A simple morphological predictor of bite force in rodents

Bite force was quantified for 13 species of North American rodents using a piezo-resistive sensor. Most of the species measured (11) formed a tight relationship between body mass and bite force (log 10(bite force)=0.43(log 10(body mass))+0.416; R ²>0.98). This high correlation exists despite the ecological (omnivores, grazers and more carnivorous) and taxonomic (Cricetidae, Heteromyidae, Sciuridae and Zapodidae) diversity of species. Two additional species, Geomys bursarius (Geomyidae) and a Sciurus niger (Sciuridae), bit much harder for their size. We found a simple index of strength based on two measurements of the incisor at the level of the alveolus ( Z_i =((anterior-posterior length)²× (medial-lateral width))/6) that is highly predictive of bite force in these rodents (R²>0.96). Z_i may be useful for prediction of bite force (log10 (Bite Force)=0.566log10 ( Z_i )+1.432) when direct measurements are not available.     

The bite force of the largest fossil rodent (Hystricognathi,Caviomorpha, Dinomyidae)

Blanco R.E., Rinderknecht, A. & Lecuona, G. 2011: The bite force of the largest fossil rodent (Hystricognathi, Caviomorpha, Dinomyidae). Lethaia, Vol. 45, pp. 157–163. An exceptionally well‐preserved skull of the largest fossil rodent Josephoartigasia monesi allows the first analysis of the bite mechanics of this group of South American giant rodents. In this study, we reconstructed the main anatomical features of the skull of this Pliocene rodent, relating them to the bite force at incisors. Bite force was estimated using three different techniques. Two methods suggest that bite forces at incisors of around 1000 N were possible for these mammals. However, the incisors seem to be stronger than expected for this bite force implying that the bite forces may have been greater than 3000 N. We consider three hypotheses: allometric effects, teeth digging or defence against predators, to explain our results. □Bite force, Dinomyidae, incisors, largest rodent, Pliocene.     

Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics

Bite mechanics and feeding behaviour in Tyrannosaurus rex are controversial. Some contend that a modest bite mechanically limited T. rex to scavenging, while others argue that high bite forces facilitated a predatory mode of life. We use dynamic musculoskeletal models to simulate maximal biting in T. rex. Models predict that adult T. rex generated sustained bite forces of 35 000-57 000 N at a single posterior tooth, by far the highest bite forces estimated for any terrestrial animal. Scaling analyses suggest that adult T. rex had a strong bite for its body size, and that bite performance increased allometrically during ontogeny. Positive allometry in bite performance during growth may have facilitated an ontogenetic change in feeding behaviour in T. rex, associated with an expansion of prey range in adults to include the largest contemporaneous animals.     

Ontogenetic scaling of bite force in lizards and turtles

Because selection on juvenile life-history stages is likely strong, disproportionately high levels of performance (e.g., sprint speed, endurance, etc.) might be expected. Whereas this phenomenon has been demonstrated with respect to locomotor performance, data for feeding are scarce. Here, we investigate the relationships among body dimensions, head dimensions, and bite force during growth in lizards and turtles. We also investigate whether ontogenetic changes in bite performance are related to changes in diet. Our analyses show that, for turtles, head dimensions generally increase with negative allometry. For lizards, heads scale as expected for geometrically growing systems. Bite force generally increased isometrically with carapace length in turtles but showed significant positive allometry relative to body dimensions in lizards. However, both lizards and turtles display positive allometric scaling of bite force relative to some measures of head size throughout ontogeny, suggesting (1) strong selection for increased relative bite performance with increasing head size and (2) intrinsic changes in the geometry and/or mass of the jaw adductors during growth. Whereas our data generally do not provide strong evidence of compensation for lower absolute levels of performance, they do show strong links among morphology, bite force, and diet during growth.     

Head shape and bite performance in xenosaurid lizards

Bite performance in lizards influences many aspects of the animal's lifestyle. During feeding, inter- and intrasexual interactions, and defensive behavior, the ability to bite hard might be advantageous. Although biomechanical considerations predict clear relations between head shape and bite performance, this has rarely been tested. Here we investigate the effect of head shape on bite performance in three closely related species of xenosaurid lizards. Our data show that in this family of lizards, bite performance is mainly determined by head height, with high headed animals biting harder than flat headed ones. Species clearly differ in head shape and bite performance and show a marked sexual dimorphism. The dimorphism in head shape also results in an intersexual difference in bite performance. As head height is the major determinant of bite performance in xenosaurid lizards, trade offs between a crevice dwelling life-style and bite performance seem to occur. The evolutionary implications of these results are discussed. J. Exp. Zool. 290:101-107, 2001.     

