Population biology and socio-ecology of Indo-Pacific humpback dolphins Sous
a chinensis were investigated during a 3-year study period in the Algoa Bay
region, South Africa. The dolphins inhabit a narrow strip of coastal water
s, mostly less than 15 m deep. Groups are small (mean = 7 animals) and thei
r daily activities concentrate around shallow rocky reefs-the primary feedi
ng grounds. Dependence on these restricted, shallow-water habitats is evide
nt throughout the year. Site fidelity is generally weak and is subject to s
easonal migration, although female site fidelity seems to be related to rep
roductive stage. Births occur predominantly in summer. The social system is
highly fluid, structured to some degree by sex and age,'mate-searching' be
haviour being the most likely male reproductive strategy. The dolphins inha
biting Algoa Bay are part of a substantially larger population that uses a
considerable length of the coastal zone. Estimated population parameters ar
e generally low, as are modelled population growth rates, and an increase i
n the population size seems unlikely. Humpback dolphins appear to be vulner
able to negative environmental pressure and the alteration/destruction of i
nshore habitats is probably among the greatest threats to them. Conservatio
n of this species should be given high priority and be seen as an important
part of integrated coastal zone management. Establishment of multiple-use
management areas with controlled ecotourism and several priority sites decl
ared as strict reserves seems to be the most effective conservation approac
h. In order to be successful, conservation and management policies need to
recognize the needs and lifestyles of the local inhabitants.