Hamilton's Frog, Maud Island Frog
© 2006 Dr. Paddy Ryan (1 of 12)
Has defensive granular glands in skin, which are concentrated into discrete dorsal patches arranged down the back and sides in about six longitudinal rows. These glandular ridges run along their body from behind the eye; the middle row is the most prominent. The glands are also on the dorsal surface of legs and feet, and to a lesser extent, the arms (Green 1988).
These frogs are very cryptically coloured, relying on camouflage as their main line of defense. Their overall colouration is brown (ranging from light tan to almost black), with black patterning over their backs and faces. They do not have an eardrum. They do not produce loud mating calls, although they can produce a faint squeak when molested. There is no webbing on their feet or hands.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: New Zealand
Terrestrial; can be found in coastal forest and deep boulder banks. Nocturnal; likes to take shelter in damp crevices by day (Gill and Whitaker 1996) and prefers rocky substrates under a full canopy of native trees (Bell 1995).
The Maud Island population (formerly considered L. pakeka) is found on the small, relatively sheltered island of 309 hectares of moderate to steep hill country. Maud Island supports a healthy population of around 19,000 individuals in broadleaf forest.
In 1984-1985, 100 individuals were translocated in two batches from Maud Island to a new site 0.5 km away, also on Maud Island. Recapture studies nearly 20 years later, in 2003, found 70 of the original 100 individual frogs, plus 35 young recruits into the population. Frogs in the earlier batch settled closer to the release site than did those released a year later (Bell et al. 2004).
In 1997, the first island-to-island translocation was carried out, from Maud Island to Motuara Island, which lies 33 km SE in Queen Charlotte Sound (Tocher and Newman 1997; Bell et al. 2004).
Life History, Abundance, Activity, and Special Behaviors
Defense: Can remain motionless for long periods of time. Assumes stiff-legged stance, rearing up and extending the legs (Green 1988).
Reproduction: Sometimes frogs, particularly males, occupy the oviposition sites for weeks or longer prior to the laying of eggs. Takes froglets at least 3 to 4 years to reach maturity. In their development, they have narrow tail fins, and only the base of the forelimbs is covered by the gular fold (Bell 1978).
These frogs prefer cool misty evenings and are particularly active above ground when the temperature is between 8 and 14C. They show considerable site fidelity and tend to stay with a 5m radius for years at a time, as well as to shelter within specific retreat sites (Bell 1994; Bell 1997; Bell 1978). They are very long lived with some individuals being found thirty years after they were marked; an average life expectancy of 33 years has been calculated (B. D. Bell, pers. comm.; Bell et al. 2004).
They are nocturnal and catch their prey by grabbing it with their mouth as they do not flick their tongues out like many other frogs. Although these frogs have never been observed breeding in the wild, Dr Ben Bell of Victoria University has made some observations from an enclosure in his garden (Bell 2002). He discovered that in captivity, frogs lay 1-19 eggs in December in moist depressions under logs, rocks or vegetation. The eggs are guarded by the male and take 14-21 weeks for the eggs to develop. There is no free-swimming tadpole stage and the young climb onto the dorsal surface of the male and continue their development there. During this time they remain fairly inactive.
During tadpole development, the developing forelimbs are large and completely exposed at all larval stages, with only the bases of the forelimb covered by the opercular fold. The tadpole has a ventral mouth but has no oral disc, denticles, or papillae. A large tongue pad is present in the stage 31 embryo. Pigmentation is developed from about stage 33 onwards (Bell and Wassersug 2003).
Trends and Threats
The species remains conservation dependent and strict measures are in place to prevent the spread of any pathogens or predators to the island habitats.
Possible reasons for amphibian decline
General habitat alteration and loss
This species was often thought of as two separate evolutionarily significant units (ESUs) and at most two species, Leiopelma hamiltoni and L. pakeka (e.g., Holyoake et al. 2001), although there was disagreement (Bell et al. 1998). More recently, they are considered a single species (e.g, Thurlow, L.E. 2016 Deducing the phylogeny of New Zealand’s endemic frog genus – Leiopelma. Unpublished MSc Thesis, University of Otago, Dunedin. 136 pp; Burns et al. 2017; Bell and Bishop 2018)
Bel, E.A., and Bell, B.D. (1994). ''Local distribution, habitat, and numbers of the endemic terrestrial frog Leiopelma hamiltoni on Maud Island, New Zealand.'' New Zealand Journal of Zoology, 21, 437-442.
