New Zealand Frog Reintroductions
Hamilton's Frog (Stephens Island Frog, Leiopelma hamiltoni)
Hamilton's Frog was, until recently, considered to exist on two islands, Stephens Island and Maud Island. However, the two populations have now been divided into separate species based on electrophoresis. Only the Stephens Island form is now considered to be L. hamiltoni, and the Maud Island form is L. pakeka.
Stephens Island Frog Pit (Cook Strait, between North and South Islands). The Stephens Island frogs were only known to occur on a 600 m2 rock bank (called the "Frog Bank"). 12 frogs were translocated to a newly created habitat called the "Frog Pit" in 1992. This new habitat is 72m2 within the nearest remaining forest patch to the frog bank. See Brown (1994).
Nukuwaiata/Inner Chetwode Island (195ha, in the Marlborough Sounds). In 2004, the first translocation of Hamilton’s frog was made from Stephens Island to Nukuwaiata. This translocation was considered a wise move in order to establish a second population but was treated with extreme caution given that the total population is less than 400 adults. The number and age class of this first cohort was determined after analysis of years of monitoring data from Stephens Island and the new site had been shown to be suitable after comparison of temperature and humidity data. Survival of both populations looks promising and a second cohort is due to be moved in mid 2006. From Peter Gaze.
Maud Island Frog (Leiopelma pakeka)
Until recently the Maud Island Frog only occured on Maud Island (Pelorus Sound, Marlborough Sounds, off NE South Island). They were formerly confined to a 15 ha remnant of coastal forest there, but in 1984-95 were translocated to a second location on Maud, from which they seem to be spreading (Bell 1994).
Motuara Island (59 ha, Queen Charlotte Sound, Marlborough Sounds). 300 Leiopelma pakeka were translocated from Maud Island, May 1997, with the aim of establishing L. pakeka on another predator-free off shore island. It isn't known whether L. pakeka occurred on Motuara historically, but its closeness to Maud Island means that this is not unlikely. The island is now predator free following eradication of kiore in 1990, and several species are being reintroduced (also see South Island saddleback, Marlborough green gecko). The collection of 300 individuals ensured a sex ratio and size class frequency similar to that found on Maud Island. Surveys of the translocated population occured every 3 months until December 1998. Juveniles from at least 3 nests were discovered at the release site only 10 months after the transfer. Results indicate the population in the 10 x 10m release grid is declining, due to both emmigration and mortality. Further monitoring will involve searching a larger area and the setting up another 2-3 grids in order to follow the progress of the transferred population. Contact Mandy Tocher or Peter Gaze. See Gaze (1999, Reintroduction News 17: 9-10).
Long Island (142 ha Scenic Reserve, Marlborough Sounds). During the winter of 2005, 100 Maud Island frogs (Leiopelma pakeka) were translocated to Long Island in Queen Charlotte Sound. As with the previous translocation of Leiopelma, a suitable site had been prepared with boardwalks constructed over the boulder substrate allowing monitoring to occur without disturbance to the habitat. Frogs were monitored during the first week following translocation and again in February/March 2006, eight months after the release. Nearly a third of the frogs were recaptured during the Feb/March monitoring trip and these appeared to be in good condition with several gravid females observed. Frogs tended to move in a downhill direction with resightings of individuals at points from 28 cm to 15.5 m away from the frogs' original release sites. Dispersal from the release site did not appear to be related to good habitat as many frogs moved downhill into areas with less dense rock piles. See Germano (2006), contact Jennifer Germano or Peter Gaze.
Karori Wildlife Sanctuary (225 ha mainland restoration area surrounded by a mammal-proof fence, central Wellington, North Island). Reintroduction. 60 frogs were translocated to Karori Wildlife Sanctuary in 2006, 30 mainly female frogs in February and March from Canterbury University where they had been held for research purposes for 3 years, and 30 mainly male frogs directly from Maud Island in October. The reintroduction is part of the restoration program in the sanctuary following eradication of mammals inside the fence (see http://www.sanctuary.org.nz). This is the first reintroduction of the Leiopelma hamiltoni-pakeka group of terrestrial frogs to any mainland site. The frogs have been placed temporarily into two “mouse-proof” enclosures where they have been monitored to assess survival and condition. The frogs transferred in October were screened for chytrid fungus and have been maintained under quarantine conditions in an enclosure separate to the other frogs. In early 2007 frogs from both enclosures will be recaptured and sorted into two experimental regimes – half will be returned to a mouse-proof enclosure and half will be placed into an adjacent rock pile to determine if this species can survive in the presence of mice. This research is being undertaken as a MSc project. Contact Raewyn Empson or Kerri Lukis.
Hochstetter’s Frog (Leiopelma hochstetteri)
Brynderwyn Hills (40 km south of Whangarei). Relocation. Frogs were relocated from a stream that was infilled due to repair of State Highway 1. We searched the 100 m of stream to be affected from 26 October to 7 November 2004, and found 28 frogs. More searching took place in late 2005, after planned repairs to the highway were extended another 20 m downstream due to new cracks being found in the road. We found 25 frogs in 2005, 14 of them were juveniles which is something we didn't get last year (suggesting a significant breeding event the previous year). We were surprised to find so many from a severely degraded stream (we expected 10 max). However, on this search we lifted every rock and ripped apart every log and used nailbars to lever open every crack rather than the usual procedure of only lifting rocks where it doesn’t cause damage. We have moved the frogs to other streams nearby (<500m), and all on the top side of the SH, as all downstream stretches regularly get inundated with floods off the road, oil washing off and debris washing in. After the 2004 relocation, we searched for the frogs 2 weeks and 2 months after release but found none. Therefore the frogs relocated in 2005 will be searched for 3 days after release. If there is no indication that reloated frogs are suriving, we will have to look seriously at other options such as putting them into captivity or using them to try and establish a new population. Transit NZ are planning other works on the hill and every single stream there has frogs in it. Contact Richard Parrish.