by Megan Guerzon
by Megan Guerzon
Physical
Characteristics
The animals are
generally dark gray or black above, with a lighter colored belly. The length of
adults varies, from about 6.5 to about 13 ft. Generally, males are slightly
larger than females, and cold-water bottlenose dolphins are larger than their
warm-water counterparts. Bottlenose dolphins have a prominent, curved dorsal fin
with a thin trailing edge that readily tatters. This distinctive tattering has
been used by researchers to identify and track individuals and groups.
Habitat
The bottlenose lives along almost all tropical and
temperate coasts to about latitude 40° south and to latitude 45° north. It can
also live around the British Isles and up to latitude 60° north. Bottlenose
dolphins are coastal in most areas and remain in groups of 20 or sometimes less
than that. Although offshore varieties also exist in many places, groups can be
as large as 200 (usually in deep water). Some populations can make seasonal
migrations.
Prey/Predators
Bottlenose dolphins feed on many different types
of prey, including shrimp, squid, fishes and other invertebrates. The dolphins
feed by nosing into rocky crevasses near the shore, by chasing fish onto mud
banks and snapping them up while they are stranded on the beach, or by herding
prey into dense clusters, sometimes against a shore or up to the surface of the
water. The dolphins also take advantage of human fisheries. They sometimes wait
by following shrimp boats for the prey and hope that the fishermen will toss
some overboard.
Mating
Bottlenose dolphins are
sociable and societies appear to stay together for life. Females come to sexual
maturity after 5 to 12 years, and males after 9 to 13 years. There is some
evidence for polygamous mating; in which there is no overt aggressive
competition by either males or females for access to mates. After a growth
period of about 12 months, a single calf is born. Calves nurse for up to 18
months. The dolphins communicate by means of a rich range of whistles and
rasping sounds. In at least some populations, individuals appear to have a
signature whistle. Bottlenose dolphins are able to discriminate even small
objects by echolocation (that is, they send out high frequency clicks that
bounce off prey and other objects and use the returning echoes to distinguish
the objects).