Variation in fecal testosterone hormone concentration with season and harem size in Misaki feral horses.

The research focuses on studying the variations in fecal testosterone hormone levels in relation to season and harem size among feral horses in Misaki peninsula, Japan. The study concludes that fecal testosterone levels can accurately reflect the harem size in wild stallions.

Research Methodology

• Fecal samples were collected monthly, for a year, from 14 Misaki stallions inhabiting Misaki peninsula.
• The fecal testosterone concentrations were measured via radioimmunoassay – a technique used to measure the concentration of specific proteins in a sample.
• The study sought to identify the pattern of fecal testosterone concentration variations over months as well as its relationship with the harem size during breeding and non-breeding season.

Key Findings

• There were significant monthly modifications in fecal testosterone concentration, with levels starting to increase in March and peaking in April at a mean monthly concentration of 2.87 +/- 0.18 ng/g.
• High levels of fecal testosterone were observed until the end of August, after which they began decreasing.
• The study established a significant correlation between fecal testosterone concentrations and the size of the harem for the 14 stallions during both the breeding and non-breeding seasons.

Conclusion

• Based on the results, the researchers concluded that it is possible to use fecal testosterone levels as a reliable marker for harem size among the Misaki stallions.
• The study underlined the significance of fecal testosterone concentration as a powerful indicator for monitoring the endocrine status, particularly relating to reproductive behaviour, in wild stallions.