Predators of Baby Leopards: You Might Be Surprised

One of my favorite TV shows is BBC's Big Cat Diary, which I believe I have already mentioned once or twice.  It has been called by critics as "The soap opera of the Serengeti," and has played for a number of seasons, under various other titles.  Essentially, the shows premise is a log of what two prides of lions (the Marsh and Ridge Prides) are doing, as well as my two favorites, the leopards and the cheetahs.

This is neither a leopard nor a cheetah, but a baboon skeleton.  It's probably poor planning on my part to not put a picture of what I've already talked about so far, but you're going to have to deal with it.  Or just pretend that's a cheetah, baboons and cheetahs are practically the same animal anyways.

In one episode I was recently watching, one of the co-hosts, Saba Douglas-Hamilton, said something that I thought was very interesting about leopard cubs.  She said that the top three animal threats to African leopards (besides humans, forcing the IUCN to label the African leopard as "Near Threatened,") are lions, hyenas....and baboons.  Check out the baboon skeleton (above) and mounted stuffed specimen from the American Museum of Natural History below!

I was actually completely kidding before, baboons and cheetahs are not really that closely related at all, and very few people have an excuse to confuse the two.

I knew baboons were an issue to leopards as one of the leopard stars of the earlier series, dubbed Half-Tail, was missing half her tail, hence her name.  The two hosts at the time, Jonathan Scott and Simon King, said that they thought the missing half of her tail was due to either a lion attack or, more likely, baboons.

Chilling like a villain: a leopard takes a break after staring out the window all day and stressing out about those stupid robins in that stupid birdbath.  Those robins better consider themselves lucky that there's glass between them, you mark my words.  Photo Credit: Ted and Gail Neher

I had never really thought about it before, but when I heard Saba mention it, I thought that was kind of strange.  Well, I looked up "baboon skulls" on Google Images, and I think I get it now; their canines can grow up to two inches long.  As a good comparison, the average lion typically possesses two inch long canines.  Now that is some serious dental hardware; I'm glad I'm not a baboon dentist!  (That, and I'm guessing that you don't get paid very much).

A baboon skull mounted at the American Museum of Natural History in New York City, New York.  Check out those nasty canines, they're frickin' huge!!

Baboons, like many primates (actually I believe all except for tarsiers), are omnivores, so theoretically they could use their canines to subdue and consume their prey.  However, it seems that male vs. male competition is the primary reason why baboons have such enormous canines.  Check out the "mandrill" webpage on the website for Bone Clones (for the lazy amongst you, HERE is a link), and you can see that the male has enormous teeth, while the female has a dentition that is much less impressive.  This seems to support the idea that baboons (at least the males) primarily use their teeth in interspecific intimidation, in order to frighten off other males and secure breeding rights to the females.

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The Cichlids of the African Rift Lakes

Three of the largest lakes in the world reside in the 3,700 mile long Rift Valleys of Africa.  These lakes, Lakes Victoria (located in the countries of Kenya, Uganda and Tanzania), Tanganyika (split between Burundi, the Democratic Republic of the Congo [DRC], Tanzania, and Zambia), and Malawi (located between Malawi, Mozambique and Tanzania), rank among the top ten largest lakes in the world; third, seventh, and ninth, respectively.  (For some reason, these rankings differ upon where you look.  Lake Victoria as the third largest lake seems pretty universal, but the ranks of Tanganyika and Malawi differ for whatever reason.  You'd think that it would be pretty universal, but I suppose not.)  Besides being such large lakes, these lakes are important for other reasons, perhaps the most important reason (for biologists, at least) being their isolation.

You see, the three great lakes are islands, of a sort.  According to Websters, the definition of an island is "a land mass smaller than a continent and surrounded by water."  The Rift Valley lakes are essentially the opposite; "a body of water smaller than an ocean and surrounded by land."  For our purposes, an island is just something that has been isolated for a time, and allowed its flora and fauna to flourish in new and interesting ways.

