2National Biological Service, Midcontinent Ecological Science Center, 4512 McMurry Ave., Fort Collins, Colorado 80525-3400, U.S.A.
AGE DETERMINATION IN MANATEES USING GROWTH-LAYER-GROUP COUNTS IN BONE
Article first published online: 26 AUG 2006
Marine Mammal Science
Volume 12, Issue 1, pages 54–88, January 1996
How to Cite
Marmontel, M., Nhea, T. J., Kochman, H. I. and Humphrey, S. R. (1996), AGE DETERMINATION IN MANATEES USING GROWTH-LAYER-GROUP COUNTS IN BONE. Marine Mammal Science, 12: 54–88. doi: 10.1111/j.1748-7692.1996.tb00305.x
1Projeto Mamiraua, Av. Brasil, 197, 69470 Tefe AM, Brazil.
3now with National Biological Service, same address.
- Issue published online: 26 AUG 2006
- Article first published online: 26 AUG 2006
- Received: 3 May 1994 Accepted: 13 June 1995
- age determination;
- growth layers;
- Trichechus manatus;
Growth layers were observed in histological preparations of bones of known-age, known minimum-age, and tetracycline-marked free-ranging and captive Florida manatees (Trichechus manatus latirostris), substantiating earlier preliminary findings of other studies. Detailed analysis of 17 new case histories showed that growth-layer group (GLG) counts in the periotic bone were consistent with known age, or time since tetracycline administration, but were less reliable in other bones. GLG counts were also made in periotic bones of 1,196 Florida manatees of unknown age found dead from 1974 through 1991. These counts were conducted in order to assess variability and to determine relationships among estimated age, size, sex, and degree of bone resorption. Resorption can interfere with accuracy of GLG counts. This effect does not occur until ages greater than about 15 yr and body lengths greater than 300 cm are attained. GLGs were also observed in periotic bones of Antillean manatees (Trichechus manatus manatus) but were not validated against known-age specimens. Use of GLG counts in the periotic bone is suitable for application to studies of population dynamics and other age-related aspects of manatee biology.