Cementum Annuli Research Articles

A simple, low-cost method to age mammals? An alternative to cementum annuli analysis.

One of the most common and ubiquitous methods to age mammals is by counting the cementum annuli in molars, premolars, incisors, or canines. Despite the ubiquity and perceived simplicity of the method, cementum annuli analysis can be time-consuming, expensive, inaccurate, and imprecise, and require specialized equipment. Using beavers (Castor canadensis) as a test species, we developed a straightforward method to age mammals that requires little specialized equipment. The method consists of: (1) digitizing longitudinally sectioned teeth and measuring the proportion of tooth surface area comprised of cementum ("proportion cementum"), (2) evaluating the relationship between proportion cementum and specimen age (determined from either known-age samples or cementum annuli analysis), and (3) using the modeled relationship to estimate the age of other individuals based solely on proportion cementum. The relationship between proportion cementum and age was strongly correlated (R 2=.97-.98 depending on observer), similar between observers, and similar between known-age specimens and those aged via cementum annuli analysis. Using this proportion cementum method, two independent observers accurately predicted the age of 80%-84% of specimens within 0.5year and 96%-98% within 1year. We suggest this aging method will likely work with most mammal species given the relatively consistent deposition of cementum throughout mammals' lives and has promise to be a simple and quick alternative to cementum annuli analysis regardless of whether one develops proportion cementum models using known-age specimens or those aged via alternative methods.

Age estimation of Tiger Panthera tigris (Linnaeus, 1758) and Lion Panthera leo (Linnaeus, 1758) (Mammalia: Carnivora: Felidae): applicability of cementum annuli analysis method

We describe the applicability of the cementum annuli analysis technique for estimating the age of Tiger Panthera tigris and Asiatic Lion Panthera leo using incisor teeth. We used I2 and I3 incisor teeth from the right mandible of Tiger and I2 and I3 from the left premaxilla of the Lion. The longitudinal sections of the teeth were prepared using an economical hand grinding technique with the help of sandpaper, followed by decalcification and staining with hematoxylin. Two cementum layers were observed under the microscope in each of the I2 and I3 incisor teeth of the Tiger and six cementum layers were observed in each of the I2 and I3 incisor teeth of the Lion. The permanent incisors in Tiger and Lion erupt between 12 and 14 months of age; hence, we added one year to the counted number of cementum layers to estimate the final age of Tiger and Lion incisors. The age of Tiger and Lion incisors were estimated to be of three years and seven years, respectively. This method may be suitable for estimating other carnivores’ age and applicable in wildlife forensic studies.

Sex identification and age estimation of bobcats and implications for management

AbstractPredictions obtained from wildlife population models may be prone to influences associated with the quality of the data available for parameterization. We assessed accuracy of furtaker‐assigned sex of bobcats (Lynx rufus; n = 123) harvested during 2017–2018 across the western USA by comparing those data to genetically assigned sex, the latter of which we assumed was 100% accurate. We also compared the precision of individual age estimates obtained through cementum annuli analysis (CAA) of the canines and incisors of harvested bobcats (n = 151), where true age was unknown. Because cementum‐line deposition may vary across populations and by sex, we hypothesized that environmental factors may affect precision of age estimates obtained via CAA. Sex of bobcats as reported by furtakers was accurate 82% of the time, and the direction of sex‐assignment error was approximately equivalent. Canine teeth were more precise than incisors for estimating age, age estimates for male bobcats may be more precise than for females, and precision of age estimates may decrease with age. However, use of incisors corrected with known rates of error may be preferred in some instances, such as studies that require live capture and tooth extraction or where assignment to age class is sufficient. In addition, we found that sex, median age, and mean elevation may influence precision of age estimates, whereas mean precipitation and geographic location (latitude, longitude) were uninformative. Knowledge of different types of errors associated with sex identification and age estimation may be integrated into population modeling efforts based on management objectives.