And flourish it did in the Rift Valley lakes.  If you were to visit these lakes, snorkel or scuba in their waters, you would most likely notice a wide variety of fish.  You would not be wrong in this assessment; however, you might be surprised to find that most of these types of fish are belonging to a group called the cichlids (SICK-lids), and that all 1,650 plus species of these cichlids descended from a common ancestor.  While the dates of when the common ancestor of the various cichlids came to be trapped in their respective lakes, it has been estimated that the cichlids of Lake Malawi all evolved from a common ancestor trapped 700,000 years ago, and those of Lake Victoria around 12,000 years ago.  Trapped in these growing lakes while they were being formed, this small group of fish quickly came to dominate their new home, exploding in biodiversity to adapt to the wide variety of niches left open to them.

Tenuous can this biodiversity be, as recent logger-based erosion has shown.  Logging nearby to one of the lakes resulted in rapid erosion.  This erosion caused a great deal of silt to build up in one of the lakes.  This, of course, caused the water to become quite murky; think about your average beach, and how murky the water often is near the shore.  Many of the cichlids that lived in this area relied upon visual identification to recognize members of the same species for mating purposes.  With the cloudy, muddled water, this became quite difficult.  As a result, many fish from closely related species ended up mating with each other and, in the case of many of the couplings, resulted in viable offspring.  These viable offspring in turn bred with other species, lowering, at least temporarily, the biodiversity of the cichlids in this particular corner of the lake.

Blantyre on Dwellable

Cloning the Cheetah: Why Bother?

In an attempt to discover why the cheetah has such a low fertility rate, a team of scientists, including David Wildt and Stephen O'Brien, decided to take a look at blood samples from a number of cheetahs, labeled "Vulnerable" by the IUCN.  What they found was startling, and very worrying; the cheetahs appeared to be dangerously, perilously inbred; they were all practically clones of each other. 

Wildt and O'Brien decided to confirm this hypothesis by taking skin samples from a number of cheetahs, and attempting to graft them onto a number of other cheetahs.  In a healthy population of animals, the skin grafts would be immediately rejected.  This is because the body of the animal who received the skin graft would recognize the skin to be from another individual, a foreign body, and attack it, just as it would attack any foreign body (i.e., germs or bacteria.)  Even in humans, skin grafts are often rejected, even ones from close relatives.

Normally a very majestic looking animal, this particular cheetah seems to have been caught at a bad time.  Photo Credit: Ted and Gail Neher

So when every single one of the cheetah skin grafts were accepted by the other animals, this did not bode well for the cheetah.  This meant the genetic diversity of the cheetah was incredibly, shockingly low.  But why is genetic diversity so important?  Well, without genetic diversity, the DNA of the individuals comprising a given population are very similar.  These individuals essentially become clones of each other, with many similar attributes, most important among them their immune systems.  In a healthy population of, say, cheetahs, say that fifty percent of them are immune to a certain disease, most of them evolving from a common ancestor.  The other fifty percent of the population has absolutely no protection against said disease, and the illness ravages their population.  An unfortunate (and oversimplified) event, to be sure, but fifty percent of the individuals remain to rebuild the population to what it once was.  With the low genetic diversity seen in the cheetah, if a similar disease in the hypothetical above sweeps through Africa, it is quite likely that a much lower percent than fifty would survive.  It is also possible that this disease would so ravage the global population of cheetahs that they would simply be unable to recover from this catastrophic event.

A cheetah scratching a log at the Denver Zoo.  The cheetahs incredibly slender build can help distinguish it from other cats. 

So why is the cheetah so catastrophically inbred?  Most of the time, low genetic diversity is due to a given species having passed through a "bottleneck."  20,000 years ago, cheetahs spanned the entire globe; ranging all over Europe, Asia and Africa, two species of cheetah, or "proto-cheetahs" if you will, even roamed North America (Miracinonyx inexpectatus and M. trumani.)  When the most recent Ice Age drew to a close around 10,000 years ago, the dramatic climatic changes (and likely human influences, as well) resulted in the extinction of much of the world's mammalian megafauna. Researchers think that this mass-extinction managed to knock the cheetah's numbers down to a very small population, likely comprising a mere handful of individuals.  (In fact, I remember reading once that at one time, some people thought that a single pregnant female mother was able to survive, but I don't think that this idea is all that highly regarded anymore).  While the cheetahs were obviously able to build their population numbers and density by a significant amount than that seen 10,000 years ago, this bottleneck came with a price; genetic diversity was, and is, miniscule.

