Animal Behaviour最新文献

The cognitive process of innovation in animals produces new or modified behaviours in response to new challenges. Common raccoons rely on their problem-solving ability to exploit anthropogenic resources that are not freely available. As a result, they are often involved in human–wildlife conflict. We used two food extraction tasks of varying difficulty levels to measure problem-solving ability in wild raccoons living in three Canadian protected areas. We conducted experiments in two distinct locations within each park based on human footprint: recreation and preservation zones. We also looked at the effect of the presence of conspecifics and of two behavioural traits (exploratory diversity and persistence) on performance. Performance differed between the puzzles, with one of them being easier to solve based on success rate and time to success. The zone (presence of humans) did not affect problem-solving performance, while there was a tendency for solving time to increase with the presence of conspecifics. Exploratory diversity was positively related to success rate and time taken to solve. Contrary to predictions, persistence did not improve performance. There were also individual differences in performance in term of success rate and time to completion. We encourage using multiple concurrent tests to evaluate problem solving with wild individuals. Overall, we provide additional evidence that raccoons are apt problem-solvers, with the potential to adapt to new foraging opportunities, and a relevant species to study innovation in mammals.

Crypsis is a common strategy used by animals to avoid detection. In many bird taxa, plumage colour patterns are assumed to play a role in crypsis, but few studies have directly measured plumage crypsis on ecologically relevant substrates from the perspective of relevant signal receivers. To address this gap, we tested whether the plumage colour patterns of three North American woodpeckers commonly found in New Jersey (U.S.A.) are more cryptic to avian predators on trees utilized for foraging than a random subset of trees from their habitat. We focused on the red-bellied woodpecker, Melanerpes carolinus, downy woodpecker, Dryobates pubescens, and hairy woodpecker, Leuconotopicus villosus. First, we took standardized photographs of the bark of trees on which we observed woodpeckers foraging, as well as photographs of the bark of trees from transects in the same area. Next, we superimposed standardized photographs of woodpecker specimens (dorsal view) onto the bark samples and adjusted the resulting images to estimate how they would appear to the visual system of an avian predator. We then estimated four types of achromatic crypsis from each bird/bark combination image: granularity matching, contrast matching, luminance matching and disruptive coloration. We also estimated how well woodpeckers matched the bark substrates in terms of colour by quantifying the degree of colour similarity in a colour space representing a typical avian predator. We found that woodpeckers were more cryptic against trees they utilized for foraging in terms of disruptive coloration, luminance matching and colour matching, suggesting that the need to be cryptic while foraging is likely to have shaped the evolution of woodpecker plumage patterning.

The behaviour and welfare of animals in captivity is of great importance to zoological collections, captive breeding programmes, food production and keepers of companion animals. Artificial lighting is commonly deficient in UV wavelengths, and use of such lighting for indoor animal enclosures could have significant impacts on the behaviour and welfare of animals to which UV wavelengths are visible. This includes birds, reptiles and fish, but also insects. Here we investigated the effect of UV-present and UV-absent light environments on the behaviour of Vanessa cardui, a butterfly that possesses a trichromatic visual system typical of many insects. We conducted behavioural experiments using a free-flight arena divided in half, where each half could be subjected to UV+ or UV− illumination. When lighting conditions for the two arena halves were the same, we found no significant differences in activity between UV+ and UV− light environments. However when lighting conditions for the two arena halves were different, butterflies showed a significant preference for the UV+ over the UV− half. This remained the case even when the overall intensity of UV+ illumination was less than that of UV− illumination. Our results suggest that UV-deficient artificial lighting conditions do not themselves affect the activity of butterflies, but that given a choice, butterflies prefer lighting that contains UV. Based on these findings, captive light environments can be designed that use supplementary lighting or filters to improve the welfare of captive insects, and the visitor experience.

The Vandenbergh effect, or male-mediated maturation, occurs when females reach sexual maturation upon exposure to a novel male. Male-mediated maturation is found across mammals, including in geladas, Theropithecus gelada, where it may be an adaptive counterstrategy to infanticide that follows the immigration of a new male; maturing after male immigration maximizes a female's chances of weaning her first offspring before the next infanticidal male immigrates (the ‘optimal timing hypothesis’). Alternatively, the nonadaptive ‘Bruce effect by-product hypothesis’ posits that male-mediated maturation in geladas (and possibly other mammals) is triggered by the same physiological changes that, in pregnant females, produce spontaneous abortion (the Bruce effect). We test both hypotheses using theory and observational data. We show that neither male-mediated maturation nor its associated hormonal changes occur in baboons (Papio cynocephalus × Papio anubis), a primate without the Bruce effect. An individual-based model suggests that male-mediated maturation should not evolve via adaptive evolution in either geladas or baboons. Finally, we derive the selection coefficient for male-mediated maturation and show it is likely to be very small because male-mediated maturation yields only marginal potential benefits unless the system is extremely fine-tuned. We conclude that male-mediated maturation in geladas is a by-product of the Bruce effect and more broadly that the Vandenbergh effect may be nonadaptive.

Parental effects, or parental phenotypes affecting offspring phenotypes, are widespread across taxa, yet there is significant variation within species regarding which offspring traits are affected. One reason for this observed variation could be the type of sensory cues present in the parental environment. By exposing parents to sensory cues containing different information about the same ecological stressor, we can determine whether information is integrated differently by parents based on cue type, leading to differential trait development in offspring. In this study, we utilized predator cues, which can be found in isolation and in combination in natural settings, to test whether cue type plays a role in differential phenotype expression in Trinidadian guppies, Poecilia reticulata. Parents were exposed to predator cues (visual, olfactory or both combined) over 14 days, after which we assessed life history traits, morphology and activity. Offspring were then raised with no predator cues and tested for morphology and activity in adulthood. No differences in life history traits were observed across 10 weeks. In line with previous findings, behaviour differed in both the parent and F1 generations in response to predator cues; however, effects were dependent on cue type and sex. Our results suggest that exposure to even a single sensory cue is strong enough to initiate a cascade of responses both in parent and F1 generations, and that interacting factors such as cue type and sex lend importance to understanding consequences of parent risk perception for offspring.

