Showing papers in "Behaviour in 2011"

The evolution of the Lombard effect: 100 years of psychoacoustic research

Abstract: On the occasion of the centenary of the discovery of the Lombard effect, we review the literature on noise-dependent regulation of vocal amplitude in humans and other animals The article addresses the scientific and the biological history of the Lombard effect: first, it sketches the evolution of the study of the Lombard effect, and second it reflects on the biological evolution of the effect itself By comparing the findings from anurans, birds and mammals, we try to trace back the phylogenetic origins of this basic vocal mechanism for acoustic communication in noise The current evidence suggests two alternative parsimonious hypotheses: either the Lombard effect is the outcome of a convergent evolution in birds and mammals or it may be a synapomorphy of all amniotes If the latter is true, then the Lombard effect would have evolved to maintain vocal communication in the presence of noise more than 300 million years ago

Carotenoid-based signals in behavioural ecology : a review

Abstract: Carotenoids are among the most prevalent pigments used in animal signals and are also important for a range of physiological functions. These concomitant roles havemade carotenoidbased signals a po ...

The brain opioid theory of social attachment: a review of the evidence

Abstract: The psychology of close human relationships is increasingly well understood and our understanding of the neurobiology of the onset of pairbonding behaviour in a range of species has benefited from the use of rodent-based models. However, the human literature has suffered from a lack of focus upon the unique nature of primate social bonds and has so far failed to adequately identify the neurobiological and behavioural mechanisms which maintain these complex, diverse and enduring social networks. One neurobiological mechanism that has been overlooked is the endogenous opioid system. Though less explicitly researched than the more familiar oxytocin/vasopressin system, there is considerable evidence that the opioids play a fundamental role in sociality, especially in the primates. This review summarises our current understanding of the evidence for the role of this system in prosocial behaviour in non-primate mammals, nonhuman primates and humans. An important conclusion is that the opioid system may play a more central role in sociality in primates (including humans) than in other mammalian taxa. © 2011 Koninklijke Brill NV, Leiden.

Underwater components of humpback whale bubble-net feeding behaviour

Abstract: Summary Humpback whales (Megaptera novaeangliae) employ a unique and complex foraging behaviour — bubble-netting — that involves expelling air underwater to form a vertical cylinder-ring of bubbles around prey. We used digital suction cup tags (DTAGs) that concurrently measure pitch, roll, heading, depth and sound (96 kHz sampling rate), to provide the first depiction of the underwater behaviours in which humpback whales engage during bubble-net feeding. Body mechanics and swim paths were analysed using custom visualization software that animates the underwater track of the whale and quantifies tag sensor values. Bubble production was identified aurally and through spectrographic analysis of tag audio records. We identified two classes of behaviour (upward-spiral; 6 animals, 118 events and double-loop; 3 animals, 182 events) that whales used to create bubble nets. Specifically, we show the actual swim path of the whales (e.g., number of revolutions, turning rate, depth interval of spiral), when and where in the process bubbles were expelled and the pattern of bubble expulsion used by the animals. Relative to other baleanopterids, bubble-netting humpbacks demonstrate increased manoeuvrability probably aided by a unique hydrodynamicly enhanced body form. We identified an approximately 20 m depth or depth interval limit to the use of bubble nets and suggest that this limit is due to the physics of bubble dispersal to which humpback whales have behaviourally adapted. All animals were feeding with at

Compensatory traits and the evolution of male ornaments

Abstract: How ornaments that are used during mate choice and rival assessment remain reliable has been a source of contention for many years. Such signals are hypothesized to be costly (i.e., 'handicaps'), but empirical studies testing for costs of sexually selected ornaments are equivocal at best, contradictory at worst. We review recent studies finding compensation for sexually selected ornaments, in both intra- and inter-specific studies, suggesting that other traits evolve to mitigate costs of ornaments. We synthesize these studies to elucidate the role of compensatory traits in the evolution of reliable ornaments and explain how selection to reduce ornament costs may influence aspects of the phenotype that are not subjected to direct sexual selection and may obscure our ability to directly measure ornament costs. Both intraspecific studies and comparative studies in a phylogenetic framework are important for our understanding of how the costs of signals may be reduced by compensation, but each approach answers different questions about ornament evolution. We also elaborate on a general theoretical model that can be useful when testing for costs of ornaments in correlational and experimental studies. We recommend that future investigators should consider compensatory traits when testing for ornament costs, especially when manipulating ornamentation.

