It’s been 25 weeks since we started this epic journey through the alphabet together, and sadly we are nearing the end. At this critical juncture, just one letter away from the finality of zed, I thought I would bestow my Pharaoh powers on to you, dear readers.
Comment below with your burning science questions, and I will answer them all next week in my final ABCs of Interesting Things post.
Thank you for reading. I leave this quest in your very capable hands.
For those still aching for some interesting science facts, how about these “you” facts:
All of the atoms in your body were made inside stars, as the great Carl Sagan said the 1980 TV Series Cosmos: “The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies, were made in the interiors of collapsing stars. We are made of starstuff.”
A lot happened in the summer of 1954. The world’s first atomic power station opened in Russia, Alan Turing committed suicide, the CIA set up a coup in Guatemala, food rationing finally ended in the UK, and the first edition of Sports Illustrated was published. Some pretty big world events, right?
You know what else happened? 22 white, middle class boys boarded a bus to a Boy Scouts of America camp in Oklahoma. And I’m going to tell you why you should care that they did.
The Robber’s Cave Experiment
On one (presumably sunny) day in 1954, two busses each picked up eleven 11-year-old children who had been screened to be “normal” (Remember, this was 50s America, so that meant white, protestant, middle class, two parents, above-average test scores) and who didn’t know each other. The busses drove their “normal” boys to a summer camp called Robber’s Cave and deposited them on opposite sides, each group not knowing that the other existed.
For about a week, under the careful surveillance of psychologists posing as counsellors and camp staff, they participated in group bonding activities. [In some ways, ethics boards have made psychology a lot more boring. At the same time, it’s probably better that we now consider it unethical to Truman-show 22 pre-teens].
They camped out, played baseball, went swimming, and generally got to know each other. They even came up with a name for their groups and emblazoned insignia on their t-shirts and caps. One group killed a snake by a river and dubbed themselves the Rattlesnakes, the other group decided to be patriotic and called themselves the Eagles.
Then came the interesting part.
The experimenters introduced the groups to each other.
The Eagles and the Rattlesnakes were pitted against each other in a series of competitions – baseball, touch football, tug-of-war, and a treasure hunt. The key aspect of these games was that one group always won and the other lost. They were zero-sum games.
The result was a little bit scary. The groups started to hate each other. It started off with names like “sneak”, “cheat”, and “stinker” but soon developed into cabin raids, flag-burning, and even one Eagle telling another to brush the “dirt” of his clothes after bumping into a Rattler. There was some serious xenophobia (fear or disgust for the “other” or “alien”). The experimenters stopped the activities for fear of escalation to serious violence and started to think about how they might eliminate this extreme prejudice.
The crazy part is that these were all “normal” boys who didn’t know each other beforehand and had no reason to hate each other besides that their groups (that had also only been formed weeks ago) were in direct competition.
The experimenters tried to bring the groups together at mealtimes and for positive evening activities, but that only served to escalate the hatred. They hurled food at each other at dinner time and jostled to be first in line.
What the experimenters tried next was pretty genius. They got the groups to try and work together to solve problems that affected everyone. One night the truck that was supposed to deliver food “broke down” so they all teamed up and pulled it out of the ditch with their tug-of-war rope. Another day, the water supply pipeline broke and they all worked together to find the leak. These superordinate (larger than the group) goals brought the Rattlers and Eagles together.
Inter-group relationships built because of these events and at the end of the camp, some campers asked to mix up the busses and one group that had won $5 in a competitive contest offered to buy milkshakes on the ride home for the whole group. How nice. They had been reconciled as easily as they had been set against each other.
A 1997 study showed how this sort of reconciliation can be contagious. It isn’t just people who have friends in other groups who will be more likely to be empathetic. If you know someone who has friends in another group, you will be more likely to be nice to people in that group. Sounds a bit complicated, but basically if you have a friend who is a clown, it’s not only you who will be more likely to not hate clowns, but also all of your friends. As soon as a few Rattlers got to thinking that maybe the Eagles weren’t so bad, the positive feelings probably spread pretty quickly.
Chemical Basis for Xenophobia
But what was going on in their brains to make this happen?
Don’t worry, the kids weren’t lobotomized to find out.
A 2010 Dutch study out of the University of Amsterdam showed that Oxytocin, the “cuddle chemical”, might have something to do with it.
