Distribution and abundance of Indo‐Pacific humpback dolphins in Leizhou Bay,China

Abstract

The Indo‐Pacific humpback dolphin (Sousa chinensis) is under severe threat in Chinese waters. Only four small populations of this dolphin are known to survive in the East China Sea and South China Sea. We conducted exploratory surveys from June to September 2005, and found a population of humpback dolphins in Leizhou Bay. Thirty‐eight individuals were identified and catalogued, of which 26 were photographed and re‐identified on more than one occasion, and nine were sighted on five or more occasions each. Our preliminary estimate of the size of the Leizhou population is about 237 individuals, second only to the Pearl River estuary population. We suggest that Leizhou Bay has the potential to serve as a “humpback dolphin sanctuary” in Chinese waters.     

Mandibular growth in the rhesus monkey (Macaca mulatta)

Mandibular growth of 42 rhesus monkeys (Macaca mulatta) was analyzed quantitatively and qualitatively. Four groups of animals were defined according to dentitional age (i.e., infant, juvenile, adolescent, young adult). At each age growth was observed for a 24 week period. Since some animals were observed at more than one stage of development, 57 periods of growth were studied. The growth incremental data were collected by superimposing serial cephalograms on mandibular implants. Growth and remodeling of both the skeletal and dento-alveolar components of the rhesus mandible were greatest in the infant monkeys and were less in successive age groups. Posterior relocation of the ramus was noted in all age groups while bone deposition on the anterior and inferior borders of the mandibular body was greatest in the younger animals. The most pronounced dental changes also occurred in the younger animals while the dentitions of the adolescent and adult animals were generally more stable. This study demonstrates that the rate and direction of normal mandibular growth varies with the age of the animal. Furthermore, mandibular growth is quantified at four defined maturational levels to provide a set of values illustrating normal mandibular growth. These values can also be used as control data for experimental studies.     

Epigenetic estimation of age in humpback whales

Age is a fundamental aspect of animal ecology, but is difficult to determine in many species. Humpback whales exemplify this as they have a lifespan comparable to humans, mature sexually as early as 4 years and have no reliable visual age indicators after their first year. Current methods for estimating humpback age cannot be applied to all individuals and populations. Assays for human age have recently been developed based on age‐induced changes in DNA methylation of specific genes. We used information on age‐associated DNA methylation in human and mouse genes to identify homologous gene regions in humpbacks. Humpback skin samples were obtained from individuals with a known year of birth and employed to calibrate relationships between cytosine methylation and age. Seven of 37 cytosines assayed for methylation level in humpback skin had significant age‐related profiles. The three most age‐informative cytosine markers were selected for a humpback epigenetic age assay. The assay has an R² of 0.787 (P = 3.04e?16) and predicts age from skin samples with a standard deviation of 2.991 years. The epigenetic method correctly determined which of parent–offspring pairs is the parent in more than 93% of cases. To demonstrate the potential of this technique, we constructed the first modern age profile of humpback whales off eastern Australia and compared the results to population structure 5 decades earlier. This is the first epigenetic age estimation method for a wild animal species and the approach we took for developing it can be applied to many other nonmodel organisms.     

Humpback whale (Megaptera novaeangliae) and killer whale (Orcinus orca) feeding aggregations for foraging on herring (Clupea harengus) in Northern Norway

Aggregations of predators on food patches have been documented for both terrestrial and marine animals. Here, we documented for the first time, and investigated, non-predatory aggregations occurring between humpback whales (Megaptera novaeangliae) and killer whales (Orcinus orca) while feeding on wintering Norwegian spring spawning herring (Clupea harengus) in Andfjord, northern Norway. Observational data were collected during 109 opportunistic surveys through three seasons 2013–2016. Killer whales were observed feeding on 59 occasions, with one to three humpback whales involved in 47 of these feeding events (79.7%), and there was an increased probability of finding feeding humpback whales when feeding killer whales also were observed. With killer whales identified as the initiating species in 94.4% of the feeding aggregations for which the first species was known, and with humpback whales joining and feeding on the fish ball afterwards, we suggest that humpback whales may benefit more from these aggregations than the opposite.     

Accuracy and precision in estimation of age of Norwegian Arctic polar bears (Ursus maritimus) using dental cementum layers from known-age individuals

Validation of age estimation from tooth cementum growth layers was conducted for 32 polar bears (Ursus maritimus) of known age, by two readers. Both readers correctly estimated age for 24% of the bears, and 50–53% were within the year of correct age. The age of young animals (age 1–8) was overestimated, while ages for bears over 8 years were underestimated. Comparison between the readings of the two readers indicated that the precision was low. Further, one of the readers reread tooth slides earlier prepared and read by another age estimation laboratory. There was a large discrepancy between these readings indicating a bias in the ages estimated. We conclude that age estimation of polar bears can be difficult, particularly in populations where individuals may forage throughout the year. As tooth growth layers may deposit differently for bears from different areas, and as different laboratories may read the same slides according to different criteria, an evaluation of the methods should be conducted for all populations, based on a significant number of tooth slides, with a broad age range, from animals of known age.     

Making the most of survey data: Incorporating age uncertainty when fitting growth parameters

Individual growth is an important parameter and is linked to a number of other biological processes. It is commonly modeled using the von Bertalanffy growth function (VBGF), which is regularly fitted to age data where the ages of the animals are not known exactly but are binned into yearly age groups, such as fish survey data. Current methods of fitting the VBGF to these data treat all the binned ages as the actual ages. We present a new VBGF model that combines data from multiple surveys and allows the actual age of an animal to be inferred. By fitting to survey data for Atlantic herring (Clupea harengus) and Atlantic cod (Gadus morhua), we compare our model with two other ways of combining data from multiple surveys but where the ages are as reported in the survey data. We use the fitted parameters as inputs into a yield‐per‐recruit model to see what would happen to advice given to management. We found that each of the ways of combining the data leads to different parameter estimates for the VBGF and advice for policymakers. Our model fitted to the data better than either of the other models and also reduced the uncertainty in the parameter estimates and models used to inform management. Our model is a robust way of fitting the VBGF and can be used to combine data from multiple sources. The model is general enough to fit other growth curves for any taxon when the age of individuals is binned into groups.     

Age-based life history of humpback red snapper,Lutjanus gibbus,in New Caledonia

This paper examines the life history of humpback red snapper Lutjanus gibbus, an important fishery species for coastal communities across the Indo-Pacific, in southern New Caledonia, where the species is lightly exploited. A total of 243 L. gibbus were sampled between January 2013 and December 2016 from occasional harvests of commercial fishers. Examination of sectioned otoliths revealed that opaque increment formation occurred annually between November and March, coinciding with the species' spawning season. Estimates of maximum age were similar between sexes, with observed ages of 38 and 36 years for females and males, respectively, extending the reported longevity of this species by at least 11 years. Growth differed significantly between sexes, with males reaching greater length at age and greater asymptotic length than females (38.88 v. 31.46 cm fork length (L_F). Total mortality for all samples was estimated as 0.13 and was slightly higher for males (0.16) than females (0.11). Estimates of natural and fishing mortality were low and slightly higher for males than females. Male L. gibbus were found to mature at slightly greater lengths and younger ages than females, with the length and age at which 50% of individuals attained maturity estimated to be 25.8 cm L_F and 3.9 years of age for females and 26.8 cm L_F and 3.4 years of age for males. The results provide key baseline information from which to assess the effect of fishing on the species for populations in New Caledonia and adjacent locations and, when viewed with those of other studies, highlight the importance of understanding spatial patterns in demography of harvested fish species across gradients of exploitation and environmental influences.     

