Comportamento diurno e uso do habitat pelos golfinhos sousa chinensis na costa ocidental e sul da ilha da inhaca, baía de maputo

Abstract

Habitat behavior and use by the Sousa chinensis species was studied on the western and southern coast of Ilha da Inhaca, Maputo Bay, between January and April 2001, through 76 boat trips and 36 fixed point surveillance sessions at Ponta Ponduine during high tide. The behavior of the dolphins was studied during 30.2 hours of which 9.3 hours of time on the West Coast and 20.9 hours in the South Bay of Inhaca. The focus group observation method (Scan Sampling) was used, the main and secondary behaviors in the habitats were studied and the route used by the dolphins in the South Bay was also identified. In 68% of the trips, dolphins of the Sousa chinensis species were not observed, suggesting a low frequency of use of the area. Dolphins were observed in 22 observations of S. chinensis dolphins, 4 of T. truncatus and 4 of dugongs. Normal foraging was the predominant behavior on the West Coast and South Bay of the inhaca. Active foraging was only observed in South Bay due to the ease of chasing prey in shallow channels. However, the occurrence of different main and secondary behaviors was influenced by the type of habitat and movement pattern. The phases of the semi-diurnal tidal cycle and the occurrence of offspring did not significantly influence the duration of the different types of behavior, foray and socialization of Sousa ch/nensis. In Inhaca South Bay there were no differences in the average duration of habitat use although dolphins spent more time in channels and banks and less time in other habitats implying that prey is more abundant and frequent in these two habitats. The occurrence of offspring did not influence the different types of spatial dispositions of the group, suggesting that only the mother is concerned with the protection of the offspring. But, the type of habitat and pattern of movement influenced the frequency of different types of spatial arrangements of the pod of dolphins. The behaviors were more frequent in the channels and during the non-directional movement numerous behaviors were exhibited. The dolphin route consists of movements along the banks of the channels of the West Coast of Inhaca and in the center of the shallow channels of the South Bay. The dolphins did not enter the Saco da Inhaca. Although they frequented the part close to the Ponta Torres channel that connects with the Ocean, the dolphins never crossed this to the ocean waters. There is a certain association between the main and secondary behaviors: travel was associated with secondary behaviors, socialization and opportunistic fleeing. Normal foraging was associated with several secondary behaviors (socialization, opportunistic and active foraging) but with low frequency. Some behaviors could not be described during the study and their percentage was relatively high. During high tide, dolphins occurred on the West Coast and throughout the South Bay of Inhaca along the channels. In the rising and ebb tides, the S. chinensis dolphins used the two inlet and outlet channels of the South Bay of Inhaca: Machangulo Channel and Ponduine Channel and never crossed the outermost part of the South Bay Bank(TRADUÇÃO NOSSA)