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Evaluación de la Efectividad del Control de Depredadores: el Zorro Rojo no Nativo Como Estudio de Caso
Author(s) -
Harding Elaine K.,
Doak Daniel F.,
Albertson Joy D.
Publication year - 2001
Publication title -
conservation biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.2
H-Index - 222
eISSN - 1523-1739
pISSN - 0888-8892
DOI - 10.1046/j.1523-1739.2001.0150041114.x
Subject(s) - vulpes , predator , predation , population , endangered species , biology , ecology , zoology , habitat , demography , sociology
Non‐native vertebrate predators pose a severe threat to many native species, and a variety of management programs are aimed at reducing predator effects. We sought to assess the effects of predator‐control programs by analyzing changes in prey and predator populations based on data commonly collected in these programs. We examined data from a predator‐control program that primarily targets the introduced red fox ( Vulpes vulpes regalis ) in central California. Red foxes negatively affect populations of native waterbirds, particularly the endangered California Clapper Rail ( Rallus longirostris obsoletus ). Using a combination of matrix population modeling, simple difference equations, and statistical analysis, we analyzed data on removed predators and monitored prey populations. Past control efforts succeeded in depressing fox numbers in local areas over 3‐month intervals, and there was a significant, positive relationship between the growth rate of local Clapper Rail populations and the successful trapping of red foxes in the preceding year. By modeling the effect of different fox‐removal rates, we found that a stable or declining population could be achieved by removing a minimum of 50% of the adults and 25% of the juveniles. Under trapping rates of 50–70%, the proportion of the fox population composed of immigrants averaged 20–52%. In contrast to the current management approach, elasticity analyses suggested that changes in adult survival rates had relatively little effect on long‐term population growth. Overall, our approach indicated that predator control was effective in the short term, but for longer‐term success it may be necessary to redirect efforts to control juvenile and immigrant foxes. Our analytical approach is potentially useful for evaluating current control programs aimed at reducing the effects of predators on native species.