儿童毒蛇咬伤的特点与程序化救治的疗效观察

目的通过分析儿童毒蛇咬伤的特点,评价程序化综合救治方法对儿童毒蛇咬伤的疗效。方法通过观察17例毒蛇咬伤儿童的临床特点,尽早进行病情预测,同时根据毒蛇咬伤的临床病情分型予程序化综合救治。监测病情变化、伤口愈合情况及平均住院时间。结果儿童毒蛇咬伤的特点为不明种类毒蛇咬伤多,症状较成人严重,易发生并发症。经过早期程序化综合救治总有效率100%,伤口渗血、肿胀明显缓解,无1例死亡,平均留观时间4.5天。结论根据儿童毒蛇咬伤特点,早期准确预测和尽快应用程序化救治能提高毒蛇咬伤疗效。     

Relationship between the training of young recruits and values of bite forces

Analysis of masticatory function is the basis of clinical work in almost all fields of dentistry. Bite forces are the expression and measure of masticatory function. Physical training has an effect on the development of functional ability, motoric ability of the organism and the formation of desired physical proportions. The purpose of this study was to examine the association between physical fitness and bite force values. Because of strictly defined regulations in the army with regard to training and nutrition, Croatian Army recruits were ideal examinees for this examination. The examinees were 135 recruits. Bite forces were measured on three places (area of the central incisors, left and right in the area of the first molars) before and after three-months of training. Of all the examinees, 108 had increased their body weight, 12 had decreased it and 15 had not changed their body weight. The median of measured forces in the recruits prior to training was 291 N in the right (lateral quadrant), 285.5 N in the left lateral quadrant and 205 N in the anterior area. After training the median of measured forces in the right quadrant was 312 N, in the left 313 N and in the anterior area 216 N Greater bite forces after training on all measured places were statistically proved. Increased activity of masticatory muscles can have the same effect on the values of bite forces as bite training. There are few data on the correlation between physical muscles and values of bite forces. The results of those studies are doubtful. In this study, after three months of conditional training, the body mass of the recruits had increased and they expressed greater values of bite forces. However, correlation between body mass and bite forces cannot be proved with certainty.     

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

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.     

Difficulties in assigning trace makers from theropodan bite marks: an example from a young diplodocoid sauropod

Bite marks on the bones of dinosaurs are relatively rare for non‐tyrannosaur dominated faunas, and few have been described in detail. Here, we describe a femur of a young diplodocoid sauropod in the Carnegie Quarry (Late Jurassic Morrison Formation) at Dinosaur National Monument that shows extensive bite marks to the proximal part of the bone. This is the only record of bite marks from this extensive quarry of over 1500 vertebrate elements, making this a most unusual find. Identification of the tracemaker is difficult as multiple large theropods are known from the quarry. Furthermore, we show that subtly different actions of feeding can potentially result in very different spacing of bite marks making matches to tooth patterns in the jaws of potential bite makers very uncertain. Although identification is uncertain, the tracemaker is clearly not a tyrannosaurid, but the selective scrape feeding pattern seen here is similar to the of tyrannosaurid theropods. This technique may be more widely distributed among large carnivorous theropods than previously realized.     

Effects of gape and tooth position on bite force and skull stress in the dingo (Canis lupus dingo) using a 3-dimensional finite element approach

Models of the mammalian jaw have predicted that bite force is intimately linked to jaw gape and to tooth position. Despite widespread use, few empirical studies have provided evidence to validate these models in non-human mammals and none have considered the influence of gape angle on the distribution of stress. Here using a multi-property finite element (FE) model of Canis lupus dingo, we examined the influence of gape angle and bite point on both bite force and cranial stress. Bite force data in relation to jaw gape and along the tooth row, are in broad agreement with previously reported results. However stress data showed that the skull of C. l. dingo is mechanically suited to withstand stresses at wide gapes; a result that agreed well with previously held views regarding carnivoran evolution. Stress data, combined with bite force information, suggested that there is an optimal bite angle of between 25 degrees and 35 degrees in C. l. dingo. The function of these rather small bite angles remains unclear.     

Sward height and bite size affect the functional response of barnacle geese Branta leucopsis

Intake rate, the rate in which herbivores can process their food, is presumed to be an important factor in habitat selection down to the scale of the foraging patch. Much attention has been given to the selection of swards of high nutritional quality, but much less has been given to the influences of sward structure on patch selection in small herbivores. In this study we tested the effects of sward density and height on the functional foraging response of barnacle geese, Branta leucopsis. The functional response curve for herbivores describes how intake rate is affected by food availability. We conducted feeding trials to determine intake rate and bite size of barnacle geese on experimentally manipulated swards. Results indicate that intake rate is mainly dependent on sward height and that there is a strong correlation between bite size and intake rate. Sward density does not influence the rate of food consumption; it is, however, a crucial parameter affecting potential total yield. We conclude that bite size is the crucial parameter influencing intake rate. Bite size is explained both by sward height and individual differences in bill morphology. Furthermore, intake rate seems to be dependent on the physical structure of the grass species consumed.     

