Hamilton's frog

Species of amphibian
speciesbox
| name = Hamilton's frog
| image = Leiopelma hamiltoni02. jpg
| status = VU
| status system = IUCN3.1
| status ref = The male remains with the eggs to protect them and allows the tadpoles to climb onto his back where they are kept moist. It is named in honour of Harold Hamilton the collector of the type specimen. The holotype is in the collection of the Museum of New Zealand Te Papa Tongarewa. There is no webbing between the hind toes, and the fingers are not webbed. These frogs have a snout length of 5.5 mm, and thighs that can reach up to 14.8 mm. Leiopelma hamiltoni is a very small frog species, with males being even smaller than females. Males have a snout vent length of up to 43 millimeters and up to 49 millimeters for females. They are typically a brown color which can range from very light brown to almost black. Some have also been spotted having a green color. They also have black spots covering their bodies. Unlike other frogs, they have very little to no webbing on their hind toes and also do not have external eardrums. They have a row like design down the back and sides of their body which are made up of callus like glands in their skin. This coloration allows the frogs to blend in well with their surroundings. These rows start right at the back side of the eye, with the middle row being the largest and most distinct. The end of this middle row terminates at what scientists called the paratoid gland. The lines are also seen on the legs, feet, and arms but are less prominent than the ones on its back.

Hamilton's frog live only on a small rocky area on mammal free Stephens Island in the Cook Strait. Sub fossils indicate Hamilton's frog once lived throughout the lower North Island and upper South Island. They live around rocky, moist and grassy areas. However, fossils show that the species may have previously had a larger range, with fossils being found scattered all over New Zealand. Remains have been found at Waitoma, Hawkes Bay, and Wairarapa, which are all located on the North Island of New Zealand. Much of the island has been modified due to farming, forcing all the frogs to live in the same section of rainforest that remains. This species typically live very closely to one another which would signal socialith. However, since their habitats have become so small, it is unclear whether they do this for social reasons or simply because there is not much space to spread out. Leiopelma hamiltoni also live for an extremely long time, compared to other frog species. Tagged frogs had been found to have lived up to 30 years after their initial tagging. Scientists have estimated that their likely life span is around 23–33 years. They also have unique hunting habits, as they catch their prey by catching it directly with their mouths, rather than with their tongues.

Hamilton's frog is a nocturnal ground dwelling species. There is growing observational evidence that it may live in some trees as well.

The Hamilton's frog are insectivores. They feed on fruit flies, small crickets, moths, and springtails. Juveniles with a snout vent length of 20 mm or less lack teeth, and thus are required to eat soft bodied arthropods like mites and fruit flies. Leiopelma hamiltoni are insectivores and feed solely on insects, including crickets, flies, moths, springtails, and other small bugs. Their tongs are stuck to the top of their mouths, so they are unable to catch insects with their tongue like many other frog species do. Instead they have to catch prey with their mouths directly. Younger frogs have to eat small insects as they have smaller mouths with fewer teeth, so young Hamilton Frogs tend to eat mites and fruit flies.

Females can lay between 11 and 15 eggs, which tend to be 9.6 9.6 mm in length. The parents, but usually the males, will often seek out and find the site where they want to lay their eggs. They will then occupy and guard the site where they will lay eggs for weeks or sometimes months before the eggs are even fertilized. The species on Maud Island will typically lay their eggs in December each year. Once the eggs are laid, the male will stay with them, protecting them from any potential predators. The eggs take between 7–9 weeks to fully develop and hatch. Once they hatch, they do not immediately start swimming like most tadpole frog species. Instead, they climb onto their father's back and stay with him while they continue to develop there. They are very inactive while they are with the father, as he carries them around everywhere. After the frogs hatch, it takes them around 3–4 years to reach full maturity. During their development they have narrow fin tails and their hindlimbs develop first. Only their forelimbs are covered by the gular fold. This was determined in a 2002 study done where any other sensory signal was eliminated, so chemical signaling was the only response to the frogs’ behavior.

Farming and deforestation on Maud Island has destroyed much of the land that the frogs used to live on, however they have managed to keep a stable number on their own in the cluster of land that they currently reside in. The frogs on Stephans Island are endangered however. They are at risk due to increase in predators, as species like the black rat have been introduced to the island. Much of their forest has also been destroyed, so they do not have much space to exist.

New Zealand has been protecting the Hamilton's frog species since 1921. A tuatara fence has also been built to stop tuataras from getting through. There is population monitoring also in place. There are plans to move some of the population to another island.