Habitat destruction and its effect on a population of smooth newts Triturus vulgaris: an unfortunate field experiment

Published source details Verrell P.A. (1987) Habitat destruction and its effect on a population of smooth newts Triturus vulgaris: an unfortunate field experiment. The Herpetological Journal, 1, 175-177.
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Summary

In England, several studies have shown that ponds with marginal scrub habitat are more likely to support amphibian populations than those without. Loss of terrestrial habitat surrounding ponds can be detrimental to amphibians which use ponds for breeding. An opportunity to study the effects of removal of marginal vegetation on a population of smooth newts Triturus vulgaris arose when scrub clearance was undertaken around a pond in Buckinghamshire, southern England.

Vegetatation removal: Marginal vegetation (mainly hawthorn Crataegus monogyna) scrub around the northern edge of Cleaver Pond (situated on the Conniburrow housing estate, Milton Keynes), was cleared over winter between the 1985-1986 amphibian breeding seasons to control plant growth and render the site safer when visited by members of the public. Vegetation was cut and removed by the local authority. Prior to this management Cleaver Pond, and nearby Marigold Pond (approximately 400 m away and not subjected to vegetation removal), were subject to physical and biological surveys.

Smooth newt censuses: Night-time censuses were undertaken during the breeding seasons in 1985 and 1986 i.e. before and after the vegetation removal. Commencing in March, two or three visits per week between 19:30 to 11:00 h (starting at or around dusk) were made. In 1985 visits were terminated in mid-June, and in 1986 early July. At Marigold Pond in both years a census consisted of walking around the pond perimeter, scanning the shallower and less-vegetated areas with a spotlight and recording the number of newts observed. At Cleaver Pond with limited access in 1985, only a small area at the western end was accessible due to thick vegetation surrounding the pond elsewhere. During each visit, standing at the western end, the number of newts visible over a 10 minute period was recorded. In 1986, access to Cleaver Pond was greatly improved but the same census technique was employed as in 1985.

From results of ‘before' and ‘after' newt surveys, the consequences of the marginal vegetation removal at Cleaver Pond suggests that this has been detrimental to the newt population. For both ponds the number of smooth newts recorded in 1986 were lower than in 1985. The decrease at Marigold Pond was 30% (cumulative total: 492 in 1985; 346 in 1986). However, the decrease at Cleaver Pond was far higher, estimated at 75% (65 in 1985; 16 in 1986). Additionally torching those parts of Cleaver Pond rendered more accessible in 1986 did not result in a high newt count (23 in total) suggesting that the between-years difference at Cleaver Pond was not due to a change in distribution within the pond.

As well as losing the benefits afforded by the terrestrial vegetation e.g. used as a terrestrial refuge/foraging area, European rabbit Oryctolagus cuniculus burrows known to be used as hibernacula by newts and common toads Bufo bufo, were also destroyed. Additionally, the opening up of Cleaver Pond has allowed greater ease of access and this has probably exacerbated problems of increased disturbance and capture of animals by members of the public.

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