Conservation status of New Zealand frogs, 2009

Abstract

A reappraisal of the conservation status of the New Zealand frog fauna is presented using the 2008 version of the New Zealand Threat Classification System. Of New Zealand's four extant endemic species, three are judged to be ‘Threatened’ (Leiopelma hamiltoni being ‘Nationally Critical’, and L. pakeka and L. archeyi being ‘Nationally Vulnerable’) and one ‘At Risk’ (L. hochstetteri ‘Declining’). Three Leiopelma species are listed as extinct—they are known from bone deposits in caves throughout the country until some time in the last 1000 years. Three introduced and naturalised Litoria species are abundant in New Zealand although two (L. aurea and L. raniformis) are threatened in their country of origin (Australia). An additional unidentified frog taxon from northern Great Barrier Island is listed as ‘Data Deficient’.     

Genetic variation in the genus Leiopelma and relationships to other primitive frogs

Allozyme variation was studied the three living species of Leiopelma. L. hamiltoni and L. archeyi are shown to be closely related to each other although L. hamiltoni is slightly more divergent relative to L. hochstetteri. This parallels previous cytoenetic data. The rarity and insularity of L. hamiltoni enables the calculation of a mutation rate based on genetic variance and population size. A mutation rate per generation of 2.7times 10^--⁶ is sufficient to account for the observed levels of variation. Six populations of L. hochstetteri show a pattern of genetic divergence that also closely parallels previously detected cytogenetic variation. L. hochstetteri is genetically distant from its congeneric species while all species of Leiopelma are at an extreme genetic distance from Ascaphus truei, the only other living amphicoelous fro At the limits of resolution of the allozme technique, Ascaphus clusters with the more morphologically advanced frogs, Discogiossus and Bombina, rather than with Leiopelma. Taken with other evidence, this supports recognition of two families, Leiopelmatidae anl Ascaphidae, with Leiopelma the probable sister group of all other frogs.     

The formulation of a national strategy for biological control of possums and bovine Tb

Abstract

The Government has designated the control of possums and bovine Tb a National Science Strategy (NSS) research area. An NSS Committee has been appointed by the Ministry of Research Science and Technology, commissioned to “identify, coordinate and promote national priorities for possum and tuberculosis (Mycobacterium bovis) related research in order that threats both to New Zealand's export markets and to conservation values can be eliminated”.     

Hochstetter's frog (Leiopelma hochstetteri) egg,mobile larvae and froglet development

Egg strings and larvae of Hochstetter's frog (Leiopelma hochstetteri) were located at three widely separated North Island sites: in seeps at Brynderwyns in December 2004, in an open pool at Wharerino in March 2009, and in an underground pool near the Kaipawa Track, Coromandel, in late May 2009. Ten egg strings were also laid by captive frogs in water courses at Hamilton Zoo in April 2009. All egg strings held from 11 to 13 eggs. The egg strings laid in the Brynderwyns were regularly observed until metamorphosis was completed in March 2005. Twenty-four swimming larvae emerged from 25 capsules at c. 40 days after discovery, and at least 14 froglets were produced at c. 90 days. All of them developed in darkness, in a 120 ml pool <30 mm deep. The emerged froglets ranged from 9.8 to 10.8 mm snout-vent length. The detection of eggs, larvae and <11 mm froglets indicates that the egg laying period is at least from late September to May.     

The taxonomic identity of a population of terrestrial Leiopelma (Anura: Leiopelmatidae) recently discovered in the northern king country,New Zealand

Abstract

A terrestrial endemic frog resembling Leiopelma archeyi was discovered in the Whareorino Forest, northern King Country, New Zealand, in 1991, where it is broadly sympatric with L. hochstetteri. To clarify its taxonomic status, allozyme electrophoresis of toe tissue was used to compare it genetically with four other populations of terrestrial Leiopelma (L. archeyi from Tapu and Tokatea, Coromandel; L. hamiltoni from Stephens Island; L. pakeka from Maud Island). Thirteen presumed genetic (allozyme) loci could be consistently scored for the five populations. At 11 loci, no genetic differences were found between the Whareorino frog and the two Coromandel L. archeyi populations. Allelic frequencies differed slightly at two loci. We therefore conclude that the terrestrial Whareorino frog represents a western population of L. archeyi. L. hamiltoni from Stephens Island is genetically closer to L. archeyi than is L. pakeka from Maud Island. The Whareorino L. archeyi population is morphologically similar to Coromandel L. archeyi populations, although multivariate analysis suggests subtle morphological differences, including the relative position of the nostril. Size comparisons between Whareorino and three Coromandel sites (Moehau, Tapu, Tokatea) show there were more larger frogs (35–38 mm snout‐vent length) at Whareorino and Tokatea compared with Moehau and Tapu, where maximum snout‐vent lengths were 34 and 36 mm, respectively.     