Evaluation of Gum‐line Recession for Aging Lynx (Lynx canadensis)

ABSTRACTAccurate age estimates of wildlife are important for both research and management purposes. Despite the value of determining the age of individuals, cost effective and minimally‐invasive approaches are lacking for most species. Assessment of gum‐line recession is a minimally‐invasive, cost‐effective method used for aging some felids; however, its reliability is unknown. Here, we evaluate the utility of gum‐line recession for aging Canada lynx (Lynx canadensis), using carcasses collected during the winters of 2015–2016 and 2016–2017 from trappers in Yukon, Canada. The purpose of our study was to 1) assess the repeatability of measuring gum‐line recession within and between observers, 2) compare measurements of gum‐line recession to estimates of age obtained from cementum annuli analysis, and 3) test for differences in mean gum‐line recession between age‐classes of lynx (i.e., young, prime adult, and old adults). We found that although estimated gum‐line recession was repeatable within an observer, it was not between observers, and did not correlate strongly with estimated age based on cementum annuli. Significant differences in mean gum‐line recession were found between age classes. We conclude that gum‐line recession does not provide an accurate estimate of age in Canada lynx and that other methods would be required if tooth extraction is not desirable. However, gum‐line recession may be useful for determining age class of lynx. Finally, we recommend similar assessments of precision and observer bias when measuring gum‐line recession to estimate the age of other species. © 2021 The Wildlife Society.

Aging Sambar (Rusa unicolor) Using Cementum Annuli and Eruption and Wear: Implications for Predicting Populations

ABSTRACTSambar (Rusa unicolor), one of 6 deer species introduced to Australia, are poorly studied and declared vulnerable in their native range of India and southern Asia. In southeastern Australia sambar are increasing in abundance and distribution despite commercial venison harvest and unlimited public hunting. The ability to accurately age individuals is important for management of cervid populations because many life history events are age dependent. The techniques most widely used to estimate the age of cervids involve tooth eruption and molar wear (EW), and interpretation of cementum annuli (CA) in incisors. Aging techniques based on teeth are influenced by diet, body condition and metabolic stressors such as disease and reproduction. We compared age estimation derived by both EW and CA techniques and applied age estimates from both methods to lifetables and the Euler‐Lotka equation to predict population growth. Sambar have CA that are discernible and correspond to midwinter despite calving throughout the year in a temperate environment. Age estimation by eruption times of molar teeth appears reliable in sambar but estimation based on wear patterns of molar teeth is less accurate than CA. Assuming CA is accurate, aging by EW was less than 30% for sambar 3 years and older. For management purposes, however, estimation of rates of population growth using either the Euler‐Lotka equation or a lifetable provided similar outputs using ages estimated by either CA or EW. © 2021 The Wildlife Society.

Accuracies and biases of ageing white-tailed deer in semiarid environments

Abstract Context The ability to accurately estimate age of animals is important for both research and management. The two methods for age estimation in ungulates are tooth replacement and wear (TRW) and cementum annuli (CA). Errors in estimated TRW ages are commonly attributed to environmental conditions; however, the influence of environmental variables on tooth wear has not been quantified. Further, the performance of CA in environments with weak seasonality has not been thoroughly evaluated. Aims The study had the following three goals: identify environmental and morphological factors that influenced estimated ages, quantify accuracy of TRW and CA, and develop TRW ageing criteria that minimise error. Methods We used data from harvested (n = 5117) and free-ranging, known-age white-tailed deer (n = 134) collected in southern Texas, USA, to quantify environmental and morphological influences on estimated TRW ages, and assess biases in both methods. Key results We observed substantial variation in age estimates for both TRW and CA. Soil, drought and supplemental nutrition had minor effects on tooth wear, insufficient to alter age estimates by ≥1 year. Body mass and antler size influenced age estimates for TRW only for extreme outliers. Both methods were biased and tended to under-estimate ages of adult deer, especially TRW. Wear on the first molar was most correlated with the known age (r2 = 0.78) and allowed biologists to correctly place known-age deer into age classes of 2, 3–5, and ≥6 years old 72%, 73% and 68% of the time, an improvement compared with the 79%, 48% and 28% accuracy from pooled TRW. Conclusions We observed substantial inter- and intra-individual variation in tooth-wear patterns that became more pronounced in older deer. Individual variation had a greater influence on TRW ages than did environmental covariates, whereas CA ages appeared unaffected by environment. Although variable, age estimates were ±1 year of the true age 87% and 93% of the time for TRW and CA respectively. Implications Managers, ecologists and epidemiologists often incorporate ages into population models. The high inter-individual variation in estimated ages, the tendency to underestimate ages of older deer, and the ageing method need to be considered.

