Another Life: A beachcombing reader, Rhoda Twombly, has the luck to live on a small Atlantic island - Inishlyre, tucked in behind the other drumlins of Clew Bay, Co Mayo, but still washed by westerly storms, writes Michael Viney.
Walking the tideline the other morning, she happened on a little castaway: an octopus, less than 30cm including tentacles. It was still alive, but "rather deflated and pale - a rather pinky-white". She put him back in the water, whereupon "almost immediately, he turned a deeper brown-red and his body inflated. He unravelled his tentacles and seemed happier. Just seeing this pretty fellow made my day!"
Twombly didn't know we had octopuses (that's the plural: "octopus" is Greek, not Latin); nor do a lot of people. Octopuses are meant to be Mediterranean, with chewy bits savoured at the bar. I kidnapped my first octopus on a snorkel dive off a Greek island. Deposited on the jetty, it promptly ran away and dived off the end.
Octopuses are every bit as bright as cats or dogs. They have the biggest eyes and most complex brains of any invertebrates, learn to solve problems by trial and error, and remember what they've learned. A pair of Irish divers from west Cork once made a "pet" of an octopus off Gibraltar, persuading it to come out of its hole to take food from their hands. Worried about attracting sharks, they began to take the food down in a small, sealed box. No box and the octopus wouldn't come out. Then it snatched the box and stayed in indefinitely, working out how to open it.
Ireland does have the common European octopus (Octopus vulgaris), but only off the south coast. That, at least, has been its northern limit, but the changing climate may well draw it up the west coast. Know it by its size - up to 70cm overall - a distinctly warty body, and two rows of stout suckers on its tentacles. The "native" species, found all round the island, are much smaller.
Twombly's castaway was probably the curled octopus (Eledone cirrhosa), no bigger than 50cm and with single rows of suckers, while the North Atlantic octopus (Bathypolypus arcticus) is no bigger than a man's palm. The first is worth watching for in any good-size rock pool, especially after a spring tide. Neither, however, is welcome in a lobster pot, since lobsters and crabs are their prey.
There's a lot that fascinates about octopuses - and, indeed, their relatives in the cephalopod clan, the cuttlefish and squid. They are all classified as molluscs, having evolved from the same basic design as oysters or periwinkles. They've lost the original external shell, the "foot" has divided into tentacles around the mouth, and the mantle cavity has become a pump for water-powered jet propulsion.
Where the rapid and often continuous colour-changing came from is harder to say, though how it works is clear: the expansion, contraction - and, when needed, pulsation - of millions of chromatophores, multi-cellular organs under neuromuscular control and acting on cells full of pigment.
The octopus famously shows its emotions through changing the colour, patterns, even texture, of its skin. The cuttlefish uses colour for camouflage, but in the throes of courtship it shimmers and flickers in dazzlingly rapid sequences. Its most arresting display, used when attacking prey, bathes the body in shifting stripes to blur its shape and motion (see drawing).
In the cuttlefish, the original mollusc shell has become an internal, porous structure used like a submarine's tanks. Filled with water by day, it sinks the animal to the sand; pumped out and gas-filled at night, it buoys it up to start hunting. This is the white, oval cuttlefish "bone", brittle and feather-light found at the tideline and famously fed to caged budgerigars.
A few years ago, whole armadas of cuttlefish "bones" arrived on western shores from some unguessably fatal event further south. Most were of the common European species, Sepia officinalis, with a mantle around 30cm long. Cuttlefish in general are expected to spread northward around Ireland and become far more abundant as the sea warms.
Cuttlefish are mainly animals of the shallows, but the North Atlantic octopus ranges down to 600m. In the real deeps, indeed, octopuses are the dominant cephalopod species. Down in the dark they've no use for clouds of ink with which to confuse attackers. They do, however, have little fingers on their arms, as well as suckers, all the better to hold on to their prey.
My column on January 26th wrongly described the brilliant blue Pulcherricium caeruleum, found on a furze bough in Cork, as a lichen. It is actually a fungus: my apologies to Vince Giavarini, to whom I attributed the error.
Eye on Nature
I've been watching a flock of about 20 young magpies flying backwards and forwards from the high trees in my garden to other high trees about two gardens away, all of which overlook the Dodder. They're doing it in groups of two or three at a time, and look like they're on test flights. It all seems very co-ordinated and organised. Are they just practising, or is there some other reason for this behaviour? Irene Furlong, Dublin 6W
It may have been a spring gathering, showing off for pair formation.
The number of chaffinches visiting our garden this year is phenomenal. Cratloe Woods are alive with them. But there are fewer sparrows than hitherto, and wagtails seem to have greatly increased in numbers. Pádraic Breathnach, Limerick
My brother in Cork had frogspawn in his pond on December 25th. Mark Shorten, west Cork
People with tadpoles in containers should add some wild watercress to the water to provide iodine to aid their transformation into frogs. Tadpoles thrive on beef mince administered very sparingly. And tanks should be siphoned clean every so often. Jane King, Rathmore, Co Kildare