Animal Behaviour最新文献

Honey bees, Apis mellifera, are important pollinators, and they face many natural and anthropogenic challenges that affect their ability to collect the resources needed to maintain the colony. Foragers can make use of a remarkable repertoire of communication behaviours that help colonies to exploit their environment successfully. Food source availability is a key factor for colony success and, therefore, survival and reproduction. Few studies have investigated how food stores impact forager communication strategies and bee physiology. We experimentally manipulated honey stores and (1) quantified the production and following of waggle dances, (2) quantified the expression of immune-related genes using qPCR and (3) analysed fatty acids from bee abdomens using GC-MS 6 days after the experimental manipulation. We found that the number of waggle dances increased by about 60% when honey bees were starved of honey. The number of followers per dance, however, decreased, which may be due to a switch to proactive, solitary foraging or to the occurrence of more waggle dances. Waggle dance duration, the number of waggle phase followers that were followed and foraging distances were not affected by the treatments. Bees in starved colonies showed a higher expression of the gene defensin 1, which is an important predictor of overwinter survival, but there was no treatment effect on fatty acid content. Our results show that the amount of honey stored in hives affects communication behaviours and the investment in immunocompetence of bees, possibly to counter the negative health effects of nutritional stress. However, fat content does not seem to be affected in the time span of the study.

Consistent behavioural responses of individuals (i.e. personality) have been linked with reproductive output and success across a range of taxa. In species with biparental care, the behavioural compatibility of breeding partners may also affect reproductive output, perhaps because it allows greater pair coordination during breeding attempts. The aim of this study was to investigate whether pairs of greylag geese are assortatively paired for personality, and whether these traits within pairs affect reproductive output. We used repeated behavioural assays in the field to quantify three personality traits: activity (focal observations), boldness (flight initiation distance) and aggressiveness (response to mirror image). We assessed their correlation with three measures of reproductive output (clutch size, hatching success and fledging success). All three personality traits were significantly repeatable; however, we found no evidence that pairs within the flock routinely assortatively paired for any trait, regardless of the pair bond duration. Nevertheless, there may still be fitness benefits associated with pair compatibility. Pairs in which the partners were similar in average boldness had higher hatching success, although this trend was not found for clutch size or fledging success. These results suggest that the benefits of having similar predator defence strategies within pairs differ across the breeding cycle, resulting in no overall selection for assortative mating for boldness.

Echolocating bats observe their surroundings through continuous vocalization and echoreception. Sounds from nearby conspecifics may have a similar spectrum and high intensity. Bats emitting frequency-modulated (FM) echolocation calls avoid conspecific jamming sounds by altering their call frequency jamming avoidance response (JAR). Bats emitting constant frequency (CF)-FM can use other strategies to avoid jamming due to the different functions of the two acoustic components. In this study, seven Rhinolophus sinicus bats were used to conduct sound detection in both single individuals and pairs. We studied how these bats adjust the terminal FM (tFM) component of their calls when flying with conspecifics, and we tested whether acoustic adjustments are made to avoid jamming. Echolocation calls had shorter durations, reduced pulse intervals and higher tFM peak frequency and terminal frequency in the presence of conspecifics. The frequency differences of the tFM component between two bats did not increase in paired flights compared to their baseline difference, and the magnitude of spectral adjustments was independent of the baseline separations between bats. These results suggest that these bats do not use a JAR strategy to mitigate interference in the tFM component of calls. The call adjustments of CF-FM bats are more likely to be attention behaviours rather than being used for avoiding acoustic interference. Bats differentiate their own echoes and pulses from those of conspecifics through their respective acoustic signatures.