Numerical competence in animals, with an insight from ants

Abstract: Summary We survey a variety of experimental paradigms for studying animal abilities to count, to understand numerical information and to perform simple arithmetic operations. There is a huge body of evidence that different forms and elements of quantitative judgement and numerical competence are spread across a wide range of species, both vertebrate and invertebrate. Here we pay particular attention to the display of numerical competence in ants. The reason is that most of the existing experimental schemes for studying numerical processing in animals, although often elegant, are restricted by studying subjects at the individual level, or by the use of artificial communicative systems. In contrast, the information-theoretic approach that was elaborated for studying number-related skills in ants employs their own communicative means and, thus, does not require the subjects to solve any artificial learning problems, such as learning intermediary languages, or even learning to solve multiple choice problems. Using this approach, it was discovered that members of highly social ant species possessed numerical competence. They were shown to be able to pass information about numbers and to perform simple arithmetic operations with small numbers. We suggest that applying ideas of information theory and using the natural communication systems of highly social animals can open new horizons in studying numerical cognition.

Dispersal in male ursine colobus monkeys (Colobus vellerosus): influence of age, rank and contact with other groups on dispersal decisions

Abstract: [Dispersal is male-biased in ursine colobus monkeys ( Colobus vellerosus ), although female dispersal also occurs (Teichroeb et al., 2009). Here we describe the process of male dispersal and its connection with between-group encounters (BGEs, N = 444) and male incursions (when males left their group and approached within 50 m of another group; N = 128) at the Boabeng-Fiema Monkey Sanctuary in central Ghana. Through BGEs and incursions, particularly those with non-aggressive interactions between individuals in different groups (BGEs, N = 17; incursions, N = 4), males could probably assess other groups for dispersal opportunities. There was a trend for males to perform incursions more frequently before emigrating voluntarily than involuntarily. Incursions were often performed towards the group that the male eventually transferred to. Incursions by alpha males were temporally shorter and more aggressive than those by non-alpha males. We suggest that non-alpha males used incursions to assess other groups for breeding or dispersal opportunities, whereas alpha males performed incursions mainly to convey information about their quality to neighbouring males and females. Male emigrations/disappearances (natal N = 20, secondary N = 43, unknown N = 9) and immigrations ( N = 62) were recorded for seven groups during ten years (2000– 2010). Alpha males always emigrated involuntarily. Parallel emigration and immigration occurred. Males often immigrated into groups with a more favourable adult male/adult female ratio and improved their rank, both of which likely increased their mating opportunities. The most fitting ultimate explanation for both natal and secondary male dispersal in this population was the intrasexual competition for mates hypothesis, as males of all ages appeared to emigrate to improve their reproductive opportunities., Dispersal is male-biased in ursine colobus monkeys (Colobus vellerosus), although female dispersal also occurs (Teichroeb et al., 2009). Here we describe the process of male dispersal and its connection with between-group encounters (BGEs, N = 444) and male incursions (when males left their group and approached within 50 m of another group; N = 128) at the Boabeng-Fiema Monkey Sanctuary in central Ghana. Through BGEs and incursions, particularly those with non-aggressive interactions between individuals in different groups (BGEs, N = 17; incursions, N = 4), males could probably assess other groups for dispersal opportunities. There was a trend for males to perform incursions more frequently before emigrating voluntarily than involuntarily. Incursions were often performed towards the group that the male eventually transferred to. Incursions by alpha males were temporally shorter and more aggressive than those by non-alpha males. We suggest that non-alpha males used incursions to assess other groups for breeding or dispersal opportunities, whereas alpha males performed incursions mainly to convey information about their quality to neighbouring males and females. Male emigrations/disappearances (natal N = 20, secondary N = 43, unknown N = 9) and immigrations (N = 62) were recorded for seven groups during ten years (2000– 2010). Alpha males always emigrated involuntarily. Parallel emigration and immigration occurred. Males often immigrated into groups with a more favourable adult male/adult female ratio and improved their rank, both of which likely increased their mating opportunities. The most fitting ultimate explanation for both natal and secondary male dispersal in this population was the intrasexual competition for mates hypothesis, as males of all ages appeared to emigrate to improve their reproductive opportunities.]

