BACK in 1860, the vacuum cleaner was invented. A boon to domestic cleanliness, they have since evolved into multi-coloured plastic turbo-boosted wonders. Some have even morphed into robotic autonomous creatures that scuttle about, sweeping up the detritus of our lives. Perhaps they will achieve sentience one night and decide the humans are a form of dirt. Stephen Hawking is very concerned about machines that become too clever …
Nature has already developed its own version of a vacuum cleaner many millions of years ago. We know them as stingrays. They are all aquatic, mainly found in marine waters but there are freshwater species in South America. They range in size from petite frying pan-sized cuties way up to five-metre-long monsters, which live in south-east Asian estuaries, and the huge mantas of tropical oceans. Our local waters are home to diverse range of species.
In nature, form follows function and the rays are perfectly adapted to hunt benthic food. The sea floor is a natural supermarket of tasty treats. Stingrays and sharks are chondrichthyans – an ancient group of fishes with cartilaginous skeletons – no bones. Rays are basically flattened sharks, with eyes on the top and mouth underneath. To get around the problem of not being able to see what they’re eating, the stingrays have a highly developed sense of smell (olfaction), along with an impressive array of electroreceptors. This enables them to sense the electrical fields generated by living prey, even when buried in the mud.
The electric rays have evolved the electroreceptors into a biological battery, capable of inflicting fatal shocks. Even Elon Musk is unable to perform that trick.
Stingrays lack the sharp teeth of most sharks – a series of crushing plates in the mouth being more suitable for dispatching crabs – but instead have a spine or stinger located on the tail. A long, hard, serrated weapon with venom glands and a coating of bacteria-laden slime for good measure provides the rays with protection and possibly offensive capabilities.
A recent worried text from the editor posed a tricky question: “Are stingrays dangerous?” It seems that Catherine and Megan were snorkelling when a ray paid a visit. Our normally fearless editor instantly thought of the late Steve Irwin and her companion formed a good impression of a Polaris missile launch getting out of the water. The spot they were diving has large numbers of stingrays, including the two-metre smooth or bull rays. These huge black beasts are quite common locally – boat ramps and piers usually have several cruising around after the scraps from fish-cleaning tables. You can view 10 or more at the Port Welshpool boat ramp – quite the spectacle.
Inverloch pier had three resident rays until a few months ago when some morons caught and butchered them in some form of “heroic deed”. Fortunately Fisheries Victoria has recently introduced new rules that should help protect our rays from such idiotic behaviour.
Another species – the eagle ray – inhabits our estuaries and coastal waters, pointed flaps and a fine whip-like tail give it a racy appearance. It is capable of powerful high-speed performance; a marine hot rod, if you like. This turn of speed is quite useful as the eagle ray is a favoured food of the orca or killer whale. Some years ago I had the pleasure of watching a pair of eagle rays mating on the beach at Inverloch – splashing away in the shallows oblivious to the hordes of swimmers.
There are other species as well. The fiddle ray, or banjo shark, which is shaped like a banjo, and the shovelnose ray – stingray at the front and shark at the back.
So are these rays dangerous? Any large wild creature needs to be treated with caution, especially in an environment where humans can flounder. I would definitely not try to cuddle one, lest you end up like Steve Irwin with a venom spine piercing your heart. I would also be careful wading in the water – be alert but not alarmed, as someone once proclaimed on a fridge magnet.
View our rays with respect and wonder. Watch their flaps undulate as the glide around – master of their environment – and rejoice that we live in a place where such magnificent natural sights are still commonplace.