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The question is pretty simple, why are crocodiles in the America's only restricted Central America and the Caribbean? Why haven't they expanded further south into the Amazon basin? I have heard some theories thrown about that Crocodiles are better adapted to saltwater, but if that were the case then there would be no inland populations of crocodiles in Africa and Asia which is false, and even if the American Crocodile is uniquely evolved for saltwater environments, there shouldn't be anything stopping it from expanding along the South American coast. But even then there is also fresh water crocodiles in South America such as the Ornico crocodile. Other theories suggest that caimans already fill the niche in the Amazon, but caimans also live in Central America and they are able to coexist with the crocodile there.
The question is pretty simple, why are crocodiles in the America's only restricted Central America and the Caribbean? Why haven't they expanded further south into the Amazon basin? I have heard some theories thrown about that Crocodiles are better adapted to saltwater, but if that were the case then there would be no inland populations of crocodiles in Africa and Asia which is false, and even if the American Crocodile is uniquely evolved for saltwater environments, there shouldn't be anything stopping it from expanding along the South American coast. But even then there is also fresh water crocodiles in South America such as the Ornico crocodile. Other theories suggest that caimans already fill the niche in the Amazon, but caimans also live in Central America and they are able to coexist with the crocodile there.
Is there something geographically/climactically specific in https://en.wikipedia.org/wiki/Guyanathat makes it unattractive for crocodile habitat?
Maybe it's the Giant River Otters, whose last and greatest stronghold is the Guianas. Just speculating of course, but my intuition tells me it's because these guys have made the Guianas either unattractive to crocodiles and/or are quick to decimate any nests or young that they find. They are very large apex hunters (the largest of all members of the weasel family) who hunt cooperatively in organized alpha packs (like packs of wolves do) to find and eat caiman and piranhas, so why would they not hunt young crocodiles too? The otter packs are also known to be cooperative with river dolphins on dolphin pack hunts, and river dolphins will kill crocodiles too when they can. So I think it's possible that the otters and dolphins may have / do cooperate with each other to get rid of another carnivorous water dweller like crocodiles that would represent too much competition with them for meat resources. Like I said, it's just a theory.
You can look at it this way. Alligators, caiman, and crocs are all closely related so in reality the crocodile family is represented in the Amazon but as caiman. Caiman and alligators are in the crocodilia order. Whatever crocodiles in recent history made their way to the Amazon were probably out competed by caiman and never succeeded there.
The black caiman is the largest species of the alligator family and the largest predator of the Amazon basin. The length of adult males is approximately 3.5-4 m, and the weight is about 200-300 kg.
Could any of native tribes played a roll in controlling the spread of alligators and crocodiles? With the exception of the larger Black Caiman, most of the caimans are not known to attack humans. Alligators and crocodiles we think of as more aggressive and could be met with aggression to rid an area of a dangerous predator.
I’ve traveled to the Pantanal area of Brazil and trust me, at night, when you shine a light across the water at night and see literally hundreds of eyes looking back at you. Those are all caiman.
In Amazonia, the only natural predator of piranhas are the fresh water dolphins aka pink dolphins. I was in my kayak early, early one morning and several piranhas literally skittering across the top of the water. Behind them was a graceful pair of beautiful pink dolphins, feeding early in the morning light.
There are also tourist-type activities where you can swim in the Rio Negro River and feed the dolphins. Remember, where there are dolphins, there are no piranhas so you’re quite safe.
Over the years, I’ve probably done 20 separate trips to Brazil including the one to the Pantanal and three different trips to the Amazon. One was a typical riverboat from from Belem to Manaus and then, two different riverboat/kayak trip out of Manaus.
One of of those kayak trips, we use small lights to “spot” caiman in the water. The light makes them freeze, more or less. If you can get your kayak beside them, you can grab them just behind the eyes around their neck. Obviously, you don’t want to mess with one unless those eyes are very close together. Lol After I caught one, I place him in a small bag and we went back to our boat.
Once on the boat, I took him out of the bag, laid him on his back and stroked his stomach. He went right to sleep. It’s pretty darn cool.
We also caught a three-toed sloth and her baby. After a few pictures, they were both released unharmed.
I love the Amazon but, you better have a good guide otherwise, you can get into a lot of trouble very quickly. I remember our guide caught an electric elk one night....right where we stepped out of our kayaks at a camping stop. I can’t imagine an ell that size with his bite! OTOH, so many of the trees and plants have medicinal uses which comes in handy when you’re stung by something. It’s a wonderful place!
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