Advance articles

Living in groups has been shown to have antipredator benefits for prey animals but risk still differs for individuals within a group. Using fish as predators presented with simulations of virtual prey, we show that prey on the edge of groups are more likely to be attacked than others, even at relatively small group sizes. We also show that encountering prey on the edge is likely to explain this effect rather than predatory confusion.

Smaller and less generalist Black-Browed albatrosses were more strongly attracted to encountered fishing boats than dominant Wandering albatrosses. Anthropogenic food sources enhance aggregations of large numbers of individuals and species, but are not necessarily exploited by all individuals encountering them, or not to the same extent. We hypothesize that these food sources may especially attract individuals with higher energetic demands and/or fewer alternative foraging options available.

We tested the population-level effects of a dominant competitor—lions—on a subordinate—leopards. Although lions were a common cause of leopard mortality, they did not suppress or displace leopards. Population growth was similar between the 2 species and leopards did not avoid lions. Coexistence was likely possible because lions and leopards targeted different sized prey. Widespread poaching of large ungulates may increase levels of competition between lions and leopards by forcing them to target the same prey.

Whether sea otters use tools to dine depends on what’s for dinner. When calorie-rich food is plentiful, all otters eat the best foods and use tools only if hard-shelled prey like large clams are present. But when the menu includes less-desirable options including small, hard-shelled snails, only some otters eat snails and use tools to crack them. Similar factors may also drive tool use in other animals like crows or dolphins.

Parental care and reproductive success of collared flycatchers were related to own and partner’s sexual ornaments in partial interaction with environmental conditions. In a brood size manipulation experiment, male wing patch size and female plumage brightness correlated with the partner’s feeding rate. Nestling quality correlated with male forehead patch size depending on breeding environment. These findings reveal a complex picture of relationships between the sexual ornament expression of parents and their parental care and success.

Studies of colour-banded zebra finches have provided mixed support for the hypothesis that females paired with attractive males will produce more sons. Variation in female mate preferences could help to explain the conflicting patterns seen in previous studies. In our experiment, females varied in their preferences for males’ colour-bands. Females mated to males of their preference produced male-biased brood sex ratios at fledging, while the specific colour of male colour-bands did not affect offspring sex.

We examined the relationships between the complexity of male genital structures (titillators) and both the mating rate of males and females, and the number of times females mate, across a range of bushcricket species. We did not find any relationship between genital complexity and the number of times females mate. Among species with titillators, however, the complexity of these structures was associated with faster re-mating rates in females. The results therefore only partly support the hypothesis that the structure and complexity of genitalia relate to the intensity of sexual selection.

Animals often have darker coloration on their top surface than on their underside (“countershading”). In terrestrial prey, this patterning eliminates the body’s shadows to facilitate camouflage. In a freshwater fish that can change color, countershading provides optimal camouflage for different visual backgrounds and viewing angles rather than to reduce shadowing. Countershading camouflage may operate differently in terrestrial and aquatic habitats.

Red foxes thrive in towns and cities, where much of their food is deliberately provided by humans. We studied fox foraging behavior using camera traps in residential gardens where householders regularly fed foxes. Predictable feeding patterns attracted foxes to gardens, females were more efficient foragers than males, and dominant foxes enjoyed priority access to food, so that subordinates had to adopt compensatory strategies. Understanding how foxes exploit resources may help address conflicts in urban areas.

Cold and hot lizards advertise territory ownership less than warm lizards because of thermal constraints on physiology. Social communication in cold-blooded animals is often linked to environmental temperature, but why has been unclear. We tested several hypotheses in a study of Caribbean anole lizards. The number of advertisement displays performed by lizards was dependent on temperature in a way that could only be explained by constraints on strenuous activity at cold and hot temperatures.

Dwarf mongooses, the smallest species in the mongoose family, produce a number of diverse alarm-call types, with several being general and 2 indicating predator type. Furthermore, the specificity of their alarm-call types appears higher for aerial than terrestrial threats and, unlike other mongoose species, they seem to use the same alarm-call type for both physically present terrestrial predators and secondary cues of their presence.

This study shows that pathogens and urbanization play only a subtle role in human face preferences in a small-scale society.

Do daily activity rhythms underlie observed variation in seasonal reproductive timing? Laboratory studies have found a link between daily activity rhythms and activation of the reproductive system. However, this relationship remains largely unexplored in the wild. We asked if females with early onset of activity would also breed earlier in the year. We found this to be true in 2 species of songbird, on 2 different continents, thus supporting our hypothesis.

We show that for objects moving in groups, spotting one that is a different shape is harder when the objects are similarly patterned. The difficulty of spotting the odd-one-out is further enhanced by matching the background and being in larger groups. So, even though motion ‘breaks’ camouflage, being camouflaged can help group-living animals reduce the risk of being singled out for attack by predators.

Preening one’s partner is important for staying together and sharing offspring care. Grooming or preening a partner is widespread in primates and birds. We tested the idea that this behavior (allopreening) in birds plays a role in maintaining partner relationships. Bird species that allopreen were more likely to share parental duties and more likely to breed with the same partner in consecutive breeding seasons, compared to species that do not allopreen.