Research subjects who had ingested some Oxytocin were more “ethnocentric” than their placebo-munching counterparts. People with a bit of extra Oxytocin in their systems were more likely to say they would sacrifice the lives of many outgroup members to save the life of one ingrouper and associated more positive, human words with ingroupers and more negative, dehumanizing words with outgroupers.
The Robber’s Cave Experiment was one of the first field experiments in social psychology. It inspired Philip Zambardo’s Stanford Prison Experiment and Stanley Milgram’s Obedience Experiment. It pushed people to consider why they acted in bigoted ways and showed how easy it can be to both turn people on each other and bring them back together. When we mistreat people who belong to different racial/social/economic groups, are we really being any more than rational than the Eagles and Rattlers? No, we aren’t.
Muzafer Sherif is also famous for a series of studies using an interesting phenomenon known as the autokinetic effect. he showed that people will create group norms and stick to them even when the group is taken away.
It’s summer time. And you know what that means? Sure, summer means picnics, barbecues, and sun.
But it also means the coming of the most dreaded outdoor villains: wasps.
Some people freeze up when they see the stripey serial stingers, others try to wave them away. I prefer the stoic strategy of a short, sharp yelp followed by a crazed hand-waving motion. It’s not a conscious decision, nor one that I am proud of, but the wasps seem to get the idea that I don’t want them around.
What is a wasp?
In taxonomic terms, a “wasp” is any member of the suborder Apocrita that isn’t a bee or an ant. While that may help useful for biologists, it doesn’t really tell us anything about the creatures.
Wasps are a varied group of hairless, six-legged flying insects that measure anywhere from to 1mm (Fairy Wasp) to 4.5cm (Japanese Hornet). There are thousands of species of wasp, many of which are specially adapted to feed on and parasitize insects we would regard as pests.
And the way they parasitize those pests can be cruel indeed. Some parasitoid wasps lay their eggs inside their prey, only to have the eggs hatch a few weeks later, letting their young eat their way out of the unsuspecting caterpillar that has been feeling a strange itch recently.
Other wasps lay their eggs inside plants, genetically modifying a plant’s seeds to suit the wasp’s needs.
Still other inventive wasps have figured out that they can lay their eggs in the nests of other wasps and trick another queen into raising their young.
It seems there is nothing a wasp won’t lay its eggs in.
Not all wasps are content merely laying eggs in unusual places. Some have acquired a taste for honey.
Meet the Japanese Giant Hornet.
While European honeybees haven’t developed defenses, asian honeybees have discovered a way to fry invaders.
So while you may just think of them as a nuisance when you’re trying to enjoy your picnic, remember that with wasps, there is more than meets the eye.
No, I’m not talking about taters. I’m talking about tardigrades: quite possibly the most durable creatures on Earth.
They might also be the strangest combination of cute and terrifying anybody has ever seen looking through a microscope.
Tardigrades, also known as water bears, evolved 500 million years ago. They have survived on a diet of moss and lichen since around the time the first fish evolved and shortly after animals evolved at all. While their basic body plan hasn’t changed much, they haven’t been evolutionarily idle. They’ve developed some pretty neat adaptations (some of which will be discussed below) and diversified into over 1000 unique species. One thing all of these species has in common is size: all species of tardigrade measure between 0.1-1 millimetre (comparable to the size of a single salt crystal).
The amazing thing about these itty-bitty balls of chitinous cuticle is that they can withstand pretty much every type of extreme we can cook up. They’ve been boiled to over 150 degrees celsius without breaking a sweat. They’ve been frozen to -250C and didn’t need tiny parkas. They’ve been dipped in acid, shot into space, dried out, and zapped with thousands of times the lethal radiation dose for a human and they just kept chugging.
Why are we being so cruel to these tiny creatures? Because they keep surviving. Things that terrify us and would kill almost any lifeform barely even faze them. Tardigrades have expanded the notion of habitable environments and understanding their indestructibility has profound implications for both earthbound medicine and for life on other worlds.
I think tardigrades are pretty darn cool. This is likely due in no small part to the fact that the lab where I did my thesis in undergrad was home to a healthy colony of moss-eating tardigrades. Up on the third floor of the Life Science Building at McMaster University, my former supervisor, Dr. Stone (or Doc Roc as he likes to be called) has been testing tardigrade tolerances with Taru, his PhD student.
