Incidence of caries and abscesses in archeological Eskimo skeletal samples from point hope and Kodiak Island,Alaska

The incidence of caries and abscesses in 246 archeologically derived skeletal specimens from the Ipiutak and Tigara levels at Point Hope, Alaska, and 79 specimens excavated from Jones Point, Kodiak Island, Alaska were investigated. All three collections span long periods of time. Only pre-white contact specimens were used. Each specimens was sexed and aged in five year groupings, using standard techniques. Caries and abscesses were recorded by type and degree of severity and correlated with age, sex, and site of origin. All samples displayed very low caries rates and few abscesses per tooth and per individual (both observed frequencies, and frequencies corrected for postmortem loss of teeth). DMF scores were tabulated using both observed and corrected frequencies. Very heavy occlusal wear in all three samples could account for the majority of abscesses and pulp exposures, while the low caries rates are attributable to traditional diets totally devoid of refined sugars, starches, and food additives.     

Oral and physiological paleohealth in cold adapted peoples: Northeast Asia, Hokkaido

This paper examines variables useful in reconstructing oral (caries, antemortem tooth loss, alveolar defects) and physiological (cribra orbitalia, linear enamel hypoplasia) well-being in two bioarchaeological assemblages from Hokkaido, Japan: Okhotsk (n = 37 individuals) and Jomon (n = 60). Findings are compared and contrasted with each other, with published series from Honshu Japan, and samples from climatically near-equivalent Alaska. It was found that more meaningful comparisons of Hokkaido paleohealth could be made with Alaskan material, rather than the more southerly Jomon. Results were ambiguous with respect to physiological well-being. Low levels of LEH in the cold-adapted samples suggest operating in arctic and subarctic environments with marine-based subsistence regimes is not physiologically expensive. However, the relatively high levels of cribra orbitalia in Hokkaido, relative to Alaska, suggest the picture is not straightforward: the reasons for elevated cribra orbitalia in Hokkaido are unclear. The subarctic and arctic samples formed three broadly similar groupings in terms of oral health profiles: (1) Aleuts and Eskimo; (2) Ipiutak and Tigara; (3) Hokkaido Jomon, Okhotsk, and Kodiak Island. Differences between these groupings could be explained with a combination of sample demographics and subsistence orientations. The extremely high frequency of caries in one sample, caribou hunting Ipiutak, may have been influenced by factors such as low levels of dietary magnesium and potentially cariogenic foodstuffs, such as preparations of caribou stomach contents. It was concluded that oral health profiles are potentially sensitive to differences in subsistence strategies among cold-adapted hunter-gatherers, although they lack predictive value.     

Health status among prehistoric Eskimos from Point Hope,Alaska

Using the protocol outlined in The Backbone of History: Health and Nutrition in the Western Hemisphere (BBH) (Steckel and Rose. 2002a. The backbone of history: health and nutrition in the Western Hemisphere. Cambridge: Cambridge University Press), this project compares the Mark I Health Index (MIHI) scores of the Ipiutak (n = 76; 100BCE–500CE) and Tigara (n = 298; 1200–1700CE), two samples of North American Arctic Eskimos excavated from Point Hope, Alaska. Macroscopic examination of skeletal remains for evidence of anemia, linear enamel hypoplasias (LEH), infection, trauma, dental health, and degenerative joint disease (DJD) was conducted to assess differences in health status resulting from a major economic shift at Point Hope. These data demonstrate that despite differences in settlement pattern, economic system, and dietary composition, the MIHI scores for the Ipiutak (82.1) and Tigara (84.6) are essentially equal. However, their component scores differ considerably. The Ipiutak component scores are suggestive of increased prevalence of chronic metabolic and biomechanical stresses, represented by high prevalence of nonspecific infection and high frequencies of DJD in the hip/knee, thoracic vertebrae, and wrists. The Tigara experienced more acute stress, evidenced by higher prevalence of LEH and trauma. Comparison of overall health index scores with those published in BBH shows the MIHI score for the Ipiutak and Tigara falling just above the average for sites in the Western Hemisphere, adding support to the argument that the human capacity for cultural amelioration of environmental hardships is quite significant. Am J Phys Anthropol, 2011. © 2011 Wiley‐Liss, Inc.     

