Re: How can I estimate the population of crocodiles in a wetland area?

Hi Luis,

Thanks for an interesting question. Since I haven't worked with crocodiles myself, I asked a croc researcher friend for his take on your question.

Curator of Herpetology at the Toledo Zoo Andy Odum said that most crocodilian surveys are done at night, and counts are based on "eye shines" which are just what they sound like-- shine a flashlight around the habitat you're surveying, and count how many eyes shine back at you. (be careful)

You'll need to conduct at least three surveys (in succession, if weather permits), so you can run statistical analyses on the counts you get to determine an average, with standard deviation. He lost me on the math part in our quick conversation, but he added that there are several published papers on these methodologies, so you'll be able to find more information in a library literature search on the topic. As is typical in science, the experts don't all agree on techniques, so read a few different articles and decide how to proceed from there.

The idea behind the eye shine surveys is that if you count 50 pairs of eyes one night, 100 the next, and 63 the third night, you can say that for your survey conditions, you know there are at least 100 crocodiles in that area. You can pretty much guarantee you didn't see every individual in the area, so there may well be more than 100 there, but there are at least that many.

I can recommend two great Web sites for more information: The World Conservation Union (IUCN) Crocodile Specialist Group site is a great place for research information, conservation status info, etc.

http://www .flmnh.ufl.edu/natsci/herpetology/crocs.htm

And the University of Florida/Florida Museum of Natural History has a great croc site, complete with my favorite thing: lots of links.

http:/ /www.flmnh.ufl.edu/natsci/herpetology/brittoncrocs/cnhc.html
Have fun counting, and be safe,

Ruth