Predation plays an important role in ecological communities by affecting prey behavior such as foraging and by physical removal of individual prey. In regard to foraging, animals such as desert rodents often balance conflicting demands for food and safety. This has been studied in the field by indirectly manipulating predatory risk through the alteration of cues associated with increased risk such as cover or illumination. It has also been studied by directly manipulating the presence of predators in aviaries. Here, we report on experiments in which we directly manipulated actual predatory risk to desert rodents in the field. We conducted a series of experiments in the field using a trained barn owl (Tyto alba) to investigate how two species of coexisting gerbils (Gerbillus allenbyi and G. pyramidum) respond to various cues of predatory risk in their natural environment. The gerbils responded to risk of predation, in the form of owl flights and owl hunger calls, by reducing their activity in the risky plot relative to the control plot. The strongest response was to owl flights and the weakest to recorded hunger calls of owls. Furthermore, when risk of predation was relatively high, as in the case with barn owl flights, both gerbil species mostly limited their activity to the safer bush microhabitat. The response of the gerbils to risk of predation disappeared very quickly following removal of the treatment, and the gerbils returned to normal levels of activity within the same night. The gerbils did not respond to experimental cues (alarm clock), the presence of the investigators, the presence of a quiet owl, and recorded "white noise". Using trained barn owls, we were able to effectively manipulate actual risk of predation to gerbils in natural habitats and to quantify how gerbils alter their behavior in order to balance conflicting demands of food and safety. The method allows assessment of aspects of behavior, population interactions, and community characteristics involving predation in natural habitats.
Context. Coyotes (Canis latrans) have adapted successfully to human landscape alteration in the past 150 years and in recent decades have successfully moved into urban areas. While this causes concern about human-wildlife conflicts, research also suggests that coyotes tend to avoid humans and human activity in urban areas. For improving management, a better understanding of space use by coyotes is needed.Aims. To study how coyote social behaviour influences fine-scale space use in urban areas we present results from an extensive, multi-year GPS telemetry study . The study area in coastal Rhode Island is a mosaic of rural, suburban and urban land use and coyotes have only recently arrived.Methods. We differentiated between two social classes: residents (individuals that have established a territory; n = 24) and transients (individuals that have no territory; n = 7). Space use was analysed using mixed effect models and detailed land-cover data.Key results. Coyotes tended to select for agricultural and densely vegetated land cover and against land used for housing and commerce. Pasture and cropland were preferred by residents and avoided by transients, especially at night, indicating the role of agricultural land as prime foraging habitat. Both groups selected densely vegetated land cover for daytime shelter sites. Transients selected for densely vegetated land cover both day and night, indicating use for both shelter and foraging. Resident coyotes avoided high-and medium-density housing more than transients.Conclusions. We interpret land-cover selection by resident coyotes as indicative of coyote habitat preference, while transients more often occupied marginal habitats that probably do not reflect their preferences. Differences in land cover selection between residents and transients suggest that transients have a corollary strategy to avoid residents.Implications. With cover and food appearing to be important drivers of space use, coexistence strategies can build on controlling food resources as well as on the tendency of coyotes to avoid humans. Nevertheless, transients, having the need to avoid territorial resident coyotes as well, show a reduced aversion to land cover with high human activity, creating a higher potential for human-wildlife conflicts.
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