Peacock ‘eyes’ that hypnotize
There’s something about the way a peacock shakes his fan of spectacularly elaborate tail feathers that attracts a peahen’s admiring gaze. It now appears the allure is indeed in the motion, not (as had once been thought) the size of the male’s feathery train, or the number of its colourful eyespots. Researchers using high-speed video found that the tail vibrates at an average frequency of around 26 beats per second. The peacock sustains this for more than 25 minutes at a time.
When the peacock vibrates his tail, it seems those ‘eyes’ can hypnotize the one he is trying to woo.1 When the train is rattled, the vibration of the tail feathers creates a “dynamic iridescent background” around each eyespot.2 The behaviour of the eyespots during tail-shaking is remarkable—not their movement as such, but their apparent non-movement. While feather barbs in the background, even near the eyespots, moved laterally by up to 9.6 mm, the eyespots themselves had a maximum side-to-side movement of just 1.7 mm.
From the peahen’s perspective (typically 1 metre directly in front), the researchers say “the eyespots would appear to be almost stationary” relative to the stunning dynamic iridescence shimmering from the rest of the tail.2 No wonder she’s mesmerized.
But how can the eyespots stay relatively still when the whole tail is shaken vigorously? Scanning electron microscopy revealed that the eyespot feather structure is different. Eyespots are heavier, having densely intermeshed barbules with microhooks,3 enabling eyespot feather barbs to cling together as a single motion-resistant mass. Meanwhile the loose barbs of the background feathers are widely spaced and free to move independently.
Avoiding the logical conclusion of intelligent design, today’s evolutionary storytellers might seek to use this discovery to revive Charles Darwin’s theory of sexual selection for the peacock—that its tail evolved to attract a mate (periodically hotly disputed by evolutionists themselves4). But sexual selection arguments still fall under the fallacy of using biological advantage of a current system as ‘proof’ of a neo-Darwinian origin of that system. The basic problem remains unresolved; such an unwieldy tail would be a huge handicap for the peacock’s escape from predators.
So wouldn’t it be more sensible to realize that this latest tail-rattling discovery seriously rattles the evolutionary tale, too? (For those not totally ‘hypnotized’ by it, of course.)
References and notes
- Secret of how peacocks shake their tail feathers to hypnotise a mate revealed, abc.net.au, 28 April 2016. Return to text.
- Dakin, R., and 4 others, Biomechanics of the peacock’s display: How feather structure and resonance influence multimodal signaling, PLoS ONE 11(4):e0152759, 2016 | doi:10.1371/journal.pone.0152759. Return to text.
- These characteristics are similar to those observed in the primary flight feathers in other bird species, which show strong evidence of design. See, e.g., “‘Microstructural architecture’ of feathers makes them tough”, p. 32 this issue. Return to text.
- See creation.com/peacock2 and creation.com/peacock3. Return to text.