Indicators of ecological change (IEC) as efficient tools for managing roe deer populations: a case study

Abstract

Because of the inaccuracies and biases of population estimates for large herbivores, ‘indicators of ecological change’ (IEC), which allow changes in the animals’ abundance and body condition to be monitored together with ecosystem features, represent an interesting alternative. We used a set of indicators to monitor the relationship between a roe deer (Capreolus capreolus) population and its habitat during a significant increase of hunting pressure in an over-browsed forest of 12.1 km2: the kilometric index, the ovulation rate of adult does, the body mass and jaw length of young and the browsing index. Subsequent to the monitoring results, roe deer density was reduced to a level improving forest regeneration, the animals’ body condition and sustainable game use. Drawing from this successful experience, we caution against a misuse of IEC that could lead to erroneous interpretations. First, the indicators concerning abundance, body condition and impact on the habitat are complementary and necessary to obtain the information needed to efficiently manage populations. Second, managers must consider the values obtained over at least three consecutive years to correctly interpret IEC variations because of their non-linearity and sensitivity to environmental fluctuations.