The Function of Cheek Pouches

A possible ancestor of Diprotodon (the largest mammal known from anytime in Australia, as well as the largest known marsupial known from anywhere in the world, and a relative of the wombat), the skull of Euryzygoma dunense, another extinct, megafaunal, eight foot long, quadrupedal herbivorous marsupial, is quite interesting: it has two extended cheekbones.  This gives Euryzygoma the unusual mammalian property of its skull being wider than it is long.  Although to most this probably doesn’t actually seem all that exciting, the extended cheekbones have led to two interesting theories regarding their function in the living animal.  One we will look at in a few weeks (the week of August 3rd to be more precise), but the other one we will look at now.

The hypothesis came about when the skull of Euryzygoma was first described.  The scientists who first described Euryzygoma thought that the lateral extensions of the zygomatic arch resembled those seen in squirrels, gophers and various types of Old World Monkeys, like the macaque and the baboon. 

 In the living animals just described, these lateral extensions function as cheek pouches, which make it so that the animals that possess them can store food in them.  That is why you so often see a squirrel running around with its cheeks puffed out.   

Some scientists think that Euryzygoma might have used its cheek pouches to store water; thus, it would not need to spend so much time near waterholes that were most likely infested with large crocodiles.  This would also help Euryzygoma travel longer distances during a drought, enabling it to move greater distances to reach waterholes that other animals would simply unable to reach, having a much more limited range.

Propleopus, the Carnivorous Kangaroo

Imagine you are on a safari to the Masai Mara National Reserve in Kenya.  If you timed your visit right, then the Mara is inundated with wildebeest and zebra, as well as numerous other herbivores.  You will probably see a number of carnivores as well: cheetahs, leopards, lions, and especially hyenas.  What you probably don’t realize is that most places aren’t like this.  The Masai Mara has one of the highest predator populations seen in Africa, due in large to the great number of prey animals available for a meal.  Regardless, you are forced to acknowledge that there are a great many more prey animals than there are animals to prey upon them. 

                This is known as the predator/prey ratio, and it can be seen all over the world, and can also be seen in the past.  While hundreds, sometimes thousands, of fossils of a single herbivorous dinosaur can be discovered, it is far more rare to unearth the remains of a predatory dinosaur.  But why is there this unbalance between predators and their prey?  Well, let’s take a look at a continuous, cyclical event that takes place in a period of 9.6 years in the wilderness of Canada, that should be able to shed some light on the situation.

                At the beginning of the almost-ten year cycle, we see a sharp increase in the number of hares.  When food is plentiful, these hares often produce two to three litters of around 12 leverets (baby hare) each.  After their numbers reach their limit, their population density reaches around eight hare per football field.  At this time, the hares have eaten all of the edible material they can reach.  Not only are they out of food, but the plants that they feed upon begin to create bitter chemicals in their leaves and edible parts, that keep the hare from digesting the plant material very efficiently. 

                While the hare population is flourishing so, the hare’s predators find an especially easy time of it.  Owls, wolves, and foxes all flourish, but one predator does particularly well: the Canadian lynx.  Hares consist between 40 and 85 percent of the average lynx’s diet, and they generally kill two hares every three days.  With such an explosion in hare numbers, all of these predators flourish, successfully raising more owlets, kits, and cubs.  However, shortly after the plants begin to release the anti-digestion chemicals, the hare populations tank.  With not enough food, many of the animals die off.  Then, a year or two after the hare die-off, the lynx also experiences a massive fall in numbers.  With the lynx no longer over hunting the hare, and the predator/prey ratio returned to normal, the hare starts the cycle all over again. 

                While this cycle seems to be a healthy part of the Canadian ecosystem, in other places, a rapid rise in the number of predators or prey could be disastrous.  Therefore, nature has made it so that, in a healthy ecosystem, the prey animals vastly outnumber the predatory animals.  But how does all of this tie into kangaroos?  We will get back to that in a minute.  First, let’s take a look at an extinct, 26,000 year old relative of today’s rat kangaroo. 

                First described by Australian zoologist Charles De Vis around the turn of the century, the holotype of Propleopus at first remained unique.  It wasn’t until the year 1967 that more remains belonging to the genus Propleopus appeared.  More was discovered in the following years, but very few remains have been discovered even to this day.  With millions of fossilized mammalian bones discovered in Australia, Propleopus are “known from teeth and jaws attributable to less than 20 individuals.” 

