Though farther south you are already reveling in springlike breezes, the steady accumulation of snow in the northern third of Japan continues to provide an opportunity for detective work.

A fresh fall of snow, on top of the lingering layers of the last few months, provides ideal conditions for a walk in the woods, along the coast or in the mountains. This is the time to use cross-country skis or snowshoes in the backcountry, the mountains and the north.

Fresh snow reveals the movements of the common and the less-common mammals that share these islands with us; they show how common some rarely seen nocturnal animals actually are, and occasionally they pose a mystery to be solved by investigation, further observation and deduction.

Some problems are easy. The dotted lines of single-file tracks are invariably those of a red fox. The closely spaced pairs of tracks beginning a meter or more out from the base of one tree and ending abruptly right at the base of another are those of a squirrel, jumping down to run between trees where there may be food on the ground or where the branches overhead do not provide sufficient support for travel. (The Japanese squirrels of Honshu and the red squirrels of Hokkaido leave similar tracks.)

Some creatures leave bizarre shapes in the snow. I recall the puzzling marks left by a giant flying squirrel, which had landed in the snow like a thrown cushion. The lines of giant K shapes along the snow atop river ice would have had me scratching my head had I not seen a Blakiston's fish owl leave them.

I have gone cross-country skiing in a patch of lowland forest close to Sapporo many times over the last three winters and have hiked there many times in spring, summer and autumn, but I have yet to see a hare there. Nonetheless, each fresh fall of snow brings fresh evidence of their presence; in fact, from their tracks it seems they are commoner this winter than in previous years.

I'd love to be able to look down from above at some of the snow-covered tree branches and see what footprints might be there -- perhaps a palm civet, a raccoon, a marten. Who knows?

The stripped carcass of a deer

Close to the shore of Lake Kussharo in the Akan National Park, about as far removed from the sea as one can be in eastern Hokkaido, I recently came across a sika deer carcass in the snow. The frozen body had been stripped, except for the lower part where it was frozen into the snow.

What had stripped it? The area immediately around the carcass -- a circle about 5 meters across -- had been neatly trampled and tamped down hard, suggesting the coming and going of many individuals. Had it been spring or autumn I might have hoped to find bear tracks nearby, for brown bears are omnivorous and will happily gorge at a deer carcass given a chance. But it was February and the bears were in the midst of their winter sleep.

The next most likely culprit would have been the red fox, the tricky kita-kitsune, but despite circling around the carcass looking for tracks, I found no lines of prints heading to and from the carcass and no signs of chewed ribs or other chewed bones that would have signaled the attention of foxes.

A close inspection of the carcass showed that every scrap of meat had been stripped from the exposed upper half: The ribs were clean, the innards completely removed, even the stomach was eaten -- though its contents, a large green ball of partly digested vegetation, had been left as an untouched frozen mass. How the deer had died, whether of sickness or injury, I don't know, but none of its remains were going to waste.

A fastidious scavenger had been repeatedly at the scene, but just what was it?

The black kite is a common scavenger throughout much of Japan, but it is a weak-billed bird more adept at picking up loose scraps than at picking away at a carcass. There are no vultures in Japan, but all the signs pointed at something equally adapted to efficient scavenging.

In Hokkaido, both Steller's and white-tailed eagles will descend to feast on deer carcasses even in densely wooded areas, and they are often the first to breach a carcass's thick skin. However, once they have taken the easy flesh, they tend to move on in search of further easy feeding. Perhaps an eagle had first found this carcass, but that was not what had cleaned it so thoroughly.

Raven foot and wing prints in the snow

I visited the carcass repeatedly to check on its state and to look for tracks, and on two occasions startled a large black bird, which flew off through the trees. Had I relied on the field guides to identify it, I would have had to write it down as a jungle crow, but those birds, while adept at scavenging around villages, towns, farms and garbage dumps, rarely scavenge in the forest. Furthermore, the calls of the birds that flew away were clear and unmistakable. They were ravens!

Although numerous field guides have recently been published in Japan, they have not kept pace with the sometimes-rapid changes in status and distribution of birds here. Back in 1982, the Wild Bird Society of Japan's guide said of the raven: "A few birds winter regularly on the Shiretoko Peninsula of eastern Hokkaido. Inhabit cliffs at seaside; feed on dead seals and fish."

Six years later, the Japanese Association for the Preservation of Birds' guide said: "Few ravens come to shores with cliffs in north and east Hokkaido during winter."

In 1998, Takuya Kanouchi's "Nippon no Yacho" repeated almost word for word the 1988 information, while "Nippon no Yacho 550," published in February 2000, said: "They come mainly to east Hokkaido in winter; the population changes from year to year. They inhabit shores, near villages, harbors and mountain forests."

It all goes to show that you can't rely on what you read in books -- things change and authors cling to what they know. In reality, the situation has changed dramatically. Based on the field guides alone I could never have guessed at the identity of the scavenger in Akan National Park. In fact, I would have been put off by them. Luckily I knew them to be wrong.

What they should say is that the raven is common to Hokkaido and can be found from its rocky coasts and peninsulas to forested mountains, wherever there is the likelihood of significant carrion (deer in particular, but also seals and occasionally whales). They are shy and generally avoid towns, villages and farms.