When sounds collide: the effect of anthropogenic noise on a breeding assemblage of frogs in Belize, Central America

Abstract: Many organisms depend on acoustic communication for myriad functions, and have evolved behaviours to minimize effects of naturally occurring acoustic interference. However, as habitats are subject to increased alteration, anthropogenic noise becomes unavoidable, and how animals overcome such interference is not well understood. In most ecosystems, only a subset of frog species is associated with disturbed habitats; the ability of these species to overcome exogenous noise suggests that habitat associations may be related to species' response to noise. We tested the hypothesis that frogs associated with largely undisturbed forest habitat would be less likely to increase call output in response to exogenous noise than would those associated with disturbed or open habitat. While this relationship was not significant, we found a slight trend supporting the hypothesis. We then asked whether anthropogenic noise affects chorus tenure at individual- or at chorus-levels. Male frogs exposed to anthropogenic noise decreased both the number of days present at the chorus and the nightly chorus duration relative to controls. Because females generally join choruses late at night to breed, the effects of noise shown here are likely to substantially decrease frog reproductive success; thus, the acoustic environment may play an important role in shaping population dynamics and in amphibian declines.

Evolution of advertisement calls in African clawed frogs

Abstract: For most frogs, advertisement calls are essential for reproductive success, conveying information on species identity, male quality, sexual state and location. While the evolutionary divergence of call characters has been examined in a number of species, the relative impacts of genetic drift or natural and sexual selection remain unclear. Insights into the evolutionary trajectory of vocal signals can be gained by examining how advertisement calls vary in a phylogenetic context. Evolution by genetic drift would be supported if more closely related species express more similar songs. Conversely, a poor correlation between evolutionary history and song expression would suggest evolution shaped by natural or sexual selection. Here, we measure seven song characters in 20 described and two undescribed species of African clawed frogs (genera Xenopus and Silurana) and four populations of X. laevis. We identify three call types — click, burst and trill — that can be distinguished by click number, call rate and intensity modulation. A fourth type is biphasic, consisting of two of the above. Call types vary in complexity from the simplest, a click, to the most complex, a biphasic call. Maximum parsimony analysis of variation in call type suggests that the ancestral type was of intermediate complexity. Each call type evolved independently more than once and call type is typically not shared by closely related species. These results indicate that call type is homoplasious and has low phylogenetic signal. We conclude that the evolution of call type is not due to genetic drift, but is under selective pressure.

Maternal inheritance and exploratory-boldness behavioural syndrome in zebrafish

Abstract: Correlated behavioural traits (behavioural syndromes) influence ecological interactions and, in turn, how natural selection shapes the evolution of behaviour. A major axis of intraspecific behavioural variation is the exploratory-boldness behavioural syndrome. Here, we describe how we sorted wild-caught zebrafish (Danio rerio) for increasing exploratory tendency using a serial open field maze. We then transferred test fish to a predator-inspection apparatus. Highly exploratory individuals spent more time near a novel predator than non-exploratory individuals, showing behavioural consistency indicative of an exploratory-boldness behavioural syndrome. We then bred the zebrafish to create F1 offspring from four crosses: (1) exploratory × exploratory, (2) non-exploratory × non-exploratory, (3) exploratory females × non-exploratory males and (4) non-exploratory females × exploratory males. F1 offspring were tested in a miniature serial open-field maze similar to the one used to sort the adults. Offspring of exploratory females were always highly exploratory regardless of the behavioural traits of the father suggesting that maternal effects may influence expression of exploratory-boldness behavioural syndrome in zebrafish.

Spontaneous innovation for future deception in a male chimpanzee

Abstract: The ability to invent means to deceive others, where the deception lies in the perceptually or contextually detached future, appears to require the coordination of sophisticated cognitive skills toward a single goal. Meanwhile innovation for a current situation has been observed in a wide range of species. Planning, on the one hand, and the social cognition required for deception on the other, have been linked to one another, both from a co-evolutionary and a neuroanatomical perspective. Innovation and deception have also been suggested to be connected in their nature of relying on novelty.

Hatchling Australian freshwater crocodiles rapidly learn to avoid toxic invasive cane toads

Abstract: Predicting the ecological impacts of invasive species on native fauna is a formidable challenge for conservation biologists. One way to deal with that challenge is to stage encounters between the invader and native species in the laboratory, to illuminate likely outcomes of encounters in the wild. The invasion of the highly toxic cane toad Rhinella marina across tropical Australia threatens many frog-eating predators, including freshwater crocodiles (Crocodylus johnstoni). To predict the impact of cane toads on crocodiles, we need to know whether crocodiles will attack cane toads, and whether predators that survive the toads' poisons will learn to avoid toads. We quantified these traits under laboratory conditions in hatchling freshwater crocodiles from Lake Argyle in Western Australia. All toad-naive hatchling crocodiles attacked toads during their first encounter, and none showed signs of overt illness after consuming toads. However, crocodiles rapidly learnt to avoid toads as prey, and only four out of the 10 crocodiles attacked toads during subsequent encounters. Compared to control (toadnaive) conspecifics, toad-smart crocodiles inflicted fewer bites on toads, held toads in their mouths for shorter time periods, and were more likely to reject toads as prey. In the field, toads were consumed more rarely than native frogs. Our results show that hatchling freshwater crocodiles can rapidly learn to avoid cane toads as prey. Hence, even if toads cause mortality of larger crocodiles (as happens in some areas), populations may recover via hatchling recruitment.