Periodontal disease in the prehistoric Ipiutak and Tigara skeletal remains from Point Hope,Alaska

Two large groups of prehistoric Eskimo skeletons from Point Hope, Alaska, were evaluated for dental wear and several measures of periodontal disease. Occlusal attrition was found to increase steadily with increasing age. Crown height decreased proportionately. Assessing periodontal disease by inspecting apparent alveolar recession was judged ineffective due to possible supereruption. Infrabony pockets, the result of severe localized periodontal disease indicated that in Ipiutak people between the ages of 25 and 30, and Tigara people between 35 and 40, more dental sites were affected by periodontal disease than were not. This suggests a cultural, genetic, or dietary difference between the two groups. Male/female differences were slight in all parameters studied.     

Tooth wear and dental pathology of the Bronze-Iron Age people in Xinjiang, Northwest China: Implications for their diet and lifestyle

Tooth wear and dental pathology related to diet and lifestyle were investigated in the human dental remains unearthed from three archaeological sites of Bronze Age and Iron Age in Xinjiang of northwest China, and in comparative samples from two Neolithic sites in Henan and Shanxi in central China along the Yellow River.Our results indicate that the average tooth wear on most tooth types in the three Xinjiang sites was close to those of the Neolithic samples from central China. The variation within the Xinjiang samples was also explored. Some special wear patterns such as severe wear on the first molar and relatively heavy wear of anterior teeth were observed on the specimens from the Xinjiang sites. Obvious differences in caries and antemortem tooth loss were found between Xinjiang and comparative samples with higher frequencies of caries observed in samples from central China and higher antemortem tooth loss in samples from the Xinjiang sites. Strongly developed exostoses (tori) were also identified on mandibles and maxillae of the specimens from Xinjiang.The authors believe that the differences in tooth wear and dental pathology between Xinjiang and central China were caused by differences in diet and lifestyle. Food of a harder texture was consumed by the people who lived in Xinjiang than by the people in Henan and Shanxi of central China. The higher occurrence of heavily worn anterior teeth and some other special wear patterns, antemortem tooth loss and presence of exostoses on jaw bones in Xinjiang suggest that the people in Xinjiang lived in a relatively harsh environment, frequently gnawing hard objects, or using teeth as some kind of tools. All these activities put masticatory organs under a heavy load. The differences in caries frequencies between the frontier and central areas of China indicate that food richer in carbohydrates was consumed by the people in the central areas.It is proposed that about 3000-2000 years BP in many areas of frontier Xinjiang, people mainly relied on the type of hunter-gatherer economy with agriculture playing a smaller role in their lifestyle.     

Body proportions of circumpolar peoples as evidenced from skeletal data: Ipiutak and Tigara (Point Hope) versus Kodiak Island Inuit

Given the well‐documented fact that human body proportions covary with climate (presumably due to the action of selection), one would expect that the Ipiutak and Tigara Inuit samples from Point Hope, Alaska, would be characterized by an extremely cold‐adapted body shape. Comparison of the Point Hope Inuit samples to a large (n > 900) sample of European and European‐derived, African and African‐derived, and Native American skeletons (including Koniag Inuit from Kodiak Island, Alaska) confirms that the Point Hope Inuit evince a cold‐adapted body form, but analyses also reveal some unexpected results. For example, one might suspect that the Point Hope samples would show a more cold‐adapted body form than the Koniag, given their more extreme environment, but this is not the case. Additionally, univariate analyses seldom show the Inuit samples to be more cold‐adapted in body shape than Europeans, and multivariate cluster analyses that include a myriad of body shape variables such as femoral head diameter, bi‐iliac breadth, and limb segment lengths fail to effectively separate the Inuit samples from Europeans. In fact, in terms of body shape, the European and the Inuit samples tend to be cold‐adapted and tend to be separated in multivariate space from the more tropically adapted Africans, especially those groups from south of the Sahara. Am J Phys Anthropol, 2010. © 2009 Wiley‐Liss, Inc.     

Dental chipping in Aleuts, Eskimos and Indians

Analysis of dentitions belonging to 324 prehistoric and protohistoric Aleuts, Eskimos and northern Indians, all of whom were regularly meat-eaters, reveals a significant difference between Eskimos and Aleut-Indians for a little known type of tooth wear. This wear is characterized by severe crushing and/or flaking of the crown surface of one or more teeth (termed “pressure-chipping”). It occurs chiefly in dentitions of high arctic Eskimos of Alaska, Canada, and Greenland, and significantly less often in the teeth of Kodiak Island Eskimos, Aleuts and northern Indians. Sex differences do not exist but pressure-chipping occurs significantly more often in adult (21–x years) than in non-adult (0–20 years) Eskimos. The exact mechanism(s) responsible for pressure-chipping is unknown, although ethnographic accounts of Eskimo eating habits suggest that crushing of hard substances such as bone was involved. The severity of this wear could have contributed to the selection for, or preservation of, large and complex crowns in high arctic Eskimos. Pressure-chipping is offered as evidence favoring the view that tooth size (longevity) may have had in the past some adaptive value.     

Vertebral arch defects in the lumbar vertebrae of pre-historic American Eskimos. A study of skeletons in the American Museum of Natural History,chieely from Point Hope,Alaska

The incidence of lumbar vertebral arch defects was studied in 295 Eskimo skeletons now in the American Museum of Natural History, New York, which were obtained from adjacent burial grounds at Point Hope, Alaska. One burial ground containing 47 skeletons was used by the Ipiutak at about the start of the Christian era. The other burial ground was used by the Tigara a thousand years later and contained 248 skeletons. The lesion is a separation of the vertebral arch from the vertebral body. It usually involves the fifth lumbar vertebra but may involve others and more than one. The present incidence in the United States is about 7%. Among the Tigara the incidence was 45% and more than twice that of the Ipiutak, 21%. The youngest case was in a child of five and the deformity was uncommon before adult life. The incidence and extent of the lesion increased with age suggesting an hereditary weakness as an etiological factor. No other etiological factor could be determined although several were considered. The clinical disability could not be determined but it seemed to have no effect on longevity.     

Oral health of the Paleoamericans of Lagoa Santa,central Brazil

The peopling, origins, and early prehistory of the Americas are topics of intense debate. However, few studies have used human remains to document and interpret patterns of health and lifestyle of Paleoamericans. This study provides the first investigation to characterize oral health in a series of early Holocene skeletal remains from Lagoa Santa, Brazil, a locality containing the remains of some of the earliest inhabitants of South America (10,000–7,000 BP). The sample is composed of 949 teeth and 1925 alveoli from an estimated 113 individuals excavated from 17 archaeological sites located in the State of Minas Gerais. We compare dental caries and abscess prevalence at Lagoa Santa to a large sample of human skeletons from the Western Hemisphere Project (WHP) database using both individual and tooth/alveolus count methods. In addition, antemortem tooth loss and tooth wear were analyzed in Lagoa Santa by sex and age. The results show that Lagoa Santa dental caries and abscess prevalence are significantly higher than observed among other hunter–gatherers included in the WHP database, except when abscess prevalence is considered by individual count. Adult females have less tooth wear coupled with higher prevalence of dental caries and antemortem tooth loss than adult males. These results point to an unexpected record of poor oral health at Lagoa Santa, especially among females. A diet based on a highly cariogenic combination of wild tubers and fruits is suggested as an explanation for the elevated rate, characterizing an early adaptation to a tropical environment in South America. Am J Phys Anthropol 154:11–26, 2014. © 2014 Wiley Periodicals, Inc.     

Variation in dental wear and tooth loss among known‐aged,older ring‐tailed lemurs (Lemur catta): a comparison between wild and captive individuals

Tooth wear is generally an age‐related phenomenon, often assumed to occur at similar rates within populations of primates and other mammals, and has been suggested as a correlate of reduced offspring survival among wild lemurs. Few long‐term wild studies have combined detailed study of primate behavior and ecology with dental analyses. Here, we present data on dental wear and tooth loss in older (>10 years old) wild and captive ring‐tailed lemurs (Lemur catta). Among older ring‐tailed lemurs at the Beza Mahafaly Special Reserve (BMSR), Madagascar (n=6), the percentage of severe dental wear and tooth loss ranges from 6 to 50%. Among these six individuals, the oldest (19 years old) exhibits the second lowest frequency of tooth loss (14%). The majority of captive lemurs at the Indianapolis Zoo (n=7) are older than the oldest BMSR lemur, yet display significantly less overall tooth wear for 19 of 36 tooth positions, with only two individuals exhibiting antemortem tooth loss. Among the captive lemurs, only one lemur (a nearly 29 year old male) has lost more than one tooth. This individual is only missing anterior teeth, in contrast to lemurs at BMSR, where the majority of lost teeth are postcanine teeth associated with processing specific fallback foods. Postcanine teeth also show significantly more overall wear at BMSR than in the captive sample. At BMSR, degree of severe wear and tooth loss varies in same aged, older individuals, likely reflecting differences in microhabitat, and thus the availability and use of different foods. This pattern becomes apparent before “old age,” as seen in individuals as young as 7 years. Among the four “older” female lemurs at BMSR, severe wear and/or tooth loss do not predict offspring survival. Am. J. Primatol. 72:1026–1037, 2010. © 2010 Wiley‐Liss, Inc.     

