Post by Tikara on Jan 4, 2008 3:13:22 GMT -5
Dolphins
Bottlenose Dolphin
DESCRIPTION:
Bottlenose dolphins are light to dark gray over their dorsal surface, fading into a white or cream along their ventral region. They have a streamlined fusiform body shape. The source of their common name, bottlenose dolphins exhibit a pronounced anterior rostrum (often referred to as a beak), typically 7-8cm (3 in.) in length. Said rostrum generally contains 76-98 conically-shaped, homogenous teeth - with tooth counts varying among individuals. Their dorsal fin is falcate.
It should be noted that two distinct ecotypes are recognized. The coastal ecotype typically exhibits smaller average body size with relatively larger flipper size. Comparatively, the offshore ecotype typically exhibit larger average body size and darker coloration - among other morphological distinctions.
SIZE:
Calves are approximately 106-132 cm (42-52 in.) at birth.
MALE Males may be slightly larger than females
Newborn calves weigh approximately 20 kg (44 lbs.)
MALE Physically mature males tend to be more massive than physically mature females
DIET: fish, squid and some eels
NURSING DURATION Up to 18 months (wean)
SEXUAL MATURITY: Typically exhibited as a function of age-dependent body size
MALE Sexual maturity for males is attained once body length reaches 2.4-2.6 m (8-8.5 ft.), generally between 9-13 years of age
FEMALE Sexual maturity for females is attained once body length reaches 2.3 m (7.5 ft.), generally between 5-12 years of age
LIFE SPAN:
Approximately 20 years (average); Maximum lifespan appears to be in 45-50 year range (with 1-2% of population attaining maximum age)
MALE Maximum lifespan for males appears to be in 40-45 year range
FEMALE Maximum lifespan for females appears to be slightly greater (i.e. 5-10 years) than that of males
RANGE:
Temperate and tropical marine waters worldwide; In the Pacific, they are found from northern Japan to Australia and from southern California to Chile; In the Atlantic, they are found from Nova Scotia to Patagonia and from Norway to the tip of South Africa; In the Indian Ocean, they are found from Australia to South Africa
HABITAT:
Primarily temperate and tropical waters; coastal ecotype typically inhabits nearshore waters including harbors, bays, lagoons, gulfs, estuaries, with occassional forays into large rivers; offshore ecotype typically inhabits pelagic regions extending to the continental shelf as well as select atolls and ocean islands
Atlantic spotted dolphin
Description:
The Atlantic spotted dolphin looks very similar to the pantropical spotted dolphin. The Atlantic Spotted dolphin tends to be more robust, with more spots and darker skin. As the dolphins get older, they develop more spots. Atlantic spotted dolphins have dark purple/grey capes with light spots, and white undersides with dark spots. Along each side they have a wide grey stripe. Their beaks are quite long and thick with white tips and white "lips". There is a light grey stripe running from the eye to the flipper which is curved with a pointed tip. Atlantic spotted dolphins have between 32 and 42 teeth in each row of the upper jaw and between 30 and 40 teeth in each row of the lower jaw. There are coastal and offshore groups and these can be quite different to each other. The offshore form tends to be smaller than the coastal and has fewer spots.
Length (metres):
New-borns are between 80cm and 1.2 metres (32in 4ft) in length. Adults are between 1.7 and 2.3 metres (5ft 9in and 7ft 6in).
Weight:
Adults weigh between 100 and 140 kg (220-310 lb). The birth weight of Atlantic spotted dolphins is not known.
Diet:
Fish, squid and sometimes invertebrates (animals without a backbone such as starfish)
Behaviour:
Atlantic spotted dolphins are active creatures. They enjoy leaping out of the water and falling back in with a big splash. They are most likely to be seen jumping out of the water when they are feeding. They are very curious and will swim up to boats and bow-ride . They live in groups of between 5 and 15, though the inshore populations are more likely to be seen in smaller groups
Spotted dolphins seem to be less spotted as you travel East in the Atlantic and West in the Pacific. For this reason they can often be mistaken for bottlenoses.
Atlantic spotted dolphins have no spots when they are born. They are about a year old when the first greyish white spots begin to appear.
