A simple morphological predictor of bite force in rodents

Freeman, Patricia W.; Lemen, Cliff A.

doi:10.1111/j.1469-7998.2008.00459.x

Cited by 51 publications

(70 citation statements)

References 14 publications

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“…It also suggests that the presence of the Y and/or X* chromosomes does not significantly influence shape. However, without considering the groups, we found a positive relationship between size and bite force, as shown in previous studies (Herrel et al, 2001;Lailvaux et al, 2004;Freeman and Lemen, 2008). Furthermore, X*Y females displayed a greater skull size, which appears to explain part of their increased bite force (Tables 1, 2).…”

Section: Resultssupporting

confidence: 46%

Sex reversal induces size and performance differences among females of the African pygmy mouse, Mus minutoides

Ginot

Julien

Pérez

et al. 2017

Journal of Experimental Biology

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Differences in biological performance, at both intra- and inter-specific levels, have often been linked to morphology but seldom to behavioural or genotypic effects. We tested performance at the intraspecific level by measuring bite force in the African pygmy mouse, Mus minutoides. This species displays an unusual sex determination system, with sex-reversed, X*Y females carrying a feminizing X* chromosome. X*Y females cannot be differentiated from XX females based on external or gonadal morphology; however, they are known to be more aggressive. We found that bite force was higher in X*Y females than in other females and males. We then performed geometric morphometric analyses on their skulls and mandibles and found that the higher performance of X*Y females was mainly explained by a greater overall skull size. The effects of the X* chromosome thus go beyond feminization, and extend to whole-organism performance and morphology. Our results also suggest limited effects of behaviour on bite force.

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Section: Resultssupporting

confidence: 46%

Sex reversal induces size and performance differences among females of the African pygmy mouse, Mus minutoides

Ginot

Julien

Pérez

et al. 2017

Journal of Experimental Biology

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“…Bite force magnitudes recorded in the present study differ markedly from a recent field study of bite force in these same species. Freeman and Lemen (2008b) report bite average forces of 8.83 and 11.45 N from four wildcaught individuals of P. maniculatus and two wildcaught individuals of O. leucogaster, respectively. These values are the average of the largest bite recorded from each individual in the field.…”

Section: Discussion Maximum Gape In O Leucogaster and P Maniculatusmentioning

confidence: 97%

“…Most obviously, as acknowledged by Freeman and Lemen (2008b), their bite force values were based on small sample sizes, particularly for O. leucogaster, both in terms of number of bites recorded and numbers of individuals sampled. It could also be that the procedure utilized by Freeman and Lemen (2008a,b) of sampling bites over a period of approximately 1 min is not sufficient for obtaining the most aggressive biting behaviors in these animals.…”

Section: Discussion Maximum Gape In O Leucogaster and P Maniculatusmentioning

confidence: 99%

Gape and bite force in the rodents Onychomys leucogaster and Peromyscus maniculatus: Does jaw‐muscle anatomy predict performance?

Williams

Peiffer

Ford

2009

Journal of Morphology

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Compared with the deer mouse, Peromyscus maniculatus, the grasshopper mouse, Onychomys leucogaster, exhibits modifications in its jaw-muscle architecture that promote wide gapes and large bite forces at wide gapes to prey upon large vertebrate prey. In this study, we determine whether jaw-muscle anatomy predicts gape and biting performance in O. leucogaster, and we also assess the influence of gape on bite force in the two species. Although O. leucogaster has an absolutely longer jaw, which facilitates larger gapes, maximum passive gape is similar in both species, averaging approximately 12.5 mm. Thus, when scaled to jaw length, O. leucogaster has a smaller maximum passive gape. These results suggest that predatory behaviors of O. leucogaster may not require remarkably large gapes. On the other hand, both absolute and relative bite forces exerted by O. leucogaster are significantly larger than those of P. maniculatus. The largest bite forces in both species occur at 5.0 mm of gape at the incisors, or 40% of maximum gape. Although bite force in both species decreases at larger gapes, O. leucogaster does maintain a larger percentage of maximum bite force at gapes larger than 40% of maximum passive gape. Therefore, although structural modifications in the masticatory apparatus of O. leucogaster may constrain gape, they may help to maintain bite force at large gapes. These results suggest that increases in gape differentially influence the length-tension properties of the jaw muscles in the two species. Finally, these results highlight the importance of considering the effect of muscle stretch on force production in comparative studies of bite force. As a first approximation, it appears that gapes of 40-50% of maximum gape in rodents optimizes bite force production at the incisors.

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“…We tentatively suggest that this may be due to interspecific competition with larger squirrels. Bite force is positively correlated with body size [21], [56], so larger squirrels can exert greater forces to open hard-shelled fruits and nuts than smaller ones. Competition with larger squirrels and other larger herbivorous mammals would have forced dwarf squirrels to specialize on a dietary activity such as bark gleaning.…”

Section: Discussionmentioning

confidence: 99%

Conservatism and Adaptability during Squirrel Radiation: What Is Mandible Shape Telling Us?

Casanovas‐Vilar

Dam

2013

PLoS ONE

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Both functional adaptation and phylogeny shape the morphology of taxa within clades. Herein we explore these two factors in an integrated way by analyzing shape and size variation in the mandible of extant squirrels using landmark-based geometric morphometrics in combination with a comparative phylogenetic analysis. Dietary specialization and locomotion were found to be reliable predictors of mandible shape, with the prediction by locomotion probably reflecting the underlying diet. In addition a weak but significant allometric effect could be demonstrated. Our results found a strong phylogenetic signal in the family as a whole as well as in the main clades, which is in agreement with the general notion of squirrels being a conservative group. This fact does not preclude functional explanations for mandible shape, but rather indicates that ancient adaptations kept a prominent role, with most genera having diverged little from their ancestral clade morphologies. Nevertheless, certain groups have evolved conspicuous adaptations that allow them to specialize on unique dietary resources. Such adaptations mostly occurred in the Callosciurinae and probably reflect their radiation into the numerous ecological niches of the tropical and subtropical forests of Southeastern Asia. Our dietary reconstruction for the oldest known fossil squirrels (Eocene, 36 million years ago) show a specialization on nuts and seeds, implying that the development from protrogomorphous to sciuromorphous skulls was not necessarily related to a change in diet.

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A simple morphological predictor of bite force in rodents

Cited by 51 publications

References 14 publications

Sex reversal induces size and performance differences among females of the African pygmy mouse, Mus minutoides

Sex reversal induces size and performance differences among females of the African pygmy mouse, Mus minutoides

Gape and bite force in the rodents Onychomys leucogaster and Peromyscus maniculatus: Does jaw‐muscle anatomy predict performance?

Conservatism and Adaptability during Squirrel Radiation: What Is Mandible Shape Telling Us?

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