Young Horses Behave Better Around Adults
The age composition of a herd significantly influences how well young horses learn social skills. Observations of wild horses find that when greater numbers of adults are around, yearlings and two-year-olds act less aggressively. Notably, the relative proportions of young and adult horses in a herd figure heavily in how the youngsters behave.
These findings come from a study in southern France of wild Przewalski horses living in five natural family groups of 7 to 12 horses.
Within those herds, the number of horses over three years old relative to those three years or younger varied. In some groups, youngsters outnumbered mature horses, while in others the adults were most numerous. The ratios ranged from two to four adults for every three juveniles. These arrangements are similar to those found in feral bands of domestic horses.
For hours at a time, the researchers made note of every bite, kick, chase and threatening gesture made by individual yearlings and two-year-olds. When the frequency of a young horse's aggressive moves was matched to the age composition of its herd, a striking pattern emerged. Anti-social activities were four times more common in groups where juveniles outnumbered adults, compared with those herds with the highest proportion of adults.
The study also found that when living in a herd dominated by horses under four years of age, young horses stayed segregated from mature horses and bonded more strongly with their peers. The fewer adults there were, the more that young horses avoided mingling with adults.
This study's authors conclude that adult horses play a pivotal role in channelling the aggressive behavior of immature herd mates. But with adult influence depending upon their relative numbers, it varies in how well young horses get taught social skills.
M. Bourjade, A. de Boyer des Roches and M. Hausberger. 2009. Adult-Young Ratio, a Major Factor Regulating Social Behaviour of Young: A Horse Study. PLoS ONE 4(3): e4888.