Historical trends in frog populations in New Zealand based on public perceptions

Surveys were distributed to New Zealand land users in 1998 and 2008 to acquire information about New Zealand frogs with the aim of compiling and mapping their distribution and inferred population trends without costly and time-consuming field surveys. The overall frog population trend was reported as declining, with possible causes reported as an increase in agriculture, an increase in the distribution of predatory fish and disease. The resultant maps could be used for four main purposes: 1) to identify regions where Litoria populations are known to occur, which can be eliminated when considering suitable regions for translocation of Leiopelma; 2) to identify growing or stable populations of Litoria species, which may assist future disease surveys, population monitoring and to identify sources of genetic material that may serve as an Ark for declining Australian populations; 3) to highlight populations that are in decline to enable effective targeting of detailed disease studies; and 4) to approximate the stability of amphibian populations in the absence of more accurate, but costly, scientific monitoring.     

Habitat distribution and predation on a western population of terrestrial Leiopelma (Anura: Leiopelmatidae) in the northern King Country,New Zealand

Abstract

A new population of terrestrial Leiopel‐matid frog was discovered in the Whareorino Forest, northern King Country, New Zealand, in 1991. Searches were carried out from June 1991 to December 1993 to determine the species present and to document variation in external morphology, habitat, and local distribution. These confirmed that a terrestrial frog resembling L. archeyi is present in the area, as well as Hochstetter's frog Leiopelma hochstetteri and the introduced Australian hylid frog Litoria aurea.

In Whareorino Forest, the terrestrial Leiopelma was mostly above 500 m altitude and L. hochstetteri above 350 m. The terrestrial Leiopelma occupies sites under rocks and logs in forest. It also occurs in vegetation, such as crown fern Blechnum discolor, tree fern Cyathea smithii, hook grass Uncinia uncinata, and rice grass Microlaena avenacea. Egg clusters of this frog were found in crown fern and tree fern, as well as under stones.

The terrestrial Leiopelma is susceptible to predation by Litoria aurea and rats. This is the first documented evidence of predation on Leiopelma on the New Zealand mainland. The future of this small remnant Leiopelma population is uncertain, and further investigation of the impact of anuran and mammalian predators is needed.     

Characterisation (δ13C and δ15N isotopes) of the food webs in a New Zealand stream in the Waitakere Ranges,with emphasis on the trophic level of the endemic frog Leiopelma hochstetteri

Abstract

Leiopelma hochstetteri, the most widespread of New Zealand's native frogs, is recognised as threatened, and is fully protected by legislation. As a first step to characterise the diet and trophic level of L. hochstetteri within streams in the Waitakere Ranges, Auckland, stable carbon and nitrogen isotope analyses were undertaken on a variety of sympatric terrestrial and aquatic plant and animal species, including adult frogs. These results show that: (1) aquatic and terrestrial food webs are linked by terrestrial inputs into the stream; (2) invertebrate and vertebrate predators separate well into distinct trophic groups, and (3) L. hochstetteri occupies an intermediate trophic position among predators, with a diet, at least as an adult, comprising terrestrial invertebrates. Shortfin eels and banded kokopu are identified as potential predators of L. hochstetteri, but data for rats are inconclusive. These results have important implications for the conservation of New Zealand native frog species and riparian stream habitat.     

Lipid levels in the South Island pied oystercatcher (Haematopus ostralegus finschi)

Wing lengths and some major body components were compared among the sexes and age classes of a sample of 48 South Island pied oystercatchers (Haematopus ostralegus finschi). Immature males were significantly lighter in wet weight and fat‐free weight than either immature females or adults, and were significantly lighter than adults in lean dry weight. No statistical differences were found in wing length, total lipids, or fat measure for birds in this sample. In a larger sample of 182 birds, fat measure varied similarly in the age classes, from a low in autumn to a peak in spring just before vernal migration. Massive pre‐migratory fattening typical of many small passerines does not occur in this species, but even so the average fat reserves in spring adults are sufficient for an approximate flight range of 2140 km, well in excess of need. It is hypothesised that the amount of fat deposited before vernal migration is a compromise between the energy cost of acquiring and transporting extra fat and the advantages of arrival at the breeding grounds with sufficient fat reserves for early achievement of breeding condition.