Showing papers in "Behaviour in 2010"

Bondedness and sociality

Abstract: Approaches to sociality have, in the past, focused either on group typologies or on the functional aspects of relationships (mate choice, parental investment decisions). In contrast, the nature of the social relationships that scale from the individual-level behavioural decisions to the emergent properties represented by group typology has received almost no attention at all. We argue that that there is now a need to refocus attention on the bonding processes that give rise to social groups. However, we lack any kind of language with which to describe or classify these operationally, in part perhaps because social bonding is emotional (and, hence, 'felt'). One task for the future is, therefore, to identify suitable indices that can be used to compare the degree of bondedness between individual animals both between species and, within species, between individual dyads in such a way as to be able to test functional questions.

Animal tool use: current definitions and an updated comprehensive catalog

Abstract: 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.

Close social associations in animals and humans : functions and mechanisms of friendship

Abstract: Both humans and group-living animals associate and behave affiliatively more with some individuals than others. Human friendship has long been acknowledged, and recently scientists studying animal behaviour have started using the term friendship for close social associates in animals. Yet, while biologists describe friends as social tools to enhance fitness, social scientists describe human friendship as unconditional. We investigate whether these different descriptions reflect true differences in human friendship and animal close social associations or are a by-product of different research approaches: namely social scientists focussing on proximate and biologists on ultimate explanations. We first stress the importance of similar measures to determine close social associations, thereafter examine their ultimate benefits and proximate motivations, and discuss the latest findings on the central-neural regulation of social bonds. We conclude that both human friendship and animal close social associations are ultimately beneficial. On the proximate level, motivations for friendship in humans and for close social associations in animals are not necessarily based on benefits and are often unconditional. Moreover, humans share with many animals a similar physiological basis of sociality. Therefore, biologists and social scientist describe the same phenomenon, and the use of the term friendship for animals seems justified.

Revolutionary coalitions in male rhesus macaques

Abstract: [Coalitions between animals are found in a variety of taxa, but are most common among primates. Here, we present data on the relative abundance of male–male coalitions within a group of free-ranging rhesus macaques, a species in which male coalitions are reportedly rare or absent. We then report a series of revolutionary coalitions among subordinates against higher ranked individuals that transformed male dominance relationships. We use these data to test theoretical model predictions about revolutionary rank-changing coalitions among primate males. We also use data on male age, rank, group residency length, associations and relative fighting ability (morphometric variables), to test predictions about coalition members' characteristics. Contrary to model predictions, coalition sizes were large, but consistent with predictions, targets were high ranking, and members middle ranking. Coalition males were more similar to each other in rank, group residency length and body mass than other males were. Coalition members were also associates (spent more time with other members than non-members did in the preceding months), and had longer canines than other males. Our results show that males forming revolutionary coalitions were from a specific part of the male distribution and represent the first systematic analysis of male–male coalitions in free-ranging rhesus macaques., Coalitions between animals are found in a variety of taxa, but are most common among primates. Here, we present data on the relative abundance of male–male coalitions within a group of free-ranging rhesus macaques, a species in which male coalitions are reportedly rare or absent. We then report a series of revolutionary coalitions among subordinates against higher ranked individuals that transformed male dominance relationships. We use these data to test theoretical model predictions about revolutionary rank-changing coalitions among primate males. We also use data on male age, rank, group residency length, associations and relative fighting ability (morphometric variables), to test predictions about coalition members' characteristics. Contrary to model predictions, coalition sizes were large, but consistent with predictions, targets were high ranking, and members middle ranking. Coalition males were more similar to each other in rank, group residency length and body mass than other males were. Coalition members were also associates (spent more time with other members than non-members did in the preceding months), and had longer canines than other males. Our results show that males forming revolutionary coalitions were from a specific part of the male distribution and represent the first systematic analysis of male–male coalitions in free-ranging rhesus macaques.]

