Field age determination of leopards by tooth wear

Age determination is an important tool in wildlife studies. Estimating the age of animals in the field using tooth wear criteria may be subject to error as a result of variations between individuals, habitats and populations. Data on age estimation of leopards and tooth wear characteristics are lacking. Nineteen leopards in Namibia were assessed for tooth eruption and wear. Between 1991 and 1995 leopards (including 13 individuals of known age) were monitored at one year intervals ('28 leopard years') to record age and tooth wear. At the age of two years leopards had fully developed dentition. Wear started with the incisors and canines, and spread to the premolars and molars. A chronology of tooth eruption and wear in relation to age is presented. Above the age of three years, male leopards showed higher frequencies of enamel flaking and canine fractures than females.     

Measurements of tooth wear among Australian Aborigines: I. Serial loss of the enamel crown

The dental casts made from Aboriginal children during the course of a longitudinal growth study in Central Australia provided material for analyzing tooth wear under known environmental conditions. The wear facets produced on the occlusal surfaces were clearly preserved on the dental stone casts and recorded the progress of enamel attrition from ages 6 to 18. These casts were photographed and traced by electronic planimetric methods that automatically recorded the location and size of wear facets on the first and second permanent molars. These areas of worn tooth surface were compared to the total tooth surface. The worn surface was regressed on age to calculate wear rates of each tooth. Discriminant analyses were also performed to determine the significance of dental attrition differences between the sexes at each age group. The total wear on each tooth was highly correlated with age as expected but females wore their teeth at a significantly higher rate than males. The mandibular molars wore more rapidly than maxillary teeth in both sexes. The discriminant analysis successfully grouped 91% of the cases according to age and sex. Pattern of wear, the location, and size of wear facets also differed between age groups and sex. The questions of why there is a difference between male and female wear or why there is greater wear on one arch or arch region have no ready answers. The differing rates and pattern of dental wear do suggest that arch shape and growth rates may be the answer though it has yet to be tested. However, the occlusal surface wear is useful for age estimation in a population and provides a record of shifting masticatory forces during growth.     

Relationship of Tooth Wear to Chronological Age among Indigenous Amazon Populations

In indigenous populations, age can be estimated based on family structure and physical examination. However, the accuracy of such methods is questionable. The aim of this cross-sectional study was to evaluate occlusal tooth wear related to estimated age in the remote indigenous populations of the Xingu River, Amazon. Two hundred and twenty three semi-isolated indigenous subjects with permanent dentition from the Arara (n = 117), Xicrin-Kayapó (n = 60) and Assurini (n = 46) villages were examined. The control group consisted of 40 non-indigenous individuals living in an urban area in the Amazon basin (Belem). A modified tooth wear index was applied and then associated with chronological age by linear regression analysis. A strong association was found between tooth wear and chronological age in the indigenous populations (p <0.001). Tooth wear measurements were able to explain 86% of the variation in the ages of the Arara sample, 70% of the Xicrin-Kaiapó sample and 65% of the Assurini sample. In the urban control sample, only 12% of ages could be determined by tooth wear. These findings suggest that tooth wear is a poor estimator of chronological age in the urban population; however, it has a strong association with age for the more remote indigenous populations. Consequently, these findings suggest that a simple tooth wear evaluation method, as described and applied in this study, can be used to provide a straightforward and efficient means to assist in age determination of newly contacted indigenous groups.     

The dentition of red deer (Cervus elaphus): a scoring scheme to assess age from wear of the permanent molariform teeth

Skulls of red deer ( Cervus elaphus of known age were examined. A scoring procedure devised for fallow deer ( Dama dama ) was used to relate tooth wear to a particular age (Brown & Chapman, 1990). The precise sequential nature of tooth wear as it appeared on the slopes and tips of cusps, on the marginal ridges and links between cusps was recorded. From these data a base has been provided from which estimates of age may be made of animals of unknown age. The variability for the scores are given for 95% prediction intervals from the regression of age on total molar wear score.     