Dusky Dolphins
Description:
Physically they are like the Pacific white-sided dolphin. They have a short, dark beak and gently sloping forehead. Their upper sides are predominantly dark or blue-black, but there are white or pale-grey blazes along their sides. Their dorsal fins are very tall with an area of light grey on the rear half. At sea it is best to look for the light face and short blunt beak.
Length (metres):
Adult duskies are between 1.6 and 2.1 metres (5ft 3in - 7ft) long. When they are born they are between 55 and 70cm (22 - 28in).
Weight:
New-born dusky dolphins weigh between 3 and 5 kg (7 - 11lb) and when they are fully grown they will weigh between 50 and 90 kg (110 - 200 lb).
Diet:
Fish and squid
Behaviour:
group at surface. one leap - new zealand - (c)ingrid visserDusky dolphins are one of the most acrobatic of all the dolphins; they are well-known for their amazingly high jumps and twists. When one dolphin starts leaping, the rest of the group often start leaping too, putting on quite a display! Dusky dolphins are highly inquisitive and usually easy to approach. They are very social and can be found in groups of hundreds. They are also frequently seen with other cetaceans as well as with seabirds.
Common Dolphins
Description:
Common dolphins are easily recognised by the hourglass pattern and tan or yellowish patch on each side, although they can sometimes be confused with striped dolphins. They have a dark cape ranging from black to brown with a v-shape under the dorsal fin. They also have a white underside with occasional yellow streaks and a white tail stock. Their flukes are dark on both sides, and their dorsal fins range from curved to triangular and can be black, greyish white or somewhere in-between. They vary so much that people have suggested there are a number of different species. Only two distinct forms are recognised; the long-beaked and short-beaked. There are only subtle differences between the sexes and males and females are difficult to tell apart.
Length (metres):
When they are born, common dolphins are about 80cm long (32in). They grow to between 1.7 and 2.4 metres (5ft 9in - 8ft) in length.
Weight:
We do not know how much common dolphins weigh when they are born, but adults are between 70 and 110 kg (155 - 245lb).
Diet:
Fish, Squid
Behaviour:
Common dolphins are often found in large, socially active groups. Their school size depends upon the time of day and season. When they are frightened, they bunch tightly together. They are fast swimmers and enjoy acrobatics - lobtailing, flipper slaps and breaching. They are highly vocal and can be heard above the surface. They do short dives of 10 seconds to 2 minutes, although dives of 8 minutes have been recorded. They may associate with other dolphins at feeding grounds and in the eastern tropical Pacific they may be seen with yellowfin tuna.
Common dolphins are very vocal. They make high-pitched squealing noises which can sometimes be heard above the water surface!
Spinner Dolphins
SHORT-SNOUTED SPINNER Little is known about the short-snouted Atlantic spinner. It ranges from the Gulf of Mexico to the Caribbean, and from the mid-Atlantic to the northwest coast of Africa. Its length is 7 feet (2 m), and its weight is 200 pounds (90 kg). Its flippers are small and pointed at the tips, and its dorsal fin is curved and nearly pointed, and is located in the middle of the back. Its color is dark gray on the upper body, with a light gray area from the eyes along the sides to the tail; its belly is white. It eats small fish and squid, and is found in small herds in very deep water.
LONG-SNOUTED SPINNER The known Pacific forms of this species include the Costa Rican, the eastern, the whitebelly, the Hawai'ian (Gray's), and a dwarf form found in the Gulf of Thailand. They are differentiated by size -- ranging from 5.5 to 6 feet (1.65 to 1.8 m) for the eastern spinner, to 7 feet (2m) for the Costa Rican spinner; by weight -- from 135 pounds (61 kg) for the eastern, to 200 pounds (91 kg) for the Hawai'ian; and by differences in shape and markings. The Hawai'ian form seems to be typical for the species elsewhere in the range including the Indian and Atlantic oceans.
PHYSICAL DESCRIPTION: The body size, shape, and color patterns of the various forms differ according to geographical location. Spinners in general all share common characteristics: their bodies are slender, their beaks are long and thin (except for the Atlantic short-snouted spinner) and their flippers are small and pointed at the tips. Their coloring is in shades of dark gray, light gray, and white; most forms have white bellies.
Feeding: The spinner dolphin's diet consists of small fish and squid. Spinners have more teeth than other species of dolphins, with between 45 to 65 sharp, pointed teeth in each side of both the upper and lower jaws. They feed at night.
