Big animals of Palau and Truk Lagoon

Diving with large animals in general is pretty safe. Never threaten or deliberately disturb fish - especially in the company of young - and you’ll be OK. Watch out for "nervous" or stressed animals.
The power of dolphins, sharks and other large sea creatures deserve respect.

As a rule don't touch or grab marine life, potentially dangerous or not.

Black tip reef shark (Carcharhinus melanopterus)
Size: 1 to 2 meters long.
Habitat/Behavior: The blacktip reef shark is probably the most encountered of the reef sharks. It occurs singly or in small schools and is easily recognized by the bright blacktiped fins, especially the first dorsal fin which has a contrasting white band beneath the black top. The blacktip might be small in size compared to other sharks, but should not be taken for timid or harmless. At the presence of food, bait or when fishermen are clearing their catch the shark will show its aggressiveness and not hesitate to attack.

Reaction to Divers: Wary to inquisitive

Grey reef shark (Carcharhinus amblyrhynchos)
Size: 1 to 2 meters long.
Habitat/Behavior: This is the most common shark around Palau and Truk Lagoon.
The grey reef shark is of the same size as the blacktip, and is thought to live as long as 25 years. The grey reef shark should just like the blacktip, be approached with precaution. When startled or approached too fast the shark will display a series of threat postures that consists of exaggerated and jerky movements. With arched back, raised snout and lowered pectoral fins the shark shows the intruder that he better stand back.

Reaction to Divers: Unaggressive, will stay away.

More information: http://www.elasmo-research.org/

White-tip Reef Shark (Triaenodon obesus)
Size: 1 to 2 meters long.
Habitat/Behavior: Found throughout Micronesia, often resting under ledges. Closely associated with the ecosystem of the coral reef, it generally lives in surface waters.
They feed alone or in groups during dusk and nighttime. Only dangerous during feeding frenzy disturbance.

Reaction to Divers: Unaggressive, largely indifferent.

Leopard shark (Stegostoma fasciatum)
Size: 1 to 2 meters long.
Habitat/Behavior: Docile shark. A bottom dweller, that feeds on benthic prey such as worms, smaller fish and crustaceans. Has small pointy teeth, but is harmless.
Sometimes called cat shark.

Reaction to Divers: Unaggressive, harmless.

More information: http://www.underwater.com.au/

Scalloped hammerhead (Sphyrna lewini)
Size: 1,5 to 4 meters long.
Habitat/Behavior: Found schooling on submerged seamounts near wall and open ocean currents. Rocky pinnacles seem to serve as reference points for nocturnal hunting.

Reaction to Divers: Wary to inquisitive while milling about in small to large schools. Hammerheads are often spooked by diver bubbles.

Whale Shark (Rhincodon typus)
Size: 5 to 15 meters long.
Habitat/Behavior: Occasionally spotted throughout Micronesian waters, usually filtering out plankton in the top layer of water.
The whale shark is up to 46 feet (14 m), weighing up to 15 tons. The average size is 25 feet (7.6 m) long It is the largest fish in the world. Females are larger than males (like most sharks).
Whale sharks can dive to a depth of more than 1000 metres and swim for hundreds of kilometres between feeding sites.

Reaction to Divers: Generally indifferent, although diver bubbles or attempts to ride the shark may cause it to move away.

Giant Manta ray (Manta birostris)
Size: 6 meters wide (maximum).
Habitat/Behavior: Found throughout Micronesian waters. Most often spotted at moderate depths in open ocean, or near the surface in coastal waters.

Reaction to Divers: Often curious when not directly approached.

Coconut crab (Birgus latro)
Size: 50 cm from claw to claw.
The immense Coconut Crab (or Robber Crab) is the largest terrestrial arthropod on earth, (Grub 1971). They have been found to attain weights in excess of 5kg (Fletcher & Amos 1994) and can span over 50cm from claw to claw, (Reyne 1939). They are very powerful creatures and have vastly strong pincers. These ‘chelae’ can easily cut through an ordinary broom handle, (Johnson 1965).

Habitat/Behavior: This species is a type of land hermit crab with a spectacular appearance and intriguing biology. It is the largest terrestrial arthropod in the world and is able to grow to relatively gigantic proportions. Unlike most other hermit crabs, only the juveniles of this species find and use gastropod shells for protection as they develop. Adults have abandoned the shell-carrying habit, and instead have hardened shells over the abdomen. This protects the crab, reduces water loss and does not restrict its growth, allowing it to reach up to a metre in size. This huge crustacean is well adapted to life on land with long strong legs. It also has large muscular claws which are used for punching holes in coconuts and scooping out the flesh. This is a unique behaviour amongst crabs and explains why this species is called the coconut crab. The claws are in fact so powerful they can lift objects such as vegetation or rocks weighing up to 28 kg. Its stalked eyes are red, and this crab’s body colour varies between islands from purplish-blue to orange-red. Studies show that males are considerably larger than females.

The Coconut crab is a rare and endangered animal. Do not eat the crab as a delicacy in restaurants. (Common up to 2002) Various conservation projects have been started around the world to save this large and unique arthropod.

More information on the Coconut crab from scientist William Murdoch.
Reaction to people: Shy and will evade all humans when it can. Not fast.