Abstract
The social hierarchy of blackbuck plays a crucial role in mate selection and establishment of hierarchy in order to maintain successful reproduction. The factors that influence dominancy have not been yet investigated in the Indian male blackbuck. Here, we investigated the interrelationships between behaviours (aggressive and scent marking), chemical profiles of preorbital gland secretion and faecal testosterone levels in male blackbuck with special reference to dominance hierarchy. The frequency of aggressive behaviour, preorbital gland scent marking behaviour and faecal testosterone level were significantly higher (P < 0.001) in the dominant males than the other males. Among the 43 major volatile compounds identified in the pre-orbital gland posting of dominant and subordinate male Blackbucks, four compounds viz., 2-methyl propanoic acid (I), 2-methyl-4-heptanone (II), 2,7-dimethyl-1-octanol (III) and 1,15-pentadecanediol (IV) were present only in the preorbital gland post of the dominant male during the hierarchy period. The results suggest that male blackbuck preorbital gland marking behaviour is meant to defend the home range or territorial region, and the scent odour suppresses aggression, scent marking, scent production and territorial patrolling of subordinate males. The behavioural expression, level of testosterone and volatile chemical profiles are closely interlinked towards establishment of dominance in the blackbuck. This investigation is the first of its kind to detect establishment of dominance hierarchy based on identification of volatile chemical compounds of preorbital gland and assessment of faecal testosterone in blackbuck.