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Aggressive Motivation in the Midas Cichlid: Evidence for Behavioral Efference
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Behavioral Efference is a hypothetical positive feedback from the performance of an aggressive display that augments the level of aggressive motivation. The hypothesis was proposed (BOND, 1989) to account for the occurrence of truthful communication during aggressive encounters, even in the face of a presumed selective pressure in favor of deceit (MAYNARD SMITH, 1984). Evidence of Behavioral Efference was sought in an experimental study of adult Midas cichlids Cichlasoma citrinellum, in which subjects responded aggressively to varying sizes of dummy fish. Before and after each aggression trial, the level of aggressive motivation was estimated from the intensity of the subject's attacks on conspecific juveniles. A weighted index of aggressiveness that objectively combined the frequencies of four aggressive action patterns was obtained using detrended correspondence analysis. Aggression indices from aggression trials, as well as from intertrial intervals, furnished a basis for comparison of two causal models: behavioral efference, which assumes that post-stimulus motivation is substantially influenced by display performance, and Direct Stimulus Mediation, which assumes that the displays themselves play no immediate causal role. When the subjects actively displayed to the stimulus dummy, the results showed no significant correlation between the size of the dummy and the magnitude of the motivational effect. However, a significant relationship was demonstrated between the level of aggressive display and subsequent increases in aggressive motivation, in precise accord with the Behavioral Efference model. Direct Stimulus Mediation was evident only in trials in which the subject displayed no overt aggression toward the stimulus object. An account of the functional significance of Behavioral Efference is provided, suggesting that the feedback serves to regulate the intensity of aggressive interactions by preparing the displaying individual for active combat.
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Escape Gaits of White-Tailed Deer, Mule Deer and Their Hybrids: Gaits Observed and Patterns of Limb Coordination
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1. The escape gaits of white-tailed deer, mule deer and hybrid white-tailed x mule deer from Alberta were examined to investigate two hypotheses: 1) that the distinctive security patterns of white-tailed deer and mule deer underly their traditional habitat segregation, and 2) that interbreeding between white-tailed deer and mule deer results in disrupted security patterns for hybrid progeny. The first step is investigating these hypotheses, and the goals of this paper, were to identify gaits used by each type of deer and to compare characteristics of limb coordination in these strides. 2. High speed cinematography was used to record the fast escape gaits to captive white-tails, mule deer and hybrids. HILDEBRAND'S (1977) method for analyzing asymmetrical gaits were adapted to examine characteristics of limb coordination. 3. All groups galloped at times, but only white-tails galloped for escape when most alarmed. Mule deer stotted and F1 hybrids (with white-tail and with mule deer mothers) bounded when seemingly most alarmed. Gaits of F1 hybrids were similar among individuals. Although gaits of 3/4- and 7/8-mule deer were variable, these backcrosses largelyfailed to reproduce the specialized mule deer gaits. The consistency of white-tail, mule deer and FI hybrid gaits indicates that these patterns have a strong genetic basis and could have evolved in response to different selective pressures. 4. Galloping white-tails tend to have two brief suspensions in their strides, whereas galloping mule deer tend to have prolonged suspension after the hind limb departure and more overlap between the hind and fore limbs. In part due to these characteristics, galloping white-tails attain faster speeds than galloping mule deer or hybrids. Hybrids are intermediate, but much more similar to mule deer. 5. Limb timing data were plotted on three-dimensions with the axes fore lead, hind lead and midtime lag to consider the range of strides employed by deer. Strides of the purebred gallops and mule deer stott fell into discrete regions of this figure, indicating these gaits are qualitatively distinct for contemporary white-tails and mule deer. liule deer strides that were intermediate between the gallop and stott had large overlap between the fore and hind limbs (i.e. small midtime lag) relative to the amount of overlap between the right and left fore limb (i.e. fore lead), perhaps reflecting gait forms that were evolutionary transitions to the stott.
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Composition and Dynamics of Humpback Whale Competitive Groups in the West Indies
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It has been hypothesized that humpback whale, Megaptera novaeangliae, competitive groups represent intrasexual competition by males for access to a mature female. The composition and dynamics of these groups was studied between 1989 and 1991 in Samana Bay, West Indies. The sex of group participants was determined by molecular analysis of skin biopsies. Groups showed similar characteristics of size and movement as those described from other breeding areas, except that only one group contained a calf. The sex was determined of 141 participants in 44 competitive groups. In 21 of these groups, we were able to biopsy all participants. No group contained more than one female, but seven of the wholly sampled groups (all of them small) consisted entirely of males. Of 22 animals who were ''positively'' assigned the role of Nuclear Animal, 17 were female, and five were male. Similarly, of 24 biopsied Principal Escorts, 23 were male and one female. All 24 biopsied Challengers were male. Of 55 animals who were either classified as Secondary Escort, or whose role could not be categorized, 51 were male and four female. In 8 cases, associated pairs of males exhibiting no aggression towards each other were observed to either enter or leave a competitive group together. Of 16 individuals resighted on more than one day, all but one were males. These data suggest that: 1. While most groups (as predicted) represent male-male competition for a single female, observers should be cautious in their assumptions; 2. All-male groups may represent dominance sorting by unfamiliar conspecifics; 3. Females may occasionally aggressively repel advances by unwanted males; 4. While unlikely in light of present knowledge, the possibility that males form coalitions cannot be dismissed. We suggest that competitive groups may be asymmetrical contests in which a female Nuclear Animal is of more value to the Principal Escort than to a Challenger, particularly if the former's defence of her represents mate-guarding.
