Fun at Home - Forensic Beachcombing The challenge = can you work out what predators are living in our oceans just by looking at clues they’ve left behind? Time to do and skill level 10 to 20 minutes to collect and examine cuttlebones, easy to medium if you decide to try and use latex or silicone. Equipment You will need: A beach An adult helper Cuttlebones Ruler or a coin to give your photographs scale A field guide or app to fish or sea creatures in your region (optional) Pouring latex or moulding silicone if you want to reveal some hidden clues (optional) Instructions Step 1 Go to the beach with your adult helper and look around for cuttlebones in the intertidal zone, this the area above water at low tide and below water at high tide. Cuttlefish are closely related to both squid and octopus (Class: Cephalopoda). Their shells, known as cuttlebones, are located just under the skin of their backs. These shells aid in buoyancy control as it contains fluid and air. By changing the balance of fluid and air in the small spaces of the shell, cuttlefish can move up or down in the water column. The shells of deceased cuttlefish are commonly found washed up on beaches. When exploring the beach, I follow these guidelines: I never remove any plants or living animals from the beach, instead I observe and photograph if its safe to do so I avoid walking through the dunes in case I damage plants or disturb nesting birds, I use designated pathways instead I exercise caution when examining shells or discarded drinks cans as they can be housing animals such as the blue ring octopus If I do take something like a cuttlebone home to examine, I will return it to the beach afterwards Step 2 Look closely at the cuttlebone for marks and see if you can identify any as holes left by teeth. The photograph below shows 2 rows of round peg-like holes. These look like the arrangement of teeth that may be found in dolphin skulls and cuttlefish are known to form part of their diet. Step 3 Can you find any teeth marks like this on your cuttlebone? It’s a strong triangle shape, so maybe it could belong to a shark. Step 4 How to get a clearer idea of what’s made the holes? The cuttlebone in the photo below had lots of holes and I couldn’t tell what shape of tooth had made them. I decided to create an impression of them by using some latex. You can get all sorts of pouring latex, or craft silicone that can be used for this purpose. Step 5 I built a wall of plasticine around the toothmarks and poured a thin layer of latex into the holes, once it dried, I continued adding thin layers until I had covered the surface of the cuttlebone. Step 6 I left to dry overnight before peeling off the latex to reveal lots of different teeth. These look like the types of teeth that fur seals and sea lions have. What do you think? Step 7 In the final cuttlebone I examined something had left curved fang-like teeth holes. I used the latex to get a clearer idea of the shape and size of the teeth. If you don’t have access to latex would a modelling clay such as plasticine work just as well? What do you think could have made these marks? A good field guide or an App that can tell you about the sea life in your region can prove very useful when beachcombing. I can’t say exactly which animals have been feeding on the cuttlefish and I don’t know how far each cuttlebone floated on the waves before being washed ashore, but I at least have an idea now of some of the variety of ocean predators out there. Step 8 What beachcombing discoveries have you made? Take a picture if it’s safe to do and use a coin or ruler to give your object scale. Share on Instagram hashtag #museumofthegreatsouthern or Facebook remembering to tag us. This Fun at Home activity is presented by: