Strangely enough the coldest locations on earth are swarming with more cold blooded animals than warm blooded ones.
In the artic and antartic the most obviously visible animals might be seals, penguins and other warm blooded animals, but they all depend on cold blooded creatures to keep their warm blooded motors running. Krill (shrimps in the antartic) is one of the most numerous animals on this planet and they are cold blooded and live in a cold sea.
Underneath the ice there is a world filled with cold blooded animals. They easily outnumber the warm blooded ones, since the warm blooded ones need the cold blooded ones to sustain themselves.
Why are the cold blooded ones a succes? Because they do not waste energy like the warm blooded ones. They don't grow fast, but they are efficient. They don't waste enegy heating themselves.