Integumentary Sense Organs
If you’ve been following our cool croc facts this month you know that crocs have an array of amazing senses. Excellent eyesight on the surface of the water, a phenomenal sense of smell, and hearing that is top of the line in class reptilia. None of these help with hunting their prey underwater though. When crocs submerge, their eyesight is lacking in daytime and nonexistent at night, flaps of skin close the nostrils, and they couldn’t hear a mouse fart let alone hear a fish swimming past them. So how do they hunt fish? Especially in the darker hours which is when most hunting is done...
Integumentary Sense Organs.
All crocodilians have ISO’s around the upper and lower jaw, the nose, and around the eyes. But for gators and caiman, that’s where they end. True crocodiles however have them all over the underneath of the body, down the neck, the belly, the legs, tail and around the cloaca.
The purpose of the ISO’s depends where on the body they’re found. Around the head and jaws they are for detecting prey. Changes in pressure and movement in the water from fish swimming are easily sensed by the ISO’s. Their sensitivity to movement and ability to tell the direction and proximity of prey, mean crocs in water with limited visibility, or even a completely blind croc can hunt with pinpoint precision and snatch up a fish within striking range as quick as we can blink. They’re also incredible sensitive to touch far exceeding the sensitivity of our fingertips and can distinguish easily the difference between what is edible and what is not.
On the body of crocodiles, the function of the obviously present ISO’s is unclear. One possible theory is they are used to secrete cleansing and waterproofing oils. Another theory is that they detect salinity in their aquatic environments, although there has been nothing thus far to prove this hypothesis. One study with juvenile crocodilians suggested the ISO’s on the body acted as a mechanosensory system detecting pressure change and vibrations just as they do on the head, allowing crocodiles to feel with the sensitivity of primates fingertips even with their thick skin and armored body.