I recently visited Bahia and saw 2 of these snakes (see photo link). We were about 15km west of Porto Seguro at the Veracel Reserve in the Atlantic Forest. Both snakes that we saw were between 5 and 6 feet in length. One of the snakes was acting very aggressive and swelling its neck and shaking its tail in what we surmised was a defensive tatic.
Our guide at the time said it was a Jararacassu (Bothrops ssp) but in looking at images of that snake, it doesn't really look like it. Any help would be appreciated.

