Although I can imagine this being quite horrific, I also don't recall that this cartoon was all that upsetting me when I watched it as a child. Then again I grew up in the countryside so maybe it was less shocking to me because I already knew what nature was like. When it comes to animal cartoons I think Watership Down and The Plague Dogs were much worse experiences.
Still, kind of makes me wonder what's up with the UK and depressing animal cartoons.