Connecting morphology, function and tooth wear in microchiropterans

A key objective in understanding the dentition of mammals is the ability to predict the function of teeth from their shape. Very few studies have used dental measurements that allow the prediction of comparative tooth effectiveness, particularly when modification in shape due to tooth wear is considered. Here, dental parameters are used in which a change in the parameter is readily interpretable in terms of change in factors such as increased force or energy required for cusps or crests to break down food. The functional parameters were measured for 3-D digital tooth reconstructions of the upper molars of the microchiropteran Chalinolobus gouldii at various stages of tooth wear. The changes in the majority of the parameters, such as decreased tip, edge and cusp sharpnesses, cusp occlusion relief, rake angle and fragment clearance, predict a deterioration in efficacy with increased wear. This conclusion has not been possible with alternative approaches; for instance, there was no significant change in crest length with wear, and so no change in function would be predicted from that measure. Some of the parameters did not change significantly with heavy wear, such as capture area of a crest, pointing to geometrical and design characteristics for the maintenance of shape with wear in the dilambdodont tooth form. Attrition and abrasion can be considered as wear on the relief and rake surfaces of tribosphenic-like crests, respectively. The differences in function of these two surfaces account for the differences in wear patterns.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 81–96.     

Tooth wear and the position of the mental foramen

Variation in the position of the mental foramen with respect to the teeth ("apparent" position) seems to be associated with race, but in the determination of this position, factors which affect the disposition of the teeth plainly have a bearing on the results. The apparent position was investigated in a sample of southern Chinese skulls of known age which were classified by the degree of tooth wear. Controlling for "true" position and size of the mandible, a highly significant correlation between wear and position was found, age and tooth size having no significant contribution as additional explanatory variables. The effect of tooth wear on the apparent position of the foramen may partly explain racial variation.     

Age and individual foraging behavior predict tooth wear in Amboseli baboons

Teeth represent an essential component of the foraging apparatus for any mammal, and tooth wear can have significant implications for survival and reproduction. This study focuses on tooth wear in wild baboons in Amboseli, southern Kenya. We obtained mandibular and maxillary tooth impressions from 95 baboons and analyzed digital images of replicas made from these impressions. We measured tooth wear as the percent dentine exposure (PDE, the percent of the occlusal surface on which dentine was exposed), and we examined the relationship of PDE to age, behavior, and life history variables. We found that PDE increased significantly with age for both sexes in all three molar types. In females, we also tested the hypotheses that long‐term patterns of feeding behavior, social dominance rank, and one measure of maternal investment (the cumulative number of months that a female had dependent infants during her lifetime) would predict tooth wear when we controlled for age. The hypothesis that feeding behavior predicted tooth wear was supported. The percent of feeding time spent consuming grass corms predicted PDE when controlling for age. However, PDE was not associated with social dominance rank or maternal investment. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Decelerating and sex-dependent tooth wear in Norwegian red deer

In ungulates, tooth wear is often suggested as a proximate cause of senescence. Tooth wear is expected to be sex-dependent since energetic requirements and food selection varies largely between sexes in sexually dimorphic ungulates. Furthermore, tooth wear may lower mastication efficiency, and we predict a negative correlation between tooth wear and body weight or condition. We tested these predictions on data on tooth wear (estimated as height of first molar) of 1,311 male and 1,348 female red deer ( Cervus elaphus) aged 3-25 years and harvested along the west coast of Norway. The rate of tooth wear decreased with age. Males wear teeth at a higher rate (from 0.61 mm/year in 4-year olds to 0.45 mm/year in 11-year olds) than females (from 0.52 mm/year in 4-year olds to 0.39 mm/year in 11-year olds). Molar height correlated positively with body weight in both sexes, but not after adjusting for body size. Molar height was strongly dependent on body size in 3-year-old individuals (when tooth wear is minimal). Earlier reports in the literature of a positive correlation between tooth height and body weight may therefore be due to initial size differences rather than differences in condition due to tooth wear.     

