Re: Regarding Spinosaurus

["Christopher Lavers" <Chris.Lavers@nottingham.ac.uk>]

>> how many big-bodied, freshwater, warm-blooded,
>>  obligate fisheaters does anyone know of?

>It is certainly possible for a large, warm-blooded, terrestrial predator to 
>support itself on fish, at least for a while, if there are enough fish 
>around.  Many brown bears all around the north Pacific get most (perhaps 
>sometimes all?) of their food intake in the form of salmon during the salmon 
>runs.

Several responses illustrate the interesting difficulties here. In groping for 
a big-bodied, warm-blooded, freshwater, obligate fish-eater, the first thought 
is to turn to the sea for analogues. But oceans and freshwater environments are 
very different places, particularly in terms of connectivity and continuity of 
food supply over ecological and evoultionary timescales. Ditto the point about 
brown bears - during the salmon run, fine, but what about at other times? Are 
freshwaters stable and/or interconnected enough over suitable timescales to 
allow the evolution of big-bodied, warm-blooded, gas-guzzling, 
starve-in-a-month-if-things-go-belly-up, obligate fish-eaters? (I take the 
point about 'obligate' being extreme - useful for speculation though!)

Best to all
Chris