Mating and Breeding: Females reach sexual maturity at about 4 to 7 years, males at about 7 to 10 years. A newborn calf averages 32 inches (80 cm) in length. The gestation period is 10 1/2 months, and the calving interval is between 2 to 3 years. Calves nurse for from 1 to 2 years.
Distribution and Migration: The Costa Rican spinner is found in large, close-knit groups of 1,000 or more animals in coastal waters less than 90 miles (150 km) off the western coast of Central America; the eastern spinner is a more oceanic species found in deep water off the coast of Mexico and the west coast of Central America, often travelling in large herds of thousands or more, sometimes in the company of spotted dolphins; the whitebelly spinner is distributed even further offshore from Mexico, Central America, and the Pacific region of northern South America, travelling in herds of 1,000 or more; the Hawai'ian spinner is common throughout the Hawai'ian Islands and congregates in herds of 200 or more.
Orcas
PHYSICAL DESCRIPTION: The orca is a stout, streamlined animal. It has a round head that is tapered, with an indistinct beak and straight mouthline.
COLOR: The orca has a striking color pattern made up of well-defined areas of shiny black and cream or white. The dorsal (top) part of its body is black, with a pale white to gray "saddle" behind the dorsal fin. It has an oval, white eyepatch behind and above each eye. The chin, throat, central length of the ventral (underside) area, and undersides of the tail flukes are white. Each whale can be individually identified by its markings and by the shape of its saddle patch and dorsal fin.
FINS AND FLUKE: Another distinctive feature of the orca is its dorsal fin, which can reach 6 feet (1.8 m) high in males and is shaped like an isosceles triangle. The immature male and the female dorsal fins are also large, reaching 3 feet (.91 m) high, but are falcate (curved). The dorsal fin often has identifying nicks, cuts, scars and indentations. The paddle-shaped pectoral flippers are broad, rounded, and can reach a length of nearly 6 feet (1.8 m) and a width of 3 feet (.91 m).
Length and Weight: Males can grow as large as 32 feet (9.6 m) long and weigh 8 to 9 tons. Females can reach 23 feet (8.2 m) in length and weigh up to 4 tons.
Feeding: The mouth of the orca is large and well adapted for hunting. It has 46 to 50 conical shaped teeth that point slightly backwards and inwards. The upper and lower teeth interlock, which aids in gripping large prey and tearing it into smaller pieces for easier swallowing. Depending on the population and geographic area, the diet of orcas varies. Food preference and availability may have led to the distinct population types, such as resident, transients, and offshores that have been observed/identified in the Pacific Northwest region of the United States and other areas around the world. Generally speaking, transients will feed on a variety of animals including: sea lions, elephant seals, harbor seals, porpoises, squid, sharks, fish, penguins, smaller whales, such as belugas and narwhals and even large baleen whales, such as gray whales. Resident whales tend to feed primarily on fish species such as salmon or herring. The diet of offshores is still being studied by scientists.
Mating and Breeding: Little is known about the orca's breeding habits. Newborn calves have been observed throughout the year suggesting that that mating can occur at any time with no particular breeding season. In the wild, orcas become sexually mature between the ages of 10 and 18 years of age and are thought to be actively reproducing by the time the male reaches about 20 feet (5.1 m) in length and the female reaches about 16 feet (4.1 m). Based on long-term field studies, females are believed to be reproductively active into their early 40's. The maximum age for males is unknown. Captive females can bear a calf every two years, but a more typical period between calves in the wild is 3 to 5 years. The gestation period is estimated to be between 13 to 17 months. At birth, a calf is generally about 6-7 feet long (1.8-2.1 m) and weighs around 400 pounds. However, calf size and weight does vary slightly between populations/regions.
Distribution and Migration: The orca is found in all the oceans of the world, though they are more abundant in cooler waters. Unlike some other species of whales, which follow a regular migration route each year, the orca seems to travel according to the availability of food. They are one of the few species of whales that move freely from hemisphere to hemisphere.
Spotted Dolphins
PHYSICAL DESCRIPTION: Spotted dolphins are difficult to describe because their size and coloring vary according to their geographic location. Found only in tropical waters, and subtropical waters, there are two recognized species: the worldwide species, the pantropical spotted dolphin, Stella attenuata and the Atlantic species, Stenella frontalis. The spotted dolphin's body is covered with spots and becomes more densely spotted with age. In the eastern Pacific, coastal forms are the most heavily spotted, while those found in the Hawai'ian Islands and in Japanese waters and the eastern Indian Ocean have moderate spotting. The spotted dolphin has a long slim beak containing 35 to 48 small conical teeth in each side of the upper jaw and 34 to 47 small, conical teeth in each side of the lower jaw.
