This series is documented to match the episode list from the original broadcaster, BBC One; here

BBC America rebroadcast the show and added an episode according to the show's web site here

There are 2 differences:

1. - BBC America lists the Meerkat episode as S02E05, while BBC One lists Meerkat as a special
2. - BBC America broadcast an episode that isn't on the BBC One site, Macaque

It seems appropriate to leave the Meerkat episode as is to match the original episode order, but how should we handle the new Macaque episode?

For now, I've added the Meerkat episode as an episode in the Specials season.