Introduction

This paper presents data on the demography of populations of European otters Lutra lutra from various parts of the British Isles. The emphasis is on age structure and patterns of mortality.

Otters have declined sharply in Britain over the last few decades, probably largely as a result of contamination by organochlorine pesticides (Mason & Macdonald, 1986; Jefferies, 1989). A similar decline has taken place in many parts of Europe and the species is now extinct in several countries. However, following the withdrawal of a number of pesticides in the UK the otter is now, very slowly, returning to areas from which it had disappeared (Green & Green, 1987; Strachan et al, 1990; Andrews et al, 1992).

A problem that has plagued research on the effects of pollution on populations of otters has been a lack of basic information on demography. In particular, in the absence of animals of known age it has been difficult to answer such pertinent questions as whether or not chemical contaminants accumulate in the bodies of otters as they age. Equally, a knowledge of demographic parameters is important in predicting the rates at which otter populations might recover in the future.

Our aims are:

1. To discuss the methods and associated problems of analysing otter demography.

2. To present data on patterns of mortality and longevity for populations from different areas of the UK.