This is a timely thread for me, as I've recently had reason to wonder at seemingly unorthodox usage of singular and plural forms for animals. A friend of mine is currently living in Kenya, helping run a nature reserve there. From time to time he sends us news in the form of an e-mail newsletter, telling us all about the reserve and the animals in it. Well, I've noticed he tends to use the singular form to speak about the animals, even when mentioning several of them or a group. He'll write "If they feel threatened, lion will chase you", or "we saw a group of hyena and a herd of elephant".

What's this all about? Is this kind of usage, I don't know, more taxonomic - used to speak biologically about the animal species as opposed to individual animals?