Evidence for a trade-off between early growth and tooth wear in Svalbard reindeer

Ruminants depend on efficient physical degradation of forage through chewing to increase the surface area of the food particles presented to the microflora. Fossil evidence suggests that increased molar height is an adaptation for wear tolerance in dry ecosystems with sparse vegetation, but no study has shown selection pressure for hypsodonty in contemporary ruminants. We explored the relationships between particle size in rumen, tooth wear (scanned molar occlusal topography), age and body mass of female Svalbard reindeer living in an arctic desert at 78 degrees latitude on Svalbard. We predicted that (H1) if the rumen particle size is determined mainly by constraints due to tooth wear, and if tooth wear is mainly a function of age, average particle size in rumen should increase with age. From allometric relations it is known that larger individuals can survive on a lower-quality diet, we therefore predicted (H2) larger particle sizes with increases in (ln) body mass, irrespective of age and wear. Lastly, if there is a trade-off between growth and tooth wear in dry ecosystems (a selection pressure for hypsodonty), we predicted (H3) that teeth of heavier animals should be more worn than those of lighter animals of the same age. The proportion of small particles (<1.0 mm) decreased rapidly with increasing age (consistent with H1). Heavier females within an age class had more worn teeth (consistent with H3) than lighter ones. A close-to-isometric relationship between particle size and body mass suggested that heavier animals partly compensated for reduced tooth efficiency by chewing more. We provide the first evidence of a trade-off between fast early growth and wear (a somatic cost) of a senescence-related trait--the structure and height of the molar--in a wild ruminant inhabiting an arctic desert where selection pressure for increased tooth height is expected. This suggests that foraging conditions are more extreme than the environment in which the species originally evolved.     

儿童牙齿磨耗研究概述

牙齿磨耗是一个多因素、多阶段、复杂渐进的过程。其特征是牙齿硬组织逐渐消失,牙齿磨耗程度可以一定程度反映饮食结构和生活方式。国外很多学者探讨了年龄、性别、饮食结构、断奶、社会分工、社会经济地位等因素对儿童牙齿磨耗的影响,及乳齿恒齿磨耗差异、牙列磨耗模式特点、牙齿磨耗与错𬌗畸形的关系等,而国内儿童牙齿磨耗研究相对薄弱。本文通过梳理和归纳相关文献,对儿童牙齿磨耗研究作简要概述,并对国内相关研究作简要回顾及展望。     

桂林甑皮岩新石器时代遗址2例儿童的年龄问题

作者报告２例于桂林甑皮岩新石器时代早期遗址出土的正处于换牙期的儿童乳、恒牙更换及其被磨耗的状况,讨论了从他们的牙磨耗级估计的年龄与从其乳、恒牙更换关系估计的年龄的误差,并提出用现代人牙磨耗级估计史前人类年龄的意见．     

Sex-specific strategies of dentine depletion in red deer

Worn teeth in herbivore ungulates may be related to lower efficiency in mastication and hence lower performance. However, selection should favour maximal performance in terms of body mass and reproductive capacity during reproductive lifespan, when permanent teeth are already partially worn. We hypothesize that wear rate may respond to a strategy of use of tooth materials (notably dentine), which balances instantaneous wear rate and performance against tooth preservation for future performance and reproduction. In the present study, we investigated 4151 carcasses of Iberian red deer Cervus elaphus hispanicus and show that more worn molars were not related to lower performance throughout age. By comparing between sexes, tooth wear rates were smaller in females than in males, but the relationship between tooth wear and body performance also differed between the sexes: females did not show a significant relationship between tooth wear and performance but males with more worn teeth were in general heavier and had larger antlers until senile age, when more depleted teeth were related to smaller antlers. These results reveal, for the first time, sex-specific lifetime strategies of dentine expenditure: maintenance of performance ability throughout a longer reproductive lifespan in females, compared with maximizing current performance by depleting dentine reserves within a shorter lifespan in males.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 93 , 487–497.     

Age determination of the African buffalo, Syncerus caffer Sparrman

Age criteria for the African buffalo are described. These are based on the tooth eruption sequence and on wear of the first molar. Assignment of absolute ages to the tooth eruption and wear classes has been made by reference to known-age animals and to numbers of cementum lines in tooth sections. For ageing animals to the nearest year, the normal degree of accuracy of the methods is assumed to be about ± 1/2year (1–5 years of age); about ± 1 year (5–15 years of age); and about ±2 years (15-20years of age). A field method of age determination is presented based on horn characteristics and relative body size.     

