[totetsu]

They say its a Myth, but then

>"What people see is essentially mass dispersal," said zoologist Gordon Jarrell, an expert in small mammals with the University of Alaska Fairbanks. "Sometimes it's pretty directional. The classic example is in the Scandinavian mountains, where (lemmings) have been dramatically observed. They will come to a body of water and be temporarily stopped, and eventually they'll build up along the shore so dense and they will swim across. If they get wet to the skin, they 're essentially dead."

[optimalsolver]

That sounds like what wilderbeest do before crossing crocodile-infested waters. It's not suicide, they're just trying to get to other side and have no other options.