Effect of sex and age on structural features of nasal calls and body size in fawns of the goitered gazelle, Gazella subgutturosa (Artiodactyla, Bovidae)

Abstract

Male goitered gazelles differ from conspecific females in having a highly prominent larynx. However, the development of sex dimorphism in the vocal apparatus and the structure of calls has not yet been studied in this species. This study deals with structural changes in the acoustic parameters of nasal calls and the body size of goitered gazelle fawns in the course of ontogeny, from birth to 6 months of age. It has been shown that their body weight and neck girth linearly increase with age, while the basic frequency of nasal calls decreases gradually; however, age-related changes in the duration and power parameters of nasal calls are nonlinear. Their basic frequency (94 Hz in males and 118 Hz in females at the age of 2 weeks) is significantly lower than in juveniles of any other ungulate species of comparable size. In fawns of any age group, the index of sexual dimorphism in the basic frequency of nasal calls is at least twice that in the body weight or neck girth, indicating that laryngeal hypertrophy in males is already developed at birth. On the other hand, this index does not increase until the fawns are 6 months old, which is evidence that the accelerated growth of male larynx apparently starts later, in the pubertal period, under the effect of sex hormones.