The development of pandanus tool manufacture in wild New Caledonian crows

Abstract: New Caledonian crows have remarkably complex tool manufacturing abilities. Here we document the ontogeny of pandanus tool manufacture in wild NC crows. Our results show that the development of wide pandanus tool manufacture is a lengthy process comparable to the development of tool use in primates. Juveniles pass through four main stages of tool manufacture before they acquire adult-like proficiency. By 10 to 12 months of age most juveniles can manufacture tools with adult-like competency, but adult-like speed in manufacture and tool use is only reached in their second year. Whilst individual trial and error learning appears to play a major role in juveniles' development of pandanus tool skills, this development takes place in an environment scaffolded by parental birds. Juveniles stay close to their parents for their first year and have ample opportunity to observe parental tool manufacture and use. Parents influence the juveniles' early learning by leading them to Pandanus sp. trees where they provide discarded tools for early tool use. Exposure to parental tools might help juveniles form a mental template of functional tool design and, thus, facilitate the faithful transmission of local design traditions.

The effect of predator appetite, prey warning coloration and luminance on predator foraging decisions

Abstract: Aposematic prey advertise their defence to visually hunting predators using conspicuous warning colouration. Established theory predicts that aposematic signals should evolve towards increased conspicuousness and similarity to enhance predator education. Contrary to theoretical expectations, there is often considerable within- and between-species variation in aposematic signals of animals sharing the same ecological niche, phylogeny and predators. This may be explained by varying responses of predators that weaken the selection pressure for a consistent signal. By presenting painted mealworm larvae as prey to great tits as predators we tested if different aposematic colour patterns have different values as a means of initial protection and learnt avoidance from predators, and how widely birds generalise their learnt avoidance to other colour patterns. We also investigated how the colour and luminance of the pattern elements affect predator attack decisions. Finally, we studied if hunger affects the predators' reaction to differently coloured prey. We found that similarity in colour was not crucial to the survival of aposematic prey, since learnt avoidance was not influenced by colour, and predators remembered and generalised widely in their learnt avoidance to other colours. We found that initial avoidance was, however, apparently influenced by luminance contrast. Interestingly, the predators' level of hunger was more important than the colour of the aposematic signal in determining birds' decisions to attack chemically-defended insect larvae. We discuss the implications of visual properties of prey colour pattern and predator appetite for the evolution of insect defences and warning signals. In addition we propose a methodological approach to effectively control for predator appetite in laboratory experiments.

The consequences of parasitic infections for host behavioural correlations and repeatability

Abstract: Summary The lifecycles of parasites are often complex, with multiple successive hosts. Many parasites have evolved the ability to modify the behaviour of their present host to increase the chance of transmission to the next host. Few studies to date have considered how a suite of related behavioural traits in the host can be affected by parasitic manipulations. The present study investigated the effect of two trematode parasites, Coitocaecum parvum and Microphallus sp., on the behaviour of their amphipod host (Paracalliope fluviatilis) in a behavioural syndrome framework. This framework focused on the correlations between, and repeatabilities within suites of behavioural traits. Three activity-related behavioural tests were conducted: phototaxis (response to light), horizontal activity, and vertical distribution. Infection by C. parvum did not have any significant effect on any of the behavioural traits investigated. However, amphipods infected by Microphallus sp. spent less time in the light. Surprisingly, amphipods harbouring Microphallus sp. also showed stronger behavioural correlations in general, compared to those of uninfected hosts. Furthermore, the repeatability of the phototaxis test for infected amphipods was lower than that of uninfected amphipods. Given these results, we encourage future studies to use this behavioural syndrome framework.

Acoustic communication in the Asian elephant, Elephas maximus maximus

Abstract: Summary Existing knowledge of acoustic communication in elephants is based primarily on African species (Loxodonta africana and Loxodonta cyclotis). There has been comparatively less study of communication in Asian elephants (Elephas maximus). In order to provide a basis for understanding the evolution and function of acoustic communication in proboscideans, I present a quantitative description of vocal communication in wild Asian elephants. I classify calls by acoustic features into 8 ‘single’ calls, 5 ‘combination’ calls and one possibly unique male call for a total of at least 14 distinct call types. Some of these vocalizations have never before been described. Certain low-frequency calls are individually distinct. Acoustic signals occur in a wide range of social contexts, with some differences in call production among age and sex classes.

