The Herpetological Journal

pp.129-136

Authors: R. Hayward, R. S. Oldham, P. J. Watt And S. M. Head

Abstract: Dispersion patterns of different life stages (egg, larva, metamorph and adult) of the great crested newt, Triturus cristatus, were recorded in two adjacent woodland ponds in Oxfordshire, UK. The places along the shores where adult females emerged were significantly different from those where eggs were laid, suggesting that the females do not choose egg sites that correspond with their routes of migration. In the northern pond the distribution patterns of eggs and larvae were very similar. In the southern pond the eggs and larvae were almost entirely restricted to two of the three shores, where they had very similar distribution patterns. Metamorphs emerged from both ponds along the same shores as adult males, suggesting that that they were following directional cues. In laboratory tests, metamorphs showed a significant preference for their own, previously-used substrates over clean substrates, and over those used by other metamorphs. Metamorphs significantly preferred substrates previously used by an adult to clean substrates; the ability to use similar cues to orientate was further indicated by the significant tendency of metamorphs to follow a directional trail left on the substrate by an adult newt in a Y-maze, regardless of whether the adult was male or female. These results suggest that metamorphs can detect cues left by both metamorphs and adult newts and may be able to use them for orientation.

Keywords: dispersion, great crested newts, metamorphs, cues, orientation

pp.137-142

Authors: Robert Jehle

Abstract: '.hirty great crested newts (Triturus cristatus) and 25 marbled newts (T. marmoratus) were rad 10 tracked for up to 31 days after leaving breeding ponds in western France. Around the pond where most newts were radio-tracked, 95% of all summer refuges fell within a radius from the pond of 63.0 m for T. cristatus and 59.5 m for T. marmoratus. The most frequently used habitats were directly adjacent to the pond shoreline. For the other two ponds, all summer refuges fell within radii of between 26.2 m and 32.3 m from the ponds respectively. No significant differences among species or ponds were observed in the mean distance that newts moved away from the breeding site. Five radio-tracked T. cristatus and two radio-tracked T. marmoratus that were moved back into their ponds migrated during the following night in almost identical directions to their initial emigrations, but did not return to the original refuges. Jn eight cases, several (up to ten) untracked newts were found in the refuges of radio-tracked individuals.

Keywords: radio-tracking, terrestrial summer habitat, site fidelity, Triturus cristatus, T. marmoratus

pp.143-155

Authors: R. S. Oldham, J. Keeble, M. J. S. Swan And M. Jeffcote

Abstract: A modification of the Habitat Evaluation Procedure (USFWS, 1976) applied to crested newt habitats is described, using ten key habitat criteria, based upon the assumption that habitat quality determines population size. Seven of these criteria (pond area, permanence, shading and density, macrophyte density, number of waterfowl and terrestrial habitat quality) are assessed using objective habitat measurements, the other three (site geography, water quality and fish occurrence) using qualitative rule-bases, to produce a Habitat Suitability Index for each site. Preliminary validation of the method for a set of 72 sites provides a significant rank correlation between indices of population size and of habitat. The procedure has the potential to provide a simple method of habitat assessment, for site surveying or selection of host sites for translocation, and can be upgraded easily as knowledge of crested newt habitat requirements improves. There was an incidental indication from the validation exercise that the number of newts caught by bottle trapping was affected negatively by the presence of macrophytes.

Keywords: Triturus cristatus, crested newt, habitat suitability index, habitat evaluation, translocation, monitoring

pp.157-163

Authors: Richard A. Griffiths And Clair Williams

Abstract: The effects of pond isolation, drought, habitat fragmentation and dispersal on populations of crested newts (Triturus cristatus) were investigated using stochastic models constructed from existing life history data. The models predict that small isolated populations have a higher risk of extension than large isolated populations. However, even large populations had a relatively high extmct1on risk over a fifty year period if they remained isolated. Pond desiccation affects metamorphic success and recruitment, and the risk of extinction decreased with decreasing frequency of regional droughts. In a subdivided population, increasing dispersal between subpopulations decreased the extinction risk of the metapopulation as a whole. However, even in the absence of dispersal, a subdivided population had a lower overall extinction risk than a single isolated population of the same size. Environmental stochasticity may therefore result in asynchronous dynamics within subpopulations, which leads to the risk of extinction being spread across the subpopulations. Although population viability analysis has the potential to provide an objective assessment of population management decisions, it has not yet been a component of conservation planning for the crested newt in Britain.

