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


  • Fiona L. Read NAMMCO, Instituto de Investigaciones Marinas (CSIC),
  • Aleta A. Hohn NOAA National Marine Fisheries Service
  • Christina H. Lockyer NAMMCO, Age Dynamics




marine mammal, age estimation, ageing, monodontid, beluga, narwhal, Delphinapterus leucas, Monodon monoceros


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.


Amano M, Miyazaki N and Petrov EA (2000) Age determination and growth of Baikal seals (Phoca sibirica). Adv. Ecol. Res. 31:449-462. https://doi.org/10.1016/S0065-2504(00)31024-8

Arnbom TA, Lunn NJ, and Boyd IL (1992) Aging live Antarctic fur seals and southern elephant seals. Mar. Mamm. Sci. 8:37-43. https://doi.org/10.1111/j.1748-7692.1992.tb00123.x

Auger-Méthé M, Marcoux M and Whitehead H (2010) Nicks and notches of the dorsal ridge: promising mark types for the photo-identification of narwhals. Mar. Mamm. Sci. 26:663-678. https://doi.org/10.1111/j.1748-7692.2009.00369.x

Augusteyn RC (2007) Growth of the human eye lens. Mol. Vis. 13:252-257. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633484/

Avens LI and Snover ML (2013) Age and age estimation in sea turtles. In: Wyneken J, Lohmann KL, and Musick JA (eds.); The biology of sea turtles, CRC Press, Boca Raton, FL, 97-134.

Azevedo CT, Iwasaki JL, Azevedo RM, Santos Neto EB, Tamy WP, Brito JL, Barbosa LA, Silveira LS (2015) Thoracic limb bone development in Sotalia guianensis (Van Beneden 1864) along the coastline of Espirito Santo, Brazil. J. Mammal. 96:541-551. https://doi.org/10.1093/jmammal/gyv059

Bada JL, Schroeder RA and Carter GF (1974) New Evidence for Antiquity of Man in North-America Deduced from Aspartic-Acid Racemization. Science 184:791-793. http://dx.doi.org/10.1126/science.184.4138.791

Bada JL, and Schroeder RA (1975) Amino acid racemization reactions and their geochemical implications. Naturwissenschaften 62: 71–79. https://doi.org/10.1007/BF00592179

Bada J, Brown S and Masters P (1980) Age determination of marine mammals based on aspartic acid racemization in the teeth and lens nucleus. In: Perrin, W.F. and Myrick, A.C. (eds.); Age determination of toothed whales and sirenians. R eport of the International Whaling Commission (Special Issue 3), Cambridge, 113-118.

Bada J, Mitchell E and Kemper B (1983) Aspartic acid racemization in narwhal teeth. Nature 303:418-420. http://dx.doi.org/10.1038/303418a0

Bauer R, Johnson A and Scheffer V (1964) Eye lens weight and age in the fur seal. J. Wildl. Manage. 28:374-376. http://www.jstor.org/stable/3798101

Beamish RJ and McFarlane GA (1983) The forgotten requirement for age validation in fisheries biology. T. Am. Fish. Soc. 112:735-743. https://doi.org/10.1577/1548-8659(1983)112<735:TFRFAV>2.0.CO;2

Bengtson JL (1988) Long-term trends in the foraging patterns of female Antarctic fur seals at South Georgia. In D. Sahrhage (ed.). Antarctic Ocean Resources Variability. Springer-Verlag, Berlin Heidelberg, 286-291. https://doi.org/10.1007/978-3-642-73724-4_24

Benjaminsen T (1973) Age determination and the growth and age distribution from cementum growth layers of bearded seals at Svalbard. Fiskeridirektoratets Skr (Havundersok) 16:159-170.

Bernt KE, Hammill MO and Kovacs KM (1996) Age estimation of grey seals (Halichoerus grypus) using incisors. Mar. Mamm. Sci. 12:476-482. https://doi.org/10.1111/j.1748-7692.1996.tb00602.x

Best P (1970) The Sperm whale (Physeter catodon) off the west coast of South Africa. Life, growth and mortality. Investigation Report, Division of Sea Fisheries, South Africa 79:1-27.

Best P (1976) Tetracycline marking and rate of growth layer formation in teeth of a dolphin (Lagenorhynchus obscurus). S. Afr. J. Sci. 72:216-218.

Best PM, Meÿer P and Lockyer C (2010) Killer whales in South African waters - a review of their biology. Afr. J. Mar. Sci. 32:171-186. https://doi.org/10.2989/1814232X.2010.501544

Bester MN (1995) Reproduction in the female sub-Antarctic fur seal (Arctocephalus tropicalis). Mar. Mamm. Sci. 11:362-375. https://doi.org/10.1111/j.1748-7692.1995.tb00291.x

Bize P, Criscuolo F, Metcalfe NB, Nasir L and Monaghan P (2009) Telomere dynamics rather than age predict life expectancy in the wild. Proc. Roy. Soc. Lond. B – Biol. Sci. 276:1679–1683. http://dx.doi.org/10.1098/rspb.2008.1817

Bjørge A, Hohn AA, Kvam T, Lockyer C, Schweder T and Aarefjord H (1995) Report of the harbour porpoise age determination workshop. In: Bjørge, A. and Donovan, G.P. (eds.); Biology of the phocoenids. International Whaling Commission, Cambridge, 16:477-491.

Blundell GM and Pendleton GW (2008) Estimating age of harbor seals (Phoca vitulina) with incisor teeth and morphometrics. Mar. Mamm. Sci. 24:577-590. https://doi.org/10.1111/j.1748-7692.2008.00194.x

Bodkin JL, Ames JA, Jameson RJ, Johnson AM (1997) Estimating age of sea otters with cementum layers in the first premolar. J. Wildl. Manage. 61:967-973. http://www.jstor.org/stable/3802207

Born E (1982) Reproduction in the female hooded seal (Cystophora cristata Erxleben) at south Greenland. J. Northwest Atl. Fish. Sci. 3:57-62. https://doi.org/10.2960/J.v3.a5

Bowen WD, Sergeant DE and Øritsland T (1983) Validation of age estimation in the harp seal (Phoca groenlandica) using dentinal annuli. Can. J. Fish. Aquat. Sci. 40:1430-1441. https://doi.org/10.1139/f83-165

Boyd IL and Roberts JP (1993) Tooth growth in male Antarctic fur seals (Arctocephalus gazella) from South Georgia: an indicator of long-term growth history. J. Zool. 229:177-190. https://doi.org/10.1111/j.1469-7998.1993.tb02630.x

Boyde A (1980) Histological studies of dental tissues of odontocetes. In: Perrin, W.F. and Myrick, A.C. (eds.); Age determination of toothed whales and sirenians. Report of the International Whaling Commission (Special Issue 3), Cambridge, 65-87.

Braham H (1984) Review of reproduction in the white whale (Delphinapterus leucas), narwhal (Monodon monoceros), and Irrawaddy dolphin (Orcaella brevirostris) with comments on stock assessment. In: Perrin, W.F., Brownell, R.L. and DeMaster, D.P. (eds.); Reproduction in whales, dolphins and porpoises. Report of the International Whaling Commission (Special Issue 6), Cambridge, 81-89.

Brill K, Marmontel M, Bolen-Richardson M and Stewart REA (2015) Inter-lab comparison of precision and recommended methods for age estimation of Florida manatee (Trichechus manatus latirostris) using growth layer groups in earbones. NAMMCO Sci. Publ. Volume 10. http://dx.doi.org/10.7557/3.3786

Brodie PF (1969) Mandibular layering in Delphinapterus Leucas and age determination. Nature 221:956-958. http://dx.doi.org/10.1038/221956a0

Brodie PF (1971) Reconsideration of aspects of growth, reproduction, and behavior of white whale (Delphinapterus leucas) with reference to Cumberland Sound, Baffin Island, population. J. Fish. Res. Board Can. 28:1309-1318. https://doi.org/10.1139/f71-198

Brodie PF (1972) Significance of accessory corpora lutea in odontocetes with reference to Delphinapterus leucas. J. Mammal. 53:614-615. http://dx.doi.org/10.2307/1379056

Brodie PF (1982) The beluga (Delphinapterus leucas); growth at age based on a captive specimen and a discussion of factors affecting natural mortality estimates. Rep. Int. Whal. Comm. 32:445-447.