Reproductive behaviour of wild zebrafish (Danio rerio) in large tanks

Abstract: Summary Zebrafish are an intensively studied model organism, and yet there are no studies describing the reproductive behaviour of wild zebrafish Here we investigated the reproductive behaviour of wild-caught zebrafish (Danio rerio) from India in large (1100 l) aquaria containing gravel and plants and low population densities We observed the behaviour of focal individuals in groups of eight fish (equal sex ratio; 28 replicates; 42 h total observations), and found similarities to what has been previously described for domesticated fish in small aquaria However, we also found several notable differences and, in particular, we found that the fish usually spawned in pairs rather than in groups, and we found evidence for sexual selection We conducted additional observations of wild-derived fish in smaller, conventional aquaria (17 l) and high densities, and found that group spawning is more common in these conditions Taken together, our observations suggest that high rates of group spawning may be an artefact of small aquaria, which may reduce or eliminate sexual selection by giving more opportunities for sneaky males and preventing females’ from choosing their mates

Support for a role of colour vision in mate choice in the nocturnal European treefrog (Hyla arborea)

Abstract: Summary Although nocturnal anurans use vision for reproductive communication, it remains unknown whether they see colours at night. Here, we explored this question in the European treefrog (Hyla arborea), by conducting two mate choice experiments under controlled light conditions. Experiments involved static male models with identical calls but different vocal sac colouration combining chromatic (red/orange) and brightness (dark/light) information. We found that females preferred dark red over light orange, evidencing for the first time a visually-guided mate choice in nocturnal diffuse light conditions. Conversely, females did not discriminate between dark orange and light red. The preference for dark over light in the first but not in the second experiment suggested that females had not only access to brightness cues but also to chromatic cues. The absence of preference may originate from females choosing at random in a situation where colour and brightness cues may convey contradictory information about male quality or from individual heterogeneity in the type of cues used for mate choice. Overall, these experiments provide the first support for the use of colour vision in a nocturnal amphibian.

Variation in kin bias: species differences and time constraints in macaques

Abstract: Recent evidence suggests that female grooming kin bias in rhesus and Tibetan macaques varies within groups over time in a manner that is consistent with the time constraints model. Here we test the same hypothesis for Tonkean macaques, using data from a corral-living group collected between 1987 and 2002.We also use published data to ask whether time constraints can explain variation across the three macaque species and/or whether these species appear to show inherent differences in kin bias based on their species' social styles, as predicted by the phylogenetic model. Several predictions of the time constraints model were supported for Tonkean macaques: as the number of potential grooming partners increased, females groomed similar amounts, but displayed decreased per capita amounts of grooming, focused their grooming on a subset of potential partners, and displayed more intense grooming kin bias. Although numbers of potential partners affected all three species similarly, species differences in kin bias were sustained and were related to species social styles independently of numbers of potential partners.We suggest that grooming kin bias represents a social reaction norm, in which species display qualitatively similar, but inherently different ranges of response to the same current conditions.

Dominance among female white-faced capuchin monkeys (Cebus capucinus): hierarchical linearity, nepotism, strength and stability

Abstract: Research on Old World primates provided the foundation for understanding competitive strategies resulting from social and ecological pressures. The neotropical primate, Cebus capucinus shares many social patterns with Old World cercopithecines (e.g., female philopatry, male dispersal), which may contribute to similar expression of competitive strategies. To clarify the nature of dominance patterns among female white-faced capuchins we examined hierarchical linearity, rank acquisition, matrilineal rank inheritance, hierarchical strength and stability. We collected focal data on 22 adult females (2008) and long-term dominance data (1986–2008) on 33 adult females in Sector Santa Rosa, Costa Rica. Females displayed linear hierarchies based on the direction of dyadic submission. At sexual maturity females quickly acquired rank positions beneath their mother and older sisters. Hierarchies were considered strong based on high proportions of food-related agonism, short latency to detection of hierarchies (21 h/female) and low directional inconsistency scores (<5%). Hierarchies were considered stable based on lack of tied submissive interactions (indicative of uncontested rank positions), low rates of rank change (0.510 changes/year), and long-term stability in matrilineal rank order. These findings enhance our understanding of capuchin social systems and how the competitive strategies of white-faced capuchins compare to those of Old World primates.