Social rank, neophobia and observational learning in black-capped chickadees

Abstract: Behavioural syndromes are consistent patterns in behavioural tendencies across varying situations in individual animals. Although studies of behavioural syndromes are becoming more common, few draw connections to social dominance. Black-capped chickadees ( Poecile atricapillus ) flock in winter, and dominance hierarchies play an important role in governing social behaviour within these flocks. Dominants and subordinates may also pursue different foraging strategies and differ in risk-taking, such as consuming novel food. In this study we examined whether social rank was related to neophobia and observational learning in chickadees. We measured individual reactions to novelty and individual differences in foragingtask learning ability. Latencies to approach a variety of novel stimuli were consistent within individuals. Social rank was related to individual reactions to novelty but not to observational learning ability. Lower-ranking individuals were less neophobic, which was consistent with the pattern of their dominance hierarchy in the wild where dominants control access to preferred resources and restrict subordinates to forage in riskier novel environments.

Male phenotype predicts extra-pair paternity in pied flycatchers

Abstract: Consejeria de Medio Ambiente, Comunidad de Madrid and Delegacion de Medio Ambiente, Junta de Castilla-La Mancha gave us working permissions. This work was supported by projects PAC05-006-2 (to J.A.D.) and CGL2006-07481/BOS (to J.C. Senar). D.C. was supported by a grant from the Ministerio de Educacion y Ciencia (I3P-BDP2005).

Aggression, but not testosterone, is associated to oxidative status in a free-living vertebrate

Abstract: Aggression often shows large inter-individual variation, but high intra-individual consistency. Although the physiological basis and direct costs of aggression are generally well known, less is known about the physiological costs such as increased oxidative stress (OS). This can occur via increased leakage of oxidants during high metabolic demands such as physical activity, or by hormones regulating both metabolism and aggression. Here we address this within a natural population of White's skinks, Egernia whitii; a species in which both sexes exhibit consistent aggressive phenotypes, and sex-specific associations between testosterone and aggression. The results reveal that males' aggressive phenotype, independent of testosterone, was positively associated with antioxidant capacity (OXY), while there was no significant association in females. Oxidative damage (ROM) and oxidative stress index (OI), were not influenced by aggressive phenotype or testosterone, but showed borderline positive associations with body size (i.e., age). The results failed to show that high testosterone increases OS. Instead, OS may be related to sex-specific behavioural patterns associated with aggressive phenotype such as territory and mate acquisition. Although experimental work is needed to identify the causal links for these patterns, the results highlight the need to consider proximate mechanisms to understand constraints on phenotypic variation.

Song-type sharing and matching in a bird with very large song repertoires, the tropical mockingbird

Abstract: Summary Song-type matching, a behaviour of some songbirds in which one individual replies to another’s song with a matching song type, has been studied primarily in birds that have small to moderately sized song repertoires (<15 song types) and that share only a few song types with neighbours. Few previous studies have examined song-type matching in species with very large song repertoires, in which birds can share larger numbers of songs with neighbours and matching particular song types might be more challenging. Here we describe frequent and rapid song-type matching in a population of tropical mockingbirds, Mimus gilvus. Males had repertoire sizes of about 133 distinct song types on average which were delivered with high versatility. Territorial neighbours shared significantly more song types than did nonneighbours, and neighbouring males matched each other’s songs frequently and often with surprising speed. Overlapping of songs occurred at approximately chance levels. Song-type matching in these birds could indicate more than just aggressive intentions, which is the presumed function of this behaviour in species with smaller repertoires. In tropical mockingbirds, rapidly matching the songs of neighbours could provide information to listeners about a singer’s experience or abilities.

Temperament traits and microhabitat use in bullhead, **Cottus perifretum** : fish associated with complex habitats are less aggressive

Abstract: Temperament traits have been linked to fitness-related functional contexts such as dispersal or mating attractiveness, but few studies have linked inter-individual differences in habitat use to temperament traits. Therefore, we conducted a three-month field study with weekly tracking to define the individual microhabitat use of bullhead (Cottus perifretum). The species is known for its dependence on structured habitats. At the end of the field-survey, bullhead were recaptured and tested in the laboratory for five temperament traits: boldness, interest in novel food, novel environment activity, aggressiveness and activity. Repeated trait tests (activity, r = 0.439; novel environment activity, r = 0.422) and habitat complexity use (r = 0.568) indicated behavioural consistency. Overall, bullhead significantly preferred complex habitats, such as branch jams, while avoiding open water. Individual frequency in the use of complex habitats could not be attributed to size or sex differences, but was significantly negatively correlated to the level of aggressiveness. We hypothesize that this relationship was caused by a higher level of aggressive defence of less structured territories. Other temperament traits were not significantly linked to individual habitat use. To our knowledge, this study is the first to show a relationship between aggressiveness measured under laboratory conditions and the use of complex habitats in situ.

Coalitions destabilize dyadic dominance relationships in male Barbary macaques (Macaca sylvanus)

Abstract: Dyadic agonistic dominance relationships are thought to result from asymmetries in both intrinsic and extrinsic power. One form of extrinsic power is the ability to solicit agonistic support from other individuals. In extreme cases extrinsic power differences may override intrinsic power differences so that physically inferior individuals attain rank positions above stronger competitors. In other cases superior extrinsic power in physically inferior individuals may destabilize the otherwise clear dominance relationships. We tested this prediction with observational data on adult males in one of three free-ranging groups of Barbary macaques at Affenberg Salem, Germany. All prime males that were subjects of this study were at least 5–8 years (average 10 years) younger than the old post-prime males that were all subordinate to them. Assuming large age differences to reflect large intrinsic/physical power differences, interactions between these prime and the old males allowed investigation of the separate effects of intrinsic and extrinsic power asymmetries on dominance relationships. We estimated relationship instability using four different estimates (counter aggression, conflicts initiated by aggression from the subordinate, spontaneous submissions by dominants, and decided conflicts won by the subordinate). Relationship instability did not decrease with increasing asymmetry in intrinsic power. Instead, all four measures of relationship instability were positively related to the number of times the dominant in a dyad was target of destabilizing coalitions. Destabilizing coalitions targeted dominant males in old male–prime male dyads more often than in old male–old male dyads. Consequently, old males had less stable relationships with the much stronger prime males than with each other. We conclude that extrinsic power asymmetries predicted the instability of dyadic dominance relationships and may systematically override intrinsic power asymmetries.

Evolution of calling songs as multicomponent signals in crickets (Orthoptera: Grylloidea: Eneopterinae)

Abstract: Calling songs of crickets are multi-component signals that serve several purposes in the species biology. The multiple functions of calling songs reflect the multiple selective forces shaping signal parameters. We test several predictions about signal evolution at a phylogenetic scale, taking into account the way signals are produced and used. We addressed these predictions in a diverse cricket clade, the Eneopterinae subfamily, using an independently derived phylogeny. Acoustic analyses of the calling songs of 24 eneopterine species permitted the definition of 35 acoustic characters describing the spectral and temporal properties of the songs. These characters proved informative for their phylogenetic content. Our main conclusions were that eneopterine calling songs have evolved as multiple independent characters (atomised evolution hypothesis), although they partly depended on the influence of emitting structures. They experienced a general tendency toward more information delivered per unit time and were driven toward equivalent temporal patterns through the combined action of inheritance from ancestors, parallelism and character convergence.

Antipredator behavior and cue recognition by multiple Everglades prey to a novel cichlid predator

Abstract: Novel predator introductions are thought to have a high impact on native prey, especially in freshwater systems. Prey may fail to recognize predators as a threat, or show inappropriate or ineffective responses. The ability of prey to recognize and respond appropriately to novel predators may depend on the prey's use of general or specific cues to detect predation threats. We used laboratory experiments to examine the ability of three native Everglades prey species (Eastern mosquitofish, flagfish and riverine grass shrimp) to respond to the presence, as well as to the chemical and visual cues of a native predator (warmouth) and a recently-introduced non-native predator (African jewelfish). We used prey from populations that had not previously encountered jewelfish. Despite this novelty, the native warmouth and nonnative jewelfish had overall similar predatory effects, except on mosquitofish, which suffered higher warmouth predation. When predators were present, the three prey taxa showed consistent and strong responses to the non-native jewelfish, which were similar in magnitude to the responses exhibited to the native warmouth. When cues were presented, fish prey responded largely to chemical cues, while shrimp showed no response to either chemical or visual cues. Overall, responses by mosquitofish and flagfish to chemical cues indicated low differentiation among cue types, with similar responses to general and specific cues. The fact that antipredator behaviours were similar toward native and non-native predators suggests that the susceptibility to a novel fish predator may be similar to that of native fishes, and prey may overcome predator novelty, at least when predators are confamilial to other common and longer-established non-native threats.

