scholarly journals Age determination methods in harbour seals (Phoca vitulina) with a review of methods applicable to carnivores

2010 ◽  
Vol 8 ◽  
pp. 245 ◽  
Author(s):  
Christina Lockyer ◽  
Beth Mackey ◽  
Fiona Read ◽  
Tero Härkönen ◽  
Ilk Hasselmeier
Keyword(s):  
Best Practices ◽  
Marine Mammals ◽  
Tooth Extraction ◽  
Age Determination ◽  
Detailed Examination ◽  
Phoca Vitulina ◽  
Growth Layer ◽  
Harbour Seals ◽  
Determination Methods ◽  
Layer Groups

The development of age determination methods in marine mammals is reviewed with particular reference to the use of teeth Growth Layer Groups (GLGs) formed in the dentine and cement of carnivores. Using this background, practices for sampling, tooth extraction and collection, storage and different methods of preparation of teeth as well as reading and counting GLGs are discussed and evaluated for the harbour seal (Phoca vitulina). The paper includes comments on best practices for counting GLGs with new examples from known-age seals, and also a detailed examination of confounding factors in interpreting GLGs such as mineralization anomalies and the phenomena of accessory lines, “false annuli” and “paired laminae” which have not been discussed previously. The paper concludes with recommendations for undertaking age estimation in harbour seals from sampling through final GLG interpretation with special emphasis on standardization of methods with other researchers.

scholarly journals Treatment of naturally acquired demodectic mange with amitraz in two harbour seals (Phoca vitulina)

2015 ◽  
Vol 63 (3) ◽  
pp. 352-357 ◽  
Author(s):  
Kyoo-Tae Kim ◽  
Seung-Hun Lee ◽  
Dongmi Kwak
Keyword(s):  
Successful Treatment ◽  
Marine Mammals ◽  
Clinical Signs ◽  
Skin Lesions ◽  
Phoca Vitulina ◽  
Aetiological Agent ◽  
Harbour Seals ◽  
Causative Agents ◽  
Pure Cultures

Two male harbour seals (Phoca vitulina; 33 and 35 years old, respectively), housed since 2002 at a zoo for exhibition purposes, developed severe, multifocal and diffuse skin lesions. Skin scrapings and microscopy for parasites as well as pure cultures for bacteria and dermatophytes were carried out to identify the aetiological agent. Skin scrapings showed that lesions appearing on the seals were caused by an infestation of Demodex mites, which is uncommon in marine mammals, and were not due to other causative agents (parasites, bacteria or dermatophytes). Treatment with amitraz (0.01%) once a week for three weeks and with ampicillin (10 mg/kg SID per os) for six days eliminated the mites and resolved the clinical signs of demodectic mange in the harbour seals. The purpose of this report is to describe the successful treatment of naturally acquired demodectic mange with amitraz in harbour seals.

A comparison of age determination techniques for the harbour porpoise, Phocoena phocoena L.

1989 ◽  
Vol 67 (7) ◽  
pp. 1832-1836 ◽  
Author(s):  
Peter Watts ◽  
David E. Gaskin
Keyword(s):  
North Atlantic ◽  
Age Determination ◽  
Harbour Porpoise ◽  
Phocoena Phocoena ◽  
Growth Layer ◽  
Single Cross Section ◽  
Living Bone ◽  
Layer Groups ◽  
Annual Deposition ◽  
Age Estimates

The maximum life-span of the harbour porpoise has been estimated at 13 years (based upon dentinal growth layer groups in the teeth) and at 21 years (based upon growth layers in the periosteal bone of the mandible). We used both techniques to estimate the ages of 120 harbour porpoises from the western North Atlantic, in an attempt to determine the relative reliability of each technique. Dentinal layering was the better predictor of body length. Mandibular layering was highly variable even within a single cross section in most specimens, as a result of both common bifurcation of the layers and destruction of the inner layers by growth and remodelling of the living bone. Furthermore, mandibular layers appear to be deposited at a rate of 2 layers/year, double the deposition rate of dentinal growth layer groups. Age estimates which assume annual deposition of mandibular layers therefore overestimate true age.

