Interesting. Either that, or maybe your hyenas were adopted before this challenge and therefore the change? When I tested mine I had freshly adopted them from Frontier Zoo.
Nah,more likely the case I didn't notice that the african dogs were breeding and it was their offspring that counted rather than the hyenas. The few hours I played last night I only got 2 baby hyenas and I don't think the number changed .. but whenever the dogs bred which was often the numbers climbed 3 or 4 at a time.