Keywords: Triturus cristatus, population viability analysis, metapopulation, modelling

pp.165-171

Authors: A. Kupfer And S. Kneitz

Abstract: Aspects of the population ecology of the great crested newt ( Triturus cristatus) were studied over a period of seven years ( 1989- 1995) in an agricultural landscape of the Drachcnfelser Landchen, south-west of Bonn, Germany. Seven ponds - three natural and four man-made - were monitored by drift fences and pitfall traps. The numbers of adults increased from 1 992. The number of juvenile emigrants showed marked fluctuations between years at all ponds and in some years juvenile production failed completely at the temporary ponds. A total of 63% of the adult newts identified in 1 994 at four sites were recaptured in the subsequent year. Ninety-nine percent of the newts recaptured returned to the place of the first capture. In contrast to the adults, a number of juvenile great crested newts moved to neighbouring ponds, migrating a maximum distance of 860 m within the year of metamorphosis. Two out of four artificially constructed ponds were colonized naturally.

Keywords: population ecology, pond fidelity, dispersal, colonization, Triturus cristatus

pp.173-176

Authors: John M. R. Baker And Tim R. Halliday

Abstract: Variation in dorsal crest morphology and tail height in males of a population of great crested newts (Triturus cristatus) was examined in relation to putative age. Newts were divided into three age classes according to the number of years that they had been recorded in the breeding Population:= first-year breeders, second-year breeders and long-term breeders. Crest morphology differed between the age classes, with a tendency for the crest's teeth to be more irregular in older males. We believe this is the first recorded evidence of age-dependent variation in a sexually selected, morphological character in an amphibian. However, it remains to be tested whether females distinguish between males on the basis of crest morphology. Body size (snout-vent length) and tail height, which is strongly correlated with crest size, also differed between the age groups: body size increased with age and males breeding for the first time had tails that were less tall than those of older animals.

Keywords: great crested newt; Triturus cristatus; crest; sexual selection; age; courtship; behaviour

pp.177-182

Authors: Clive P. Cummins And Mary J. S. Swan

Abstract: Twenty-one late-larval or newly-metamorphosed great crested newts (Triturus cristatus) were implanted with passive transponders (PIT tags) and released into the wild at their natal pond, in England, in 1 996. Body mass at the time of release ranged from 0.69 g to 1.57 g, excluding the tag. Eight of the tagged newts were recaptured as breeding adults in 1999 (5 males, 3 females). Seven of the eight were recaptured again in 2000 (5 males, 2 females), along with four more tagged animals (3 males, I female). The mean annual survival over the four years from tagging and release in 1996 to the breeding season in 2000 was at least 85%. The tagged newts recaptured in 1999 were among the smallest in the breeding population that year, which was consistent with their being the youngest; this interpretation was supported by the appearance of a new group of similar-sized newts the following year. The growth of tagged newts between 1999 and 2000 was consistent with that of the population at large. Overall, we found high mean annual survival and normal rates of growth among great crested newts PIT-tagged at metamorphosis, indicating that the tagging procedure we used was benign. This use of PIT tags, which allow long-term and instant identification of individual animals, provides a means for investigating dispersal, colonization and metapopulation dynamics during the hitherto little studied juvenile phase of the life cycle of this protected species.

Keywords: PIT tags, newt larvae, marking methods, survival, growth

pp.183-190

Authors: R. S. Oldham  And R. N. Humphries

Abstract: Published evidence from 178 great crested newt population translocations in the UK carried out between  1985 and 1994 emphasizes the need for continued monitoring following translocation. In more than half the cases, there was insufficient evidence for judging success, mainly due to lack of monitoring. Using the liberal criterion of the presence of a population one-year following translocation, 37% of all cases were successful and 1 0% unsuccessful. Most of the failures were predictable from existing knowledge of great crested newt requirements. Conflict between development objectives and great crested newt conservation at a site in northern England prompted a large-scale translocation of over 1 OOO individually photographed adults to a conservation area immediately adjacent to the development site. During the first year following translocation, adult newts showed a strong tendency to move towards their previous breeding site, some travelling 500 m in doing so, but none reaching home ponds 900 m away. At least 60% of the translocated newt population either escaped from - or attempted to leave - the conservation area. The remainder accepted the ponds in the conservation area, some of which were less than one year old, and bred successfully. Population sizes were extrapolated from the results of trapping both outside and within the conservation area. The estimated density of adults in the conservation area, at 150 ha·1, was high compared to that in the proposed development site (about 5 ha-1). Nevertheless, in the first year the population in the conservation area showed good production of metamorphs, and mortality consistent with that found in previous studies. Furthermore, most recaptured adults had grown (median of 18% gain in mass) during the season. This was probably the result of the increased habitat diversity in the conservation area, especially the aquatic habitat. It must be recognised that this translocation procedure can be applied only to the adult component of the population.

Keywords: Triturus cristatus, great crested newt, translocation, conservation, population size, survival, site fidelity