Sex Differences in Spotted Hyenas

Area of Science:

• Zoology
• Behavioral Ecology
• Mammalian Biology

Background:

• Spotted hyenas display apparent virilization in females, prompting investigation into sex differences.
• Existing research highlights a mosaic of dimorphic traits, some aligning with mammalian norms, others reversed.

Purpose of the Study:

• To review and analyze sex differences in spotted hyena behavior and morphology.
• To understand the evolutionary pressures shaping these unique dimorphic traits.

Main Methods:

• Comparative review of existing literature on spotted hyena behavior and morphology.
• Analysis of documented sex differences in traits such as social dominance, dispersal, and reproduction.

Main Results:

• Spotted hyenas show reversed sex differences in aggression, social dominance, and territory defense compared to other mammals.
• Females are slightly larger as adults, with no differences in neonatal body mass or hunting behavior.
• Early androgen exposure may enhance female aggressiveness, linked to food acquisition.

Conclusions:

• "Masculinized" female traits, particularly aggression, are adaptations for securing food, essential for reproductive success due to high energetic costs.
• Natural selection has modified food-related traits while leaving non-food-related dimorphisms consistent with other mammals.