National Geographic : 1999 Jan
Getting a firm scientific grip on our subject calls for a bit of snake wrangling, but first we have to find the anacon das. Sloshing along at water's edge, we poke the mud with poles and with our bare feet, the better to feel snakeskin. This time we got lucky and turned up a tangle of snakes in a breeding ball (left). To date we've examined nearly 800 adult anacondas and taken hundreds of blood samples. Each snake's DNA will help us determine how many males in a breeding ball sire the newborns (bottom middle). We also measured the snakes, the heaviest of which was 215 pounds. One surprising dis covery: Adult females are almost five times bulkier than males, a sexual dimorphism much greater than any other terrestrial vertebrate. Before we release the snakes, we sometimes implant a radio transmitter (bottom right) to track their whereabouts. On a local road we came across a dead female anaconda, and dis secting it we found unfertil ized ova inside (bottom left). We hope our work-a joint effort by the Wildlife Conser vation Society and Vene zuela's wildlife agency, with support from National Geo graphic-will help keep this snake, threatened by the deg radation of its habitat, from losing more ground. OE Biologist JESUS RIVAs is a doctoral candidate at the University of Tennessee, Knoxville. ROBERT CAPUTO, a regular contributor to the GEOGRAPHIC, is based in Washington, D.C .