Body scarring as an indicator of social function of dugong (Dugong dugon) tusks

The fully aquatic lifestyle of dugongs means that direct observation of social tusk use is not usually possible. This study used body scarring as an indicator of tusk function by males. Tusk rake scars on 298 live wild dugongs, of both sexes and all sizes, were categorized and counted in over 1,000 photographs, and examined in relation to maturity and reproductive activity over seasons. All dugongs had tusk scars, but adults were the main recipients. Sexually active adults acquired the greatest number of fresh tusk wounds during the mating season. Subadults received fresh rakes at similar numbers year-round. Adult males had more scars on the mid and posterior dorsum, indicating that males direct combative force to these regions of the male body when competing for females. Adult females had heaviest scarring and more tusk puncture wounds on the anterior-mid dorsum and head, suggesting that male dugongs use tusks in sexual coercion. Heavy scarring sustained by solitary calves compared to dependent ones, suggests that mothers afford some protection. Body scarring caused by tusks may serve as an indicator of reproductive contribution of the recipients, providing that successful males are involved in more reproductive competitions, and successful females in more mating events.

Automated summary

The body scarring caused by tusks can indicate the reproductive contribution of recipients, with successful males involved in more reproductive competitions and successful females in more mating events. Adult males direct combative force to specific regions of the body when competing for females, while adult females sustain heavier scarring and tusk puncture wounds, suggesting male dugongs use tusks in sexual coercion. The study showed that tusk rake scars were present in all dugongs, with sexually active adults acquiring the most fresh tusk wounds during the mating season.