The accuracy and precision of age determination by dental cementum annuli in four northern cervids

Individual age is an important element in models of population demographics, but the limitations of the methods used for age determination are not always clear. We used known-age data from moose (Alces alces), red deer (Cervus elaphus), semi-domestic reindeer (Rangifer tarandus tarandus) and Svalbard reindeer (Rangifer tarandus platyrhynchus) to evaluate the accuracy and repeatability of age estimated by cementum annuli analysis of longitudinally sectioned permanent incisors. Four observers with varying experience performed blind duplicate age estimation of 37 specimens from each cervid. The relationship between known age and estimated age was linear, except for Svalbard reindeer where a quadratic model gave a slightly better fit. After correcting for observer ID and animal ID, there was a slightly declining probability to assess the correct age with increasing age for moose, red deer and Svalbard reindeer. Across cervids and observers, estimated age equalled known age in 69% of all readings, while 95% age ± 1 year. Predicted probability of correct age assessment for experienced observers was 93% for red deer, 89% for Svalbard reindeer, 84% for moose and 73% for semi-domestic reindeer. Regardless of observer experience and cervid, there was a high agreement between repeated assessments of a given animal’s tooth sections. The accuracy varied between cervids but was generally higher for observers with former ageing experience with a given cervid. We conclude that the accuracy of estimated age using longitudinally sectioned incisors is generally high, and even more so if performed by observers with former ageing experience of a given species. To ensure consistency over time, a reference material from known-age individuals for each species analysed should be available for calibration and training of observers.

Precision of cementum annuli method for aging male white-tailed deer.

The most common method used to estimate ages of harvested white-tailed deer (Odocoileus virginianus) and other cervids is a criterion based on tooth replacement-and-wear (TRW). Previous studies have shown this method is prone to considerable error because TRW is partially subjective. A presumably more accurate, but more labor intensive and expensive, method to estimate age involves the counting of cementum annuli (CA) of cross-sectioned incisors. Quantifying rate of error of the CA aging method is not possible without known-aged specimens, but precision of duplicate CA age estimates for two teeth may be related to accuracy if identical factors influence both CA accuracy and precision. The objective of this research was to identify and assess factors affecting precision of paired CA ages as well as evaluate congruence between TRW and CA age estimates. We obtained paired CA age estimates from a laboratory specializing in CA aging for 473 adult (≥ 1 year old), male white-tailed deer harvested in Iowa (USA; 2014–2018). Not all CA age estimates of paired incisors agreed with one another and probability of agreement between the paired CA ages decreased as the certainty level of the CA ages provided by the laboratory decreased and was dependent upon the batches in which they were aged by the laboratory. We also estimated the age of 1,292 adult, male deer using both TRW and CA methods and compared the congruence between the TRW and CA age estimates. Congruence rates of CA and TRW ages differed among age classes (80% congruence in yearling TRW age classification, 65% with 2-year-olds, 78% with ≥3-year-olds). Our results showed that CA aging is imperfect and that the certainty level is an important factor to consider with CA ages, as shown in previous research, as is the batch in which the teeth were aged. We also confirmed previous studies’ findings that CA and TRW ages for adult deer are not always congruent, particularly in age classes other than the yearling age class. Our results suggest managers are best served by using TRW to age adult deer as yearlings or ≥2-years-old. If additional age classes are required, CA aging is likely to be a better tool than TRW.

Non-Invasive Age Estimation by Cranial Suture Closure in Japanese Sika Deer (Cervus nippon)

Although counting cementum annuli of lower incisor is a reliable method for age estimation in cervids, it inevitably involves the destruction of specimens. Here we studied the relationship between cranial suture closure patterns and age to test the possibility of cranial suture closure as a non-destructive age indicator in sika deer (Cervus nippon) specimens from Kinkazan Island, Japan, for which extensive life records were available. A strong positive relationship between the sum of suture closure level scores and age was found. We found that this relationship was even stronger than the relationship between age and the crown height of the first molar, which is frequently used for non-destructive age determination. Our study highlights the potential of cranial suture closure as an alternative valid tool for age estimation.

Does hard mast production affect patterns of cementum annuli formation in premolar teeth of Asian black bears (Ursus thibetanus)?

