We were disappointed not to see more wildlife. The Circuit is somewhat lifeless, being a desolate volcanic wasteland and all.
It is a bit of a thrill to come across a bird, unusual insect or surprising flower in the lava.
Other things to do near the Circuit?
Tongariro is a World Heritage cite for both natural uniqueness & on cultural grounds; it is sacred to the indigenous Maori people.
You might:
visit Taupo
golf Whakapapa
visit National Park town
ski or hike Mt Ruapehu
e.g. Round-the-Mountain Track (4-5 days)
travel to Rotorura
The Taupo Volcanic zone is perhaps the best tourist destination in New Zealand. There is much to do here & it is central to other attractions on the North Island.