Philip Hoare: A stranded whale was once an omen. Today it is a warning

Some existing species are known only from skulls on beaches

The symbolism of the whale runs as deep as the waters in which it swims, as the drama of the last two days has vividly demonstrated. As millions tuned in to witness the Thames whale's fate, it was as if even this noble cetacean had become part of the modern-day media circus. In a sense, the whale has had that role for centuries, if not millennia - ever since the leviathan swallowed Jonah (or indeed, Pinocchio). Our fascination with it is enduring.

The whale world is even bigger and more mysterious than many people might imagine. The order of the cetacea encompasses some 80 species, of both baleen and toothed whales. New species are still being discovered: in July last year, a new species of snubfin dolphin was identified in Australian waters. Some beaked whales - of which the Thames whale is one - are known only from skulls discovered on beaches, the living animals yet to be satisfactorily seen.

These animals - the largest and loudest that ever lived - are mostly a mystery to modern science, a fact that speaks volumes about our hubris as a species.

Since the 1970s, the whale has been an emblem of a threatened planet. The plangent song of the humpback, sung in impenetrable cycles, which may be a cultural expression of brains bigger and perhaps as powerful as our own, was recorded and sent into space on the Voyager probe.

Yet more salutary is new research which has found that bowhead whales may live for 200 years. Each summer I spend eight hours a day off the coast of Cape Cod watching whales. I've seen up to 11 species of cetacea, from white-sided dolphin, to 80ft fin backs, gliding effortlessly under our boat and emerging the other side to spout, drenching me in a fishy atomised cloud.

Nothing prepares you for the first time you see a whale leaping out of the water. More troubling to our modern consciences are the deaths of these animals. Since the international moratorium on whaling was implemented in 1987, Japan alone has killed 7,900 minke whales, 243 Bryde's whales, 140 sei whales, and 38 sperm whales.

Britain was still whaling within my lifetime; anyone born before 1960 probably ate whale in margarine or ice cream, or used it in cosmetics. Norway, which still kills hundreds of minke whales a year, was hunting the northern bottlenose whale in 1973, when the British market for whale meat - used as pet food - was closed. Bottlenoses suffered particularly in the great age of whaling: 22,000 were killed in the last quarter of the 19th century by British and Norwegian fleets.

Although these figures pale in comparison to the greater cetacean holocaust: 360,000 blue whales killed in the 20th century, with fewer than 4,000 now living.

But whaling was undertaken by men out at sea. A stranded whale has historically been the only interface between the public and cetaceans. In England, such animals become "Royal Fish" - as Herman Melville narrates in the ur-text of all cetology, Moby Dick. Indeed, Elizabeth I was known to enjoy whale meat. And 17th and 18th-century engravings of such events - regarded by many as ill omens - show sperm whales with their penises extruded, a final gesture towards its ebbing life.

Our age, too, might take the Thames whale as an omen of a globally-warmed, threatened world. Last month, in the shallow waters off Cape Town, six Arnoux's beaked whales made a similarly unusual appearance. With their mysterious mottled markings, they looked like antediluvian ghosts, come back to haunt a world that has treated these creatures so sinfully.

Joan Smith is away