Osa Safari

The American Crocodile

(Crocodylus acutus)

Mike Boston

Mike is an honor’s biology graduate of the University of Portsmouth and is the owner / operator of Osa Aventura, the premier guiding outfitter for Corcovado National Park, and has led groups into the Park for the past eighteen years.  Contact him directly at mike@osaaventura.com.


The American Crocodile (Crocodylus acutus) is one of four species of crocodile to be found in the New World Tropics (Neotropics).  It is the most widespread of the New World species, ranging from the tip of Florida through southern Mexico and Central America to Venezuela, Colombia and Ecuador.  It is also found throughout much of the West Indies.  The other three species have very restricted distributions: the Orinoco crocodile to the Orinoco river basin; Morlete’s crocodile to southeastern Mexico and Belize; and the Cuban crocodile to western Cuba.  The latter two species are relatively small crocodiles, seldom exceeding 3 meters in length.  However, the American Crocodile, and its sibling species, the Orinoco Crocodile, are reputed to reach lengths in excess of 6 meters – and well over a ton in weight!  They share the dubious distinction, therefore, of being the largest predators in the Neotropics – a title the American Crocodile alone holds in Central America!  However, not that long ago—geologically speaking—Porosaurus reigned supreme as one of the largest non-marine predators of all time.  This monster caiman, reaching 16 meters (50 feet) and weighing over 18 tones, terrorized the Amazon Basin up until about 6 million years ago.  Its fossilized skull alone weighed 500 kilograms!

(Crocodylus acutus)

(Crocodylus acutus)

Like all crocodilians world wide—with the possible exception of the Common Caiman—the American Crocodile is threatened with extinction.  And like all of its relatives it was hunted mercilessly for its skin.  In an attempt to rescue this species from possible extinction, the Convention on International Trade in Endangered Species (CITES) placed the American Crocodile on Appendix 1 (Endangered) in the 1970s, preventing further trade in skins and live specimens among signatory nations. However, thanks to Costa Rica’s rigorous conservation laws, and its present system of protected wetland areas, this country has ensured a secure future for this majestic crocodilian within its national borders.  Costa Rica is perhaps the only country in its range where the American Crocodile is still relatively abundant.  On both versants of the country sizeable specimens of the American Crocodile can be seen frequently in swamps, tidal estuaries and sluggish rivers.  I, personally, have seen American Crocodiles of over 4.5 meters on the upper Rio Sierpe, and have been assured by several Park Rangers that 5 to 6 meter specimens live in and around the Corcovado Lagoon in the heart of Corcovado National Park!

Common Caiman

Common Caiman

The American Crocodile shares its amphibious world in this country with the Common Caiman (Caiman crocodilus).  The two species are often confused with one another.  However, both represent distinct lineages within the crocodilians: the American Crocodile is a true crocodile (sub-family Crocodilinae), whose members are pan tropical; the Common Caiman is in fact an alligator (sub-family Alligatorinae) whose members are confined to the New World (with the curious exception of the Chinese Alligator).  The best known member of this group is the Mississippi Alligator from the Southeastern United States.  The Common Caiman seldom exceeds 2 meters in length, but the following characters can readily tell specimens of similar size of caiman and crocodile apart:

  • The common caiman is darkish brown in color with distinct black bands on its tail; the American Crocodile on the other hand is drab olive green, and the black markings on its tail do not form bands.
  • When basking on a riverbank, a Common Caiman will generally hold its head up; the American Crocodile will rest its head on the ground.
  • The snout of the Caiman is shorter and more rounded, with its eyes and nose more prominently raised; the American Crocodile has a longer, narrower snout, with less prominently raised eyes and nose.
  • From a dorsal view, the snout of the Caiman is not constricted behind the nose; that of the American Crocodile is distinctly constricted.
  • When its mouth is shut, only the teeth of the upper jaw of the Common Caiman are visible; the teeth of the lower jaw slot into the upper jaw. In the American Crocodile, however, the teeth of both the lower and upper jaws are visible when its jaws are shut – look for the large fourth tooth of the lower jaw which slots into the constriction of the upper jaw behind the nose.

Another difference between the American Crocodile and the Common Caiman is in their habitat preference.  Although they cohabit in many fresh water areas, the latter is in ways more adaptable and will even inhabit watery ditches, transient pools and fast flowing creeks.  The Common Caiman will rarely, if ever, stray into brackish river estuaries, and never into the sea.  The American Crocodile is choosier in its fresh water habitats, favoring lakes, lagoons and sluggish rivers.  However, it shares with the Indo-Pacific Crocodile the unique ability to utilize salt-water habitats, such as tidal estuaries, mangroves and the sea.  I have often seen American Crocodiles in the seas around the Osa Peninsula, even feeding at sea in front of the Rio Sirena, in Corcovado.

American Crocodile

American Crocodile

We all regard crocodilians as primitive beasts and, let’s face it; their appearance serves only to reinforce this view.   But, behind that primordial guise lies a sophisticated animal indeed.  We traditionally refer to them as reptiles, with all the lowliness that this grouping implies.  But current taxonomic wisdom has elevated the crocodilians to a loftier status and grouped them along with the birds.  They share many features and behaviors in common, among them a four-chambered heart (mammals too have four-chambered hearts, but of a different configuration to that of birds and crocodiles) and a sophisticated system of parental care.  Snakes, lizards and turtles have two-chambered hearts and rarely engage in any form of parental care.  And crocodilians have larger brains than their former reptilian group-mates!

The American Crocodile, like other crocodiles and alligators, guards its eggs throughout the 90-day incubation period from nest robbers such as raccoons, coatis, and ocelots.  It buries its clutch of about 30 eggs in sandy riverbanks – a characteristic shared with other true crocodiles; alligators bury their eggs in mounds of vegetation.  Favorite nesting sites (for example the sandy banks around the Rio Corcovado) may be crowded with the nests of many female American Crocodiles.  Alerted to the guttural grunts of their hatching young, the female will help unearth them, grasp each of them gently in her powerful jaws and carry her hatchlings to a secluded watery hideaway.  The female American Crocodile will then remain in protective care of her young for many months until the last one has dispersed.

American Crocodiles of over 3 meters are potentially dangerous to man.  Although they don’t have the fearsome reputation of the Indo-Pacific Crocodile of Asia and Australia, or the Nile Crocodile of Africa, nevertheless there have been several cases where American Crocodiles have attacked and killed people in Costa Rica.  However, despite their lethal capability large American Crocodiles are for the most part surprisingly timid beasts.  Unless one is foolhardy enough to swim where large crocodiles are known to occur or venture too close to female protecting her nest or young, one need fear little from the American Crocodile.

Crocodilians and their ancestors lived on earth for over 200 million years, and have survived two mass extinctions – the Triassic/Jurassic and the Cretaceous/Tertiary, which put pay to the dinosaurs.  Let us hope the American Crocodile and its relatives, in all their primeval splendor, can survive this, the next mass extinction at the Holocene/Anthropocene boundary, into which the natural world has now entered.


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