Perceived risk of predation and habitat use by the Andean White-eared Opossum Didelphis pernigra (Didelphimorphia: Didelphidae) in an ex-urban area.
The introduction of exotic species can negatively affect native species; for example, the domestic dog (Canis lupus familiaris) can increase their predation risk. We evaluated the effect of the presence of domestic dogs and humans on the foraging behavior of the Andean White-eared Opossum, Didelphis pernigra, in an ex-urban area in the Colombian Andes. We also studied habitat use by this marsupial using the giving-up density (GUD) technique, the amount of food left by a forager after exploiting a patch in which it experiences diminishing returns, and that informs about foraging costs experienced by an individual, including the perceived risk of predation. We measured the GUD's in experiments with the presence of dogs and/or humans in an area in natural regeneration of Andean forest and in an exotic plantation of Eucalyptus globulus near the Bogotá River. The opossums used the regeneration area more than the plantation; the plantation was barely visited. Our results suggest that the opossum chose foraging sites depending on their exposure to potential predators. The human presence reduced the foraging of the opossum in the regeneration forest. In addition, their foraging also was affected by the moon's light, but this effect was modulated by the period of the night. The opossums do not seem to recognize the dog as a threat, probably increasing their vulnerability to the attack of these carnivores.