During the flooding of primary lowland rain forest by the filling of a
hydroelectric reservoir in French Guiana, live-trapping was conducted on 175
subsequently formed islands. Different factors affecting the mammal trap
efficiency were analysed. The main results show the real complexity of the
sampling problem and the influence of the habitat disturbance due to the
flooding. The location and/or the type of traps influenced captures of
Dasypus novemcinctus, Proechimys spp., Metachirus nudicaudatus and Philander
opossum in relation to their foraging and/or locomotion behaviour, and to to their size. The conformation of the islands
(height and size) had no influence on the number of captures, nor on the species
richness. The number of captures increased with the number of trapnights during
the first water inflow and the level stretch. The best trapping success was observed
during the wet season, when the strong habitat modification and the forest fragmentation became more significant. It resulted from the reduction of available
land area and trophic resources. One year after the beginning of the water inflow, the decrease of the number of captures with the increasing
number of trapnights reflected a real decrease of the number of mammals on
the islands. The species richness increased with the number of trapnights in
all periods, and was also the highest during the wet season.