Human tooth wear, tooth function and cultural variability

Among primitive peoples dental attrition appears to be a natural phenomenon. Often the degrees and kinds of tooth wear vary from population to population. This variability is possibly related to certain material aspects of culture such as diet, food preparation techniques and tool usage. In order to learn more about these relationships, extensive cross cultural comparisons must be made. This paper reports on a study of dental attrition among skeletal remains of North American Indians from three areas: California, the Southwest and the Valley of Mexico. A method of comparing worn teeth of these populations was devised so several characteristics of the teeth and supporting bone could be examined by population. This study showed significant differences in type and degree of wear among the three groups as well as differences between sexes within each population. A positive correlation between tooth wear and cultural factors was found. Dietary specialization and division of labor appear to be responsible for the degree and type of wear found in this sample. Further studies of this type are planned to expand the sample size and, if the new data support these correlations, valuable information about human–environmental relationships can be gained.     

New facial measurement used in the determination of palatine index and thickness of the mandibular body index

Measurements of the height of the mandibular body and the length of the palate rest on the assumption that the alveolar parts of the mandible and maxilla are not altered. Unfortunately, in the skeletal remains of the past population most of the molar teeth are often antemortem lost and this tooth loss is followed by resorption of the alveolar ridge. A new method of taking mandibular and palate measurements, which could be used in these cases is proposed in the study.     

Resorption of mandibular alveolar bone following loss of molar teeth and its relationship to age at death in a human skeletal population

Estimating adult age at death in skeletal remains is problematic, particularly in older adults. Molar wear is arguably the most reliable ageing technique for palaeopopulations, but many older adult skeletons have lost their molar teeth ante mortem, precluding its application. Resorption of the alveolar process occurs following tooth loss, and this appears to continue for a prolonged period. The current work investigates the relationship of this process to individual age in a nineteenth century AD European archaeological skeletal series of known age at death (N = 92 individuals), and discusses its potential as an age indicator. Mandibular corpus height was measured at the different molar positions. In females, reduction of corpus height with age was found at molar positions showing ante mortem loss. In both sexes, a relationship was found between age and a simple composite measure of corpus height in the molar region in those showing ante mortem loss of one or more mandibular molars. The correlation was stronger in females (r = ?0.74) than in males (r = ?0.49), appeared approximately linear, and continued into the ninth decade, the oldest age group in the study material. The results suggest that investigation of height of the posterior part of the mandibular corpus as a skeletal age indicator for individuals that have lost one or more molar teeth is merited in other palaeopopulations. Am J Phys Anthropol 153:643–652, 2014. © 2014 Wiley Periodicals, Inc.     

Cultural remains in local and regional context on the central Alaska Peninsula: housepits, language, and cultural affinities at Marraatuq after 1000 B.P

Professor Dumond's research on the Alaska Peninsula provided information that prior to 1,000 years ago people of both sides of the Alaska Peninsula shared material culture and exhibited subsistence interests that persisted into historic times, During the Late Precontact Era (ca. 1100 A.D. to mid-1700s) these Alutiiq societies shared cultural traits including language, house styles, and material culture with their relatives and neighbors on Kodiak Island. Until recently, few data were available regarding potential variability in house construction techniques, or styles and functions of Alutiiq semi-subterranean houses of this era found on the Alaska Peninsula, This paper provides examples of a few known prehistoric and historic Alaska Peninsula and Kodiak Alutiiq houses and presents previously unreported data from archaeological tests at Marraatuq on the Central Alaska Peninsula, Taken together with Dumond's 1998-1999 field work at Leader Creek and archaeological research on Kodiak Island, the work provides further evidence that interregional interaction was strong during the Late Precontact Era. However, large population centers and ranked political hierarchies probably were not hallmarks of central Alaska Peninsula communities during the Late Precontact Era and historic times as they were on the Kodiak and Aleutian islands.     