Effect of male and female age on the mating success of the obliquebanded leafrollerChoristoneura rosaceana (Lepidoptera: Tortricidae) under different ecological conditions

The present study was undertaken to test the hypothesis that male and female age, as well as temperature, can affect the mating success ofChoristoneura rosaceana, given the role that these two factors play in the pheromone biology of this species. In the laboratory, the mating success of females generally declined linearly with age, whereas in males, it increased during the first 3 days and then decreased. The decline in female mating success was more pronounced under warm than cool thermocycles, while the changes observed in males were greater under fluctuating than constant temperature regimes. The onset time of mating was unaffected by male age, however, older females always mated earlier than younger ones, with the advance being more pronounced at cool than warm temperatures. Similar results were also obtained under field conditions. When a single 3-day-old male was provided with 0-, 3-, and 5-day-old females simultaneously, older females obtained mates significantly more often than younger individuals at all temperatures, indicating that calling earlier may afford a reproductive advantage to older females. At both constant temperatures, the time spent mating was longer in older than in younger females, but not under fluctuating thermocycles. Very young and very old males generally spent more time in copula than middle-aged individuals both at constant temperatures and under the warm thermocycle. Under the cool thermocycle, the duration of mating was considerably prolonged at all ages, which could increase the risk of predation.     

THE EQUIVALENCE OF AGE IN ANIMALS

1. A method of plotting growth curves is presented which is considered more useful than the usual method in bringing out a number of important phenomena such as the equivalence of age in different animals, difference in the shape and duration of corresponding growth cycles in different animals, and also in determinating the age of maxima without resorting to complicated mathematical computations. 2. It is suggested that after the third cycle is past the conceptional age of the maximum of the third cycle may be taken as the age of reference for estimating the equivalent physiological ages in different animals. Before the age of the third cycle, the maxima of the second and first cycles are most conveniently used as points of reference. 3. It is shown that the product of the conceptional age of the maximum of the third cycle by 13, gives a value which is, with the possible exception of man, very near to the normal duration of life of animals under the most favorable conditions of life. In other words, the equivalent physiological ages in different animals bear an approximately constant linear relation to the duration of their growth periods. 4. Attention is called to certain differences in the shape and duration of the corresponding growth cycles in different animals and of the effect of sex on these cycles.     

Segmented Bayesian calibration approach for estimating age in forensic science

Forensic age estimation is receiving growing attention from researchers in the last few years. Accurate estimates of age are needed both for identifying real age in individuals without any identity document and assessing it for human remains. The methods applied in such context are mostly based on radiological analysis of some anatomical districts and entail the use of a regression model. However, estimating chronological age by regression models leads to overestimated ages in younger subjects and underestimated ages in older ones. We introduced a full Bayesian calibration method combined with a segmented function for age estimation that relied on a Normal distribution as a density model to mitigate this bias. In this way, we were also able to model the decreasing growth rate in juveniles. We compared our new Bayesian‐segmented model with other existing approaches. The proposed method helped producing more robust and precise forecasts of age than compared models while exhibited comparable accuracy in terms of forecasting measures. Our method seemed to overcome the estimation bias also when applied to a real data set of South‐African juvenile subjects.     

Increasing plant diversity of experimental grasslands alters the age and growth of Plantago lanceolata from younger and faster to older and slower

The persistence of plant populations depends on the ability of individuals to cope with the conditions provided by the community. So far, it is not known whether differences in the diversity and composition of plant communities affect the age structure of plant populations or the expression of stem anatomical traits reflecting investment into plant growth and storage. We analyzed annual growth rings in the secondary xylem and measured stem anatomical traits in individuals from 18 populations of Plantago lanceolata growing in a 12‐year old grassland biodiversity experiment (Jena Experiment). Plant individuals of P. lanceolata were on average older and reproduced later with increasing species richness. Individuals of P. lanceolata were slightly younger and the age distribution within populations skewed to younger individuals in the presence of grasses. The presence of legumes did not affect mean age, but led to a more even age distribution within populations. The width of growth‐related tissues (xylem, phloem, phellem) decreased with increasing species richness. Plant diversity‐effects on storage‐related tissues (pith, cortex) were less consistent, as pith showed increasing width with species richness, while cortex did not change with plant diversity. Our results imply that plant diversity effects on population age structure and the expression of stem anatomical traits of P. lanceolata reflect a tradeoff: growth and turnover is fast at low diversity (younger age, higher allocation to growth‐related tissue, faster generative reproduction), while it is slow at high diversity (older age, higher allocation to storage‐related tissue, later generative reproduction).     

