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Question of the Week / Re: QotW - 09.03.29 - Why are Australian snakes so toxic? (Elapids vs Vipers)
« on: 20/03/2009 04:30:06 »
Chemistry4me thanks for the link...but I didn't agree with much of what was posted there...
Doctor Beaver and Madidus_Scientia thanks for your replies.
Madidus_Scientia >> The water/cost is a point I hadn't thought about...interesting....but many(?) vipers also live in desert regions...with "less concentrated(?)" venom. And also some Elapids not only produce a more toxic venom but they also produce more of it when envenoming their prey....so any water saved by concentrating the venom would be lost by over production....
Doctor Beaver >> prey is comparatively rare in Australia's desert...but up to 50 species of small terrestrial (bite sized) mammals went extinct from these areas due to the introduction of Cats/Foxes/Rabbits and the eradication of Dingoes and Aboriginal people. Rabbits obviously not a direct threat to mammals but huge numbers provided prey base for foxes which ate everything as they spread through the continent....Dingoes and Australian Aboriginal peoples killed and ate cats thus keeping their numbers to a minimum...untill they themselves were killed by white pastoralists... and also it has only been in the last million years or so that Australia has had any deserts...historically its pretty much always been hotter and wetter....Wouldn't this equate to more prey availability thus negating selection for higher venom toxicity?
But on the other hand, most Australian snakes diets contain a relatively high proportion of skinks and amphibians.....both abundant in arid Australia (Yes we have desert frogs...) so the absence of presence/absence of mammals shouldn't matter too much anyway.....!
I think Current distributions of prey density in Australia are very skewed away from what what would have been the norm for much of the time elapidae was evolving in Australia...so I don't think that lower prey density could have been a driving force for the evolution of such a high proportion of highly toxic serpentines in Australia...
Does anyone know of any studies into the efficiency/costs of elapidae vs viperdae venom?
[O8)]
Doctor Beaver and Madidus_Scientia thanks for your replies.
Madidus_Scientia >> The water/cost is a point I hadn't thought about...interesting....but many(?) vipers also live in desert regions...with "less concentrated(?)" venom. And also some Elapids not only produce a more toxic venom but they also produce more of it when envenoming their prey....so any water saved by concentrating the venom would be lost by over production....
Doctor Beaver >> prey is comparatively rare in Australia's desert...but up to 50 species of small terrestrial (bite sized) mammals went extinct from these areas due to the introduction of Cats/Foxes/Rabbits and the eradication of Dingoes and Aboriginal people. Rabbits obviously not a direct threat to mammals but huge numbers provided prey base for foxes which ate everything as they spread through the continent....Dingoes and Australian Aboriginal peoples killed and ate cats thus keeping their numbers to a minimum...untill they themselves were killed by white pastoralists... and also it has only been in the last million years or so that Australia has had any deserts...historically its pretty much always been hotter and wetter....Wouldn't this equate to more prey availability thus negating selection for higher venom toxicity?
But on the other hand, most Australian snakes diets contain a relatively high proportion of skinks and amphibians.....both abundant in arid Australia (Yes we have desert frogs...) so the absence of presence/absence of mammals shouldn't matter too much anyway.....!
I think Current distributions of prey density in Australia are very skewed away from what what would have been the norm for much of the time elapidae was evolving in Australia...so I don't think that lower prey density could have been a driving force for the evolution of such a high proportion of highly toxic serpentines in Australia...
Does anyone know of any studies into the efficiency/costs of elapidae vs viperdae venom?
[O8)]