Periodicity of death feigning by domestic fowl in response to simulated predation

Bispectral index reveals death-feigning behavior in a red kite (Milvus milvus)

Red kites (Milvus milvus) are birds of prey known to feign death in the presence of humans. An adult wild red kite was anesthetized with isoflurane for coelioscopy. During surgery, heart rate and respiratory rate ranged from 240 to 260 beats per minute and from 16 to 28 breaths rates per minute, respectively. Pupil and corneal reflexes remained present, and body temperature was maintained at 40.4 degrees C (104.7 degrees F). Suppression ratio was 0 during the anesthetic episode. The bispectral index was 44 immediately after intubation, ranged from 44 to 57 during maintenance of anesthesia, and was 59 at the moment of extubation. The index increased to 85 while the kite remained immobile, which was suggestive of feigning death in sternal recumbency. Once the bird was perched upright, it immediately kept the upright position, which confirmed the correspondence of the bispectral index value (85) with a fully conscious patient. Although behavioral or cardiorespiratory variables remained unchanged, the degree of hypnosis was indicated by the bispectral index, which anticipated a possible sudden awakening episode of this bird.

Adaptive significance of death feigning posture as a specialized inducible defence against gape-limited predators

Death feigning is fairly common in a number of taxa, but the adaptive significance of this behaviour is still unclear and has seldom been tested. To date, all proposed hypotheses have assumed that prey manage to escape predation by sending a death-mimicking signal, although death-feigning postures are markedly different from those of dead animals. Moreover, the efficacy of this technique may largely depend on the foraging mode of the predator; death feigning seldom works with sit-and-wait predators that make the decision to attack and consume prey within a very brief time. We examined whether death feigning in the pygmy grasshopper Criotettix japonicus Haan was an inducible defence behaviour against the frog Rana nigromaculata, a sit-and-wait, gape-limited predator. The characteristic posture assumed by the grasshopper during death feigning enlarges its functional body size by stretching each of three body parts (pronotum, hind legs and lateral spines) in three different directions, thereby making it difficult for the predator to swallow the prey. Our result is the first consistent explanation for why death-mimicking animals do not always mimic the posture of dead animals.

Prehatch entrainment of circadian rhythms in the domestic chick using different light regimes

The onset of circadian rhythms in many animals occurs during prenatal development. We conducted four experiments, using the domestic chick as a model, to assess when these rhythms can first be entrained and the type of light zeitgeber necessary. In Experiment 1, the presence of circadian rhythms was assessed using tonic immobility, an antipredator behavior, whereas in Experiments 2 to 4 body temperature was studied. We demonstrate that (a) circadian rhythms can be entrained during the late stage of the chick's 21-day incubation period (prehatch Days 13-18), (b) only 1 day of light cues [12:12 hr light:dark (12L:12D)] on prehatch Day 13 is necessary for entrainment, and (c) short bouts of light, which simulate the light cues embryos typically experience during natural incubation, can act as zeitgebers although they are not as effective as 12L:12D. The onset of entrainment is earlier than predicted and suggests that the brain structures mediating circadian rhythms mature sooner than proposed by previous research.

Time budgets in growing chicks

The manner in which rapidly growing chicks distribute their time among diurnal activities was measured in two studies in which the amount of available light was varied to match seasonal extremes. The effectiveness of the chick's time budgets was assessed in terms of the impact on growth. In Experiment 1, 24-hr patterns of feeding, drinking, nesting, and wheel-running were recorded during successive photoperiods with 12, 6, 18, and 12 hr of light when access to a social partner was concurrently available. In Experiment 2, access to a social partner was an exclusive activity. In both studies, chicks' 24-hr behavioral patterns in response to temporal constraints on their diurnal activities were surprisingly plastic, permitting them to defend a normal and high rate of growth. This was accomplished by changes in feeding rate and by nocturnal feeding rather than by systematic elimination of other diurnal activities. When sociality and feeding were competing activities, feeding time decreased and feeding rate increased such that contact with a conspecific as well as rapid growth were defended. The absolute amount of time spent in measured activities was invariant within subjects irrespective of age, photoperiod, or the number and type of activities recorded, providing evidence of time budgets in immature organisms. In both studies, buffer time (the amount of time spent in no activity) emerged as a significant aspect of the daily time budget that is defended through a variety of environmental challenges.

Twilight activity and antipredator behavior of young fowl housed in artificial or natural light

Twenty-four-hr patterns of running wheel activity (Experiment 1) and death feigning, an antipredator behavior (Experiment 2), were studied in domestic chicks housed outside, in natural lighting, or indoors, with light onset and offset timed to coincide with the upper limbs of local sunrise and sunset, respectively. Although chicks housed outside were more active and displayed stronger death feigning reactions, the daily patterns of each activity were highly similar in the two groups. Activity peaked during the period corresponding to evening twilight and was negligible during the morning twilight period; in contrast, death feigning peaked during the morning twilight period. Activity measures indicated that chicks on the artificial light schedule had learned to anticipate dark by day 5, and subsequent ontogenetic changes in activity occurred exclusively in the evening twilight phase.

Naloxone interactions with morphine-and shock-potentiated tonic immobility in chickens

Opiate receptor involvement in tonic immobility was examined by administering various does of the opiate antagonist naloxone before measuring morphine-potentiated, shock-poteniated or unpotentiated tonic immobility in chickens. Naloxone attenuated morphine-potentiated, but not shock-potentiated or unpotentiated tonic immobility. Morphine-potentiated tonic immobility appears to be opiate specific.

Components of predation defense behavior in chickens: evidence for endogenous rhythmicity

The manifestation of diurnal periodicity and the extent of its control by the photoperiod was assessed in three predation defense reactions which constitute either components or outcomes of a predator-prey interaction sequence. Two-hundred White Leghorn chicks were reared from hatching for one week in either 24L or 12L and then tested at one of two clock hours previously demonstrated to define peak and trough response for one of the components. Putative evidence was found for an endogenous source of the periodicity manifested in all reactions. Maintenance schedule did not entrain the periodicity, but simple room entry and handling elicited anti-predator reactions, the extent of which varied as a function of clock hour. A general model of predation defense behavior was proposed.