I got in touch with Doc Roc this week to ask him a few questions about tardigrades. To give you an idea of the kind of (awesome) professor he is, one of his research goals was to publish a one-sentence paper. He accomplished that goal with the help of quite a number of semi-colons. As you’ll see below, I think he likes that useful but oft-forgotten punctuation mark.
Thoughtful Pharaoh (TP): Where do you find tardigrades?
Doc Roc (DR): Tardigrades are found the world over, literally on all continents and in all bodies of water; they inhabit all systems, marine, freshwater, terrestrial; they occur terrestrially on moss.
TP: What have you done to test the limits of tardigrades?
DR: We have tested their tolerance to temperature (cold), radiation, desiccation, pH, g-forces (simulated), and red food dye (I think that you know the tale); we have witnessed complete revival from -80 degrees Celsius for up to 6 months (but they can tolerate -250 K); 4000 Gy radiation (6 Gy kills humans); completely drying out inside an evaporating water droplet (tales in the literature purport over 100 years in a desiccated state); over 16000 g (Earth atmosphere being 1 g – meteoritic impact being an order-of-magnitude greater, however); and sensitivity to red food dye.
[The tale of the red food dye: In one of many discussions of tardigrades in that lab, I was asking if these incredible creatures had any weaknesses. Doc Roc told me about a curious incident that happened when he tried to stain tardigrades to see them better. He tried putting some red food colouring onto the plate and they changed colour and were easy to spot, but they also all died. Green and blue food colouring did nothing, but red colouring stressed the tardigrades to death. Strange that such an indestructible creature could be undone by food colouring.]
TP: What is the most interesting thing about tardigrades, in your opinion?
DR: I think that understanding how their tolerance and reproductive modes (e.g., parthenogenesis) evolved are the most interesting topics for tardigrade research.
[Tardigrades don’t need males to reproduce. Females can lay unfertilized eggs which will hatch as clones, genetically identical to the mother. The advantage of this is that they don’t need to waste time looking for mates. The disadvantage is low genetic diversity.]
TP: What do you want to do next?
DR: We plan to investigate how they tolerate the high radiation doses (e.g., their DNA repair mechanisms).
[McMaster has a small nuclear reactor on campus, which has been used in recent years to expose tardigrades to high levels of radiation. After thousands of times a lethal radiation dose for humans, the tardigrades were fine and in some cases the irradiated ones did better than their lab-housed control counterparts. How they can survive and continue to reproduce remains a mystery but it almost certainly involves some incredible DNA repair.]
TP: Do you ever name the tardigrades?
DR: The student who studies them is named Taru, which seems an appropriate name for one; given that we work with a parthenogenetic species, I would name them Tarugrade 1, Tarugrade 2, …
[Seems reasonable to me.]
TP: If they’re so invincible, why haven’t tardigrades taken over the world?
DR: Organisms are limited in their resources, so populations can grow unchecked only to the extent that living materials are available (populations crash thereafter); predators additionally can reduce population sizes.
[In other words, tardigrades can still starve and get eaten. Just like every other creature.]
TP: What can studying tardigrades tell us about life on other planets?
DR: Studying tardigrades can inform us about the limits to which organisms can survive, helping researchers to identify which extreme environments are viable and whether organisms could be transported between planets.
Westley: Rodents of Unusual Size? I don’t think they exist. [R.O.U.S. attacks Westley] Westley: Ahhhh!!!
Why is that my favourite scene? Because I laugh every time I watch it. The R.O.U.S. is just so ridiculous-looking and shows up right after Westley disbelieves its existence.
For the devoted readers out there, you’re maybe wondering what my obsession with R.O.U.S.es is, because I’ve written about them before, but somehow they capture my imagination unlike any other strangely-proportioned creature. I think it has something to do with the comedic effect of reversing the expectation of something cute.
The R.O.U.Ses from the Princess Bride have come to set the standard for overgrown rodents, but sometimes reality is stranger than fiction.
The largest discovered member of the rodent family (membership to which depends on having a pair of razor-sharp, ever-growing incisors), Josephoartigasia monesi is estimated to have been the size of a bull.
Since only its skull was discovered, the weight of this creature has been debated. The original discovery paper pegged the mass of the monstrous mulch muncher at 1211kg on average with a maximum of 2584kg. To put that into perspective, that’s anywhere from 1 to 4 dairy cows. A more recent study, however, showed that depending on the part of the skull you use to predict the mass of the full creature, J. monesi could have weighed from as low as 356kg (half a cow) to 1534kg (back up to the 2-cow range). Even if the creature was as small as 356kg, that still makes it nearly 6 times heavier than the current rodent heavyweight champion of the world, Floyd Mayweather the capybara.
