• Renan Lima Laboratório de Ecologia e Conservação da Megafauna Marinha, Instituto de Oceanografia, Universidade Federal do Rio Grande Programa de Pós-Graduação em Oceanografia Biológica, Instituto de Oceanografia, Universidade Federal do Rio Grande
  • Julieta Cebuhar Laboratório de Ecologia e Conservação da Megafauna Marinha, Instituto de Oceanografia, Universidade Federal do Rio Grande Programa de Pós-Graduação em Oceanografia Biológica, Instituto de Oceanografia, Universidade Federal do Rio Grande
  • Leonardo Martí Núcleo de Educação e Monitoramento Ambiental
  • Valentina Franco-Trecu Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República
  • Larissa Oliveira Laboratório de Ecologia de Mamíferos, Universidade do Vale do Rio dos Sinos Grupo de Estudos de Mamíferos Aquáticos do Rio Grande do Sul
  • Silvina Botta



Otaria flavescens, otariids, pinnipeds, pregnancy, twinning


We report the first known occurrence of South American sea lion (Otaria flavescens) twins for the South American coast. In January 2021 a female pregnant with dizygotic male and female fetuses was found dead in southern Brazil. The timing of the stranding event suggests that the pregnancy was near-term. However, the total body length and weight of fetuses suggested poor development and growth, which could be due to the advanced age of the mother and/or poor nutrition of the individual during pregnancy. The female fetus was larger and heavier than the male and could have been implanted and developed earlier.


Bester, M. N., & Kerley G. I. H. 1983. Rearing of twin pups to weaning by subantarctic fur seal Arctocephalus tropicalis female. African Journal of Wildlife Research, 13(3), 86–87. DOI: 10520/AJA03794369_3399

Campagna, C., & Le Boeuf, B. J. 1988. Reproductive behaviour of southern sea lions. Behaviour, 104 (3-4), 233–261. DOI: 10.1163/156853988X00539

Cappozzo, H. L., & Perrin, W. F. 2009. South American Sea Lion: Otaria flavescens. In: B. Würsig, W. Perrin, & J. G. M. Thewissen (Eds.), Encyclopedia of marine mammals, 2nd ed. pp. 1076–1079 Academic Press, Cambridge.

Clutton-Brock, T. H. 2019. The evolution of parental care. Princeton University Press, Princeton: p. 352.

Condit, R., Beltran, R. S., Robinson, P. W., Crocker, D. E., & Costa, D. P. 2021. Birth timing after the long feeding migration in elephant seals. Marine Mammal Science. DOI: 10.1111/mms.12896

Doidge, D.W. 1987. Rearing of twin offspring to weaning in Antarctic fur seals, Arctocephalus gazella. In: Croxall, J. P. & Gentry, R. L. (Eds.). Status, biology, and ecology of fur seals. Proceedings of an International Symposium and Workshop, Cambridge, England, 23-27 April 1984: International Symposium and Workshop on the Biology of Fur Seals, Cambridge, 1984. Seattle, National Marine Fisheries Service, 107–111.

Dowell, S. A., Boren, L. J., Negro, S. S., Muller, C. G., Caudron, A. K., & Gemmell, N. J. 2008. Rearing two New Zealand fur seal (Arctocephalus forsteri) pups to weaning. Austrailian Journal of Zoology, 56(1), 33–39. DOI: 10.1071/ZO07063

Drago, M., Cardona, L., Franco-Trecu, V., Riet-Sapriza, F. G., Crespo, E. A., García, N., & Inchausti, P. 2021. Relationship between the female attendance pattern and pup growth rate in the South American sea lion (Carnivora). Scientia Marina, 85(2), 81–90. DOI: 10.3989/scimar.05128.008

Franco-Trecu, V. 2015. Tácticas comportamentales de forrajeo y apareamiento y dinámica poblacional de dos especies de otáridos simpátricas con tendencias poblacionales contrastantes. Doctoral thesis. Montevideo, Universidad de la República. p. 225.

Franco-Trecu, V., Tassino, B., & Soutullo, A. 2010. Allo-suckling in the South American fur seal (Arctocephalus australis) in Isla de Lobos, Uruguay: cost or benefit of living in a group? Ethology, Ecology and Evolution, 22(2), 143–150. DOI: 10.1080/03949371003707745.

Franco-Trecu, V., Costa-Urrutia, P., Schramm, Y., Tassino, B., & Inchausti, P. 2015. Tide line versus internal pools: mating systems and breeding success of South American sea lion males. Behavioral Ecology and Sociobiology, 69(12), 1985–1996. DOI: 10.1007/s00265-015-2010-1.

