Bottlenose
dolphins are very adaptable, so they can be found in cold temperate
to tropical waters throughout the world. Two separate populations of
Tursiops exist. One population is found inshore, in the shallow waters
(under 30metres) along coastlines and the other population is found
offshore, in deep ocean waters over 30m (www.cetacea.org).
The
majority of this website is devoted to the social behaviour of coastal
bottlenose dolphins, so a brief description of offshore interactions
is given here. Offshore dolphins can be found more than 27km from any
coastline. These populations exhibit long-term site fidelity and
repeated, regular associations within the herd (Rossbach and Herzing,
1999). These associations strengthen the social bonds within the herd,
which is essential for cooperative foraging and hunting offshore where
food is harder to locate than inshore. The strongest and most permanent
groups in offshore dolphins follow the same pattern as inshore dolphins,
with same-sex groups being dominant (Rossbach and Herzing, 1999).
Dolphins,
as carnivores, follow their prey in a home range, and may migrate in
response to changing environmental conditions, such as water temperature,
storms, etc. (www.cetacea.org).
Defran et al. (1999) estimated home ranges of 50km to 470km along the
shoreline (considered conservative estimates) in a population of Pacific
coast bottlenose dolphins. All these dolphins remained within 1km of
the shoreline. This narrow but long range can be explained by the moving
food resources, and implies that dolphin home ranges follow prey distribution.
Thus, Tursiops habitat and home range are largely determined by the
quality, abundance, distribution and ease of hunting their prey (Grigg
and Markowitz, 1997).
Seagrasses
are an important nursery habitat for dolphins because the grasses provide
protection from predators and a rich prey area in which juveniles practice
hunting (Barros and Wells, 1998).