Data from: 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 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 mole-rat 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.

鼹形鼠（Mole-rats）以其突出的凿状门齿挖掘地下隧道网络而闻名，但目前仍不清楚这些门齿如何实现土壤的破碎与移位。理论上存在多种挖掘策略可供选择：鼹形鼠可通过头部下压肌群驱动上门齿进行铲掘动作（通过头部朝下旋转完成），或驱动下门齿进行铲掘动作（通过头部朝上旋转完成）；亦可在上下门齿刺入土壤后，借助下颌收肌群抓取并破碎土壤，或是结合上述多种机制共同运作。为明确凿齿挖掘的具体运作机制，本研究基于实验室透明管内饲养的19只米克氏非洲鼹形鼠（Fukomys micklemi）的高速录像，对该行为开展了运动学分析。分析结果表明，土壤会在较大张口角下被上下门齿同时刺入，此时头部通常呈朝上旋转状态。初始阶段，上门齿大致保持静止，充当锚点以允许下门齿向上运动抓取土壤。随后，头部快速朝下旋转，进一步剥离土壤并将其甩至头部下方。综上，米克氏非洲鼹形鼠的凿齿挖掘行为是通过下颌收肌收缩与头部下压动作协同发力实现的。当在更坚硬的土壤中挖掘时，会采用相同的机制，但挖掘周期更长，且在更小的张口角下将土壤向下抛出。