The results, reported in the Sept. 5 issue of Nature, contradict assertions by pro-hunting groups that fox numbers had soared during the hunting ban. The Farmers' Union of Wales, for example, had claimed that the ban had led to an ''explosion in the population to unprecedented levels'' and said some farmers had reported a huge increase in the number of attacks on sheep.
Dr. Harris has studied foxes and badgers in the Bristol area for about three decades, and in 1999 he began a long-term study of foxes throughout lowland Britain. He and his colleagues surveyed 160 one-kilometer-square plots in late winter of that year and at the same time in 2000. Then, in February 2001, with the countryside in the throes of the foot-and-mouth epidemic and many farms essentially locked down, the hunting ban was instituted.
When the ban was lifted at the end of 2001, Dr. Harris realized that he had an opportunity to gauge its effect. So in February and March of this year, he and his team surveyed the plots again.
Foxes are notoriously secretive, Dr. Harris said, which makes them difficult to count through sightings. Instead, he and his surveying teams used a system of counting fox feces. Since foxes tend to avoid open spaces, preferring to travel along hedgerows and other linear features in the landscape, finding feces was not difficult. And since the average fox produces a given amount of feces each day, ''it's a good way of counting fox numbers,'' Dr. Harris said.
Dr. Arthur Lindley, science director of the Royal Society for the Prevention of Cruelty to Animals, said Dr. Harris's methodology was completely accepted.
''We have argued that the fox population does not need to be and cannot be artificially controlled,'' Dr. Lindley said. ''This research has, on a completely objective basis, confirmed our belief.''
But the Countryside Alliance, an umbrella organization for hunting advocates and groups that champion rural causes, questioned the science behind the study. ''It was set up to study something else,'' said Tim Bonner, a spokesman for the alliance, who described Dr. Harris as a ''long-term opponent of us.'' Mr. Bonner also said the study did not cover some parts of Britain where hunting is very popular.
But Dr. Harris said his survey plots, which were randomly selected, included both well-hunted and hunt-free areas. ''And that's important for the results,'' he said. ''There was no difference between the two.''
Dr. Lindley said he was not surprised at the study's results, given that there are an estimated 400,000 to 700,000 foxes in Britain, and, even by generous estimates, hunting kills only 15,000 of them a year. ''Fifteen-thousand animals in the scale of things wouldn't make much of a difference,'' he said.
Dr. Harris said that over the years he had observed that foxes appeared to do a good job of regulating their numbers on their own -- for example, by producing smaller litters in overpopulated areas. ''Our data suggest that the way foxes regulate their own numbers is as important as any culling that is done,'' he said.