Assessment of claw growth-layer groups from ringed seals (Pusa hispida) as biomonitors of inter- and intra-annual Hg, δ15N, and δ13C variation

2011 ◽  
Vol 89 (9) ◽  
pp. 774-784 ◽  
Author(s):  
Elizabeth O. Ferreira ◽  
Lisa L. Loseto ◽  
Steven H. Ferguson
Keyword(s):  
Life History ◽  
Marine Mammals ◽  
Ringed Seal ◽  
The Body ◽  
Conservation Strategies ◽  
Growth Layer ◽  
Annual Variations ◽  
Ringed Seals ◽  
Pusa Hispida ◽  
Layer Groups

The ringed seal ( Pusa hispida (Schreber, 1775)) is a sentinel species of arctic marine mammals; therefore, methods to monitor its life-history changes are crucial to establish effective conservation strategies. We evaluate the potential use of claws of ringed seals as a proxy for counts of tooth growth-layer groups (age) and a biomonitor of total mercury burden (THg) and diet (stable isotope ratios expressed as δ15N and δ13C). The count of claw growth-layer groups was indicative of age up to 8 years and we infer differentiation of dark and light annuli as being associated with the spring moult. No differences of THg, δ15N, or δ13C were observed among flipper digits. The proximal claw annulus representing the most recent growth had δ13C values that were correlated to both muscle and liver δ13C, supporting the use of claws to monitor visceral δ13C. Claw log10THg from the proximate annulus was significantly correlated to liver and whisker log10THg, while significant interannual THg accumulation was observed in 18 of 32 seals ≥4 years, suggesting the claws receive and disperse Hg from active tissues of the body. Results support the use of claw tissue from ringed seal to provide a chronological record of inter- and intra-annual variations representing seal diet, contaminant load, and life history.

Transit time of digesta in captive harbour seals (Phoca vitulina)

1993 ◽  
Vol 71 (5) ◽  
pp. 1071-1073 ◽  
Author(s):  
Nina Hedlund Markussen
Keyword(s):  
Transit Time ◽  
Marine Mammals ◽  
Barium Sulphate ◽  
Stomach Content Analysis ◽  
Phoca Vitulina ◽  
Caloric Content ◽  
X Rays ◽  
Qualitative And Quantitative ◽  
Harbour Seals ◽  
Time Required

Stomach-content analysis can be used to identify the species and size of prey fishes eaten by marine mammals, and has been used for both qualitative and quantitative estimates of their food requirements. Methods that use mass or volume to determine the amount of fish eaten depend on the degree of digestion and the time required for the stomach to empty. The transit time of digesta was estimated by recording the initial defecation time and the time required for the stomach to empty in four harbour seals (Phoca vitulina). The seals were given meals varying in size from 0.5 to 2.1 kg and in caloric content from 4940 to 12 770 kJ/kg, and containing carmine or barium sulphate as a marker. The time from eating until red faeces were observed was between 2 h 35 min and 6 h 15 min. Also, barium sulphate was injected into the food given, and X-rays were used to estimate the time required for the stomach to empty. The stomach started to empty less than 1 h after the meal. Some prey remained in the stomach 5 h after eating.

scholarly journals A review of age estimation methods in marine mammals with special reference to monodontids

2018 ◽  
Vol 10 ◽  
Author(s):  
Fiona L. Read ◽  
Aleta A. Hohn ◽  
Christina H. Lockyer
Keyword(s):  
Age Estimation ◽  
Marine Mammals ◽  
Estimation Methods ◽  
Growth Layer ◽  
Mineral Density ◽  
Relative Age ◽  
Accuracy And Precision ◽  
Absolute Age ◽  
Hard Structures ◽  
Layer Groups

This paper presents a critical review of methods for estimating absolute or relative age in marine mammals. Absolute age is achieved by counting growth layer groups (GLGs) in hard structures such as teeth, ear plugs, baleen, bones and claws. Relative age can be obtained by methods such as aspartic acid racemisation, genetic telomeres, bone mineral density, fatty acid signatures and other methods. Each method is discussed in detail. Accuracy and precision, including inter-reader calibration and anomalies, as well as methods of validating GLG deposition rates are also addressed. Each section concludes with methods of age estimation applicable to monodontids, and suggestions on the focus of future age-estimation research.

scholarly journals Laryngeal and soft palate valving in the harbour seal (Phoca vitulina)

2020 ◽  
Vol 223 (20) ◽  
pp. jeb230201
Author(s):  
Arlo Adams ◽  
Wayne Vogl ◽  
Camilla Dawson ◽  
Stephen Raverty ◽  
Martin Haulena ◽  
...  
Keyword(s):  
Soft Palate ◽  
Marine Mammals ◽  
Vocal Folds ◽  
Phoca Vitulina ◽  
Harbour Seal ◽  
Upper Aerodigestive Tract ◽  
Laryngeal Inlet ◽  
Harbour Seals ◽  
Lateral Margins ◽  
And Function

ABSTRACTEffective ‘valving’ in the upper aerodigestive tract (UAT) is essential to temporarily separate the digestive and respiratory pathways. Marine mammals are largely dedicated to feeding underwater, and in many cases swallowing prey whole. In seals, little work has been done to explore the anatomy and function of the UAT in the context of valving mechanisms that function to separate food and air pathways. Here we use videofluoroscopy, gross dissection, histology and computed tomography (CT) renderings to explore the anatomy of the larynx and soft palate in the harbour seal (Phoca vitulina), and generate models for how valving mechanisms in the head and neck may function during breathing, phonating, diving and swallowing. Harbour seals have an elevated larynx and the epiglottis may rise above the level of the soft palate, particularly in pups when sucking. In addition, the corniculate and arytenoid cartilages with associated muscles form most of the lateral margins of the laryngeal inlet and vestibule, and move independently to facilitate airway closure. The corniculate cartilages flex over the laryngeal inlet beneath the epiglottis to completely close the laryngeal vestibule and inlet. The vocal folds are thick and muscular and the medial margin of the folds contains a small vocal ligament. The soft palate has well-defined levator veli palatini muscles that probably function to elevate the palate and close the pharyngeal isthmus during feeding. Our results support the conclusion that harbour seals have evolved UAT valving mechanisms as adaptations to a marine environment that are not seen in terrestrial carnivores.

scholarly journals Accuracy and precision of age determination using growth layer groups for California sea lions ( Zalophus californianus ) with known ages

2019 ◽  
Vol 35 (4) ◽  
pp. 1355-1368 ◽  
Author(s):  
Lauren B. Rust ◽  
Kerri Danil ◽  
Sharon R. Melin ◽  
Brent Wilkerson
Keyword(s):  
Age Determination ◽  
Zalophus Californianus ◽  
Growth Layer ◽  
California Sea Lions ◽  
Sea Lions ◽  
Accuracy And Precision ◽  
Layer Groups

Variability of Dentin Deposits in Tursiops truncatus

1980 ◽  
Vol 37 (4) ◽  
pp. 712-716 ◽  
Author(s):  
Clifford A. Hui
Keyword(s):  
Tursiops Truncatus ◽  
Age Determination ◽  
Growth Layer ◽  
Posterior Teeth ◽  
Annual Cycles ◽  
Left And Right ◽  
Layer Groups

