Ethology最新文献

Reciprocity is one of the most prominent explanations for the evolution of stable cooperation. Although reciprocity has been studied for decades in numerous animal species and behavioural contexts, its underlying proximate mechanisms remain unclear. Domestic dogs provide a useful model species for the study of proximate mechanisms, though there are currently inconsistent findings regarding dogs' propensity to reciprocate. Here, we investigated whether, after minimal training, pet dogs would press a button, which remotely controlled a food dispenser, to deliver food to an enclosure occupied by a helpful conspecific that had provided them with food or an unhelpful conspecific that had not provided them with food. We included an asocial control condition in which the enclosure was unoccupied and a social facilitation control in which the food delivery mechanism was non-functional. Whether subjects were familiar with the helpful and unhelpful conspecifics was also varied. In addition, to investigate potential mechanisms underlying reciprocity, we measured subjects salivary oxytocin concentration before and after they experienced the helpful and unhelpful acts. There was no effect of the previous helpfulness or the familiarity of the partner on the number of times subjects pressed the button. However, there was also no effect of the presence of a partner or the operationality of the food delivery mechanism on the number of button presses, indicating that subjects were not pressing the button to provision the partner. Moreover, the experience of the helpful or unhelpful act did not influence subjects' salivary oxytocin concentration. Variation in findings of reciprocity across studies appears to correspond with differing training protocols. Subjects' understanding of the task in the current study may have been constrained by the limited training received. Additional tests to verify subjects' understanding of such tasks are warranted in future studies.

Environments contain various forms of noise that can interfere with the ability of animal sensory systems to perceive information. One ubiquitous type of visual noise in shallow aquatic habitats is caustic flicker (or caustics), consisting of dynamically moving light patterns caused by the refraction of light when passing through the water's rippling surface. While some teleost fish avoid environments with caustic noise (where their prey can be more difficult to detect), it remains untested whether caustics affect the habitat selection of invertebrates. In the present study, we ask whether three invertebrate species, the shore crab Carcinus maenas, the brown shrimp Crangon crangon, and the common cuttlefish Sepia officinalis, prefer or avoid associating with environments with caustic noise, and whether caustics affect their behavioural activity and habitat exploration. To do this, we exposed the three species in binary choice experiments to different simulated caustic noise levels varying in their temporal (speed) and spatial (definition) components. Neither of the three tested invertebrate species spent more or less time in environments with higher caustic noise levels. While we also found no evidence that caustics affected the behavioural activity and exploration of Ca. maenas and S. officinalis, the brown shrimp Cr. crangon reduced its activity with increasing spatial caustic noise. However, all obtained effect sizes in this study were small, suggesting that caustic noise only minimally affects invertebrate behaviour. Overall, our results show that, unlike in teleost fish, caustics have limited influence on the habitat selection, exploration, and activity of crustaceans and cephalopods.

Environmental enrichment (EE) often increases positive behavioral and physiological effects on captive animals. Fish are commercially and scientifically important taxa that have been shown to benefit from EE. Here we examined the effects of both short- and long-term EE in Trinidadian guppies (Poecilia reticulata). In the short-term exposure to EE, female guppies were raised in standard conditions, and after reaching adulthood were moved to either an enriched or a deprived environment for 2 weeks. Long-term exposure guppies were reared from birth for 12 weeks (until sexual maturity) in either an enriched or deprived environment. We then assessed growth, brain size, and neophobic and exploratory behaviors in standard assays. Guppies given EE were bolder, regardless of timescale, although females showed a more pronounced change in behaviors than males. We further found that guppies reared with EE were smaller yet had larger relative brain sizes than guppies reared under deprived conditions. Here we highlight that EE had influenced growth, brain size, neophobic, and exploratory behaviors in guppies, and behavioral changes were observed after only 2 weeks. Our results highlight the need for assessing the influences of EE in captivity, in particular for researchers studying cognition and behavior.