Brodie P, Ramirez K and Haulena M (2013) Growth and Maturity of White whales (Delphinapterus leucas) in Cumberland Sound, Canada, Compared to Those Raised in Captivity: evidence for GLG/2. J. Cet. Res. Manage. 13:1-18.

Brownell RL, Tillman MF, di Sciara GN, Berggren P and Read AJ (2000) Further scrutiny of scientific whaling. Science 290:1696. http://dx.doi.org/10.1126/science.290.5497.1696a

Buffrénil V de (1982) Données préliminaires sur la présence de lignes d’arrêt de croissance périostiques dans la mandibule du marsouin commun (Phocoena phocoena (L.)), et leur utilisation comme indicateur de l’âge. Can. J. Zool. 60:2557-2567. In French. https://doi.org/10.1139/z82-328

Buffrénil V de, Dabin W, and Zylbergerg L (2004) Histology and growth of the cetacean petro-tympanic bone complex. J. Zool. 262:371-381. https://doi.org/10.1017/S0952836903004758

Burns JJ and Seaman GA (1986) Investigations of belukha whales in coastal waters of western and northern Alaska. II. Biology and Ecology. U.S. Department of Commerce, NOAA, OCSEAP Final Report 56:221-357.

Butti C, Corain L, Cozzi B, Podesta M, Pirone A, Affronte M and Zotti A (2007) Age estimation in the Mediterranean bottlenose dolphin (Tursiops truncatus Montagu 1821) by bone density of the thoracic limb. J. Anat. 211:639-646. https://doi.org/10.1111/j.1469-7580.2007.00805.x

Calvert W and Ramsay M (1998) Evaluation of age determination of polar bears by counts of cementum growth layer groups. Ursus 10:449-453. http://www.jstor.org/stable/3873156

Calzada N, Aguilar A, Lockyer C and Grau E (1997) Patterns of growth and physical maturity in the western Mediterranean striped dolphin (Stenella coeruleoalba) (Cetacea: Odontoceti). Can. J. Zool. 75:632-637. https://doi.org/10.1139/z97-078

Campana S (1997) Use of radiocarbon from nuclear fallout as a dated marker in the otoliths of haddock (Melanogrammus aeglefinus). Mar. Ecol. Prog. Ser. 150:49-56. http://www.jstor.org/stable/24857596

Campana S (2001) Accuracy, precision and quality control in age determination, including a review of the use and abuse of age validation methods. J. Fish Biol. 59:197-242. https://doi.org/10.1111/j.1095-8649.2001.tb00127.x

Campana SE and Stewart REA (2014) Bomb dating, age validation and quality control of age determinations of monodontids and other marine mammals. NAMMCO Sci. Publ. Vol.10. http://dx.doi.org/10.7557/3.2987

Caron L and Smith T (1990) Philopatry and site tenacity of belugas (Delphinapterus leucas) hunted by the Inuit at the Nastapoka Estuary, eastern Hudson Bay. Can. Bull. Fish. Aquat. Sci. 224:69-79.

Chambellant M and Ferguson SH (2009) Ageing live ringed seals (Phoca hispida): Which tooth to pull? Mar. Mamm. Sci. 25:478-486. https://doi.org/10.1111/j.1748-7692.2008.00269.x

Cheney B, Corkrey R, Durban JW, Grellier K, Hammond PS, Islas-Villanueva V, Janik VM, Lusseau SM, Parsons KM, Quick NJ, Wilson B and Thompson PM (2014) Long-term trends in the use of a protected area by small cetaceans in relation to changes in population status. Glob. Ecol. Conserv. 2:118-128. https://doi.org/10.1016/j.gecco.2014.08.010

Childerhouse S, Dickie G, and Hessel G (2004) Ageing live New Zealand sea lions (Phocarctos hookeri) using the first post-canine tooth. Wildl. Res. 31:177-181. https://doi.org/10.1071/WR03006

Chittleborough R (1959) Determination of age in the humpback whale (Megaptera nodosa Bonaterre). Aust. J. Mar. Freshw. Res. 10:125-143. https://doi.org/10.1071/MF9590125

Christensen I (1981) Age determination of minke whales (Balaenoptera acutorostrata) from laminated structures in the tympanic bullae. Rep. Int. Whal. Comm. 31:245-253.

Christensen-Dalsgaard SN, Aars J, Andersen M, Lockyer C and Yoccoz NG (2010) Accuracy and precision in estimation of age of Norwegian Arctic polar bears (Ursus maritimus) using dental cementum layers from known-age individuals. Pol. Biol. 33:589-597. https://doi.org/10.1007/s00300-009-0734-y

Clapham P (1992) Age at attainment of sexual maturity in humpback whales, Megaptera novaeangliae. Can. J. Zool. 70:1470-1472. https://doi.org/10.1139/z92-202

Clark ST, Odell DK and Lacinak CT (2000) Aspects of growth in captive killer whales (Orcinus orca). Mar. Mamm. Sci. 16:110-123. https://doi.org/10.1111/j.1748-7692.2000.tb00907.x

Dabin W, Cossais F, Pierce GJ and Ridoux V (2008) Do ovarian scars persist with age in all cetaceans: new insight from the short-beaked common dolphin (Delphinus delphis Linnaeus 1758). Mar. Biol. 156:127-139. https://doi.org/10.1007/s00227-008-1070-4

Dalebout ML, Steel D and Baker CS (2008) Phylogeny of the beaked whale genus Mesoplodon (Ziphiidae: Cetacea) revealed by nuclear introns: implications for the evolution of male tusks. Syst. Biol. 57: 857-875. https://doi.org/10.1080/10635150802559257

Dellabianca NA, Hohn AA, Goodall NP, Pousa JL, Macleod CD and Lima M (2012) Influence of climate oscillations on dentinal deposition in teeth of Commerson's dolphin. Glob. Chang. Biol. 18:2477-2486. https://doi.org/10.1111/j.1365-2486.2012.02707.x

Dennis C (2006) A gentle way to age. Nature 442:507-508. https://doi.org/10.1038/442507a

Dietz R, Heide-Jørgensen MP, Härkönen T, Teilmann J and Valentin N (1991) Age-determination of European harbour seal (Phoca vitulina L.). Sarsia 76:17-21. https://doi.org/10.1080/00364827.1991.10413461

DiGiancamillo M, Rattegni G, Podesta M, Cagnolaro L, Cozzi B and Leonardi L (1998) Postnatal ossification of the thoracic limb in striped dolphins (Stenella coeruleoalba Meyen 1833) from the Mediterranean Sea. Can. J. Zool. 76:1286-1293. https://doi.org/10.1139/z98-055

Doidge D (1990) Age-length and length-weight comparisons in the beluga (Delphinapterus leucas). Can. Bull. Fish. Aquat. Sci. 224:59-68.

Domning DP (2009) Sirenian evolution. In: Perrin WF, Würsig B and Thewissen JGM (eds.); Encyclopaedia of Marine Mammals (Second Edition). Academic Press, London, 1011-1019. https://doi.org/10.1016/B978-0-12-373553-9.00236-4

Domning DP and Hayek LAC (1984) Horizontal tooth replacement in the Amazonian manatee (Trichechus inunguis). Mammalia 48:105–127. https://doi.org/10.1515/mamm.1984.48.1.105

Domning D and Myrick A (1980) Tetracycline marking and the possible layering rate of bone in an Amazonian manatee (Trichechus inunguis). In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Rep. Int. Whal. Comm. (Special Issue 3), Cambridge, 203-207.

Druffel EM and Linick TW (1978) Radiocarbon in Annual Coral Rings of Florida. Geophys. Res. Lett. 5:913-916. https://doi.org/10.1029/GL005i011p00913

Dunshea G, Duffield D, Gales N, Hindell M, Wells RS and Jarman SN (2011) Telomeres as age markers in vertebrate molecular ecology. Mol. Ecol. Res. 11:225-235. https://doi.org/10.1111/j.1755-0998.2010.02976.x

Evans K and Robertson K (2001) A note on the preparation of sperm whale (Physeter macrocephalus) teeth for age determination. J. Cet. Res. Manage. 3:101-107.

