Predictor Of Bite Force Research Articles

Theoretical calculations of bite force in billfishes

AbstractBite force is one of the most utilized performance measures due to its association with feeding and consequently fitness. Due to their large size and the concomitant increase in the adductor muscles it is expected that apex predators may rely on high biting performance allowing for increased dietary breadth. Billfish are apex marine predators characterized by the extreme elongation of the upper jaw bones forming a rostrum. This structure has been shown to facilitate prey capture and processing, but little is known as to whether this elongated structure has had an effect on biting performance in this group of enigmatic fishes. The goal of this study was to investigate bite force among five billfish species differing in size and rostrum morphology, and to determine the relationship between bite force and cranial anatomy. Because prey processing is partially decoupled from the oral jaws in these fishes, we hypothesized that bite force will be relatively low in billfishes compared to other fish, and that mass specific bite force will be inversely proportional to rostrum length. Anterior and posterior values of bite force ranged from 29 to 330 N and 99 to 1361 N, respectively among billfish species. Although absolute bite forces reached high values, mass specific bite force was among the lowest recorded for cartilaginous and bony fishes. Contrary to our hypothesis, rostrum length was not a predictor of bite force. The evolution of this novel structure, however, has been demonstrated to have a role in feeding, and the relatively low bite force in billfishes may indicate a lack of dependence on this performance metric for prey capture and processing.

The scaling of bite force and constriction pressure in kingsnakes (Lampropeltis getula): Proximate determinants and correlated performance

Across the diversity of vertebrates, bite force has been studied and suggested to have important ecological and evolutionary consequences. However, there is a notable lineage of vertebrates that use this performance trait yet are missing from the bite-force literature: the snakes. Snakes often rely on biting during prey subjugation and handling. Many snakes bite and hold prey while a constriction coil is formed or while venom is being delivered, or both. Others use biting exclusively without employing any additional prey-handling behaviors. In addition to biting, constriction is an important predation mechanism. Here, I quantify bite force and constriction pressure in kingsnakes (Lampropeltis getula). Furthermore, I explore the proximate determinants of bite force as well as the relationship between biting and constriction performance. Bite force increased linearly with all head and body measures. Of these, head height was the best predictor of bite force. Bite force in kingsnakes was within the range of values reported for lizards, but their relative performance was lower for their head size compared to lizards. Peak constriction pressure also increased with all body measures. Biting and constricting use 2 different parts of the musculoskeletal system and are positively and significantly correlated with one another. Future work targeting a greater diversity of snakes that rely more heavily on biting may reveal a greater range of bite performance in this diverse and successful vertebrate group.

Under pressure: morphological and ecological correlates of bite force in the rock-dwelling lizardsOuroborus cataphractusandKarusasaurus polyzonus(Squamata: Cordylidae)

Rock-dwelling lizards are hypothesized to be highly constrained in the evolution of head morphology and, consequently, bite force. Because the ability to generate a high bite force might be advantageous for a species' dietary ecology, morphological changes in head configuration that allow individuals to maintain or improve their bite force under the constraint of crevice-dwelling behaviour are to be expected. The present study addressed this issue by examining head morphology, bite force, and a number of dietary traits in the rock-dwelling cordylid lizards Ouroborus cataphractus and Karusasaurus polyzonus. The results obtained show that O. cataphractus has a larger head and higher bite force than K. polyzonus. In K. polyzonus, head width, lower jaw length, and jaw closing-in lever are the best predictors of bite force, whereas head height is the main determinant of bite force in O. cataphractus. Although the observed difference in bite force between the species does not appear to be related to dietary patterns or prey handling, the prey spectrum available for intake was greater in O. cataphractus compared to K. polyzonus. We discuss the influence of interspecific differences in anti-predator morphology on head morphology and bite force in these rock-dwelling species. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 823–833.

Scaling of bite performance with head and carapace morphometrics in green turtles (Chelonia mydas)

Adult green turtles (Chelonia mydas) are unusual relative to other sea turtles in that they are predominately herbivorous. This herbivorous diet is reflected in the serrated morphology of their beak, bite performance and the relative morphometrics of their heads. Recent bite performance data in loggerhead turtles (Caretta caretta), which are known for their durophagous capability, have demonstrated that bite force is correlated with head morphometrics. The objective of this study was to characterize bite force in green turtles and correlate bite performance with head and carapace morphometrics. We predicted that maximum bite force in green turtles would be less in magnitude relative to loggerheads, but would be positively correlated with head morphometrics. Therefore, mass, straight carapace length, straight carapace width, greatest head width, height, and length were collected with bite force from free-ranging green turtles from Punta Abreojos, Baja California Sur, Mexico and Otsuchi, Japan. Subjects ranged from 10.9 to 48kg, with straight carapace length and width ranged from 40.6cm to 71.9cm (mean=56.3±8.5cm) and from 33.5cm to 55.9cm (mean=44.8±5.7cm), respectively. A bite force apparatus was used to collect bite performance from subjects. The maximum bite force was 303N. Mean head width, head height, and head length were 8.7±1.2, 8.2±1.1, and 11.5±1.5cm, respectively. Bite force was lower in magnitude than reported for loggerhead turtles as predicted but still strong enough to process algal and plant matter, as well as crush many hard prey items. Simultaneous measurements of body and head size, and the use of non-linear reduced major axis regression, show that bite force scaled isometrically relative to body size and head size. Simple correlation showed that all logged transformed morphometrics were good predictors of logged bite performance, but an AICc-based weighted regression showed that body mass, followed by head width and head height, were better predictors of bite force than carapace size.

