Rearing history and levels of abnormal behaviour exhibited by lion-tailed macaques housed in Indian zoos was found to influence their ability to breed. Proven breeders were born in zoos while the non-breeding individuals were confiscated from private owners. Proven breeders also exhibited significantly lower percentages of abnormal behaviour and higher levels of social interactions and autogrooming when compared to the non-breeding macaques. These differences may have been due to non-breeders being housed in isolation and in contact of humans. This could have had an influence on the development of reproductive and social behaviours during the early stages in their lives. (c) 2005 Elsevier B.V. All rights reserved.