Volume contents

Abstract

1. Disease epizootics can significantly influence host population dynamics and the structure
\nand functioning of ecological communities. Sarcoptic mange Sarcoptes scabiei has dramatically
\nreduced red fox populations Vulpes vulpes in several countries, including Britain,
\nalthough impacts on demographic processes are poorly understood. We review the literature
\non the impact of mange on red fox populations, assess its current distribution in Britain
\nthrough a questionnaire survey and present new data on resultant demographic changes in
\nfoxes in Bristol, UK.
\n
\n2. A mange epizootic in Sweden spread across the entire country in < 10 years resulting in a
\ndecline in fox density of up to 95%; density remained lowered for 15–20 years. In Spain,
\nmange has been enzootic for > 75 years and is widely distributed; mange presence was
\nnegatively correlated with habitat quality.
\n
\n3. Localized outbreaks have occurred sporadically in Britain during the last 100 years. The
\nmost recent large-scale outbreak arose in the 1990s, although mange has been present in
\nsouth London and surrounding environs since the 1940s. The questionnaire survey indicated
\nthat mange was broadly distributed across Britain, but areas of perceived high prevalence
\n(> 50% affected) were mainly in central and southern England. Habitat type did not significantly
\naffect the presence/absence of mange or perceived prevalence rates. Subjective assessments
\nsuggested that populations take 15–20 years to recover.
\n
\n4. Mange appeared in Bristol’s foxes in 1994. During the epizootic phase (1994–95), mange
\nspread through the city at a rate of 0.6–0.9 km/month, with a rise in infection in domestic
\ndogs Canis familiaris c. 1–2 months later. Juvenile and adult fox mortality increased and the
\nproportion of females that reproduced declined but litter size was unaffected. Population
\ndensity declined by > 95%.
\n
\n5. In the enzootic phase (1996–present), mange was the most significant mortality factor.
\nJuvenile mortality was significantly higher than in the pre-mange period, and the number of
\njuveniles classified as dispersers declined. Mange infection reduced the reproductive potential
\nof males and females: females with advanced mange did not breed; severely infected males
\nfailed to undergo spermatogenesis. In 2004, Bristol fox population density was only 15% of
\nthat in 1994.