MVSc

The study was carried out at the State Museum and Zoo, Thrissur, Kerala, India for a period of four months from 11th June to 11th October, 2009. There were a total of 70 sambar deer in the enclosure, during the commencement of the study, of which 22 were males including 16 adult stags. A total of 318 hours of observation was involved in the study spanning over four months and each animal received about 53 hours of observation.

Top three stags in the rut stage, on a chronological order of dominance namely H1, H2 and H3 were selected. Three more superior stags in late stages of velvet growth were selected and were named V1, V2 and V3 as per descending order of dominance. Hence, a total of six animals were selected for the study.

Behavioral scores were allotted on the basis of the observations recorded on the ethogram and with the help of a standard score chart. Stag H1 maintained a behavioral score of 42±11.73 during the hard antler phase whereas during the velvet phase it slipped to 9.66±2.25. The behavioral score of stag H2 was 42.85±12.58 during the hard antler stage and it reduced to 12.6±2.3 during the velvet period. Stag H3 had a behavioral score of 44±14 during the rut season; it became 12.6±3.13 during the velvet stage. The behavioral score of stag V1 was 23.16±12.84 during the velvet stage, but as it entered the rut season, its score shot up to 51.81±5.54. Stag V2 had a behavioral score of 24.85±13.83 during the velvet phase, as it shifted to hard antler stage, the score increased to 51.9±5.38. The behavioral score of V3 was 30.33±14.76 during the velvet antler stage, the shift to the rut took up the score to 53.75±4.83.

Fecal testosterone level was measured by RIA on a weekly basis from all six stags. The stag H1 possessed the largest harem followed by H2 and H3 with a membership of 17, 13 and 07 individuals respectively till they retained the hard antlers. As V1, V2 and V3 entered the rut season, V1 collected the largest harem with 19, followed by V3 with 14, and V2 not lagging far behind with 13 members.
The stag H1 maintained a testosterone level of 14.66±2.30 ng g-1 of dry feces when it was in rut stage. The testosterone level after the antler casting in the seventh week maintained a low profile of 7.85± 2.32 ng g-1 of dry. The testosterone level of stag H2 was 14.07±0.54 ng g-1 of dry feces during the hard antler phase and its decline by the eight week led to the antler casting. The testosterone level then was at a level of 9.12± 2.40 ng g-1 of dry feces. Stag H3 had testosterone levels of 14.85±1.17 ng g-1 of dry feces before casting the antler. The casting was followed by testosterone levels of 9.56±1.94 ng g-1 of dry feces.

Stag V1 had testosterone levels of 13.52±1.82 ng g-1 of dry feces in the velvet stage. After velvet shedding, the stag had hormone levels of 18.65±1.20 ng g-1 of dry feces. V2 maintained testosterone levels of 12.45±0.91 ng g-1 of dry feces during the velvet stage. Velvet shedding was accompanied by an increase in testosterone level to 18.77±1.03 ng g-1 of dry feces. The stag V3 had the hormone levels at 12.32±1.18 ng g-1 of dry feces before casting the velvet. The testosterone level after the velvet casting was 18.72±0.79 ng g-1 of dry feces.

The stags in the rut season were found to have a significantly higher testosterone concentration in comparison with the velvet growth stage stags. The study also reveals that, it is the sudden dip in the testosterone concentration which causes the antler casting. Velvet shedding was preceded by an increase in the testosterone levels emphasizing its role. The increasing behavioral scores were also accompanied by higher levels of testosterone.

Statistical analysis to correlate the testosterone levels of all the stags during both hard antler and velvet stage to the behavioral scores showed a significant and positive correlation ( ρ = 0.875, p < 0.01 ). Statistical analysis of the testosterone level and behavioral score during the hard antler stage alone also showed positive and significant correlation ( ρ = 0.791, p < 0.01 ). The correlation between the testosterone level and the behavioral score was significant and positive during the velvet stage as well ( ρ = 0.805, p < 0.01 ).