Hochstetter’s frog (Leiopelma hochstetteri) lives in forested ranges from Northland (south of Whāngārei) to East Cape, usually alongside streams.
The frogs are brown or greenish, with partial webbing on the hind toes. Females grow to 4.7 centimetres (from snout to vent) while males reach 3.8 centimetres. The total population is unknown.
There are two main groups of this North Island species (Leiopelma archeyi) – one in Coromandel and the other in the Whareorino Forest, west of Te Kuiti. Archey’s frog is slim, with a glandular ridge running backwards from the eye. Colour is variable and ranges from mainly green (rarely) through combinations of green and brown to mainly brown. Some Whareorino specimens may be quite brightly coloured, with pinks and brick reds against the background colour.
The male body length is up to 3.1 centimetres and the female 3.7 centimetres. The total wild population is unknown but is almost certainly decreasing, in part because of the introduced chytrid fungus disease.
This species (Leiopelma hamiltoni) is known only from Stephens Island in Cook Strait, where it is found in only two small areas. It is mainly brown, but juveniles are sometimes greenish.
It is similar in appearance to Archey’s frog, with a glandular ridge running from the eye, but on average Hamilton’s frog is larger. These are the largest native frogs, with males up to 4.3 centimetres long and females up to 5 centimetres. The total population may be fewer than 300 individuals.
Maud Island frog
Females may reach 4.9 centimetres in length, and males slightly less. They are long-lived – one survived at least 29 years. The Maud Island population is estimated at over 10,000 frogs.
Based on measurement and appearance, the Maud Island frog is identical to Hamilton’s frog. But in 1998 it was described as a new species, Leiopelma pakeka, because of genetic differences. More recent study based on mitochondrial DNA has questioned this, and it is possible the two frog groups will once again be treated as one species.
Even so, the fact that Maud Island and Hamilton’s frogs live on separate islands means that over time they are evolving differently. From a conservation point of view, two separate populations, with some genetic differences, should be managed as if they are different species, because such diversity is valued.