Gelatt, T. S., Davis, C. S., Siniff, D. B., & Strobeck, C. 2001. Molecular evidence for twinning in Weddell seals (Leptonychotes weddellii). Journal of Mammalogy, 82(2), 491–499. DOI: 10.1644/1545-1542(2001)082<0491:MEFTIW>2.0.CO;2.

Grandi, M. F., Dans, S. L., García, N. A., & Crespo, E. A. 2010. Growth and age at sexual maturity of South American sea lions. Mammalian Biology, 75(5), 427–436. DOI: 10.1016/j.mambio.2009.09.007.

Gutiérrez, J., Seguel, M., Saenz-Agudelo, P., Acosta-Jamett, G., & Verdugo, C. 2021. Genetic diversity and kinship relationships in one of the largest South American fur seals (Arctocephalus australis) populations of the Pacific Ocean. Ecology and Evolution, DOI: 10.1002/ece3.7683 (Epub ahead of print).

Haase, T. J. 2007. Suckling an additional pup to weaning in the New Zealand fur seal. Marine Mammal Science, 23(1), 176–183. DOI: 10.1111/j.1748-7692.2006.00078.x

Hamilton, J. E. 1939. A second report on the southern sea lion, Otaria byronia (de Blainville). University Press, Cambridge: p. 66.

Hoffman, J. I., & Forcada, J. 2009. Genetic analysis of twinning in Antarctic fur seals (Arctocephalus gazella). Journal of Mammalogy, 90(3), 621–628. DOI: 10.1644/08-MAMM-A-264R1.1

Ling, J. K. 1986. Twin foetuses from an Australian sea lion, Neophoca cinerea (Carnivora: Otariidae). Australian Mammalogy, 9, 9–60. DOI: 10.1071/AM86008

Machado, R., Oliveira, L. R., Ott, P. H., Denuncio, P., Haimovici, P., Haimovici, M., Cardoso, L. G., Danilewicz, Moreno, I. B., & Borges-Martins, M. 2018. Changes in the feeding ecology of South American sea lions on the southern Brazilian coast over the last two decades of excessive fishing exploration. Hydrobiologia, 819, 17–37. DOI: 10.1007/s10750-018-3618-8

Maniscalco, J. M., & Parker, P. 2009. A case of twinning and the care of two offspring of different age in Steller sea lions. Marine Mammal Science, 25(1), 206–213. DOI: 10.1111/j.1748-7692.2008.00247.x.

McMahon, C. R., & Hindell, M. A. 2003. Twinning in southern elephant seals: the implications of resource allocation by mothers. Wildlife Research, 30(1), 35–39. DOI: 10.1071/WR01069

Oftedal, O. T., Boness, D. J., & Tedman, R. A. 1987. The behavior, physiology, and anatomy of lactation in the pinnipedia. In: H. H. Genoways (Ed.). Current mammalogy. pp. 175–245. Springer, Berlin.

Payne, M. R. 1978. Population size and age determination in the Antarctic fur seal Arctocephalus gazella. Mammal Review, 8(1-2), 67–73. DOI: 10.1111/j.1365-2907.1978.tb00218.x.

Procksch, N., Grandi, M. F., Ott, P. H., Groch, K., Flores, P. A. C., Zagonel, M., Crespo, E. A., Machado, R., Pavez, G., Guimarães, M., Veronez, M., & de Oliveira L. R. 2020. The northernmost haulout site of South American sea lions and fur seals in the western South Atlantic. Scientific Reports, 10(1), 1–15. DOI: 10.1038/s41598-020-76755-2

Riedman, M. 1990. The pinnipeds: seals, sea lions, and walruses (Vol. 12). University of California Press, Berkeley: p. 439.

Rosas, F. C. W., Haimovici, M., & Pinedo, M. C. 1993. Age and growth of the South American sea lion, Otaria flavescens (Shaw, 1800), in Southern Brazil. Journal of Mammalogy, 74(1), 141–147. DOI: 10.2307/1381913.

Roulin, A. 2002. Why do lactating females nurse alien offspring? A review of hypotheses and empirical evidence. Animal Behaviour, 63(2), 201–208. DOI: 10.1006/anbe.2001.1895.

Spotte, S. 1982. The incidence of twins in pinnipeds. Canadian Journal of Zoology, 60(9), 2226–2233. DOI: 10.1139/z82-285.

Trites, A. W. 1991. Fetal growth of northern fur seals: life-history strategy and sources of variation. Canadian Journal of Zoology, 69(10), 2608–2617. DOI: 10.1139/z91-367.

Vaz-Ferreira, R. 1982. Otaria flavescens (SHAW), South American sea lion. In: Mammals in the Seas: FAO, UNEP, Report 4, 477–495.

Weckerly, F. W. 1998. Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals. Journal of Mammalogy, 79(1), 33–52. DOI: 10.2307/1382840.






Short communication