COLOR: Color varies according to geographical location, age, and the individual. Generally speaking, these animals go through five color phases:
1. newborn calves are dark gray with a white belly and no spots;
2. the color changes to two-tone, sharply divided, dark on top, light on belly and no spots;
3. adolescent phase when dark spots begin to appear on the lower part of the body;
4. light spots appear on the dark upper portion of the body;
5. dark ventral (underside) spots merge almost into a solid color with pink shading on the forward part of the belly
Its beak is black and the lips and tip of the beak are white. A dark link extends from the middle of the lower jaw to the flipper and both eyes are circled in black with a black connecting line from each eye across the beak.
FINS AND FLUKE: The dorsal (top) fin is tall and curved; the flippers are small and pointed. The flukes are small and pointed at the tips with a small median notch.
Length and Weight: Length averages about 7 feet (2.1 m); weight averages 220 pounds (100 kg). Calves are 32 to 36 inches (80 to 90 cm) at birth.
Feeding: Spotted dolphins feed on many varieties of fish and squid found near the surface of the water. In the eastern Pacific, pregnant females feed more on squid and nursing females tend to feed more on fish. The reason for this is unknown.
Mating and Breeding: This species reaches maturity between 6 and 8 years of age or when the animal is about 6.5 feet (2 m) in length. Mating and calving take place throughout the year; the calving interval is believed to be about every two years, but in stressed populations mating takes place at an earlier age and calving at shorter intervals, a response to the enormous mortalities suffered from being entangled in nets by the tuna fishery. Gestation is 11 1/2 months and calves are nursed for 11 months.
Distribution and Migration: Spotted dolphins consist of tropical and subtropical species and are widely distributed in all tropical and warm-temperate waters of the Atlantic, Pacific, and Indian Oceans.
White sided dolphin
Striped Dolphin
Physical description
The striped dolphin is slender and streamlined with a well-defined beak. The beak is long and thin and there are about 50 cone shaped teeth on both jaws. The dorsal fin is placed mid-way down the body and is falcate. The pectoral fins are short and the tail fluke has a pronounced notch. Most noticeable are the two very well defined black or blue/black stripes, the first running form the corner of the eyes down to the anal region and the second from the eye to the pectorals. Sometimes these lines are double and there is usually a falcate area under the dorsal fin which also points to the eye. The fins, flukes, beak and jaws are all dark whereas the belly is pale.
Distribution
The striped dolphin is found in tropical and temperate waters of all oceans. In the Atlantic its northern limits are Newfoundland and Greenland. In the Pacific it is found as far North as Hokkaido or Washington. Southwards it is found all around Australia and New Zealand and South Africa as well as off the east coast of South America to the same latitudes. However on the west coast of South America it has not been found so far south. The striped dolphin prefers deep water and is rarely found in coastal areas. It carries out a local migration around the equator in the autumn, travelling towards the cooler latitudes in the spring.
Behaviour
Striped dolphins are very acrobatic, leaping up to 7 metres out of the water. They travel in very large groups of up to 100 individuals and are attracted by ships. Like many dolphins they enjoy bow riding but have a habit of suddenly “streaking” away from the ships. They can attain speeds of up to 37 km/hr, surfacing every five seconds. When travelling more slowly they surface roughly about every 10 to 20 seconds. There is no data at present about their use of sound.
Breeding
The large mixed schools of striped dolphins appear to be sub-divided into smaller breeding or non-breeding schools and mating is seasonal. The calving interval is thought to be about four years. Gestation lasts about 12 months and the young are between 93 and 100cm at birth. Females become sexually mature earliest, between 5 and 13 years, and the males between 7 and 15 years. Their maximum estimated age is 58 years.
Feeding
As one would expect from a species which has such a large range, the striped dolphin eats a large variety of foods. It seems to prefer feeding on shoals of small, deep sea fish, as well as squid and octopus. They can dive to depths of 200 to 700 metres but in the Atlantic their main prey seems to be cod.