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Smilodon Vs. Thylacosmilus: The Saber-Toothed Marsupial

Two million years ago, a saber-toothed predator stalked the landscape of South America.  Possessed with long, dagger-like teeth, Thylacosmilus was undoubtedly a terrifying predator of the plains of Patagonia.  This saber-toothed predator would have given even the saber-toothed cats pause, despite the fact that (to paraphrase Obi-Wan Kenobi), "He's more kangaroo now than cat."  Despite superficial similarities, Thylacosmilus was not a saber-toothed cat.  Instead, it was a six foot long, 500 pound saber-toothed marsupial.

A reconstruction of Thylacosmilus by the talented young artist Sam Lippincott.  Interestingly, the super-sized canines of Thylacosmilus grew continually throughout its life, unlike those of Smilodon or Xenosmilus (see below), two of the actual saber-toothed cats.  Photo Credit: Sam Lippincott

The immense canines possessed by Thylacosmilus had previously evolved in both the cat-like Nimravids and the various saber-toothed cats (amongst others), and is a classic example of convergent evolution, a topic, in my opinion, that is one of the most interesting happenstances in nature.  We will hopefully talk about convergent evolution sometime next week.

A mounted skeleton of Xenosmilus, a type of saber-toothed feline, at the Mace Brown Museum of Natural History at the College of Charleston in South Carolina.  I got to visit here in July of 2014, and it was a very nice little museum.  Compare the skull of Xenosmilus with that of Thylacosmilus (below).

Anyways, Thylacosmilus lived during the Miocene and the Pliocene Epochs, from 10-2 MYA.  Up until 2 MYA, South America had been its own, separate land mass, not connected to any other continents since some time during the Cretaceous.  2 MYA, however, something extraordinary happened: the Isthmus of Panama was formed, connecting the two continents.  With this connection, came something scientists have dubbed the "Great American Interchange."  Animals from both continents could move, and spread out into the other continents.  For some creatures, like the saber-toothed cats, this was a good thing; they moved down into South America from North America and dominated the landscape.  For other predators, like the terror-bird Titanis(again, a topic for another time), it was good, for a while; after moving into the southern part of North America, however, Titanis was outcompeted by other predators.  For Thylacosmilus, it was down-right disastrous.  Shortly after the Great American Interchange, fossil evidence of Thylacosmilus entirely disappears, similar to the competition between the dingo and the thylacine that drove the thylacine to extinction on mainland Australia.

The skull of Thylacosmilus on display at the American Museum of Natural History in New York.  Got to see this sucker in person in August 2014, when I visited with my good buddy Zach Evens! 

This is a partial post for the "Convergent Evolution" series.  That means that this post is partially included, but was not made specifically to be a part of that series.  HERE is a link to the Homebase for this series.  

The Biggest Carnivorous Dinosaur Part 3: Spinosaurus, The World's Largest Penguin

Spinosaurus quickly smashed its way to the top (literally!) following the success of Jurassic Park III.  At up to 56 feet (17 meters) in length, Spinosaurus (found in Egypt and Morocco) is unquestionably the longest carnivorous dinosaur that has ever been discovered, and by a significant margin, too.  But how could Spinosaurus be so successful when another carnivorous monstrosity, Carcharodontosaurus, lived in such close proximity?  The answer lies in what it ate; in fact, Spinosaurus appears not to have been as carnivorous as we once thought, and seems to in fact have been more piscivorous.  Essentially, it is thought that Spinosaurus might have survived on a diet consisting a great deal upon fish.

There is a great wealth of information that indicates the staple diet of Spinosaurus was fish.  Here we will take a more in-depth look at this evidence.

A picture of Spinosaurus drawn by the talented young artist Sam Lippincott.

1.  POSITION OF THE NOSTRILS:  Spinosaurus, unlike most other theropod (meat-eating) dinosaurs had nostrils situated very high up on its skull.  By contrast, most other theropods, like Tyrannosaurus, had nostrils very close to the front of the skull.  The nostril placement in Spinosaurus would have allowed it to stick its nose into the water quite deep, enabling it to hunt fish more effectively.