Evans RD, Richner P, and Outridge PM (1995) Micro-spatial variations in heavy metals in the teeth of walrus as determined by laser ablation ICP-MS: The potential for reconstructing a history of metal exposure. Arch. Environ. Contam. Toxicol. 28:55-60. https://doi.org/10.1007/BF00213969

Evans K, Hindell MA, Robertson K, Lockyer C and Rice D (2002) Factors affecting the precision of age determination of sperm whales (Physeter macrocephalus). J. Cet. Res. Manage. 4:193-201.

Fancy SG (1980) Preparation of mammalian teeth for age determination by cementum layers: a review. Wildl. Soc. Bull. 8:242-248. http://www.jstor.org/stable/3781696

Fisher HD (1954) Studies on reproduction in the harp seal (Phoca groenlandica Erxleben) in the north-west Atlantic. Manuscr. Rep. Fish. Res. Board Can. 588:1-109.

Frie AK, Fagerheim KA, Hammill MO, Kapel FO, Lockyer C, Stenson GB, Rosing-Asvid A and Svetochev V (2011) Error patterns in age estimation of harp seals (Pagophilus groenlandicus): results from a transatlantic, image-based, blind-reading experiment using known-age teeth. ICES J. Mar. Sci. 68:1942-1953. https://doi.org/10.1093/icesjms/fsr116

Frie AK, Hammill MO, Hauksson E, Lind Y, Lockyer C, Stenman O and Svetocheva O (2013) Error patterns in age estimation and tooth readability assignment of grey seals (Halichoerus grypus): results from a transatlantic, image-based, blind-reading study using known-age animals. ICES J. Mar. Sci. 70:418-430. https://doi.org/10.1093/icesjms/fss169

Frost HM (1968) Tetracycline bone labelling in anatomy. Am. J. Phys. Anthr. 29:183-195. https://doi.org/10.1002/ajpa.1330290212

Gabriele CM, Lockyer C, Straley JM, Jurasz CM and Kato H (2010) Sighting history of a naturally marked humpback whale (Megaptera novaeangliae) suggests ear plug growth layer groups are deposited annually. Mar. Mamm. Sci. 26:443-450. https://doi.org/10.1111/j.1748-7692.2009.00341.x

Galatius A, Andersen MBER, Haugan B, Langhoff HE and Jespersen A (2006) Timing of epiphyseal development in the flipper skeleton of the harbour porpoise (Phocoena phocoena) as an indicator of paedomorphosis. Acta Zool. 87:77-82. https://doi.org/10.1111/j.1463-6395.2006.00223.x

Gambell R and Grzegorzewska C (1967) The rate of lamina formation in sperm whale teeth. Norsk Hvalfangst-Tidende 56:117-121.

Garde E, Heide-Jørgensen MP, Hansen SH, Nachman G and Forchhammer MC (2007) Age-specific growth and remarkable longevity in narwhals (Monodon monoceros) from West Greenland as estimated by aspartic acid racemization. J. Mammal. 88:49-58. https://doi.org/10.1644/06-MAMM-A-056R.1

Garde E, Frie AK, Dunshea G, Hansen SH, Kovacs KM and Lydersen C (2010) Harp seal ageing techniques-teeth, aspartic acid racemization, and telomere sequence analysis. J. Mammal. 91:1365-1374. https://doi.org/10.1644/10-MAMM-A-080.1

Garde E, Heide-Jørgensen MP, Ditlevsen S and Hansen SH (2012) Aspartic acid racemization rate in narwhal (Monodon monoceros) eye lens nuclei estimated by counting of growth layers in tusks. Pol. Res. 31:15865. http://dx.doi.org/10.3402/polar.v31i0

Garde E, Hansen SH, Ditlevsen S, Tvermosegaard KT, Hansen J, Harding KC and Heide-Jørgensen MP (2015) Life history parameters of narwhals (Monodon monoceros) from Greenland. J. Mammal. 96:866–879. https://doi.org/10.1093/jmammal/gyv110

Garde E, Bertelsen MF, Ditlevsen S, Heide-Jørgensen MP, Nielsen NH, Frie AK, Olafsdottir D, Siebert U and Hansen SH (2018) Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature. NAMMCO Sci. Publ. Vol. 10. http://dx.doi.org/10.7557/3.4400 .

Garlich-Miller JL, Stewart REA, Stewart BE and Hiltz EA (1993) Comparison of mandibular with cemental growth layer counts for aging Atlantic walrus (Odobenus rosmarus rosmarus). Can. J. Zool. 71:163-167. https://doi.org/10.1139/z93-022

Garrigue C, Oremus M, Dodemont R, Bustamante P, Kwiatek O, Libeau G, Lockyer C, Vivier JC and Dalebout ML (2016) A mass stranding of seven Longman’s beaked whale (Indopacetus pacificus) in New Caledonia, South Pacific. Mar. Mamm. Sci. 32 884–910. https://doi.org/10.1111/mms.12304

Garshelis DL (1984) Age estimation of living sea otters. J. Wildl. Manage. 48:456-463. http://dx.doi.org/10.2307/3801178

George JC and Bockstoce JR (2008) Two historical weapon fragments as an aid to estimating the longevity and movements of bowhead whales. Pol. Biol. 31:751-754. https://doi.org/10.1007/s00300-008-0407-2

George JC, Bada J, Zeh J, Scott L, Brown SE, O'Hara T and Suydam R (1999) Age and growth estimates of bowhead whales (Balaena mysticetus) via aspartic acid racemization. Can. J. Zool. 77:571-580. https://doi.org/10.1139/z99-015

George JC, Follmann E, Zeh J, Sousa M, Tarpley R, Suydam R and Horstmann-Dehn L (2011) A new way to estimate the age of bowhead whales (Balaena mysticetus) using ovarian corpora counts. Can. J. Zool. 89:840-852. https://doi.org/10.1139/z11-057

Goren AD, Brodie PF, Spotte S, Ray GC, Kaufman HW, Gwinnett AJ, Sciubba JJ and Buck JD (1987) Growth layer groups (GLGs) in the teeth of an adult beluga whale (Delphinapterus leucas) of known-age: evidence for 2 annual layers. Mar. Mamm. Sci. 3:14-21. https://doi.org/10.1111/j.1748-7692.1987.tb00148.x

Grier SJ, Turner AS and Alvis MR (1996) The use of dual-energy x-ray absorptiometry in animals. Investig. Radiol. 31:50-62. https://doi.org/10.1097/00004424-199601000-00008

Grue H and Jensen B (1979) Review of the formation of incremental lines in tooth cementum of terrestrial mammals. Dan. Rev. Game Biol. 11:1-48.

Guglielmini C, Zotti A, Bernardini D, Pietra M, Podesta M and Cozzi B (2002) Bone density of the arm and forearm as an age indicator in specimens of stranded striped dolphins (Stenella coeruleoalba). Anat. Rec. 267:225-230. https://doi.org/10.1002/ar.10107

Gurevich V, Stewart B and Cornell L (1980) The use of tetracycline in age determination of common dolphins (Delphinus delphis). In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Rep. Int. Whal. Comm. (Special Issue 3), Cambridge, 165-169.

Hall ME, Nasir L, Daunt F, Gault EA, Croxall JP, Wanless S and Monaghan P (2004) Telomere loss in relation to age and early environment in long-lived birds. Proc. R. Soc. Lond. Ser. B-Biol. Sci. 271:1571-1576. http://dx.doi.org/10.1098/rspb.2004.2768

Haussmann MF and Mauck RA (2008) New strategies for telomere-based age estimation. Mol. Ecol. Res. 8:264-274. https://doi.org/10.1111/j.1471-8286.2007.01973.x

Haussmann MF and Vleck CM (2002) Telomere length provides a new technique for aging animals. Oecologia 130:325-328. https://doi.org/10.1007/s00442-001-0827-y

Haussmann MF, Winkler DW, O’Reilly KM, Huntington CE, Nisbet ICT and Vleck CM (2003) Telomeres shorten more slowly in long-lived birds and mammals than in short-lived ones. Proc. R. Soc. Lond. Ser. B-Biol. Sci. 270:1387–1392. http://dx.doi.org/10.1098/rspb.2003.2385

Hay K (1980) Age determination of the narwhal (Monodon monoceros L.). In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Rep. Int. Whal. Comm. (Special Issue 3), Cambridge, 119-132.

