Journal of Mammalian Evolution

, Volume 20, Issue 4, pp 337–355 | Cite as

Sexual Dimorphism and Inter-Generic Variation in Proboscidean Tusks: Multivariate Assessment of American Mastodons (Mammut americanum) and Extant African Elephants

  • Kathlyn M. SmithEmail author
  • Daniel C. Fisher
Original Paper


Characteristics of social structure, mating strategies, and parental investment can be inferred for mammalian species based on degree of sexual dimorphism, especially when males are substantially larger than females. American mastodons (Mammut americanum) and extant African elephants (Loxodonta africana, Loxodonta cyclotis) both exhibit marked dimorphism in tusk size. To evaluate the hypothesis that this dimorphism might be indicative of similar, and possibly conserved, behavioral patterns in each lineage, we undertook a detailed evaluation of the pattern of tusk growth in these two genera. Separate discriminant function analyses (DFA) of 21 adult mastodon tusks of inferred sex and 48 adult elephant tusks of known sex show that patterns of ontogenetic change in tusk circumference, regardless of genus, effectively discriminate between sexes. Canonical variates analysis (CVA) of tusks from male and female mastodons and male and female elephants shows that male tusks in both genera are larger than female tusks across all measurements, especially for maximum tusk circumference and pulp cavity depth. CVA’s emphasis of inter-group differences in tusk morphology also shows that mastodon tusks are more robust than elephant tusks. Overall, this study illustrates that there is a characteristic male and a characteristic female tusk form shared by elephants and mastodons. This shows that elephants and mastodons display a shared syndrome of traits beyond sex-linked differences in tusk size, supporting the hypothesis that mastodons exhibited behaviors similar to those we observe today in African elephants.


Tusk Sexual dimorphism Morphology Mammut americanum Loxodonta Behavior 



We thank W. Stanley and J. Phelps at the Field Museum of Natural History, Chicago, IL, L. Gordon and D. Schmidt at the National Museum of Natural History, Washington, D.C., and A. Fleming and E. Westwig at the American Museum of Natural History, New York, NY, for access to collections and assistance moving and measuring tusks; J. Johnson for his invaluable assistance during the data-collection portion of this project; C. Badgley, R. Bebej, P. Gingerich,. D. Fox, and one anonymous reviewer for comments and suggestions that improved this manuscript greatly; and A. Rountrey, W. Sanders, A. Wood, and M. Zelditch for contributions throughout this study. Funding was provided by a Scott Turner Award from the University of Michigan, Department of Earth and Environmental Sciences (KMS) and National Science Foundation grants EAR 9628063 and 054095 (DCF).


