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Predicting the effect of climate change on aggregation behaviour in four species of terrestrial isopods
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Climate warming has changed the spatial distributions and temporal behaviours of several taxa. A key question that remains is how behaviours that alter microclimatic conditions might be used to buffer the effects of climate change. In this study, we focus on the aggregation behaviour of four species of terrestrial isopods, in which groups of individuals clump together to prevent moisture-loss, and use a laboratory protocol to investigate the effects of changes in relative humidity (RH) and temperature on aggregation. We find that three species aggregate more at lower RH and at higher temperatures, and that species that are better adapted to reducing moisture loss aggregate less than do species with fewer such adaptations. These results suggest that behavioural variation can buffer the effects of changes in microclimate. We finish by suggesting that it is critical to determine how such behavioural shifts will affect isopod densities and competitive hierarchies.
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Ecstatic display calls of the Adélie penguin honestly predict male condition and breeding success
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The Adélie penguin (Pygoscelis adeliae) breeds in large, noisy Antarctic colonies and has evolved a communication system of complex intra- and inter-sexual visual and vocal behaviours. The Ecstatic Display Call (EDC) given by males whilst at the breeding colony is composed of introductory beats, short repeated syllables and a climactic long syllable. Here, we show that spectral qualities of the short syllables of the EDC can predict body condition and breeding success and suggest that in addition to its role in territory defence, the EDC may function as an honest signal of male quality for female mate choice. In the short repeated syllables frequency modulation, mean frequency, and pitch were all significantly lower in birds of better condition, with frequency modulation changing concomitantly with changing condition during the breeding season. Furthermore, during the period of mate attraction, a male's frequency modulation predicted both his latency to pair and likelihood of successfully breeding. Due to the long incubation fasts in this species we propose that female Adélie penguins may reliably use frequency modulation of the EDC as a potentially honest signal of early season male condition and the likelihood of a successful breeding outcome.
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Animal tool use: current definitions and an updated comprehensive catalog
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Despite numerous attempts to define animal tool use over the past four decades, the definition remains elusive and the behaviour classification somewhat subjective. Here, we provide a brief review of the definitions of animal tool use and show how those definitions have been modified over time. While some aspects have remained constant (i.e., the distinction between 'true' and 'borderline' tool use), others have been added (i.e., the distinction between 'dynamic' and 'static' behaviours). We present an updated, comprehensive catalog of documented animal tool use that indicates whether the behaviours observed included any 'true' tool use, whether the observations were limited to captive animals, whether tool manufacture has been observed, and whether the observed tool use was limited to only one individual and, thus, 'anecdotal' (i.e., N = 1). Such a catalog has not been attempted since Beck (1980). In addition to being a useful reference for behaviourists, this catalog demonstrates broad tool use and manufacture trends that may be of interest to phylogenists, evolutionary ecologists, and cognitive evolutionists. Tool use and tool manufacture are shown to be widespread across three phyla and seven classes of the animal kingdom. Moreover, there is complete overlap between the Aves and Mammalia orders in terms of the tool use categories (e.g., food extraction, food capture, agonism) arguing against any special abilities of mammals. The majority of tool users, almost 85% of the entries, use tools in only one of the tool use categories. Only members of the Passeriformes and Primates orders have been observed to use tools in four or more of the ten categories. Thus, observed tool use by some members of these two orders (e.g., Corvus, Papio) is qualitatively different from that of all other animal taxa. Finally, although there are similarities between Aves and Mammalia, and Primates and Passeriformes, primate tool use is qualitatively different. Approximately 35% of the entries for this order demonstrate a breadth of tool use (i.e., three or more categories by any one species) compared to other mammals (0%), Aves (2.4%), and the Passeriformes (3.1%). This greater breadth in tool use by some organisms may involve phylogenetic or cognitive differences — or may simply reflect differences in length and intensity of observations. The impact that tool usage may have had on groups' respective ecological niches and, through niche-construction, on their respective evolutionary trajectories remains a subject for future study.
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Learning to hunt: the role of experience in predator success
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Animal behaviour is a composite of innate and learned components. During their lifetimes, animals typically gain experience and manifest learning, thereby augmenting or modifying genetically determined, innate behaviour patterns. Following a training period during which predatory fish (jade perch, Scortum barcoo) were allocated to treatments and given experience of either live prey (mosquitofish, Gambusia holbrooki), freshly killed prey, or cichlid pellets with equal nutritional value, we tested the response of the predators to the prey in an experimental arena. Across all treatments, there was no difference in the number of attacks made by the predators on the prey, however the predators with experience of live fish prey were significantly more successful in capturing prey than those without previous experience of live prey. These results suggest that, in this piscivorous predator, the recognition of prey has an innate component, but that hunting efficiency is increased through experience. These findings are discussed in terms of their implications for the release of hatchery-reared fish into the wild, the majority of which are predatory.
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Disentangling defense: the function of spiny lobster sounds
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The function of anti-predator signalling is a complex, and often-overlooked, area of animal communication. The goal of this study was to examine the behavioural function of an antipredator acoustic signal in the ocean. We observed the acoustic and defensive behaviours of California spiny lobsters (Palinuridae: Panulirus interruptus) to a model predator, model conspecific and blank pole, both in the tank and in the field. We found that P. interruptus make a 'rasp' sound once physically contacted by an aggressor, rather than during the approach. The model predator and conspecific elicited no discernable changes in defensive behaviour, but the responses by the lobsters to aggressors in the tank versus field were distinct. Our results indicate that the spiny lobster's rasp is used as a startle or aposematic signal, which may be coupled with visual aposematism of their spines. Alternatively, the rasp may function as a vibratory escape mechanism or as an acoustic analogue to eye-spots. This study offers insights into the role of acoustic signalling in the marine environment and demonstrates a central role for sound production in spiny lobster ecology.
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Self-grooming by male meadow voles differs across copulation but is not affected by the risk and intensity of sperm competition
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Meadow voles, Microtus pennsylvanicus, self-groom before, during and after copulation, which may convey olfactory information to nearby conspecifics. Since males who self-groom at high rates were found to be attractive to females, it is possible that the copulating male may attempt to increase his attractiveness over that of other males who are present or nearby. In that the presence of other males affects sperm investment and can be used by males as an indicator of sperm competition, we tested the hypothesis that the presence of scent marks of other males near a sexually receptive female affects the self-grooming behaviour of males that encounter them. We did so by pairing a male and a female vole in the presence of the odours of one male conspecific, five male conspecifics, or no male conspecifics. The amount of time male voles self-groomed was not affected by the risk or intensity of sperm competition. We also tested the hypothesis that self-grooming behaviour of males differed depending on whether it was performed before, during, or after copulation. Male voles differed in the amount of time and the location on their body that they self-groomed before, during, and after copulation.
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