Proximate mechanisms leading to large male-mating advantage in the Andrew's toad, Bufo andrewsi

Abstract: In animals, body size is a prominent trait that generally positively affects ecological and reproductive success. Through field observations and experiments, we investigated the effects of two mechanisms of sexual selection on large male mating advantage in the Andrew's toad, Bufo andrewsi, a species widely distributed in western China. We observed a large male mating advantage in the field. Field data were corroborated by experiments in which large males mated more frequently than smaller males. However, in female preference tests, in which females could choose freely between two males differing in body size, choosing females showed no size preference while many females did not exert mate choice at all. We suggest that the large male mating advantage observed in the field and laboratory is caused by competition among males rather than by female choice.

An evolutionary interpretation of the effect of gender and sexual orientation on human mate selection preferences, as indicated by an analysis of personal advertisements

Abstract: Sexual selection and parental investment theory have been used to study mate selection for many years and for much of that time has been applied to humans, with the prediction that humans will follow the general mammalian pattern. One aspect of human mate selection that has received much less attention is that of same sex mate selection. The present study used an analysis of 800 personal advertisements from print and online media to determine the mate selection criteria of four mating groups — males seeking females (MF), females seeking males (FM), males seeking males (MM) and females seeking females (FF). Consistent with results of earlier studies, heterosexual males (MF) in our study preferred significantly younger partners than heterosexual females (FM), offered physical attractiveness significantly less often than FM, sought resources significantly less often than FM and indicated a willingness to make a commitment significantly more often than FM. Homosexual females (FF) differed from heterosexual females by the same four criteria and in the same direction as heterosexual males, in clear contrast to hypotheses suggesting that homosexuals only differ from heterosexuals of the same gender in choice of sexual object. Homosexual males (MM) differed from heterosexual males in only two criteria, both of which exhibited an exaggerated male pattern, possibly because MM are unaffected by the sexual strategies of females; MM sought attractiveness (even) more than MF and offered resources less than MF. Homosexual men, thus, exhibited no evidence of selection on the mate preference characteristics predicted by sexual selection theory. In contrast, the proximate mate selection preferences of female homosexuals were consistent with the assumption that in their case procreation is irrelevant to mate selection.

Age, sex and escape behaviour in the Striped Plateau Lizard (Sceloporus virgatus) and the Mountain Spiny Lizard (S. jarrovii), with a review of age and sex effects on escape by lizards

Abstract: Escape behaviour often differs between sexes, reproductive states and ages. Escape theory predicts that flight initiation distance (FID = predator–prey distance when escape begins) increases as predation risk and fitness increase, and decreases as cost of escaping increases. Similar predictions hold for distance fled and refuge entry, suggesting that age and sex differences in escape behaviour may occur when risk, fitness, and opportunity costs differ. I studied such differences in two lizard species and reviewed relevant literature on escape by lizards. In Sceloporus virgatus no difference occurred between sexes or female reproductive states in FID, distance fled, distance from refuge, or probability of entering refuge. In S. jarrovii juveniles had shorter FID and distance fled than adults; juveniles were closer than females to refuge, but this did not affect FID or distance fled. Juveniles were more likely than adults to be on rocks and use them as refuges. The literature review showed that sexual dimorphism in FID occurs in about 1/5 of species (male FID usually > female FID), but distance fled differed between sexes in only 1 of 21 species. Juveniles had shorter FID than adults in all of five species; the relationship between age and distance fled was highly variable. Reasons for patterns of age/sex differences are discussed. Because age and sex differences in these factors and escape strategy can alter multiple components affecting optimality, sometimes in opposite ways, these factors and escape strategy must be known to predict effects of age, sex and reproductive state on escape.

The calling songs of male spring field crickets (Gryllus veletis) change as males age

Abstract: Sexual traits are typically thought to convey information about a male's quality or condition. Female preference for older males has been documented in many taxa, but the evidence that males signal their age is inconclusive. We investigated lifetime patterns of acoustic mate attraction signalling in a longitudinal study of the spring field cricket, Gryllus veletis. We recorded males continuously throughout their lives, such that every pulse of sound produced by every male was analyzed. Our study answers two main questions: (1) Do calls change as males age? Our results reveal that the calls of male spring field crickets change with age; the calls of older males were quieter, with more silent periods within and between chirps, and produced less often than those of younger males. As males aged most of the changes in call structure reflect decreased calling effort. (2) What is the relationship between calling effort and longevity? Lifetime calling effort was positively related to longevity, such that males that called the most over their life also lived longer than males that called less. Together, our findings provide the most thorough exploration of lifetime signalling patterns in crickets to date.