California towhee vocal duets are multi-functional signals for multiple receivers

Abstract: Avian vocal duets provide a model system for studying the evolution and production of complex signals which require input from multiple individuals. Duets serve a variety of communication functions in diverse species. To explore the function of duetting in California towhees (Pipilo crissalis) I collected behavioural data from a marked population, conducted sound playback experiments, and removed males from established pairs to observe the behaviour of new partners. Results indicate that California towhees use duets during extra-pair communication with conspecifics and during intra-pair communication between duetting partners. During the breeding season duetting frequency peaked during the chick-rearing period and was low during periods of high female fertility. Playbacks provoked similar levels of aggressive response from male and female territory holders. Mated pairs duetted in response to simulated intrusion by conspecific males, females and pairs. California towhee duets briefly increased in frequency after pairing, and showed no evidence of change due to learning. Duets facilitate spatial and behavioural coordination by mates, which should allow them to more effectively perform behaviours related to mutual reproductive success. No single existing hypothesis adequately explains vocal duetting among California towhees. Instead, duets function in multiple contexts and provide multiple potential benefits.

Predicting the effect of climate change on aggregation behaviour in four species of terrestrial isopods

Abstract: 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.

Perceptual mechanism for vocal individual recognition in jungle crows (Corvus macrorhynchos): contact call signature and discrimination

Abstract: In long-range fission-fusion complex societies, individuals are often recognized by audiovocal signals because of long-range propagation. The signature voice system is a well-known mechanism involving both acoustic individuality of a certain call type and discrimination ability. Previous studies on vocal individual recognition of birds have emphasized its involvement in breeding contexts such as mate, parent and offspring, and territorial-neighbour recognition. However, there has been less focus on the recognition of non-breeding flock members despite the socio-ecological demand of such ability in the complex social lives of highly social birds including corvids. Here we report a signature voice system in jungle crows by showing both acoustic individuality of contact calls and discrimination ability. We first performed a discriminant functional analysis on contact ka calls of five crows to examine their discriminatory potential and demonstrate inter-individual distinctions. We next used an operant conditioning to verify the perceptual ability to discriminate non-breeding familiar conspecifics based on ka calls. Four of the five crows successfully transferred discrimination of individual calls to the novel ka calls. Our results provide the first evidence of a signature voice system as a perceptual mechanism for individual recognition of familiar individuals in non-breeding flocks of a highly social crow.

Male guppies (Poecilia reticulata) adjust their mate choice behaviour to the presence of an audience

Abstract: In recent years analyzing animal behaviour in light of the social environment has become widely accepted Especially many mating interactions do not happen in privacy, but in a public arena, raising the question of how this affects the behaviour of both the focal individual and the observing audience individual We studied in feral guppies whether male preferences for female body size, a correlate of fecundity, are influenced by the presence of another male, the audience We also studied whether the audience was influenced by the observed interactions These two aspects are not normally studied together Furthermore, we were also interested in the question of how long changes in the behaviour of the audience male might last We found that male preferences measured as nipping/approaches decreased in the presence of an audience Furthermore, the audience males showed no preference for larger females when tested right after the interaction with the focal male, but returned to the typical preference for larger females after 24 h Our study highlights the relevance of the social conditions under which mating decisions are being made

Group effect on fertility, survival and silk production in the web spinner Tetranychus urticae (Acari: Tetranychidae) during colony foundation

Abstract: In many vertebrates and invertebrates, individuals reared in isolation show biological modifications compared with those reared in groups of two of more. The spider mite Tetranychus urticae is characterised by a communal organization and displays some forms of cooperative behaviour (aggregation and common web spinning). To evaluate the potential fitness cost or gain of group living, we investigated the effect of being in group on life history parameters (silk production, fecundity, death rate, feeding rate). In this respect, virgin single females and grouped females (two to six individuals) were compared every day for 5 days. Grouped mites produced significantly more web/mite per day (since the second day of experiment) and more eggs/mite per day (since the fourth day of experiment) than single mites. Moreover, single mites had a higher death rate than mites living in groups. However, no difference was found concerning feeding rate. We assume that mites could benefit from the web production of other individuals and invested resources in other activities such as egg production. We showed that these group effects already exist in small groups. In natural conditions with a higher group size, the impact of group living might be stronger for the dynamics of T. urticae populations and the colony foundation.