Animal sociality, the extent and manner in which conspecifics associate with each other, ultimately affects an individual's survival and reproductive success. It is shaped by the spatiotemporal configuration and composition of the social units (e.g. individual, pair, group) in a population. Here, we assessed the formation and structure of social networks of a presumed nonsocial species with individual-based movement data of 153 GPS-marked brown bears, Ursus arctos. We explored changes in the frequency of dyadic associations in relation to distinct seasonal patterns (i.e. mating, hyperphagia and hunting seasons) that affect bear behaviour. We found seasonally distinctive frequencies in brown bear associations throughout their active period and that reproduction was the main driver for associations in the population, that is, the highest frequency of associations occurred during the mating season and male–female dyads during the mating season included the majority (73%) of observed associations. We also observed dyadic associations during the hyperphagia and hunting seasons, but found no significant changes in frequency during these seasons. In addition, we found that social structures during both the mating and nonmating periods were nonrandom, that is, dyadic associations occurred more often than expected. Animal sociality is commonly viewed as a classification of social versus nonsocial, but our results suggest that it is rather a dynamic continuum primarily influenced by variation in a species' spatiotemporal configuration (i.e. seasonal movements, social unit structure) and demographic composition (i.e. age, sex). Our results also support the contention that studies focusing on animal sociality should include a sociospatial perspective, as both components are tightly linked. Since sociality can affect individual fitness, and vice versa, advancing the knowledge on assumed ‘solitary’ species is paramount for the conservation and sustainable management of their populations.

The cultural transmission of behaviour patterns across animal populations and between generations has been rigorously demonstrated in diverse vertebrate species and also in insects, but controversies continue about exactly what distinguishes nonhuman from human cultural learning. A contentious contemporary debate concerns a hypothetical ‘zone of latent solutions’ (ZLS), conceptualized as all that members of a species can acquire by individual learning. The ZLS hypothesis proposes that cumulative culture is restricted to humans because of a unique ability to copy behavioural innovations beyond our species' ZLS. Apes and other taxa are argued instead to be limited to copying only behaviours that are already within their ZLS, thus constraining their capacity for cumulative culture. Here I suggest that empirical tests of this hypothesis are scattered through the research literature covering social learning experiments and I collate relevant instances. Over 20 such studies spanning mammals, birds, fish and insects demonstrate social learning of novel actions new to the species that no individual acquires through its own efforts. Many offer particularly compelling refutation of the ZLS hypothesis because in addition to documenting an absence of individual level learning, they incorporate designs showing that observers match whichever of two alternative forms of action they witnessed or include multistep actions that are clearly challenging for individuals of the species studied to acquire by individual learning.

Organisms that nest in ant-defended trees presumably benefit from ants deterring potential enemies. How birds build a nest while surrounded by ant workers and how the ants are kept away from the fledglings are unknown. In Costa Rican dry forests, two bird species (streak-backed oriole, Icterus pustulatus, and yellow-olive flycatcher, Tolmomyias sulphurescens) preferentially nest in Pseudomyrmex ant-defended swollen-thorn acacias (Vachellia) and build the entire nest with fungal rhizomorphs. We tested whether rhizomorphs alter acacia ants' behaviour as a potential mechanism to deter aggressive ants from the birds’ nests. We also tested whether water increased the properties of the fungus, because birds nest during the rainy season. Hence, we recorded detailed observations of ant behaviour after contacting plant fibres (control) and dry and wet rhizomorphs. After touching the rhizomorphs, the probability of grooming and speeding up was higher (>65%) than after contacting plant fibres (<30%). Some ant behaviours were never observed with the plant fibres but had a higher probability of occurring (∼16–67%) after the ants touched rhizomorphs: gaster curling, biting a nestmate, spinning and wandering erratically. Water did not enhance putative rhizomorph properties. The results indicate signs of alarm, repellence and intoxication after interacting with rhizomorphs. Therefore, birds may benefit from using fungal rhizomorphs as it may deter the ants from entering the nest. This finding opens a venue for research questions, including whether the fungus effects are specific to acacia ants or can be generalized to other social hymenopterans that the birds choose to live nearby (e.g. wasps) or need to keep away from the nest (e.g. army ants).

