Why might an alien species have evolved long, narrow appendages/protuberances that resemble rabbit ears but aren't ears, horns, or antlers?

They attach at the top and/or back and/or sides of the head like rabbit ears. They should extend to a length of 0.5-1 metre and may be rigid or semi-flexible, but not prehensile.

The species is intelligent and tool-using, standing roughly 2.5-3 metres tall. They are a transitional centauroid – two true legs, two true arms, two limbs that can serve either purpose as needed. The species is native to a terrestrial planet not dissimilar to Earth in any significant fashion.

Temperature regulation for the body or the brain seems obvious, but long and narrow wouldn't be as efficient as wide (elephant-like), would it?

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    $\begingroup$ I really don't know what they're designed for but definitely not meant to be manhandled... alright people I know our mom used to do it to drag us around when we are young but this is animal cruelty oh god I wonder who design those things? $\endgroup$ – user6760 Jan 10 '17 at 7:28
  • $\begingroup$ I really have to disagree that this is opinion-based. There are clearly wrong answers (e.g. "wings" or "qi conduits"), and the pool of possible answers relies on a grasp of (or examples from) biology, and is further narrowed by the description provided. It does not meet any of the MetaFilter-sourced examples and clearly meets the "subjective but constructive" requirement further down the page. $\endgroup$ – rek Jan 10 '17 at 20:32

Some Ideas

  • Pheromone distributors and sensors

  • Motion detectors, similar to the otoliths in human ears

  • Sexual selection - the appendages are sexually linked, and play a role in displaying attractiveness to other sexes, like peacock tails do

  • They convey body language during conversation, like humans do with their hands, or dogs do with their tails

  • They are prehensile and cover nearby sensory organs when necessary, in the same way nictitating membranes cover the eyes in times of need

  • They are magnetosensors helping the alien navigate by sensing magnetic fields, like a homing pigeon does

  • They could be vestigial appendages that evolved from whisker-like touch sensors of their ancient ancestors, like moth antennas

  • $\begingroup$ Good suggestions especially about the magnetosensors. It would be easy to go any of your ideas. Plus one. $\endgroup$ – a4android Jan 10 '17 at 6:46

They can be the result of a symbiothic virus, giving the host some benefit in exchange of its "residence permit".

It would resemble what Papillomavirus does in rabbits (with no benefits, besides being referenced in some internet page, in this case)

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