Bell, B. D. (1994). ''A review of the status of New Zealand Leiopelma species (Anura: Leiopelmatidae), including a summary of demographic studies in Coromandel and on Maud Island.'' New Zealand Journal of Zoology, 21, 341-349.
Bell, B. D. (1997). ''Demographic profiles of terrestrial Leiopelma (Anura: Leiopelmatidae) on Maud Island and in Coromandel: growth, home-range, longevity, population trends, survivorship, and translocation. Proceedings of the Society for Research on Amphibians and Reptiles in New Zealand, Abstracts.'' New Zealand Journal of Zoology, 24, 323-324.
Bell, B. D. (2002). Experience of captive breeding the four extant Leiopelma species. Unpublished Report to the Native Frog Recovery Group. Department of Conservation, New Zealand.
Bell, B. D., Daugherty, C. H.. and Hay, J. M. (1998). ''Leiopelma pakeka, n. sp. (Anura: Leiopelmatidae), a cryptic species of frog from Maud Island, New Zealand, and a reassessment of the conservation status of L. hamiltoni from Stephens Island.'' Journal of the Royal Society of New Zealand, 28, 39-54.
Bell, B. D., Pledger, S., and Dewhurst, P. L. (2004). ''The fate of a population of the endemic frog Leiopelma pakeka (Anura: Leiopelmatidae) translocated to restored habitat on Maud Island, New Zealand.'' New Zealand Journal of Zoology, 31, 123-131.
Bell, B. D., and Pledger, S. (2001). ''Estimating population trends in the terrestrial and partly subterranean Maud Island frog Leiopelma pakeka.'' New Zealand Journal of Zoology, 28, 361-362.
Bell, B. D., and Wassersug, R. J. (2003). ''Anatomical features of Leiopelma embryos and larvae: implications for anuran evolution.'' Journal of Morphology, 256, 160-170.
Bell, B.D. (1978). ''Observations on the ecology and reproduction of the New Zealand native frogs.'' Herpetologica, 34, 340-354.
Bell, BD and Bishop PJ (2018). ''Status of Decline and Conservation of Frogs in New Zealand.'' Status of conservation and decline of amphibians : Australia, New Zealand, and Pacific Islands. Heatwole, H and Rowley JL, eds., CSIRO Publishing, Clayton South, Victoria, Australia, 151-165.
Bell, E. (1995). Habitat use, distribution and population dynamics of the Maud Island frog, Leiopelma hamiltoni. Unpublished M. Sc. thesis (Victoria University of Wellington), Wellington, New Zealand.
Gill, B., and Whitaker, T. (1996). New Zealand Frogs and Reptiles. David Bateman Limited, New Zealand.
Green, D. M. (1988). ''Antipredator behavior and skin glands in the New Zealand native frogs, genus Leiopelma.'' New Zealand Journal of Zoology, 15, 39-46.
Hitchmough, R. (2002). New Zealand Threat Classification System lists - 2002. Threatened Species Occasional Publication 23. Department of Conservation, Wellington.
Holyoake, A., Waldman, B., and Gemmell, N. (2001). ''Determining the species status of one of the world's rarest frogs: a conservation dilemma.'' Animal Conservation, 4, 29-35.
Pledger, S. (1999). Monitoring Protocols for Motuara Island Frogs Leiopelma pakeka. Unpublished Report. School of Mathematical Computer Sciences, Victoria University of Wellington, Wellington.
Tocher, M., and Newman, D. (1997). ''Leaps and bounds.'' Forest and Bird, 285, 14-20.
Originally submitted by: Chih Wang, Michelle S. Koo (first posted 2003-04-22)
Comments by: Michelle S. Koo (updated 2021-03-17)
Edited by: Michelle S. Koo (2021-03-17)
Species Account Citation: AmphibiaWeb 2021 Leiopelma hamiltoni: Hamilton's Frog <https://amphibiaweb.org/species/2065> University of California, Berkeley, CA, USA. Accessed May 18, 2021.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 May 2021.
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