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Sabretoothed carnivores and the killing of large prey.

Andersson K, Norman D, Werdelin L - PLoS ONE (2011)

Bottom Line: For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed.The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations.We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom. andersson.ki@gmail.com

ABSTRACT
Sabre-like canines clearly have the potential to inflict grievous wounds leading to massive blood loss and rapid death. Hypotheses concerning sabretooth killing modes include attack to soft parts such as the belly or throat, where biting deep is essential to generate strikes reaching major blood vessels. Sabretoothed carnivorans are widely interpreted as hunters of larger and more powerful prey than that of their present-day nonsabretoothed relatives. However, the precise functional advantage of the sabretooth bite, particularly in relation to prey size, is unknown. Here, we present a new point-to-point bite model and show that, for sabretooths, depth of the killing bite decreases dramatically with increasing prey size. The extended gape of sabretooths only results in considerable increase in bite depth when biting into prey with a radius of less than ∼10 cm. For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed. The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations. Furthermore, our results demonstrate how sabretoothed carnivorans are likely to have evolved along a functionally continuous trajectory: beginning as an extension of a jaw-powered killing bite, as adopted by present-day pantherine cats, followed by neck-powered biting and thereafter shifting to neck-powered shear-biting. We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions. We also expect that our model for point-to-point biting and bite depth estimations will yield new insights into the behaviours of a broad range of extinct predators including therocephalians (gorgonopsian + cynodont, sabretoothed mammal-like reptiles), sauropterygians (marine reptiles) and theropod dinosaurs.

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Bite depth rapidly drops with increasing prey radius.Contour plot of bite depth (h, z-axis) for a 15 cm jaw as a function of prey radius (Rprey, x-axis) and canine clearance (c, y-axis) for two different jaw lengths. The arrow indicates how bite depth decreases as prey radius increases. The Rshift-threshold around which small changes in canine clearance (c) shift from returning large to small bite depth to smaller than the change itself is shown as a straight line.
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pone-0024971-g003: Bite depth rapidly drops with increasing prey radius.Contour plot of bite depth (h, z-axis) for a 15 cm jaw as a function of prey radius (Rprey, x-axis) and canine clearance (c, y-axis) for two different jaw lengths. The arrow indicates how bite depth decreases as prey radius increases. The Rshift-threshold around which small changes in canine clearance (c) shift from returning large to small bite depth to smaller than the change itself is shown as a straight line.

Mentions: We modelled bite depth for predators and prey at various sizes, assuming optimal canine clearance. The results are presented in Fig. 3. The full implication of predator-prey scaling in point-to-point biting is illustrated by the following comparison. Consider a predator with a 15 cm jaw (Rjaw15) and a 10 cm clearance (c10) between the canines at maximum gape, biting into prey with radii ranging between 1 and 100 cm (Rprey1…100). Maximum theoretical bite depth is limited by what can be fitted between the canines and ranges between 10 and 5.86 cm. This can be achieved for prey with radius smaller than 5 cm. For prey with radius 5 cm (Rprey5) bite depth is 5.86 cm and from there it drops dramatically to ∼2.2 cm for prey with a 10 cm radius (Rprey10) and 0.98 cm for prey at 100 cm radius (Rprey100). Now, consider the same jaw dimension but increase the gape and canines by 50%, from canine clearance 10 to 15 cm (c15). Maximum bite depth now ranges between 15 and 9.51 cm and is achieved for prey with less than 7.5 cm radius. At Rprey7.5 bite depth is 9.51 cm, At Rprey10 bite depth is 5.40 cm and at Rprey,100 bite depth is ∼2.3 cm.


Sabretoothed carnivores and the killing of large prey.