                There are multiple reasons why an animal does not appear with a great amount of frequency in the fossil record.  Perhaps it is because the animal was small; smaller bones are much more delicate, and therefore less likely to survive the fossilization process.  (They are also a lot smaller, and therefore usually harder to find then, say the humerus of an Brachiosaurus!)  Perhaps the animal lived in an environment where fossilization is unlikely.  For example, in millions of years, when intelligent life again evolves on this planet, or we are visited by intelligent life from elsewhere in the galaxy, they would find very little or no evidence of mountainous animals, like bighorn sheep or the snow leopard.  This is because mountains are in a constant state of geologic flux.  At times they are being pushed up; but even when they are rising, they are already eroding.  Given enough time, entire mountain ranges can disappear, or almost disappear, like in the Australian Outback.  Sometimes, it is because paleontologists are simply looking in the wrong places, and there are treasure troves of these animals just waiting to be discovered elsewhere.  It could also be because the rocks where the animal was deposited simply don’t exist anymore, something that is called an unconformity in geologist’s terms.  Maybe the animal was just not very successful, and went extinct after only a short amount of time.  The fossilized animal could also represent a transitional fossil, so creatures with those characteristics would have only been around for a few thousand years.  Or, of course, it could be because the animal was a predator, and there were fewer individuals to begin with.

                Now you are probably thinking that this is quite a leap.  Just because this kangaroo didn’t appear all that often in the fossil record doesn’t necessarily mean that it was carnivorous.  And you are right, as if this was the only evidence of Propleopus being a carnivorous kangaroo, I would be laughed right out of the Neolithic Age: and they, at best, had only a very, very primitive form of language, and probably would, at best, barely understand what I was saying.  However, there is more evidence in favor of a carnivorous Propleopus.  As I am fond of saying, “the teeth tell the tale.” 

                Studies of the dentition of Propleopus show a close resemblance to small, extant insectivores or omnivores, i.e. the mountain pygmy possum and the musky rat kangaroo.  Where the teeth of Propleopus differ from the mountain pygmy possum and the musky rat kangaroo, however, the differences “could be interpreted as adaptations to meat-eating.”  To sum up, the incisors are short, stout, and appear great for stabbing, the premolars are strongly serrated, which is perfect for tearing into very tough stuff (perhaps tendon), and the molars are greatly reduced in size, as sometimes seen in the genus Wakaleo, one of the genera of marsupial lion, like Thylacoleo.  Furthermore, the molars, although reduced in size, share similar features to the largest extant marsupial carnivore today, the Tasmanian devil.  These features in the Tasmanian devil serve to keep bone splinters from penetrating the gums, and clearly would not be needed to serve that purpose in an herbivore. 

                The most revealing tale of the teeth can only be revealed by a microscope.  Studies have shown that, when you compare the microscopic wear patterns on the teeth of a herbivore and a carnivore, you can see obvious, and distinguishable, differences.  The teeth tell the tale of the diet of an animal, and help to show us what Propleopus might have eaten.  When compared with the wear patterns of closely related herbivores, like the musky rat kangaroo, and marsupial and placental carnivores, like the thylacine, Thylacoleo, and dogs, the wear patterns seen on Propleopus resembles that of the carnivores more so than that of the herbivores. 

                So was Propleopus a carnivore, or a herbivore, or both?  One hypothesis that has been put forward is that Propleopus was situated in a similar ecological niche as the modern day African baboon, eating whatever came it way, be it plants, eggs, insects, or meat.  Whatever the answer, is is doubtful that it could be answered now, and it is likely that only further research, and more discoveries, will ever hope to unravel the mystery surrounding Propleopus, the seemingly killer kangaroo.  

The Komodo Dragon: Deadly Drooler or Poisonous Predator?

The Komodo dragon (labeled "Vulnerable" by the IUCN) has long had the title of "World's Deadliest Drooler."  Native only to the Komodo Islands in Indonesia, The story went that the Komodo would bite its prey and let it slowly die, eaten away from the inside out by all of the deadly bacteria that fermented in its mouth.  It ends up that this story, as that is all it is, a story, originated from just one or two accounts of the creature almost a century or so ago, and that they were based almost entirely upon observation.  After these accounts were made public, more and more researchers and scientists tagged on to this idea until, eventually, it was a scientifically accepted fact.

