Age determination in manatees using growth-layer-group counts in bone

Marine Mammal Science
By: , and 



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.

Publication type Article
Publication Subtype Journal Article
Title Age determination in manatees using growth-layer-group counts in bone
Series title Marine Mammal Science
DOI 10.1111/j.1748-7692.1996.tb00305.x
Volume 12
Issue 1
Year Published 1996
Language English
Publisher Wiley
Description 35 p.
First page 54
Last page 88
Online Only (Y/N) N
Additional Online Files (Y/N) N
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