Seasonal variations in serum concentrations of testosterone, testicular volume and neck circumference of fallow deer (Dama dama) kept ex situ in a tropical region

Abstract

The fallow deer (Dama dama) is a species of Cervidae commonly kept in captivity, either in commercial farms or in zoos. The reproductive seasonality of this species is well known in the northern hemisphere, where photoperiod is a decisive factor in androgenic activity and, consequently, in the development of secondary sexual characteristics among male adults. The maintenance of this species in tropical regions has been successful, but there are no studies that demonstrate the maintenance of reproductive seasonality under these climatic conditions, which was the objective of the present study. To do so, the present investigation involved 27 fallow deer (D. dama) specimens, of which 14 were adults and 13 prepubescent (<8 months) individuals, all assessed during and outside (December–February) the reproductive season (June–August). The serum concentrations of testosterone, testicular volume, and neck circumference were analyzed among all animals during both seasons. The reproductive season was marked by expressive hormonal concentrations, increasing neck circumference and testicular volume, differing significantly between adults and prepubescent individuals outside the season. Positive correlations were observed among all analyzed variables: mean testicular volume and neck circumference (r = 0.92, p < 0.0001), testicular volume and testosterone concentrations (r = 0.79, p < 0.0001) and between neck circumference and testosterone concentrations (r = 0.67, p < 0.0001). Given the results found, the conclusion is that even under tropical climate conditions the reproductive seasonality of the fallow deer is well defined and may be related to photoperiod.

The Antler Cycle and Fecal Testosterone of Male Sambar Deer Rusa unicolor unicolor at the Horton Plains National Park in Sri Lanka

“…This was followed by the antler casting stage, where the deer cast their antlers either in a fight or hitting against a tree or any other hard structure [29]. The results reported here are similar to previous findings as the fallow deer (Dama dama) stags are recorded with peak fecal testosterone concentrations during November-January [9], while November to January has been identified as the breading season of sambar deer elsewhere in the tropics [2,6].…”

“…Histologically, a substantial reduction, or absence, of germinal epithelium and absence of spermatozoa have been described in testicular atrophy [8]. When it comes to seasonal breeding in deer from temperate regions, the cycle of rutting and related behavior together with growth and casting of antlers is associated with secretion of testosterone by the testis [4,9]. Changes in testosterone concentration, diameter of the testicles and mass of the body have been studied in relation to the antler cycles of such deer stags [9].…”

“…When it comes to seasonal breeding in deer from temperate regions, the cycle of rutting and related behavior together with growth and casting of antlers is associated with secretion of testosterone by the testis [4,9]. Changes in testosterone concentration, diameter of the testicles and mass of the body have been studied in relation to the antler cycles of such deer stags [9]. Thus, it is well established that reproductive steroid levels contribute to reproduction of animals [10].…”

Phenology of Antler Casting and Occurance of Late-Breeding in Nebraska White-Tailed Deer

“…A significant positive correlation has been found between testicular volume and testosterone concentrations of captive fallow deer (Dama dama), and mature males showed higher testosterone levels than younger males outside the reproductive season (Pizzutto et al 2019). During the height of breeding season, it is not unusual for a male's testicles to enlarge, however this condition subsides postbreeding season as testosterone levels drop (Mirarchi et al 1977).…”