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Re: Venom in Sinornithosaurus



Jura wrote:

--- On Thu, 12/24/09, don ohmes <d_ohmes@yahoo.com> wrote:
Perhaps I used "cursorial" in an inexact manner here, but
on a functional level, snakes are _slow_. They require slow
prey, or some strategy (e.g., venom or ambush) to negate the
speed advantage of (e.g.) a rabbit.

+++++++++++++++++++++++++++++++++++++++++++++++++++++

I think your view of snakes might be a bit skewed (likely due to the greater attention in popular culture that vipers and boas get compared to other snakes), but there are cursorial species. In fact, a large chunk of Serpentes is composed of fast moving species that actively chase after and physically overpower their prey. Part of the reason why one does not typically see elapids, boomslangs, and racers in pet stores is because they are nervous animals that are always moving around. They don't handle captivity well, and are not very "user friendly."

Elapids, boomslangs, and other such species are indeed quite quick (the reason you don't see them in pet stores has more to do with lethality, I think, but that is another issue altogether - certainly the point holds for things like racers, coachwhips, and kin). The thing is, while they are fast, they really don't have particularly high top speeds in a flat out chase - black mambas are often touted as the fastest snakes on earth, with speeds possibly as high as 13 mph - however, that may be an overestimate, as animal speeds are often exaggerated. Even if that figure is accurate, it is slower than a human. The fact is that your average fit adult human can *walk* faster (barely) than an average mid sized colubrid can sprint. Long- bodied snakes with speed-adapted morphologies (which, among other things, involves longer costal muscles) can move darn quick for something that does not have legs, and they can outpace some prey animals, but they appear deceptively fast to us because of rapid turning and high accelerations. To the best of my knowledge, the top speeds of most lizards exceeds that of rapid, arboreal, lizard-eating snakes, for example - however, the extra speed of these snakes certainly helps in ambush, as they can quickly close distance from their hiding location (which sometimes just means dropping from a higher branch). Certainly, the active, sprinting, almost frenetic hunting modes of boomslangs and elapids is different from that seen in vipers and boids, but I'm not sure I'd call an elapid a cursorial pursuit predator. Perhaps it's just a matter of taste.

Cheers,

--Mike Habib