[00:00.00]Narrator: Listen to part of a lecture in a Biology class.
[00:03.94]Professor: OK. For today, let's look at a reptile, a predator that hasn't evolved much in the last seventy million years. [00:15.61]No discussion of reptiles would be complete without some mention of crocodiles.
[00:20.64]Now, we tend to think of crocodiles as, uh, kind of solitary, hiding out in a swamp, uh, kind of mysterious creatures. [00:29.75]But we are finding out that they aren't as isolated as they seem. [00:33.61]In fact, crocodiles interact with each other in a variety of ways.[00:38.04]One way is with vocalizations, you know, sounds generated by the animal.[00:43.15]This is true of the whole crocodile family, which includes crocodiles themselves, alligators, etc.
[00:50.09]Take American alligators.[00:52.59] If you were to go to a swamp during the breeding season, you'd hear a chorus of sounds, deep grunts, hisses, these are sounds that male alligators make. [01:03.29]And some of them are powerful enough to make the water vibrate. [01:06.45]This sends a strong, go-away message to the other males. [01:11.01]So the alligator can focus on sending other sound waves through the water, sound waves that you and I couldn't even hear since they are at such low frequency. [01:19.65]But they do reach the female alligator, who then goes to find and mate with the male.
[01:25.56]Vocalization is um...well, it's used for other reasons, like getting attention or just, um... letting others know you are distressed.[01:35.29]Let's see. [01:36.55]New-born crocodiles, or hatchlings and their interactions with their mothers.[01:40.61]When they are born, croc... baby crocodiles have a sort of muffled cry while they are in their nest.[01:47.49]Hatchlings are really vulnerable, especially to birds and small mammals when they are born. [01:53.35]But their mother, who has been keeping vigil nearby, hears their cry for help and carries them to safety, meaning, to water.
[02:01.23]So she takes them out of the nest. [02:03.89]Uh, uh, all the eggs hatched at once, so she has about forty newborns to look after. [02:10.00]Well, she takes about fifteen out of the nest at a time, carrying them in her mouth to the nearby water. [02:16.35]While she is taking one load of hatchlings, the others wait for her to come back. [02:21.24]But do you think they are quiet about it? No way.[02:24.72] They are clamoring for the mother's attention, sort of squeaking and practically saying-don't forget about me!
[02:30.62]I heard some great examples of this on the television program on crocodiles last week.[02:35.28] Anyone catch it? [02:36.46]It had a few interesting bits. [02:38.41]But you know, uh, you have to be careful, think critically. [02:42.87]Sometimes I don't know where these shows find their experts.
[02:50.43]Student: Excuse me. [02:53.59]But, um... does all that crying defeat the purpose? [02:56.36]I mean, doesn't it attract more predators?
[02:59.06]Professor: Hmm...good question. [03:01.41]I guess, well, I am guessing that once the babies have the mother's attention, they are safe. [03:07.28]She's never too far away, and, and I think...I mean, would you mess with a mother crocodile?
[03:17.56]So after the mother transports all the youngsters, they still call to each other, and to their mother.[03:26.44]This communication continues right through to adulthood. [03:29.89]Crocodiles have about eighteen different sounds that they can make.
[03:33.60]There's...um...um… you have deep grunting sounds, hisses, growls, so there are many different sounds to interact or send messages.[03:45.91]This is more typical of mammals than of reptiles. [03:49.24]I mean, crocodiles' brains are the most developed of any reptile.[03:52.70] In that sense, they are closer to mammals' brains than other reptiles' brains. [03:56.79]And we know that mammals, dogs for example, dogs vocalize many different sounds. [04:03.46]Crocodiles have a similar level of, uh, vocal sophistication, if you will, which makes them unique among reptiles.
[04:11.94]Another thing would be, um, if a hatchling gets separated from the rest of its family, once the others get far enough away, its survival instinct kicks in. [04:22.28]It will make a loud distress call, which its siblings answer.[04:26.19] It calls again.[04:27.59] And they continue calling back and forth until they all find each other again.
[04:31.49]Another thing, something that wasn't on that TV show I mentioned.[04:35.85] Um... mother crocodiles lead their young from one area to another, like when they have to find a different source of water. [04:43.69]Usually she will lead them at night, when it is safer for them, moving ahead and then letting out calls of reassurance so that they will follow her.[04:51.69]Her voice helps give the babies the courage they need to leave the area and go someplace that's a more desirable home for them.