Hay K (MS) (1984) The life history of the narwhal (Monodon monoceros) in the eastern Canadian Arctic. [Ph.D. thesis]. McGill University, Canada, 254 pp.

Hay KA and Mansfield AW (1989) Narwhal, Monodon monoceros Linnaeus, 1758. In: Ridgway SH and Richardson RJ (eds.); Handbook of marine mammals, vol. 4. River dolphins and the larger toothed whales. Academic Press, London, 145–176.

Hazard K (1988) Beluga whale (Delphinapterus leucas). In: Lentfer JW (ed.); Selected marine mammals of Alaska: species, accounts with research and management recommendations. Marine Mammal Commission, Washington, DC, 195-235.

Heide-Jørgensen MP and Lockyer C (2001) Age and sex distributions in the catches of belugas (Delphinapterus leucas) in West Greenland and in western Russia. Mammal. Biol. 66:215-227.

Heide-Jørgensen MP and Teilmann J (1994) Growth, reproduction, age structure and feeding habits of white whales (Delphinapterus leucas) in West Greenland waters. Medd. Grønl. Biosci. 39:195-212.

Heide-Jørgensen MP, Jensen J, Larsen, A.H., Teilmann, J. and Neurohr, B. 1994. Age estimation of white whales (Delphinapterus leucas) from Greenland. Medd. Grønl. Biosci. 39:187-193.

Helfman PM and Bada JL (1975) Aspartic-Acid Racemization in Tooth Enamel from Living Humans. Proc. Nat. Acad. Sci. USA. 72:2891-2894. https://doi.org/10.1073/pnas.72.8.2891

Helfman PM and Bada JL (1976) Aspartic-acid racemization in dentin as a measure of aging. Nature. 262:279-281. http://dx.doi.org/10.1038/262279b0

Herman DP, Matkin CO, Ylitalo GM, Durban JW, Hanson M, Dahlheim ME, Straley JM, Wade PR, Tilbury KL, Boyer RH, Pearce RW and Krahn MM (2008) Assessing age distributions of killer whale (Orcinus orca) populations from the composition of endogenous fatty acids in their outer blubber layers. Mar. Ecol. Prog. Ser. 372:289-302. http://www.jstor.org/stable/24872738

Herman DP, Ylitalo GM, Robbins J, Straley JM, Gabriele CM, Clapham PJ, Boyer RH, Tilbury KL, Pearce RW and Krahn MM (2009) Age determination of humpback whales (Megaptera novaeangliae) rough blubber fatty acid compositions of biopsy samples. Mar. Ecol. Prog. Ser. 392:277-293. http://www.jstor.org/stable/24873697

Hewer H (1964) The determination of age, sexual maturity, longevity and a life-table in the grey seal (Halichoerus grypus). Proc. Zool. Soc. Lond. 142:593-623. https://doi.org/10.1111/j.1469-7998.1964.tb04631.x

Hohn A (1980) Analysis of growth layers in the teeth of Tursiops truncatus using light microscopy, microradiography, and SEM. In: Perrin, W.F. and Myrick, A.C. (eds.); Age determination of toothed whales and sirenians. Rep. Int. Whal. Comm. (Special Issue 3), Cambridge, 155-160.

Hohn A (1990) Reading between the lines: analysis of age estimation in dolphins. In: Leatherwood S and Reeves RR (eds.); The bottlenose dolphin. Academic Press, San Diego, 575-585. https://doi.org/10.1016/B978-0-12-440280-5.50037-8

Hohn A (2009) Age estimation. In: Perrin WF, Würsig B and Thewissen JGM (eds.); Encyclopaedia of Marine Mammals (Second Edition). Academic Press, London, 11-17. https://doi.org/10.1016/B978-0-12-373553-9.00004-3

Hohn A and Fernandez S (1999) Biases in dolphin age structure due to age estimation technique. Mar. Mamm. Sci. 15:1124-1132. https://doi.org/10.1111/j.1748-7692.1999.tb00881.x

Hohn A and Lockyer C (1995) Protocol for obtaining age estimates from harbour porpoise teeth. In: Bjørge A and Donovan GP (eds.); Biology of the phocoenids. International Whaling Commission, Cambridge, 16:494-496.

Hohn A and Lockyer C (1999) Growth layer patterns in teeth from two known-history beluga whales: reconsideration of deposition rates (IWC/SC/51/SM4). Submitted to the International Whaling Commission Scientific Committee, Grenada, May 1999, 17 pp.

Hohn A and Lockyer C (2011) Presentation 20: Age validation through known history captive studies in belugas. In: Hohn AA, Lockyer C and Acquarone M (eds.); Report of the workshop on age estimation in monodontids, Tampa, USA. NAMMCO Sci. Publ. Vol. 10. http://dx.doi.org/10.7557/3.3743

Hohn A, Scott MD, Wells RS, Sweeney JC and Irvine AB (1989) Growth layers in teeth from known-age, free ranging bottlenose dolphins. Mar. Mamm. Sci. 5:315-342. https://doi.org/10.1111/j.1748-7692.1989.tb00346.x

Hohn AA, Lockyer C and Acquarone M (2016) Report of the workshop on age estimation in monodontids. Tampa, Florida, USA. 26-27 November 2011. NAMMCO Sci. Publ. Vol. 10. http://dx.doi.org/10.7557/3.3743

Hui C (1980) Variability of dentin deposits in Tursiops truncatus. Can. J. Fish. Aquat. Sci. 37:712-716. https://doi.org/10.1139/f80-090

Ichihara T (1966) Criterion for determining age of fin whale with reference to ear plug and baleen plate. Sci. Rep. Whal. Res. Inst. Tokyo 20:17-82.

IWC–International Whaling Commission (1969) Report of the meeting on age determination of whales 19:131-137.

Izzo C, Hamer DJ, Bertozzi T, Donnellan SC and Gillanders BM (2011) Telomere length and age in pinnipeds: the endangered Australian sea lion as a case study. Mar. Mamm. Sci. 27:841-851. https://doi.org/10.1111/j.1748-7692.2010.00450.x

Johnston D, Joachim D, Bachmann P, Kardong KV, Stewart R, Dix L, Strickland M and Watt I (1987) Aging furbearers using tooth structure and biomarkers. In: Novak M, Baker JA, Obbard ME and Malloch B (eds.); Wild furbearer management and conservation in North America. Ontario Ministry of Natural Resources, Ontario, 228-243.

Juola FA, Haussmann MF, Dearborn DC and Vleck CM (2006) Telomere shortening in a long-lived marine bird: cross-sectional analysis and test of an aging tool. Auk 123:775-783. https://doi.org/10.1642/0004-8038(2006)123[775:TSIALM]2.0.CO;2

Kalish JM (1993) Pre-bomb and post-bomb radiocarbon in fish otoliths. Earth Planet. Sci. Lett. 114:549-554. https://doi.org/10.1016/0012-821X(93)90082-K

Kalish JM (1995) Radiocarbon and fish biology. In: Secor, D.H., Dean, J.M. and Campana, S.E. (eds.); Recent Developments in Fish Otolith Research. University of South Carolina Press, Columbia, 637-653.

Kastelle CR, Shelden KEW and Kimura DK (2003) Age determination of mysticete whales using 210Pb/226Ra disequilibria. Can. J. Zool. 81:21-32. https://doi.org/10.1139/z02-214

Kato H and Sakuramoto K (1991) Age at sexual maturity of southern minke whales: a review and some additional analyses. Rep. Int. Whal. Comm. 41:331-337.

Kato H, Shimadzu Y and Kirishima K (1984) Biological simulation to examine historical changes in age at sexual maturity of the Antarctic minke whale. Rep. Int. Whal. Comm. 34:327-333.

Keklikoglu N and Akinci S (2013) Comparison of three different techniques for histological tooth preparation. Folia Histochem. Cytobiol. 51:286-291. http://dx.doi.org/10.5603/FHC.2013.0039

Ketten DR (1992) The marine mammal ear: Specializations for aquatic audition and echolocation. In: Webster DB, Fay RR, and Popper AN (eds.); The Evolutionary Biology of Hearing. Springer Verlag, 717–750. https://doi.org/10.1007/978-1-4612-2784-7_44

Ketten DR, Odell DK, Domning DP (1992) Structure, function and adaptation of the manatee ear. In: Thomas JA, Kastelein RA and Supin AY (eds.); Marine Mammal Sensory Systems. Plenum Press, New York, 77–95. https://doi.org/10.1007/978-1-4615-3406-8_4

Kleinenberg SE and Klevezal GA (1962) On methods of aging toothed whales. Doklady Akademii Nauk SSSR 145:460-462.

