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Relatório final do protocolo de colaboração entre ICN/PNSACV e CIBIO-UP (2002-2005)
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Reynolds, J.C. & Tapper, S.C. 1995: The ecology of the red fox Vulpes vulpes in relation to small game in rural southern England. - Wildl. Biol. 1: 105-119. Diet, population density, dispersion, and productivity of red foxes were investigated in an 11 km(2) area of mixed agriculture representative of much of lowland rural Britain, where medium-sized animals (adult weight 0.3-3.5 kg) were abundant. Four small game species within this size range - brown hare Lepus europaeus, pheasant Phasianus colchicus, grey partridge Perdix perdix, and redleg partridge Alectoris rufa - were also censussed twice a year throughout the study. Fox diet was determined by analysis of faecal material, with diet of cubs at breeding dens analysed separately. Two-thirds of fox diet consisted of vertebrate prey in the range 0.3-3.0 kg. Prey types of overwhelming importance for foxes in other environments - such as small rodents, fruit and invertebrates - each contributed 10% or less to fox diet. Fox territory size was determined by radio-tracking eight adult foxes during a three-year period in spring, summer and autumn. Details of family group size, number of litters per group, and litter size were determined through field observation. Adjacent fox territories (mean size 2.7 km(2)) formed a contiguous mosaic with individual foxes spending less than 10% of their active time on ground shared with neighbouring groups. Typically each territorial group held an adult pair and had one litter of four cubs. Half of these groups had an additional, non-breeding vixen. Most known fox deaths were the result of deliberate control by man. Control on a central 4.75 km(2) farm reduced adult fox density and eliminated cub production there, and for the whole 11 km(2) study site deliberate control was almost sufficient in itself to negate annual numerical increase in fox numbers. The food requirements of foxes living at this density was estimated, and from this the biomass of lagomorphs and gamebirds consumed. Even assuming early dispersal of juvenile foxes, the biomass of these species consumed annually was substantial relative to that available at the onset of breeding. It is suggested that hare and rabbit populations were able to survive this heavy depredation because they have a long breeding season and foxes exploited annual production of young prior to maturity; by contrast, the pheasant population was supported artificially by release of hand-reared birds. Jonathan C. Reynolds & Stephen C. Tapper, The Game Conservancy, Fordingbridge, Hampshire SP6 IEF, United Kingdom
Immuno-contraception is being developed in Australia to control populations of the introduced red fox Vulpes vulpes. One possible adverse response is compensatory reproduction which is being studied in captive and wild populations. At high food supplies, groups form with more cubs born to them than to mated pairs. There may be little agonistic behaviour as well, and the role of "helpers' in groups needs elucidation. The circumstances under which home ranges are defended in whole or in part is uncertain also. It is suggested that the concept of "fugitive species' should be examined for an understanding of flexibility in the socio-ecological system of the red fox. -from Author
The diet of the Irish hare Lepus timidus hibernicus Bell, 1837, was investigated in western Ireland by analysis of feaces collected each month for a year from 3 areas of blanket bog. 1 of rough grassland and 1 of machair.
The reproductive output (ovulation rate, fertility, barrenness, productivity, pre-natal mortality) of the red fox Vulpes vulpes (n = 317) has been studied in a Mediterranean region (Pisa province, Central Italy) in 1992 by post-mortem analysis. On average, female foxes shed 5.03 ± 1.27 ova, had 3.95 ± 1.25 placental scars and 3.88 ± 1.55 live embryos. Twenty percent of foxes were barren, and intra-uterine mortality was common: 47% of females lost at least one ovum before implantation; 43.5% of yearlings (≤ 1 year old) lost at least one foetus, whereas only 16.7% of adults did so. Male yearlings had lower testis mass than adults. The reproductive output was higher for heavier females, but marginally so for those with greater head and body length. Barrenness and intra-uterine mortality were not related to body size. Amount of body fat and age were unrelated to reproductive output, with the exception of post-implantation mortality (higher for yearlings). All these results suggest that the reproduction of the red fox was not limited directly by food availability, but rather by social modulation. The reproductive output in this population was low in comparison with other populations, in spite of faster physical development. A review of the literature suggests compensatory reproduction in the red fox, litter size being larger in areas of higher mortality.