Ratzilla’s bite force was recently estimated up to 4000N, enough to outperform modern crocodiles and tigers. It was definitely a herbivore though, and is thought to have used its teeth as elephants use their tusks: to dig around for tasty treats.
Luckily for us, Ratzillas (Ratzillae?) no longer roam the plains of South America. They went extinct about 2 million years ago, after 2 million years of rodent dominance. Interestingly, that makes them the contemporaries of terror birds, sabre-toothed cats, and giant ground sloths. Their size and sharp teeth probably made them tough prey items.
Just like the R.O.U.Ses in the Princess Bride though, they were probably susceptible to fire jets and swords.
And with this rodent rant written, I promise to not write about any more Rodents of Unusual Size for the remainder of this ABCs series.
What’s half a metre long, weighs 3-4kg, and has the cutest face you ever did see?
Yup, there it is! This, dear readers, is a quokka. A native of South west Australia, this marsupial has recentlyskyrocketedto fame because of the way its mouth seems to rest in an adorable little smile. A quick Google image search will reveal hundreds of awesome pictures (that aren’t licensed under creative commons) and a growing number of quokka selfies. It looks so happy that it has even been dubbed the mortal enemy of Grumpy Cat.
So, what’s the deal?
The quokka is a vegetarian (one of those darn salad-eaters) that prefers leaves and stems. Since its habitat is so dry, it will swallow its food whole only to regurgitate it later, chew it up, and swallow again in order to make sure it sucks out all of the moisture. Their digestive systems are tuned to allow survival in the dry climate of Western Australia. This means that when humans try to feed the quokkas with bread or give them water, the poor animals can go into toxic shock and die. For the love of all that is cute in this world, do not feed quokkas.
Like other marsupials, quokkas have a very short pregnancy of only one month, followed by five or six months of pouch-time. Unlike most other marsupials, quokkas have the ability to double down on their reproduction. The day after giving birth and moving the joey to their stomach pouch, female quokkas will mate again and will pause the development of the new foetus in a process known as embryonic diapause. If the joey in the pouch doesn’t make it (quokka-god forbid), the female can resume the embryo and still call the season a reproductive win.
One thing the quokka’s PR people (who have done an excellent job so far, by the way) might not want you to know is that female quokkas, when threatened by predators, will quite literally throw their babies under the bus. They will eject their joey and head for the hills, hoping that the predator takes the easy prey and they get to live another day.
For the readers out there still keen to snap the perfect selfie, the best place to find quokkas is on Rottnest Island, a tiny, 19km2 bit of land off the coast of Perth. [Non sequitur – I can’t help but hear “Purse” said with a lisp whenever I come across Perth.] The island was named Rottnest (Rat’s Nest) by a dutch explorer who thought the resident quokkas looked like “a kind of rat as big as a common cat”.
Just like the selfie stick we know is lurking out of the frame of all those hilarious pictures, disaster may be around the corner for the quokka. The Australian Government rates the Rottnest Island population as stable, but the quokka’s mainland habitats are under threat from foxes (an invasive species) and forest clearing. These threatened mainland populations are especially important because they contain much more genetic diversity than the island groups. The IUCN classifies the quokka as Vulnerable, one step above Endangered. This is due not to the population size (upwards of 10 000), but rather to the extremely small range and susceptibility to environmental change.
The quokka is a species of very cute and biologically strange marsupial whose Australian home is under a myriad of threats. Why the internet is currently abuzz with it remains a mystery, but there are certainly some adorable pictures to be taken and some interesting things to be learned.
Unbeknownst to the rest of us, a debate has been raging in the world of biogeography. The debate stems from a simple observation made by a young Canadian scientist in 1964: island animals are weird. Sometimes they’re way bigger than normal, like the Tenerife Giant Rat, and other times they are way smaller than normal, like the Elephas falconeri, a tiny species of elephant.
J.B. Foster published a short, two-page paper in the April 1964 edition of Nature positing that rodents get bigger and lapidomorphs (rabbits), carnivores, and artiodactyls (deer/goats) get smaller on islands. This, he thought, was because small animals found the isolation of islands to be liberating. They no longer had to worry about predators and could grow to fill their new space. Larger animals, however, might be restricted by the relative paucity of resources on islands and would have immense evolutionary pressure to become smaller.
