foot/feet up and down rhythmically Lie supine, flex and extend leg rhythmically, thus bounce foot up and down. Element of balance. See video. bow Plooij Bow: Similar to bob in context. Deep flexion of legs but arms extended forward, so that head is lower than hips. Absent in bonobos, but see Pika. Category 3. See video. brachiate Goodall Brachiation. Hanging from branch, swings hand-over-hand to move to terminal branch of tree to eat or to descend to ground. Plooijs Brachiate. Same as Kanos Brachiation and Susman et al.s Armswinging. Cf. swing. See video. branch break See break branch. branch-clasp See groom-branch-clasp. branch din See din branch. branch drag See drag branch. branch-flail See flail long object. branch-haul See hook branch. branch-hook See hook branch. branch shake See shake