×This thesis deals with the nature conservation of reptiles and amphibians in the Netherlands, the present practices and what should be done to improve them. Most of the species of the herpetofauna, as these groups together are known, are in a state of continuing decline. Obviously something is wrong; apart from the role played in this decline by loss of habitat, measures in the field are not effective for the sustainable survival of these species. This thesis has been written to rectify this; based on current knowledge of the ecology of these protected animals and on own experiences with nature management, it is meant to provide a guide and practical tool when carrying out the appropriate measures in the field.
The introduction describes work that has been done internationally, especially at European level, to protect the herpetofauna. Further, how this has influenced policy plans and legislation in the Netherlands. It also points out the shortcomings, both in the approach of the policymakers, as well as in the current training of nature managers, and how these are reflected by the measures taken in the field. This information provides a background for chapter 7, the last chapter of this thesis, where the practice of management is discussed.
The remaining chapters include five articles on ecological research; they also show how much time is needed to improve our knowledge on the ecology of these animals. Also, not understanding it can unwittingly create marginal conditions for a species, as was the case for the Slow-worm and Sand Lizard with the forest management on the Utrechtse Heuvelrug in the 1980s; this is described in the first two articles.
That long-term surveys of population dynamics are more than necessary, is shown by the great fluctuations in the presence and activity of the European tree frog over the six years it was studied in the southwest of the Netherlands. Methodology is also discussed in this third article, and a practical formula given for estimating population size.
Pond characteristics form the subject of the next article, wherein statistical analysis illustrates how they can indicate the possible presence and therefore the suitability of a pond for amphibians. Practical indications are given, useful when constructing new ponds as part of the Pond Action Plans.
The last article has implications for the reintroduction of species into new or former habitats. That there is phenotypic variation within species of amphibians occurring within 200 kilometres of each other, shows that, to avoid failure, this should be taken into account in the selection both of the source population and the location of the habitat into which the animals are to be introduced.
All these aspects are brought together in the final chapter where the practice of the conservation of both groups is discussed in turn. The habitats are the point of departure, and it is shown how conservation measures with plants or landscapes in mind can bring about deterioration or loss of habitat for a particular species of reptile or amphibian. The integration of management goals should be the approach for as far as is possible, but legal obligations may force us to take species specific measures into account for herpetofauna. Heathlands are of utmost importance for reptiles and the most relevant features of the management for this type of habitat are highlighted. For their part, amphibians find their major aquatic habitat in ponds. Details are given of the management for various amphibian species, both in ponds, and as far as we know it, in their habitat on land.
The extensive literature on these subjects, found at the end of Chapters 1 and 7, as well as that of the articles, provides opportunity for going further into depth.
The recommendations from Chapter 7, dealing with the structure of the vegetation to a considerable extent, should improve the situation of the herpetofauna in the Netherlands.
