Is there subtle sexual dimorphism in the colouration of the ear pinna in the pronghorn (Antilocapra americana)?

In previous Posts, I have shown that certain species of Cervidae are sexually dimorphic in the colouration of their ears.

More particularly, mature males tend to lack certain conspicuously pale markings at/near the bases of the ear pinnae (

I have hypothesised that the loss of the markings in question, as males grow from juveniles to adults, may be related to the presence of antlers in males only. The showiness of these head-adornments theoretically eclipses any intraspecific communication via the swivelling movements of the ear pinnae.

Some semblance of this kind of sexual dimorphism may also occur in a few Bovidae. I refer particularly to Kobus kob (, which resembles cervids in that horns are restricted to males.

While scrolling through thousands of photos of the pronghorn (Antilocapra americana), I have come to suspect that the colouration of the ear pinnae of this member of the Antilocapridae is sexually dimorphic.

In this case it is dark, not pale, markings that differ. The tips and margins of the ear pinnae tend

  • to be accentuated by dark, short pelage in females and juveniles, but
  • to lack this accentuation in adult males - in which the dark horns draw attention undistracted by the ear pinnae.

The sexual dimorphism of the head adornments in the pronghorn is limited, because

  • the horns in males are smaller than in cervids of similar body mass, and
  • females, too, possess horns, albeit small and individually variable ones.

Furthermore, in the pronghorn the ear pinnae have a peculiar shape, suggesting a subtle 'mimicry' of horns. The tips are pointed and turned somewhat medially, which gives an impression of 'bracketing' the horns, in a way (

In cervids sympatric with the pronghorn, the anterior surface of the ear pinnae is conspicuously dark-edged in winter pelage. It is possible that a similar seasonal pattern applies to the pronghorn.

With the above in mind, I scrutinised the Web for illustrations of this sexual difference. The results are inconclusive, as follows.

Adult females and juveniles:

Adult males:

Publicado el abril 21, 2024 12:09 MAÑANA por milewski milewski


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