Further support for this hypothesis was observations of Komodos biting buffalo, a main food source, and simply hanging around for days, weeks, and (I believe) on at least one occasion, a month.  Scientists believed that the animals would slowly succumb to the copious amounts of bacteria that were at home in the mouth of the worlds largest extant lizard. 

While it is true that the mouth of the Komodo dragon was, in fact, home to a number of very virulent strains of bacteria, it seems that there are other players at work.  A group of scientists noticed that the Komodo dragon, and other closely related monitor lizards, all had interesting bulges in the sides of their mouths.  These bulges they thought resembled those seen in the Gila monster, one of just two lizards that were previously known to have venom, the other being Mexico's beaded lizard.  Komodo skulls are hard to get a hold of, however, and it wasn't until 2009 that the team of researchers were finally able to get ahold of a Komodo dragon skull to put through an MRI machine.  The MRI scan showed that the Komodo did indeed have venom glands.  Although the venom appeared not to be deadly, it was potent enough to act as a sedative.  This, the team concluded, was how the Komodo would kill its victims: sedate them with its mildly potent venom, and then finish them off when they were slow and torporous. 

This didn't explain why it sometimes took weeks for Komodos to finish off a buffalo.  Kurt Schwenk believes it is because the Komodos often don't want to risk life and limb.  So what they do is they bite their victims, and let a combination of shock and bloodloss do the trick.  As the prey slowly starves, being surrounded by Komodo dragons and unable to retreat anywhere, more and more Komodos congregate in preparation of the coming feast.  And given their slow metabolic rates, they can afford to wait, too: unlike a lion or a cheetah, they are in no hurry to finish off their prey, and see no reason to take unnecessary risks to finish off the prey.

While all of this research is highly disputed, and subject to many different points of interpretation, it does seem like the idea of the Komodo killing by its toxic drool is indeed false, although only future research will decide all of this for certain.

Acrobatic Felines: The Caracal

(Almost) everybody loves cats!  Not only the domestic kitties, but wild cats too, like the speedy cheetah, the social lion, and the elusive snow leopard, among others.  But most people don't know that there are all sorts of different cats, and thirty-six generally accepted species of cats!  Many have numerous sub-species as well, the leopard having eight or nine all by itself.

Today, I am going to introduce you to one of my absolute favorite wild cats: the caracal, which is fortunately labeled "Least Concern" by the IUCN.  The caracal is found all over Africa, pretty much except in the rainforests and the deserts, as you can see in the map below.  The caracal is also found in various non-African countries, such as Israel, Iran, Arabia, Jordan, Pakistan, and India.

I am not going to do a lot of talking (which is not normal, believe me), as words can't really do justice to what this cat can do.  So just click the link below, and be amazed.  (I actually have never watched this video with the audio on, so I don't even know what he is saying, because I think that the audio would simply detract from the video.  Enjoy!)

http://www.youtube.com/watch?v=4dCXK6KhkTw

The Fauna of South Carolina: Reptiles and Amphibians

First off, don't forget to look below to see the answer to last weeks mystery animal, and to see a couple of pictures of this weeks!

Recently, my family visited some good friends of ours in South Carolina for a few weeks.  Not only did we have a lot of fun visiting them, we saw a lot of cool plants and animals there that we simply don't have up north!  For some of you, many of these animals and plants will be routine and boring, but hopefully there will be something in here that you will find interesting!  I think I am going to split this post up into at least a few different segments, with tomorrows post devoted entirely to the Black Skimmer, a very interesting bird that I had the good fortune to see hunt!  So today I am going to talk about some of the interesting reptiles and amphibians we saw down there, and over the next few weeks we can take a look at some of the birds, fossils and other things we saw down there!

Due to the increased heat and humidity, coupled with less of a swing between the seasons (i.e. it rarely snows and drops below freezing), the south is an excellent place to see all sorts of reptiles and amphibians.  We saw a number of turtles and a frog/toad or two when we were in the south, but what interested me more were the lizards.

