Behavior and ecology of the bottlenose dolphin, Tursiops truncatus, in the South Atlantic

Abstract

Bottlenose dolphins observed nearshore in Golfo San Jose, Argentina, spent 92% oftheir time in water less than 10 m deep. They moved into deeper water, up to 39 m depth, mainly during midday in nonsummer for brief (16 min) periods. They moved more rapidly in deeper water, and may have been feeding on schooling fish at that time. During summer they stayed in shallow water, 2-6 m deep. Dolphins moved parallel to shore and in consistent depth of water at almost all times. They changed direction at predictable locations and patrolled certain nearshore waters for up to several hours. Their movement was influenced by tide and by nearshore rocks. Slow movement and apparent resting occurred mainly riuring the morning, while most aerial behavior, apparent sexual and social behavior, and rapid-movement feeding occurred in the afternoon. The Atlantic bottlenose dolphin, Tursiops trun­ catus, is undoubtedly the best studied of any of the toothed cetaceans. It was successfully kept in cap­ tivity over 60 yr ago (Townsend 1914), and has since that time served as the white rat of cetol­ ogy, with a great deal known about its behavior in captivity, but until relatively recently practically nothing known about its behavior in the wild. Long-term behavioral studies of stable bottlenose dolphin colonies in captivity were mainly carried out at Marine Studios/Marineland ofFlorida from the mid-1930's to mid-1950's (McBride 1940; McBride and Hebb 1948; McBride and Kritzler 1951; Essapian 1953, 1963; Tavolga and Essapian 1957; Tavolga 1966). These studies showed that bottlenose dolphins have a complex social organi­ zation, often with a male-dominated social hierar­ chy. From some ofthese studies also developed the idea that bottlenose dolphins, and other odonto­ cete species as well, use echolocation (McBride 1956). This concept was validated by numerous workers in the 1950's and 1960's (Schevill and Lawrence 1956; Kellogg 1961; Norris et al. 1961). Other l'esearch on captive bottlenose dolphins in general (including the species T. gilli and T. aduncus, as well as T. truncatus) was reported by Brown and Norris (1956), Caldwell et al. (1965), D. K. Caldwell and M. C. Caldwell (1972), M. C. Caldwell and D. K. Caldwell (1972), Tayler and Saayman (1972), and Saayman et al. (1973). The