Evolution of the ungulate dewlap: thermoregulation rather than sexual selection or predator deterrence?

Area of Science:

• Zoology
• Animal Morphology
• Physiology

Background:

• Dewlaps are prominent features in ungulates, but their function is poorly understood.
• Previous research found no link between dewlap size and social status in common elands.
• This suggests sexual selection may not be the main driver of dewlap evolution.

Purpose of the Study:

• To investigate the function of dewlaps in ungulates.
• To test hypotheses regarding signaling and thermoregulation.
• To analyze dewlap function through comparative and intraspecific studies.

Main Methods:

• Interspecific comparative analysis of Bovidae and deer species.
• Intraspecific study of wild eland antelopes (Tragelaphus oryx).
• Analysis of dewlap size in relation to body size, sexual dimorphism, and predation indicators.

Main Results:

• Dewlap presence in males was not correlated with sexual size dimorphism.
• Dewlaps were associated with large male body size (>400 kg), supporting a thermoregulatory role.
• In elands, larger dewlaps correlated with more claw marks, indicating a potential predation cost.

Conclusions:

• Thermoregulation is a likely primary function of ungulate dewlaps.
• This contrasts with proposed functions in lizards and birds.
• Communication may play a secondary role, but is not the primary driver.