As you enjoy a relaxing stroll along one of our sandy beaches it’s likely you are passing some vital clues to the presence of cold-blooded killers. But don’t worry! It’s not you they are after…

First clue (naturally) is a body; or in this case bodies! The remains of the victims may be obvious: bivalve shells like pipis with neat round holes in them. If the tide is out you may see another clue: squiggly tracks in the wet sand each ending in a lump. In the right months leathery collars embedded with sand, or clear, kidney-shaped jellies also provide a clue to the identity of the killers.

The killers are Sand Snails, active hunters that plough their way through the sand just below the surface. Each has a large foot which folds back over its head and pushes sand aside as the animal crawls. Tentacles on the snail’s head sense chemicals in the water to find its prey.

When it comes in contact with a pipi or other bivalve the snail grasps it with folds of its foot and produces an acid which helps soften the shell. It can then be drilled by the Sand Snail’s rasp-like tongue. The killer then inserts its tube-like proboscis into the prey and devours its victim.

If you come across the track of a Sand Snail and carefully uncover the lump at the end you may get a glimpse of the animal’s large foot before it pulls it back inside the smooth round shell.

There are several species of Sand Snails common in our area. The Conical Sand Snail (Polinices conicus) is a honey-coloured, pear-shaped shell with a brown or orange band along the top of each whorl. It grows to 42mm and is found on sand flats of sheltered beaches and estuaries. Polinices incei grows to about the same size but varies in colour and is rounder. The Sordid or Leaden Sand Snail (Polinices sordidus) prefers the more muddy conditions of estuaries. Its shell, which grows to about 36mm, varies from grey to brown with an orange outer lip.

All these snails lay eggs in kidney-shaped egg jellies, sometimes called horseshoe jellies. If you hold one up to the light you will see spots inside which are the tiny eggs.

Another Sand Snail common on ocean beaches is Polinices didymus (or Neverita didyma) whose light honey-coloured shell can grow to 65mm. It lays its eggs in a sand collar.

Eggs from the jellies and sand collars hatch into tiny larvae which spend some time in the plankton before settling out as baby snails.