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An Evaluation of Auditory Learning in Filial Imprinting
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The characteristics of auditory learning in filial imprinting in precocial birds are reviewed. Numerous studies have demonstrated that the addition of an auditory stimulus improves following of a visual stimulus. This paper evaluates whether there is genuine auditory imprinting, i.e. the formation of a preference for an auditory stimulus as a result of exposure to it. Many studies lack important features such as a balanced experimental design or a retention interval, which makes it difficult to draw firm conclusions from their results. The majority of studies of early auditory learning have used a compound of a visual and an auditory stimulus during training. Presentation of a visual object during auditory training improves learning about sounds. The visual stimulus may act as a US for learning about sounds. Alternatively, presentation of a visual stimulus may increase attention or arousal and thereby improve learning about the sound. In a large number of studies visual stimulation during auditory exposure was provided by the presence of a hen or siblings. Relatively few studies using only auditory exposure have demonstrated significant auditory learning. Exposure to a sound before hatching can lead to a significant preference for that sound when tested after hatching. However, such preferences are generally weak and short-lived. In a number of species, a predisposition for species-specific calls has been demonstrated, that is already apparent before hatching. It is concluded that auditory stimuli play an important role in the formation of filial preferences, but that auditory imprinting is not as prominent as has sometimes been suggested, especially when compared to visual imprinting.
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Avian Movement Imitation and a New Form of Mimicry: Tracing the Evolution of a Complex Form of Learning
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1. The spontaneous imitation of movements, previously known in two orders of mammals, is demonstrated in a psittacine bird. 2. The animal, a Grey parrot which has bonded to humans, utilizes its torso, legs, wings, head, beak, and tongue in the imitation of human movements. 3. A new form of imitation, ''non-vocal mimicry,'' is tentatively identified. It is defined by the use of skeletal movements to produce mimetic sounds. 4. Hierarchical relationships and phylogenetic patterns of occurrence suggest that imitative learning in birds may have evolved through the sequence: song/call learning → vocal mimicry → non-vocal mimicry→ movement imitation. 5. These relationships and patterns, and possible differences in function and incubation time, suggest that movement imitation in birds is not homologous to that in mammals.
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Inherited Population Differences in Avoidance Conditioning in Three-Spined Sticklebacks, Gasterosteus Aculeatus
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Laboratory-reared predator-naive three-spined sticklebacks from two sites, one with abundant predatory fish (the high-risk site) and the other essentially predator-free (the low-risk site), were given a passive avoidance conditioning task in which they received a simulated attack from a model avian predator whenever they entered a previously-favoured feeding patch. 15/16 fish learned to avoid the dangerous patch within 15 days, but those from the high-risk site did so significantly faster and received fewer attacks in the process. The two categories of fish did not differ either in active avoidance of the attack stimulus or in the rate at which they started to re-exploit the dangerous patch once negative reinforcement ceased. It is argued that fish from high- and low-risk sites differ in the negatively reinforcing properties of the same, standardised attack.
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Memory Does Not Constrain Individual Recognition in a Bird With Song Repertoires
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We tested the hypothesis that memory or perceptual limitations imposed by song repertoires contrain the ability of song birds to recognize their neighbours by song. Using operant conditioning procedures, we trained male song sparrows (Melospiza melodia) (median repertoire size = 8) to discriminate between two artificial song sparrow repertoires of 32 songs each (64 songs total). Both song sparrows learned to discriminate concurrently between all 32 song pairs. The birds learned later songs as quickly as they learned earlier songs. These results suggest that song sparrows are capable of memorizing the full song repertoire of their neighbours under natural conditions. In a second experiment we found that song sparrows readily generalize from one exemplar of a song type to other variations of that song type. We conclude that the evolution of song repertoires of song sparrows have neither constrained nor been constrained by individual recognition of neighbours by song.
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Simulation and Analysis of Information-Center Foraging
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I present a mathematical model and simulation of information-center (IC) foraging (WARD & ZAHAVI, 1973). The results indicate that the most important condition for supporting an IC is time-limited foraging in patches supporting multiple individuals. Foraging rate is enhanced by information exchange even where the probability of finding food is otherwise relatively high (i.e. not, as generally assumed, exclusively where food is "unpredictable"). The effects of IC foraging are strongest for small populations (N < 20), though they increase marginally as the number of individuals increases. One can determine the critical patch-duration at which IC foraging becomes profitable and how individuals may optimally distribute search time between active scouting and vicarious search (through recruitment in the IC). As food becomes difficult to find, the optimal proportion of time an individual should scout on its own approaches roughly one-half.
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Sequential Analysis of Nominal Data in Mother-Infant Communication: Quantifying Dominance and Bidirectionality
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In recent studies on early communication a preference seems to exist for applying statistical methods to behaviours that have in some way been scaled. As an alternative, two methods for analyzing the interaction between two sequences of nominal data are discussed: an information-statistical analysis as developed by VAN DEN BERCKEN & COOLS (1980a) and log-linear modelling. Both methods make use of contingency (transition) tables, which should be constructed according to common requirements that are often ignored in practice. Firstly, the relationships between the number of behavioural categories, the length of the recording, the complexity of the model and the reliability of the statistics need to be considered. Secondly, choices have to be made regarding the use of either time or event sequences. Although these requirements are explained and illustrated using theoretical considerations and data on early mother-infant communication in humans, the application of these models may be much broader. Since informational and log-linear statistics are mathematically related, both can be used to describe the same measures of directionality in the interaction of individual pairs.
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