Estimating density of Kirk’s dik‐dik (Madoqua kirkii Günther), impala (Aepyceros melampus Lichtenstein) and common zebra (Equus burchelli Gray) at Mpala,Laikipia District,Kenya

This study compares two methods of estimating the density of three ungulate species: Kirk’s dik‐dik, impala and common zebra, in a dry savannah ecosystem. Fixed strip width and distance sampling involving direct animal counts were used in parallel, and tested for bias and precision in two habitats. Distance sampling was the method that achieved a better balance between accuracy and precision. The differences in sightability of ungulates, according to body size, colour and habitat characteristics, are taken into account by the distance sampling method, but not by the strip method, which produced, what we suspect are, underestimates of animal density.     

The phenotype and frequency of f. medionigra of Panaxia dominula L. (Lepidoptera: Arctiidae) at Cothill, Oxfordshire, England, 1988–1991

New research at Cothill Fen and examination of E. B. Ford's field note-books have revealed much evidence of great variation in the expression of the medionigra form of Panaxia dominula L. Over the years there is a high probability that individual insects have been misclassified. While this casts doubts on the accuracy of the published frequencies of the medionigra form and hence of the medionigra allele, it seems unlikely that the errors will have any serious effect on the interpretations and principles of ecological genetics that the long-term study has revealed. It is clear that both the fore-and hind wings must be examined before a judgement can be made about the phenotype of any individual moth. The new work shows that the medionigra form remains at a low frequency at Cothill. The colony is flourishing, the population size in 1991 being the largest ever recorded.