Kinematics of chisel-tooth digging by African mole-rats

Mole-rats are known to use their protruding, chisel-like incisors to dig underground networks of tunnels, but it remains unknown how these incisors are used to break and displace the soil. Theoretically, different excavation strategies can be used. Mole-rats could either use their head depressor mus...

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Bibliographic Details
Published in:Journal of Experimental Biology
Main Authors: Van Wassenbergh, Sam, Heindryckx, Stef, Adriaens, Dominique
Format: Article in Journal/Newspaper
Language:English
Published: 2017
Subjects:
Biology and Life Sciences
Rodentia
Bathyergidae
Teeth
Incisors
Biomechanics
COMPARATIVE FUNCTIONAL-MORPHOLOGY
RODENTS TACHYORYCTES-SPLENDENS
HETEROCEPHALUS-GLABER
CRYPTOMYS-DAMARENSIS
RATTUS-RATTUS
HEAD MUSCLES
PATTERNS
EVOLUTION
MOVEMENT
Rattus rattus
Online Access:https://biblio.ugent.be/publication/8542993
http://hdl.handle.net/1854/LU-8542993
https://doi.org/10.1242/jeb.164061
https://biblio.ugent.be/publication/8542993/file/8542994
Description
Summary:Mole-rats are known to use their protruding, chisel-like incisors to dig underground networks of tunnels, but it remains unknown how these incisors are used to break and displace the soil. Theoretically, different excavation strategies can be used. Mole-rats could either use their head depressor muscles to power scooping motions of the upper incisors (by nose-down head rotations) or the lower incisors (by nose-up head rotations), or their jaw adductors to grab and break the soil after penetrating both sets of incisors into the ground, or a combination of these mechanisms. To identify how chisel-tooth digging works, a kinematic analysis of this behaviour was performed based on high-speed videos of 19 individuals from the African molerat species Fukomys micklemi placed inside transparent tubes in a laboratory setting. Our analysis showed that the soil is penetrated by both the upper and lower incisors at a relatively high gape angle, generally with the head rotated nose-up. Initially, the upper incisors remain approximately stationary to function as an anchor to allow an upward movement of the lower incisors to grab the soil. Next, a quick, nose-down rotation of the head further detaches the soil and drops the soil below the head. Consequently, both jaw adduction and head depression are jointly used to power tooth-digging in F. micklemi. The same mechanism, but with longer digging cycles, and soil being thrown down at smaller gape sizes, was used when digging in harder soil.

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