1. ¹Department of Zoology, University of Cambridge, Cambridge, UK
2. ²Institute of Zoology, Zoological Society of London, London, UK

Correspondence: Dr EH Boakes, Institute of Zoology, Zoological Society of London, Regent's Park, London NW1 4RY, UK. E-mail: Elizabeth.Boakes@ioz.ac.uk

Received 7 August 2006; Revised 24 October 2006; Accepted 10 November 2006; Published online 20 December 2006.

Abstract

We use regression models to investigate the effects of inbreeding in 119 zoo populations, encompassing 88 species of mammals, birds, reptiles and amphibians. Meta-analyses show that inbreeding depression for neonatal survival was significant across the 119 populations although the severity of inbreeding depression appears to vary among taxa. However, few predictors of a population's response to inbreeding are found reliable. The models are most likely to detect inbreeding depression in large populations, that is, in populations in which their statistical power is maximised. Purging was found to be significant in 14 populations and a significant trend of purging was found across populations. The change in inbreeding depression due to purging averaged across the 119 populations is <1%, however, suggesting that the fitness benefits of purging are rarely appreciable. The study re-emphasises the necessity to avoid inbreeding in captive breeding programmes and shows that purging cannot be relied upon to remove deleterious alleles from zoo populations.