This led to Foster’s Rule, also known as the Island Rule. It states that in general, big animals get small on islands and small animals get big. They also do so very quickly (in evolutionary terms). For instance, red deer on Jersey, an island in the English Channel, were shown to have shrunk to to 1/6th their original size in only 6000 years.
There’s a problem, though. Like pretty much every rule in biology, there are lots of exceptions. Sometimes small animals get smaller (like Brookesia micra, the world’s tiniest chameleon) and relatively big animals get bigger (like Haast’s eagles).
A 2011 article by a joint Israeli-Italian-British team of researchers calls the whole theory into question, showing that the smallest species in any given group is no more likely to be from an island than would be expected by chance. Size extremes, they say, exist everywhere. Islands don’t have some sort of monopoly. They do concede that large mammals tend to get smaller, but they think the idea that small animals get bigger only seems like common sense because they are easier to notice.
A British paper from 2008 throws even more confusion into the mix, showing that depending on the kinds of statistical tests you use, you can show that the island rule either exists or doesn’t. They suggest that the island rule should be looked at in “taxonomically restricted studies” – biologist-speak for “case-by-case basis”. That seems to kind of defeat the purpose of a nice heuristic, though.
One thing we know for sure is that islands isolate organisms. This isolation means that evolution can work differently for the island population and might lead to all sorts of interesting changes. This type of evolutionary change is also called allopatric speciation and is responsible for the variation that Darwin saw in Galapagos finches. Whether islands always create a particular kind of change is still up for discussion, but nobody can doubt that when organisms of unusual size appear, they deserve attention.
When was the last time you ate dinosaur? I had some just the other day, next to my peas and carrots.
Shocking as it may seem, dinosaurs are all around us and we interact with them on a fairly regular basis. If you’re sitting there saying to yourself, “No, dinosaurs went extinct millions of years ago!”, let me remind you of one critical and oft-forgotten fact: all modern birds (including chickens, turkeys, toucans, and cuckoos) are dinosaurs. That’s right, the mascot for Froot Loops is a dinosaur. KFC can change it’s name to Kentucky Fried Dinosaur and still be scientifically accurate.
How can this be? It all has to do with how biologists name and classify organisms (the technical term for this is taxonomy). Scientists, being very much into order and rationality, made up a few systems for naming organisms and describing their evolutionary relationships. The system I’m going to focus on today, cladistics, has only a few basic rules and is incredibly helpful for understanding the history of life on our planet. Unfortunately it can be a bit daunting because there is some pretty scary-looking jargon. Let’s unpack some of that jargon and apply it to dinosaurs in order to find out how the heck the same word can be used to (correctly) describe animals as different as stegosauruses and canaries.
Two of the most important concepts for cladistics are that:
All life on Earth evolved from a single common ancestor.
Organisms should be classified based on last common ancestors, with organisms that share recent common ancestors being interpreted to be more closely related than organisms with more distant common ancestors.
Think of your family. Everyone is descended from your grandparents (premise #1 above) and you are more closely related to your siblings (last common ancestor is your parents) than your cousins (last common ancestor is your grandparents; premise #2 above).
Those are the basic rules of cladistics. Pretty simple in theory, right? The problem is that with organisms that have been dead for millions of years and only leave behind fragments of bone, deciding where they fit in to the family tree gets difficult.
Now let’s look at some of that jargon I promised.
The first word we need to understand is monophyletic. A monophyletic group is a set of organisms that all share a common ancestor. You, your siblings, and your mum make a monophyletic group. You, your siblings, your mum, and your dad are not monophyletic because (hopefully) your mom and dad are not related. Some scientists call monophyletic groups clades and they are the bedrock of cladistics. A “proper” group must be monophyletic.
If the group you’re looking at isn’t monophyletic, it might be paraphyletic or polyphyletic. These are two types of almost-groups that can confuse a lot of people. Paraphyletic groups choose a section of the family tree, ignoring a large chunk. Polyphyletic groups choose a few individuals throughout the tree without regard for common ancestors. In the family analogy, a paraphyletic group could include your mom and two of your siblings but not you. A polyphyletic group might include you and your cousin.
Phylogenetic trees are the most common tool used by biologists to depict evolutionary relationships. Generally the root of the tree is interpreted to be the oldest and the branches are the newest. Every branching point is called a node.