Food imprinting revisited: early learning in foraging predatory mites

Abstract: Learning is a ubiquitous phenomenon in foraging animals, allowing behavioural optimisation in variable environments. Food imprinting is a specific form of learning restricted to the early stages of life and with long lasting consequences. However, since coining of the term four decades ago, the uniqueness of food imprinting has been largely questioned due to a putative mechanistic similarity with associative learning. Here, we demonstrate food imprinting in the predatory mite Neoseiulus californicus , which primarily feeds on spider mites but may use thrips as alternative prey. Brief (24 h) exposure to thrips (contact without feeding) early in life resulted in shorter attack latencies and consistently higher predation rates on thrips during adulthood. Predation and oviposition rates were positively correlated but oviposition did not differ between naive and experienced females. Our results suggest that food imprinting is indeed special because, unlike associative learning, it occurred without reinforcement, was restricted to a sensitive phase and persisted into adulthood. Food imprinting seems particularly advantageous when prey species availability varies little within generations and a given prey is difficult to ingest for young small but not older larger life stages. Food imprintability could be used to improve the efficacy of biocontrol agents such as N. californicus .

The challenge of finding a high-quality male: a treefrog solution based on female assessment of male calls

Abstract: In the context of sexual selection through mate choice, it has recently been suggested that the effectiveness of intersexual communication is affected not only by the honesty of male sexual signals but also by the number of signal components simultaneously used to convey information. We investigated female use of acoustic components in the chorusing treefrog Hyla arborea using two-choice phonotaxis tests. Females showed a significant preference for higher call rates and calls of short duration, as well as for higher call amplitudes. They also favoured lower peak frequencies. Since this call characteristic was negatively correlated with body weight, such a preference should lead to their selecting larger males. Females also exhibited a marginal preference for longer call bouts. The reliability of the multiple call components involved in mate choice in H. arborea are discussed, as well as the validity of these results for mate choice in the natural context of a noisy anuran chorus.

Disentangling defense: the function of spiny lobster sounds

Abstract: 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.

Black-capped chickadee dawn choruses are interactive communication networks

Abstract: Summary The dawn chorus of songbirds provides an ideal opportunity to study communication networks because multiple singers are within signalling range of each other, permitting eavesdropping by both males and females. Using an Acoustic Location System, we examined the dawn chorus singing behaviour of male black-capped chickadees (Poecile atricapillus )i n 15 neighbourhoods to determine whether singing behaviour is consistent with the communication network model. We calculated levels of frequency matching for 19 focal males and all of their neighbours. The observed level of frequency matching was greater than expected by chance. All males were involved in multi-way matching at dawn and often matched two or three neighbours simultaneously. The identity of individuals involved in three-way matches was related to both previous winter-flock membership and the relative dominance rank of the interacting males. We show that male black-capped chickadee dawn choruses are interactive communication networks where males are involved in high levels of matching with neighbours, and they match multiple individuals both simultaneously and sequentially. Additionally, the existence of multi-way matching and the identities of individuals involved suggest that individual males may eavesdrop at dawn. This is the first study to quantify network communication during the dawn chorus in multiple neighbourhoods.

Sign and strength of emotional arousal: vocal correlates of positive and negative attitudes to humans in silver foxes (Vulpes vulpes)

Abstract: Summary The hypothesis of similarity in trends of acoustic characteristics regardless of the sign of emotional arousal, positive or negative, has been advanced based on human vocalizations. For non-human mammals, testing is complicated because the same stimulus cannot evoke opposite (positive and negative) internal states, to trigger the respective vocalizations. To resolve this concern, we designed an experimental procedure using Tame and Aggressive strains of silver foxes, with genetically predetermined positive or negative emotional responses to humans respectively. We analyzed features of vocalizations produced by callers at different fox‐human distances, assuming changes in vocal responses reflect the shifts of human-related positive arousal in Tame foxes and human-related negative arousal in Aggressive foxes. Both strains showed similar trends for changes in calling rate and proportion of time spent vocalizing toward higher levels in response to greater emotional arousal, positive in Tame foxes and negative in Aggressive foxes. At the same time, strains showed distinctive trends for the proportions of different call types and maximum amplitude frequency. We infer that the variables with similar trends reflect the strength of emotional arousal, regardless of triggering internal states, whereas variables with distinctive trends are specifically related to the sign of emotion in silver fox.

