The Romans mined lead in the Castleton caverns and the straight lines of dry stone walls mark the fields that were common land before the "enclosures" drove the peasants to the towns in the 18th century.
Without improved immunology, curators would have to be far more reticent about letting their animals move into larger and more populated enclosures.
Animals live in appropriate social groups within enclosures designed to resemble their natural habitat.
They spray deer musk in big cat enclosures, and freeze a polar bear's fish supper in blocks of ice.Few of the changes in the handling and presenting of animals would be possible had great progress not come in veterinary care.
Curious as to whether these changes were happening regularly, and keen to identify specifically how behaviour was changing, Mr Ross and a team of his colleagues decided to carry out an experiment.The researchers trained observers to monitor seven chimpanzees and seven gorillas in both the holding areas and the enclosures.
In contrast, time spent foraging for food dropped from 18.1% of the total in the enclosures to 10.5% of it in holding areas.Gorillas showed a drop in foraging as well.
It fell from 30.6% of their time when in the enclosures to 5.4% in the holding areas.
Boom and bust ReprintsDr Molette and her colleagues raised 150 male mule ducks (a cross between Pekin and Muscovy ducks that is often used to produce foie gras) for 13 weeks in standard poultry-house conditions and then transferred them into individual enclosures.
In the first enclosures, in 18th- and 19th-century Britain, the commons open fields used by many, belonging to all, owned by none were fenced in, and nearly all land became private property.
Guests slotted themselves into small, horizontal enclosures like bees into honeycomb, with space only for a bed and a tiny television.
It has a doughty defender in Stroud, who seeks out its seeds, propagates them in shade houses, plants them out in enclosures and the wild, and protects them from budleias, Koster's curse, rabbits and other foes.