Foraging honey bees, Apis mellifera, need to interact with a range of moving objects, including flowers during windy conditions. Their ability to land on moving flowers, which they demonstrate regularly in nature, would require them to be able to detect, identify and compensate for the flowers' movements. We sought to investigate whether honey bees can distinguish between a stationary and an oscillating flower and whether they display a preference for one or the other. Different sets of individual free-flying honey bees were trained by presenting them with either a stationary or an oscillating flower-like stimulus, which were identical in shape and colour. Subsequently, when prompted to spontaneously choose between two identical flowers, one moving and the other stationary, honey bees exhibited a preference for the moving flower, regardless of whether they were previously trained on the stationary or the moving flower. In a further experiment, a separate set of bees were presented, after being trained, with a choice between stationary or oscillating flowers whose shape differed from the training flower. Here too, bees displayed a significant preference to land on the moving novel-shaped flower. These findings highlight the significance of flower movement to honey bee foraging behaviour. Moving objects like flowers could contribute additional visual salience which would enable easier detection, highlighting motion as an important descriptor used by insects to identify and interact with relevant environmental stimuli.

The navigational mechanisms of homing pigeons, Columba livia, have been extensively studied and represent a useful model for the navigation of birds and other animals. Pigeons navigate with an olfactory map and sun compass from unfamiliar areas and, in familiar areas, are largely guided by visual landscape cues, following stereotyped and idiosyncratic routes. However, the mechanisms by which they gain familiarity, improve their navigation and transition between navigational strategies during learning are not fully understood. Addressing these outstanding questions in this navigational model will help to improve our understanding of navigational ontogeny. We sought to investigate whether passive exposure to the cues at a site, without release, was sufficient for navigational learning, given that pigeons can determine the home direction before taking off. We exposed pigeons to cues at a novel site before returning them to the site the next day and releasing them alongside controls. We found no differences in the directional distributions, mean vector lengths, virtual vanishing times, efficiency indices or homing efficiency indices between birds that had and had not previously visited the site. We therefore found no evidence to suggest that passive exposure to the cues at a novel site was sufficient to facilitate a detectable improvement in navigational performance. There are three possible explanations for this result: first, a larger sample size would have detected a weak effect of learning; second, passive exposure to a release site is insufficient to generate navigational learning; and third, pigeons learn from passive exposure but do not rely upon this information, showing no difference in performance, despite learning. We discuss these three explanations with reference to previous findings on navigational learning in homing pigeons. We suggest that experiments should continue to examine navigational ontogeny in homing pigeons to help address this major problem for the field of navigation.

Chorusing animals constantly face the challenge of overcoming background noises. To minimize the masking of their own calls by conspecific or heterospecific calls, plasticity in call timing serves as an alternative tactic for chorusing animals. We examined how male rhacophorid treefrogs, Zhangixalus prasinatus, adjust their call timing in response to various noisy environments. When exposed to periodic white noise disturbances with brief silent intervals, the frogs accurately avoided overlapping with the noise and delivered their calls in the silent gaps. Moreover, they delivered long calls earlier than short calls during the silent periods to accommodate the longer duration within a brief silent gap. When exposed to noises of varying frequencies, the frogs specifically avoided medium-frequency noise, which closely matched their own call frequency. This phenomenon was also observed in experiments testing the aggregating behaviour of male frogs; they ceased to aggregate towards conspecific calls when interfered with by medium-frequency noise, whereas high-frequency and low-frequency noise interferences did not elicit the same behaviour. Compared to high-quality males, frogs with low SM_i (scaled mass index) exhibited greater plasticity in call timing, indicating a condition-dependent tactic for energy allocation. Such behavioural plasticity in call timing was reflected in natural soundscape recordings. Our recordings revealed that, as a result of these adaptive strategies, males tended to avoid overlapping their calls with background noises in their natural habitats. Our research provides evidence that call plasticity is an effective strategy for chorusing animals to respond to noise at both individual and population levels. Furthermore, our study suggests that plasticity in call timing is a complex decision-making behaviour involving the consideration of noise properties and an individual's body condition.

Offspring provisioning can act as a proxy of resource acquisition and vary with parental sex and age. Age-related variation can arise from individual experience and senescence, but also from selective disappearance of poor-quality parents. Distinguishing between these processes and quantifying their effect on the resource acquisition and fate of individual chicks requires longitudinal monitoring of known-age individuals, which is still rare. In our longitudinal study, we observed offspring provisioning of common terns, Sterna hirundo, across a 6-year period and analysed provisioning behaviour from both a parental and offspring perspective. Using repeated measures of provisioning of individual parents, our analyses showed that provisioning did not increase with age, but that parents that were observed at older ages provisioned more, suggesting selective disappearance of parents that provisioned less. Parental provisioning was higher in males than females and increased with brood size in both sexes. For offspring, energetic acquisition declined with hatching order and increased with age. Acquisition from the mother increased faster with chick age than that from the father, and mothers distributed their provisioning more evenly across chicks of different hatching order. Parental age, however, did not affect the energetic acquisition of the offspring. The early energetic acquisition rate of chicks predicted their fledging success, but not fledging mass. When decomposing effects on energetic provisioning and acquisition rate into effects on feeding rate, prey energetic density and prey size, we found that all arose from variation in feeding rate. Overall, these results therefore show that both parents and offspring vary in quality, which is reflected in their feeding rate.