Potential amplification of territorial advertisement markings by black-backed jackals (Canis mesomelas)

Abstract: Optimality theory suggests that territorial scent marks are under selective pressure through the information they provide about competitive quality/reproductive status and so should be situated to maximize their detection to alert conspecifics that they are intruding upon the territory of a resident. Factors that increase mark detectability are consequently beneficial to both resident and intruder by allowing tactical withdrawal by intruders and, thus, reducing the costs of conflict. We tested whether black-backed jackals ( Canis mesomelas ) preferentially deposited territory marks on substrates (rocks or faeces) in two separate sites in South Africa's Addo Elephant National Park. Elephant ( Loxodonta africana ) dung piles were preferentially defecated upon by jackals in both sites. Where black rhinoceros ( Diceros bicornis ) was present at relatively high density, rhino middens were also preferentially marked by jackals; however, jackals resorted to defecating on elevated surfaces, such as rocks, where rhinos were scarce. We hypothesize that the odour of elephant and rhino dung may increase the detectability of jackal markings while providing an additional olfactory signal component, while rocks and elephant dung provide visual amplification. Manipulative experimentation will be necessary to confirm our multimodal amplification hypothesis.

Effects of gravidity on the locomotor performance and escape behaviour of two lizard populations: the importance of habitat structure

Abstract: In lizards, locomotor costs of gravidity may depend on habitat structure and refuge availability. We compared the locomotor performance and escape tactics in the laboratory, before and after oviposition, of two populations of Psammodromus algirus separated by 700 m altitude. When gravid, females escaped using a larger number of slower and shorter runs, and had lower temperatures at the time of trial, than after oviposition. Some of these effects differed between populations: when gravid, but not after oviposition, low-elevation females ran shorter distances at a slower average speed than high-elevation ones. Low-elevation females laid their clutches earlier than high-elevation ones, which conditioned their lower speed when gravid in simultaneous running trials. However, their escape distances were still shorter after controlling for the effects of temperature and laying date. In the field, refuge availability was lower at the low-elevation site, where females spent more time inside refuges and perching above ground. The shorter escape distance of low-elevation females may, thus, represent a behavioural response to minimize detectability, especially if predator avoidance depends primarily on whether or not the lizard is seen by the predator. Such behavioural adjustments might inhibit selection for evolutionary shifts in the performance of gravid females.

Vocal duets in a nonpasserine: an examination of territory defence and neighbour–stranger discrimination in a neighbourhood of barred owls

Abstract: Mated pairs of animals in many taxa coordinate their vocalizations into duets, yet most research on duetting has focused on songbirds. Here we examine the duetting behaviour of barred owls (Strix varia) by addressing three questions: (1) Do owl duets play a role in territorial interactions? (2) Do owls discriminate between duets of neighbours versus strangers? (3) Do duets play a role in extended communication among a neighbourhood of owls? We simulated territorial encounters by broadcasting duets of adjacent, territory-holding owls (neighbours) and distant owls (strangers). We assessed responses to playback using a 3.5-km transect of automated recording devices. We compared vocal activity during a pre-playback period and following both playback treatments for the focal pair, their neighbours, and more distant owls within the neighbourhood. After playback, focal owls gave significantly more duets, vocalized for a longer duration, and emphasized different call types compared to the pre-playback period, demonstrating that barred owls use duets in territory defence. Focal owls did not respond significantly differently to neighbours versus strangers. At the neighbourhood level, owls did not behave differently during silent pre-playback periods or post-playback periods. Our results suggest barred owl duets function primarily in immediate confrontations during territorial conflicts.

