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Showing posts from October, 2013

Marine Mammals: Dugongs

Shy and retiring, dugongs are marine mammals that spend their days feeding in the shallow waters of reefs and along coastlines in the Indian Ocean, the Indonesian archipelago, and the southwestern Pacific around the Philippines. Even though they resemble a cross between a seal and a walrus, dugongs are more closely related to elephants. The slow-moving mammals are easily identified by their triangular, whalelike tails, broad trunklike snouts, and long bodies, which reach 9 feet (2.7 m). Dugongs have a thick layer of blubber under their skin, a feature that gives them a round-shouldered look. Their mouths look like vertical slits on their upper jaws, and their flippers are small and paddle shaped.
Dugongs have unusually slow metabolic rates for mammals but function well in their warm water environments where they float and feed, expending very little energy. With very few predators and plenty of food, migration and other energetic types of behavior are not necessary. Most of their tim…

The minke whale (Balaenoptera acutorostrata)

The minke whale (Balaenoptera acutorostrata) is the second smallest of the baleen whales, measuring about 32.8 feet (10 m) in length. A distinctive triangular head, narrow and pointed snout, and sickle-shaped dorsal fin make this whale easy to identify. Generally, minke whales are black, gray, or brown on their dorsal surface and a light color on their ventral surface. These active, agile whales have good maneuverability and speed, able to travel at 10.4 miles per hour (17 kph) for short periods of time.
As baleen whales, minkes are carnivores whose mouths are equipped with smooth baleen plates for filtering small organisms from gulps of water. Minkes can be found worldwide and are known to live in deep oceans, along coasts, and in coral reefs. Instead of seasonal migration, they only travel to follow their food. Sometimes minkes chase schools of small fish such as sardines and herring, swimming beneath and scooping them up in their open mouths. As in humpbacks, the throats of minkes …

Humpback Whales

The humpback whale (Megaptera novaeangliae) is much bigger than the spinner dolphin, measuring 40 to 50 feet (12.9 to 15.2 m) long and weighing up to 55 tons. The common name humpback describes the motion this whale makes as it jumps out of the water. A typical humpback whale is black on the dorsal side, with a white ventral surface and distinctive 15-foot flippers on the sides of its body.
The head of a humpback whale is large in proportion to the rest of its torpedo-shaped body. This figure below shows that the mouth line runs high along the entire length of head, and the eyes are set above the ends of the mouth. The small ear slits are located behind and below the eyes.
On the top of its head, a humpback has a raised area in front of its two blowholes that functions like a splashguard to keep water from flowing back into the holes where it breathes. Rounded knobs called tubercles are also located on the head, often on the upper and lower jaws. Each tubercle contains a hairlike str…

Spinner Dolphins

Spinner dolphins (Stenella longirostris) are easily spotted as they swim in the clear waters of coral reefs. Named for their ability to spin during acrobatic jumps, these dolphins are slender, with long thin beaks, sloping foreheads, and a stripe that runs from the eyes to the flippers. An adult measures 4.25 to 6.89 feet (1.3 to 2.1 m) long, and weighs between 100 and 165 pounds (45 and 75 kg). There are several varieties of spinners in different geological locations, and they vary slightly in shape and color.
Spinner dolphins feed at night on fish and squid in the deeper waters of the reef, although they will also eat organisms that live on the reef floor. Their mouths are equipped with 45 to 65 pairs of sharp teeth in each jaw. After feeding, spinner dolphins can often be found resting in protected areas of shallow water.
As social animals, spinners depend on interaction with others for hunting, defense, and reproduction and form small, long-lasting social groups called pods. In thi…