Bigger teeth for longer life? Longevity and molar height in two roe deer populations

The role of tooth wear as a proximate cause of senescence in ruminants has recently been highlighted. There are two competing hypotheses to explain variation in tooth height and wear; the diet-quality hypothesis predicting increased wear in low-quality habitats, and the life-history hypothesis predicting molar height to be related to expected longevity. We compared tooth height and wear from roe deer of known age from two contrasting populations of roe deer (Capreolus capreolus) in France: Trois Fontaines (TF) with good habitat and shorter animal life expectancy and Chizé (CH) with poor habitat and longer animal life expectancy. There was no population difference in tooth wear, leading to rejection of the diet-quality hypothesis. However, despite their smaller body size, initial molar height for animals from CH was larger than for animals from TF. This provides the first evidence that variation in longevity between populations can lead to differences in molar height within a species.     

Age estimation of the White rhinoceros (Ceratotherium simum)

Age estimation criteria for the southern White rhinoceros ( Ceratotherium simum simum ) are presented both for free-ranging live animals and for cranial material. These are based on: (i) size appearance and horn development of live animals; (ii) stages of tooth eruption; (iii) tooth wear classes; (iv) attrition in height of the first molar tooth; (v) counts of cementum lines visible in tooth sections. Selected measurements are presented for live animals, skulls and horns.
For live animals, eight size classes are distinguished, seven of these covering immature animals up to ten years of age. Sixteen tooth wear classes are established, based on eruption and surface wear of maxillary dentition. Chronological ages were assigned from individually known animals followed in the field, and from skulls from animals for which exact records of age were available, or which could be assigned to an age category from appearance at death. Cementum line counts corresponded approximately with age in years, despite difficulties in interpreting lines. Some variability was observed, possibly related to nutritional conditions.
The maximum cementum line count obtained indicates a longevity of at least 40 years. Full body weight and socio-sexual maturity are attained by males between 10 and 15 years of age, while females first give birth between six and eight years of age. Sequences and times of tooth eruption are similar to those reported for the Black rhinoceros ( Diceros bicornis ).
Comparative cranial and body measurements are presented for the northern subspecies ( Ceratotherium simum cottoni ).     

Relation of dental wear to the concentrations of essential minerals in teeth of the California sea lion <Emphasis Type="Italic">Zalophus Californianus Californianus</Emphasis>

Tooth wear in marine mammals has been attributed to age, feeding habits, behavior, and contaminants. Advanced tooth wear in some California sea lions, including some of very young age (<5 yr), in the Gulf of California, suggests that there are variations in chemical composition of tooth parts, wherein the concentrations of certain trace minerals might be anomalous, making them more susceptible to erosion. The concentrations of the essential minerals Ca, P, K, Na, Fe, Mg, and Zn in the dentition of Zalophus c. californianus are documented for the first time and are compared for sea lion teeth with different degrees of wear. Canine teeth and molars from 45 skulls collected at 15 localities since 1978 were digested in perchloric acid and analyzed using atomic adsorption spectrometry, the results being expressed in milligrams per 100 g. An index of tooth wear (Id) was established, involving the average wear on the teeth and the age of the organism. No significant difference was detected in the variables, but there was one between ages (p=0.02). A higher degree of wear was observed up to 7 yr of age than from this age onward. Mineral concentrations did not explain the excessive wear observed (correlation, p>0.09; ANOVA, p>0.15); however, the Ca concentration of the teeth was inversely proportional to the age of the animal (sexes combined, p=0.026) and particularly significant for the females (r ²=0.112, r=−0.335, p=0.039). Females could be more prone to decalcification because of their annual bone investment in their offspring. Animals of both sexes were susceptible to tooth wear as their age increased, but the higher frequency of animals between 4 and 7 yr suggests an impact on survival at early stages probably linked to deficient feeding and chronic malnutrition.     