Andersson K, Norman D, Werdelin L - PLoS ONE (2011)

Bite depth rapidly drops with increasing prey radius.Contour plot of bite depth (h, z-axis) for a 15 cm jaw as a function of prey radius (Rprey, x-axis) and canine clearance (c, y-axis) for two different jaw lengths. The arrow indicates how bite depth decreases as prey radius increases. The Rshift-threshold around which small changes in canine clearance (c) shift from returning large to small bite depth to smaller than the change itself is shown as a straight line.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3198467&req=5

pone-0024971-g003: Bite depth rapidly drops with increasing prey radius.Contour plot of bite depth (h, z-axis) for a 15 cm jaw as a function of prey radius (Rprey, x-axis) and canine clearance (c, y-axis) for two different jaw lengths. The arrow indicates how bite depth decreases as prey radius increases. The Rshift-threshold around which small changes in canine clearance (c) shift from returning large to small bite depth to smaller than the change itself is shown as a straight line.
Mentions: We modelled bite depth for predators and prey at various sizes, assuming optimal canine clearance. The results are presented in Fig. 3. The full implication of predator-prey scaling in point-to-point biting is illustrated by the following comparison. Consider a predator with a 15 cm jaw (Rjaw15) and a 10 cm clearance (c10) between the canines at maximum gape, biting into prey with radii ranging between 1 and 100 cm (Rprey1…100). Maximum theoretical bite depth is limited by what can be fitted between the canines and ranges between 10 and 5.86 cm. This can be achieved for prey with radius smaller than 5 cm. For prey with radius 5 cm (Rprey5) bite depth is 5.86 cm and from there it drops dramatically to ∼2.2 cm for prey with a 10 cm radius (Rprey10) and 0.98 cm for prey at 100 cm radius (Rprey100). Now, consider the same jaw dimension but increase the gape and canines by 50%, from canine clearance 10 to 15 cm (c15). Maximum bite depth now ranges between 15 and 9.51 cm and is achieved for prey with less than 7.5 cm radius. At Rprey7.5 bite depth is 9.51 cm, At Rprey10 bite depth is 5.40 cm and at Rprey,100 bite depth is ∼2.3 cm.

Bottom Line: For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed.The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations.We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth Sciences, University of Cambridge, Cambridge, United Kingdom. andersson.ki@gmail.com

ABSTRACT
Sabre-like canines clearly have the potential to inflict grievous wounds leading to massive blood loss and rapid death. Hypotheses concerning sabretooth killing modes include attack to soft parts such as the belly or throat, where biting deep is essential to generate strikes reaching major blood vessels. Sabretoothed carnivorans are widely interpreted as hunters of larger and more powerful prey than that of their present-day nonsabretoothed relatives. However, the precise functional advantage of the sabretooth bite, particularly in relation to prey size, is unknown. Here, we present a new point-to-point bite model and show that, for sabretooths, depth of the killing bite decreases dramatically with increasing prey size. The extended gape of sabretooths only results in considerable increase in bite depth when biting into prey with a radius of less than ∼10 cm. For sabretooths, this size-reversed functional advantage suggests predation on species within a similar size range to those attacked by present-day carnivorans, rather than "megaherbivores" as previously believed. The development of the sabretooth condition appears to represent a shift in function and killing behaviour, rather than one in predator-prey relations. Furthermore, our results demonstrate how sabretoothed carnivorans are likely to have evolved along a functionally continuous trajectory: beginning as an extension of a jaw-powered killing bite, as adopted by present-day pantherine cats, followed by neck-powered biting and thereafter shifting to neck-powered shear-biting. We anticipate this new insight to be a starting point for detailed study of the evolution of pathways that encompass extreme specialisation, for example, understanding how neck-powered biting shifts into shear-biting and its significance for predator-prey interactions. We also expect that our model for point-to-point biting and bite depth estimations will yield new insights into the behaviours of a broad range of extinct predators including therocephalians (gorgonopsian + cynodont, sabretoothed mammal-like reptiles), sauropterygians (marine reptiles) and theropod dinosaurs.

Show MeSH
Related in: MedlinePlus