Kleinenberg SE, Yablokov AV, Bel'kovich BM and Tarasevich MN (1964) Beluga (Delphinapterus leucas). Investigation of the species. USSR Academy of Sciences, A N Severtson Institute of Animal Morphology, Nauka, Moscow, 376 pp. Translated from Russian.

Klevezal G (1980) Layers in the hard tissues of mammals as a record of growth rhythms of individuals. In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Report of the International Whaling Commission (Special Issue 3), Cambridge, 89-95.

Klevezal GA (1996) Recording structures of mammals: determination of age and reconstruction of life history. AA Balkema, Rotterdam, 274 pp.

Klevezal G and Kleinenberg S (1967) Age determination of mammals from annual layers in teeth and bones. USSR Academy of Sciences, Moscow, 128 pp. Translated from Russian.

Klevezal G and Mitchell E (1971) Annual layers baleen whale bone. Zoologicheskii Zhurnal 50:1114-1116.

Klevezal GA and Myrick AC (1984) Marks in tooth dentine of female dolphins (Genus stenella) as indicators of parturition. J. Mammal. 65:103-110. https://doi.org/10.2307/1381206

Konrádsson A and Sigurjónsson J (1989) Studies on growth layers in tympanic bullae in fin whales (Balaenoptera physalus) caught off Iceland. Rep. Int. Whal. Comm. 39:277-279.

Koopman HN, Iverson SJ and Gaskin DE (1996) Stratification and age-related differences in blubber fatty acids of the male harbour porpoise (Phocoena phocoena). J. Comp. Phys. B-Biochem. Syst. Environ. Phys. 165:628-639. https://doi.org/10.1007/BF00301131

Koopman HN, Iverson SJ and Read AJ (2003) High concentrations of isovaleric acid in the fats of odontocetes: variation and patterns of accumulation in blubber vs. stability in the melon. J. Comp. Phys. B-Biochem. Syst. Environ. Phys. 173:247-261. https://doi.org/10.1007/s00360-003-0329-9

Kovacs KM and Lavigne DM (1985) Neonatal growth and organ allometry of northwest Atlantic harp seals (Phoca groenlandica). Can. J. Zool. 63:2793-2799. https://doi.org/10.1139/z85-418

Kovacs KM and Lavigne DM (1986) Growth of gray seal (Halichoerus grypus) neonates: differential maternal investment in the sexes. Can. J. Zool. 64:1937-1943. https://doi.org/10.1139/z86-291

Kubota K, S Shibanai, J Kubota and S Togawa (2000) Developmental transition to monophydonty in adaptation to marine life by the northern fur seal (Callorhinus ursinus) (Otariidae). Hist. Biol. 14:91-95. https://doi.org/10.1080/10292380009380557

Kuiken T and Hartmann MG (eds.) (1991) Proceedings of the first European Cetacean Society workshop on ‘Cetacean pathology: dissection techniques and tissue sampling’. European Cetacean Society Newsletter 17:1-38.

Lahnert P (2005) An improved method for determining telomere length and its use in assessing age in blood and saliva. Gerontol. 51:352-356. https://doi.org/10.1159/000086374

Langtimm CA, Beck CA, Edwards HH, Fick-Child KJ, Ackerman BB, Barton SL and Hartley WC (2004) Survival estimates of Florida manatees from photo-identification of individuals. Mar. Mamm. Sci. 20:438–463. https://doi.org/10.1111/j.1748-7692.2004.tb01171.x

Lanyon JM and Sanson GD (2005) Degenerate dentition of the dugong (Dugong dugong), or why a grazer does not need teeth: morphology, occlusion and wear of mouthparts. J. Zool. 268:133-152. https://doi.org/10.1111/j.1469-7998.2005.00004.x

Laws RM (1952) A new method of age determination for mammals. Nature 169:972-973. http://dx.doi.org/10.1038/169972b0

Laws R (1953) A new method of age determination in mammals with special reference to the Elephant Seal (Mirounga leonina L.). Sci. Rep. Falkl. Isl. Dep. Surv. 11 pp.

Laws RM (1960) Laminated structure of bones from some marine mammals. Nature 187:338-339. http://dx.doi.org/10.1038/187338a0

Laws RM (1961) Reproduction, growth and age of southern fin whales. Discov. Rep. 31:327-486.

Lawson et al. (1992) Factors affecting accuracy of age determination in the harp seal, Phoca groenlandica. Mar. Mamm. Sci. 8:169-171. https://doi.org/10.1111/j.1748-7692.1992.tb00378.x

Lee J and Taylor M (1994) Aspects of the polar bear harvest in the Northwest Territories, Canada. Int. Conf. Bear Res. Manage. 9:237–243. http://www.jstor.org/stable/3872707

Lockyer C (1972) The age at sexual maturity of the southern fin whale (Baleanoptera physalus) using annual layer counts in the ear plug. J. Conseil., Conseil Int. l’Explor. Mer. 34:276-294. https://doi.org/10.1093/icesjms/34.2.276

Lockyer C (1974) Investigation of the ear plug of the southern sei whale (Balaenoptera borealis) as a valid means of determining age. J. Conseil., Conseil Int. l’Explor. Mer. 36:71-81. https://doi.org/10.1093/icesjms/36.1.71

Lockyer C (1984) Report of the minke whale ageing workshop. Annex F. Age determination by means of the earplug in baleen whales. Rep. Int. Whal. Comm. 34:692-696.

Lockyer C (1993) A report on patterns of deposition of dentine and cement in teeth of pilot whales, genus Globicephala. In: Donovan GP, Lockyer C and Martin AR (eds.); Biology of northern hemisphere pilot whales. International Whaling Commission, Cambridge, 14:138-161.

Lockyer C (1995) A review of factors involved in zonation in odontocete teeth, and an investigation of the likely impact of environmental factors and major life events on harbour porpoise tooth structure. In: Bjørge A and Donovan GP (eds.); Biology of the phocoenids. International Whaling Commission, Cambridge, 16:511-529.

Lockyer C (1999) Application of a new method to investigate population structure in the harbour porpoise (Phocoena phocoena) with special reference to the North and Baltic seas. J. Cet. Res. Manage. 1:297-304.

Lockyer CH, and Braulik GT (2014) An evaluation of age estimation using teeth from South Asian River dolphins (Platanistidae). NAMMCO Sci. Publ. Vol. 10. http://dx.doi.org/10.7557/3.3268

Lockyer C, Smellie CG, Goodall RNP and Cameron IS (1981) Examination of teeth of Commerson's dolphin (Cephalorhynchus commersonii) for age-determination. J. Zool. 195:123-131. https://doi.org/10.1111/j.1469-7998.1981.tb01896.x

Lockyer C, Benjamins S and Hohn AA (1999) The potential use of tooth morphology and ultrastructure in stock differentiation in Beluga (Delphinapterus leucas) (IWC/SC/51/SM5). Submitted to the International Whaling Commission Scientific Committee, Grenada, May 1999, 23 pp.

Lockyer C, Hohn AA, Doidge D, Heide-Jørgensen MP and Suydam R (2007) Age determination in belugas (Delphinapterus leucas): a quest for validation of dentinal layering. Aquat. Mamm. 33:293-304. https://doi.org/10.1578/AM.33.3.2007.293

Lockyer C, Mackey B, Read FL, Härkönen T and Hasselmeier I (2010) Age determination methods in harbour seals (Phoca vitulina) with a review of methods applicable to carnivores. NAMMCO Sci. Publ. 8:245-264. http://dx.doi.org/10.7557/3.2688

Lockyer C, Hohn AA, Hobbs R and Stewart REA (2016) Report of the workshop on age estimation in beluga. Beaufort, North Caroline, US, 5-9 December 2011. NAMMCO Sci. Publ. Vol 10. http://dx.dx.doi.org/10.7557/3.3731

Lord K (1959) The lens as an indicator of age in cottontail rabbits. J. Wildl. Manage. 23:358-360. http://dx.doi.org/10.2307/3796900

Lubetkin S and Zeh J (2006) Deriving age-length relationships for bowhead whales (Balaena mysticetus) using a synthesis of age estimation techniques (SC/58/BRG14). Submitted to the International Whaling Commission Scientific Committee, St. Kitts and Nevis, June 2006, 20 pp.

Lubetkin S, Zeh J, Rosa C and George J (2008) Age estimation for young bowhead whales (Balaena mysticetus) using annual baleen growth increments. Can. J. Zool. 86:525-538. https://doi.org/10.1139/Z08-028

Luque SP, Higdon JW and Ferguson SH (2007) Dentine deposition rates in belugas (Delphinapterus leucas): an analysis of the evidence. Aquat. Mamm. 33:241-245. https://doi.org/10.1578/AM.33.2.2007.241

Luque PL, Learmonth JA, Santos MB, Ieno E and Pierce GJ (2009a) Comparison of two histological techniques for age determination in small cetaceans. Mar. Mamm. Sci. 25:902-919. https://doi.org/10.1111/j.1748-7692.2009.00304.x

Luque P, Pierce G, Learmonth J, Santos M, Ieno E, Lopez A, Reid R, Rogan E, Gonzalez A, Boon J, Law R and Lockyer C (2009b) Dentinal anomalies in teeth of harbour porpoises (Phocoena phocoena) from Scottish waters: are they linked to sexual maturation and environmental events? J. Mar. Biol. Assoc. U.K. 89:893-902. https://doi.org/10.1017/S0025315409001866

Mackey BL (MS) (2004) Population dynamics and life history of harbour seals: the determination of phocid vital rates using dental annuli and mark recapture. [Ph.D. thesis]. University of Aberdeen, United Kingdom, 70-104.

Maeda H, Kawamoto T, and Kato H (2013) A study on the improvement of age estimation in common minke whales using the method of gelatinized extraction of earplug. NAMMCO Sci. Publ. Vol. 10. http://dx.doi.org/10.7557/3.2609

Mansfield AW and Fisher HD (1960) Age determination in the harbour seal (Phoca vitulina L.). Nature 186:92-93. http://dx.doi.org/10.1038/186092a0

Mansfield AW (1991) Accuracy of age-determination in the gray seal (Halichoerus grypus) of eastern Canada. Mar. Mamm. Sci. 7:44-49. https://doi.org/10.1111/j.1748-7692.1991.tb00549.x

Manzanilla S (1989) The 1982-1983 El Niño event recorded in dentinal growth layers in teeth of Peruvian dusky dolphins (Lagenorhynchus obscurus). Can. J. Zool. 67:2120-2125. https://doi.org/10.1139/z89-301

Marcoux M, Lesage V, Thiemann GW, Iverson SJ and Ferguson SH (2015) Age estimation of belugas (Delphinapterus leucas) using fatty acid composition: A promising method. Mar. Mamm. Sci. 31:944-962. https://doi.org/10.1111/mms.12212

Marmontel M, Nhea TJ, Kochman HI and Humphrey SR (1996) Age determination in manatees using growth-layer-group counts in bone. Mar. Mamm. Sci. 12:54-88. https://doi.org/10.1111/j.1748-7692.1996.tb00305.x

Marsh H (1980) Age determination of the dugong (Dugong dugon Muller) in northern Australia and its biological implications. In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Report of the International Whaling Commission (Special Issue 3), Cambridge, 181-201.

Marsh H (2009) Dugong: Dugong dugon. In: Perrin WF, Würsig B and Thewissen JGM (eds.); Encyclopaedia of Marine Mammals (Second Edition). Academic Press, London, 332-335. https://doi.org/10.1016/B978-0-12-373553-9.00080-8

Masaki Y (1979) Yearly change of the biological parameters for the Antarctic minke whale. Rep. Int. Whal. Comm. 29:375-395.

Masters PM, Bada JL and Zigler JS (1977) Aspartic-acid racemization in the human lens during aging and in cataract formation. Nature 268:71-73. http://dx.doi.org/10.1038/268071a0

Masters PM, Bada JL and Zigler JS (1978) Aspartic acid racemization in heavy molecular weight crystallins and water insoluble protein from normal human lenses and cataracts. Proc. Nat. Acad. Sci. 75:1204-1208. https://doi.org/10.1073/pnas.75.3.1204

Matthews CJD and Ferguson SH (2014) Validation of dentine deposition rates in beluga whales by interspecies cross dating of temporal δ13C trends in teeth. NAMMCO Sci. Publ. Vol. 10. http://dx.doi.org/10.7557/3.3196

McConkey S, Lalas C and Dawson S (2002) Moult and changes in body shape and pelage in known‐age male New Zealand sea lions (Phocarctos hookeri). N. Zeal. J. Zool. 29:53-61. https://doi.org/10.1080/03014223.2002.9518289

McLaren IA (1958a) The biology of the ringed seal (Phoca hispida Schreber) in the eastern Canadian Arctic. Bull. Fish. Res. Board Can. 118:1-97.

McLaren IA (1958b) Some aspects of growth and reproduction of the bearded seal (Erignathus barbatus (Erxleben)). J. Fish. Res. Board Can. 15:219-21. https://doi.org/10.1139/f58-012

McLeod S, Druhan J and Hacker R (2006) Estimating the age of kangaroos using eye lens weight. Wildl. Res. 33:25-28. https://doi.org/10.1071/WR04077

Medill S, Derocher AE, Stirling I, Lunn N and Moses RA (2009) Estimating cementum annuli width in polar bears: identifying sources of variation and error. J. Mammal. 90:1256-1264. https://doi.org/10.1644/08-MAMM-A-186.1

Medill S, Derocher AE, Stirling I and Lunn N (2010) Reconstructing the reproductive history of female polar bears using cementum patterns of premolar teeth. Polar Biol. 33:115-124. https://doi.org/10.1007/s00300-009-0689-z

Meyers RA, Bowen WD and Stobo WT (1997) Duration of pelage stages of grey seal (Halichoerus grypus) pups (97/11). Department of Fisheries and Oceans, Canadian Stock Assessment Secretariat, Research Document number 97/11. 10 pp.

Michaud R (2011) Presentation 24: Individual identification and life history of the St. Lawrence beluga. In: Hohn, A.A., Lockyer, C. and Acquarone, M. (eds.); Report of the workshop on age estimation in monodontids, Tampa, USA. NAMMCO Sci. Publ. Vol. 10. https://dx.doi.org/10.7557/3.3743

Mitchell J (1978) Incremental growth layers in the dentin of dugong incisors (Dugong dugong Müller) and their application to age-determination. Zool. J. Linn. Soc. 62:317-348. https://doi.org/10.1111/j.1096-3642.1978.tb01043.x

Mizroch SA, Herman LM, Straley JM, Glockner-Ferrari DA, Jurasz C, Darling J, Cerchio C, Gabriele CM, Salden DR and von Ziegesar O (2004) Estimating the adult survival rate of central north pacific humpback whales (Megaptera novaeangliae). J. Mammal. 85:963–972. https://doi.org/10.1644/BOS-123

Monaghan P (2010) Telomeres and life histories: the long and the short of it. Annals of the New York Academy of Sciences 1206:130-142. https://doi.org/10.1111/j.1749-6632.2010.05705.x

Morris P (1972) A review of mammalian age determination methods. Mamm. Rev. 2:69-104. https://doi.org/10.1111/j.1365-2907.1972.tb00160.x

Murphy S, Spradlin TR, Mackey B, McVee J, Androukaki E, Tounta E, Karamanlidis AA, Dendrinos P, Joseph E, Lockyer C and Matthiopoulos J (2012) Age estimation, growth and age-related mortality of Mediterranean monk seals (Monachus monachus). Endanger. Species Res. 16:149-163. https://doi.org/10.3354/esr00392

Murphy S, Perrott M, McVee J, Read FL and Stockin KA (2014) Deposition of growth layer groups in dentine tissue of captive common dolphins (Delphinus delphis). NAMMCO Sci. Publ. Vol. 10. https://dx.doi.org/10.7557/3.3017

Myrick AC (1980) Examination of layered tissues of odontocetes for age determination using polarized light microscopy. In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Report of the International Whaling Commission (Special Issue 3), Cambridge, 105-112.