Responses of seed-hoarding behaviour to conspecific audiences in scatter- and/or larder-hoarding rodents

Abstract: In rodents, the presence of conspecifics may trigger changes in food-hoarding behaviour when the risk of pilferage is perceived to be high. It is not clear how hoarding intensity and hoarding patterns (scatter- or larder-hoarding) of rodents change in the presence of conspecific audiences or if the nature of the change is different between sexes, or influenced by body size. We investigated these questions in Korean field mice (Apodemus peninsulae) (KFM, showing both scatter- and larder-hoarding behaviours) and Chinese white-bellied rats (Niviventer confucianus) (CWBR, showing larder-hoarding behaviours only) through carefully controlled experiments in outdoor enclosures. We observed the seed-hoarding behaviour of focal females and males of each species in the presence of a conspecific audience of the opposite sex, same sex, and alone (control treatment). We found both rodent species increased hoarding efforts when faced with an increased pilferage risk (presence of audiences), supporting the pilferage tolerance hypotheses or forage competition hypotheses. In contrast with previous studies, we found potential pilferage risk can result in a KFM shift from scatterhoarding to larder-hoarding, supporting the larder defence hypotheses, not the catastrophic avoidance hypotheses. However, the relationship between hoarding patterns, and body size or sex, is rather complex and requires further investigation.

Spawning behaviour of Arctic charr (Salvelinus alpinus): risk of sperm competition and timing of milt release for sneaker and dominant males

Abstract: Summary A mismatch in timing between the release of male and female gametes in external fertilizers may lead to failed fertilization or, under sperm competition, reduced paternity. To quantify the actual synchrony of gamete release and the level of sperm competition we placed video cameras on two spawning grounds of a naturally spawning population of Arctic charr (Salvelinus alpinus). Females release eggs in response to courting (quivering) in less than 1% of the cases, yet to both dominant and sneaker males. That is, females initiated spawning with dominant males in 73.3% of the recorded spawning events. Although the actual spawning seems to be largely under female control, 55.6% of spawning events occur under sperm competition. The average time delay between dominant and sneaker males milt release under sperm competition is 0.68 s. Thus, female reproductive decisions seem to be strongly influenced by male-male competition and this may have set the stage for the evolution and maintenance of the observed plasticity in ejaculate characteristics of male charr.

Interactions between the Asian koel (Eudynamys scolopacea) and its hosts

Abstract: The interaction between brood parasitic cuckoos and their hosts represents a traditional example of coevolution, whereby obligate interspecific brood parasitic cuckoos completely rely on their hosts to do their parental care for them by laying their eggs in the host’s nest. This thesis brings together a great deal of information documenting and clarifying the interactions between different species of hosts and their respective parasitic cuckoos in Bangladesh. I recorded parasitism rates to determine the extent of brood parasitism and to identify the host species that were parasitised by sympatric cuckoos. Four parasitic cuckoos were documented: the Asian koel ( Eudynamys scolopacea), the common hawk cuckoo (Cuculus varius; previously known as Hierococcyx varius), the pied cuckoo (Clamator jacobinus) and the Indian cuckoo (Cuculus micropterus). These cuckoos were sympatric and parasitised different host species, including the house crow (Corvus splendens), the long-tailed shrike (Lanius schach), the common myna (Acridotheres tristis), the jungle babbler (Turdoides striatus) and the black drongo (Dicrurus macrocercus). All of these cuckoo species are obligate brood parasites. The Asian koel utilised the following three hosts: the house crow, the common myna and the long-tailed shrike. The latter was recorded for the first time as a host for the Asian koel in Bangladesh. We found that koel eggs were highly non-mimetic to those of common myna and long-tailed shrike, but showed good mimicry to house crow eggs. Indian cuckoos showed excellent egg mimicry with the eggs of their black drongo hosts, as did common hawk cuckoos and pied cuckoos with their jungle babbler host. The hosts accepted the eggs of all four cuckoo species. However, the common myna was more likely to abandon nests parasitised by the koel than unparasitised ones. All of the host species suffered the costs of koel parasitism, showing reduced breeding success. Proximity to fruit trees was an important predictor of the probability of parasitism in the three koel host species studied. There was a significant positive relationship between nest volume and probability of parasitism by Asian koels. Furthermore, the colonial breeding house crows suffered comparatively less parasitism than the other two koel host species. Long-tailed shrike nests close to conspecific neighbours were less likely to be parasitised, and the risk of parasitism was increased in nests lower to the ground. The risk of parasitism increased during the breeding season for house crows and common mynas. All three Asian koel hosts tolerated multiple parasitism. We investigated whether there was any interspecific competition among the sympatric cuckoos. In theory, sympatric parasites should show niche segregation through variation in host use. As predicted, each cuckoo species parasitised different host species; however, host use overlapped in common hawk cuckoos and pied cuckoos, but interspecific competition was reduced because these two cuckoo species have different breeding seasons. Furthermore, there was a significant difference in parasitism rate among the three main habitats: human habitations, mixed scrub forests and monoculture plantations. This indicated that different cuckoos favour specific habitats, even if their favourite host also occurs elsewhere. Finally, I tested responses against foreign eggs by the cuckoo hosts as well as by potential cuckoo hosts in the study area. For this purpose, I used differently sized and coloured model eggs. Common mynas and jungle babblers accepted all non-mimetic eggs, as did most of the house crows (91 %). Long-tailed shrikes rejected 75 % of the non-mimetic model eggs. Finally, black drongos turned out to be strong rejectors and could do so without damaging any of their own eggs, most likely because they grasped and ejected the non-mimetic model egg. This result indicates that the black drongo has been in a coevolutionary arms race with the Indian cuckoo since drongos accepted mimetic cuckoo eggs. Species such as the Oriental magpie robin (Copsychus saularis), red-vented bulbul (Pycnonotus cafer) and Asian pied starling (Gracupica contra), which likely have no history of interaction with cuckoos, accepted 100 % of the non-mimetic model eggs. In conclusion, our findings describe host nest use cues used by the Asian koel, which may provide background for further studies in other sympatric brood parasites. In spite of the high degree of acceptance of parasitic eggs, the breeding success of both cuckoos and hosts should be more closely studied to obtain a better understanding of the costs of parasitism. Future experimental studies are highly recommended to achieve a better understanding of host responses to Asian cuckoo species.

