Tag Archives: crocodile

Saltwater Crocodiles: the world’s oldest and largest reptile

From the east of India, all through to the north of Australia, one fearsome, cold-blooded predator stalks the coasts. This hypercarnivore will contend with any that enters its watery domain, from birds to men to sharks, and almost always win that fight. Fossil evidence shows that this species has been plying its bloody trade for almost 5 million years, remaining virtually unchanged, a testament to just how efficient a killing machine it is. Looking it in the eye is the closest thing we have to staring down a carnivorous dinosaur.

Saltwater crocodile at the Australia Zoo, Beerwah, South Queensland. Image credits Bernard Dupont / Flickr.

This animal is the saltwater crocodile (Crocodylus porosus). It has the distinction of being the single largest reptile alive on the planet today, and one of the oldest species to still walk the Earth.

Predatory legacy

The earliest fossil evidence we have of this species dates back to the Pliocene Epoch, which spanned from 5.3 million to 2.6 million years ago.

But the crocodile family is much older. They draw their roots in the Mesozoic Era, some 250 million years ago, when they branched off of archosaurs (the common ancestor they share with modern birds). During those early days, they lived alongside dinosaurs.

Crocodiles began truly coming into their own some 55 million years ago, evolving into their own species in the shape we know them today. They have remained almost unchanged since, a testament to how well-adapted they are to their environments, and the sheer efficiency with which they hunt.

This makes the crocodile family, and the saltwater crocodile as one of its members, one of the oldest lineages alive on the planet today.

The saltwater crocodile

With adult males reaching up to 6 or 7 meters (around 20 to 23 ft) in length, this species is the largest reptile alive today. Females are smaller than males, generally not exceeding 3 meters in length (10 ft); 2.5 meters is considered large for these ladies.

Image credits fvanrenterghem / Flickr.

The saltwater crocodile will grow up to its maximum size and then start increasing in bulk. The weight of these animals generally increases cubically (by a power of 3) as they age; an individual at 6 m long will weigh over twice as much as one at 5 m. All in all, they tend to be noticeably broader and more heavy-set than other crocodiles.

That being said, they are quite small as juveniles. Freshly-hatched crocs measure about 28 cm (11 in) in length and weigh an average of only 71 g — less than an average bag of chips.

Saltwater crocodiles have large heads, with a surprisingly wide snout compared to other species of croc. Their snout is usually twice as long overall as they are wide at the base. A pair of ridges adorn the animal’s eyes, running down the middle of their snout to the nose. Between 64 and 68 teeth line their powerful jaws.

Like their relatives, saltwater crocodiles are covered in scales. These are oval in shape. They tend to be smaller than the scales of other crocodiles and the species has small or completely absent scutes (larger, bony plates that reinforce certain areas of the animal’s armored cover) on their necks, which can serve as a quick identifier for the species.

Young individuals are pale yellow, which changes with age. Adults are a darker yellow with tan and gray spots and a white or yellow belly. Adults also have stripes on the lower sides of their bodies and dark bands on their tails.

That being said, several color variations are known to exist in the wild; some adults can maintain a pale coloration throughout their lives, while others can develop quite dark coats, almost black.

Behavior, feeding, mating

Saltwater crocodiles are ambush predators. They lie in wait just below the waterline, with only their raised brows and nostrils poking above the water. These reptiles capture unsuspecting prey from the shore as they come to drink, but are not shy to more actively hunt prey in the water, either. Their infamous ‘death roll’ — where they bite and then twist their unfortunate victim — is devastating, as is their habit of pulling animals into the water where they drown. But even their bite alone is terrifying. According to an analysis by Florida State University paleobiologist Gregory M. Erickson, saltwater crocodiles have the strongest bite of all their relatives, clocking in at 3,700 pounds per square inch (psi).

That’s a mighty bitey. Image credits Sankara Subramanian / Flickr.

Apart from being the largest, the saltwater crocodile is also considered one of the most intelligent reptiles, showing sophisticated behavior. They have a relatively wide repertoire of sounds with which they communicate. They produce bark-like sounds in four known types of calls. The first, which is only performed by newborns, is a short, high-toned hatching call. Another is their distress call, typically only seen in juveniles, which is a series of short, high-pitched barks. The species also has a threat call — a hissing or coughing sound made toward an intruder — and a courtship call, which is a long and low growl.

Saltwater crocodiles will spend most of their time thermoregulating to maintain an ideal body temperature. This involves basking in the sun or taking dips into the water to cool down. Breaks are taken only to hunt or protect their territory. And they are quite territorial. These crocodiles live in coastal waters, freshwater rivers, billabongs (an isolated pond left behind after a river changes course), and swamps. While they are generally shy and avoidant of people, especially on land, encroaching on their territory is one of the few things what will make a saltwater crocodile attack humans. They’re not shy to fight anything that tresspasses, however, including sharks, monkeys, and buffalo.

This territoriality is also evident in between crocs. Juveniles are raised in freshwater rivers but are quickly forced out by dominant males. Males who fail to establish a territory of their own are either killed or forced out to sea. They just aren’t social souls at all.

Females lay clutches of about 50 eggs (though there are records of a single female laying up to 90 in extraordinary cases). They will incubate them in nests of mud and plant fibers for around 3 months. Interestingly, ambient temperatures dictate the sex of the hatchlings. If temperatures are cool, around 30 degrees Celsius, all of them will be female. Higher sustained temperatures, around 34 degrees Celsius, will produce an all-male litter.

Only around 1% of all hatchlings survive into adulthood.

Conservation status

Saltwater crocodiles have precious few natural predators. Still, their skins have historically been highly prized, and they have suffered quite a lot from hunting, both legal and illegal. Their eggs and meat are also consumed as food.

In the past, this species has been threatened with extinction. Recent conservation efforts have allowed them to make an impressive comeback, but the species as a whole is much rarer than in the past. They are currently considered at low risk for extinction, but they are still of especial interest for poachers due to their valuable meat, eggs, and skins.

Saltwater crocodiles are an ancient and fearsome predator. They have evolved to dominate their ecosystems, and do so by quietly lurking just out of sight. But, like many apex predators before them, pressure from humans — both directly, in the form of hunting, and indirectly, through environmental destruction and climate change — has left the species reeling.

Conservation efforts for this species are to be applauded and supported. Even though these crocodiles have shown themselves willing to attack humans if we are not careful, we have to bear in mind that what they want is to be left alone and unbothered. It would be a pity for this species, which has been around for millions of years, which has come from ancient titans, survived for millennia and through global catastrophe, to perish.

Crocodile tears are remarkably similar to those of humans

Credit: Pikist.

The phrase ‘crocodile tears’ is often used to denote phony tears of sorrow but, literally speaking, crocodile tears are surprisingly similar to our own in terms of chemical makeup. Since crocs haven’t changed that much for millions of years, these new findings might provide insight into how the eye evolved and lead to new treatments for eye disease.

Most previous studies that analyzed the chemical composition of tears in non-human animals tended to focus on other mammals, such as dogs, horses, or monkeys. It’s been just recently, however, that researchers in Brazil analyzed the tears of reptiles and birds for the first time.

The researchers collected tears from seven species (barn owls, blue-and-yellow macaws, roadside hawks, broad-snouted caimans, and loggerhead, hawksbill, and green sea turtles) from tear ducts or other similar glands.

Tears serve an important role in keeping the eyes healthy. They’re typically made of mucus, oil, and water, which bind together to coat the eye preventing them from drying out and supplying crucial proteins and minerals. Tears also prevent infections and lubricate the eye, clearing debris. In humans, tears are also an expression of powerful emotional states.

Although no other animal is known to weep, the new study shows that at least chemically speaking, human tears aren’t all that different from those of reptiles like caimans.

Veterinarians at Brazil’s Federal University of Bahia analyzed the tears of 7 species of caiman from local conservation centers, animal care facilities, and commercial breeders.

Using special testing kits, the researchers measured the amounts of electrolytes and proteins in the reptiles’ tears.

Remarkably, birds, reptiles, and mammals all had a very similar makeup of their tears, despite the fact that there was great variation in the structures that produce their tears for each species.

“There was more total protein and urea in owl and sea turtle tears, respectively, than in the other animals tested. Electrolyte balance was similar for all species, with higher sodium, chloride, and iron,” the authors of the study wrote.

“The ionic balance of lacrimal fluids of birds and reptiles was similar to that in humans, with higher values of sodium and chloride. However, a similar tear composition did not influence the crystal morphology. Crystallization classification suggested that higher grades and types are due to the different microelements present in the tears of wild species,” they added.

That’s not to say that the tears were identical. Human tears had higher levels of protein compared to other species, on average, offering greater stability of the ocular surface. Caimans and owls have even higher concentrations of proteins, likely because both species have very large eyes and blink rarely. People blink every 10-12 seconds while caimans can keep their eyes open without blinking once for up to two hours.

Examples of tear crystallization patterns in wild animals, graded according to Rolando and Masmali scales. (A) Ara ararauna—type I (Rolando) and grade 0 (Masmali) with uniform crystallization pattern and no spaces between branches. Credit: Frontiers in Veterinary Science.

Doctors often look at dried tears under the microscope in order to diagnose eye disease. When the Brazilian researchers analyzed the crystallization patterns of solid tears, this time they found evidence of much more variation in the tears crystals between species than in the tear composition itself. Sea turtles and caimans were particularly unique, which is likely due to their adaptations to aquatic environments.

According to the new findings published in the journal Frontiers in Veterinary Science, the surrounding environment has an important impact on tear composition. Because tears are the body’s most exposed fluids to the outside world, their composition will become easily modified when the environment is altered, such as by pollution. This can have a detrimental effect on eye health.

In the future, the researchers plan on analyzing tears from more species, as well as uncovering new findings that may translate into new treatments for eye problems in both humans and animals.

This ancient crocodile may have run on two legs like an ostrich

Artist impression of Batrachopus grandis. Credit: Kyung Soo Kim.

Whether loitering on the banks of the Nile or casually floating through the rivers of Costa Rica, crocodiles aren’t exactly filled with joy and life. In fact, to most people, they look like the incarnation of laziness, despite their fearsome appearance.

But how about you imagine this: a crocodile walking on two legs like an ostrich or T. rex. This cartoonish scenery may have actually been very much real during the Early Cretaceous, about 120 million years ago, according to paleontologists who conducted excavations in South Korea.

Although the international team of researchers don’t have any fossilized bones to support their case, they claim that it is very likely that a bipedal crocodilian left pristinely preserved tracks, found near a lake in South Korea.

Nearly a hundred indentations, each 18 to 24 centimeters long, were preserved in the muddy sediment. They all look very similar in shape to those made by Batrachopus crocodiles that lived tens of millions of years earlier, during the Jurassic period.

Credit: Kyung Soo Kim.

While Batrachopus were obviously quadrupeds, the tracks look like they were made by a biped.

“We can see all the digits, all the ridges in the skin – just as if you were looking at your hands,” Martin Lockley, an emeritus professor at the University of Colorado, told BBC News.

“They put one foot in front of another; they could pass a sobriety test walking on a straight line. And there are no front footprints,” Lockley said, adding that depth of impressions made by the heel also supports the idea of an upright gait.

Lockley and colleagues have named the supposed crocodilian Batrachopus grandis, seeing how the shape of the tracks look like they were made by a Batrachopus, albeit a much larger one.

Professor Kyung Soo Kim from South Korea’s Chinju National University of Education also added that the trackways are very narrow and there are no markings left by a dragging tail — something you would surely expect from a crocodile.

The bipedal crocodile must have been 3-meter long judging from the size of the prints. Credit: Kyung Soo Kim.

Previously, in 2012, Lockley and colleagues studied another fossilized trackway in South Korea. These tracks looked very similar to the ones described in the new study, but at the time the researchers thought they must have been etched by pterosaurs — ancient flying reptiles that ranged in size from the size of a sparrow to the size of an airplane.

Credit: Kyung Soo Kim.

At the time, the researchers thought that this was the only explanation — some pterosaurs must have clumsily walked on their two legs before taking flight to the skies. But now, in light of this new evidence, Lockley says that these earlier tracks could have been made by a bipedal Batrachopus.

Well, it’s either that or by some unknown bipedal dinosaur whose limb digits resemble that of a croc. From T. rex to raptors, there’s no shortage of two-legged dinosaurs known to science. And seeing how they have no fossils to speak of, the notion of a two-legged crocodile seems shrouded in skepticism — at least until paleontologists actually find some fossils.

The findings were described in the journal Scientific Reports.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Shocking images of a python devouring a crocodile whole in Australia

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Pythons are biologically equipped to consume prey much larger than themselves. It’s very common to see these large snakes gulping down deer, impalas, and sometimes even humans. But despite this knowledge, it’s still shocking to hear about a python devouring a crocodile. This is exactly what happened to an Australian freshwater crocodile (Crocodylus johnstoni) which was unfortunate enough to stumble into the jaws of an olive python (Liasis olivaceus).

Credit: Martin Muller/GG Wildlife Rescue Inc .

Credit: Martin Muller/GG Wildlife Rescue Inc.

The grisly footage was shared on social media by GG Wildlife Rescue Inc., a nonprofit in Australia on May 31. According to the NGO’s Facebook page, the images were taken by kayaker Martin Muller near Mount Isa, Queensland.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Pythons kill their prey by wrapping themselves around it, squeezing tighter as the victim exhales. Within minutes, the prey dies by suffocation or cardiac arrest. Pythons swallow their food whole thanks to the way their jaws are connected by very flexible ligaments, which can stretch around large prey. Their digestive system and metabolism are also perfectly adapted to breaking down huge meals all at once.

To handle the sudden influx of calories, pythons are known to rapidly increase the size of their internal organs, including the intestines, heart, and kidneys.

Pythons are almost exclusively mammal feeders, although they can consume reptiles. The unlucky Australian freshwater crocodile seen in these photos illustrates this fact.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.

Credit: Martin Muller/GG Wildlife Rescue Inc.


Some extinct species of crocs were plant-eaters, fossil study reveals

Some crocodile species are vegetarians — but also extinct.


Image credits Sasin Tipchai.

A study on fossilized teeth revealed that several ancient groups of crocodyliforms, the lineage that includes crocodiles and alligators, were not carnivores at all; in fact, they were vegetarians. The team reports that at least three (but potentially up to six) different species have relied on a plant-based diet in the past. They all are now extinct.

Mean green veggie machine

“The most interesting thing we discovered was how frequently it seems extinct crocodyliforms ate plants,” said Keegan Melstrom, a doctoral student at the University of Utah. “Our study indicates that complexly-shaped teeth, which we infer to indicate herbivory, appear in the extinct relatives of crocodiles at least three times and maybe as many as six.”

All crocodilians living today share the same general body shape, ecology, and live their lives as generalist, semi-aquatic carnivores. Being carnivores, their teeth are relatively simple, conical implements used to rip and tear through flesh and not much else. Melstrom and his graduate advisor, Randall Irmis, chief curator of the Natural History Museum of Utah, compared the tooth complexity of extinct and living crocodyliforms using a method originally developed for use in living mammals. Overall, they measured 146 teeth from 16 different species of extinct crocodyliforms.

It quickly became clear that the extinct species showed a different pattern of tooth structure. Some species showed multiple specializations that are not seen in living species today, including a feature known as heterodonty: regionalized differences in tooth size or shape.

“Carnivores possess simple teeth whereas herbivores have much more complex teeth,” Melstrom explained. “Omnivores, organisms that eat both plant and animal material, fall somewhere in between. Part of my earlier research showed that this pattern holds in living reptiles that have teeth, such as crocodilians and lizards.”

“So these results told us that the basic pattern between diet and teeth is found in both mammals and reptiles, despite very different tooth shapes, and is applicable to extinct reptiles.”

Through measurements of dental measurements and those of other morphological features, the team reconstructed the diets of the extinct crocodyliforms. The results suggest that these species had a wider range of dental complexity — and thus diet too — than previously estimated.

Plant-eating crocodyliforms popped up quite early in the group’s evolutionary history, the team explains, just after the mass extinction at the end of the Triassic. These species lived up until the end of the Cretaceous, when the dinosaur mass extinction occurred. The team’s analysis shows plant-eating species developed at least three times, possibly up to six times, during the Mesozoic.

“Our work demonstrates that extinct crocodyliforms had an incredibly varied diet,” Melstrom said. “Some were similar to living crocodilians and were primarily carnivorous, others were omnivores and still others likely specialized in plants.”

“The herbivores lived on different continents at different times, some alongside mammals and mammal relatives, and others did not. This suggests that an herbivorous crocodyliform was successful in a variety of environments!”

Their work is not yet done, however. Some fossil crocodyliforms are missing teeth and, armed with the knowledge of the present study, Melstrom plans to reconstruct their diets as well. He also wants to find out why these extinct crocodiles diversified so radically after one mass extinction but not another, and whether dietary ecology could have played a role.

The paper “Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs” has been published in the journal Current Biology.

Crocodile ancestor fossil.

Fossil Friday: Jurassic crocodile shows us how the scaly killers came to be

An ancient fossil is giving us a glimpse into how the Earth came to have crocodiles.

Crocodile ancestor fossil.

A newly identified species of marine crocodile, Cricosaurus bambergensis.
Image credits Heinrich Mallison.

Modern crocodiles are the descendants of a slender, fin-tailed, paddle-limbed animal which lived in the sea, a new paper reports. These ancient creatures fed on the fast-moving prey (squid or small fish for example) that populated Jurassic shallow seas in what is today Germany — and looked more like dolphins than crocs.


“The rock formations of southern Germany continue to give us fresh insights into the age of dinosaurs,” says Dr Mark Young, of the University of Edinburgh’s School of GeoSciences, one of the study’s co-authors.

“These rock layers were deposited at a time when Europe was covered by a shallow sea, with countries such as Germany and the UK being a collection of islands.”

The study comes from an international team which included researchers from Germany and the University of Edinburgh. The fossil itself was discovered in 2014 in a quarry near the town of Bamberg in Bavaria, Germany by a team from the Naturkunde-Museum Bamberg, where it is now housed. The species was named Cricosaurus bambergensis in honor of the town where it was found.

After comparing the fossil with those from other museum collections, the team confirmed: while related species have previously been found in Mexico and Argentina, this one belonged to a previously-unseen species. Several features clearly distinguished this species from other crocs we’re found so far, the team explains. This specimen’s jaws, tail, and the roof of its mouth are, so far, unique.

To allow other researchers easy access to the fossil, the team also created digital, high-resolution images of it. They expect the fossil will aid greater understanding of a wider family of ancient animals, known as metriorhynchid, to which this species belonged.

Sven Sachs, from the Naturkunde-Museum Bielefeld, who led the project, said: “The study reveals peculiar features at the palate that have not been described in any fossil crocodile so far. There are two depressions which are separated by a pronounced bar. It is not clear what these depressions were good for.”

The paper “A new species of the metriorhynchid crocodylomorph Cricosaurus from the Upper Jurassic of southern Germany” was published in the journal Acta Palaeontologica Polonica.

African slender-snouted crocodile. Image credit: Leyo / CC BY-SA 2.5.

New species of crocodile found in Africa right under our snout

African slender-snouted crocodile. Image credit: Leyo / CC BY-SA 2.5.

African slender-snouted crocodile. Image credit: Leyo / CC BY-SA 2.5.

Scientists have identified a new species of crocodile for the first time in more than 80 years. The species, dubbed Mecistops leptorhynchus or the Central African slender-snouted crocodile, did not suddenly appear out of nowhere — it has been hiding in plain sight all along. Up until now, the animal was thought to be the same species as Mecistops cataphractus, its West African counterpart.

Matthew Shirley poses with juvenile Central African slender-snouted crocodiles. Credit: Florida International University.

Matthew Shirley poses with juvenile Central African slender-snouted crocodiles. Credit: Florida International University.

It took Matt Shirley, study lead author and a researcher at Florida International University, more than ten years of painstaking work to come to a new species designation for the Central African croc. During this whole time, Shirley traveled through more than a dozen African countries, paddling across thousands of miles in search for crocs and scoured through museum samples around the world. He even caught malaria 16 times. To make things even more challenging, the M. cataphractus holotype—the specimen used to originally identify the species— was destroyed when the Nazis bombed the National History Museum in London. But, in the end, it was all worth it.

The West African croc was first described in 1835, but scientists have always had a hunch that there may be a second, very similar species.

In a new study published in the journal Zootaxa, Shirley and colleagues showed that there are two slender-snouted crocs. The main difference between the two is that the Central African crocs have softer, smoother scales than their West African cousins. Another defining feature is that the Central African crocs don’t have bony crests on their skulls, unlike their counterparts.

A genetic comparison of the two species suggests that the two diverged more than eight million years ago. The volcanic activity of a volcano in Cameroon led to the formation of mountains that were impenetrable to the crocs. In time, different populations isolated from one another speciated. They’re still very similar but different enough to be called distinct species.

The study is also somewhat bad news for Mecistops cataphractus, which is now down to only 500 individuals left in the wild, following the new designation. Both species are affected by habitat loss and poaching, and Shirley hopes that his work will help boost conservation efforts.

National Geographic reports that Shirley and colleagues are currently working with the governments of Côte d’Ivoire and Ghana to breed the animals in captivity. Ultimately, the plan is to release more than 30 of the animals currently residing at a zoo in Côte d’Ivoire. Hopefully, Africa’s slender-snouted crocodiles can be saved, just like the American alligator, which was on the cusp of extinction in the 1960s but can now be easily observed in nature thanks to protective measures.

Nile crocodiles. Credit: Pixabay.

Scientists play classical music to fancy crocodiles, then scan their brains

Nile crocodiles. Credit: Pixabay.

Nile crocodiles. Credit: Pixabay.

The lives of some scientists are anything but boring. In a world first, researchers placed a Nile crocodile inside an MRI machine and scanned its brain while it was listening to classical music. Bach was on the playlist, if you were just wondering about the reptile’s musical tastes.

The study might sound gimmicky but it’s actually very important. The results, for instance, suggest that the fundamental neuronal processing mechanisms for sensory stimuli evolved hundreds of millions of years ago and can be traced back to a common ancestor of all vertebrates.

Croc brain on music

Brains don’t fossilize, which is a bummer for scientists who would like to know how the most ancient brains function and trace back the evolutionary history of the ultimate biological hardware. Luckily, they have at their disposal the next best thing: crocs. You see, crocodiles have barely changed in the last 200 million years or so, and, as such, they represent the perfect animal model for investigations of ancient neural workings.

Researchers led by Felix Ströckens from the Department of Biopsychology at Ruhr University Bochum wanted to investigate how the crocodilian brain might respond to complex sounds, so that they might compare the patterns to those of birds and mammals. To this end, the researchers inserted a Nile crocodile (Crocodylus niloticus) into an MRI machine in order to scan its brain. Yes, science can be very exciting (and dangerous).

Magnetic resonance imaging, or MRI, uses a powerful magnetic field, radio waves and a computer to produce detailed pictures of the inside of your body. Previously, MRI scans have been performed on various mammals, but this is the first time a cold-blooded reptile was put inside an MRI machine, which had to be modified for this study.

Croc prepared for MRI scan. Credit: Felix Ströckens.

Croc prepared for MRI scan. Credit: Felix Ströckens.

As you might imagine, placing a croc inside a very cramped and noisy machine was challenging work. In order to make sure the croc didn’t move inside the machine for proper scanning, the reptile was sedated and had its snout taped for extra safety. The fact that the animal is cold-blooded added to the complexity of task since brain scans can be skewed by the animal’s body temperature. Luckily, the researchers were at least fortunate enough to work with very gentle crocs. Perhaps, the selection of sounds that the researchers played, which also included classical music, helped to calm the beasts.

“In the first step, we had to overcome a number of technical obstacles,” said research team member Mehdi Behroozi. “For example, we had to adjust the scanner to the crocodile’s physiology, which differs massively from that of mammals in several aspects.”

The five juvenile crocs used in the study were exposed to various visual and auditory stimuli like flashing red and green lights or random chord noises between 1,000 Hz and 3,000 Hz. To gauge the croc’s response to complex sounds, the researchers played Johann Sebastian Bach’s Brandenburg Concerto No. 4, which had been employed in previous studies that worked with other animals, thus providing a good reference.

The brain scans revealed that different brain areas were activated in the crocodilian brain when the animal was subjected to complex sounds compared to when basic sounds were played. The observed pattern is very similar to that seen in mammals and birds which were exposed to music. This suggests that the structural and functional machinery of this kind of sensory processing appeared hundreds of millions of years ago. This ability was then preserved and passed down the evolutionary family tree.

“It was technical breakthrough,” Ströckens told Gizmodo. “We could prove that fMRI can be used in reptiles which differ massively in their physiology from mammals or birds (e.g. body temperature and breathing patterns). This will allow future studies to investigate many species which have not been investigated yet with this non-invasive method.”

Researchers from Iran, South Africa, France and Germany participated in the study, which was published in the journal Proceedings of the Royal Society B: Biological Sciences.

Researchers find the oldest ever crocodile eggs

Paleontologists working in Portugal have discovered the world’s oldest crocodilian eggs — they’re so well preserved that they can tell us a lot about their species and environment.

The croc eggs are surprisingly well preserved. Image credits: Octavio Mateus.

Looking at crocodiles, it’s not hard to imagine that they’ve been around for so long. They evolved some 200 million years ago, with the early dinosaurs, and haven’t changed that much since then. These eggs date from 152 million years ago, which is a big upgrade from the previous record, dated to approximately 112 million years ago.

“The fact that they are from the Late Jurassic makes these eggs the oldest crocodilian eggs known so far,” said João Russo of Universidade Nova de Lisboa, Portugal. “This new discovery from Portugal extends the knowledge of this type of egg by approximately 40 million years.”

Based on the size and shape of the eggs, he estimates that the mother croc would have measured two meters and looked a lot like modern crocs. It belonged to a group called crocodylomorphs which had many similarities to modern crocs but were a much larger and diverse group.

“The fossil record tells us that crocodiles and their relatives (forming the larger group of crocodylomorphs) were much more diverse in the past, with different feeding habits, ecological niche distribution or morphology,” he added.

The eggs weren’t laid by “true” crocodiles, but rather by some of their relatives (or rather, ancestors) called crocodylomorphs. During Mesozoic and early Cenozoic times, Crocodylomorphs were an incredibly varied group, emerging at least as early as the dinosaurs. “Modern” crocodiles, for comparison, emerged in the late Cretaceous, some 100 million years ago. Crocodylomorphs live on to this day, though they’re not as varied.

The thing is, crocodile bones are not that uncommon throughout the fossil history — and neither are other crocodylomorph bones. Eggs, however, are a different issue. While a croc can live on for years or decades, an egg “survives” for a few months. They’re also frail and less likely to fossilize, which makes this finding even more valuable. Even when eggs are found, they’re usually fragmented. The eggs are also quite similar to those of modern crocs.

The eggs were found in a dinosaur nest near the village of Lourinhã, north of Lisbon. This is quite intriguing because while crocs are top predators today, it wasn’t like that in the past, and some dinosaurs were above them in the food chain. Why would the croc eggs be in a dinosaur nest? That’s not clear at the moment.

Journal Reference: João Russo , Octávio Mateus, Marco Marzola, Ausenda Balbino — Two new ootaxa from the late Jurassic: The oldest record of crocodylomorph eggs, from the Lourinhã Formation, Portugal. http://dx.doi.org/10.1371/journal.pone.0171919

The Crocodilian Revolution: amazing myths and facts about crocodiles

Almost every time I stop by a crocodile enclosure in a zoo, I hear people wondering if these are real animals or plastic models. Captive crocodilians (crocodiles, alligators and their less-known relatives such as caimans) don’t move that much. And this “laziness” has fooled people for centuries.


A female Cuban crocodile given a piggyback ride by her long-term male partner. Credits: Vladimir Dinets.

Deceivingly Clever

Virtually every popular or scientific description of crocodilians, from Herodotus two thousand years ago to school textbooks of the 1990s, calls crocodilians not just lazy, but stupid (even if more polite or scientific-sounding words are used). When I started my research on crocodilian behavior ten years ago (as a Ph.D. student at the University of Miami, upon a suggestion by my adviser Steven Green), I shared this misconception.

There were some dissenting voices. In 1935, E. A. McIlhenny described some really interesting behaviors; in the 1960s L. Garrick with colleagues discovered a complex signaling system used by crocodilians. But McIlhenny wasn’t a professional zoologist, so his accounts (known today to be entirely accurate) were distrusted by scientists, as were other unusual claims scattered in even older literature. And Garrick, content with discovering some cool things such as crocodilians using infrasound (acoustic vibrations too low for humans to hear), didn’t try to study the behavior of these animals more broadly.


A mugger crocodile trying to lure some egrets by offering them a stick for nest building. Credits: Vladimir Dinets.

I knew that crocodilians were the only large non-marine animals to survive the mass extinction that wiped out all non-avian dinosaurs. More than one crocodilian lineage managed to survive the catastrophe (the split between crocs and gators pre-dates it). I intuitively felt that there had to be something special about them. But I had no idea what it could be, and scientific literature of the time wasn’t much help.

We shouldn’t be too critical of scientists. Studying crocodilian behavior is a zoologist’s nightmare. Much of it can’t be seen in captivity, but observing it in the wild is difficult and sometimes dangerous (in the last ten years, three crocodilian researchers have died in the line of duty). Crocodilians inhabit murky waters, mosquito-infested swamps and impenetrable rainforests. They are mostly nocturnal, and many have become obsessively shy after decades of overhunting. They are specialized ambush predators, with numerous adaptations (such as the most sophisticated heart in the animal kingdom) allowing them to conserve energy, in part by not moving too much. For example, they don’t hunt very often: being cold-blooded, they eat about ten times less than mammals of the same size (their ancestors were warm-blooded and more active, but that was over a hundred million years ago). It’s not unusual to watch a crocodile all day and never see it move, so you need a lot of patience and endurance.

Crocs in the Night

So I became pretty much the first zoologist to systematically observe crocodilians in the wild at night. I began with a relatively easy species, the American alligator, and then studied over twenty others. And it worked. Within a week I began discovering new things, and this exhilarating marathon of discovery just never ended. In five years I got my Ph.D.; it took me four more years to follow up on some leads that were outside the scope of my thesis, and to publish everything (including a popular book Dragon Songs check it out on Amazon). By that time the subject of crocodilian behavior was no longer a scientific swamp: researchers all over the world are now studying it and making one discovery after another.

So, what have we learned in the last ten years?


Dancing American alligators. Credits: Vladimir Dinets.

Crocodilians are not stupid. They have relatively small brains, but, just like in birds, these brains are organized very differently from mammalian brains: their volume is utilized more efficiently. These animals are smart and have very complex behavior, instinctive and learned.

They use a sophisticated, flexible communication system. It is a combination of sounds, infrasound, chemical and visual signals, produced by unusual and still poorly understood physical mechanisms. This system can be easily optimized to work in a broad variety of habitats, from overgrown marshes to flooded forests to large open lakes. Crocodilian “language” is so perfect that for the last 70 million years it hasn’t changed much: alligators and crocodiles still largely understand each other.

They are deadly hunters, second only to humans in versatility. Their hunting techniques are only partially known, but we have found that they can hunt as effectively on land as underwater, cooperate with each other (for example, chase prey into an ambush, or form a chain to drive schools of fish into shallows), and use lures. Alligators and crocodiles that live near egret rookeries often float with little sticks on their snouts during the birds’ nest-building season. If an egret looking for building material tries to pick up the stick, it promptly gets snatched. But they are not strictly predatory: they can eat fruit and even be important seed dispersers for some tree species.


Baby alligators raised in mixed creches love to ride on the backs of their older friends. Credits: Vladimir Dinets.

They are surprisingly social, particularly gators. American alligators gather on spring nights to dance and then sing in choruses in the morning. They are promiscuous, but often have preferred partners and mate with them year after year. Crocodiles have a more hierarchical social system… but this aspect of crocodilian lives still needs a lot of research before we understand even the basics.

They can be excellent parents. In some species both mother and father protect and feed the brood; in others multiple females bring their babies together into a crèche and take turns watching over it.

And they can be playful, friendly, even funny. They play with toys, with each other, and with other animals such as otters. They can become tame and form strong bonds with people. One amateur naturalist in Costa Rica rescued a wounded crocodile, and the animal became his faithful friend: for many years the man and the huge crocodile played together and even pulled little practical jokes on each other.

But don’t try that at home. They might look like plastic models, but they can be very fast, and you can’t presume to be smarter than them.

This article was written by Vladimir Dinets, of the University of Tennessee, Knoxville. He has spent a decade studying the behavior of crocodiles, evaluating their habits and noting playful interactions and complex behaviors.

Nile Crocodile enters Florida, researchers find

Scientists from the University of Florida have mate a startling discovery: Nile Crocodiles are now in Florida, infiltrating local populations in the Everglades. They warn that these crocs are extremely dangerous, and can injure or kill humans.

Nile crocodile in Gulu, Uganda. Photo by Tim Muttoo

The Nile Crocodile (Crocodylus niloticus) is an African crocodile and the second largest reptile in the world, after the saltwater crocodile. It can grow up to 5.5 metres (18 feet) in length and was blamed for at least 480 attacks on people and 123 fatalities in Africa between 2010 and 2014. Another report claims that the Nile crocodile kills hundreds of people each year. Either way, this is definitely a species which can be dangerous, much more dangerous than native alligators.

DNA analysis has confirmed that at least three juveniles are part of the Nile species, linked to crocodiles from South Africa. Kenneth Krysko, a herpetology collections manager at the Florida Museum of Natural History told the journal Herpetological Conservation and Biology that the species can survive and potentially thrive in sub-tropical Florida.

“The odds that the few of us who study Florida reptiles have found all of the Nile crocs out there is probably unlikely. We know that they can survive in the Florida wilderness for numerous years, we know that they grow quickly here and we know their behaviour in their native range, and there is no reason to suggest that would change here in Florida.”

Crocodylus niloticus is considered a generalist predator which can feast on pretty much all types of meat. They can certainly adapt to Florida’s environment, munching down birds and mammals. Researchers don’t know where these crocs came from, but pet owners are the likely cause. According to the Guardian, large groups of Nile crocodiles have been imported from South Africa and Madagascar, both for display at places such as Disney’s Animal Kingdom, and to supply Florida’s pet trade.

It’s not the first time Florida is dealing with invasive species; on the contrary, the state is one of the most invaded areas in the world. The spiny lionfish has destroyed reef-dwelling fish across the Caribbean, the Cuban tree frog has also taken out many native specimens, and recently, the Burmese python has become so common that Florida is authorizing python hunts.

“My hope as a biologist is that the introduction of Nile crocodiles in Florida opens everyone’s eyes to the problem of invasive species that we have here in our state,” Krysko said. “Now here’s another one, but this time it isn’t just a tiny house gecko from Africa.”


Artist impression of the "Carolina Butcher," Carnufex carolinensis. Credit: JORGE GONZALES

Croc ancestor was the top two-legged predator on Earth, long before T. Rex and other dinosaurs

Long before T-rex claimed the top dog spot among terrestrial predators, a vicious crocodile ancestor that walked on its hind legs was at the top of the food chain during the Triassic. The fossils of the Carnufex carolinensis, also known as the the “Carolina Butcher,” were discovered decades ago  in the Pekin Formation, a geological formation in North Carolina’s Chatham County. It was only recently that researchers reanalyzed the fossils and concluded they were dealing with an all new predator that roamed the Earth several million years before dinosaurs were even around.

Artist impression of the  "Carolina Butcher," Carnufex carolinensis. Credit: JORGE GONZALES

Artist impression of the “Carolina Butcher,” Carnufex carolinensis. Credit: JORGE GONZALES

Lindsay Zanno, an assistant professor at North Carolina State University and the lead author of a paper describing the research, was among those who first analyzed the ancient fossils. She and her team dated the ancient croc as being 231 million years old. Using a high-resolution surface scanner, the team mapped the croc’s skull and created a 3-D model which revealed it was littered with dozens of blade-like teeth. In all likelihood, it used them to slice meat from the bones of the animals it killed or scavenged.

The model also showed that the Carolina Butcher stood at least 9 feet tall and most likely walked on two legs, judging from the forelimb to skull ratio (very similar to T. Rex). Sometime in the Late Triassic, however, the beasts went extinct following a massive wipe-out. In the end, its place was taken by large dinosaurs. But the smaller ancestors of crocodiles made it through the extinction, and eventually evolved in today’s crocs and alligators.

Reconstructed skull of Carnufex carolinensis

Reconstructed skull of Carnufex carolinensis.

The discovery is important since it fills an evolutionary gap. Even so, there are still unknowns further up the ladder, like who’s the common ancestor of the dinosaur line and the crocodile line?

A paper was published in the journal Scientific Reports.

Crocs love to have fun, study shows

A new study has revealed the fun-loving side of crocodiles; the reptiles, generally regarded as ferocious and aggressive, are reported to surf waves, play ball and engage in piggyback rides to have fun.

Crocodiles just wanna have fun. Image via Utah People Post.

Vladimir Dinets of the University of Tennessee, Knoxville has spent a decade studying the behavior of crocodiles, evaluating their habits and noting playful interactions between the species, and even with humans. The study has been published in the journal Animal Behavior and Cognition and shows that even beasts sometimes like to have fun.

Dinets said:

“Many aspects of crocodilian behavior remain poorly known due to their rare occurrence and to the difficulty of observing predominantly nocturnal predators. In the case of play, an additional problem appears to be that people witnessing such behavior consider their observations unworthy of publishing or unlikely to be taken seriously.”

Crocodile playful interactions are actually quite complex – including locomotor play, object play and social play. Crocs like to engage in playing with others or with objects more often than being social. Playful behavior has been observed previously, though it wasn’t interpreted accurately.

“In many cases this behavior appears to be accidental, but on two occasions I have seen crocodilians doing this in a manner strongly suggesting play. In both cases, the objects were pink Bougainvillea flowers that were floating in the pools where the animals were kept captive.”

A male crocodile gives a piggyback ride to his lifelong female partner. Credit: Vladimir Dinets

In several instances, he actually observed crocodiles playing with humans. He details one such episode:

“The crocodile would swim with his human friend, try to startle him by suddenly pretending to attack him or by sneaking up on him from behind, and accept being caressed, hugged, rotated in the water and kissed on the snout.”

His research seems to suggest that crocodiles may be much more affectionate than previously thought, and can even harbor feelings towards humans.

“A man who rescued a crocodile that had been shot in the head became close friends with the animal. They happily played every day until the crocodile’s death 20 years later”.

Crocodiles evolved 55 million years ago and have been a top predator ever since. Our knowledge and understanding of them is still quite lackluster, because they dangerous and often find in remote areas. This paper shows a side of them we are just starting to discover – and there are likely others as well.

“Play behavior in crocodilians is not uncommon, but it remains virtually undescribed in scientific literature. I present the first overview of play behavior of three types (locomotor play, object play and social play) in crocodilians based on original observations, published reports and anecdotal evidence”, the paper’s abstract reads.

Crocodilians use sticks to attract prey

  • Two distinct groups of crocodilians have been reported to use tools for hunting
  • They balance sticks on their snouts, baiting birds who want to use the sticks for nests
  • Crocodiles actively search for the sticks (which are usually rare) and do this more often during the birds’ mating season

Mugger crocodile (Crocodylus palustris) at Madras Crocodile Bank, Tamil Nadu, India, with sticks on its head. Image credits: Dinets et al. (2013).

It’s been known for quite a while that the usage of tools isn’t restricted to humans. Monkeys (of course) also use tools, but this type of behavior has also been reported in other species, including crows, dolphins, elephants and otters. Now, a new study has reported that crocodiles and alligators also use sticks to attract prey.

In recent years, reptile research has provided some stunning results, showing that they are not only cold-blooded efficient killers, but that they exhibit a myriad of remarkable behaviors. Play behaviour, complex social interactions, gaze recognition, pair-bonding and monogamy, social hunting, speedy learning abilities and good memories – they have all been reported in reptiles.

Now, another very interesting unexpected adaptation has been demonstrated across these groups: tool usage.

As described by Dinets et al. (2013), Mugger crocodiles Crocodylus palustris in India and American alligators Alligator mississippiensis in the USA have been observed to lie, partially submerged, very close to birds they want to hunt, with sticks balanced carefully on their snouts. Birds want to take the sticks to use them in their nests and… let’s just say it usually has a very bad ending for the birds.

But what’s remarkable is that this occurrence of stick usage by crocodilians isn’t random! Stick displaying took place consistently more often with crocodiles living closer to rookeries, and it also took place more often during mating season – when birds are more inclined to construct nests. It’s also noteworthy that sticks are pretty rare in this type of environment – the reptiles actively search for them, especially during the birds’ mating period.

Baiting behavior was demonstrated before in archosaurs (the big group of species which includes crocodiles, birds and all extinct dinosaurs). Green herons (Butorides virescens) often do it: they use feathers, twigs and even berries and bits of bread to attract fish, while burrowing owls (Athene cunicularia) use mammal dung to attract dung beetles. Also, anecdotal reference suggests that crocodiles also use fish fragments to attract birds. But the fact that this has been consistently reported in two separate groups seems to suggest that this type of behavior is mainspread.

If you think about it, crocodiles have been around for over 70 million years – since the Cretaceous. They are incredibly well adapted to the environment, being able to live as scavengers and survive for months without food. They can even go into a state of hibernation when conditions aren’t favorable, waking up when things are looking up. So it makes sense that they learned a trick or two about hunting.

Each bump on the crocodile or alligator's face is barely a millimeter wide and has the shape of a dome. (c) :Leitch & Catania.

Crocodile skin around its jaws is 10 times more sensitive than that of human fingertips

Considering their heavy scale armor, and ferocious apatite, “sensitive” might not be the first adjective that comes to mind when describing crocodiles or alligators. A new study has sought to answer a long lasting riddle for biologists after it finally found the purpose of peculiar black spots or domes on crocodile and alligator heads. Apparently, these act as extremely sensitive sensors, that can sense touch or pressure 10 times better than the skin of a human’s fingertip.

Some 4000 such dots are present on alligator heads, particularly along their jaws, inside their mouths, and between their teeth. Crocs are even more gifted, as they also have dome sprinklings over parts of the rest of their bodies, thus amounting to 9000 dots in total. These formations were first described over a century ago and have since been known as integumentary sensory organs, or ISOs.

Despite scientists have known for a very long time that the domes pose a sensing function of some sort, the exact purpose and functionality has escaped them. Many studies have argued that these might act like salt sensors, helping crocs and alligators detect unsafe to drink water, or used to detect faint electrical signals given off by prey. No evidence has been provided, however.

Each bump on the crocodile or alligator's face is barely a millimeter wide and has the shape of a dome. (c) :Leitch  & Catania.

Each bump on the crocodile or alligator’s face is barely a millimeter wide and has the shape of a dome. (c) :Leitch & Catania.

Vanderbilt University grad student Duncan Leitch, along with his adviser biologist Ken Catania, took it upon themselves to provide an answer to this puzzling question. Leitch first took a croc-handling course – a baby croc-handling course that is – and order relatively small alligators from refuges and crocodiles from commercial breeders.

Bumps that turn the croc and alligator into perfect on the sly predators

When he cut away the domes, he uncovered a vast network of nerve endings, including touch receptors tuned specifically to pressure and vibration. He then tested the various other theories presented in studies that sought to define the ISOs function. The animals were inserted in saltwater of varying degree, but the ISOs nerve endings didn’t react. Then, a 9-volt battery was dipped into the water to create an electric field, but again nothing back at the croc’s end. Both leading theories were busted.

Instead, Leitch found that the nerves feeding into the ISOs end in a variety of touch sensors, after he found the domes responded to stimuli from von Frey filaments—hairlike, standardized wires used to gauge sensation levels. Actually, the black dotes on the animals’ faces are so sensitive that they can detect pressure too slight even for the filaments.

“My professor and I didn’t believe at first that they could be that reactive,” Leitch said. “We closed our eyes and tried to tickle each other with [the filaments] on our fingertips, and neither of us could even feel it.”

Ten times more sensitive than our fingertips

The researchers found that the most sensitive ISOs can sense forces as tiny as 78 millionths of a Newton or  10 times more sensitive than the most sensitive parts of our fingertips. This explains how crocs and alligators are able to detect ripples from even a single drop of water-and therefore even very weak prey movements, a theory for ISOs function first mentioned in 2002. To put the theory to the test, Leitch  dropped pellets of food into the still tiny animals’ water tanks, all while in pitch black. He found that the crocs would almost instantly turn towards the food was, heads towards it, and bite it within 50-70 milliseconds after their skin touched it.

“This was exactly what I had hoped somebody would do with ISOs, in terms of really looking at the distribution and the electrophysiology, because that’s really the way to answer these questions about function in a tiny sense organ like this,”  said Kent Vliet, co-chair of the Association of Zoos & Aquariums’ Crocodilian Advisory Group.

The sensors aren’t only used for feeding, though. A great proportion of these domes are present inside the animals’ mouth, between teeth especially. These would most likely serve to offer sensitivity to the mout to help their young out of their shells and to hold the offspring between their jaws for protection.

Next the researchers plan on studying why crocs also have these bumps on their bodies, not just their faces. Some people have speculated that the alligators have body ISOs buried deeper in their skin, but Leitch saw no evidence.

“What’s interesting to me is that such a scaly animal, one that’s so heavily armored, could have a sensitivity that rivals or surpasses our tactile abilities,” Leitch said. “But they have all these little tactile areas that are so exquisitely sensitive—it seems really amazing.”

Findings were published in the Journal of Experimental Biology.


The oldest crocodile so far found was 30 feet long had a shield for a head

Casey Holliday, a University of Missouri researcher, was looking through some of the hundreds of unlabeled items kept in a storage facility when he come about a remarkable find –  a skull fragment from an ancient croccodile, dating back from the late Cretaceous, around 95 million years ago. What’s really interesting about the find is not only the fact that it was 30 feet long, or that it’s the oldest closest relative to modern day crocodiles; it’s that it had 5 feet long skull, which featured a shield like shape, granting him the nickname “Shiedcroc”.

crocodile shield head skull fragmentThe crocodile, which is part of a previously undescribed species called Aegisuchus witmeri, was first found in Morocco by local fossil diggers. Since the African soil is recognized as an important source of fossils, it’s become an important target zone for researchers, however due to its extensive land mass, it’s been a lot more practical to provide financial incentives for the local populace to dig for fossils. Most of the things they dig up are worthless, some wind up at mineral or rock shows/shops, and a few are deemed valuable enough to be further studied. The skull fragment was dug up years ago, but for some reason it was stacked up in storage facility in the Royal Ontario Museum in Toronto, until Holliday came by and re-discovered it.

Although it was just a fragment of the croc’s massive skull, scientists were able to semi-accurately assess it’s head proportions by performing CAT scans and geometrical analysis, and hence the rest of its buss-sized body. The skull featured bumps and grooves on its roof, which signaled the fact that it was once filled with blood vessels, which would’ve likely delivered blood to a thick, circular, shield-like mound of skin atop the creature’s skull. This is a unique feature, never before seen in any crocodile species, modern or ancient.

The researchers believe, however, that its thick shield-like skin didn’t serve as a defensive weapon, but rather as a show-off feature to impress mates or ward-off predators; a sort of peacocking. The discovery can help scientists learn more about the evolution of crocodiles as well as offer new information about how to protect modern reptilian habitats.

“Understanding the climate of the past, and knowing what we know about climate changes today, it does give us an idea that this type of an ecosystem is a hotbed of diversity, and they are highly susceptible to changes, whether due to the climate, the chemistry of water or carbon dioxide in the air,” Holliday said.

Holliday plans to give the skull chunk back to the Royal Ontario Museum, where it will be put on display later this year.

Holliday plans to give the skull chunk back to the Royal Ontario Museum, where it will be put on display later this year, and of course continue his study of the crocodile’s evolution.

“Researchers are finding a lot of fossils of crocodiles that were terrestrial predatory crocodiles or terrestrial herbivorous crocodiles with adaptations on the teeth to eat plants, as well as all sorts of aquatic crocodiles and fully marine ones,” Holliday said. “These prehistoric fossils tell us that today’s crocodiles are actually kind of boring.”

Images courtesy  of MU NEWS BUREAU. Source.