Across all of Australia, the rate of deadly attack has skyrocketed from one every two years in 1971 to seven times that number in 2013, totaling 99. Of those, 27% were fatal, a low statistic compared to the country’s neighbors. In nearby Sumatra, 107 people have been attacked since 2007, almost 50% of which were fatal.

Image source: Outbackcooking.blogspot.com

One such attack was made famous by Hugh Edwards in his book Crocodile Attacks in Australia and made even more so by Bill Bryson in his entertaining travel novel In a Sunburned Country. In 1986, many moviegoers were entranced by the release of Crocodile Dundee, inspiring droves to visit the Australian wilderness. One such traveler was 24-year-old American model Ginger Meadows. Aboard the luxury yacht Lady G, Meadows and her newly-earned Australian friend stopped for a swim near the waterfalls at the beautiful King Cascades. The two women were quickly pinned in the water between a croc and a steep cliff. The girls began shouting, throwing their shoes, and tried to wait out the croc, but nothing could deter it. Meadows, a strong swimmer, attempted to make a break for the nearby embankment but vanished in a cloud of splashing in seconds. Caught in a death roll, Meadows looked to her friends desperately, but no one could do anything to help before she vanished. Her body was found floating and armless two days later.

The King Cascade falls, the site of the vicious crocodile attack on American model Ginger meadows in 1987. The attack occurred in the alcove left of the falls. Image source: Tripadvisor.com

Cases like these are hardly solitary. In 2003, a group of three adult friends were repairing an ATV in the Northern Territory when a crocodile fatally attacked one of them and chased the other two into a tree for 22 hours. In 2009, a 5-year-old Queensland boy was eaten in his own backyard trying to protect his new boxer puppy. In 2013, a New Zealand man was trapped alone on an island for two weeks when a crocodile attacked him each time he neared his boat. Last year, a 61-year-old man was snatched from his fishing boat while his family had their backs turned.

It must be said that a majority of attacks are non-fatal. It’s a common occurrence, especially in the Northern Territory, for locals to boast about close encounters with crocs. Sometimes, bait or cleaning buckets attract crocs to wayward limbs. Campsites, public spaces, or private residences located adjacent to croc habitat also can contribute to croc encounters. Excessive alcohol has also been tied to many attacks. Other times, the crocs attack objects like boat hulls, motors, fishing gear, and other inedible objects completely without warning or agitation.

Damage to an outboard motor done by an unprovoked saltwater croc in Australia’s Northern Territory. Source: ntnews.com.au

Though it’s hard to find any heart-warming aspects of the saltwater croc’s story, such things do exist. For one, a collection of Australian laws were passed in the 1970s that outlawed the unregulated trade of saltwater croc skins, a large contributor to critically low crocodile numbers. In the first ten years, the population exploded from 4,000 to nearly 30,000 animals, and today the number may be as high as 150,000 in the Northern Territory alone. To date, the recovery of croc populations from near extinction is the most successful predator conservation program in history.

Though saltwater crocs are among the most aggressive, deadly, and fearsome species in the animal world, they have also fascinated millions. From Steve Irwin to Mick Dundee, the raw power of saltwater crocodiles appeals to man’s primal urges of dominance and aggression. Crocs remind us of a by-gone era where reptiles the size of automobiles waged war on planet Earth. Perhaps that’s why we’re so entranced by them. Perhaps that’s also why we fear them so.

Further reading:

http://shadowreports.com/2011/04/13/eaten-alive-five-killer-croc-attacks-part-one-22-hours-in-hell/

http://www.couriermail.com.au/news/queensland/crocodile-tragedy-boys-family-leaves-daintree-river-home/story-e6freoof-1225812013828

http://mysteriousuniverse.org/2014/08/the-horrific-crocodile-massacre-of-ramree-island/

Cone Snails: The reason why I won’t be sleeping tonight

TitleSometimes, when I’m camping, I dream about angry bears ripping through my tent and attacking me for that forgotten bit of food I left in my pack. A perfectly logical nightmare, all things considered, but far from my worst. In that one, I was SCUBA diving with my cat when she encountered a 6-inch long cone snail. In a sudden flash of activity, one of my best buds was murdered in a rush of sadness and a chorus of bubbly muffled screaming.

