Inter-lab comparison of precision and recommended methods for age estimation of Florida manatee (Trichechus manatus latirostris) using growth layer groups in earbones

  • Katherine Brill P.O. Box 7646, Merrifield, Virginia 22042
  • Miriam Marmontel Mamirauá Institute for Sustainable Development, Estrada do Bexiga 2584, Tefé, 69553-225
  • Meghan Bolen-Richardson 1093 A1A Beach Blvd #548, Saint Augustine, FL 32080
  • Robert EA Stewart 1218 Marchand Road, Howden MB, R5A 1J6
Keywords: manatee, ageing, earbone

Abstract

Manatees are routinely aged by counting Growth Layer Groups (GLGs) in periotic bones (earbones). Manatee carcasses recovered in Florida between 1974 and 2010 provided age-estimation material for three readers and formed the base for a retrospective analysis of aging precision (repeatability). All readers were in good agreement (high precision) with the greatest apparent source of variation being the result of earbone remodelling with increasing manatee age. Over the same period, methods of sample preparation and of determining a final age estimate changed. We examined the effects of altering methods on ease of reading GLGs and found no statistical differences. Accurate age estimates are an important component for effective management of the species and for better models of population trends and we summarize the currently recommended methods for estimating manatee ages using earbones. 

Published
2016-06-01
How to Cite
BrillK., MarmontelM., Bolen-RichardsonM., & StewartR. E. (2016). Inter-lab comparison of precision and recommended methods for age estimation of Florida manatee (Trichechus manatus latirostris) using growth layer groups in earbones. NAMMCO Scientific Publications, 10. https://doi.org/10.7557/3.3786