Balancing bias and precision in capture-recapture estimates of abundance

Capture‐recapture estimates of abundance using photographic identification data are sensitive to the quality of photographs used and distinctiveness of individuals in the population. Here analyses are presented for examining the effects of photographic quality and individual animal distinctiveness scores and for objectively selecting a subset of data to use for capture‐recapture analyses using humpback whale (Megaptera novaeangliae) data from a 2‐year study in the North Atlantic. Photographs were evaluated for their level of quality and whales for their level of individual distinctiveness. Photographic quality scores had a 0.21 probability of changing by a single‐quality level, and there were no changes by two or more levels. Individual distinctiveness scores were not independent of photographic quality scores. Estimates of abundance decreased as poor‐quality photographs were removed. An appropriate balance between precision and bias in abundance estimates was achieved by removing the lowest‐quality photographs and those of incompletely photographed flukes given our assumptions about the true population abundance. A simulation of the selection process implied that, if the estimates are negatively biased by heterogeneity, the increase in bias produced by decreasing the sample size is not more than 2%. Capture frequencies were independent of individual distinctiveness scores.     

Variation in Growth and Potentially Associated Health Status in Hermann's and Spur‐Thighed Tortoise (Testudo hermanni and Testudo graeca)

Captive reptiles often show higher growth rates than in the wild, possibly due to higher feeding intensity. Although health problems are usually linked to inappropriate diets, fast growth itself, such as triggered by appropriate diets fed in high amounts, has traditionally also been considered unfavorable for tortoises. We document growth rates (based on age and mass) from private Testudo hermanni and T. graeca breeders, which are generally higher than those reported for free‐ranging specimens, but show enormous variation. Tortoise patients presented to an exotics clinic also covered the whole growth rate spectrum. To test whether fast growth was associated with diseases, the age–body mass relationship of these patients was tested, in a retrospective evaluation, for additional influence factors, such as dietary history and occurrence of certain diet and growth‐related diseases. No indication was found that animals particularly heavy for their age were more prone to diet/growth‐related disorders. In general, tortoises fed diets with meat/grain were heavier for their age than tortoises fed more appropriate diets; dietary history was not related to a particular disease. The results suggest the age–body mass relationship may not be suitable for testing effects of fast growth; an age–body length relationship would be more appropriate. Animals presented for a diet/growth‐related disorder were younger than animals presented for other reasons; there was a significant negative correlation between the severity of pyramiding and age, suggesting that growth‐related disorders may well limit the life expectancy of tortoises. Controlled clinical studies are required to fully test this hypothesis. Zoo Biol. 31:705‐717, 2012. © 2012 Wiley Periodicals, Inc.     

Aging,Maturation and Growth of Sauropodomorph Dinosaurs as Deduced from Growth Curves Using Long Bone Histological Data: An Assessment of Methodological Constraints and Solutions

Information on aging, maturation, and growth is important for understanding life histories of organisms. In extinct dinosaurs, such information can be derived from the histological growth record preserved in the mid-shaft cortex of long bones. Here, we construct growth models to estimate ages at death, ages at sexual maturity, ages at which individuals were fully-grown, and maximum growth rates from the growth record preserved in long bones of six sauropod dinosaur individuals (one indeterminate mamenchisaurid, two Apatosaurus sp., two indeterminate diplodocids, and one Camarasaurus sp.) and one basal sauropodomorph dinosaur individual (Plateosaurus engelhardti). Using these estimates, we establish allometries between body mass and each of these traits and compare these to extant taxa. Growth models considered for each dinosaur individual were the von Bertalanffy model, the Gompertz model, and the logistic model (LGM), all of which have inherently fixed inflection points, and the Chapman-Richards model in which the point is not fixed. We use the arithmetic mean of the age at the inflection point and of the age at which 90% of asymptotic mass is reached to assess respectively the age at sexual maturity or the age at onset of reproduction, because unambiguous indicators of maturity in Sauropodomorpha are lacking. According to an AIC-based model selection process, the LGM was the best model for our sauropodomorph sample. Allometries established are consistent with literature data on other Sauropodomorpha. All Sauropodomorpha reached full size within a time span similar to scaled-up modern mammalian megaherbivores and had similar maximum growth rates to scaled-up modern megaherbivores and ratites, but growth rates of Sauropodomorpha were lower than of an average mammal. Sauropodomorph ages at death probably were lower than that of average scaled-up ratites and megaherbivores. Sauropodomorpha were older at maturation than scaled-up ratites and average mammals, but younger than scaled-up megaherbivores.     

