Invertebrates nocturnal

Flathead Lobster

Thenus orientalis

Meet the shovel-headed master of the seafloor. The Flathead Lobster is a marvel of evolution, perfectly designed for a life of stealth and excavation in the sandy depths.

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Quick Identification

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Size

Typically 15-25 cm (6-10 inches) in length; weighs approximately 150-500g (5-18 oz).

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Colors

Mottled brownish-grey to tan with reddish-brown speckles; the underside is typically a pale cream or off-white.

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Key Features

Extremely flattened, shovel-like body shape
Broad, plate-like antennae used for digging
Eyes set wide apart at the outer edges of the head
Lacks large pincers or claws found in other lobsters

When You’ll See Them

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Activity pattern nocturnal

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Peak hours 10 PM - 4 AM

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Season Year-round

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Diet A carnivorous scavenger that targets small fish, mollusks, marine worms, and other small crustaceans found within the sediment.

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Habitat Soft-bottomed marine environments including bays, estuaries, and continental shelf waters with sand or mud substrates.

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Behavior

The Flathead Lobster, frequently known as the Moreton Bay Bug, is a master of camouflage. Unlike their more aggressive clawed cousins, these lobsters spend most of their daylight hours buried just beneath the surface of soft sand or mud. They use their specialized, shovel-shaped antennae to excavate shallow depressions, leaving only their eyes and the tips of their antennae exposed to monitor for predators or passing prey.

When night falls, these crustaceans become active foragers. They move with a rhythmic, crawling gait across the seafloor, but are capable of a rapid backwards retreat—powered by a strong flick of the tail—if they feel threatened. While generally solitary, they can often be found in high densities in areas with nutrient-rich sediments. They are relatively docile toward humans but are highly sensitive to vibrations and sudden light changes in their environment.

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Camera Tips

Capturing the Flathead Lobster requires an underwater camera setup, such as a waterproof drop-cam or a pier-mounted system. To maximize your chances, place your camera housing directly on the seabed in areas with soft, sandy, or silty bottoms. These lobsters prefer 'benthic' life, so a camera angled 10-20 degrees downward from a weighted tripod or a low-profile flat base will provide the best view of their specialized digging behavior.

Bait is essential for bringing these shy scavengers into the camera’s field of view. Use a mesh bait bag filled with oily fish scraps, such as mullet or sardines, and secure it roughly 1-2 feet in front of the lens. The scent trail will draw them out from their buried positions. Because they are nocturnal, you will need a camera with strong infrared (IR) capabilities or low-glow LEDs. Avoid using bright white light, as this can cause them to retreat or attract large predatory fish that might knock your equipment over.

For the best video results, set your camera to a high frame rate to capture their unique 'tail-flick' escape response. If you are using a triggered system, set the sensitivity high, as their movements can be slow and methodical while foraging. Seasonal success often peaks during the warmer months when their metabolism is higher, though they can be filmed year-round in tropical and subtropical waters. Always ensure your camera tether is weighted to prevent tidal currents from shifting your frame away from the bait station.

Similar Species

Species that look similar or are commonly confused with Flathead Lobster.

Slipper Lobster

Slipper lobsters have a more rounded, humped body and their eyes are positioned closer together rather than at the extreme edges of the head.

Shovelnose Ray

While also flat and sandy-colored, the Shovelnose Ray is a fish with a long tail and visible fins rather than a segmented crustacean shell.

Frequently Asked Questions

Flathead Lobsters are strictly nocturnal. They spend the daylight hours buried in the sand and emerge shortly after sunset to forage for food, with peak activity occurring during the darkest hours of the night.

If you live on a coastal property with a pier, use a waterproof drop-cam. Attract them by placing a bait cage filled with crushed shellfish or oily fish scraps directly in front of the lens on a sandy seafloor.

They are opportunistic carnivores and scavengers. Their diet consists mainly of small bottom-dwelling fish, marine worms, and bivalves which they uncover by digging in the silt.

They are common in coastal suburban areas with access to saltwater bays and estuaries, particularly in the Indo-Pacific region, though they are rarely seen unless you are looking underwater.

While both are flat, the Flathead Lobster (Thenus) has its eyes located at the far corners of its head shield, whereas most Slipper Lobsters (Scyllarides) have eyes located closer to the midline.

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