  1. Allen JA (1877) The influence of physical conditions in the genesis of species. Radical Rev 1:108-140Google Scholar
  2. Averianov AO (1996) Sexual dimorphism in the mammoth skull, teeth, and long bones. In: Shoshani J, Tassy P (eds) The Proboscidea: Evolution and Palaeoecology of Elephants and their Relatives. Oxford University Press, Oxford, pp 260-267Google Scholar
  3. Badyaev AV (2002) Growing apart: an ontogenetic perspective on the evolution of sexual size dimorphism. Trends Ecol Evol 17(8):369-378CrossRefGoogle Scholar
  4. Berger J, Dulamtseren S, Calin S, Enkkhbileg D, Lichtman P, Namshir S, Wingard G, Reading R (2001) Back-casing sociality in extinct species: new perspectives using mass death assemblages and sex ratios. Proc R Soc Lond B 268(1463):131-139CrossRefGoogle Scholar
  5. Bininda-Edmonds OR, Gittleman JL, Purvis A (1999) Building large trees by combining phylogenetic information: a complete phylogeny of the extant Carnivora (Mammalia). Biol Rev 74:143-175CrossRefGoogle Scholar
  6. Campbell NA, Atchley WR (1981) The geometry of canonical variates analysis. Syst Zool 30(3):268-280CrossRefGoogle Scholar
  7. Cerling TC, Harris JM, Leakey MG (1999) Browsing and grazing in elephants: the isotope record of modern and fossils proboscideans. Oecologia 120:364-374CrossRefGoogle Scholar
  8. Charnov EL, Schaffer WM (1973) Life-history consequences of natural selection: Cole’s result revisited. Am Nat 107:791-793CrossRefGoogle Scholar
  9. Clutton-Brock TH (1994) The costs of sex. In: Short RV, Balaban E (eds) The Differences Between the Sexes. Cambridge University Press, Cambridge, pp 347-362Google Scholar
  10. Darwin CR (1871) The Descent of Man, and Selection in Relation to Sex. Appleton, New YorkGoogle Scholar
  11. Debruyne R (2005) A case study of apparent conflict between molecular phylogenies: the interrelationships of African elephants. Cladistics 21:31–50Google Scholar
  12. Eberhardt LL (2002) A paradigm for population analysis of long-lived vertebrates. Ecology 83:2841-2854CrossRefGoogle Scholar
  13. Eisenberg JL, McKay GM, Jainudeen MR (1971) Reproductive behavior of the Asiatic elephant (Elephas maximus maximus L.). Behaviour 38:193-225CrossRefPubMedGoogle Scholar
  14. Elder WH (1970) Morphometry of elephant tusks. Zool Afr 5:43-159Google Scholar
  15. Fisher DC (1990) Age, sex, and season of death of the Grandville mastodon. Mich Archaeol 36:141-160Google Scholar
  16. _____ (1996) Extinction of proboscideans in North America. In: Shoshani J, Tassy P (eds) The Proboscidea: Evolution and Palaeoecology of Elephants and their Relatives. Oxford University Press, Oxford, pp 121-135Google Scholar
  17. _____ (2008) Taphonomic analysis of the Hyde Park mastodon. In: Allmon WD, Nester PL, Chiment JJ (eds) Mastodon Paleobiology, Taphonomy, and Paleoenvironment in the Late Pleistocene of New York State: Studies on the Hyde Park, Chemung, and Java Sites. Palaeontographica Americana 61:197-290Google Scholar
  18. _____ (2009) Paleobiology and extinction of proboscideans in the Great Lakes region of North America. In: Haynes G (ed) American Megafaunal Extinctions at the End of the Pleistocene. Springer Science, New York, pp 55-75CrossRefGoogle Scholar
  19. Fisher DC, Beld SG, Rountrey AN (2008) Tusk record of the North Java mastodon. In: Allmon WD, Nester PL, Chiment JJ (eds) Mastodon Paleobiology, Taphonomy, and Paleoenvironment in the Late Pleistocene of New York State: Studies on the Hyde Park, Chemung, and Java Sites. Palaeontographica Americana 61:417-463Google Scholar
  20. Fisher DC, Fox DL (2003) Season of death and terminal growth histories of Hiscock mastodons. In: Laub RS (ed) The Hiscock Site: Late Pleistocene and Holocene Paleoecology and Archaeology of Western New York State. Bull Buffalo Soc of Nat Sci 37:83-101Google Scholar
  21. _____ (2007) Life history and unilateral loss of molar function in the Cohoes mastodon: a case study in nutritional stress? J Vertebr Paleontol 27 (Suppl to 3):74A-75AGoogle Scholar
  22. Gheerbrant E, Sudre J, Tassy P, Amaghzaz M, Bouya B, Iarochene M (2005) Nouvelles données sur Phosphatherium escuilliei (Mammalia, Proboscidea) de l’Éocène inférieur du Maroc, apports à la phylogénie des Proboscidea et des ongulés lophodontes. Geodiversitas 27(2):239-333Google Scholar
  23. Gheerbrant E, Tassy P (2009) L’origine et l’évolution des éléphants. CR Paleovol 8:281-294CrossRefGoogle Scholar