Cementum annuli widths in mammals are is influenced by the nutrition of mammals. Reproductive stress has been is suggested to reduce the width of lead to narrower cementum annuli widths in female Asian black bears (Ursus thibetanus); however, food availability in autumn strongly impacts bear nutrition and likely impacts cementum widths as well. This study aimed to test how cementum annuli widths and the formation of false annuli were influenced by hard mast production. We established two hypotheses: (1) cementum annuli widths become narrower in poor mast years owing to inadequate nutritional conditions and (2) false annuli occur more frequently in poor mast years. We used teeth samples from male bears to avoid reproductive influences and separated width data into “adult” and “subadult” groups. We calculated the proportional width index (PWI) and used linear mixed models to estimate the masting effects on PWI. Generalized linear mixed models estimated the masting effects on false annuli frequency. True annuli widths and false annuli formation showed no significant relationship with mast production in adults. In subadults, poor mast production weak negative influence on false annuli formation. These new data resolve previous questions, allowing us to deduce that cementum annuli widths are a reliable index of reproductive success in female bears.

Reproductive Histories of Asian Black Bears Can be Determined by Cementum Annuli Width

Very little is known about the cementum annuli of Asian black bears (Ursus thibetanus). We collected the first premolar tooth from adult female bears in central Japan to investigate whether reproductive history was reflected in cementum annuli width; previous studies have indicated that this is possible in other bear species. We calculated the proportional width index (PWI) value as an index of annular cementum growth, and we confirmed reproductive status by direct field observations (females with cubs, with yearlings, or without offspring). We compared both PWI and reproductive status among 10 females to determine whether PWI was correlated with reproduction. In years when females were accompanied by cubs, PWI was significantly smaller than in years when females were with yearlings or without offspring. Our results indicate that reproductive success (parturition and lactation) in female Asian black bears decreases cementum annulus width, which appears to be a useful index of past reproductive history. These data will improve our ability to determine this life-history parameter as we monitor and manage Japan's bear population. Linking other factors (e.g., food availability) to PWI could increase the accuracy of detection of cub survival by this reproductive success index.

Refining Aging Criteria for Northern Sea Otters in Washington State

AbstractMeasurement of skull ossification patterns is a standard method for aging various mammalian species and has been used to age sea otters Enhydra lutris from Russia, California, and Alaska. Cementum annuli counts have also been verified as an accurate aging method for sea otters in Alaska. In this study, we compared cementum annuli count results and skull ossification patterns as methods for aging the northern sea otter, E. l. kenyoni, in Washington State. We found significant agreement between the two methods, suggesting that either method could be used to age sea otters in Washington. We found that ossification of the squamosal–jugal suture at the ventral glenoid fossa can be used to differentiate male subadults from adults. To assist field biologists or others without access to cementum annuli or skull ossification analysis techniques, we analyzed a suite of morphologic, physiologic, and developmental characteristics to assess whether a set of these more easily accessible parameters could also predict age class. We identified tooth condition score, evidence of reproductive activity in females, and tooth eruption pattern as the most useful criteria for classifying sea otters in Washington. We created a simple decision tree based on characteristics accessible in the field or at necropsy, which can be used to reliably predict age class of Washington sea otters as determined by cementum annuli. These techniques offer field biologists and marine mammal stranding networks a replicable, cost-conscious methodology to gather useful biological information from sea otters.

Benefits and drawbacks of determining reproductive histories for black bears (Ursus americanus) from cementum annuli techniques

Recruitment is difficult to estimate but is essential for determining population trend. Recruitment in bears can be estimated from patterns in width of cementum annuli that indicate years with cubs. We evaluated reproductive history estimates from cementum annuli of 19 101 black bears (Ursus americanus Pallas, 1780) collected over 20 years to determine the benefits and drawbacks of this technique for management agencies. The technique only worked to estimate reproductive histories for 25% of submitted samples, and 49% of samples with estimates contained uncertain litters. Whether uncertain litters were counted or not caused significant variation in estimates of age at first litter, number of litters per female, and interbirth intervals. Hence, naive treatment of uncertain litters may bias analyses. A data set we optimized to reduce bias showed that litters per female ranged from 0 to 12, mean interbirth interval was 2.07 years, and both increased as females aged. Large samples of teeth collected from harvested bears over multiple decades potentially provides a wealth of information on reproductive parameters at a minimal cost compared with intensive field studies, but until uncertain litters are understood mechanistically and can be better quantified, reproductive estimates from this technique should be interpreted with caution.