DEMOGRAPHIC ASPECTS OF COEXISTENCE IN ENGELMANN SPRUCE AND SUBALPINE FIR

The mechanisms for the maintenance of coexistence of Engelmann spruce and subalpine fir in subalpine forests of the Colorado Front Range were examined by comparing age, size, and spatial distributions of spruce and fir in two adjacent, previously logged sites of differing moisture availability. Adult tree ages were calculated from stem cores, while seedling ages were calculated from a multiple regression equation based on diameter, height, and number of branch whorls. Tree size was measured by height and diameter; spatial distributions were described by Morisita's index of dispersion. Cumulative age and size distributions were significantly different in the two species, with greater longevity and a larger overall size in spruce than fir. Both species showed a significant linear relationship between size and age, while fir showed a faster height growth rate than spruce. The linear relationship beween age and size was much closer in seedlings than in adults. Seedling spatial distribution was highly clumped in both species, but mature trees showed little or no clumping. Because both species are mainly wind dispersed, the greater clumping in spruce than in fir seedlings suggests that spruce have more specific establishment requirements than fir. Colonization patterns indicated that spruce seedlings were primarily found in forest gaps or associated with fir canopy trees, while fir seedlings were more commonly found in the forest, associated with either spruce or fir canopy trees. Tree density, growth rates, and mortality rates were higher in the wet site, with spruce showing the largest between site differences. These data suggest a new hypothesis for coexistence stating that Engelmann spruce and subalpine fir are maintained as codominants because the greater longevity and size of spruce is balanced by the faster height growth and more flexible seedling establishment requirements of fir.     

POPULATION ANALYSES OF INDO-PACIFIC HUMPBACK DOLPHINS SOUSA CHINENSIS IN ALGOA BAY,EASTERN CAPE,SOUTH AFRICA1

Mark-recapture analyses were performed on photo-identification data for Indo-Pacific humpback dolphins (Sousa chinensis) inhabiting Algoa Bay, on the Eastern Cape coast of South Africa. Boat-based photo-ID surveys were undertaken between May 1991 and May 1994. The rate of discovery of newly identified dolphins, distribution of sightings and frequency of resightings of known individuals indicate a high level of seasonal immigration of humpback dolphins into, and emigration from, the Algoa Bay region in summer. Consequently, humpback dolphins from Algoa Bay appear to be part of a substantially larger population that uses a considerable length of the coastal zone. The minimum population size is estimated to be about 466 dolphins.     

Relationships of reproductive traits and body size with attainment of sexual maturity and age in Blanding's turtles (Emydoidea blandingi)

To place associations among body size, age at maturity, age, and reproductive traits of a long-lived organism in the context of current life history models based on the concept of norms of reaction, we examined data from a mark-recapture study of Blanding's turtles (Emydoidea blandingi) in southeastern Michigan during 24 of the years between 1953 and 1988. Females matured between 14 and 20 years of age. Both the smallest and largest adult females in the population were reproducing for the first time in their lives. This result suggests that a combination of differences in juvenile growth rates and ages at maturity, and not indeterminate growth, are the primary cause of variation in body size among adults. Body size variation among individuals was not related to age at sexual maturity. Females that had slower growth rates as juveniles matured later at similar mean body size compared to those with more rapid growth that matured at an earlier age. As a result, a linear model of age at sexual maturity with growth rates of primiparous females between hatching and maturity was significant and negative (R² = 0.76). Frequency of reproduction of the largest and smallest females was not significantly different. Clutch size did not vary significantly with age among either primiparous or multiparous females. Clutch sizes of primiparous females and multiparous females were not significantly different. However, older females (>55 years minimum age) reproduced more frequently than did younger females (minimum age <36 y).     