  24. Gingerich PD (1981) Variation, sexual dimorphism, and social structure in the early Eocene horse Hyracotherium. Paleobiology 7(4):443-455Google Scholar
  25. _____ (2000) Arithmetic or geometric normality of biological variation: an empirical test of theory. J Theor Biol 204:201-221CrossRefPubMedGoogle Scholar
  26. Gittleman JL, Van Valkenburgh B (1997) Sexual dimorphism in the canines and skulls of carnivores: effects of size, phylogeny, and behavioural ecology. J Zool 242:97-117CrossRefGoogle Scholar
  27. Groves CP, Grubb P (2000) Do Loxodonta cyclotis and L. africana interbreed? Elephant 2(4):3-4Google Scholar
  28. Grubb P, Groves CP, Dudley JP, Shoshani J (2000) Living African elephants belong to two species: Loxodonta africana (Blumenbach, 1797) and Loxodonta cyclotis (Matschie, 1900). Elephant 2(4):1-3Google Scholar
  29. Hammer Ø, Harper DAT, Ryan PD (2001) PAST: Paleontological Statistics software package for education and data analysis. Palaeontol Electron 4:1-9Google Scholar
  30. Hanks J (1972) Growth of the African elephant (Loxodonta africana). East Afr Wildl J 10:251-272CrossRefGoogle Scholar
  31. Haynes G (1991) Mammoths, Mastodonts, and Elephants: Biology, Behavior, and the Fossil Record. Cambridge University Press, CambridgeGoogle Scholar
  32. Holman JA, Fisher DC, Kapp RO (1986) Recent discoveries of fossil vertebrates in the lower peninsula of Michigan. Michigan Academician 28:431–463Google Scholar
  33. Huttunen K, Goelich UB (2002) A partial skeleton of Prodeinotherium bavaricum (Proboscidea, Mammalia) from the middle Miocene of Unterzolling (Upper Freshwater Molasse, Germany). Geobios 35:489–514CrossRefGoogle Scholar
  34. Johnson MB, Clifford SL, Goossens B, Nyakanna S, Curran B, White LJT, Wickings EJ, Bruford MW (2007) Complex phylogeographic history of central African forest elephants and its implications for taxonomy. BMC Evol Biol 7:244–257Google Scholar
  35. Jones ME, Cockburn AA, Hamede R, Hawkins C, Heserman H, Lachich S, Mann D, McCallum H, Pemberton D (2008) Life-history change in disease-ravaged Tasmanian devil populations. Proc Natl Acad Sci USA 105:10023-10027PubMedCentralCrossRefPubMedGoogle Scholar
  36. Joshi R, Singh R, Pushola R, Negi MS (2009) Reproductive behaviour of wild Asian Elephants Elephas maximus in the Rajaji National Park, North-West India. Researcher 1:76-84Google Scholar
  37. Koch PL, Tuross N, Fogel ML (1997) The effects of sample treatment and diagenesis on the isotopic integrity of carbonate in biogenic hydroxylapatite. J Archaeol Sci 24:417-429CrossRefGoogle Scholar
  38. Lee PC, Moss CJ (1986) Early maternal investment in male and female African elephant calves. Behav Ecol Sociobiol 18:353-361CrossRefGoogle Scholar
  39. ____ (1995) Statural growth in known-age African elephants (Loxodonta africana). J Zool 236:29-41Google Scholar
  40. ____ (1999) The social context for learning and behavioural development among wild African elephants. In: Box HO, Gibson KR (eds) Mammalian Social Learning. Cambridge University Press, Cambridge, pp 102-125Google Scholar
  41. Lister A (1996) Sexual dimorphism in the mammoth pelvis: an aid to gender determination. In: Shoshani J, Tassy P (eds) The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives. Oxford University Press, Oxford, pp 254-259Google Scholar
  42. Luckett WP (1996) Ontogenetic evidence for incisor homologies in proboscideans. In: Shoshani J, Tassy P (eds) The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives. Oxford University Press, Oxford, pp 26-31Google Scholar
  43. Madden CT (1986) Stegomastodon associated with Mammuthus in Arizona during the Quaternary. Quaternary Res 26:266-271CrossRefGoogle Scholar
  44. Maglio VJ (1973) Origin and evolution of the Elephantidae. Trans Am Philos Soc 63:1-149CrossRefGoogle Scholar
  45. Mihlbachler MC (2003) Demography of late Miocene rhinoceroses (Teleoceras proterum and Aphelops malacorhinus) from Florida: linking mortality and sociality in fossil assemblages. Paleobiology 29:412-428CrossRefGoogle Scholar
  46. Moss CJ (1988) Elephant Memories: Thirteen Years in the Life of an Elephant Family. William Morrow, New YorkGoogle Scholar
  47. Noubhani A, Hautier L, Jaeger J, Mahboubi M, Tabuce R (2008) Dental and cranial variability of Numidotherium koholense (Mammalia, Proboscidea) from El Kohol, Eocene, Algeria. Geobios 41:515-531CrossRefGoogle Scholar