Ringed seal (Pusa hispida) tooth annuli as an index of reproduction in the Beaufort Sea

Multi-decadal time-series of biological indices that reflect the state of a population are rare in ecological studies, but invaluable for assessing environmental regulation of population dynamics. We utilized canine teeth extracted from ringed seals (Pusa hispida) killed by polar bears (Ursus maritimus) in the Beaufort Sea, Canada, in 1985–2011, to obtain widths of annual growth layers in the cementum. Canine teeth for 75 individuals were measured and compared across years using a proportional width index (PWI) spanning 1965–2007. PWI was positively correlated with ringed seal ovulation rate obtained independently from other studies and was significantly lower than normal during ringed seal reproductive declines in 1974–75, 1984–87, 1991–93, and 2004–05, suggesting that PWI reflects ringed seal reproductive capacity. The PWI was also examined against climatic and sea ice factors to assess environmental regulation of ringed seal reproduction. Results suggest that ringed seals benefit from cyclonic circulation regimes in the Beaufort Sea, and an earlier breakup of sea ice in summer that may positively influence the quality and quantity of food during the open water season. Results highlight how cementum annuli in the canine teeth of ringed seals can provide an index of body state and linkages to sea ice conditions. Canine teeth from ringed seals can function as a means to monitor the effects of past Arctic marine variability on area-specific populations for which there are few independent empirical data.

Effects of removal on a lightly exploited coyote population in eastern Nevada

Coyote (Canis latrans) removal is a common, yet controversial, management practice to increase game populations throughout the West. I studied the effect of removal on coyote populations in eastern Nevada from 2004 to 2008 and reviewed 27 available publications to determine the level of human exploitation on my study populations. Removals were performed by USDA Wildlife Services (WS) to benefit game populations and involved the use of trapping, neck snaring, and ground and aerial shooting. To determine if the removal had an effect on the coyote populations, I measured 3 parameters: the presence or absence of skewed sex ratios; proportions of juveniles in the population; and average adult age. Sex was determined at the time of ground removal efforts. Canine teeth were acquired from 96% of coyotes removed from the ground; cementum annuli analysis was performed for aging. Due to WS removal efforts prior to 2004, coyote populations likely were in a lightly exploited state when the study began. Where removal efforts were the highest (65% of total), there was a resulting decline in the mean age of coyotes, an increase in percentage of juveniles in the population, and a skewed sex ratio, indicating that this population may be heavily exploited. No change in these parameters occurred in areas where 35% of the total removals occurred. This information should help wildlife managers understand the exploitation levels of their own coyote populations.

Estimating the Age of Male Gray Wolves (<i>Canis lupus</i>) Using Baculum Measurements

Morphological characteristics of the bacula of 62 Gray Wolves (Canis lupus) harvested in Wisconsin were related to age estimates generated from cementum annuli analyses. Baculum analysis suggested that 47 of 62 wolves (75.8%) were correctly classified as the appropriate age category (pup, yearling, adult) assessed by cementum analyses; however, this success was limited for yearlings (53.5%) and adults (38.5%). Results could not corroborate future use of this approach for rapid aging of dead wolves. there remains a need for a wolf-aging technique that can be broadly implemented in a timely and cost-effectivemanner, while also preserving the inherent trophy value of an intact skull.

Evaluation of the Applicability of Different Age Determination Methods for Estimating Age of the Endangered African Wild Dog (Lycaon Pictus).