Twitter: @ElspethKenny

How genetic variation is preserved is a central issue in evolutionary biology. In many species of damselflies, females come in distinct heritable color varieties. We found that in an Iberian damselfly when subject to stressful male harassment, fecundity decreased in one kind of female but not in others. Our results, together with previous observations, suggest a scenario where differential fecundity, male preference, and fluctuations in male abundance play an important role in maintaining this variation.

Early environmental conditions can have important long-term consequences for fitness. These carry-over effects often differ among species but the reason for such interspecific variation is not clear. We experimentally manipulated incubation temperatures in 4 sympatric bird species and show that carry-over effects differ among species according to parental care responses.

Novel environments can trick animals into preferring the worst place to live. Artificial night lights simulate their primary navigational beacon (the moon) and when that light reflects off of asphalt it is polarized and makes roads appear as false ponds. Insects evolved to use moonlight to guide their flight, but it can also make false ponds more attractive as nesting sites.

Links between behavioral traits can shift with the local climate. We show that behavioral associations with temperature not only occur across, but also within populations. At warmer sites ant colonies increased their exploration and foraging activity, but were less aggressive. Moreover, at these warmer sites, more positive links were found between behaviors within populations compared to colder sites, where more negative links prevailed. Our study suggests that associations between behaviors shift along climatic gradients.

Behavior of pygmy rabbits varied seasonally to accommodate both thermal challenges and predation risk. We quantified selection of rest sites and activity during summer and winter to evaluate behavioral tradeoffs between thermal and security resources. Our work suggests that behavior might buffer individuals of this species against a changing climate, and it highlights the need for incorporating behavior into models of how individuals and populations of animals respond to climate change.

Measures of stress hormones reveal the challenges faced by socially subordinate meerkats. We studied the causes of variation in stress hormones in group-living wild meerkats. We found that stress hormones in subordinate meerkats were affected by the amount of conflict with socially dominant breeders and also by conflict with other group members, whether they were caring for offspring, and their own body condition. Our study highlights how factors of the social group in addition to those of the individual and ecological environment affect stress levels in highly social animals.

Twitter: @ben_dantzer

Why does the distance that animals disperse between their natal and breeding territory usually differ between males and females? We show that in cooperatively breeding Seychelles warblers males are reluctant to disperse and disperse less far than females. We suggest that this may be because for males, dispersal is more costly due to more aggression from other territorial males.

Twitter: @SjoukeKingma

We investigated geographical variation in multiple traits in the oriental fire-bellied toad and tested whether local adaptation to predators has affected the observed divergence of these traits. Our field surveys and experiments revealed that mainland and island frogs were distinguishable in morphology and behavior, most likely due to marked differences in predation pressure between locations. Our study therefore shows how differential predation pressure can affect the geographical divergence of multiple traits.

The factors that limit sexual signal expression and ensure honest signaling of mate quality are poorly known. We show that predation risk is a cost of the sexually selected red coloration of the threespine stickleback and, hence, could contribute to signal honesty. A common predator selectively preys on colorful stickleback males in the field, and an experimental study showed that the bright coloration attracts the predator independent of the behavior of the male.

The role of sexual selection in driving speciation is supported by correlative links between various traits under sexual selection and speciation. However, there is little evidence on the candidate genes involved in mate choice enabling speciation. Experiments on stickleback mate choice highlight the polymorphic immunogenes of the Major Histocompatibility Complex (MHC) as a true “magic trait”: the MHC drives both habitat-specific assortative mate choice and local adaptation—ultimately speciation.

Individual discrimination can influence social behaviors. Here, we show that superb fairy-wrens (Malurus cyaneus), a cooperative bird species, have individually distinct mobbing alarm calls and that receivers discriminated between 2 unfamiliar individuals using mobbing alarm calls alone. Superb fairy-wrens also responded differently to playback of calls from their mate and kin versus individuals from another population.

Family living is a fundamental characteristic of many organisms social life. Family living is maintained when conditions reduce conflicts between family members. Specifically, low levels of female multiple mating (which increases relatedness between family members) and high resource availability should lead to decreased family conflicts and increase family harmony. We tested this using a subsocial beetle. We show that family conflicts, measured via competitive offspring begging, are decreased when resource availability is high. In contrast, female polyandry had no effect on the level of family conflict.

Bird songs are frequently used by males in territory defense. We show that hihi learn to match their song repertoire to their territory neighbors. Such flexibility in vocalizations is likely to have evolved as a result of the extreme levels of male competition in this species.

Returning to previously used areas (site fidelity) or place of birth (philopatry) are important behavioral adaptations in many species, with known fitness benefits. The combined population level consequences of site fidelity and philopatry, however, have received little attention. Based on GPS location data and mitochondrial DNA we demonstrate how high levels of fidelity and philopatric behavior in the matrilineage of black-tailed deer can lead to fine-scale population structure and discuss possible implications for population dynamics.

Learning enables generalists to forage efficiently from diverse floral resources. Bees must collect nectar and pollen, but effective, flexible foraging behavior has been demonstrated only for nectar foragers. We demonstrate that flexible and effective pollen collection by bees is regulated by 2 ubiquitous floral cues. This mechanism of foraging flexibility likely facilitated the evolution of pollen concealment via poricidal floral morphology. We conclude that effective flexibility in pollen collection can occur without necessitating learning.

We still understand poorly why different groups of individuals within a given species differ in their mating behaviour. We investigated how the composition in size and behavioural tendencies of individuals in a group affected mating behaviour in water striders. In groups where striders were active, bigger, and more flexible, a single male guarded multiple females. In contrast, in groups where striders were inactive, smaller, and exhibited a more rigid behaviour, individuals mated with several partners.

Twitter: @POMontiglio

We studied the effects of energy sector and ocean surf sounds on male song performance, an important attribute in assessing their quality. We found that both ocean and human-generated sounds are linked to reduced song performance. Our results demonstrate that natural sounds can influence avian vocal behaviour in ways similar to human-made sounds and, despite having song characteristics that may be heard better in loud areas, the quality of the signal may be compromised.

Personality is a fundamental component of the individual although atypically considered during conservation efforts. For tortoises about to be released into the wild, we quantified personality prior to release and related it to survival and behaviour in their new environments. We show that personality can be used to predict both survival and ability to engage in beneficial behaviours after release. Personality and behaviour may provide meaningful guidance to conservation practitioners.

Extravagant seasonal male ornaments are assumed to be sexually attractive. Fairy-wrens are a well-known example, where females cheat on their mates by copulating with attractive males that produce ornamental plumage early in the year. Purple-crowned fairy-wrens lack this extreme infidelity, but males do produce a conspicuous breeding plumage at highly variable times. However, this does not appear to bring any fitness benefits or costs, and the stunning purple crown might disappear over (evolutionary) time.

Twitter: @colourfulmarie

Ungulate mothers should provide more maternal care when resources are plenty. Few studies quantify individual differences in resource use, instead using population-level metrics such as between-year variation in environmental conditions. We found that care provisioning by female Soay sheep was similar, regardless of their home range quality. This may be because summer resource levels are high, and demonstrates the need to accurately characterize the environment experienced by individual animals.

Twitter: @ce_regan

Here, we show that one species of leaf-footed bug can self-amputate an injured limb to reduce the cost of injury. Other benefits of self-amputation include escaping predation and escaping entrapment. By identifying different benefits of this behavior, we stand to gain a more comprehensive understanding of how such an extreme trait evolves.

The capacity of animals to alter their foraging strategy is essential to cope with changing environmental conditions and survive at high population densities. White-tailed deer used different foraging tactics between mild and harsh winters. As winter severity increased, deer decreased their exposure to cold temperature, and traded-off the costs associated with locomotion in deep snow cover with the benefits of forage acquisition. Ultimately, they selected different foraging areas between harsh and mild winters.

When offered a choice of experimental foods high in protein, lipid or carbohydrate, urban Australian white ibis showed a preference for high-carbohydrate foods. This is in contrast to the typical composition of their natural prey, which are low in carbohydrates and higher in protein and lipids. Furthermore, the proportion of macronutrients selected by ibis was affected by competition and previous rainfall, giving further insight into the complexities of a native species foraging in urban environments.

Twitter: @SeanCoogs

Contrary to the view that social dominance is a wolf feature that was lost by dogs during domestication, we found that Italian free-ranging dogs live in packs with a stable membership and with a clear hierarchical social structure. Moreover, as in wolves and other cooperative animals in which group members rely on the guidance of experienced companions, high social status in dogs was mainly held by elders, and agonistic interactions were highly ritualized.

In response to competition, males should invest in premating traits (i.e., courtship) to enhance their mating success or in postmating traits (i.e., sperm) to increase fertilization success. We show instead that in the presence of a rival, spiders courting females with food gifts reduce both, investment in gifts and sperm. In competitive environments, accessing more females through low-quality gifts rather than allocating large amounts of sperm to each mating may confer highest fitness rewards.

Research of causes and consequences of animal personality promises exciting insights, yet widely used tests can lead to spurious results: when predictions of individual-level random effects are used in secondary analyses, their error is not carried forward, leading to increased likelihood of ‘false positive’ errors. We demonstrate how alternative approaches enable behavioural ecologists to test hypotheses about the causes and consequences of individual behavioural variation while accounting for the uncertainty inherent in the random effects.

Behavioral flexibility is measured using a plethora of non-equivalent tasks. In experimental psychology, tests include reversal learning, set-shifting and self-control tasks. In addition to the latter tasks, behavioral ecologists have measured behavioral flexibility with tasks that include problem-solving and personality tests. A relationship between behavioral flexibility assessments, especially in behavioral ecology, still needs to be demonstrated. We argue that using a single umbrella term that incorporates too many unrelated traits should be avoided.