DENTITION AND AGEING OF THE HIPPOPOTAMUS

I. Summary The present paper is based on the examination of lower jaws from some 3000 individuals of Hippopotamus amphibius L. which were collected in the course of cropping operations in the Queen Elizabeth Park, Uganda between 1961 and 1966. It extends an earlier study by W. M. Longhurst, who described 20 relative age groups based on tooth replacement and wear. The age groups, slightly modified, are described and illustrated here and should serve as a useful field guide. Mean chronological ages from 0–43 years have been allocated to the groups. Checks which confirm the validity of the ages allotted are presented and discussed. These include correlation with the mandibular age group of six known-age animals; findings on the age-related incidence of rinderpest-neutralising antibodies; the orderly progress of fusion of the mandibular symphysis and rate of loss of the first premolar. Growth layers present in the teeth are discussed. The growth of the eye lens is also described. After an initial phase of rapid growth the lens continues to grow throughout life and follows a rectilinear pattern from an estimated age of eight years onwards. This is expected from the findings of similar studies on other species for which known-age specimens are available. Variability of lens dry weight at age is relatively small and indicates that the estimated ages are reasonably precise. Growth of the mandible is analysed and is not inconsistent with the ages allotted. A marked sex difference in mandible weight at age allows the sex of found jaws to be determined at ages above eight years. The growth of the teeth is described. Both canines and incisors show well-marked sex differences in growth rate and size. The post-canine teeth do not show sex differences. Cycles of growth, wear and resorption of these teeth are discussed and it is concluded that mechanical senescence of the teeth is a major factor in mortality at ages above 30 years. Growth in body length is briefly discussed and provides further confirmation of the validity and precision of the age criteria. Growth equations are presented. Finally a survivorship curve derived from the ageing of 207 jaws assumed to represent natural deaths is presented. Population models are constructed from the survivorship curves by calculation of estimated natality rates (obtained by applying data on age at first breeding and annual pregnancy rate to the survivorship data) and life tables are constructed. The shape of the survivorship curve and the percentage recruitment agree with expectation and provide further evidence of the consistency of the age criteria.     

AN OCEAN-BASIN-WIDE MARK-RECAPTURE STUDY OF THE NORTH ATLANTIC HUMPBACK WHALE (MEGAPTERA NOVAEANGLIAE)

Although much is known about the humpback whale, Megaptera novaeangliae, regional studies have been unable to answer several questions that are central to the conservation and management of this endangered species. To resolve uncertainties about population size, as well as the spatial and genetic structure of the humpback whale population in the North Atlantic, we conducted a two-year ocean-basin-wide photographic and biopsy study in 1992-1993. Photographic and skin-biopsy sampling was conducted of animals in feeding and breeding areas throughout most of the range of this species in the North Atlantic, from the West Indies breeding grounds through all known feeding areas as far north as arctic Norway. A standardized sampling protocol was designed to maximize sample sizes while attempting to ensure equal probability of sampling, so that estimates of abundance would be as accurate and as precise as possible. During 666 d at sea aboard 28 vessels, 4,207 tail fluke photographs and 2,326 skin biopsies were collected. Molecular analyses of all biopsies included determination of sex, genotype using six microsatellite loci, and mitochondrial control region sequence. The photographs and microsatellite loci were used to identify 2,998 and 2,015 individual whales, respectively. Previously published results from this study have addressed spatial distribution, migration, and genetic relationships. Here, we present new estimates of total abundance in this ocean using photographic data, as well as overall and sex-specific estimates using biopsy data. We identify several potential sampling biases using only breeding-area samples and report a consistent mark-recapture estimate of oceanwide abundance derived from photographic identification, using both breeding and feeding-area data, of 10,600 (95% confidence interval 9,300-12,100). We also report a comparable, but less precise, biopsy-based estimate of 10,400 (95% confidence interval of 8,000-13,600). These estimates are significantly larger and more precise than estimates made for the 1980s, potentially reflecting population growth. In contrast, significantly lower and less consistent estimates were obtained using between-feeding-area or between-breeding-area sampling. Reasons for the lower estimates using the results of sampling in the same areas in subsequent years are discussed. Overall, the results of this ocean-basin-wide study demonstrate that an oceanwide approach to population assessment of baleen whales is practicable and results in a more comprehensive understanding of population abundance and biology than can be gained from smaller-scale efforts.     

Age determination by back length for African savanna elephants: extending age assessment techniques for aerial-based surveys

Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.