Conservation StatusSub-fossil records indicate there were at least seven species of native frogs in New Zealand before the arrival of people approximately1000 years ago. Habitat change and the introduction of non-native mammals have caused the three largest frog species to become extinct. The remaining four New Zealand frog species all have severely reduced distributions and populations sizes.
Archey’s frog - Critically Endangered
Sub-fossil records and the two remaining disjoint populations (Coromandel Peninsula and Whareorino) suggest the mainland range of this species was once more widespread. A sharp population decline was detected in the late 1990’s and this species is now in critical danger of extinction.
Hamilton’s frog - Critically Endangered
One of the world’s rarest frogs with an estimated population of less than 350 individuals. These frogs survived only in a small rocky area on mammal-free Stephens Island in the Cook Strait. Sub-fossil indicate Hamilton’s frog was once widely distributed throughout the lower North Island and upper South Island.
Maud Island frog - Endangered
Also restricted to a single island in the Marlborough Sounds following the arrival of humans in New Zealand. An estimated 40 000 frogs survive in a remnant of regenerating forest on rodent-free Maud Island.
Hochstetter’s frog - Vulnerable
Ten populations of this species are known in the upper half of the North Island. The fragmented distribution of these populations suggests the distribution of this species has become reduced following the arrival of humans.
The four remaining species of native frogs in New Zealand face a number of threats:
• Non-native mammals
Anecdotal evidence suggests predation and/or competition with non-native mammals may be partially responsible for historical declines of the four extant native frog species. The distribution of frogs on the mainland became restricted following the arrival of non-native mammals and two frog species now survive only on mammal-free island refuges.
While there is a lack of direct evidence to evaluate the exact nature of the effect of non-native mammals on native frogs, ship rats (Rattus rattus) have been documented predating upon Hochstetter’s and Archey’s frogs in North Island forests. Non-native mammals such as pigs and goats can cause severe disturbance and degradation of habitat which may also affect native frogs.
• Habitat change
Historical declines may also be partially attributed to the destruction of forest habitats that followed the arrival of Polynesian and European settlers. Today, Hochstetter’s frog continues to be threatened by localised destruction of stream habitat that occurs as a result of mining, forestry and farming practices.
A chytrid fungus (Batrachochytrium dendrobatidis) has been implicated in the worldwide decline of numerous amphibian species. Frogs infected with this fungus suffer chytridiomycosis, a disease affects amphibian skin and is often fatal. Chytrid zoospores can survive in damp conditions and may be transported between frog populations in muddy clothing and footwear.
This disease was first detected in New Zealand in 1999 in an exotic frog population in Canterbury. It has since been identified in all populations of Archey’s frog in the upper North Island. As a result of infection, one population of Archey’s frog on the Coromandel Peninsula has declined in numbers by over 80% resulting in a ‘Critically Endangered’ listing from the IUCN.
Conservation Action• Translocations
Translocation is a tool used to improve the conservation status of a species. It is the deliberate movement of animals to an area in which they have become locally extinct. All translocations require careful planning to ensure the factors that caused the original population to become locally extinct have been removed or controlled. Translocations also require long term planning and monitoring to assess the outcome and to determine the factors that have influenced success or failure.
Translocations may occur for a number of reasons. While restricted to single locations, Hamilton’s frog and Maud Island frogs were vulnerable to extinction from a stochastic event (fire, disease or invasion by a non-native mammal species). Translocation has been used to mitigate such threats, beginning in 1985 with the intra-island translocation of 100 Maud Island frogs to suitable habitat 500 m away from their original location. In 1997, 300 Maud Island frogs were translocated to a mammal-free island in the Marlborough Sounds. Following the success of this translocation a further 101 frogs were moved to a second island in 2005. Monitoring of all three populations continues today.
Hamilton’s frog was especially vulnerable to extinction with such a small population in a confined area of Stephens Island. The Department of Conservation initially translocated 12 frogs to specially constructed habitat also on Stephens Island. Recently 70 Hamilton’s frog were also translocated to one of the Chetwode Islands in the Cook Strait.
Translocation can also be used to re-introduce a species to an area in which it has become locally extinct to fulfill objectives of restoration projects. In 2006, 60 Maud Island frogs were translocated to Karori Wildlife Sanctuary. Karori Wildlife Sanctuary is a 252 ha restoration project 2 km from Welllington City and is surrounded by an 8.6 km fence that excludes all introduced species of mammals except mice. This translocation is significant because it is the first translocation of a native frog back to the mainland and provides a number of unique research opportunities to gain knowledge on how mice may affect native frog populations.
• Disease management
The Department of Conservation and frog researchers are working hard to reduce the threat of infection by preventing the spread of chytrid fungus. All people visiting areas with frog populations adhere to strict hygiene protocols including not taking packs, bags or gaiters into frog areas, and treating clothing, footwear and research equipment with a biocide known to kill the fungus.
• Control of Predators
The Department of Conservation runs an active predator control programme (more information on this topic will be coming shortly). Check out the DOC Frog web pages.
How you can help with the conservation of New Zealand’s native frogs
If you find a frog that fits the description of a native frog (click here to learn how to differentiate native frogs from introduced frogs) it is important that you do not capture or handle the frog. Take a photograph or make notes about its appearance, its habitat and location. Report your findings to the nearest office of the Department of Conservation as soon as possible or send in a report to NZFROG. You can also donate money to help with frog conservation projects by clicking here.
Remember, all native frogs are protected by the New Zealand Wildlife Management Act. This means it is illegal to collect any native frog from the wild without a permit from the Department of Conservation (see Frogs and the Law)
Native Frog Recovery Group
The Native Frog Recovery Group is an advisory panel of native frog conservation and research experts. The group provides expert advice to the Department of Conservation about the recovery of our threatened native frog species. The group is a mix of university researchers and Department of Conservation staff. It meets annually to advise the Department on native frog research and conservation priorities and progress toward achieving the goals of the Native Frog Recovery Plan.