A comparison of antemortem tooth loss in human hunter‐gatherers and non‐human catarrhines: Implications for the identification of behavioral evolution in the human fossil record

Middle and Late Pleistocene fossil hominin specimens with severe antemortem tooth loss are often regarded as evidence for the precocious evolution of human‐like behaviors, such as conspecific care or cooking, in ancient hominin species. The goal of this project was to ask whether the theoretical association between antemortem tooth loss and uniquely human behaviors is supported empirically in a large skeletal sample of human hunter‐gatherers, chimpanzees, orangutans, and baboons. Binomial regression modeling in a Bayesian framework allows for the investigation of the effects of tooth class, genus, age, and sex on the likelihood of tooth loss. The results strongly suggest that modern humans experience more antemortem tooth loss than non‐human primates and identify age in years as an important predictor. Once age is accounted for, the difference between the humans and the closest non‐human genus (chimpanzees) is less pronounced; humans are still more likely on average to experience antemortem tooth loss though 95% uncertainty envelopes around the average prediction for each genus show some overlap. These analyses support theoretical links between antemortem tooth loss and modern human characteristics; humans' significantly longer life history and a positive correlation between age and antemortem tooth loss explain, in part, the reason why humans are more likely to experience tooth loss than non‐human primates, but the results do not exclude behavioral differences as a contributing factor. Am J Phys Anthropol 151:252–264, 2013. © 2013 Wiley Periodicals, Inc.     

Tooth loss, denture wearing and associated factors among an elderly institutionalised Brazilian population

Objective: This cross‐sectional study assessed the prevalence and extent of tooth loss as well as denture wear and associated factors in institutionalised elderly in Brazil. Background: There is scarcity of research in Brazil concerning geriatric oral health issues. Material and methods: A sample of 335 individuals over 60 years of age, representative of the institutionalised elderly from Belo Horizonte, Brazil, were selected through a stratified sampling strategy. Data were collected from structured questionnaires, reviews of medical records and intra‐oral examinations. Results: Edentulousness was observed in 74.9% of the elderly and was related to age, years of study, income, length of institutionalisation, systemic diseases and mini‐mental score. Among the dentate subjects, 17.9% possessed 20 or more teeth. Approximately half the edentulous elderly (42.6%) and most of the partially dentate subjects (66.7%) did not wear dentures. The multivariate analysis showed that subjects that wear dentures were more likely to be female, possess higher incomes, be more functionally independent and married. Furthermore, the odds of wearing dentures among the elderly who had lost 13–32 teeth were 9.11 times higher than those who had lost up to 12 teeth. Conclusion: Tooth loss is highly prevalent in this institutionalised Brazilian population, and the prevalence of denture wear is low. The extent of tooth loss, income, functional status and marital status are important predictors for denture wear. The development of an oral health programme for these individuals should assist in their rehabilitation needs and promote in‐home care or safe transport for the elderly to a health care location.     

湖北郧县青龙泉新石器时代居民牙齿磨耗及健康状况

位于湖北省郧县境内的青龙泉遗址出土有仰韶、屈家岭和石家河等不同文化类型遗存, 被认为是中国新石器时代南、北文化交流的过渡地带。有关学者通过考古发现和同位素测试分析认为, 生活在青龙泉遗址的新石器时代居民已经具有发达的农业、家畜饲养业和渔猎,稻粟农业和肉类对居民的食物构成都有贡献, 但并不确定农业或渔猎是否占主导地位。本文通过对87例个体1075枚青龙泉新石器时代居民牙齿的磨耗、龋齿病、牙齿生前脱落、颌骨粗壮程度的观察、分析和对比, 试图从另一个侧面提供当时居民食物构成和经济模式的信息。本研究发现, 相比于其他中国新石器时代人类, 青龙泉居民的牙齿磨耗程度总体偏轻、臼齿磨耗角度多呈倾斜状、龋齿病出现率高、与生活状态相关的牙齿生前脱落出现率低、颌骨粗壮程度不明显。这些发现提示居民的食物较精细,加工程度高, 富含碳水化合物。基于本文发现, 作者认为农业经济在距今5000年左右的长江中游地区已经比较发达, 在居民食物构成中居主导地位,居民可能已经具有较高的食物制作加工技术。     