So far we’ve been looking at phylogenetic trees of your hypothetical family, but now that we have a primer in cladistics under our belts, we can start to look at a dinosaur phylogenetic tree.
The way to interpret this diagram is to think of time increasing as you read up. At the bottom there are the most recent common ancestor of all crocodiles, pterosaurs, and dinosaurs: Archosaurs. Just as with all of the other terms on this diagram, everything up from any given node belongs to the group labelled at the node. This means that all dinosaurs are archosaurs (but not all archosaurs are dinosaurs).
Archosaurs evolved in the late Permian or early Triassic period, about 250 million years ago. The most familiar archosaurs from that time are probably sail-backed beasts like Ctenosauriscus koeneni.
At the next node, you see ornithodirans, a word which refers to dinosaurs and pterosaurs. The interesting part to note here is that pterosaurs (like pterodactyls and Quetzalcoatlus) aren’t dinosaurs. They are the closest relatives to dinosaurs without actually being dinosaurs.
The next node on that diagram is the one we’ve been waiting for: Dinosaurs! As you can see, dinosaurs are a monophyletic group. If you want to refer to the dinosaurs that were wiped out by an asteroid 65 million years ago, you have to make a paraphyletic group and exclude birds. You can do this by saying “non-avian dinosaurs”. Let the pedantry begin!
As the diagram shows, the dinosaur lineage splits at this point and we find one of the most important features that helps scientists classify dinosaurs. It all comes down to the hip. One group, the ornithischians, have backwards-facing pubises in line with their ischia, while saurischians have down-and-forwards facing pubises at an angle to their ischia. This will become much clearer with some labelled images:
Once you know to look for it, this difference becomes glaringly obvious whenever you look at a dinosaur skeleton. Here, have a look at a few different images of dinosaurs and see if you can tell if its ornithischian or saurischian (I often just think of these as O– and S– because even when I say them in my head I trip over the -ischi-).
You are well on your way to being a dinosaur expert!
The last node we are going to discuss in the evolution of dinosaurs is the theropods. The word itself means beast feet and it is the last taxonomic word you can use to accurately describe both T-Rex and turkey. Theropods are a terrifying group of creatures, laying claim to speedy velociraptors, vicious ceratosaurs, and of course, the King, Tyrannosaurus Rex. They evolved fairly early on (~230 million years ago) and include most carnivorous dinosaurs and their descendants.
My favourite extinct dinosaur is Ankylosaurus magniventris, an armoured tank of a creature with a club-tail that definitely meant business. On the other hand, my favourite non-extinct dinosaur is probably Meleagris gallopavo, a colourful but mean-looking dino best served with potatoes and cranberry sauce.
I’ve never been a cat person, myself. They just seem a bit too contemptuous as a species.
Cats, aside from being aloof, clawed, and kind of mean, also form a necessary part in the life cycle of a single-celled protozoan called Toxoplasma gondii. This sneaky parasite can only reproduce in feline intestines but also finds its way into the tissues of pretty much all warm-blooded mammals. Its reach seems almost limitless and extends to more than half of the world’s bears, birds, cattle, cats, domestic chickens, deer, dogs, domestic geese, goats, mice, pigs, rabbits, rats, sea otters, sheep, and humans. And those are only the populations that were studied. Ever heard the expression that glitter is the herpes of the craft world because it gets everywhere? More accurately, glitter is the T. gondii of the craft world.
I call it sneaky because T. gondii has been shown to alter the behaviour of its rodent hosts in order to make it more likely to be ingested. The physical mechanism for this is still under investigation and largely unknown but there are two interesting experiments worth noting. The first found that rodents infected with T. gondii are more active and more excited about new places, making them more likely to be noticed (and eaten) by cats. The second purports that rodent brain chemistry is altered so that the unfortunate rats finds the scent of cat pee sexually attractive. The scientific paper which explains this second theory is even titled “Fatal attraction in rats infected with Toxoplasma gondii”.
So we’re pretty confident that T. gondii can alter the behaviour of rodents, but what does it do to humans?
We’re not sure…
For those with weak immune systems or for the pregnant, a T. gondii infection can cause acute toxoplasmosis, a potentially fatal disease characterised by swelling lymph nodes, sore muscles, and flu-like symptoms. I wouldn’t worry about that too much because it’s about as lethal as the flu for those with regular immune systems.