Myrick AC (1988) Is tissue resorption and replacement in permanent teeth of mammals caused by stress-induced hypocalcemia? In: Davidovitch Z (ed.); The biological mechanisms of tooth eruption and root resorption. EBSCO Media, Birmingham, Alabama, 379-389.

Myrick AC (1991) Some new and potential uses of the dental layers in studying delphinid populations. In: Pryor K and Norris KS (eds.); Dolphin societies: discoveries and puzzles. University of California Press, Berkeley and Los Angeles, 251-279.

Myrick AC and Cornell LH (1990) Calibrating dental layers in captive bottlenose dolphins from serial tetracycline labels and tooth extractions. In: Leatherwood S and Reeves RR (eds.); The bottlenose dolphin. Academic Press, San Diego, 587-608. https://doi.org/10.1016/B978-0-12-440280-5.50038-X

Myrick AC, Hohn AA, Sloan PA, Kimura M and Stanley DD (1983) Estimating age of spotted and spinner dolphins (Stenella attenuata and Stenella longirostris) from teeth (NOAA-TM-NMFS-SWFC-30). U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Center, 17 pp.

Myrick A, Shallenberger E, Kang I and MacKay D (1984) Calibration of dental layers in seven captive Hawaiian spinner dolphins (Stenella longirostris) based on tetracycline labelling. U S Fish. Wildl. Serv. Fish. Bull. 82:207-225.

Myrick AC, Hohn AA, Barlow J and Sloan PA (1986) Reproductive biology of female spotted dolphins (Stenella attenuate) from the eastern tropical Pacific. Fish. Bull. 84:247-259.

Myrick A, Yochem P and Cornell L (1988) Toward calibrating dentinal layers in captive killer whales by use of tetracycline labels. Rit Fiskideildar 11:285-296.

Nakagawa S, Gemmell NJ and Burke T (2004) Measuring vertebrate telomeres: applications and limitations. Mol. Ecol. 13:2523-2533. https://doi.org/10.1111/j.1365-294X.2004.02291.x

NAMMCO (2013) Annex 4. Report of the NAMMCO Scientific Workshop on Age Estimation 2, Beaufort (summary only). NAMMCO Annual report 2012 541-548.

Nerini MK (1983) Age determination of fin whales (Balaenoptera physalus) based upon aspartic acid racemization in the lens nucleus. Rep. Int. Whal. Comm. 33:447-448.

Neve PB (MS) (1995) Narwhal (Monodon monoceros L.) in West Greenland. University of Copenhagen, Denmark, 29 pp.

Nielsen HG (1972) Age determination of the harbour porpoise (Phocoean phocoena L.) (Cetacea). Vidensk. Medd. Dan. Nat. For. 135:61-84.

Nielsen NH, Garde E, Heide-Jørgensen MP, Lockyer CH, Ditlevsen S, Òlasfsdóttir D. and Hansen SH (2013) Application of a novel method for age estimation of a baleen whale and a porpoise. Mar. Mamm. Sci. http://dx.doi.org/10.1111/j.1748-7692.2012.00588.x

Nielsen HN, Víkingsson GA, Hansen SH, Ditlevsen S and Heide-Jørgensen MP (2017) Two techniques of age estimation in cetaceans: GLGs in teeth and earplugs, and measuring the AAR rate in eye lens nucleus. NAMMCO Sci. Publ. Vol. 10. https://dx.doi.org/10.7557/3.4184

Nishiwaki M (1950) Determination of the age of Antarctic blue and fin whales by the colour changes in crystalline lens. Sci. Rep. Whal. Res. Inst. Tokyo 4:115-161.

Nishiwaki M (1958) Age study of sperm whale based on reading of tooth laminations. Sci. Rep. Whal. Res. Inst. Tokyo 13:135-153.

Nishiwaki M and Yagi T (1953) On the age and the growth of teeth in a dolphin (Prodelphinus cazruleoalbus). Sci. Rep. Whal. Res. Inst. Tokyo 8:133-146.

Nishiwaki M, Ohsumi S and Kasuya T (1961) Age characteristics in the sperm whale mandible. Nor. Hvalfangst. Sandefjord 50:499-507.

Norgaard N and Larsen BH (1991) Age Determination of harbour seals (Phoca vitulina) by cementum growth layers x-ray of teeth and body length. Dan. Rev. Game Biol. 14:17-32.

Odell DK (1977) Age determination and biology of the manatee. Report submitted to U.S. Fish and Wildl. Serv., Contract number 14-16-008-930, 104 pp.

Odendaal PN, Bester MN, van der Merwe M and Oosthuizen WH (2002) Seasonal changes in the ovarian structure of the Cape fur seal (Arctocephalus pusillus pusillus). Austr. J. Zool. 50:491-506. https://doi.org/10.1071/ZO01016

Ogden JA, Conlogue GJ and Rhodin AGJ (1981) Roentgenographic indicators of skeletal maturity in marine mammals (Cetacea). Skelet. Radiol. 7:119-123. https://doi.org/10.1007/BF00347376

Ognetev G (1981) Studies on the ecology and the taxonomy of the white whale (Delphinapterus leucas Pall. 1776) inhabiting the Soviet Arctic. Rep. Int. Whal. Comm. 31:515-520.

Ohsumi S (1979) Interspecies relationships among some biological parameters in cetaceans and estimation of the natural mortality coefficient of the southern hemisphere minke whale. Rep. Int. Whal. Comm. 29:397-406.

Olsen E and Sunde J (2002) Age determination of minke whales (Balaenoptera acutorostrata) using the aspartic acid racemization technique. Sarsia 87:1-8. https://doi.org/10.1080/003648202753631686

Olsen MT, Robbins J, Bérubé M, Rew MB and Palsbøll PJ (2014) Utility of telomere length measurements for age determination of humpback whales. NAMMCO Sci. Publ. Vol. 10. https://dx.doi.org/10.7557/3.3194

Oosthuizen WH (1997) Evaluation of an effective method to estimate age of cape fur seals using ground tooth sections. Mar. Mamm. Sci. 13:683-693. https://doi.org/10.1111/j.1748-7692.1997.tb00091.x

Owen R (1845) Odontography; or, A Treatise on the Comparative Anatomy of Teeth, their physical relations, mode of development and microscopic structure in the Vertebrate Animals. Hippolyte Bailliere, London. 655 pp.

Pastukhov VD (1969) Onset of sexual maturity in female Baikal seals. In: Arsen'ev VA, Zenokovich BA and Chapskii KK (eds.); Marine Mammals. Nauka, Moscow, 127-135. In Russian.

Perrin W and Myrick A (1980) Age determination of toothed whales and sirenians. Report of the International Whaling Commission, Cambridge. 229 pp.

Petersen S and Born EW (1982) Age-determination of the Atlantic walrus (Odobenus rosmarus rosmarus Linnaeus), by means of mandibular growth layers. Int. J. Mamm. Biol. 47:55-62.

Pierce KV and Kajimura H (1980) Acid etching and highlighting for defining growth layers in cetacean teeth. In: Perrin WF and Myrick AC (eds.); Age determination of toothed whales and sirenians. Report of the International Whaling Commission (Special Issue 3), Cambridge, 99-103.

Pinedo MC and Hohn AA (2000) Growth layer patterns in teeth from the Franciscana (Ponotoporia blainvillei): developing a model for precision in age estimation. Mar. Mamm. Sci. 16:1-27. https://doi.org/10.1111/j.1748-7692.2000.tb00901.x

Pleskach K, Hoang W, Chu M, Halldorson T, Loseto L, Ferguson SH and Tomy GT (2016) Use of mass spectrometry to measure aspartic acid racemization for ageing beluga whales. Mar. Mamm. Sci. 32:1370-1380. https://doi.org/10.1111/mms.12347

Purves P (1955) The wax plug in the external auditory meatus of the mysticeti. Discov. Rep. 27:293-302.

Rice D and Wolman A (1971) The life history and ecology of the gray whale (Eschrichtius robustus). Special Publication 3, The American Society of Mammalogists, 142 pp.

Roe H (1967) Seasonal formation of laminae in the ear plug of the fin whale. Discov. Rep. 35:1-30.

