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 ).     

Age determination of the African buffalo, Syncerus coffer (Sparrman) in Zimbabwe

Age determination methods using teeth are described for African buffalo in Matusadona National Park, Kariba, Zimbabwe. Tooth eruption stages and age classes for sub-adult animals were established by reference to a seasonal breeding peak and known dates of death. Teeth in adult animals were allocated age classes based on wear using measurements of crown height and by reference to previously published material. Layering in the dental cement indicated the deposition of one cementum line per annum and line counts were used to assign chronological ages to individual animals. Regressions of wear on age were confirmed by independent counts of cementum lines using a predictive wear model.     

AGEING THE UGANDA DEFASSA WATERBUCK KOBUS DEFASSA UGANDAE NEUMANN

Chronological ages have been assigned to the defassa waterbuck of western Uganda using four complementary techniques. These are the "jaw board" method in which collected skulls are sorted into arbitrary groups based upon tooth eruption and attrition; tooth impressions taken from immobilised animals at yearly intervals; counting of cementum lines in sectioned incisor teeth, and growth of horns in young males. Using these methods an animal could be aged to within plus or minus six months.     

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.     

The biology of cementum increments (with an archaeological application)

Cementum, a bone-like tissue that surrounds the roots of teeth, anchoring them to the periodontal ligament, is useful for determining the age at and season of death of mammals, an issue of concern for both archaeologists and biologists. When a tooth is sectioned and examined microscopically, cementum appears in bands that differ in their optical properties and are well correlated with seasonal growth. Because it is a continually deposited tissue that is rarely modified or resorbed, cementum records the history of a variety of seasonal factors that affect its growth. An understanding of the biological nature of cementum is crucial to the identification of these factors and interpretation of the resulting incremental structure. This paper outlines current knowledge of the development, histology and function of cementum in the context of the mammalian masticatory apparatus. Of the various types of cementum, acellular cementum is often more appropriate for seasonal correlations. Differences between acellular cementum increments are probably related to specific dietary factors that often vary between seasons. Cellular cementum increments probably result from phasic cementogenesis triggered by tooth eruption. This paper outlines a study of cementum bands in Gazella gazella for which there is an excellent correlation between the season of death and incremental structures in their cementum. This correlation can be used to estimate the season of death of gazelles from archaeological sites in the Levant. Problems for future research are outlined.     

The evolution of human periodontal tissues with ageing.

In this research, the structural modifications with ageing of clinically healthy periodontal tissues were analyzed by means of polarization microscopy and morphometrical methods for light microscopy. The new findings may be summarized as follows. The periodontal ligament was found to be widened in the cervical and apical regions. The thickening of cementum with ageing was shown to be accompanied by a modification in the shape of Sharpey's fibres, which in the elderlies were wavy instead of straight as in the control. Lamellar bone, forming an osteone, was found to substitute in part for cementum in one tooth. These results are interpreted as indicating that: (1) late active eruption occurs in man, causing the observed modification in the thickness of periodontal ligament and cementum in the apical region and in the direction of Sharpey's fibres within cementum; (2) cementum may undergo renewal during lifetime and in this case bone may be deposited in contact with dentin.     

Determination of age in the Japanese monkey from growth layers in the dental cementum

The teeth of 14 Japanese monkeys (Macaca fuscata) were examined to establish an exact method of determining age by histological observation of dental cementum. The cementum showed annual growth layers, which were especially remarkable in the incisor root and in the molar cementum deposited at the junction of the roots. The layer of cementum formed in winter appears as a dark layer in stained sections and as a translucent layer in unstained ground sections. In the incisor the first dark and light layers are formed at the age of three years, whereas in the molar they do not appear at a definite age. The layers are thick and clear in the upper medial incisor. As a result, the age of a Japanese monkey can be determined by adding two to the number of dark layers and an outer light layer. It is interesting that the formation of the cementum of the first molar begins a few years after its eruption. The relation between this fact and the pressure of occlusion is discussed.     

