Most restricted diet for a bear

The most restricted diet of any species of bear is that of China's giant panda Ailuropoda melanoleuca, more than 99% of which consists of bamboo shoots and leaves. The remaining <1% consists of other types of plant material, plus occasional carrion, small birds or rodents. It will also eat eggs, fruit, honey and even fish when maintained in captivity.

Despite their predominantly herbivorous diet, giant pandas still retain a carnivore-based digestive system (simple stomach and short gastrointestinal tract), as well as certain carnivoran-specific genes, and actually derive little nutritional sustenance from bamboo, which is a very poor source of protein and energy. This means that they need to eat large quantities of it in order to remain healthy – up to 14 kg (30 lb) of bamboo shoots and leaves per day. To meet the nutritional challenges, they adjust foraging by switching from leaves to shoots of wood bamboo in spring, and in summer they move to higher elevations to supplement with shoots of arrow bamboo that mature later in a season. The two bamboo species are nutritionally interchangeable, and the shoots and leaves are nutritionally complementary resources, with shoots providing primarily N and P, but deficient in Ca, which is provided by the leaves. Both species of bamboo are, nonetheless, critical for the pandas, because their asynchronous phenology, coupled with seasonal altitudinal migration, enables the pandas to complete their life cycle on this low diversity and highly specialized diet.