Meet the Epaulette Shark

Mini Neptune's Note XIV

Welcome to the Mini Neptunes Notes, a slightly smaller species spotlight for the quirky and the cute creatures who might not be a cetacean, but still deserve to be celebrated on Beached.

Enjoy! 🐙

In shallow waters ranging from northern Australia to New Guinea, there is a marine animal one might be surprised to find resting so placidly on the seabed. In the company of crabs and soles, this little creature is redefining what we thought we knew about sharks. 

I’m referring, of course, to the Epaulette shark. 

Nestled among the reefs, these sweet, spotted fish can dwell at depths of 50 metres, but are more often found in rocky, shallow water where they can put their ‘feet’ to good use. Saying ‘feet’ rather than fins might sound peculiar, and it is! Epaulette sharks have mastered many skills evolution told them they could not, but perhaps the most impressive is their ability to walk. 

Wriggling their bodies and pushing their paddle-shaped fins against the floor, they prefer to travel like this even when the water is deep enough to swim in. Cartilaginous support within an Epaulette shark's fins is reduced and more separated than in other sharks, and it’s this that allows them to rotate their fins for use as limbs. Walking themselves across coral and out into tidal pools, one might worry about their ability to breathe on land. Alas, the Epaulette shark has outsmarted evolution once again.

For these remarkable creatures have also developed an extraordinary ability to cope with severe oxygen depletion. When tidal pools become isolated from the ocean at low tide, oxygen levels can plummet by more than 80%. Yet this is where the Epaulette shark thrives, capable of surviving complete anoxia¹ for up to two hours without issue – a feat only few animals can achieve and those cases are in much colder conditions. They’ve evolved to increase blood supply to their brain and selectively shut down non-essential functions. This means they can stay in the safety of tidal pools for long periods, where predators dare not venture for fear of getting stuck. 

Epaulette sharks are easily recognised by their namesake feature – the distinct, white-outlined black spots behind each pectoral fin, reminiscent of military epaulettes². Typically measuring somewhere between 70 and 90cm, the caudal peduncle of the sharks, to which the tail fin is attached, comprises over half the shark's length. This gives them the appearance of a long, slender body. Adults are light brown with scattered darker spots and subtle bands, providing excellent camouflage. While juveniles sport striking alternating light and dark bands that fade as they age.

When it comes to dinner time, Epaulette sharks are opportunistic predators. Active at dawn and dusk, they use their keen sense of smell and electro-receptive senses to locate hidden prey. All sharks have electroreceptors, which help them to hone in on prey with accuracy. The diet of the Epaulette shark consists of a wide range of small invertebrates and bony fishes. Using their small triangular teeth, they are particularly adept at crushing hard-shelled prey like crabs. As they feed, sand and other detritus are expelled from their gill slits, allowing them to efficiently process their meals.

Reproduction in Epaulette sharks is as equally fascinating as the rest of their story. Females lay 20-50 eggs a year, depositing two egg capsules at a time. Their propensity to breed well in captivity makes them a popular choice in aquariums, and, in recent years, they've made headlines for the rare instance of parthenogenesis – asexual reproduction. This was observed at Brookfield Zoo, and, intriguingly, the only other known instance of parthenogenesis among this species was at the New England Aquarium, where the Brookfield Zoo female had come from! Maybe there actually is something in the water… Though wonderfully unique, outside of the aquarium trade, Epaulette sharks are thankfully of little interest to commercial fisheries. The IUCN has assessed them as a species of Least Concern, allowing them to live undisturbed in water and on land. 

Continuing to surprise and delight marine enthusiasts, these lovely sharks do so much for the reputation of their species, and even make a walking shark seem not so scary!

Tidal pool life. Photo by BBC/Smithsonian Magazine.

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Amie 🐋

1. Anoxia is total oxygen deprivation.

2. An epaulette is an ornamental shoulder piece on an item of clothing, usually the coat or jacket of a military uniform.