Dentition and age determination of the giraffe Giraffa camelopardalis

Thirteen tooth eruption stages and their corresponding chronological ages are descri bed from a series of giraffe jaws. These can be used for age determination in giraffes with immature dentition. Significant correlations of the lingual crown height ( r =0-957; P < 0001) and lingual occlusal surface width ( r =0-959; P < 0001) with the number of dark staining incremental lines in the cementum of thin decalcified sections of the maxillary first molar were found. The regression equations derived from these relationships provide a further method for determining the age of a giraffe. A composite plate showing maxillary first molar wear patterns provides a means of roughly assigning an age to a particular specimen. Thin sections of undecalcified teeth, mandible measurements, various other indices of tooth wear and eye lens mass were investigated and found unsuitable for age determination in this     

Longevity and life history of cave bears – a review and novel data from tooth cementum and relative emergence of permanent dentition

Abstract

Longevity and other life history variables are key to understanding evolutionary processes and the biology of extinct animals. For the past 20 years, the lifespan of cave bears received an increased interest. Studies focusing on incremental lines of tooth cementum resulted in detailed mortality patterns from different localities. In this review, we summarise literature on age estimation as well as mortality of different European cave bear localities and present novel data on longevity from 94 teeth originating from 20 European localities. Additionally, the relative tooth emergence pattern of the permanent dentition is investigated under the Schultz’s rule framework of possible life history implications. For this, the known sequences of extant bear species are compared with the one of cave bears. Our results suggest that the typical duration of the life of cave bears was 19 years but data from literature show that in rare cases ages of up to 30–32 years were achieved. Additionally, we present the oldest known age for the Middle Pleistocene cave bear Ursus deningeri, 29 years. The tooth eruption pattern of cave bears exhibits a heterochronic shift that implies, under the assumption of Schulz’ rule, a slightly faster life history than closely related species.     

Age determination and body growth of the Common duiker Sylvicapra grimmia(Mammalia)

Age determination in the Common duiker Sylvicapra grimmia was investigated by analysis of tooth eruption and replacement sequence, incremental lines of tooth cementum and tooth wear in a unique collection of 48 known-age skulls, and also by analysis by post-natal body growth in known-age duiker. In both the mandible and maxilla, permanent molariform teeth were fully erupted and in wear by 26 months of age. There was little variation in the age of eruption and replacement of all molariform teeth, making this a particularly useful feature of the duiker for age determination purposes. In contrast, the variability in eruption of the incisiforms, coupled with the difficulty in distinguishing deciduous incisiforms from the permanent counterparts, placed an unexpected limitation on the use of these teeth. Although the apparent linear relationship between tooth attrition and age has potential for further investigation as an age determination technique, the cementum annuli were not correlated with chronological age. Theoretical Von Bertalanffy equations were used to analyse body growth with age. It was concluded that because the asymptote of growth was reached at such an early age, and because there is so much individual variation in growth, body growth, including horn growth, is of very limited value for age determination. Female duiker were significantly larger than males.     

EVALUATION OF AN EFFECTIVE METHOD TO ESTIMATE AGE OF CAPE FUR SEALS USING GROUND TOOTH SECTIONS

Teeth of known-age Cape fur seals Arctocephalus pusillus pusillus were used to validate age estimated from ground sections. In the canines, dentine growth layer groups (GLGs) reflected age accurately but no reliable readings could be obtained from GLGs in the cementum. Upper canines were the most suitable for age estimation. By contrast, in the postcanines where the cementum is thicker, only GLGs in the cementum could be used for age determination, but not with the same accuracy as for dentine in the canines. Therefore, it is recommended that GLGs in the dentine be used to determine age in the Cape fur seal. However, pulp cavities in canines closed at about 13 yr and consequently GLGs in the cementum of the postcanines should be used where the pulp cavities of canines are closed. Accurate estimation of age is not possible from the dentine of older animals.     

MANDIBULAR DENTAL ONTOGENY OF RINGED SEALS (PHOCA HISPIDA)

X-rays of mandibles from ringed seal fetuses ( n = 15), newborns ( n = 12), and young-of-the-year ( n = 11), collected up to early June, were examined for the presence, location, and eruption patterns of deciduous and permanent teeth. The presence of a neonatal line and cementum in permanent canines was determined microscopically. Fetuses sampled in October-November had only unerupted, deciduous tooth germs, but by late January there were robust, deciduous teeth at il-2 pc2-4 and small permanent teeth at 11-2 Cl PCl-5. In newborns collected in early April, 109 of 143 (76%) deciduous teeth were resorbed completely. The remaining 34 deciduous teeth were partially resorbed; six (18%) had erupted and likely would be shed. By late April young-of-the-year had no deciduous teeth remaining. In newborns 54% of the permanent teeth (102/188) were erupted < 2 mm, and by late May the permanent dentition was erupted fully. The neonatal line first appeared in the canine teeth of young-of-the-year collected in mid-April and was 100% present after early May. There was no cementum apparent on any canine collected up to early June. Two seals were missing one and two permanent incisors, respectively. No supernumerary teeth or morphological variants were observed.     