2.  SENSORY ORGANS ON THE TIP OF THE SNOUT:  Along with the high placement of the nostrils, Spinosaurus also had a number of small sensory organs at the front of the snout, revealed by CT scans.  These greatly resemble those of the crocodile, who uses them to sense where prey is by "seeing" tiny movements in the water.  Thus, a crocodile can attack its prey without ever seeing them with their eyes.  Spinosaurus appears to have been able to do much the same thing, making its hunting method of choice quite obviously effective, given its immense size.

3.  ISOTOPIC EVIDENCE:  A study of the isotopes in the skull of a Spinosaurus specimen revealed something quite interesting.  Spinosaurus shares a great deal of isotopic overlap with crocodiles, fairly aquatic animals.  By contrast, other carnivorous dinosaurs like Tyrannosaurus have very different isotopic readings, indicating a terrestrial lifestyle.  Given the great deal of overlap possessed by Spinosaurus and crocodiles, it appears that Spinosaurus spent much of its life like a crocodile; semi-submerged in rivers and streams.

4.  THE TEETH TELL THE TALE:  Spinosaurus, unlike most other carnivorous dinosaurs like Tyrannosaurus, Allosaurus, or the famous Velociraptor, possess conical, round teeth.  These other carnivores possess thin, blade-like teeth, made for slicing, crushing or tearing into other animals.  Spinosaurus has teeth much like a crocodile; round and conical.  These teeth are made for gripping and making sure that an animal does not escape. 

5.  THE TEETH TELL THE TALE....AGAIN:  Yet again, we come to the issue of teeth, and this is one of the most damning pieces of evidence of all.  During the time that Spinosaurus lived in North Africa, another inhabitant of these streams and rivers was a saw-toothed fish called Onchopristis.  Two fossils involving Onchopristis have been discovered in conjunction with the remains of Spinosaurus.  One was the skull of a Spinosaurus; imbedded in one of the tooth sockets was a vertebrae from an Onchopristis.  The other discovery was the barb of an Onchopristis embedded in the jaw of the Spinosaurus.

6.  PLUS:  We only ever seem to find Spinosaurus in shallow aquatic environments, where fishy prey would be abundant.

All in all, it seems like an inevitable conclusion to draw that Spinosaurus was, in fact, a piscivore, at least much of the time.  A fascinating example of the crazy turns evolution can take.

The Biggest Carnivorous Dinosaur Part 2: Carcharodontosaurus Vs. Spinosaurus

As I promised yesterday, today we are going to take a closer look at Carcharodontosaurus (kar-kar-o-DON-to-SAUR-us).  Carcharodontosaurus was a relative of Colorado's own Allosaurus.  However, Carcharodontosaurus was four times larger, and found in Egypt, Morocco, Algeria, Libya, and Niger.  At around 46 feet long, Carcharodontosaurus was similar in size to yesterday's Giganotosaurus (pronounced jig-a-NOTE-o-saur-us), and longer than Tyrannosaurus, though Tyrannosaurus was undoubtedly much bulkier.  Regardless, Carcharodontosaurus was a monster-sized killer, and almost certainly had a monster-sized appetite to match.  It is almost a certainty that such an animal would have a fairly large territory, and would have needed to eat a great deal to maintain its fast metabolism, similar to your average teenage dude.

Clearly, such a large predator had little competition from other carnivorous dinosaurs.  Or did it?  As a matter of fact, 95 MYA, North Africa was home to not one, but two monster-sized killers, Carcharodontosaurus, and the even longer, 50 foot (15 meter) Spinosaurus.  (Some not so conservative estimates even place the maximum size for Spinosaurus as 60 feet (18 meters) in length, but this does seem extreme.)

Now, in the modern day, predators can inhabit the same area.  Take the plains of Africa, for example; in many places, lions, leopards, cheetahs, wild dogs and hyenas all inhabit the same area.  There is a clear hierarchy amongst the animals, and each seems to get enough to eat.  However, this is partly because each animal exploits a slightly different set of resources, so contact amongst them is less frequent than if all five of the large carnivores all hunted the same animal, say, the Thomson's Gazelle.  This is a phenomenon known as resource partitioning, and it occurs all over the place in nature, arguably one of the most important factors involving ecology and evolution. Scientists believe that a similar sort of partitioning took place between the two mega-carnivores of Mid-Cretaceous North Africa, with Carcharodontosaurus being a terrestrial carnivore, while Spinosaurus took to the water.  We will conclude "The Biggest Carnivorous Dinosaur" trilogy tomorrow with a look at the environment Spinosaurus was able to so successfully exploit.

A fantastic visual representation of resource partitioning amongst large herbivorous mammals in Africa.  The giraffe, the zebra, and the wildebeest will all inhabit the same area and eat plants, but the types of plants can differ.  Photo Credit: Ted and Gail Neher

The Biggest Carnivorous Dinosaur Part 1: Move Over, T-Rex (Kind Of)

Tyrannosaurus rex, the "Tyrant Lizard King," has long been a dinosaurian favorite the world over.  He is quite the interesting animal, and simply massive; the publicity received by him and the giant-sized Velociraptor in Jurassic Park helped a bit, I'm sure!  However, T-rex is no longer thought to be the largest carnivorous dinosaur.  Well, yes he is.  But he isn't.

A picture of the Tyrannosaurus rex specimen Stan at the Morrison Natural History Museum.

Imagine someone who has never heard of the giraffe and elephant asks you which one is biggest.  You might say the elephant, because the elephant is much heavier and has more bulk.  But what if they mean which animal is taller?  Somewhat of a dilemma.  So using words like "biggest" (as I have done here) is not the best way to go.  So Tyrannosaurus still seems to be the heavyweight champion, there are other dinosaurs that, while more slender, were probably longer.  Kind of confusing, I know.

The fact that T-rex has some serious competition has put barely a dent into his popularity, and some of the other larger carnivores are receiving a lot of attention, too. The longest of these carnivores, which we will learn about on Wednesday, was possibly around 20% larger than Tyrannosaurus Rex!  Today, we are going to look at another enormous killer, of South American origin; the massive, the monstrous, Giganotosaurus.

A Giganotosaurus on display at Fernbank Museum, in Atlanta, Georgia

Giganotosaurus is an estimated 46 feet long, comparable in length to the average Tyrannosaurus!  We do have some specimens of Tyrannosaurus that are around the same size as Giganotosaurus, but either way: Giganotosaurus was a massive animal! Of course we don't actually know for sure what the maximum size for any dinosaur is as, unlike for most living animals, we generally have a relatively small sample set, but we can make close estimates based on the finds we have.  And these estimates indicate that Giganotosaurus grew to simply massive proportions.  One of the largest terrestrial animals that we know of is Argentinosaurus (who, like Giganotosaurus, was also found in Argentina), a sauropod dinosaur that lived at the same time as Giganotosaurus.  For Giganotosaurus to prey on even the juveniles of such a large herbivore, it would similarly need to grow to massive proportions.

Giganotosaurus vs. Argentinosaurus at Fernbank Museum, in Atlanta, Georgia

Giganotosaurus vs. Argentinosaurus at Fernbank Museum, in Atlanta, Georgia

This pattern repeats itself all over the world, the pattern of gigantism evolving in sauropods, along with the subsequent evolution of gigantism in the theropods (meat-eating dinosaurs), is a pattern repeated throughout the world, and throughout the Jurassic and Cretaceous Periods of the Mesozoic Era, the two periods in time when the rule of the dinosaurs was absolute.  Here are some more of the predator-prey, giant-sized carnivore/giant-sized herbivore relationships seen throughout the Mesozoic.  The first animal named will be the predator, and the second will be the sauropod.

Asia, 160 MYA: Sinraptor, Mamenchisaurus
Europe, 125 MYA: Neovenator, Ornithopsis
North America, 150 MYA: Allosaurus, Diplodocus
North Africa, 95 MYA: Carcharodontosaurus, Paralititan

In tomorrows post, we will look at the last relationship, and focus on another larger (or longer) than life carnivore, Carcharodontosaurus.