I must have been about 12 years old at the time I had the nightmare, and it keep recurring. These nightmares started the same night that I first learned about cone snails and their cat-murderingly lethal toxins from a Disvocery Channel documentary. Not once have I had a nightmare about a Badass Biology topic, let alone one that still rips at the psychological wounds 13 years later.

What about cone snails makes them so horrible? So memorable? Get comfortable, I have a lot to write.

The 6 reasons why cone snails deserve to invade my nightmares:

1) I’m convinced cone snails are heralds to the war of the end times.

Cone snails look pretty innocent. In fact, many of them, like the textile cone pictured below, have intricate colors and gorgeous patterns that would make them desirable for any unsuspecting shell-lover to snatch in an instant. Just look at this little guy here:

Textile cone. I’d would seriously be inclide to play with this shell if I saw it, then I’d remember this article and swim away in a panic. I’d likely also wet myself in fear. Image source: Wikimedia

How cute, right? I think so. I’d hold him. However, what I wouldn’t expect is for that fleeting joy to be one of the last thoughts my brain could process before I’d rapidly be dead.

Unlike the garden variety of snail, cone snails are carnivorous marine snails. They’re common in Indo-Pacific waters, though they also inhabit the temperate waters around California, the Mediterranean, and South Africa among other habitats. The smaller varieties eat benthic invertebrates, though the larger ones must be quick and deadly to capture the small fish they feed upon. This selection pressure created one of the most badass weapons in the natural world.

To catch their quick prey, cone snails possess a small harpoon-shaped structure within the snail’s radula, a feeding structure that other snails use to scrape food from surfaces. In cone snails, the harpoon carries a toxic cocktail of sometimes hundreds of lethal compounds, all stored in a venom sac that supplies the harpoon with enough venom to apply to their next murder victim. This harpoon is used blindingly quickly, leaving little chance for their prey to escape. Then, after that, the cone snails engulf them whole with a mouth so horrifying that I cannot find the guts to post a picture here, thereby I suggest you just Google it.

HarpoonPic

Pictured above is the anatomy of the venom sac and a microscopic view of the toxin-tipped harpoon. Image source: theconesnail.com

2) Take a moment today to call your mother and let you know you love her.

Cone snails produce more toxins than any genus of organisms discovered by science. In fact, there are so many that an entire database has been developed to catalogue and characterize conotoxins, the potent toxic compounds present in cone snail venom. This database, called ConoServer, presently has 8482 chemical entries from no more than 215 species within the cone snail genus, a staggering number for a single organismal group.

But what are these toxic chemical compounds? Most are peptides, short strings of amino acids chained together with a special carbon-nitrogen bond. If these chains were considerably longer, portions of the string would begin interacting with other parts and fold itself into a protein, a type of molecule I’m sure you’ve heard of. Peptides, though shorter, are still useful molecules to manufacture, forming the surfactants that keep mammalian lung tissue from sticking to itself, adding nutritional value to milk, and in the case of our nightmarish cone snails, killing stuff really really quickly.

Conotoxin peptides are mostly used defensively. Most human stings are caused by a wayward foot delivered to a cone snail hiding in the sediment. However, roughly 10% or so of classified cone snail toxins have been found to be used in foraging and hunting, paralyzing their prey.

3) I am now hoarding Morton’s salt under my pillow in case one tries to break into my home.