Intrapopulation variation in macro tooth wear patterns—a case study from Igloolik,Canada

The pattern of human tooth wear—the way it varies between teeth in the mouth—is crucial to our understanding of important questions in archeology and paleoanthropology, such as the contrasts in diet and behavior between Neanderthals and early modern humans in Europe and Asia, or with the adoption of agriculture in the Americas. Little is known, however, about the way in which wear patterns develop with increasing age or the way in which they differ between males and females. One explanation is that few living people show the high rates of tooth wear seen worldwide throughout the preindustrial archaeological record. The study described here investigates the macroscopic pattern of tooth wear in a unique group of known age and sex dental casts from living Canadian Inuit from Igloolik. The results show that the Igloolik people possessed a pattern of extremely heavy anterior tooth wear, relative to the first molar and the other posterior teeth, which is attributed to the use of the anterior teeth in cultural practices as well as the extreme and marginal environments in which they lived. Heavy anterior tooth wear was established at an early age and maintained throughout life; statistically significant differences were found between the wear patterns of males and females and are explained in terms of sexual division of labor within the community. This study highlights the need to understand both intra‐ and interpopulation variation in tooth wear patterns when interpreting patterns in past human groups. Am J Phys Anthropol, 2012. © 2012 Wiley Periodicals, Inc.     

Cheek tooth erosion in male babirusa (genus Babyrousa)

The wear on the occlusal surfaces of male babirusa cheek teeth was evaluated in 53 skulls of Babyrousa babyrussa from Buru and the Sula Islands and 87 skulls of B. celebensis from Sulawesi, Indonesia. Based on the comparative lengths of their continually growing maxillary canine teeth, the skulls were divided into five ‘age categories’ (A–E). Numerical and symbolic codes representing tooth wear were applied to each pillar (cusp region) of the mandibular and maxillary permanent third and fourth premolar teeth, and the first, second and third permanent molar teeth. There was no significant difference between the tooth wear patters of skulls in groups A and B, or in groups C and D, and so these were amalgamated. There was close correspondence in wear patterns between each side of the mouth in both species and in each age group. The wear patterns of the mandibular and maxillary teeth, although not identical, were very similar, as were the wear patterns of both species. In group A + B for both species tooth wear was relatively slight, with the M1 teeth experiencing most relative wear. There was almost no wear of the M3 teeth. In group C + D substantial wear of upper and lower M1 was evident. In group E more widespread wear of the cheek teeth was seen, with increased severity of M1 tooth wear, yet there was comparatively much less M2 and M3 tooth wear. The pattern of cheek tooth wear of the Babyrousa spp. was different from that shown by Sus scrofa. Differences in diet selection and processing were highlighted as potential contributing factors. The pattern of cheek tooth wear in male babirusa was not adequate for use to monitor their age.     

Age determination in roe deer — a new approach to tooth wear evaluated on known age in dividuals

A novel, simple, and objective method is presented for ageing roe deerCapreolus capreolus (Linnaeus, 1758) evaluated on 471 lower jaws from roe deer of known age (351 with permanent premolars). It is based on tooth eruption patterns and presence/absence of wear characters in jaws from roe deer integrated in a scoring system. Permanent cheek teeth emerge in May–July in the year af ter birth, which enables precise age determination of individuals with deciduous premolars. For individuals with permanent cheek teeth, the method provides the correct age for all individ uals younger than 13 months and > 80% of all individuals between 13 and 24 months old. For older in dividuals the accuracy decreases, but decent accuracy is achieved to the age of 48 months. Males have higher wear rates than females corroborating recent documentation of sex-specific life history tactics in ungulates. The data originate from two separated Danish roe deer populations exposed to contrasting habitats, but no difference in wear rate is found between populations. Thus, previous concern about the validity of age determination methods based on tooth wear may have been overstated. The findings demonstrate that objective measures of tooth wear can provide the basis for age determination in ungulate species that are otherwise difficult to age.     

Patterns of approximal wear in cheek teeth of a Romano-British population

The approximal surfaces of premolars and molars of 376 adult British-Romano skulls were examined for wear facets. The type of wear was designated as convex, concave, sigmoid, or flat, and the degree was categorised on a three-point scale. Concave wear facets were more frequently seen in the older age groups, but the type of wear was similar on right and left sides. Taking all teeth together or as individual tooth types, concave wear was significantly more likely on mesial rather than distal surfaces. The degree of wear was age related and similar on right and left sides in both males and females. It is suggested that the distribution of concave facets may be related to movements between adjacent teeth.