Singing, allogrooming, and allomarking behaviour during inter- and intra-sexual encounters in the Neotropical short-tailed singing mouse (Scotinomys teguina)

Abstract: In this study we determine whether brief interactions with unfamiliar conspecifics stimulate audible singing behaviour in the Neotropical short-tailed singing mouse (Scotinomys teguina). Specifically, we examine whether intra- or inter-sexual interactions elicit singing in males in a neutral-arena design. We conducted two experiments. In experiment 1, we recorded singing behaviour of male subjects both before and after a brief exposure to a female mouse. Males significantly increased their singing behaviour after the exposure to the female, as compared to prior to the exposure. In experiment 2, we compared the singing behaviour of male test subjects after a brief exposure with one of three different treatment animals: a male, a non-oestrous female and an oestrous female. We found that males are most likely to sing after an interaction with a female, regardless of her reproductive condition. Male subjects sang significantly less following an interaction with another male. Although spontaneous singing is known to occur in males and females, opposite sex elicited-singing behaviour was found to be sexually dimorphic. An interaction with a male was not effective in eliciting singing in females. In experiment 2, we also recorded incidences of allogrooming and allomarking by males during the interactions with males, non-oestrous females, and oestrous females. Male allogrooming and allomarking behaviours using the mid-ventral sebaceous gland tend to occur more frequently during interactions with females as compared to males, but were significantly different only in the case of allogrooming. Thus, this study clearly suggests sex differences in singing, allogrooming and allomarking, and a likely relationship between these behaviours and courtship in this Neotropical rodent.

Good fences make good neighbours: the role of landmarks in territory partitioning in the rose bitterling (Rhodeus ocellatus)

Abstract: Territorial animals sometimes use conspicuous natural landmarks as boundaries to their territories. The utilization of territory-demarcating landmarks may have evolved to limit the costs of territorial defence, since the adoption of clearly defined boundaries by opponents in adjacent territories can reduce the overall rate of aggressive encounters, which can be energetically expensive or might result in injury. Here the role of artificial landmarks as boundaries was tested in territorial male rose bitterling ( Rhodeus ocellatus ), a fish with a resourcebased mating system. Pairs of size-matched territorial males were permitted to interact for short periods in an otherwise featureless aquarium with an obvious landmark at the shared boundary of their territory either present or absent. The presence of the territory-demarcating landmark significantly reduced both the frequency of territorial incursions by males into adjacent territories and the rate of territorial displays. Males showed individual differences in their propensity to enter the territory of a rival, irrespective of the presence of a territorydemarcating landmark. These results suggest that the cost of defence of a territory may be reduced by utilizing territory-demarcating landmarks, in accordance with the predictions of theoretical models.