The relative age structure and body masses of complete wild-captured colonies of two social mole-rats, the common mole-rat, Cryptomys hottentotus hottentotus and the Damaraland mole-rat, Cryptomys damarensis

The relative ages of individuals in a complete wild-captured colony of 13 Cryptomys hottentotus hottentotus and a complete wild-captured colony of 25 Cryptomys damarensis were determined by means of tooth wear and eruption patterns and through the degree of ossification of their skeletons.
From sequential tooth wear and eruption patterns four relative age classes were discerned in C. h. hottentotus and five in C. damarensis . These relative age class allocations were supported by the studies on the ossification of the skeletons.
In C. damarensis , older animals are not necessarily the larger-sized individuals. In C. h. hottentotus , however, older animals are usually the larger-sized individuals. The reproductive pair in each of the Cryptomys species are the oldest or amongst the oldest individuals in the colony.
Individuals in a second colony of C. damarensis kept under laboratory conditions for three years maintained greatly disparate body masses which were correlated with the role of the individual within the colony and not, where it was known, with the age of the animal.
An analysis of 13 body and skull measurements performed on a complete colony of 13 C. h. hottentotus and a complete colony of 25 C damarensis revealed that only C. damarensis showed sexual dimorphism. This dimorphism was apparent from an early age but became more pronounced in older animals.     

Evaluation of Preparation, Staining and Microscopic Techniques for Counting Incremental Lines in Cementum of Human Teeth

Apposition of cementum occurs in phases resulting in two types of layers with different optical and staining properties that can be observed by light microscopy. Narrow, dark staining incremental lines are separated by wider bands of pale staining cementum. The distance from one line to the next represents a yearly increment deposit of cementum in many mammals, and counting these lines has been used routinely to estimate the age of the animals. Incremental lines in cementum have also been observed in sections of human teeth, and the object of the present investigation was to examine a number of methods for preparing and staining them for counting. Longitudinal and transverse sections, either ground or decalcified, were cut from formalin fixed human dental roots, paraffin embedded or frozen, and stained using several techniques. The cementum was investigated using conventional light, fluorescence, polarized light, confocal laser scanning, interference contrast, phase contrast, and scanning electron microscopy. Incremental lines in the cementum could be observed in ground sections and, following decalcification, in both frozen and paraffin embedded sections. Toluidine blue, cresyl violet, hematoxylin, or periodic acid Schiff (PAS) stained incremental lines allowing differentiation by conventional light microscopy. Contrast was best using fluorescence microscopy and excitation by green light since the stained cemental bands, but not the incremental lines, fluoresced after staining with cresyl violet, PAS or hematoxylin and eosin. The results with other microscopic techniques were unsatisfactory. Since incremental lines are not destroyed by acids and stain differently than the remaining cementum, it is likely that they possess an organic structure which differs from the cementum. Incremental lines in human dental cementum could be observed best using decalcified sections stained with cresyl violet excited by green light.     

Cementum annulation and age determination in Homo sapiens. II. Estimates and accuracy

The cementum annulation aging technique was evaluated in a sample of 80 clinically extracted premolars (age range 11–70 years). Demineralized thin sections (7μm) stained with hematoxylin were used. The correlation (r) between age and adjusted count (number of annulations added to age of tooth eruption) was 0.78 for the entire sample (N = 73) and 0.86 for a subsample in which teeth with periodontal disease were excluded (N = 55). Standard error of the estimates ranged from 4.7 to 9.7 years depending on sex and health status of the tooth. The technique provided significantly better estimates for females than for males. The overall inaccuracy (mean absolute error) of the technique was 6.0 years, with a bias (mean error) of 0.26 years. Reduced major axis regression of adjusted count on age produced a slope of 0.797 for the entire sample and 0.889 for the nonperiodontal disease subsample. These slopes are consistent with a hypothesis of annual deposition of cementum rings given a decrease in cementogenesis with increasing age.     

A new method for the automated age-at-death evaluation by tooth-cementum annulation (TCA)

A valid age at death estimation is required in historical and also forensic anthropology. Tooth cementum annulation (TCA) is a method for age at death estimation of adult individuals. The method is based on light microscope images taken from tooth-root cross sections. The age is then estimated by manually counting the cementum incremental lines and adding this to the chronological age at the assumed point of tooth eruption. Manual line counting, however, is time consuming, potentially subjective and the number of individual counts is insufficient for statistical evaluations. Software developed for the automated evaluation of TCA images, that uses Fourier analysis and algorithms for image analysis and pattern recognition is presented here. It involves "line-by-line" scanning and the counting of gray scale peaks within a selected region-of-interest (ROI). Each scanning process of a particular ROI yields up to 400 counts that are subsequently statistically evaluated. This simple and time saving program seeks to substitute manual counting and supply consistent and reproducible results as well as reduce the demand of human error by eliminating unavoidable factors such as subjectivity and fatigue.     