Recent research on bird calls has unearthed a striking result: birds sometimes react to the calls of other species that are neither geographically nor phylogenetically close. One mechanism explaining this response may be the recognition of specific acoustic features, also present in their own vocalizations, rather than the recognition of complete notes, with the result that unfamiliar calls may be understood if they contain the critical feature. Parids and other passerines produce mobbing calls with similar properties that are responded to across species (i.e. noisy, large frequency range notes reaching low frequencies and with numerous harmonics) that are therefore good candidates for recognition based on features. In a playback experiment, we explored the featural interpretation hypothesis by testing the response of free-ranging great tits, Parus major, to artificial mobbing calls with varying acoustic properties. We first confirmed that they respond to artificial calls sharing all the targeted spectral properties (large frequency range, low frequency, noise and harmonics). In contrast, great tits did not respond to calls with the same rhythmicity but without the targeted features. We then tested whether great tits respond to calls that possess only one of the four above-mentioned properties. We show that great tits did not respond to any of the four treatments, and therefore no single specific spectral feature seems likely to explain great tits' response to unknown calls. We discuss alternative mechanisms for decoding novel calls, notably through a similarity threshold.

Sexual conflict occurs when the fitness interests of the two sexes do not align. Some traits shared by males and females (like mating rate) have sex-specific fitness optima that cannot be achieved simultaneously, and this conflict can favour the evolution of adaptations that benefit one sex but harm the other, like copulatory wounding. Prolonged copulation in damselflies can be seen as a clear example of sexual conflict: while it allows males to guard their partners, preventing them from remating, females cannot feed during copulation and may be more exposed to predators. Ischnura graellsii is one of the species of damselflies in the Coenagrionidae family characterized by females having a conspicuous vulvar spine on the sternum of the eighth abdominal segment, which makes contact with the male seminal vesicle during copulation. To investigate the role of the vulvar spine in sexual conflict, we evaluated whether there is a difference in copulation duration between females with the spine removed and those with an intact spine (control females) and studied the allometry between spine length and body length. We found that the vulvar spine had a significant effect on copulation duration, since males mated on average for 200 min with control females but increased copulation to 227 min with spineless females. The spine was allometric with wing size, but the slope depended on the regression method used. The male seminal vesicle has a depression exactly where the spine is in contact with it during copulation. There was no evidence of physical damage, and consequently, males mated to control and spineless females had similar longevity. We conclude that this spine allows females to reduce mating duration.

Foraging increases predation risk. As such, prey frequently attend to potential predator cues when making decisions about foraging behaviour. Environmental cues, such as light levels, can impact predation risk, and populations from different environments may vary in how they respond to such cues. Here we experimentally manipulated foraging conditions for a frugivorous bat, the Jamaican fruit bat, to ask whether individuals rapidly alter their foraging behaviour based on potential predator cues and light levels. Specifically, we ran bats in multiple foraging trials across a night in which we varied the level of ambient light or predator cues (auditory or visual) and measured latencies to feed. We found that bats in a more urban population were most affected by simulated full moonlight, delaying their foraging behaviour. In contrast, bats from a rural population were sensitive to simulated urban light. Furthermore, rural bats were also more sensitive to potential predator cues and foraged more rapidly in the presence of novel objects and auditory predator cues. These results reveal variation across populations of the same species with respect to their response to potential predator cues, possibly indicating differences in their evaluations of foraging risks.

Species recognition can be interpreted as the identification of sexual compatibility among individuals, which is related to the assessment of partner quality. This compatibility can be assessed using visual signals of conspecifics such as body coloration. Fiddler crabs constitute a group with a global distribution, comprising over 100 species with diverse colours. They perceive these body colours and use them for intersexual communication, primarily through signalling of the hypertrophied claw of males. However, few species have been investigated regarding the role of body coloration as a species-specific signal, and it remains unknown whether other body regions, such as the carapace, convey information about individual quality or species identity. Hence, this study aimed to examine whether carapace coloration of two sympatric fiddler crab species (Leptuca leptodactyla and Leptuca cumulanta) affects species recognition. To do this, we used individual females of L. leptodactyla that were subjected to a binomial choice of males with claws and carapaces reflecting different colours, simulating conspecifics (L. leptodactyla) or heterospecifics (L. cumulanta). We observed that females were unable to distinguish conspecifics from heterospecifics using only claw colour. On the other hand, we discovered that the white carapace coloration of L. leptodactyla was crucial for females to identify conspecific males. This is the first study to demonstrate that carapace coloration of male fiddler crabs functions in species recognition, reinforcing the idea that body traits beyond sexual ornaments can influence animal communication, affecting species identity and/or mate selection.