Mason said such conditions likely stem from a combination of ill health, unusually small social groupings, inadequate dwelling space, and European weather that is often colder than in the elephants’ native habitats. Female elephants in the wild live in interactive family groups of up to ten individuals, said Mason. The female calves usually remain in their family group for life and develop strong bonds with members of that group. In contrast, zoo elephants are typically found in groups of two, and two-thirds of female calves are taken from their mothers at an early age. This low level of family structure and the relatively small enclosures of zoos contribute to boredom and distress, said Mason. Wild elephants roam over distances as much as 60 to 100 times larger than typical housing for zoo elephants, 90% of whom have no natural grazing.