Frog (Hamilton's frog) Leiopelma hamiltoni
Species: L. hamiltoni
Binomial name: Leiopelma hamiltoni
Common name: Hamiltons frog, Hamilton frog
Leiopelma hamiltoni is a frog native to New Zealand. It is one of the rarest and most primitive frogs in the world. Its natural range is a 600 m sq. boulder bank near the summit of the mammal-free Stephens Island in Cook Strait. It is one of the smallest known habitats for any frog species in the world.
Leiopelma hamiltoni is a small species, with males reaching a total length of up to 43 mm and females being larger at 52 mm. Despite its small size it is New Zealand’s largest native frog. They are mostly light brown in colour, although some green individuals have also been observed. A single dark stripe runs along each side of the head and through the eye. Defensive granular glands are present in the skin, which are concentrated into discrete patches arranged down the back and sides in about six long rows from head to rear, with the middle row being the most prominent. Glands are visible on the upper surface of the legs and feet, and to a lesser extent, the arms. There is no, or very little, webbing between the hind toes, and the fingers are not webbed.
Hamilton’s frog, like all other native New Zealand frogs, does not exhibit a breeding call. This is because they are a primitive frog species that do not possess vocal chords or eardrums. However, they are known to squeak or chirp when annoyed, distressed, or during sexual activity. Because of the absence of well developed vocal sac, the sounds they produce depend upon resonance frequencies in head and body, rather than the vibration frequency of vocal chords.
Leiopelma hamiltoni are a nocturnal ground dwelling species that hides during the day in damp, mossy rock crevices. They are insectivores and at night feed on fruit flies, small crickets, moths, and springtails. Juvenile frogs have a snout-vent length of about 20 mm and have no teeth, and thus they are required to eat soft-bodied arthropods like mites and fruit flies.
Leiopelma hamiltoni young do not go through a tadpole stage, instead they develop totally within a gelatinous capsule in the egg, hatching out as froglets. They take around three years to reach maturity. The male that has protected the eggs allows the froglets to climb onto his back where they are kept moist.
The Department of Conservation (DOC) has classified the Hamilton's frog as Nationally Critical under the New Zealand Threat Classification System.
The red square is the position of Stephens Island
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