Nature's Biggest Beasts

Size matters in wildlife, for species and individuals. As relative skin surface versus mass decreases exponentially with size, large animals have an advantage in the cold, hence Arctic species tend to be larger, like the polar bear, but a disadvantage in war weather, requiring adaptations in the tropics and deserts to cool down, gather or conserve water. Larger also means stronger, a better chance to fight enemies like predators or rivals for food and mating rights. Being large requires adaptations, which even puts limits on size, especially on land, to cope with gravitational problems like drinking with a giraffe's neck (allowing grazing high above herds). In the evolutionary arms race smaller species may however develop countermeasures, like poison to kill much larger preys.