Many plants exploit the ability of animals to move in order to disperse their pollen and seeds. Despite the growing understanding of the role animals play in the reproductive lives of plants, there are few examples of amphibians contributing to these processes. We report on an Australian tree frog, Litoria fallax, interacting with and likely moving seeds of the broad-leaved cumbungi, Typha orientalis, over short distances via external transport. Field observations revealed both juvenile and adult L. fallax individuals carrying typha seeds, which were adhered to the skin on the feet, legs, belly and dorsum. Approximately 30% of observed frogs were found to be carrying 1–14 seeds at a time. The small size and specialised fibre tufts of typha seeds, which enable them to be primarily dispersed by wind, also make them susceptible to being unintentionally picked up and transported by L. fallax as they move through aquatic environments. The moist surfaces of frogs, coupled with their presence in freshwater systems that can be dominated by typha, create favourable conditions for seed attachment. These findings highlight a previously unknown interaction between an amphibian and a plant that enables seed dispersal, supporting the need for further exploration into unexpected plant vectors.

Reciprocity and pseudo-reciprocity are two important models for the evolution of cooperation and often considered alternative hypotheses. Reciprocity is typically defined as a scenario where help given causes help received: cooperation is stabilized because each actor's cooperative investments are conditional on the cooperative returns from the receiver. Pseudo-reciprocity is a scenario where help enables byproduct returns: cooperation is inherently stable because the actor's cooperative investments yield byproduct returns from the receiver's self-serving behavior. These models are strict alternatives only if reciprocity is defined by the restrictive assumption of zero fitness interdependence, meaning that the helper has no “stake” in the receiver's fitness. Reciprocity and interdependence are, however, not mutually exclusive when helping can increase both reciprocal help and byproduct returns. For instance, helping partners survive can simultaneously increase their willingness to reciprocate, their ability to reciprocate, and byproduct benefits of their existence. Interdependence can “pave the road” to reciprocal helping, and partners who reciprocate help can also become interdependent. However, larger cooperative investments can increase the need for responsiveness to partner returns. Therefore, most long-term cooperative relationships involve both responsiveness and interdependence. Categorizing these relationships as “reciprocity” can be viewed as ignoring interdependence, but calling them ‘pseudo-reciprocity’ is confusing because stability also comes from the cooperative investments being conditional on returns. Rather than conceptualizing cooperation into discrete categories, it is more insightful to imagine a coordinate system with responsiveness and interdependence as continuous dimensions. One can ask: To what degree is helping behavior responsive to the partner's behavior? And to what degree does the helper inherently benefit from the receiver's survival or reproduction? The amounts of responsiveness and interdependence will often be hard to estimate, but both are unlikely to be zero. Identifying their relative importance, and how that changes over time, would greatly clarify the nature of cooperative relationships.

Cooperative behaviours, which benefit a recipient, are widespread in the animal kingdom; yet their evolution is not straightforward. Reciprocity, i.e., cooperating with previously experienced cooperative partners, has been suggested to underly cooperation, but has been contested throughout the years. Once a textbook example of reciprocity was cooperative predator inspection, where one or several individuals leave their group to approach a potential threat. Each can at any point stop or retreat, increasing the risk for its partner. It was suggested that inspecting individuals follow a specific reciprocal strategy called tit-for-tat, i.e., cooperating on the first move and then copying the partner's last move. Numerous studies provide evidence to support the claim that fish cooperate to inspect predators, including three-spined sticklebacks (Gasterosteus aculeatus), guppies (Poecilia reticulata) and minnows (Phoxinus phoxinus). However, over the past few decades some scholars have expressed scepticism whether predator inspection is indeed a cooperative behaviour or rather a case of by-product mutualism, which describes behaviours that benefit a partner as a corollary of an otherwise selfish behaviour. For instance, it has been shown that pairs of fish moving in unfamiliar environments appear to coordinate movements even in the absence of predators. Many studies have also used coarse measures of overall approach rates towards predators rather than the fine-grained analyses necessary to infer tit-for-tat in cooperative inspections. Now is the time to return to the question of cooperative predator inspection with new tools and approaches to resolve a decades-old debate.

