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DO ROADS HARM TOADS?

DO ROADS HARM TOADS?. A stochastic simulation model of the spadefoot toad ( Pelobates fuscus ) in a Danish pond system Tove Hels, Centre of Forest and Landscape Gösta Nachman, University of Copenhagen. The problem was approached in two ways:. Experimentally:

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DO ROADS HARM TOADS?

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  1. DO ROADSHARM TOADS? A stochastic simulation model of the spadefoot toad (Pelobates fuscus) in a Danish pond system Tove Hels, Centre of Forest and Landscape Gösta Nachman, University of Copenhagen

  2. The problem was approached in two ways: Experimentally: • Data were collected from five adjacent ponds in Jutland • All individuals arriving and leaving the ponds were caught and marked individually to provide information about age specific survival and reproduction rates • Reproduction was estimated from the weight loss of the females during their stay in the ponds Theoretically: • A general stochastic simulation model of a spatially divided population (metapopulation) was developed • The model includes demographic and environmental stochasticity • Data from the field system were used to estimate the relevant parameters • The model predicts the number of males and females in each age class and in each pond

  3. MetaFusc: A stochastic simulation model of Pelobates fuscus

  4. Conclusions: • The ponds constitute a core-satellite (or source-sink) metapopulation system • Stochastic processes make local (and to some extent regional) dynamics unpredictable • Inverse density-dependent mortality on eggs and tadpoles imposes a threshold effect that impedes colonization of empty ponds and leads to sudden extinctions • Environmental stochasticity has a negative effect on regional persistence but may be beneficial to the satellite subpopulations • Lower dispersal rates decrease the proportion of occupied ponds • A road has a negative effect on the isolated pond but not on the remaining metapopulation • Efforts to increase juvenile survival will be more beneficial than efforts that only increase adult survival and reproduction

  5. Thank you for your attention

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