. Ecology and behavior of the Manatee (Trichechus manatus) in Florida . ABC Fig. 18. Diagrammatic representation of the use of the tail as a rudder. Pos- terior view of a cruising manatee in forward glide (A), preparing to turn to the right (B), and preparing to turn to the left (C). Roll does not always accompany a turn. It should be mentioned here that dugongs are more streamlined than are manatees and show other structural modifications, in- cluding a fluke, that suggest a greater specialization for aquatic life than is found in trichechids. The tail of the manatee also serves as a rudder (
. Ecology and behavior of the Manatee (Trichechus manatus) in Florida . ABC Fig. 18. Diagrammatic representation of the use of the tail as a rudder. Pos- terior view of a cruising manatee in forward glide (A), preparing to turn to the right (B), and preparing to turn to the left (C). Roll does not always accompany a turn. It should be mentioned here that dugongs are more streamlined than are manatees and show other structural modifications, in- cluding a fluke, that suggest a greater specialization for aquatic life than is found in trichechids. The tail of the manatee also serves as a rudder (Fig. 18). Ac- cording to Kinzer (1966), the tail may be at an angle as great as 45 degrees to the long axis of the body when a manatee is turning in a circle. Cruising animals can steer, bank, and roll by means of the tail alone. Immobile or idling manatees frequently adjust the angle of the tail to counteract roll and, to some degree, yaw. At the same time, the tail may be elevated or depressed to adjust the longitu- dinal axis of the body. Stroke rate.—Stroke rate and the amplitude of undulations of the tail vary with the state of activity. Defining a stroke as one complete undulation of the tail, I determined the stroke rates of adult and subadult manatees while idling, cruising, and fleeing. Adult man- atees were seen to stroke 18 to 20 times per minute when idling and 24 to 36 times per minute while cruising. Idling involves sev- eral moderate strokes followed by a glide. Idling manatees swim with less regular strokes than when cruising and either dangle their flippers or adduct them at the wrists under their chests. When cruising, in contrast, manatees tend to maintain a constant rhythm of even strokes, the tail moves through a greater arc, and the flippers are held back flush against the body. Maximum stroke rate and amplitude are associated with flight. Fleeing manatees were observed to stroke their tails 45 to 50 times per minute.
Size: 4491px × 1113px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectmammals
