The odds-on-favorite was the Kemp's Ridley Sea Turtle at 4/5 when I checked today, followed by the Bluefin Tuna at 6/4, then the Leatherback Sea Turtle and the Brown Pelican at 8/1 each.
Hat tip: Richard Black's Earth Watch blog, which added:
I wondered, though, whether species extinctions are a suitable subject for gambling. Isn't inviting people to estimate the relative odds of two species taking the dodo trail in the pursuit of cash just a bit - well - tasteless?
[Paddy Power's] Mr Robertson countered with the opposite notion. It's actually a positive thing for conservation, he said, because punters whose knowledge of the natural world extends to horses and greyhounds might discover a bit more in the process of trying to beat the odds.