Summary
The results of a study to evaluate radio-tracking and freeze-branding techniques as applied to the study of the ecology of wild Amazonian manatees are presented. A young male Trichechus inunguis was radio-marked and released in a series of flood-plain lakes near Manaus, Brasil. We used a 150 mHz transmitter attached by a "coliar" around the caudal peduncle of this animal and the daily movements were monitored during 20 days using standard triangulation techniques. We were easily able to follow the animal's movements (~ 2.6 km/d) and on several occasions were able to approach to within 3 m of it and make behavioural and feeding observations both visually and using a hydrophone. Based on the respective rates of movement there were no significant differences between day and night activity patterns (day, 0.14 ± 0.17 km/h and night 0.08 ± 0.12 kg/h). Five months prior to its release the animal was freeze-branded for 25-30 sec. with a copper branding iron using liquid nitrogen as the coolant. Although there was some cutaneous tissue damage, the brand healed quickly and a legible mark remained. The interpretation of radio-tracking data in further studies is discussed.