Learning to hunt: the role of experience in predator success.

Abstract: 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.

American cockroaches prefer four cardinal geomagnetic positions at rest

Abstract: A specific behavior based on the ability to perceive the magnetic field has been described in several species: when resting or grazing animals take up a position placing their main body axis parallel with the North-South or East-West geomagnetic axes, which is referred to as magnetic alignment The adaptive significance of this behavior remains an enigma No experiments have been made to date to demonstrate conclusively whether that orientation will adequately change in response to an experimental rotation of geomagnetic axes which is a key step to prove the use of exclusively magnetic cues for orientation In our study, we identified a preference regarding the four cardinal magnetic axes, ie a quadrimodal alignment both in natural and in 60deg rotated fields The study gives the original evidence that quadrimodal alignment is a type of animal behavior specifically related to the cardinal magnetic axes of the Earth

Phenoloxidase activity and melanization do not always covary with sexual trait expression in Hetaerina damselflies (Insecta: Calopterygidae)

Abstract: Sexual selection theory indicates that males use sexual traits to signal immune ability, a hypothesis known as the immunocompetence principle. A positive relationship between sexual traits and immune ability is not always present. Here we illustrate this pattern by using five damselfly species in the genus Hetaerina. Previous studies have documented a positive correlation between sexual trait expression (wing spot size) and immune ability in members of this genus. These studies have also documented that there are fitness and energetic costs of producing and bearing wing pigmentation. First we used five Hetaerina species to investigate the correlation between spot size and phenoloxidase (PO) activity (a key insect immune component) in two contrasting seasons. Second, we experimentally challenged males of two Hetaerina species and correlated spot size with PO activity and melanization ability. Results indicate either a positive relationship, a negative relationship or, more commonly, no relationship at all between immune components and wing pigmentation. Season did not predict any of these relationships or expression of spot size and PO activity. These results, although limited to two immune components, indicate that the relationship between sexual trait expression and immunity is not always consistent.

Nest defence in a cuckoo host: great reed warblers risk themselves equally for their own and parasitic chicks

Abstract: Hosts of the common cuckoo (Cuculus canorus) may foster a foreign chick instead of raising their own progeny, which incurs a significant cost to their fitness. Chick recognition or discrimination is, however, rare in cuckoo hosts and has been investigated exclusively in relation to nestling provisioning. Here we test for the first time whether hosts differ in the willingness of risk-taking when they care for own or parasitic offspring. We investigated nest defence in great reed warblers (Acrocephalus arundinaceus) against three types of nest intruders while controlling for the number of chicks and the length of the nestling period. The most parsimonious linear mixed-effects model showed that the type of intruder and nest identity significantly explained variation in host aggression. Our results demonstrated that the hosts discriminated two predators from an innocuous species and that some nest owners consistently defended their nests more intensely than others. However, the birds did not differ in their responses in relation to the nest contents, indicating that neither the nestling species, nor the length of previous parental investment influenced the intensity of nest defence. Our findings are, therefore, in accordance with the general scarcity of chick discrimination by cuckoo hosts.

Occurrence and duration of post-copulatory mate guarding in a spider with last sperm precedence

Abstract: One male strategy to prevent female re-mating is post-copulatory mate guarding. In the pholcid spider Holocnemus pluchei last male's fertilization success is around 74% and females remain receptive after copulation. It is, thus, reasonable to suppose that males should engage in post-copulatory mate guarding. Chronologically, the present study focused on the following aspects: (1) to determine if male permanence near females corresponds to mate guarding. For this, a second male (intruder) was introduced. Time of permanence, distance and behaviour of residents did not change whether or not an intruder was present; (2) to investigate the duration of mate guarding and male distance to the female in a time series intervals after copulation. Males remained close to females during 14 h keeping a distance of less than 15 cm; (3) to evaluate whether guarding duration is influenced by female sexual receptivity. We found that 24 h after the first copulation, when the resident was placed again next to the female, he tried to re-mate; and (4) to examine differences in paternity in relation to whether or not the resident exerted guarding. P2 was higher when second males copulated again within the first 6 h compared to 24 h after the first copulation.