Gormezano and Rockwell calculated the total caloric values of snow geese and caribou--two possible prey alternatives to seals that bears have been observed hunting--and found there to be enough calories necessary to prevent starvation. One bull caribou, for example, worth approximately 105,000 calories, could last a bear for 27 days. Even a calf, depending on age, could provide anywhere from 4,700 to 34,000 calories and sustain an adult bear for 8 days or so. Feeding on smaller food sources, like geese and eggs, requires more consumption--between 10 to 26 clutches of eggs a day--but the relative lack of effort needed to harvest them tends to offset this. The reality is that polar bears are master opportunists (they have been known to snack on anything from berries and lichens to whale carcasses). As Rockwell so eloquently puts it, "If it's lunch time and there's a sushi bar, I'm there. But if it's lunch time and there isn't a sushi bar, pizza works."