Epaulette Shark: The Walking Shark of Eastern Indonesia
Meeting the epaulette shark on a reef flat
The epaulette shark, Hemiscyllium ocellatum, is a small, bottom-dwelling shark that lives in shallow reef water. Its most striking habit is that it walks. It uses its paddle-shaped pectoral and pelvic fins as legs and feet, moving across the sea floor, through sand and between shallow pools, rather than swimming away. Visitors who find one are often surprised by how little it reacts to them and how readily it simply moves on.
The species is reef-associated, with a recorded depth range of 0 to 50 metres, and its distribution centres on New Guinea and northern Australian waters. The ground it prefers is the part of the reef that the tide uncovers, so the way to see one is to understand how the water moves over the reef flat, not to look for it in open blue water.
What the epaulette shark looks like
The species name, ocellatum, refers to the eye-like spots on its body, and these markings are the simplest guide when you are looking at one in the water. The body is pale to brown, with darker markings across the back and flanks. The head is rounded and the snout is short, and the fins are broad and muscular, which is what allows the animal to walk.
Size matters when you judge what you are looking at. Reported maximum length is about 107 centimetres, so a fish on a reef flat is usually a small animal that can be easily mistaken for a wider piece of reef or a patch of rubble until it moves. Take your time when you look into a pool, and let your eyes adjust to the shallow water before you decide whether something is a shark or a rock.
Why the walking shark can stay in shallow water
Walking is useful on a reef flat because the tide regularly drops the water to a depth too thin to swim in comfortably. An animal that can move over the bottom, step over rubble and crawl between pools can remain in the same patch of reef through a full tidal cycle instead of being pushed out to deeper water.
The species also copes with conditions that would stress many other fish. It can survive with very little oxygen for around an hour without ill effects, and it can switch off non-essential brain functions to do so. That tolerance is part of why it can rest in warm, shallow pools where oxygen levels fall during the heat of the day. A pool that looks lifeless from the surface may still hold an animal that is simply resting.
What it eats and when it is active
Its diet is built on small invertebrates. Worms, crabs, shrimp, amphipods and small fishes are the main items, and the animal searches the sand and rubble on the reef flat for them. Food is found on the bottom rather than in open water, which is why the shark spends so much of its time close to the reef surface.
The species is largely nocturnal and is most active at dusk and during the night. It can still be seen searching for food during the day, but its activity increases at low water, when the tide concentrates animals into shallow areas. A daytime visit at low water is the most practical way to see one, and a night visit gives the better view of an animal that is actively feeding.
Timing your outing around the tide table matters more than choosing a particular beach. Check the low-water time before you plan, and arrive early enough to reach the flat while the water is still falling. Once the tide has turned and the pools begin to fill, the best viewing chances are over for that visit.
How to approach without disturbing it
The epaulette shark can be approached quite closely before it swims away, and it is fairly easy to approach, but it will move off if pressed too closely. Approach slowly and stop before the animal starts to move. A shark that retreats into a crevice is one you will not see again that visit.
Do not grab it, corner it or lift it out of a pool. A shark that is trapped against rock or picked up will defend itself, and the person handling it is the one who gets hurt. Let it finish what it is doing and return to its shelter, and watch from a short distance.
Keep your hands and fins off the reef. Walk on sand wherever you can, because coral breaks easily under a foot, and stepping on the flat damages the living cover that the animals use for shelter. Avoid wading into small pools that look empty, since some of them hold animals that are simply keeping still.
For photography, keep a distance of at least a body length and avoid using flash at close range. A quiet pause usually produces better pictures than following the animal across the flat. Patience is the most reliable technique, and an unhurried animal often stays in view long enough to be photographed.
Reading a reef flat at low tide
A reef flat changes character within a few hours. As the water drops, the shallow sections become isolated pools, sand channels and patches of rubble, and each one holds a different set of animals. Walk the edge of the flat first and look into the deeper pools before you cross open sections, because the animals tend to remain where there is cover and water to wait out the falling tide.
Pay attention to the bottom as well as the water. A sandy channel between coral heads is easier to read than a bed of broken rubble, and an animal that is walking leaves a clearer track than one that is still. Look for disturbed sand, a fin resting on the bottom or a patterned body partly hidden under a ledge, and then stop to let the scene settle before you look more closely.
Keep the tide in mind during the whole visit. Water that is falling is leaving the flat in a predictable way, so the pools you pass early will be shallower and busier later on. Plan to leave the flat before the tide begins to rise quickly, so that you are not caught on coral in a current or wading in deeper water than you expected.
Keeping the reef flat intact
The epaulette shark depends on the same shallow flats that people walk across at low tide. Damage to those flats, from trampling, from anchors and from the removal of coral, affects the animals that shelter and feed there. Looking after the reef flat is the most direct way to look after the shark.
The simplest rule is to leave the animal where it is. Do not take it from the water, and do not keep one in a container or a pool. An animal removed from its pool is handled roughly and kept in conditions it cannot live in for long. If you see one, take a photograph, make a note of the location and move on.
Planning a reef visit around the shark
If you are travelling in Papua, the epaulette shark fits into a wider wildlife plan. The Papua region guide is the right place to plan the rest of a trip around reef days, including the choice of base and how far to travel between sites.
Reef days also suit a snorkelling plan. The coral reefs of Bali page describes what a healthy reef looks like, which is a useful comparison when you judge the condition of the reef flats you visit elsewhere. For choosing a place to swim and reading conditions on the day, the Bali snorkelling spots guide is the practical companion.
Wear reef shoes if you walk across rough coral, and carry a torch with a red or dim filter for night outings so that the animals are not dazzled. Move slowly, and let your eyes adjust before you look for detail in a pool.
What to expect on your first encounter
Expect a small, unhurried animal that is more interested in its own patch of reef than in you. The first sighting often happens when you least expect it, as a patterned body moves under a ledge or a fin lifts off the sand. Stay still, let the animal settle and watch how it uses its fins. That walking behaviour is the reason the species is so memorable, and watching it is the best part of the encounter.
Related guides: conservation pressure on grey reef sharks, Zebra Shark: Spotted Reef Shark of Indonesian Waters, Sharks and Rays of Indonesia: Species, Habitats and How to Choose.