Proximate determinants of bite force capacity in the mouse lemur

AbstractBoth mating system and diet are thought to drive inter‐individual variation in bite force. Although previously published data suggest that bite force variation may be driven by variation in morphology (e.g. head morphology, body size, muscle size), age and physiology (e.g. fluctuating plasma testosterone levels) in some vertebrates, this remains untested in primates. Here, we explore the proximal determinants of bite force capacity in the grey mouse lemur Microcebus murinus. Our results show that in male grey mouse lemurs, bite force measurements are repeatable across a 1‐month period. Yet, bite forces were independent of fluctuation plasma testosterone levels. Head dimensions and body mass were all positively correlated with bite force. Among these, head width was the best predictor of bite force as has been observed for other vertebrates. Unexpectedly, age was highly significantly and positively correlated with bite force. Whereas older animals generally bit harder, the oldest age group (5.5 years) showed a decline in bite force capacity. These results suggest that bite force in the grey mouse lemur is mostly determined by morphology and age, yet is independent of variation in testosterone. Future studies including a broader age range and animals of different sexes would be of interest to better understand the variation in bite force in this small lemur.

The ontogenetic scaling of bite force and head size in loggerhead sea turtles (Caretta caretta): implications for durophagy in neritic, benthic habitats

Ontogenetic studies of vertebrate feeding performance can help address questions relevant to foraging ecology. Feeding morphology and performance can either limit access to food resources or open up new trophic niches in both aquatic and terrestrial systems. Loggerhead sea turtles are long-lived vertebrates with complex life histories that are marked by an ontogenetic shift from an oceanic habitat to a coastal neritic habitat, and a transition from soft oceanic prey to hard, benthic prey. Although considered durophagous and strong biters, bite performance has not been measured in loggerheads, nor has the ontogeny of bite performance been characterized. In the present study, we collected measurements of bite force in loggerhead turtles from hatchlings to adults. When subadults reach the body size at which the ontogenetic shift occurs, their crushing capability is great enough for them to consume numerous species of hard benthic prey of small sizes. As loggerheads mature and bite performance increases, larger and harder benthic prey become accessible. Loggerhead bite performance eventually surpasses the crushing capability of other durophagous carnivores, thereby potentially reducing competition for hard benthic prey. The increasing bite performance and accompanying changes in morphology of the head and jaws are likely an effective mechanism for resource partitioning and decreasing trophic competition. Simultaneous measurements of body and head size and the use of non-linear reduced major axis regression show that bite force increases with significant positive allometry relative to body size (straight carapace length, straight carapace width and mass) and head size (head width, height and length). Simple correlation showed that all recorded morphometrics were good predictors of measured bite performance, but an AICc-based weighted regression showed that body size (straight carapace width followed by straight carapace length and mass, respectively) were more likely predictors of bite force than head size morphometrics (head width and head length).

Sexual dimorphism, body size, bite force and male mating success in tuatara

287..292 Sexual dimorphisms in body size and head size are common among lizards and are often related to sexual selection on male fighting capacity (organismal performance) and territory defence. However, whether this is generally true or restricted to lizards remains untested. Here we provide data on body and head size, bite performance and indicators of mating success in the tuatara (Sphenodon punctatus), the closest living relative to squamates, to explore the generality of these patterns. First, we test whether male and female tuatara are dimorphic in head dimensions and bite force, independent of body size. Next, we explore which traits best predict bite force capacity in males and females. Finally, we test whether male bite force is correlated with male mating success in a free-ranging population of tuatara (Sphenodon punctatus). Our data confirm that tuatara are indeed dimorphic in head shape, with males having bigger heads and higher bite forces than females. Across all individuals, head length and the jaw closing in-lever are the best predictors of bite force. In addition, our data show that males that are mated have higher absolute but not relative bite forces. Bite force was also significantly correlated to condition in males but not females. Whereas these data suggest that bite force may be under sexual selection in tuatara, they also indicate that body size may be the key trait under selection in contrast to what is observed in squamates that defend territories or resources by biting. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 287‐292.

Is Extreme Bite Performance Associated with Extreme Morphologies in Sharks?

As top predators in many oceanic communities, sharks are known to eat large prey and are supposedly able to generate high bite forces. This notion has, however, largely gone untested due to the experimental intractability of these animals. For those species that have been investigated, it remains unclear whether their high bite forces are simply a consequence of their large body size or the result of diet-related adaptation. As aquatic poikilotherms, sharks can grow very large, making them ideal subjects with which to investigate the effects of body size on bite force. Relative bite-force capacity is often associated with changes in head shape because taller or wider heads can, for example, accommodate larger jaw muscles. Constraints on bite force in general may also be released by changes in tooth shape. For example, more pointed teeth may allow a predator to penetrate prey more effectively than blunt, pavementlike teeth. Our analyses show that large sharks do not bite hard for their body size, but they generally have larger heads. Head width is the best predictor of bite force across the species included in our study as indicated by a multiple regression model. Contrary to our predictions, sharks with relatively high bite forces for their body size also have relatively more pointed teeth at the front of the tooth row. Moreover, species including hard prey in their diet are characterized by high bite forces and narrow and pointed teeth at the jaw symphysis.