Chimpanzees (Pan troglodytes) and humans cooperate in reciprocal patterns, but it is unclear whether these interactions are based on the same psychological foundations. While there is evidence suggesting that both species engage in long-term forms of reciprocity, there is very little work exploring their short-term behavioural contingencies with suitable methods. Here, we present a direct comparative study on short-term reciprocity in chimpanzees and human children using a novel, low-cost instrumental helping task. We investigated whether participants help a conspecific partner to obtain a tool for accessing a reward, and whether the level of helping depends on the partner's previous helpful or unhelpful behaviour. In line with prior research, both chimpanzees and children demonstrated helping behaviour towards their partner. However, the extent to which the two species showed short-term reciprocity differed considerably. After receiving help, tested children always helped in return. They helped substantially less when interacting with an unhelpful partner. Chimpanzees showed a higher tendency to help when interacting with a helpful compared to an unhelpful partner only in the first half the experiment. With increasing trial number, chimpanzees stopped discriminating between helpful and unhelpful partners. This study provides evidence for short-term reciprocity in human children and, to a lesser extent, in our closest living relatives. Our findings demonstrate that helping paradigms provide a useful context to investigate reciprocal motives in humans and chimpanzees alike.

Bumblebees are important pollinators in both natural and agricultural ecosystems, but their survival and pollination service are threatened by extensive pesticide use. Due to regulation changes, acetamiprid has become the only neonicotinoid substance that can be used without restrictions and in open-field cultivations in the European Union. Yet, we know little about how this active ingredient affects bumblebees' foraging behaviour and if such effects are similarly detrimental to those of other neonicotinoids. Here we investigated how a 14-day-long (chronic) exposure to low (5 ppb) and high (2500 ppb) concentrations of acetamiprid in syrup affected different aspects of foraging behaviour in buff-tailed bumblebees (Bombus terrestris, Linnaeus). We recorded individual foraging at artificial food patches during one-hour-long trials and then compared several foraging-related measures between differently dosed individuals. We found that 75.12% of the total syrup consumption occurred at the first-exploited patch, but individuals did not exhibit any bias toward pesticide-treated food patches. Chronic exposure to acetamiprid had little effect on individual foraging decisions at the first-exploited food patch but significantly affected the time to the first feeding and the number of feedings at the second-exploited patch in interaction with body mass. The duration of the first feeding was affected only by foragers' body mass. Our finding indicates that chronic exposure to a high but field-realistic concentration of acetamiprid may alter some aspects of bumblebees' foraging behaviour. If such behavioural changes accumulate during consecutive foraging bouts, chronic exposure to this pesticide might lead to a reduction of daily resource collection, ultimately jeopardising colony fitness or plant (crop) pollination.

As the females of most mosquitoes require a blood meal to provision their eggs, they can be a vector of parasites and pathogens that have profound impacts on both animal and human populations. Understanding the interactions between mosquitoes and their hosts, including animal and feeding site preferences, could thus provide valuable insights into disease transmission. In this study, we present a highly specific feeding strategy observed in a mosquito from Australia (Mimomyia elegans). Over 3 years of fieldwork, we found this mosquito feeding exclusively on the nostrils when using several amphibian species as hosts. Mosquitoes were observed initially landing on the backs of hosts before walking towards the nostrils, potentially minimizing detection and mitigating the risk of predation or defensive responses. This remarkable level of feeding site specificity suggests strong selection pressures that are causing the nostril to be the optimal location for blood extraction on amphibians. Possible explanations include the presence of thinner, more accessible skin tissue or enhanced vascular properties in the nostril region. Understanding mosquito host preferences, points of contact and feeding site specificity could provide valuable insights into disease transmission among amphibians, as mosquitoes have been identified as potential vectors of pathogens like the amphibian chytrid fungus.

Dogs interpret cues as being about location, which human infants would relate to objects. This spatial bias could shed light on the evolution of object-centered thought, however, research needs to rule out that this is not a by-product of dogs' weaker (compared to humans) visual capacities. In this study, we used a data set in which dogs were tested in two types of learning tasks (discrimination and reversal learning) with two types of rewarded cues (location and object features). In both tasks, dogs displayed spatial bias, that is, faster learning when the rewarded cue was a location. We investigated how sensory and cognitive capacity each contributes to this spatial bias. To this end, an estimate for general cognitive ability (g) was obtained from a battery of tests for some of the dogs. Cephalic index, a feature targeted in breeding and linked to differences in visual capacity, correlated negatively with the expression of spatial bias only in the easier discrimination learning task, while a negative correlation between g factor and spatial bias scores emerged in the more difficult reversal learning task. We conclude that dogs' spatial bias cannot be reduced to a sensory limitation and is easier to overcome with greater cognitive capacity.