|Florida Marine Mammals: Dolphins (2)|
Dolphin-Risso's dolphins are a relatively robust dolphin with a
rounded head, similar in shape to the more familiar pilot whale. They
have an unusual external vertical crease in the melon (the organ in the
rounded head used to direct sonar clicks) that runs from the front of
the forehead to the mouth. Adult Risso's dolphins are usually dark gray
with extensive white scarring. The scars can be scratches, splotches, or
circular marks and, in some animals, can be so extensive that the entire
body appears to be white. This scarring may come from bites from other
Risso's dolphins, squid bites, or parasites. As calves, their bodies are
a uniform light gray, which then darkens to a brownish-gray in
juveniles. Risso's dolphins also have a white anchor-shaped patch on
their ventral/chest area (from throat to stomach). Reflecting the
offshore distribution of this species, primary prey appears to be squid,
although they have also been known to feed on a number of fish species.
While the size of their squid prey is unknown, squid beaks from species
that grow up to 12 feet in length have been found in the stomachs of
stranded Risso's dolphins. Risso's dolphins tend to prefer offshore
habitats worldwide in the warm temperate and tropical waters of both
Rough-toothed Dolphin- The rough-toothed dolphin is named for the 20-27 teeth with faint ridges located in both the upper and lower jaw. Color varies by region within the species, but generally they are dark gray with light spots on the flanks. The ventral side, lower jaw and lips are white and they have a darker marking that extends over the eyes to the upper part of the flanks. Like other marine species, rough-toothed dolphins may show scars resulting from encounters with other marine life such as sharks, squid, and other rough-toothed dolphins. Rough-toothed dolphins are small members of the dolphin group that reach a length of 8.5 feet and weight of 350 pounds Like other dolphins, rough-toothed dolphins communicate and echolocate using clicks and whistles. Reproductive biology is poorly known in this species, but it is known that maturity occurs at 11 years of age and maximum longevity is 32 years. Rough-toothed dolphins usually occur in tight-knit groups of 10 to 20. Rough-toothed dolphins apparently feed primarily on squids and fishes.
Spinner Dolphin- So called for their high, spinning leaps, spinner dolphins are known as playful, eager bow-riders. Spinner dolphins are found in the Atlantic, Indian and Pacific Oceans, where they are restricted to tropical, subtropical and less often warm, temperate regions. Spinner dolphins are characterized by a long slender beak with a black tip and black lips, and an erect dorsal fin. The body is mainly grey, with a three toned coloration. Adult spinner dolphins are about 5.9 -6.6 feet in size and weigh 165-209 pounds. Spinner dolphins often associate with spotted dolphins, common dolphins and small to medium sized whales. Spinner dolphins typically congregate together in groups or pods. These groups however are not really comparable to those formed by other mammals. The society is leaderless and very fluid. Associations change daily and there is no strict hierarchy of dominance. In each group however there is usually a core of individuals who associate on a regular basis.
Striped Dolphin-Striped dolphins are the most widespread dolphins in the world. These dolphins can reach lengths of about 9 feet and weigh up to 350 pounds. They have a small to medium-sized robust, sleek body with a long, defined beak and round "melon" (forehead). Their distinct and striking coloration pattern with a complex of bold thin stripes is the origin of its common name. Calves and juveniles may have more muted colorations and patterns. Striped dolphins are usually found in tight, cohesive groups averaging between 25 and 100 individuals, but have been occasionally seen in larger groups of up to several hundred and even thousands of animals. Within these schools there is a complex system of individuals that may be organized by age, sex, and breeding status. They rarely associate with other species of whales, dolphins, and seabirds. Their surface behavior is often characterized as sociable, athletic, energetic, active, and nimble with rapid swimming. They can often be observed breaching, "roto-tailing", jumping, and leaping up over 20 feet above the surface of the water. Striped dolphins feed on a diverse diet consisting of various species of relatively small, closely-packed schooling fish such as cod, squid and octopus.
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