Jaws Full of Teeth – American Crocodile

Chances are, when someone mentions crocodiles, you most likely immediately think of the Nile and saltwater crocs of Africa and Australia, respectively. The fact is, these ancient monster reptiles are so evolutionarily successful that they occur in the Americas too. The American crocodile (Crocodylus acutus) is found throughout the waters along the Pacific coast of Mexico and Central and South American down to Ecuador. It is even present on the Southern tip of Florida in the United States and in the Caribbean islands. The highest concentration of American crocodiles is in Lago Enriquillo, a hypersaline lake in the Dominican Republic. It’s not surprising how widespread crocs are given that they’ve been on the earth for 84 million years – even before dinosaurs.

Sarcosuchus imperator skull compared with extant crocodile species:

The American crocodile is one of the largest crocodilian species in the world and South American male crocs can reach lengths of up to 20 feet. Lengths of 14-16 feet are much more common, however, and U.S. crocodiles generally don’t exceed 13 feet. At sizes like these, they do pose a significant threat to humans and are more aggressive than American alligators. Although very rare, human killings have been recorded. American crocs are very tolerant of saltwater, hence their other common name of American saltwater crocodile, and possess special glands in their tongues that secrete excess salt to keep their internal saline concentration in balance.

Crocodiles are air breathing creatures and are therefore buoyant to a certain degree due to the air in their lungs when they inhale just as any other land animal. Unfortunately, they wouldn’t be able to hunt if they were just floating on the surface of the water all the time, or even slightly submerged. Their prey would see them for sure. But being the reptilian masterminds that they are, they’ve developed a strategy to combat this. Crocodiles will seek out stones and swallow them to create a ballast. This way, they can sink themselves to the bottom or rise up to the surface whenever they please. Mostly they submerge everything but their eyes and nostrils and lie in wait for anything edible to wander too close, but they will also hang out on the bottom of a river or lake too and are capable of staying under for hours. American crocodiles eat anything from large mammals and birds to crabs, fish, and snails. They will also sometimes scavenge for carrion.

When it comes to breeding, usually in late fall or winter, American crocodiles will come together and partake in surprisingly gentle and elegant courtship that can last up to a month before any mating takes place. The female will then excavate a burrow, or if no burrowing sites are available, create a mound in which to lay her eggs. The material for the nest and amount of incubation is extremely important because sex is determined by temperature and a subtle fluctuation out of optimal range could create a clutch of either all female or all male crocodiles. This would decrease genetic variation in the species and make them more vulnerable to disease and other factors that can devastate populations. Both parents stay and aggressively protect the nest until the babies hatch, then the female provides them with protection and transportation for several weeks until they disperse.

As big and heavy as American crocs are and as lazy and lethargic as they appear to be most of the time, their agility is not to be underestimated. These huge reptiles can swim up to 20 miles an hour and run on land at 10. When they are walking, trotting, or running, they move their legs underneath and raise their bodies off the ground. Freshwater crocodiles can actually gallop and reach speeds of 15 miles per hour.

This is a Nile crocodile, but it gives you an idea of what they look like when they run:

Here’s a video of a freshwater crocodile galloping as well:

So if you ever see a wild crocodilian of any kind, don’t assume you can just run away from it if you get too close. Stand way, way back and enjoy one of the most perfect, unchanged predators on earth.

In memory of Lolong, the world’s largest captive crocodile, who died on February 10th, 2013 in a conservation center in the Philippines. He was a 20.3 foot long saltwater crocodile and is thought to have been over 50 years old. His cause of death is still unknown.

References:
1. Fishman, Jake and MacKinnon, Kristin. “Crocodylus acutus (American Crocodile)”. Animal Diversity Web. University of Michigan Museum of Zoology, 2009. Web. 24 June 2015. http://animaldiversity.org/accounts/Crocodylus_acutus/

2. “American Crocodiles.” National Geographic. National Geographic Society, n.d. Web. 24 June 2015. <http://animals.nationalgeographic.com/animals/reptiles/american-crocodile/&gt;

3. Swiman, Elizabeth, Mark Hostetler, and Sarah Webb Miller. “Living with Alligators: A Florida Reality.” EDIS New Publications RSS. University of Florida, Aug. 2005. Web. 24 June 2015. <http://edis.ifas.ufl.edu/uw230&gt;.

4. Taplin, Laurence E., et al. “Lingual salt glands in Crocodylus acutus and C. johnstoni and their absence from Alligator mississipiensis and Caiman crocodilus.” Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology 149.1 (1982): 43-47.

5. Wedel, Matt. “Eusuchia.” Unversity of California Museum of Paleontology. University of California, Berkely, May 2010. Web. 24 June 2015. <http://www.ucmp.berkeley.edu/taxa/verts/archosaurs/eusuchia.php&gt;.

6. Parrish, J. Michael. “The origin of crocodilian locomotion.” Paleobiology (1987): 396-414.

7. Britton, Adam. “Lolong Officially the World’s Largest Crocodile in Captivity.” Weblog post. Croc Blog. Crocodilian.com, 23 June 2012. Web. 24 June 2015. <http://crocodilian.blogspot.com/2012/06/lolong-officially-worlds-largest.html&gt;.

Photo and Video Links:
1. http://img3.wikia.nocookie.net/__cb20120817051721/dinosaurs/images/7/79/Sarcosuchus.jpg

2. http://crocodilian.com/cnhc/images/!cbd-faq-q1h.jpg

3. http://www.herpnation.com/wp-content/uploads/2011/05/AmerCroc_Snook.jpg

4. http://www.chrisgillette.com/Nature/Florida/i-RFFjpvx/0/L/Crocodylus%20acutus-L.jpg

5. http://25.media.tumblr.com/tumblr_m6s3ch2JN81r3zfc1o1_500.jpg

6. https://www.youtube.com/watch?v=d_Qmi8MP5uI