Dentin is deposited in approximately annual cycles in Tursiops truncatus for at least the first 11 yr. There were no consistent differences in the dentinal layer count between the left and right sides nor between the mandible and maxilla in the teeth of nine animals studied. The posterior teeth, however, have a greater number of growth layer groups (GLGs). The differences in the number of GLGs among teeth of the same individual increase unpredictably when there are more than about 15 GLGs in the posterior teeth. Only minimal age may be determined using dentinal counts.Key words: age determination, dentin, dolphins, odontocetes, teeth, Tursiops

scholarly journals A note on the age at sexual maturity of humpback whales

2020 ◽  
pp. 71-73
Author(s):  
Peter B. Best
Keyword(s):  
Sexual Maturity ◽  
Gulf Of Maine ◽  
Accumulation Rate ◽  
Age Determination ◽  
Biological Data ◽  
Humpback Whales ◽  
Natural Mortality ◽  
Growth Layer ◽  
Younger Age ◽  
Layer Groups

The conclusion of researchers in the 1950s that humpback whales reached sexual maturity at about age five was largely influenced by their interpretation of baleen tracings, and to achieve consistency with these tracings the accumulation rate of ear plug laminations (growth layer groups: GLGs) was assumed to be two per year. However, ovulation and natural mortality rates calculated by these researchers under the same assumption produced estimates that are difficult to reconcile with other biological data or with more recent estimates using individual re-sighting data. Such disparities are reduced or disappear when an annual accumulation rate is used, in which case their ear plug data would have indicated a mean age at sexual maturity of 9–11 years. Recent estimates of the age of female humpback whales at first calving using longitudinal studies of photoidentified individuals have produced conflicting results, some (from southeastern Alaska) being compatible with the earlier age-determination studies, others (from the Gulf of Maine) suggesting a much younger age.

scholarly journals Tooth Microwear Texture in the Eastern Atlantic Harbour Seals (Phoca vitulina vitulina) of the German Wadden Sea and Its Implications for Long Term Dietary and Ecosystem Changes

2021 ◽  
Vol 9 ◽  
Author(s):  
Elehna Bethune ◽  
Ellen Schulz-Kornas ◽  
Kristina Lehnert ◽  
Ursula Siebert ◽  
Thomas M. Kaiser
Keyword(s):  
Health Status ◽  
Marine Mammal ◽  
Marine Mammals ◽  
Wadden Sea ◽  
Anthropogenic Impacts ◽  
Phoca Vitulina ◽  
Dental Microwear ◽  
Future Health ◽  
Terrestrial Mammals ◽  
Harbour Seals

Marine mammals are increasingly threatened in their habitat by various anthropogenic impacts. This is particularly evident in prey abundance. Understanding the dietary strategies of marine mammal populations can help predict implications for their future health status and is essential for their conservation. In this study we provide a striking example of a new dietary proxy in pinnipeds to document marine mammal diets using a dental record. In this novel approach, we used a combination of 49 parameters to establish a dental microwear texture (DMTA) as a dietary proxy of feeding behaviour in harbour seals. This method is an established approach to assess diets in terrestrial mammals, but has not yet been applied to pinnipeds. Our aim was to establish a protocol, opening DMTA to pinnipeds by investigating inter- and intra-individual variations. We analysed the 244 upper teeth of 78 Atlantic harbour seals (Phoca vitulina vitulina). The specimens were collected in 1988 along the North Sea coast (Wadden Sea, Germany) and are curated by the Zoological Institute of Kiel University, Germany. An increasing surface texture roughness from frontal to distal teeth was found and related to different prey processing biomechanics. Ten and five year old individuals were similar in their texture roughness, whereas males and females were similar to each other with the exception of their frontal dentition. Fall and summer specimens also featured no difference in texture roughness. We established the second to fourth postcanine teeth as reference tooth positions, as those were unaffected by age, sex, season, or intra-individual variation. In summary, applying indirect dietary proxies, such as DMTA, will allow reconstructing dietary traits of pinnipeds using existing skeletal collection material. Combining DMTA with time series analyses is a very promising approach to track health status in pinniped populations over the last decades. This approach opens new research avenues and could help detect dietary shifts in marine environments in the past and the future.

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