A Carolina anole (Anolis carolinensis).  Despite its name, the Carolina anole is found in both South and North Carolina, as well as Florida, Georgia, Louisiana, Texas, Alabama and Mississippi.

A type of skink, but I have yet to ascertain its species, although I am almost certain its genus is that of Plestiodon

And then, of course, there's the gators.  The American Alligator lives in the same states as the Carolina anole, as well as Virginia, Arkansas and Oklahoma.  While we did see a few in the wild, all of these shots (except for that of the gator footprint) were taken at a place called Brookgreen Gardens, or at a restaurant called the Crab Shack.

This big gator we saw at Brookgreen Gardens

This is a picture of a gator footprint that I took.  You can see three of the toes very well, making it look a lot like a theropod dinosaur track, but you can see the other two toes as little holes in the ground.

This picture, and all the rest, were taken at an awesome (both food- and entertainment-wise) restaurant on Tybee Island in Georgia called The Crab Shack.

 

 

 

 

 

 This post is part of "The Fauna of South Carolina" series.  For the rest of the posts in this series, click HERE.

Sea Pines on Dwellable

What Is It? The Weekly Challenge #1 Answer

Well, it's that time of the week again!  We only had a few guesses this week, and no one got it exactly right, but there were some close guesses!  The two closest were Kristie C., who guessed an Adélie Penguin, and Masaki K. who guessed Cormorant.  Well, the correct answer to last weeks challenge is Waimanu.  Waimanu is the scientific name of the oldest known fossil penguin.  Two species are known, and both of them were found on the South Island of New Zealand.  One of the species, Waimanu manneringi, lived during the Paleocene, around 61.6 MYA; that means that the oldest known penguin was swimming the oceans only a few million years after the death of the dinosaurs!  Although Waimanu manneringi is the oldest KNOWN fossil penguin, it by no means is the oldest penguin.  In fact, it is quite likely that, were scientists to uncover a fossil that shows when penguins split off from the other orders of birds, we would not even recognize it as a penguin.  Waimanu had undoubtedly already adapted to a fully non-aerial lifestyle, and almost certainly behaved much like modern penguins do when it comes to breeding on land, near the ocean.


Works Cited:

Waimanu, the first penguin. (2010, January 30). Retrieved July 11, 2012, from https://fossilpenguins.wordpress.com/2010/01/30/waimanu-the-first-penguin/

Arthur the Aardvark

Almost everybody has heard of Arthur Read from the popular PBS show "Arthur."  What a lot of people don't realize is that Arthur is an aardvark.  And even more people don't usually even know what an aardvark is.

A fossorial (burrowing, like terrestrial or marine), nocturnal mammal from Africa, the aardvark is an insectivore, its favorite food being termites, and is labeled as "Least Concern" by the IUCN.  The aardvark, as you can see below, inhabits an incredibly large portion of Africa, including South Africa, Ethiopia, Kenya, Tanzania, Uganda, Mozambique, the Democratic Republic of the Congo (DRC), Burundi, Somalia, Angola, and many others.

The aardvark has several important adaptations for its burrowing, insectivorous life style.  Perhaps the most important are the large claws on its front limbs.  These claws enable the aardvark to not only dig out immense burrows for habitation use, but also to dig into termite mounds to extract a meal.  Interestingly, when the aardvark leaves its burrow to dig a new one, the old burrow is often taken up by the African wild dog, where the pups shelter until they are old enough to leave the protection of the burrow.

The aardvark also has thick skin, which keep the termites from biting it, allowing it to feast in relative peace.  A further adaptation to keep insects (as well as dust) out is in its nose: it can close its nose, preventing both bugs and dust from invading its breathing passages.  Finally, another very important insectivorous adaptation is the tongue of the aardvark.  The long, sticky tongue of the aardvark is usually about 12 inches long, equivalent to about one-sixth the length of the animal!  Long, sticky tongues are a fairly common adaptation for termite-eaters such as the numbat (Myrmecobius fasciatus), pangolins (Manis sp.), and the giant anteater (Myrmecophaga tridactyla) among them.

A southern tamandua (Tamandua tetradactyla) shows off its extraordinarily long tongue during an animal demonstration at one of Denver Zoo's teen career days.  Tamanduas are also insectivorous, and clearly also possess an amazing tongue.