Masticatory muscle anatomy and feeding efficiency of the American beaver, Castor canadensis (Rodentia, Castoridae)

TY - JOUR

T1 - Masticatory muscle anatomy and feeding efficiency of the American beaver, Castor canadensis (Rodentia, Castoridae)

AU - Cox, Philip Graham

AU - Baverstock, Hester

N1 - (c) Springer Science+Business Media New York 2015. This is an author produced version of a paper published in Journal of Mammalian Evolution. Uploaded in accordance with the publisher's self-archiving policy.

PY - 2016/6/1

Y1 - 2016/6/1

N2 - Beavers are well-known for their ability to fell large trees through gnawing. Yet, despite this impressive behavior, little information exists on their masticatory musculature or the biomechanics of their jaw movements. It was hypothesized that beavers would have a highly efficient arrangement of the masticatory apparatus, and that gnawing efficiency would be maintained at large gape. The head of an American beaver, Castor canadensis, was dissected to reveal the masticatory musculature. Muscle origins and insertions were noted, the muscles were weighed and fiber lengths measured. Physiological cross-sectional areas were determined, and along with the muscle vectors, were used to calculate the length of the muscle moment arms, the maximum incisor bite force, and the proportion of the bite force projected along the long axis of the lower incisor, at occlusion and 30° gape. Compared to other sciuromorph rodents, the American beaver was found to have large superficial masseter and temporalis muscles, but a relatively smaller anterior deep masseter. The incisor bite force calculated for the beaver (550–740 N) was much higher than would be predicted from body mass or incisor dimensions. This is not a result of the mechanical advantage of the muscles, which is lower than most other sciuromorphs, but is likely related to the very high percentage (>96 %) of bite force directed along the lower incisor long axis. The morphology of the skull, mandible and jaw-closing muscles enable the beaver to produce a very effective and efficient bite, which has permitted beavers to become highly successful ecosystem engineers.

AB - Beavers are well-known for their ability to fell large trees through gnawing. Yet, despite this impressive behavior, little information exists on their masticatory musculature or the biomechanics of their jaw movements. It was hypothesized that beavers would have a highly efficient arrangement of the masticatory apparatus, and that gnawing efficiency would be maintained at large gape. The head of an American beaver, Castor canadensis, was dissected to reveal the masticatory musculature. Muscle origins and insertions were noted, the muscles were weighed and fiber lengths measured. Physiological cross-sectional areas were determined, and along with the muscle vectors, were used to calculate the length of the muscle moment arms, the maximum incisor bite force, and the proportion of the bite force projected along the long axis of the lower incisor, at occlusion and 30° gape. Compared to other sciuromorph rodents, the American beaver was found to have large superficial masseter and temporalis muscles, but a relatively smaller anterior deep masseter. The incisor bite force calculated for the beaver (550–740 N) was much higher than would be predicted from body mass or incisor dimensions. This is not a result of the mechanical advantage of the muscles, which is lower than most other sciuromorphs, but is likely related to the very high percentage (>96 %) of bite force directed along the lower incisor long axis. The morphology of the skull, mandible and jaw-closing muscles enable the beaver to produce a very effective and efficient bite, which has permitted beavers to become highly successful ecosystem engineers.

KW - Beaver

KW - Bite force

KW - Dissection

KW - Masticatory muscles

KW - Rodent

UR - http://www.scopus.com/inward/record.url?scp=84939208219&partnerID=8YFLogxK

U2 - 10.1007/s10914-015-9306-9

DO - 10.1007/s10914-015-9306-9

M3 - Article

SN - 1064-7554

VL - 23

SP - 191

EP - 200

JO - Journal of mammalian evolution

JF - Journal of mammalian evolution

IS - 2

ER -