The effect of barn owls (Tyto alba) on the activity and microhabitat selection of Gerbillus allenbyi and G. pyramidum

Abstract

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.

Habitat structure determines competition intensity and invasion success in gecko lizards

“…Three processes known to be affected by habitat structure are commonly observed in most animals. First, predation or the threat of predation is affected by habitat structure, and species respond to this threat (31)(32)(33). Second, foraging efficiency for mobile or stationary prey is affected by habitat structure (2,(8)(9)(10)(11)(12)(13)(14).…”

Construct validity of behavioral models of anxiety: Where experimental psychopathology meets ecology and evolution.

“…A behavioral ecological approach to risk assessment can be constructed as follows: (Kavaliers & Choleris, 2001)" In behavioral ecology, this is usually modeled using the construct of "antipredator apprehension", a motivational state defined as a reduction in attention to other activities (such as foraging and mate seeking) as a result of enhanced allocation of attention to detection and avoidance of potential predators (Brown, et al, 2001); the behavioral output of this state is "vigilance", a behavioral state involving alertness and scanning for prey. For example, gerbils (Gerbillus allenbyi and Gerbillus pyramidum) change their behavior from "blind foraging" to no feeding and total vigilance, through a phase of low feeding and increased scanning behavior (Abramsky, Strauss, Subach, Kotler, & Reichman, 1996;Dall, Kotler, & Bouskila, 2001). This "apprehension continuum" is reminiscent of the concept of defensive distance from the ethopharmacological literature: when the risk is high (i.e., when the defensive distance is small), animals adopt safer tactics (defensive aggression, refuge use, escape); when the risk is low (i.e., when the defensive distance is intermediate to great), animals tend to be more flexible in their behavior (risk assessment, normal non-defensive behavior).…”

Thermobiology, energetics and activity patterns of the Eastern tube-nosed bat (Nyctimene robinsoni) in the Australian tropics: effect of temperature and lunar cycle

“…Moreover, if they rely on vision for foraging like pteropodid bats, they are also likely to be affected by nocturnal illumination, such as during different phases of the moon cycle. Data from the literature suggest that during higher lunar illumination nocturnally active rodents (Lockard and Owings, 1974;Wolfe and Summerlin, 1989;Bowers, 1990;Daly et al, 1992;Abramsky et al, 1996), lagomorphs (Butynski, 1984;Gilbert and Boutin, 1991), and some neotropical and insectivorous bats (Erkert, 1978;Haeussler and Erkert, 1978;Morrison, 1978;Morrison, 1980;Lang et al, 2006) reduce their activity. This is generally explained by increased predation pressure, which seems to outweigh the advantage that could be gained in finding food.…”