African wild dogs (Lycaon pictus) are endangered and their population continues to decline throughout their range. Given their conservation status, more research focused on their population dynamics, population growth and age specific mortality is needed and this requires reliable estimates of age and age of mortality. Various age determination methods from teeth and skull measurements have been applied in numerous studies and it is fundamental to test the validity of these methods and their applicability to different species. In this study we assessed the accuracy of estimating chronological age and age class of African wild dogs, from dental age measured by (i) counting cementum annuli (ii) pulp cavity/tooth width ratio, (iii) tooth wear (measured by tooth crown height) (iv) tooth wear (measured by tooth crown width/crown height ratio) (v) tooth weight and (vi) skull measurements (length, width and height). A sample of 29 African wild dog skulls, from opportunistically located carcasses was analysed. Linear and ordinal regression analysis was done to investigate the performance of each of the six age determination methods in predicting wild dog chronological age and age class. Counting cementum annuli was the most accurate method for estimating chronological age of wild dogs with a 79% predictive capacity, while pulp cavity/tooth width ratio was also a reliable method with a 68% predictive capacity. Counting cementum annuli and pulp cavity/tooth width ratio were again the most accurate methods for separating wild dogs into three age classes (6–24 months; 25–60 months and > 60 months), with a McFadden’s Pseudo-R2 of 0.705 and 0.412 respectively. The use of the cementum annuli method is recommended when estimating age of wild dogs since it is the most reliable method. However, its use is limited as it requires tooth extraction and shipping, is time consuming and expensive, and is not applicable to living individuals. Pulp cavity/tooth width ratio is a moderately reliable method for estimating both chronological age and age class. This method gives a balance between accuracy, cost and practicability, therefore it is recommended when precise age estimations are not paramount.

Demographic structure of three riparian mustelid species in Spain

Age estimation of three mustelid species with similar body size was performed in Northern Spain. Canine samples of 1766 carcasses from 1661 American mink (Neovison vison), 54 European mink (Mustela lutreola), and 51 European polecats (Mustela putorius) were sectioned, and cementum annuli counts in tooth sections were used for age estimation. American mink samples consisted primarily of trap-captured animals from governmental control campaigns, whereas road casualties were the principal origin of European mink and European polecat carcasses. Individuals prior to their first breeding season (class 0+) represented approximately half of all animals, with no significant differences between species or causes of death. Differences in sub-adult percentages were observed between the pre- and post-reproductive period, with a high mortality during the dispersal-winter period in all three species. Frequencies of mortality of the sub-adult age class were 0.46, 0.50, and 0.55 for American mink, European mink, and European polecat, respectively. Survival rates of the American mink were higher than those of the native species. The oldest animals detected were 7+, 5+, and 3+ years old for the American mink, European mink, and European polecat, respectively. No differences were observed in mean age of animals found dead as road casualties in all three species or between captured American mink and road casualties. The information obtained is of high value for understanding the demographic processes of the populations and particularly for conservation and management decisions for these species.

Relationship Between Tooth wear and Age in the Japanese Black Bear in Hiroshima Prefecture, Japan

Some field studies and population management activities relating to the Japanese black bear (Ursus thibetanus japonicus) require noninvasive methods that can quickly provide an estimation of the age of living animals in the field. Nondestructive methods are also necessary when studying specimens that are part of museum or private collections. The most common method of age determination in this subspecies involves counting the tooth cementum annuli (e.g., Nozaki and Mizuno 1986; Amano et al.

Estimating ages of white-tailed deer: Age and sex patterns of error using tooth wear-and-replacement and consistency of cementum annuli

The age structure of harvested animals provides the basis for many demographic analyses. Ages of harvested white-tailed deer (Odocoileus virginianus) and other ungulates often are estimated by evaluating replacement and wear patterns of teeth, which is subjective and error-prone. Few previous studies however, examined age- and sex-specific error rates. Counting cementum annuli of incisors is an alternative, more accurate method of estimating age, but factors that influence consistency of cementum annuli counts are poorly known. We estimated age of 1,261 adult (≥1.5 yr old) white-tailed deer harvested in Wisconsin and Illinois (USA; 2005–2008) using both wear-and-replacement and cementum annuli. We compared cementum annuli with wear-and-replacement estimates to assess misclassification rates by sex and age. Wear-and-replacement for estimating ages of white-tailed deer resulted in substantial misclassification compared with cementum annuli. Age classes of females were consistently underestimated, while those of males were underestimated for younger age classes but overestimated for older age classes. Misclassification resulted in an impression of a younger age-structure than actually was the case. Additionally, we obtained paired age-estimates from cementum annuli for 295 deer. Consistency of paired cementum annuli age-estimates decreased with age, was lower in females than males, and decreased as age estimates became less certain. Our results indicated that errors in the wear-and-replacement techniques are substantial and could impact demographic analyses that use age-structure information. © 2014 The Wildlife Society.