Genetic structuring among Alaskan Pacific herring populations identified using microsatellite variation

Five highly variable microsatellite loci were used to investigate population structuring in Pacific herring Clupea pallasi collected from Kodiak Island, two sites in the Bering Sea and four sites within Prince William Sound, Alaska. All loci revealed high levels of variability with heterozygosity estimates ranging from 86 to 97% (mean heterozygosity: 89%). The variation was structured significantly among sites suggesting that the samples investigated were genetically distinct from each other. Genetic divergence was greatest between populations from the Bering Sea and those from Prince William Sound. The Kodiak Island and Point Chalmers samples appeared to be distinct from the Prince William Sound and Bering Sea populations. The observed genetic distance relationships among samples could be explained largely in terms of geographical separation.     

Tooth wear and compensatory modification of the anterior dentoalveolar complex in humans

In populations living in environments where teeth wear severely, some compensatory modification of the dentoalveolar complex is thought to occur during life whereby functional occlusion is maintained as tooth substance is lost by wear. This study investigates one aspect of this modification process: Changes in the anterior dentoalveolar complex that are accompanied with wear were examined in a series of Japanese skeletal samples. In the prehistoric Japanese hunter-gatherer population heavy wear occurs over the entire dentition. The following changes were demonstrated to have occurred in the anterior segment of the dentition accompanied by wear on the anterior teeth: The anterior teeth tip lingually with wear up to a nearly upright position to fill in interproximal spaces that would have been generated by wear, and to maintain contact relations between adjacent teeth. At the same time, the anterior surface of the maxillary alveolar process also inclines lingually to a certain extent. The amount of lingual tipping is greater in the maxillary anterior teeth than in their mandibular antagonists. It is because of this discrepancy that, with age, the horizontal component of the overlap between maxillary and mandibular anterior teeth decreases, and their bite form changes from scissor bite to edge-to-edge bite. Lesser degrees of lingual tipping of the anterior teeth were also detected in the prehistoric agriculturists and historic Japanese populations. The variation in the degree of lingual tipping observed among the samples is explained by inter-population variation in severity and pattern of tooth wear. This and other evidence suggests that mechanisms that compensate for wear in the anterior dentition may be characteristic of all living human populations, independently of the degree of wear severity endured in their environments.     

Assessment of clinical pathology and pathogen exposure in sea otters (Enhydra lutris) bordering the threatened population in Alaska

Northern sea otter (Enhydra lutris kenyoni) abundance has decreased dramatically over portions of southwest Alaska, USA, since the mid-1980s, and this stock is currently listed as threatened under the Endangered Species Act. In contrast, adjacent populations in south central Alaska, USA, and Russia have been stable to increasing during the same period. Sea otters bordering the area classified in the recent decline were live-captured during 2004-2006 at Bering Island, Russia, and the Kodiak Archipelago, Alaska, USA, to evaluate differences in general health and current exposure status to marine and terrestrial pathogens. Although body condition was lower in animals captured at Bering Island, Russia, than it was at Kodiak, USA, clinical pathology values did not reveal differences in general health between the two regions. Low prevalences of antibodies (<5%) were found in Kodiak, USA, and on Bering Island, Russia, to Toxoplasma gondii, Sarcocystis neurona, and Leptospira interrogans. Exposure to phocine herpesvirus-1 was found in both Kodiak, USA (15.2%), and Bering Island, Russia (2.3%). Antibodies to Brucella spp. were found in 28% of the otters tested on Bering Island, Russia, compared with only 2.7% of the samples from Kodiak, USA. Prevalence of exposure to Phocine distemper virus (PDV) was 41% in Kodiak, USA, but 0% on Bering Island, Russia. Archived sera from southwest and south-central Alaska dating back to 1989 were negative for PDV, indicating exposure occurred in sea otters in Kodiak, USA, in recent years. Because PDV can be highly pathogenic in na?ve and susceptible marine mammal populations, tissues should be examined to explore the contribution of this virus to otter deaths. Our results reveal an increase in exposure to pathogens in sea otters in Kodiak, Alaska, USA, since the 1990 s.