It is common to see dolphins in Bunaken National Park. There are 28 different types of whales and dolphins that have been seen in the park, however they are shy animals and most of the times we see them in the surface rather than diving.
When we do see them then often it is in very large schools of 50-100+ animals, as in the photo on the right.
Here a little bit more information about these amazing animals!
They are mammals of the order Cetacea and the families Plantanistidae and Delphinidae and include about 50 species. All have a beak like snout and sharp, conical teeth.
Most dolphin species are about 6 ft in length, the males averaging 4 to 8 in longer than females. The largest is the killer whale, which can be 19-22ft long and weigh between 8000-10000lbs.
Dolphins feed on live food and are predators, except when trained otherwise in captivity. The primary food is fish, mostly things like herring, mackerel, and sardines. Some species seem to prefer squid, occasionally, shrimp and other crustacean are consumed, and even mollusc shells have been found in their stomach contents.
The body is sleek and smooth and the hairless skin is rubbery to the touch. Most species have jaws that protrude into a beak like snout. Above the upper jaw is a large mass of fat and oil-containing tissue forming the so-called “melon” that looks much like a bulging forehead.
The anterior appendages contain the skeletal remnants of five digits that form the flippers, which the animal uses primarily as stabilizers, although occasionally in an oar like fashion. The hind appendages are virtually absent and consist of a pair of small pelvic bones, deeply embedded in the connective tissue at the base of the tail. The dorsal fin is formed from subcutaneous dermal tissue and is not movable by muscle action. The caudal, or tail, fin is also primarily dermal in origin, rather than skeletal, and consists of a pair of horizontally extending flukes.
The locomotion of dolphins is typical of the whale. The main thrust comes from vertical oscillations of the tail and flukes, and most species tested are capable of sustained swimming speeds of up to 18.6 mph and they jump at this high speeds travelling 30 ft or more. Their normal “cruising speed” is about 23 to 25 mph, and if they are bow riding, they have been known to get up to 30mph (bow riding is when the dolphin rides the front bow wave produced by a boat/ship).
Because dolphins are mammals, they must breathe air and maintain a high body temperature. The internal temperature, between 97.9 deg to 99 deg F, is acheived by a thick layer of blubber under the skin. Air is breathed through blowhole, situated almost directly on top of the head. The dolphin normally come to the surface to breathe about every two minutes, and each breath consists of a short, almost explosive exhalation, followed by a slightly longer inhalation. Dolphins can hold their breath for up to several minutes and are capable of rapid and deep dives of more then 1,000 ft.
Mating normally occurs during the spring months, like with most animals, with the male-female pair exhibiting courtship for some time prior to the actual mating. A female dolphin has to carry her baby (calf) for 11-12 months. The calf is delivered normally tail first, and the newborn is capable of swimming and breathing within the first minutes. The calf will follow its mother closely, and suckling takes place frequently, with the mother tolling slightly and the calf nuzzling the mammary area. The dolphin’s two mammary glands open into a pair of sacs on either side of the anal opening, and the calf’s beak fits into the openings on the sacs. The nipple is grasped between the upper jaw and the tongue, and muscular contractions by the mother literally squirt mil into the calf’s mouth. Nursing may continue for as long as 12 to 18 months after birth, although weaning is probably slowed or inhibited in captive animals.
Dolphins are extremely and almost constantly vocal. They are capable of two kinds of sounds. A specialized mechanism in the nasal passages just below the blow-hole enables them to emit short, pulse-type sounds. These sounds, called clicks, can be produced in such rapid succession as to sound like a buzz or even a duck like quack. The clicks are used as a form of sonar, in which echoes of sounds from surrounding objects enable the animals to detect obstacles, other dolphins, fish, and even tiny bits of matter in the water.
Despite having a face that looks strangely like that of a disgruntled weasel, the Whitetip Reef Shark (Triaenodon obesus) is generally unaggressive toward humans who invade its environment. Although it often rests in caves during daylight hours, this species is probably the most commonly-encountered shark of the tropical Pacific. Indeed, for many divers and snorkellers, the phlegmatic Reef Whitetip is their only ambassador to sharkdom.
Despite its formal species name, obesus, the Whitetip Reef Shark is rather slender and delicately built. This body form grants it the ability to slither, eel-like into crevices in the reef, where this species is an absolute master at extracting prey. Quiescent during the day, Whitetip Reef Sharks become active and determined hunters at night. Moving over the reef face in loosely organized packs, these sharks systematically poke their blunt heads into each crack and crevice in the reef face in search of prey. Known prey of the Whitetip Reef Shark includes sleeping diurnal teleosts or hiding nocturnal creatures such as octopuses, soldierfishes, wrasses, and trumpetfishes, which are grasped with its small, tricuspid teeth. Using its ampullae of Lorenzini and uniquely tube-flapped nares, the Whitetip Reef detects its prey primarily by bioelectrical cues and scent. When a hunting Whitetip Reef locates a prey animal within a hole in the reef face, it violently twists and turns to push itself deep into the crevice. Some sharks actually squirm into a hole in one side of a coral head and exit through an opening on the other. During these zealous foraging bouts, Whitetip Reef Sharks have been observed breaking off pieces of coral — sometimes tearing their skin and fins. Although they are primarily nocturnal, Whitetip Reef Sharks can and do feed opportunistically by day.
