Thank you Mo and Azizi.
I think the Boa Constrictor rhyme is from Spike Milligan - but I'd have to take a look in our files. It was in several Australian school-songbooks in the 1970s.

We played "What's the Time Mr Wolf" here in Australia during the 1950s. My children played it in the 1960s-70s. It's still played in Western Victoria today. Although foxes are well known here and wolves are not, I've always thought that the idea of using a wolf comes from a deep-seated fear of this animal that comes to us from our ancestors. In the European culture of my ancestors the fox is clever and tricky, but the wolf is dangerous and scary. Children tend to favour dangerous and scary in the playground.

It's a very basic game isn't it? Every man/woman/child for himself/herself and the wolf against everyone. I never liked it but I understand it's appeal.
Cheers, Joy