|
 |
|
Photo: Pady Ryan, Ryan Photographic |
As giant meat-eating lizards began to stomp through the jungles, frightening the life out of their prey, small species of frog already inhabited the planet. New Zealand was then just floating away from Gondwanaland and the frogs, not needing to evolve, didn't. So they sat there with their unique features:
- round rather than slit eyes,
- hatching straight into an almost fully-formed frog instead of tadpoles,
- no external ear drums, and
- not croaking regularly like most other frogs.
Scientists believe that these frogs evolved about 200 million years ago, making them as unique as the tuatara, and the most ancient frog species in the world. They are small, nocturnal, and camouflage themselves well making them very hard to see.
Growing up to 49 mm long this is one of the rarest frogs in the world with a population estimate of about 300 individuals. This species is virtually indistinguishable from the Maud Island frog, but differs by usually being paler. Females tend to be larger than males, but the sexes are otherwise identical
Breeding and Lifecycle
Hamilton's frog lays five to nine terrestrial eggs. The white embryos undergo virtually all their development within the egg and emerge as small frogs, about 11 mm long. Males attend the eggs and hatchlings, which climb onto its back and legs.
Habitat and Distribution
It is only found on a few hundred square metres of rocky ground on the summit of a single islet (Stephens Island) in Cook Strait between New Zealand’s two main islands. A separate population of Hamilton's frog has also been established on its home on Stephens Island and is monitored closely by Department of Conservation staff.
Diet
This frog most certainly eats small insects and other terrestrial arthropods.
Threats to Survival
Native frogs were once spread throughout both the North and South Islands. The four remaining species have declined significantly in range and in numbers, as land has been cleared of forest and predators have been introduced. Frogs are vulnerable to many introduced predators such as rats and cats.
Forestry and agriculture also take a major toll on frog populations and roads and agricultural fields are significant barriers to amphibian’s movement. The apparently safe herbicide "Roundup" is extremely toxic to tadpoles and adult frogs and can cause developmental abnormalities or fatalities. This herbicide is widely used by farmers, foresters and gardeners in New Zealand.
Chytrid fungus was first detected in Canterbury in November 1999, by September 2001 it was detected in frogs in the Coromandel region. The spread of this fungus poses a serious threat to this nationally critical species.
 |
Animal Fact Sheets - Want to learn more about some of Australasia's unique fauna? Take a look at these fact sheets. Great for school projects! |
|
Global Amphibian Extinction Crisis - Find out why our frogs are in trouble. |
|
Regional Education Policy - This policy produced by the education group is a formulation of principles, guidelines and minimum standards for education for the many different sectors involved in zoos, parks and aquaria. |
|
Education Specialist Advisory Group - An overview of ARAZPA and education. Learn about the activities of the ARAZPA Education Specialist Advisory Group. | |