For the rest of us, infection with this parasite is largely asymptomatic. There’s no way to tell whether you’re infected or not without a blood test. Unless you ask Czech researcher Jaroslav Flegr. He, along with a growing number of scientists, believes there is enough evidence to show that latent toxoplasmosis makes humans more thrill-seeking. According to a 2012 paper in the Journal of Experimental Biology, infected individuals are more likely to get into traffic accidents, score differently on personality tests than un-infected individuals, and infected men are taller on average with more masculine facial features.
Rodent and human brains are not so different, it turns out.
If your cat got infected and you happened to get exposed while cleaning out its litter box, chances are that you are infected. Your cat’s poo is likely changing your personality. If, like me, you don’t and have never owned a cat, that doesn’t mean you’re safe from infection. T. gondii is really good at getting into your body and making its way to the central nervous system, where it acts the puppetmaster and, expecting you to be a rodent, makes you excited about new environments. All this so that you can be eaten and it can reproduce.
Ever wish you could see in the dark? It would make life a bit easier. No more tripping over clutter on the ground or feeling walls for a switch. Humans rely quite heavily on their sight, but some animals can make do by illuminating their surroundings with sound.
Bats are just such an animal. They belong to a privileged group of organisms including toothed whales (like sperm whales, dolphins, and killer whales) and shrews that use sound to see the world. By listening for the reflections of their high-frequency clicks, bats are able to build up an accurate picture of the world around them. The clicks are often too high for humans to hear, sometimes reaching as high as 110 kHz (human hearing generally goes from 20Hz-20kHz). This amazing superpower is called echolocation but not all bats have it. Most microbats (usually small, insect-eating, with proportionally large ears) can echolocate using their throat to produce clicks, while megabats (larger, fruit-eating, with large eyes) usually can’t. Like most rules in biology, though, these distinctions aren’t universal. Some megabats have evolved echolocation by way of specialized nose structures and others are smaller than big microbats.
So now that you’ve been acquainted with the notion of echolocation and the bat family tree, let’s start talking about some neat things that bats can do with their special ability.
Since echolocation is dependent on a bat receiving and interpreting the reflections of sound, it is particularly susceptible to interference. The biggest source of interference is the bat itself. Bats produce some of the loudest sounds in nature and have some of the most sensitive ears to register the reflections that come back hundreds of times quieter. Imagine revving up a Harley Davidson and putting a traffic cone on your ear to hear someone whispering across the room. It would probably hurt if you did those things at the same time. You’d be too rattled by the revving to be able to listen to the whisper. Bats avoid this by temporarily disconnecting their ears as they shriek, then quickly reconnecting them in time to hear the echo.
One particular species of bat, the Mexican free-tailed bat (Tadarida brasiliensis), has been recently observed messing with its competitors’ signals. By emitting a special signal right when another bat is about to catch an insect, the bats make each other miss. It’s the bat equivalent of yelling “PSYCH!” when someone is about to shoot a free-throw. Unlike the obnoxious friend though, the bat version actually works. The bats’ success rate drops by about 80%. It’s such an effective strategy that two bats will even hang out near each other, jamming each others’ signals every time one swoops in for a bug, until someone gives up.
The same species of bat that jams also lives in close proximity to natural gas fields in New Mexico. Some of the rigs have compressors that emit a constant, loud noise that can interfere with echolocation calls. For the Mexican free-tailed bats, whose normal calls fall within the same frequency range as the compressors, the loud wells are avoided when possible. The bats have also begun to change their calls, making them longer and in a more restricted range of frequencies. This strategy would make the calls more easily distinguishable from the background din and marks the first time human-made noise has been shown to interfere with bat life.
We know that humans can’t hear a lot of what the bats are “saying” when they are building up a sonar picture because our ears aren’t sensitive to the right frequencies. This makes sense because, for the vast majority of humans, it really doesn’t matter what the bats are saying. It’s a whole other issue if you’re a moth about to be eaten. There’s a lot of (evolutionary) pressure to hear the bats coming in order to avoid getting eaten. Some noctuids, a rather large family of moths, have evolved bat-sensing ears that warn the insect of impending disaster. If the bat is far enough away, the moth will make a break for it, otherwise it will just start flying erratically in random directions to try and make the bat miss. The Pallas long-tongue bat (Glossophaga soricina) still manages to get a meal by using only ultra-high-frequency, low intensity calls to find moths and by going silent on approach. This stealth mode doesn’t trip the moth’s defences.
For more information on echolocation and bats, check out: