Similar But Not That Similar
Alligators and crocodiles are both crocodilians — members of the order Crocodilia — but they are not closely related enough to produce offspring together. They belong to different families: alligators to Alligatoridae, crocodiles to Crocodylidae. These families diverged approximately 80 million years ago — before the extinction of the non-avian dinosaurs. They are about as closely related as dogs and seals.
Why They Cannot Interbreed
Successful interbreeding requires compatible genetics, compatible reproductive behavior, and in most cases geographic overlap. Alligators and crocodiles fail on all three counts. Their chromosome numbers differ, their mating behaviors are species-specific and do not cross, and most species do not share habitat. The American alligator (Alligator mississippiensis) and the American crocodile (Crocodylus acutus) do overlap in southern Florida — the only place in the world where a crocodilian species coexists with an alligator — but there are no documented natural hybrids.
How to Tell Them Apart
The easiest distinction: jaw shape. Alligators have wide, U-shaped snouts; crocodiles have narrower, V-shaped snouts. When an alligator’s mouth is closed, the lower teeth are hidden inside the upper jaw. When a crocodile’s mouth is closed, the large fourth lower tooth remains visible outside the upper jaw — a reliable field identification feature. Crocodiles also have salt-secreting glands on their tongues (visible as small pores); alligators lack functional salt glands, which is why they are restricted to freshwater.
What About Caimans?
Caimans are members of Alligatoridae — the same family as alligators — and are more closely related to alligators than crocodiles are. Even so, no natural alligator-caiman hybrids have been documented. In captivity, some crocodilian hybrids have been produced under controlled conditions (notably Cuban-American crocodile hybrids), but these are rare and typically infertile.
FAQs
Are alligators and crocodiles the same species?
No. They are different families that diverged about 80 million years ago. They share a common crocodilian ancestor but are as different from each other as lions are from hyenas.
Where do alligators and crocodiles coexist?
Only in southern Florida, where the American alligator and American crocodile overlap in habitat. No natural hybrids have been found there.