Bottlenose dolphins live in groups called pods (Scott,
Wells, and Irvine, 1990).
a. A pod is a coherent long-term social
unit.
b. The size of a pod varies significantly with its composition.
On the west coast of Florida, mean pod size is about seven animals
(Scott, Wells, and Irvine, 1990).
c. In the wild, pod composition and structure are based largely
on age, sex, and reproductive condition (Wells, 1991).
(1) Researchers
on the eastern U.S. coast commonly sight mother-calf pairs and
pods of mature females with their most recent offspring
(Wells, 1991).
(2) Subadults typically occur in mixed-sex and single-sex groups
(Wells, 1991).
(3) Adult males are often observed alone, or in pairs or occasional
trios (Wells, 1991). Adult males commonly move between female groups
in their range, and may pair up with females for brief periods.
Adult males rarely associate with subadult males (Wells, 1991;
Herman, 1980).
In general, size of pods tend to increase with
water depth and openness of habitat. This may be correlated with
foraging strategies
and protection (Shane, et al., 1986).
Several pods may join temporarily (for several
minutes or hours) to form larger groups called herds or aggregations.
Up to several
hundred animals have been observed traveling in one herd (Shane,
et al., 1986).
Researchers have identified certain factors that
tend to
cause a pod to either draw together or to disperse somewhat
(Herman,
1980).
a. Factors that tend toward cohesion include protection,
fright, and familial associations.
b. Factors that tend toward dispersion include alertness,
aggression, and feeding.
There may be a social hierarchy within a group of bottlenose
dolphins.
B. Social behavior.
Dolphins in a pod appear to establish strong
social bonds. Behavioral studies suggest that certain animals
prefer association
with each
other and recognize each other after periods of separation.
Field observations suggest that mother-calf bonds are
long-lasting.
a. Mother-calf bonds are long-lasting; a calf typically
stays with its mother three to six years or more (Wells,
1991).
b. Adult male pair bonds are strong and long-lasting.
Male pairs often engage in a number of cooperative
behaviors (Wells, 1991).
Bottlenose dolphins establish and
maintain dominance
by biting, chasing, jaw- clapping, and smacking their
tails on the water
(Shane, et al., 1986; Herman, 1980).
Dolphins often show aggression by scratching one
another with their teeth, leaving superficial lacerations
that
soon heal (Shane,
et al., 1986). Traces of light parallel stripes
remain on the skin of the dolphin. These marks have been
seen in virtually
all species
of dolphins. Dolphins also show aggression by emitting
bubble clouds from their blowholes.
During courtship, dolphins engage in head-butting
and tooth-scratching (Shane, et al., 1986).
Bottlenose dolphins often hunt together. See
Methods of collecting food.
Dolphin courtship behavior includes twisting, nuzzling, and
tooth-scratching.
C. Daily activity cycles.
Observations
indicate that dolphins undergo daily cycles of activity.
Bottlenose
dolphins are active to some degree both day and night (Shane,
et al., 1986).
Social behavior comprises a major portion of bottlenose
dolphins'daily activities (Shane, et al., 1986).
Feeding usually peaks in the early morning and late afternoon
(Shane, et al., 1986).
D. Individual
behavior.
Dolphins frequently ride on the bow
waves or the stern wakes of boats. This is probably adapted
from
the natural behavior
of riding ocean swells, the wakes of large
whales, or a mother dolphin's "slip stream" (hydrodynamic
wake) (Shane, et al., 1986).
Dolphins have
been seen jumping as high as 4.9 m (1
6 ft.) from the surface of the water
and landing
on their backs or sides,
in a behavior called a breach.
Both young
and old dolphins chase one another, carry objects around,
toss seaweed to one another,
and use
objects to solicit
interaction. Such activity may be practice
for catching food.
In a common behavior called a breach, a bottlenose dolphin jumps
out of the water and lands on its side.
E. Protection and care.
Large adult males often roam the periphery
of a pod, and may afford some protection against predators
(Herman, 1980).
Researchers have observed scouting behavior in bottlenose
dolphins. An individual may investigate novel objects
or unfamiliar territories and "report" back
to the pod (Herman, 1980).
Bottlenose dolphins may
aid ill or injured pod mates. They may stand by
and vocalize, or they may physically
support the
animal at the surface so it can breathe.
F. Interaction with other species.
Bottlenose
dolphins have been seen in groups of toothed whales such as
pilot whales, spinner dolphins, spotted dolphins, and
rough-toothed dolphins.
Bottlenose dolphins have been seen riding the
pressure waves of gray whales, humpback whales,
and right whales (Shane, et
al., 1986). They often force Pacific white-sided
dolphins away from prime spots in the waves
(Herman, 1980).
Dolphins respond to sharks with tolerance, avoidance,
and aggression. Tiger sharks elicit the strongest
responses from
dolphins (Shane, et al., 1986). Researchers have
observed dolphins attacking, and sometimes killing,
sharks in the wild (Herman,
1980).
Some individuals in the wild regularly solicit
attention, such as touching and feeding, from
humans (Shane, et al., 1986).