The epidemiology of dog bite injuries in Switzerland – characteristics of victims,biting dogs and circumstances

Abstract

Dogs are a potential source of several health hazards for humans. Public attention has recently focussed on dog bites, and different prevention strategies have been suggested. As few data on dog bite epidemiology are available, a prospective study was conducted in family practices (FP) and emergency departments (ED) in Switzerland. The objectives of this study were to estimate the incidence of dog bites receiving medical treatment and to identify possible risk factors. An annual dog bite incidence rate of 180/100 000 population was estimated. The highest incidence rates were found in children, young adults and dog owners. While head and neck injuries were most common (37% of FP and 45% of ED cases) amongst children and these tended to have more severe sequelae, adults' injuries most commonly involved the extremities. Victim–dog interactions prior to the incident often were observed in children, particularly in infants (82% of 0–4-year-old cases) and in family dog bites (88%). Biting dogs were most commonly medium or large in size, male, and aged < 5 years. The three most popular breeds (Shepherd, Retriever Dogs and Swiss Mountain Breeds) also were the three most common biters. However, Shepherd dogs and Rottweilers were more common among biting dogs. No difference in bite risk was found between pure-bred and cross-bred dogs. Results of this study suggest that dog bites are a common event in the community. A multifactorial approach to dog bite prevention is recommended.     

Dry versus wet and gross: Comparisons between the dry skull method and gross dissection in estimations of jaw muscle cross-sectional area and bite forces in sea otters

Bite force is a measure of feeding performance used to elucidate links between animal morphology, ecology, and fitness. Obtaining live individuals for in vivo bite-force measurements or freshly deceased specimens for bite force modeling is challenging for many species. Thomason's dry skull method for mammals relies solely on osteological specimens and, therefore, presents an advantageous approach that enables researchers to estimate and compare bite forces across extant and even extinct species. However, how accurately the dry skull method estimates physiological cross-sectional area (PCSA) of the jaw adductor muscles and theoretical bite force has rarely been tested. Here, we use an ontogenetic series of southern sea otters (Enhydra lutris nereis) to test the hypothesis that skeletomuscular traits estimated from the dry skull method accurately predicts test traits derived from dissection-based biomechanical modeling. Although variables from these two methods exhibited strong positive relationships across ontogeny, we found that the dry skull method overestimates PCSA of the masseter and underestimates PCSA of the temporalis. Jaw adductor in-levers for both jaw muscles and overall bite force are overestimated. Surprisingly, we reveal that sexual dimorphism in craniomandibular shape affects temporalis PCSA estimations; the dry skull method predicted female temporalis PCSA well but underestimates male temporalis PCSA across ontogeny. These results highlight the importance of accounting for sexual dimorphism and other intraspecific variation when using the dry skull method. Together, we found the dry skull method provides an underestimation of bite force over ontogeny and that the underlying anatomical components driving bite force may be misrepresented.     

Annual incidence of snake bite in rural bangladesh

Background

Snake bite is a neglected public health problem in the world and one of the major causes of mortality and morbidity in many areas, particularly in the rural tropics. It also poses substantial economic burdens on the snake bite victims due to treatment related expenditure and loss of productivity. An accurate estimate of the risk of snake bite is largely unknown for most countries in the developing world, especially South-East Asia.

Methodology/Principal Findings

We undertook a national epidemiological survey to determine the annual incidence density of snake bite among the rural Bangladeshi population. Information on frequency of snake bite and individuals'' length of stay in selected households over the preceding twelve months was rigorously collected from the respondents through an interviewer administered questionnaire. Point estimates and confidence intervals of the incidence density of snake bite, weighted and adjusted for the multi-stage cluster sampling design, were obtained. Out of 18,857 study participants, over one year a total of 98 snake bites, including one death were reported in rural Bangladesh. The estimated incidence density of snake bite is 623.4 / 100,000 person years (95% C I 513.4–789.2 /100,000 person years). Biting occurs mostly when individuals are at work. The majority of the victims (71%) receive snake bites to their lower extremities. Eighty-six percent of the victims received some form of management within two hours of snake bite, although only three percent of the victims went directly to either a medical doctor or a hospital.

Conclusions/Significance

Incidence density of snake bite in rural Bangladesh is substantially higher than previously estimated. This is likely due to better ascertainment of the incidence through a population based survey. Poor access to health services increases snake bite related morbidity and mortality; therefore, effective public health actions are warranted.     

Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation

Background

Crocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known.

Methodology/Principal Findings

We measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research.

