Too many bears (and dens) !
[0.41g/Erebus.py + ErebusContinent.py]
With both the Erebus map and the ErebusContinent map script, I'm getting mostly bears roaming the countryside. Either
A) the animal generation is heavily weighted towards bears, or
B) bears are the only ones building dens, and therefore increasing in numbers.
As I've never seen any Lion or Polar bear dens, I guess it's (B) ...
edit - add:
Giant do not generate a Baby Spider upon eating a living elven scout - at least not at a high enough %age that one would expect from the help text!
Looking at the XML file, the chance is a paltry 5% per combat; combined with may 2-3 Giant Spiders generated on a huge map (never seen more), means that maybe one Baby Spider might be generated per game.
Wolves aren't any better off: With strength 2, they're unlikely to win a combat, and never will win a 2nd one - negligible chance of forming a wolf pack, either.
Now compare that to the bears, which I have seen setting up 3 lairs on a peninsula of ~6x8 squares ...