All of the 600-700 species of cone snails are capable to stinging and injecting their toxins into humans. Not only are there a multitude of lethal toxins in a cone snail’s sting, but their lethality is nearly unparalleled. A useful way to measure how lethal a toxin can be is to measure what’s called a LD50, or the dosage expressed in mass/kg of body weight at which 50% of a population of test animals (usually rats) are killed. Arsenic, a well-known toxic substance, has an LD50 of around 15mg/kg, meaning it would take about half a teaspoon of crystallized arsenic compounds to kill a male human weighing 83.6kg, or around 181 lbs. The LD50 for some conotoxins can be as low as 0.005mg/kg, meaning you could very well be killed by conotoxin at a volume little larger than 10 medium grains of sand.

How do these toxins kill at such small dosages? If you’re an avid reader of mine, you may remember textrodotoxin, a neurotoxin in blowfish that kills by interfering with ion channels in neurons. Ion channels allow neurons to fire, and conotoxins bind to these channels with startling specificity, prohibiting their ability to function. Conotoxins kill humans in much the same way, and like tetrodotoxin, most human deaths from conotoxins are related to the asphyxia caused by the diaphragm being unable to contract. There is no anti-venom, and in some species like the geography cone, a sting is 70% fatal.

4) I strongly suggest we flee for the mountaintops.

Diabetic or not, you’ve heard of insulin. Insulin too is a peptide, and in humans it acts a hormone to help mediate the amount of glucose present in the bloodstream. Cone snails have now added another use for insulin in the natural world.

In January of this year, researchers published a study characterizing two species of cone snails that possess the first and only recorded case of weaponized insulin in the history of the planet.

That’s right. Weaponized insulin. Used as a predatory tactic, cone snails release insulin into the surrounding water when prey are nearby. It then passes through the gills of prey fish, enters the bloodstream, and drops the blood sugar enough to prevent the fish from having enough energy to flee the encounter,  all in a matter of seconds.

5) Oh dear God, there’s more?!

Conotoxins are so potent that there are serious efforts dedicated to determine whether they can be weaponized and used on mass numbers of victims by terrorists groups. In a paper published in the Journal of Bioterrorism and Biodefense, scientists outline the probability of a terrorist attack in the form of aerosolized conotoxins or contamination of food or water. Their verdict is surprisingly reassuring, citing the difficulty to extract most conotoxins from living animals and the difficulties synthesizing conotoxins in a usable and deliverable form. However, not all varieties of conotoxins face these same issues, and the risk of three broad biochemical classifications of conotoxins are candidates for bioterrorism should those few key technical hurdles be overcome.

THIS IS WHY I KEEP HAVING THESE NIGHTMARES. GAAAAAHHH, DON’T SWALLOW MY CAT!!! Source: AquariumAdvice.com and my darkest nightmares

6) Oh hey, a fact that’s not actually all that terrible.

Remember when I mentioned ConoServer, the online database that combines efforts of dozens of biochemists seeking to catalogue the vast variety of Conotoxins? Why spend the time to catalogue them if terrorists could simply learn to replicate these peptides in vitro?

Many of today’s most common and effective pain-killers carry powerful negative consequences. For example, the narcotic pain medications like the opioids hydrocodone (Vicodin), morphine, oxycodone (Percoset), and codeine are highly addictive and can leave patients with withdrawal symptoms after their course is complete. The hunt is on for a powerful non-habit forming pain killers with few side effects that can be cheap, easy to deliver, and easy to scale up.

Conotoxins may provide the solution. Much like snake venom, most research efforts on conotoxins are geared toward repurposing the toxins to serve as pain killers. Perhaps a single toxin or a cocktail of a few or several toxins could serve as potent yet non-costly painkillers, and collaborative research efforts like ConoServer could rapidly speed progress towards a revolution in patient care and pain management.

One promising conotoxin pain drug is ziconitide, a synthetic drug identical to a toxin produced by the cone snail Conus magus. Ziconitide has been FDA-approved for treating intractable pain and has shown some promise in its effectiveness. However, the drug degrades rapidly and cannot be delivered orally. Instead, ziconitide must be injected directly to the spinal cord via a surgically-implanted pump. Not terribly convenient if you ask me, but it seems to be a good start nonetheless.