Conclusions/Significance

Critical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination.     

BluePort: a platform to study the eosinophilic response of mice to the bite of a vector of Leishmania parasites, Lutzomyia longipalpis sand flies

Background

Visceral Leishmaniasis is a serious human disease transmitted, in the New World, by Lutzomyia longipalpis sand flies. Natural resistance to Leishmania transmission in residents of endemic areas has been attributed to the acquisition of immunity to sand fly salivary proteins. One theoretical way to accelerate the acquisition of this immunity is to increase the density of antigen-presenting cells at the sand fly bite site. Here we describe a novel tissue platform that can be used for this purpose.

Methodology/Principal Findings

BluePort is a well-vascularized and macrophage-rich compartment induced in the subcutaneous tissue of mice via injection of agarose beads covered with Cibacron blue. We describe the sequence of inflammatory events leading to its formation and how it can be used to study the dermal response to the bite of L. longipalpis sand flies. Results presented indicate that a shift in the inflammatory response, from neutrophilic to eosinophilic, is the main histopathological feature associated with the immunity acquired through repeated exposure to the bite of sand flies, and that the BluePort tissue compartment could be used to accelerate this process. In addition, changes observed inside the BluePort parenchyma indicate that it could be used to study complex immunobiological processes, and to develop ectopic secondary lymphoid structures.

Conclusions/Significance

Understanding the characteristics of the dermal response to the bite of sand flies is a critical element of strategies to control leishmaniasis using vaccines that target salivary proteins. Finding that dermal eosinophilia is such a prominent component of the anti-salivary immunity induced by repeated exposure to sand fly bites raises one important consideration: how to avoid the immunological conflict derived from a protective Th2-driven immunity directed to sand fly saliva with a protective Th1-driven immunity directed to the parasite. The BluePort platform is an ideal tool to address experimentally this conundrum.     

Comparing apples and oranges—the influence of food mechanical properties on ingestive bite sizes in lemurs

Previously we found that Maximum Ingested Bite Size (V_b)—the largest piece of food that an animal will ingest whole without biting first—scales isometrically with body size in 17 species of strepsirrhines at the Duke Lemur Center (DLC). However, because this earlier study focused on only three food types (two with similar mechanical properties), it did not yield results that were easily applied to describing the broad diets of these taxa. Expressing V_b in terms of food mechanical properties allows us to compare data across food types, including foods of wild lemurs, to better understand dietary adaptations in lemurs. To this end, we quantified V_b in five species of lemurs at the DLC representing large and small frugivores and folivores using ten types of food that vary widely in stiffness and toughness to determine how these properties relate to bite sizes. We found that although most species take smaller bites of stiffer foods, this negative relationship was not statistically significant across the whole sample. However, there is a significant relationship between bite size and toughness. All three of the more frugivorous taxa in our sample take significantly smaller bites of tougher foods. However, the two more folivorous lemurs do not. They take small bites for all foods. This suggests that the species most adapted to the consumption of tough foods do not modulate their ingestive sizes to accommodate larger pieces of weak foods. Am J Phys Anthropol 157:513–518, 2015. © 2015 Wiley Periodicals, Inc.     

Mechanism of the switchover from extensive to area-concentrated search behaviour of the ladybird beetle, Coccinella septempunctata bruckii

Area-concentrated search of predatory coccinellid adults, Coccinella septempunctata bruckii, is considered to be controlled by internal locomotory information, since the area-concentrated search is generated even if aphids are no longer present in the environment. To investigate what kind of cue elicits the switchover from extensive to area-concentrated search behaviour, the duration of area-concentrated search (giving-up time) was measured after each of the following five kinds of feeding stimuli was supplied: (a) contact with an aphid (Myzus persicae), (b) biting an aphid, (c) consumption of an aphid, (d) contact with an agar block of ca 2 × 2 × 2 mm, (e) consumption of an agar-block coated with a droplet of aphid body fluid. Switchover from extensive to area-concentrated search was observed as a response to all feeding stimuli. The cue to elicit the switchover is the contact with a prey rather than the consumption of it. The giving-up time is dependent on the intensity of feeding stimulus since giving-up time varied according to the type of feeding stimulus (d = a < b < e < c). The giving-up time was positively correlated with the duration of feeding on an aphid which represented the size of prey consumed. To test whether giving-up time is determined by the amount or by the size of prey consumed, it was measured after the ladybird beetle had fed first on a large then on a small aphid (Sequence A) and after it had fed first on a small then on a large aphid (Sequence B). Although the beetle consumed the same total amount of aphids in both sequences, the beetle showed the longer giving-up time in Sequence B than in Sequence A. Therefore, it can be concluded that giving-up time is determined by the size of prey most recently consumed rather than hunger level or prey capture rate.