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First published online August 17, 2007
Journal of Experimental Biology 210, 3096-3106 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.003210
Kinematic analysis of an appetitive food-handling behavior: the functional morphology of Syrian hamster cheek pouches
Lehigh University, Bethlehem, PA 18015, USA
* Author for correspondence at present address: Psychology Department, Lafayette College, Easton, PA 18042, USA (e-mail: buckleyc{at}lafayette.edu)
Accepted 20 June 2007
Prodigious food hoarding in Syrian hamsters Mesocricetus auratus
Waterhouse is strongly linked to appetite and is made possible by large
internal cheek pouches. We provide a functional analysis of the cheek pouch
and its associated retractor muscle. Frame-by-frame analysis of videotaped
pouch-filling behavior revealed multiple jaw cycles for each food item pouched
and the use of more jaw cycles to pouch large food items (
2.5 g chow
pellets) than small (corn kernels or sunflower seed with husks). These results
stand in contrast to previously reported pouching kinematics in the externally
pouched Dipodomys deserti, which uses only one jaw cycle per pouching
event. Comparison of pouching and mastication in the same individuals also
suggests that in Syrian hamsters, feeding jaw cycles are modulated to
accommodate pouch filling primarily by the addition of a pause between fast
open and fast close phases, which we call `gape phase'. Contrary to previous
assertions, the retractor muscle does not merely provide structural support
for the full pouch during locomotion. Video analysis of ten hamsters with
unilaterally denervated retractor muscles and electrophysiological study of an
anaesthetized subject confirmed that retractor muscle activity during pouch
filling increases pouching efficiency for food items subsequent to the
first.
Key words: Mesocricetus, feeding, hoard, retractor
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