Progress is being made to develop oral conotoxins-derived pain medications. In 2014, Dr. David Craik from the University of Queensland presented new evidence at the 2014 meeting of the American Chemical Society. Craik and colleagues looped peptide chains, amplifying their stability over the long-term while preserving their potency as analgesics. The prototype drug was given orally to test animals and showed nearly a 100-fold increase in effectiveness in comparison to the common painkillers morphine and gabapentin.

Overall, I find it pretty badass that such an effective killer lurks in the oceans. It delivers death in seconds to its prey and in minutes to a fully-grown human, and with no anti-venom, its effects are second to none. Hell, these guys even weaponized insulin. On top of that, they may gift humanity with a revolution in pain management. That’s pretty badass.

Want to suggest a future topic? Write it down in the comments below. Do it. Do it do it do it doitdoitdoitdotidoit.

For further reading:

http://www.conoserver.org/?page=about_conotoxins&bpage=keyrefs (list of current review papers on conotoxins as pain killers and the difficulties faced with their use)

http://www.theconesnail.com/ (lab website of the Olivera lab group at the University of Utah)

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.

How settlers and cows changed the face of south Texas prairies.

What you are about to read is udderly amazing. This being an article about the great state of Texas, currently my home, the steaks are high to make this one funny and I butter deliver. If you have any bull with what I have to say, go hoof it or I’ll get cheesed. At least give me the chance to milk this topic before you give me beef. Regardless, much of this article isn’t black and white, and I hope too that in some way you will find this article amoosing. Anyway, let’s herd this along, I’m getting hungry. Agriculture.

Cow Title

How settlers and cows changed the face of south Texas prairies.

Texas: the home of wide open skies, twenty acres, barbecues, and pecan pies. American culture paints an idyllic and rugged picture of Texas. Cowboys herd cattle through vast expanses of fence-less plains. Prairies full of lush grasses as far as the eye can see. The picture in your head probably isn’t too far off from this:

Photo credit: Pondero (http://pawndero.wordpress.com/)

Had you visited central or south Texas 120 years ago, this would’ve been largely accurate. However, over a span of a few decades, an alarmingly large portion of Texas has transformed from a landscape of endless grass to something much much uglier:

What you see nowadays is mesquite, prickly pear cactus, and some small brushy shrubs displacing the miles and miles of grasslands that historically covered much of Texas. How did it get this way? And, more importantly, can we blame something else for it besides ourselves?

Even if you’ve never seen the Lion King, you’re likely still aware of cyclical nature of life. Among these cycles is succession. A habitable area becomes damaged by some event, like an eruption or a bulldozer clearing land for farming. The vacuum of space and resources left behind gets colonized first by r-selected species. These species are really good at dispersing over wide distances and taking root in new places unaided by other species. The unfortunate cost to being an r-selected species is that it’s generally very hard to compete, especially with k-selected species that take longer to colonize a disturbed area but competitively dominate more easily once they’ve done so. So, over time, a community of plants or animals can shift from being primarily r-selected to k-selected, completing the cycle of succession until the next disturbance event.

A typical course of succession on a plot of cleared land. R-selected strategists invade first, but are gradually out-competed by hardier but slower-growing k-selected species like hardwoods. Heh. Hardwoods.

Prior to about the 1880s, the most common form of disturbance in south Texas was fire. Prairie grasses would naturally form dense expanses of flammable material, and the slightest spark could create wildfires that spread for miles. The constant and intense winds blowing from the Gulf would aid in spreading fires over vast distances, removing all the built-up grasses and allowing new ones to take root. Another consequence of these natural fires is that shrubs, cacti, and trees, all more k-selected than the weedy grasses, could not colonize the prairie successfully because the odds of surviving these fires was so low. And because it took such a long time for these plants to move into a space, even one cleared by fire, they never really became dominant in these regions because fires were so common.

