Reduction of the labial and mandibular vibrissae as part of extreme adaptation to anti-parasite grooming in impalas (Aepyceros), part 1

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Please see https://pupford.com/why-dogs-have-whiskers/ and https://en.wikipedia.org/wiki/Whiskers and http://www.scholarpedia.org/article/Vibrissal_behavior_and_function.

It is known that impalas (Aepyceros)

are extremely committed to anti-parasite grooming (https://www.sciencedirect.com/science/article/abs/pii/0031938495021868 and https://www.researchgate.net/publication/227316644_Role_of_sex_and_breeding_status_in_grooming_and_total_tick_load_of_impala and https://www.researchgate.net/publication/263375627_Self_grooming_in_impala_mothers_and_lambs_testing_the_body_size_and_tick_challenge_principles), and
allogroom particularly frequently for ruminants (https://www.sciencedirect.com/science/article/abs/pii/S0003347205803197#:~:text=Adult%20female%20and%20male%20impala,to%20the%20head%20and%20neck. and https://psycnet.apa.org/record/1993-24594-001 and https://psycnet.apa.org/record/1997-07057-005).

The anatomical structure seen as particularly adapted for grooming is a small toothcomb on each side (left and right), consisting of mandibular incisors and a canine (https://www.newscientist.com/article/mg14018992-900-science-impalas-wobbly-teeth-get-to-grips-with-ticks/ and https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1993.tb05361.x and https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.1993.tb05361.x).

The following are particularly clear illustrations of the 'toothcomb' of Aepyceros melampus, which consists of a narrow incisor (mandibular incisor 2), two needle-like teeth with loose bases (mandibular incisor 3 and the mandibular canine), and a cone-like gingival papilla (https://www.inaturalist.org/observations/178533731 and https://www.alamy.com/stock-photo-a-tender-moment-shared-by-two-female-impala-32019187.html?imageid=4D457A53-C732-4EA3-9D77-EDF2ABD5E672&p=4989&pn=1&searchId=e623827709c92224586328b59a115995&searchtype=0 and https://sketchfab.com/3d-models/impala-skull-ef9b723f33ea4aa59591c277dfdf5a20).

The above photos show that incisor 3 and the canine are so narrow (and flexibly attached to the jaw) that they are specialised for combing pelage rather than for foraging.

However, what seems to have been overlooked is that, in anatomical terms, the vibrissae on the lips and chin may be more extremely adapted than are the teeth.

A NEW SEARCH-IMAGE

It makes sense that the labial and mandibular vibrissae have been reduced in impalas.

The lips and chin of most ruminants are sensitive to the three-dimensional arrangement of objects in the environment. This aids foraging, particularly in darkness.

However, such sensitivity would be disconcerting during the rubbingly intimate, time-consuming actions of allogrooming by means of small front teeth. Furthermore, impalas tend not to forage at night.

Reduction of the labial and mandibular vibrissae as part of extreme adaptation to anti-parasite grooming in impalas (Aepyceros), part 1

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