Reconstructing the reproductive history of female polar bears using cementum patterns of premolar teeth

Premolar teeth collected from 220 adult female polar bears (Ursus maritimus) from western Hudson Bay, Canada, were examined to determine whether past reproductive events are recorded in cementum. The widths of annular cementum growth layer groups (GLGs) were measured and compared as proportional width index (PWI) values to correct for age and body size bias. Known reproductive states (pregnant, with cubs, or with yearlings) were used to confirm and calibrate cementum annuli. Significant differences in PWI were observed between GLGs formed the year females were pregnant versus when accompanied by cubs or yearlings. The probability of a female having produced a cub in adulthood was determined by fitting a logistic regression model between the ΔPWI of females when pregnant and with their cubs. Logistic regression of ΔPWI (β₀ = −0.229, β₁ = −13.465, G ² = 46.55, df = 1, P < 0.001) correctly classified the presence or absence of cubs in 72% of GLGs. Cementum width did not vary between different litter sizes. Observations of females with early litter loss suggests that longer periods of lactation contributes to decreased cementum width and therefore cementum may record a minimum age of litter survival. Predictions of litter production rate (0.43 litters/female/year) derived from cementum were similar to field observations; however, age at first parturition was underestimated by 1 year. We conclude that patterns of cementum deposition may be useful to determine individual reproductive histories and establish course estimates of reproductive parameters when regular field observations are not feasible. We also conclude that reproductive parameters derived from cementum are not adequate on their own for monitoring populations which are in decline or under stress and field observation should not be replaced under these conditions.     

Cold stress in captive great apes recorded in incremental lines of dental cementum

Incremental lines in dental cementum of museum specimens of 11 free-ranging great apes were compared to the respective structures in 5 captive specimens of known age-at-death, and with many known life-history parameters. While the dental cementum of the free-ranging apes was regularly structured into alternating dark and light bands, 4 out of 5 captive animals showed marked irregularities in terms of hypomineralized bands which could all be dated to the year 1963. Cementum preservation was insufficient in the fifth specimen and did not permit such a differentiation. All 4 captive apes had been kept in a zoo located in the northern hemisphere, where 1963 was characterized by an extremely cold winter. Since cold stress is a calcium-consuming process, the lack of available calcium in newly forming cementum could be responsible for the observed hypomineralization. The appositional growth characteristics of dental cementum serve as a record for such life-history events.     

Teeth as indicators of age with special reference to Red deer (Cervus elaphus) of known age from Rhum

An experiment in land management and Red deer population control was begun by the Nature Conservancy on the Isle of Rhum, a National Nature Reserve off the west coast of Scotland, in 1957. To assess the results fully it has become necessary to determine the most suitable ageing method which can be applied to the material, which has accumulated since from the annual deer culls and natural deaths.
Using mandibles only from individuals, whose age was certainly known by marking at birth, and which, in most cases were shot by mistake during subsequent annual culling operations, four different techniques were critically tested. These comprised correlating various combinations of jaw and tooth measurements with age, examining the nature and quantity of secondary dentine deposited within the crown of the first incisor, interpreting the number of layers in the pad of cementum beneath the crown of the first molar, and assessing the stages reached in tooth replacement, eruption and wear. Of these various methods, ageing by tooth replacement, eruption and wear proved the most reliable.     

Tooth Eruption Sequences in Cervids and the Effect of Morphology,Life History,and Phylogeny

Tooth eruption sequences vary in a non-random way among mammalian species. Several variables have been linked to this, including tooth and jaw shape, adaptations to diet, and food processing. Likewise, changes in eruption patterns correlate with the speed of postnatal growth in some groups, the Schultz’s Rule pattern. Here, the eruption pattern of the permanent dentition in lower jaws from different cervid species have been investigated to discern the effect of these factors and phylogeny as well as to reconstruct the ancestral tooth eruption sequence of cervids. In ruminants, the different patterns of emergence of permanent teeth seem to be best explained by phylogeny. The degree of hypsodonty, age of first molar eruption, and life history parameters such as longevity and age of female sexual maturity do not explain the observed sequential differences in eruption patterns. The Parsimov-based analysis for the ancestral state resulted in a tooth eruption sequence of m1 – m2 – i1 – i2 – i3 – c – m3 – (ppp) for Cervidae; a pattern recorded in Odocoileus, Capreolus, and Hydropotes. The eruption pattern of Caenomeryx filholi, from the Oligocene of Gaimersheim, is identical to the result of the Parsimov-based analysis except for the presence of a first premolar, a tooth lost in cervids.