  48. Pilgram T, Western D (1986) Inferring the sex and age of African elephants from tusk measurements. Biol Conserv 36:39-52CrossRefGoogle Scholar
  49. Poole JH (1987) Rutting behavior in African elephants: the phenomenon of musth. Behaviour 102:283-316CrossRefGoogle Scholar
  50. _____ (1994) Sex differences in the behavior of African elephants, In: Short RV, Balaban E (eds) The Differences Between the Sexes. Cambridge University Press, Cambridge, pp 331-346Google Scholar
  51. Ralls K (1976) Mammals in which females are larger than males. Quart Rev Biol 51:245-276CrossRefPubMedGoogle Scholar
  52. _____ (1977) Sexual dimorphism in mammals: avian models and unanswered questions. Am Nat 11:917-938CrossRefGoogle Scholar
  53. Reznick DA, Bryga H, Endler JA (1990) Experimentally induced life-history evolution in a natural population. Nature 346:357-359CrossRefGoogle Scholar
  54. Reynolds JD, Harvey PH (1994) Sexual selection and the evolution of sex differences. In: Short RV, Balaban E (eds) The Differences Between the Sexes. Cambridge University Press, Cambridge, pp 53-70Google Scholar
  55. Roca AL, Georgiadis N, Pecon-Slattery J, O’Brien SJ (2001) Genetic evidence for two species of elephant in Africa. Science 293:1473-1476CrossRefPubMedGoogle Scholar
  56. Shoshani J (1992) Comparing the living elephants, In: Shoshani J (ed) Elephants: Majestic Creatures of the Wild. Rodale Press, Pennsylvania, pp 36-51Google Scholar
  57. Smith KM, Fisher DC (2008) Tusk growth record of a female American mastodon (Mammut americanum) from southwestern New York state. J Vertebr Paleontol 28 (suppl to No 3):144AGoogle Scholar
  58. _____ (2011) Sexual dimorphism in structures showing indeterminate growth: tusks of American mastodons (Mammut americanum). Paleobiology 37:175-194Google Scholar
  59. Spain AV, Heinsohn GE, Marsh H, Correll RL (1976) Sexual dimorphism and other sources of variation in a sample of dugong skulls from North Queensland. Aus Zool 24:491-497CrossRefGoogle Scholar
  60. Sukumar R (1989) The Asian Elephant. Cambridge University Press, CambridgeGoogle Scholar
  61. _____ (2006) A brief review of the status, distribution, and biology of wild Asian elephants. The Zool Soc Lond 40:1-8Google Scholar
  62. Sukumar R, Joshi NV, Krishnamurthy V (1988) Growth in the Asian elephant. Proc Indian Acad Sci (Anim Sci) 97:561-571CrossRefGoogle Scholar
  63. Tassy P (1996) Growth and sexual dimorphism among Miocene elephantoids: the example of Gomphotherium augustidens. In: Shoshani J, Tassy P (eds) The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives. Oxford University Press, Oxford, pp 92-100Google Scholar
  64. van den Bergh GD (1999) The Late Neogene elephantoid-bearing faunas of Indonesia and their palaeozoogeographic implications: a study of the terrestrial faunal succession of Sulawesi, Flores and Java, including evidence for early hominid dispersal east of Wallace's Line. Scripta Geologica 117:1-419Google Scholar
  65. Vanpe C, Kjellander P, Galan M, Cosson J, Aulagnier S, Liberg O, Hewison AJM (2009) Mating system, sexual dimorphism, and the opportunity for sexual selection in a territorial ungulate. Behav Ecol 19:309-316CrossRefGoogle Scholar
  66. Vidya TNC, Sukumar R (2005) Social organization of the Asian elephant (Elephas maximus) in southern India inferred from microsatellite DNA. J Ethol 23:205-210CrossRefGoogle Scholar
  67. Weckerly FW (1998) Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals. J Mammal 79:33-52CrossRefGoogle Scholar
  68. Wilson DE, Reeder DM (eds) (2005) Mammal Species of the World: A Taxonomic and Geographic Reference (3rd edition). John Hopkins University Press, BaltimoreGoogle Scholar
  69. Zalmout I, Gingerich P (2008) Sexual dimorphism in the bony pelvis of sea cows from the Eocene of Egypt (Mammalia, Sirenia). J Vertebr Paleontol 28 (suppl to no 3):164AGoogle Scholar
  70. Zelditch ML, Swiderski DL, Sheets HD, Fink WL (2004) Geometric Morphometrics for Biologists: A Primer. Elsevier Academic Press, New YorkGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Department of Geology & Geography and Georgia Southern University MuseumGeorgia Southern UniversityStatesboroUSA
  2. 2.Museum of Paleontology and Department of Earth & Environmental SciencesUniversity of MichiganAnn ArborUSA

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