Browsing Scientia Discipulorum vol. 6 (2013) by Subject "predation"
Now showing items 1-2 of 2
An examination of sensory input in anti-predator behavior of the American crow (Corvus brachyrhynchos)Sensing, processing, and responding to environmental cues is a fundamental process, particularly for avifauna. The degree to which signals are effectively responded to, determines an individual's and a species' ability to function and flourish in its habitat. The sensing of sight and sound are highly evolved environmental analysis tools of the American crow (Corvus brachyrhynchos). This study examined how crows respond to visual and auditory cues in urban and rural environments. Taxidermic models of a great-horned owl (Bubo virginianus) and a red-shouldered hawk (Buteo lineatus), a recorded call of the great-horned owl, and a recorded crow mobbing call were used to test the mobbing response of local crows in several different locations. No significant difference was found in mobbing response between urban and rural environments. There was a significant difference in number of crows mobbing the two predator species. Results suggest that crows use sensory information differently; visual cues for predation avoidance and auditory cues for intraspecific communication. The results also suggest crows exhibit discretionary sensory processing and responses. This study provides insight to how a highly successful synanthropic species utilizes sensory information to thrive in natural and anthropogenic habitats.
Frequency of missing legs in the cave cricket, Hadenoecus subterraneusThe cave cricket (Hadenoecus subterraneus) is a keystone species in maintaining biological diversity in cave communities in Mammoth Cave National Park. Crickets must leave the cave to forage on nights when conditions are favorable, which puts them at considerable risk of predation. Invertebrates have developed defenses for predation, including autotomy (voluntary loss of a limb). We hypothesize that missing legs are a sign of predation pressure on the crickets, and may be vary in different environments. We used a visual census to record the sex-specific frequency of missing legs among adult cave crickets at eight different cave entrances. We expected males to be missing legs more than females because they must leave the cave refuge to forage more frequently than females; however, we found that males and females were missing legs in equal numbers. The hind leg was missing with greater frequency than other limbs, likely the result of cricket predator avoidance behavior (jumping), which puts the larger hind limb closest to the predator. The frequency of crickets with missing limbs varied among cave entrances from a low of 6.6% to a high of nearly 40%, with abundance varying yearly. In Frozen Niagara, which consistently had a high proportion of crickets missing legs, the percentage missing legs was highest in crickets roosting closer to the entrance (30.8%) than deeper (18.7%) into the cave. The goal of this survey was to study the pattern and implications of limb loss on foraging and predator avoidance.