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Travellers to Śląsk-Opolskie beware - pumas on the loose [83]
Sorry, language is changing and I'm here to point that out. You will find 'deers' in some dictionaries. Some things change over time. For example, fish can be fishes and I've heard native speakers use it that way. English is so broad and flexible and if I write it naturally without feeling it as an error, it's probably right (without sounding smug I hope).
Next you'll be telling me that you spell humour as humor ;) ;) ;)
Go and check it in WikiAnswers.com, ask What do you call a deer in plural? I think you'll find the percentage answer quite staggering.
I know the consensus opinion but we don't have to stick to Stone-age traditions. I'd generally prefer deer as the plural as that's what I was taught. Then again, I don't always go with what I was taught :) :)