Rosa C, Zeh J, Craig GJ, Botta O, Zauscher M, Bada J and O'Hara TM (2012) Age estimates based on aspartic acid racemization for bowhead whales (Balaena mysticetus) harvested in 1998-2000 and the relationship between racemization rate and body temperature. Mar. Mamm. Sci. 29:424–445. http://dx.doi.org/10.1111/j.1748-7692.2012.00593.x

Ruud J (1940) The surface structure of the baleen plates as a possible clue to age in whales. Hval. Skrift. Oslo 28:1-24.

Scheffer VB (1950) Growth layers on the teeth of pinnipedia as an indication of age. Science 112:309-311. https://doi.org/10.1126/science.112.2907.309-a

Scoresby W (1820) An account of the Arctic regions, with a history and description of the northern whale-fishery. Archibald Constable, Edinburgh, 574 pp. https://doi.org/10.5962/bhl.title.49370

Sergeant DE (1959) Age determination in odontocete whales from dentinal growth layers. Norsk Hvalf. 48:272-288.

Sergeant DE (1971) On permissible rates of exploitation of monodontids. Rep. Int. Whal. Comm. 31:583-588.

Sergeant DE (1973) Biology of white whales (Delphinapterus leucas) in western Hudson Bay. J. Fish. Res. Board Can. 30:1065-1090. https://doi.org/10.1139/f73-178

Sergeant DE, Caldwell DK and Caldwell MC (1973) Age, growth, and maturity of bottlenose dolphin (Tursiops truncatus) from northeast Florida. J. Fish. Res. Board Can. 30:1009-1011. https://doi.org/10.1139/f73-165

Sheehan DC and Hrapchak BB (1980) Theory and practice of histotechnology. Mosby, St. Louis. 480 pp.

Sigurjónsson J (1989) Studies on age and reproduction in minke whales (Balaenoptera acutorostrata) in Icelandic waters. Rep. Int. Whal. Comm. 38:327-333.

Slooten E (1991) Age, growth and reproduction in Hector's dolphins. Can. J. Zool. 69:1689-1700. https://doi.org/10.1139/z91-234

Smith T (1973) Population dynamics of the ringed seal in the Canadian eastern Arctic. Bull. Fish. Res. Board Can. 181:1-55.

Snedecor GW and Cochran WG (1980) Statistical methods. The Iowa State University Press, Ames, 570 pp.

Stewart BE (2012) A Technical Report on Methods for Tooth Preparation and Age Estimates of Beluga (Delphinapterus leucas). Can. Tech. Rep. Fish. Aquat. Sci. 3020: 85 pp.

Stewart BE (2017) Age estimates of narwhal (Monodon monoceros) derived from growth-layer groups (GLGs) in the dentine of embedded tusks – Developmental constraints and best practices. NAMMCO/JCNB Joint Working Group on narwhals and belugas. Copenhagen, Denmark. March 2017. Work Package 11. 38 pp.

Stewart BE and Stewart REA (2014) The biology behind the counts: tooth development related to age estimation in beluga (Delphinapterus leucas). NAMMCO Sci. Publ. Vol. 10. https://dx.doi.org/10.7557/3.3195

Stewart REA (MS) (1983) Behavioral and energetic aspects of reproductive effort in harp seals (Phoca groenlandicus). [Ph.D. thesis].University of Guelph, Canada, 231 pp.

Stewart REA (1994) Size-at-age relationships as discriminators of white whale (Delphinapterus leucas) stocks in the eastern Canadian Arctic. Medd. Grønl. Biosci. 39:217-225.

Stewart REA and Lavigne DM (1979) Age determination in harp seals. International Workshop on Biology and Management of Northwest Atlantic Harp Seals. Guelph, Ontario, Canada. 3-6 December 1979. Working Paper HS/WP 10. 8 pp.

Stewart REA and Lavigne DM (1980) Neonatal growth of northwest Atlantic harp seals (Pagophilus groenlandicus). J. Mammal. 61:670-680. https://doi.org/10.2307/1380312

Stewart REA and Stewart BE (1987) Dental ontogeny of harp seals (Phoca groenlandica). Can. J. Zool. 65:1425-1434. https://doi.org/10.1139/z87-225 - https://doi.org/10.1139/z87-121

Stewart REA and Stewart BE (2005) Comparison of between-tooth age estimates of Atlantic walrus (Odobenus rosmarus rosmarus). Mar. Mamm. Sci. 21:346-354. https://doi.org/10.1111/j.1748-7692.2005.tb01236.x

Stewart REA, Stewart BE, Stirling I and Street E (1996) Counts of growth layer groups in cementum and dentine in ringed seals (Phoca hispida). Mar. Mamm. Sci. 12:383-401. https://doi.org/10.1111/j.1748-7692.1996.tb00591.x

Stewart R, Campana S, Jones C and Stewart B (2006) Bomb radiocarbon dating calibrates beluga (Delphinapterus leucas) age estimates. Can. J. Zool. 84:1840-1852. https://doi.org/10.1139/z06-182

Suydam RS (MS) (2009) Age, growth, reproduction and movements of beluga whales (Delphinapterus leucas) from the eastern Chukchi Sea. [Ph.D. thesis]. University of Washington, USA, 152 pp.

Sweeny MM, Price JM, Jones GS, French TW, Early GA and Moore MJ (2005) Spondylitic changes in long-finned pilot whales (Globicephala melas) stranded on Cape Cod, Massachusetts, USA, between 1982 and 2000. J. Wildl. Dis. 41:717-727. https://doi.org/10.7589/0090-3558-41.4.717

Sydney NV and Monteiro-Filho EL (2011) Efficiency of wear and decalcification technique for estimating the age of estuarine dolphin (Sotalia guianensis). J. Biosci. 36:117-121. https://doi.org/10.1007/s12038-011-9005-5

Tsuji A, Ishiko A, Takasaki T and Ikeda N (2002) Estimating age of humans based on telomere shortening. Forensic Sci. Int. 126:197-199. https://doi.org/10.1016/S0379-0738(02)00086-5

Vleck CM, Haussmann MF and Vleck D (2003) The natural history of telomeres: tools for aging animals and exploring the aging process. Exp. Gerontol. 38:791-795. https://doi.org/10.1016/S0531-5565(03)00110-4

Vos DJ (MS) (2003) Cook Inlet beluga age and growth. [M.Sc. thesis]. University of Alaska, Anchorage, USA, 69 pp.

Wainwright KL and Walker RS (1988) A method for preparing beluga (white whale), Delphinapterus leucas, teeth for ageing. Department of Fisheries and Oceans. Canadian Manuscript Report of Fisheries and Aquatic Sciences 1967, 15 pp.

Waugh DA, Suydam RS, Ortiz JD, Thewissen JGM (2018) Validation of Growth Layer Group (GLG) depositional rate using daily incremental growth lines in the dentin of beluga (Delphinapterus leucas (Pallas, 1776)) teeth. PLoS ONE 13:e0190498. https://doi.org/10.1371/journal.pone.0190498

Weidman CR and Jones GA (1993) A shell-derived time history of bomb C-14 on Georges Bank and its Labrador Sea implications. J. Geophys. Res.-Oceans 98:14577-14588. https://doi.org/10.1029/93JC00785

Worbes M and Junk WJ (1989) Dating tropical trees by means of C-14 from bomb tests. Ecol. 70:503-507. https://doi.org/10.2307/1937554

Yagi T, Nishiwaki M and Nakajima M (1963) A preliminary study on method of time marking with lead-salt and tetracycline on the teeth of northern fur seal. Sci. Rep. Whal. Res. Inst. Tokyo 17:191-195.

Yalman RG, Bruegemann W, Baker PT and Garn SM (1959) Volumetric determination of calcium in presence of phosphate. Anal. Chem. 31:1230-1233. https://doi.org/10.1021/ac60151a001

Young BG, Higdon JW, Ferguson SH (2011) Killer whale (Orcinus orca) photo-identification in the eastern Canadian Arctic. Polar Res. 30:7203. 10.3402/polar.v30i0.7203. https://doi.org/10.3402/polar.v30i0.7203

Zimushko VV and Ivashin MV (1980) Some results of Soviet investigations and whaling of grey whales (Eschrichtius robustus Lilljeborg 1961). Rep. Int. Whal. Comm. 30:237-246.




How to Cite

Read, F. L., Hohn, A. A., & Lockyer, C. H. (2018). A review of age estimation methods in marine mammals with special reference to monodontids. NAMMCO Scientific Publications, 10. https://doi.org/10.7557/3.4474