In addition to electrical and olfactory cues, the Whitetip Reef Shark is also highly responsive to sounds and vibrations. In experiments conducted at the Marshall Islands and French Polynesia, Whitetip Reefs consistently responded to recorded sounds of struggling fish, feeding sharks, and even vocalizations of teleosts. At Eniwetok Atoll, Marshall Islands, artificially generated sounds were found to be most attractive to Whitetip Reef Sharks when they combined low frequency (25-100 Hertz) with varied intermittent pulses every 7.5 to 15 seconds. These sound characteristics correspond well to the irregular sounds and vibrations generated by a fish struggling on the end of a spear or on hook and line. In South Pacific areas where spearfishing is common, Whitetip Reef Sharks respond very rapidly to the sound of a speargun discharge, typically appearing within seconds. Although normally quite placid, this inquisitive species can become persistent and bold when faced with a diver playing or carrying a speared fish — sometimes dashing in to tear an impaled fish from the spear tip.
Due to the abundance of Whitetip Reef Sharks in coastal areas of the tropical Pacific and Indian Oceans, day-to-day life of this species is better known than that of most sharks. Whitetip Reefs are most often encountered during daylight hours while they rest quietly in underwater caves throughout much of the tropical Indo-Pacific or in lava tubes of Hawaiian reefs. But in some locations — such as at Cocos Island and near-shore waters off the Pacific coast of Costa Rica — this species is often seen lying stretched out on the sandy bottom, completely exposed in broad daylight. Sometimes, several of these gregarious sharks are seen lying side-by-side or even stacked on top of one another, like cord-wood. The significance of these diurnal al fresco gatherings is not known, but may have something to do with these sharks being cleaned by small wrasses and at least one species of goby.
The Reef Whitetip is one of the three most common sharks on Indo-Pacific coral reefs, the other two being the Blackfin Reef Shark (Carcharhinus melanopterus) and the Grey Reef Shark (Carcharhinus amblyrhynchos). Although these three sharks are widely distributed over the vast expanse of the tropical Pacific and Indian Oceans, their relative distribution over the reef profile is remarkably uniform from place to place. Blackfin Reef Sharks, especially juveniles, are typically found closest to shore, inhabiting the turbid lagoon shallows over sandy plains at depth from 0 to 50 feet (0 to 15 metres). Juvenile Grey Reef Sharks are found in the clearer, deeper waters of the back reef, while adults of this species typically patrol the reef crest and fore reef from the depth of about 65 feet (20 metres) down to a depth of about 330 feet (100 metres). Both species are most active at dawn and dusk, accomplishing most of their feeding during these twilight hours when schooling diurnal fishes are most vulnerable.
Neatly nestled between the crepuscular Blackfin Reef and Grey Reef sharks, Whitetip Reefs typically haunt the reef flats and shallower parts of the fore-reef at depths of 35 to 100 feet (10 to 30 metres). Although it can extend its range from the intertidal to at least 130 feet (40 metres), the Whitetip Reef manages to coexist with the Blackfin Reef and Grey Reef Shark by feeding primarily at night and specializing in extracting prey from cracks and crevices in the reef face that are all but inaccessible to these other sharks. By inhabiting different depths and ecological niches, the slender, weasel-faced Whitetip Reef Shark reduces competition for food resources with other sharks sharing its habitat.
Maturity: unknown; at least 5 years in both sexes
Mode: viviparous, with a yolk-sac placenta
Gestation: 13 months
Pups: 1-5 (usually 2-3), probably every two years
Juvenile: small teleost fishes, crabs, octopuses
Adult: teleost fishes, crabs, octopuses
Habitat: Sandy Plains, Rocky Reefs, Coral Reefs, Deep Sea
Depth: 3-1080 ft (1-330 m), often at 26-130 ft (8-40 m)
Distribution: Central Pacific, South Pacific, Tropical Eastern Pacific, Southern African, Madagascaran, Arabian, Indian, South East Asian, Western Australian, Northern Australian, Japanese
These beautiful cuttlefish get their name from the flamboyant pink, yellow and black ripples they make with their bodies when alarmed.
This small cuttlefish is just 8cm (3in) in length.
They are found in northern Australia and Indonesia.
A tropical species with limited distribution, it is found on the seabed in shallow waters.
Small fish and crustaceans.
Active in the day the cuttlefish uses vision to detect its prey. It’s capable of rapid colour change that might be used to confuse predators or prey.
Like other cephalopods, the flamboyant cuttlefish breeds once and then dies.
Great morning dives, four sea horses, octopus (eating a crab), demon stinger scorpionfish, zebra batfish ( the juvenile!), robust pipefish… and two hairy frogfish!!Great last dive for Flavia!
Back in February 2010, we had a group of Scandinavian divers who informed us of the existence of the ‘Tongue Eating Isopod’ – you may remember Anna’s photograph from the our ‘ Did You Know’ blog ( http://divinglembeh.wordpress.com/2010/03/28/did-you-know-2/) . One of the group was Bent Christensen, an Aquatic Ecologist and avid (and very talented) underwater and land photographer who has recently informed that he will be coming back to “to document the parasites further” . Even though he plans to spend a lot of time sitting at anemones, staring into the mouths of anemone fish as they try and bite him ( they are just protecting their anemone!) we are sure that he will spend some time enjoying some of the other critters that we have here in Lembeh and also to see if any of the other fish have a tongue-eating parasite living in their mouth!!
If you would like to check out some more of Bent’s photos from his stay here at Two Fish Lembeh and also at Two Fish Bunaken then follow the link to http://www.pbase.com/borneobent/sulawesi_2010 .
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