Clams may look small in the paws of a grizzly bear, but they're still worth all that effort. Early autumn two months to go before hibernation, and the bear's appetite steps up a gear. A seasonal change in the bear's physiology now allows him to eat continuously without ever feeling full, a huge advantage during the berry season. They may eat as many as , berries a day. And that gives the next big boost to a bear's energy reserves. But at this time of the year they'll eat whatever they find. After three months of counting calories, they're back in shape. For these grizzly bears in Alaska, the real test is about to begin. With luck, they will have put on enough weight to enable them to survive the coming five to six months of winter. They will only have done so by being extremely unfussy feeders. BLOODSTOCK RADIO The lifestyle of a generalist may seem a good strategy, but from an evolutionary perspective, there's always the temptation to specialise. In India, there's another bear happy to tackle anything remotely edible it comes across. But that is only for half the year. This bear, the sloth bear, has started down the road to specialisation. Inside this mound of clay lies a huge quantity of food, and the sloth bear has just the right equipment to collect it. It has particularly large claws, perfect for breaking into these sunbaked termite mounds. It's worth the effort, for just one colony may contain a million individuals. The termites' first line of defence has been broken. Faced with such a large and destructive predator, there's little the soldier termites can do to drive the bear away. As the termites swarm over their smashed mound, the bear hoovers them up. But the greatest prize are the larvae that lie inside the nest. The bear has other adaptations as well as big claws. It's lost its two front teeth, so by pursing its floppy lips into a tube, it can suck insects directly into its mouth. At the end of its snout, there's a flap that prevents dirt and dust going up its nose at the same time. But the sloth bear may be heading for danger; the same danger that may before long exterminate its cousin, the giant panda. For the moment, however, there's no shortage of termites, and the sloth bear has still not become as wholly reliant on them as the giant panda is on Radio. Just as humans have had an impact on the giant panda and its food, so they have on the sloth bear. In India, sloth bears live alongside people, and conflict between the two is common, resulting in hundreds of maulings every year. BLOODSTOCK RADIO During the day, bears take refuge in areas not used by people. Sloth bears may not compete with cattle for food, but land turned to grazing reduces the bears' termite harvest. Loss of natural habitat has had a serious impact on wildlife across the globe, but, ironically, manmade habitats have provided new opportunities for many omnivores. The modern city, a seemingly sterile world of concrete, steel and glass. It must be one of the most difficult places for a wild animal to make a living in. It would be, if not for the extravagant habits of the people who live here. The largest cities may contain more than ten million human inhabitants.