The catalyst that sparked change in Texas prairies was the large influx of cattle ranchers in the late 19th century. Early Texas ranchers understood the importance of fires and would perform yearly burns of ranchlands, and it was clear that the annual new growth of grasses improved the health and size of their cattle making for tastier Ribeyes and jucier Sirloins. However, once the density of cattle began to explode, grazing on these grasses intensified, leaving empty patches clear of the combustible material necessary for fires to destroy old growth. Fires became less and less effective and spread to a fraction of the area and intensity that they were mere decades before.

Here’s where the opportunistic k-selected species began to invade. With reduced damage by fires, seedlings of mesquite, oak, and various shrubs had a better chance of setting up a home on the range. Once they did, the shade they created further drove down the density of flammable grasses and added more space between plants, inhibiting fires even further. The end result facilitated the invasion of other plant types including a host of cacti and small shrubs.

Why does any of this matter? Put simply, economic growth in the region took a heavy blow. In a surprisingly well maintained old-ass report published by the U.S. Dept. of Agriculture in 1908, the consequences of bushes on ranching and farming became clear: “South Texas is being rushed under the plow to escape the invasion of bushes. Large tracts which could have been bought a few years ago for a dollar or less per acre…now cost $5 or $10 an acre to clear of woody growth…many thousands of acres are already lost, at least to the present generation, for the bushes are so well intrenched that the cost of clearing would greatly exceed the value of the land”.

Despite these difficulties, the face of south Texas is likely to continue to change. The currently dominant plant species in the area are only transitory, and often they give way to larger trees that can outcompete the smaller brush. Many experts think reforestation is a likely consequence in the coming decades, though a gradual one. Swampify isn’t a word, but it should be.

I want to make clear that despite the usage of the term “south Texas”, the area impacted by mesquite invasion is friggin massive. The amount of land encompassed between Houston, the Rio Grande valley to the south, and the border town of Del Rio to the west is roughly the size of the state of South Carolina; some 32,000 square miles. And these boundaries only generally reflect the affected areas because these are among the only Texas towns I can name off the top of my head. Regardless, the difficulty of this invasion has undoubtedly shaped Texas history and the outcomes of economic competition with other Southern states.

The overall point of cases like these is that human beings have a profound and measurable impact on the land from which we obtain our livelihoods. The issue of responsible land management is arguably one of the greatest problems facing our generation. Properly managing sensitive natural areas is crucial for the future of economic growth and development.  Unfortunately for us, it’s almost never clear what the best approach is to battling habitat degradation. What would have worked in south Texas? Limiting the density of cattle? Denying settlers the opportunity to buy arable land? Freezing growth in a developing Texas? Eating more cows? I am seriously hungry.

Since I’ve moved to Texas, I’ve gotten the chance to do a lot of characteristically “Texas-y” things. I’ve saved a friend’s beer while floating the rapids on the San Marcos. I’ve hiked Guadalupe Peak. I’ve stopped on the highway to take pictures of the springtime explosion of Texas Blue Bonnets. I’ve seen the millions of bats at Devil’s Sinkhole and seen Kemp’s Ridley turtle hatchlings make a run for it on Padre Island. Hell, I’ve even yelled at cows from a moving vehicle. Enjoy these things while they last, because those cows may just eat all your land to death. The end.

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.

Pistol Shrimp

“Wtf, shrimp!!? I make it all the way to this website from who knows what part of the internet, and I see ‘Badass Biology’. Man, Kevin, you flip my brain out with possibilities of flying sharks, rabbits of doom, or a half-honeybee half-unicorn rainbow pollinators. And what do you deliver? A stupid shrimp??! I hate you, and I quit this website. (╯°□°)╯︵ ┻━┻)” To which I reply, “Charles Barkley, I think you’re over-reacting. Please repair my table at once”.

Yes, it’s a shrimp. A measly two-inch-long shrimp. But you don’t understand. This one single stupid shrimp is just about the coolest thing I’ve ever heard. Trust me, and when you hear one too, you’ll probably go deaf, because this one little shrimp IS ONE OF THE LOUDEST ORGANISMS ON THE PLANET. I’m talking 220+ decibels, much louder than a gunshot and louder than standing next to a jet engine at take-off. O_o.

First, I want to talk about some other wicked cool stuff this little guy does apart from being a tiny walking firework of sonic pain. These shrimp garner lots of attention from ecologists because of their symbiotic, or mutually-beneficial, relationship with gobies, a type of small marine fish. The coral reef populations of this shrimp build burrows and recruit the help of a goby to stand guard out front while being no more than an antennae’s distance from the shrimp, using the goby’s well-developed vision to watch for danger. Once danger comes, the goby flicks its tail to signal a threat, and both the goby and the shrimp retreat into the same burrow. Then they start slapping five. It’s flippin sweet.

From an ecologist’s point of view, this is totally mutualistic, and some scientific literature lists this interaction as “totally f-ing amazing” [citation needed] (Good luck with finding THAT reference -ed.). Yeah, both the goby and the shrimp live to see another day should a shark, barracuda, squid, rogue buoy, really fast snail, very-misplaced land predator, sinking boat part, cloud of wasps, or sentient shrimp-hating spear come around to threaten them. The goby gets a burrow, and the pistol shrimp gets a gargoyle. Selection at work.

I like to think of the goby as the pistol shrimp’s pet, kinda like me buying a falcon and parading it around the neighborhood on a leash. And once danger comes, the falcon goes “Hey yo, Kevo, you might need to reconsider this route”, we split, we don’t find danger, and I buy the falcon ribs for a job well done (and because I really want ribs right now). So in a sense, pistol shrimp are danger shepherds equipped with sun-blasting cannons of glory that we’ll get to in a moment.

I need to take a break to collect myself. Holy balls, these shrimp own everything own-able. Next time I see one, I’m buying it ribs. The whole rack.

Let’s get to that “pistol” thing, why don’t we? Pistol shrimp have one very distinct set of front appendages, like two arms extending outwards from its body. Only, one of these arms is disproportionately larger than the other, and it’s quite a contrast. Like no foolin’ man, this one arm alone can be as long as half the entire length of the shrimp’s body. Imagine walking around with one of your arms the size of the Hulk’s and you get the idea. This may look pretty stupid, but this powerful musculature operates one of the most badass weapons nature can offer.

Yeah, kinda like this

When in serious danger or when hunting, the pistol shrimp cocks its massive claw backwards into a 90oposition. Once the claw snaps shut, it produces a jet of water propelled forward at 60mph. Yeah, woo, a fast water jet. Big deal. But here’s the amazing part. Are you ready to have your mind blown? If you have ever listened to me before, now is a pretty good time, too: This jet of water creates a bubble that cavitates, or implodes, generating a pressure wave that creates a sound loud enough to break glass in an instant. Not only that, but once the bubble cavitates, the heat generated by the force of the implosion causes the temperaturesinside the bubble to reach about 18,000 degrees Fahrenheit. Yes. Eighteen. Thousand. Oh, and to top it off, the whole process takes three tenths of a second.

THIS TINY SHRIMP MAKES A BUBBLE SO AWESOME THAT IT’S LOUDER THAN A JET AND MORE THAN TWICE AS HOT AS THE SURFACE OF THE SUN.

 

You can imagine the horribly bubbly doom the pistol shrimp’s enemies must face. Stunned (or killed) by the force of that kind of pressure change, the pistol shrimp’s prey has basically just become lunch in an instant. The shrimp pulls its quarry into its burrow, and goes to town, just how I could go to town on some ribs right about now. I dug up a video about this whole process in case what I said wasn’t convincing enough:

If you want me to write about any other badass biological bosses, leave a comment. I may talk about them, or I may just tell you that your suggestions are awful. Probably not the latter though. I like people.

Well, I like most people except you, Charles Barkley. I really miss that table. Now I’ve got nothing to rest my wine on when Glee’s on.