Observations of manatees in aggregations. American Museum novitates ; no. 1811

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New York, N.Y. : American Museum of Natural History
"The difficulties of observing wild manatees under ordinary circumstances were found to be substantial and were considered to explain the absence of any previous report of systematized field observations. Natural cold-induced aggregations of wild manatees were found to provide favorable circumstances for field observations. Identification of individuals by means of scars permitted recognition of some of them five and a quarter years after first identification. During the last winter season of observations, 1954-1955, in 10 aggregations, 57 marked individuals were recognized and 195 individuals were estimated to have been present. Some of these evidently reside in the vicinity at least during the winter season. And of these some appear to move in for the winter season, possibly taking part in a seasonal migration. Presence or absence of barnacles and algae on the skin indicates that some individuals reside in fresh water up river, others in the saline waters of the bay. Pattern of attendance of aggregations by marked individuals suggests that their ranges were dispersed and reveals no evidence of social organization. Mothers with young were not accompanied by other individuals. Groups within the aggregations engaged in play. The muzzle-to-muzzle contact between individuals involves lifting snouts above the surface, perhaps as relict behavior inherited from terrestrial ancestors. The usually observed courtship behavior was of a male approaching, nuzzling, 'embracing,' and presenting its venter to some presumed female, which most frequently turned away or swam off before courtship proceeded further. Of the identifiable sample of 65 individuals about 15 per cent were recorded as immatures and 15 per cent as calves, each closely accompanying an adult. The relative sizes of calves and other evidence suggest lack of any distinct breeding season. Annual reproduction by adult females is questioned. Young sometimes rode on mother's back. Suckling took place in horizontal psition, under water, without embrace. Very young calves swam only with flippers. Adults ordinarily swam only with tail, but one adult regularly used its flippers also"--P. 22-23.
24 p. : ill. ; 24 cm.
Includes bibliographical references (p. 23-24).