Monday, March 30, 2015

When Crackers Won't Cut It: Carnivory in Parrots

Animals do surprising things, and this should come as no surprise. After all, they are more than just entries in field guides; they are living beings and individuals which react different to a variety of unique situations. Most animals are both intelligent and intuitive, and will change their behavior to better survive an unlikely situation, or take advantage of situations which they find favorable.

As evolution is driven at its core by the need to gain resources for survival and reproduce, it makes sense that many surprising behaviors are related to food and sex. I’d like to address the former rather than the latter, and you can busy yourselves by searching for articles on the subject. Trust me, there’s enough material on strange animal sex to give you nightmares.

Sometimes, animals eat things that we don’t expect them to. Lions, jaguars, and other large carnivores will readily eat fruit when preferred prey is limited. Seals and walruses will chow down on seabirds when on land. Deer and cattle have been seen time and time again chewing on bones and eating young birds to gain essential calcium in their diets. But perhaps one of the most intriguing cases of bizarre gastronomy in animals is the fact that some parrots will eat meat when given the chance.

Granted, this is uncommon, but this is the norm for unexpected behavior. As far as observed instances of carnivory in parrots, I believe that only two species have been readily seen eating other animals/animal products: the kea Nestor notabilis and, just recently, the rainbow lorikeet Trichoglossus moluccanus.

Kea: Scourge of the Kiwi ski slopes
The kea is a weird parrot to begin with - it lives in New Zealand (already a sure-fire sign that it is a strange bird), specifically in the chilly alpine regions of the country, where it can be seen engaging in play behavior such as rolling in the snow and destroying your car. They are also really smart, even for parrots: in the wild and captivity, they have been able to solve manmade puzzles in order to get treats (non-meat, I presume).

A kea, happily removing your windshield wiper for its own amusement. They regularly dismantle manmade objects found in their environment, including cars, tents, and backpacks.

So what does an alpine, cold-weather parrot eat? Like most parrots, most of its diet consists of vegetation, with a few invertebrates thrown in. However, it is also an active predator. In addition to rabbits (don’t feel bad, they’re an exotic invasive in New Zealand and deserve it), kea will also infiltrate the nest burrows of shearwaters and drag out their fat, unfledged chicks. I’d just like to state, at this point, that if you’re still doubting that birds are dinosaurs, it’s not too late to change your mind.

Perhaps the most long-winded and interesting debate over the diet of the kea is whether or not it preys upon sheep. Sheep, as you know, account for most of New Zealand’s population. There have been observations of kea landing on sheep and ripping into their flesh. Yes, really. There’s even an old photo of a sheep supposedly killed by kea, showing tufts of wool around the carcass where the birds attacked. Knowing the kea’s track record for being the most metal and un-parrot-y parrot, I would not be surprised if these sheep attacks are more common than we realize.

Rainbow Lorikeet: The true sparkleraptor
Appparently, at least one person in Australia leaves out meat for endemic carnivorous birds to come and eat. Besides being the most awesome bird feeding system ever, the offerings attract kookaburra and currawongs. But recently, a new bird has taken a liking to the meat, and has even began chasing others away.

Behold the face of a true monster.

A pair of rainbow lorikeets chowing down at the
meat-filled bird feeder in question. Photograph taken by Matt Watson.
Now, I’m still trying to wrap my head around this one, honestly. Lorikeets are largely nectar-eaters, occasionally taking fruit and nuts as well. Some zoos have feeding stations for them, allowing you to walk among them with cups of simulated nectar, which they will swarm around. I think next time I go to one, I’m going to bring a pork chop instead.

What could lorikeets possibly want to do with meat? Why this sudden change in appetite? It’s likely that the meat contains essential vitamins and proteins which are beneficial to the parrots. However, perhaps it is just a matter of preference - in the yard in which this occurred, native flowering and fruiting trees were even more abundant than the meat scraps left out at the feeders. Even if this is an isolated case, I am curious to see what ornithologists make of it - continued observation of this bizarre instance is needed in order to better understand it.

I often like to think of parrots as the primates of the bird world in terms of their social behavior, feeding habits, and adaptability. And, just like chimpanzees, it seems that particular species have a fondness for something other than the usual fruit or nut. Just keep an eye out the next time Polly starts eyeing the family cat.

Thursday, March 26, 2015

Triassic Thursday IV: Giant temnospondyls

By both diversity and popular opinion, reptiles ruled the Triassic. I’ve said it again and again on this blog and I’m sure you’re sick of it. So how about we change things up and talk about big gregarious flat-headed amphibians?

Before I begin, let me clear something up about what we like to call “amphibians.” You mention the word to most people and they will get the general idea of what an amphibian is: a frog or a salamander, for example; something that has moist skin and likes to swim around and lay little squishy eggs. Based on this diagnosis, lots of extinct critters fall into the category of amphibians. The animals I am about to discuss, however, are not the same as the amphibians we’re familiar with. Rather, they are labyrhinthodonts, specifically temnospondyls: members of an extinct clade of large, often crocodile-like amphibians which were among the dominant semi-aquatic predators from the Carboniferous to the early Jurassic. My point, I suppose, is that it is taxonomically incorrect to refer to these big guys as amphibians per se, but they aren’t far off and I won’t judge you for referring to them as such. Whether or not they would take offense remains to be seen.

Across the floodplains of Late Triassic Pangaea, which was slowly drifting apart, huge vernal pools and ponds were home to groups of these large temnospondyls. Metoposaurs and mastodonsauroids were the biggest in the Triassic, growing to a couple of meters long. They also have some ridiculous-looking skulls. The first time I heard someone refer to metoposaurs as “toilet seat-headed,” I was surprised I hadn’t thought of it myself. The resemblance is uncanny. 

Metoposaurus bakeri, a toilet-headed temnospondyl. Reconstruction by DiBgd, from Wikipedia.

These giant toilet-headed beasties probably ate whatever they could fit into their big mouths. Fish were probably key menu items; however, with eyes located dorsally on their skulls and an overall dorsoventrally compressed bodyplan, it was likely that they could ambush riparian animals as well. Living in a time of phytosaurs, rauisuchians, and dinosaurs, I’m sure that temnospondyls were much more often the prey of reptiles than the other way around.

Some of the best-preserved metoposaurs come from mass bone beds. For a while, it was thought that these animals had gathered together during a drought, congregating in rapidly-dissipating pools which were essential for their survival. However, taphonomy of these bone beds suggests that, while they were likely in close association when alive, they were probably carried from other locations rather than being preserved in a single pool. Perhaps these metoposaurs lived as crocodiles do in resource-abundant areas, passively gathering together when times were plentiful. Or, some suggest, they could have gathered to spawn, which would have been an awesome spectacle: imagine a vernal pool on a Pangaea floodplain full of dozens of writhing, spawning, two-meter temnospondyls depositing tens of thousands of eggs. Beautiful. And gross.

Thursday, March 19, 2015

Triassic Thursday III: Carnufex

Fresh off the presses of the Internet, and just in time for a new Triassic Thursday, comes a brand-new crocodylomorph predator from the Late Triassic of North Carolina. On the heels of the armored-necked aetosaur Gorgetosuchus, which hails from the same area, we are graced with Carnufex carolinensis. It was one of the first crocodylomorphs to reach the status of apex predator in this Triassic ecosystem.

The skull of Carnufex. With a long, pointed head, it was very different
from most large predators of the Triassic. From Zanno et al., 2015.

One look at the skull of Carnufex, and you realize that this was not typical of Late Triassic ecosystems: its skull was slender and long, and looks for all the world like the skull of a theropod. It was likely a gracile and slender animal, rather unlike what we see in the majority of crocodylomorphs. Its lightweight frame and long limbs gave it an advantage of agility and speed during a time when most reptiles, barring crocodylomorphs and dinosaurs, were amblers or lumberers.

While I have previously written about the success of pseudosuchians and other crocodile-line archosaurs during the Triassic, Carnufex was truly something exceptional: it is currently the oldest-known crocodylomorph, more closely related to true crocodiles than to rauisuchians and their ilk. As such, it was something novel on the landscape of the Triassic: it was likely more slender and adaptable than other large reptiles of the time. It was the forebear of an age which was as much dominated by crocodylomorphs as it was by dinosaurs.

I highly recommend checking out Zanno et. al's paper (which can be found here). The discovery of Carnufex is a significant one for understanding the evolution of crocodylomorphs, and how they were able to diversify rapidly at the end of the Triassic following the extinction of other lines of pseudosuchians. 

Thursday, March 12, 2015

Triassic Thursday II: Aetosaurs

Aetosaurs, of the family Stagonolepididae, were prominent herbivores during the mid- to Late Triassic. I love aetosaurs: their snouts and prominent body armor made them the ecological equivalent of warthogs covered in spikes. They were a globally-dispersed species, with specimens being found in the Americas, Europe, Asia, and Africa. Before low-browsing dinosaurs evolved, these guys were the herbivorous powerhouses.

The main difference between aetosaur species is the arrangement and shape of body armor. However, most species contain an armadillo-like covering of osteoderms, protecting their neck, back, tail, and stomach from large predators such as the dino-mimicking rauisuchians with which they shared their environment. The most extensively-covered and elaborately-adorned aetosaur of them all was, without a doubt, Desmatosuchus, which I think bears an uncanny resemblance to the nodosaur Sauropelta. Clearly, the big shoulder spine look was not a fad limited to the Triassic.

The spike-shouldered aetosaur Desmatosuchus. Reconstruction by Dr. Jeff Martz.

Most other aetosaurs were not as well-equipped as Desmatosuchus. Most had parallel rows of TV remote-shaped scutes running down their backs. Still, this thick armor was enough to deter some of the biggest predators of the Triassic.

There is some evidence out there that aetosaurs constructed nests. Simple bowl-shaped depressions in the ground found in Arizona may belong to motherly aetosaurs. Archosaurs in general are known for parental care and nest construction, so the fact that these large nests may belong to aetosaurs is entirely within the realm of possibility.

Material from the new aetosaur Gorgetosuchus (Heckert et. al 2015).

Aetosaurs are particularly topical because a brand new species was just identified from North Carolina. Dubbed Gorgetosuchus, it had a ring of osteoderms surrounding its neck, like a huge bony collar. Despite being heavily-armored and generally of the same body shape, the diversity of aetosaurs in the mid- to Late Triassic is pretty incredible considering that the earth was still in recovery. The Triassic was a time of great proliferation, especially of reptiles.

Thursday, March 5, 2015

Triassic Thursday I: An Introduction, and Coelophysis

Because I’m pleased as punch to be making progress on my microfossil research, I hereby declare that, henceforth, Thursdays shall be Triassic Thursdays!

The Triassic period was one of the most bizarre periods in Earth’s history. The world was recovering from the most catastrophic mass extinction which has ever occurred: at the end of the Permian, over 90% of the planet’s species had gone extinct due mass volcanism which was covering basically all of Russia. A strange cast of characters, most of them synapsid amniotes, disappeared in this cataclysm. But the tragic end of the Paleozoic Era was the glorious dawn of a planet dominated by reptiles: the Mesozoic.

The Triassic was just plain awesome, and the fossils prove it. With the planet essentially a giant blank slate, evolution let loose the reigns of predictability and spun a ridiculous world of diapsids. The beginnings of all modern groups of reptiles can all be found in the mid-late Triassic: lizards, turtles, crocodiles, and dinosaurs all had their roots during this time, as well as other reptiles which have left no living descendants, including sauropterygians (ichthyosaurs and their kin), placodonts (which I have previously written about), and pterosaurs, the first flying vertebrates. Also thrown into the mix are reptiles which still puzzle us with their bizarre anatomy: monkey-lizards and their leaf-mimicking relatives, creatures with necks twice the length of their entire bodies, and dragon-like reptilian otters have all been discovered in Triassic localities, and are still contested over where they belong among other reptiles.

How awesome was the Triassic? This awesome. A couple of pseudosuchians (an aetosaur on left and a rauisuchian on right) square off. You can see a small theropod dinosaur in the background, biding his time before his kind throws the largest biological coup in history. Illustration by Julius Csotonyi.

This is why I am happy to be conducting research on the Triassic. I’ve been a paleo-nerd for my entire life, and anyone with a passion for paleo knows how cool the Triassic is. Not everyone agrees that it is the best (but we won’t judge them for that), but in terms of biological and evolutionary significance, it’s easily in the Top 5.

So, what exactly am I doing? Why, I’m glad you asked! So thoughtful, you.

Over the past year, I have been looking through what appears to be dirt and gravel in search of microfossils. These are 1-2mm size chunks and fragments of bone, teeth, scales, and whatever else happens to be fossilized. And there are lots of them! While a sizable chunk of matrix might only contain a couple dozen vertebrate microfossils, it is a challenge to properly identify them, just because of the condition they’re in. Trust me, when all you have of a small animal is a small chunk of a small bone, it gets tricky. But therein lies the fun!

My ultimate goal is to identify specimens of juvenile archosaurs (that is, dinosaurs and crocodylomorphs, which I have also written about) from the samples I and others have collected, and to identify characteristics of these fossils which can be used to identify other juvenile archosaurs from other places and periods. These samples, which are professionally stored in gallon plastic bags, hail from the Hayden Quarry of the Ghost Ranch locality in Abiquiu, New Mexico, which I had the pleasure of visiting and the honor of working with a group of Triassic paleontologists from around the country. 

It’s a bit ambitious, I’ll give you that. A grant reviewer even called this effort too much for a “questionable gain in knowledge.” But hey, I won’t complain. I’ve always wanted to conduct paleontological research and I’m really enjoying it. Plus, I’ve already found some fossils which may fit the criteria I’m looking for. 

Well, now that you know a bit about why I love the Triassic and why I so enjoy this project, let me introduce this week’s Triassic beastie.

Coelophysis bauri

A Coelophysis family about to chow down on an unfortunate drepanosaur. Illustration by Asparavis, from deviantArt.

Coelophysis is one of the best-known dinosaurs, largely due to the enormous quantity of specimens that have been recovered from the American southwest. Hundreds of individuals are known from several quarries in New Mexico and Arizona, and range in age from juveniles to adults. Such abundance is really awesome for paleontologists, as it is so rare to have even one individual of one species preserve in the fossil record. Coelophysis provides a unique opportunity for studies of ontogeny, or growth, from a young to mature animal. 

Like most dinosaurs of its day, Coelophysis was no heavyweight. Only a couple of meters long, it was dwarfed by an array of crocodile-line predators. However, its descendants were some of the largest predators of the Early Jurassic, soon after the crocodilian competition had gone extinct at the end of the Triassic. It probably hunted insects and small reptiles. In fact, it is one of the dinosaurs known to be preserved with stomach contents. 

Coelophysis stomach contents (in yellow). From Nesbitt et al. 2006.

It was thought for a while that this Coelophysis was a cannibal which had eaten a younger member of its species. However, it was found that the bones preserved in this guy’s torso did not belong to Coelophysis, but an early crocodylomorph. 

Coelophysis was a gracile animal with birdlike bones, a trait which is reflected in its name, which means “hollow form.” It is a classic example of the anatomical advantages that dinosaurs had over most other reptiles of the Triassic: legs held directly below the body, bipedal locomotion which freed up the hands for manipulating prey, and a long tail for anchoring leg muscles. While it wasn’t the first dinosaur, it is a good example of the general role of dinosaurs during a time when they weren’t dominant.

Oh, and Coelophysis was the second dinosaur to go to space. Don’t ask me why. 

Thanks for hanging with me, everyone. I know I haven’t written in a long while, but I do appreciate the views and support you give me. Stick around for more updates!