Volume 33, Issue 3, May/June 2022

The study of animal personality has focused on five main traits: exploration, boldness, activity, aggression, and sociality, but it is unclear whether animals display personality across additional behavioral domains. We investigated the generality of personality across spatial behaviors such as home-ranging, movement through space, and habitat use. We demonstrated that individuals consistently differed in these behaviors across taxa. The existence of spatial personality may influence wildlife distribution, abundance, interactions, and fitness, and thus effect the capacity for populations to adapt to environmental change.

Spotless starling nestlings colour their mouths with a yellow secretion that reflects their oxidative status, which in turn influences parental feeding behaviour. We directly observed the cosmetic use of uropigial secretion by nestlings and experimentally demonstrated a link between antioxidants and secretion colour. Moreover, because siblings reared in different starling nests showed similar secretion colour, and because parents prefer to feed nestlings with particular colourations, our results strongly suggest a role of uropygial secretion in parent–offspring communication.

We found that helping decisions in wild sociable weavers are influenced by the individuals’ physiological condition, age and cost of flight, and that individuals decreased their helping behaviour to minimise the associated costs. These results suggest a trade-off between cooperation and self-maintenance, which is important to understand when helping might take place in this and other species.

Many animals have the ability to lose and regenerate body parts. Interestingly, most of those animals are relatively primitive such as worms, jellyfish, crabs, and starfish; derived animals like birds and mammals are incapable of losing and regenerating appendages. Why would evolution favor the loss of such a seemingly beneficial trait? Our research hints at the intriguing possibility that birds and mammals may have traded their relatively elaborate reproduction for their ability to regrow body parts.

Social networks of common waxbills appear more strongly shaped by associations with familiar individuals than by phenotypes. Familiarity was the main predictor of long-term associations among wild-caught waxbills over two years in a large mesocosm, but waxbills also preferred opposite-sex associations during breeding seasons and, in non-breeding seasons, assorted according to dominance rank. Results show that social structure in gregarious animals can depend more on long-lasting familiarity than on phenotypic differences among individuals.

If sexual selection is such a powerful force in nature, why are the sexes strikingly similar in some of the bovid species where the competition for mates is believed to be most intense? This study finds that although sexual dimorphism in coloration and pelage appendages generally characterizes species where the potential for males to monopolize females is high, such dimorphism is less common in species where the sexes tend to form mixed-sex groups outside the breeding season. We propose that a predation cost from divergent appearance of the sexes may be higher in taxa that form mixed-sex groups.

What information do social groups use in colony-wide warfare? We tested if, at the collective level, ant colonies use information about an opposing colony’s demographics during contests over brood. We used the number of workers as a measure of colony fighting ability and the number of brood as a measure of colony resource value. We found that colonies use information about both the opposing colony’s fighting ability and their own brood to make contest decisions.

Social information gathered by observing others may often be highly beneficial in harsh environments. We conducted playback experiments to assess the use of social information for locating conspecifics in wild zebra finches. Zebra finches were more likely to land when vocalizations from foraging zebra finches were broadcast compared to white noise. Use of such social information may enhance foraging efficiency in environments with scarce foraging locations and may reduce predation risk.

Highly successful invasive brown widow spiders avoid egg sac parasitism. We found that parasitoids prefer native widow spider egg sacs compared to those of the invasive brown widow spider. More and larger wasps emerged from the native widow egg sacs, indicating that the species is a better host for the wasp. The lower suitability of brown widow egg sacs for the wasp parasitoid may explain the rapid invasive spread of brown widow spiders worldwide.

Despite numerous studies comparing behavioral flexibility between populations from rural and urban habitats, we still don't understand the relationship between level of urbanization and flexibility. We suggest that the problem stems from ignoring the heterogeneity within urban habitats. In this empirical study we show that urban change (i.e., the change in urbanization level over time) better explains behavioral flexibility and other related behaviors in house sparrows than the level of urbanization.

Before you eat someone, you have to attack them first. Here, we investigated the factors that shape aggression in the cannibalistic tadpoles of the dyeing poison frog. We find that aggression depends on both size and relatedness: when set in pairs, large tadpoles are half as aggressive towards their smaller siblings than to nonsibs. It looks like belonging to the same family provides some protection against aggression, though no one is ever truly safe.

Birds may return to the same breeding site to reunite with their old partner. For migratory bird species, whether to return to the same site as last year to breed or disperse to a new site depends on their mating system. Among 49 species of shorebirds from around the globe, species that form an exclusive breeding pair returned to the previous breeding site more than species where one sex mates with multiple partners.

The benefits of group living drive social evolution, but these could vary over time and not be evident at all times that group size is measured. We found that important benefits of group size in a primitively social bee are only apparent late in the reproductive season when group size has dwindled and colonies may not even seem to be social. Understanding social evolution requires a whole-of-life viewpoint, and “snapshot” samples may not capture this.

Many animals dig nests to provide good conditions for their progeny. Nevertheless, the distinction between the importance of the choice of habitat compared with the characteristics of the modifications made during nest building is little considered. Using the sea lamprey as a study case, it appears that both choice and modification should be considered but that habitat modification had a greater impact on keeping eggs in the nest.

In nature, selection often favors animals that have specific responses to predation encounters. However, unintuitively, sometimes selection can favor a lack of behavioral response when predators are abundant in their environment. We demonstrated that behavioral strategies of threespine stickleback populations experiencing predation from an invasive predator, northern pike, vary considerably in their behavioral responses, and that evolution in response to predation may be highly variable even within a species.

Decisions predators make while foraging affect their feeding efficiency, which also affects these decisions in return. To better understand these intricate relationships, we studied the impacts of feeding success on foraging behaviors of two species of fur seals. Seals responded to a decrease in capture success by adjusting both their movement and diving patterns, although in different ways depending on their habitat and targeted prey. Our study provides insight into seals might respond to changes in prey availability.

Ant nests are extended phenotypes, resulting from the behavior of the ants. Factors both internal and external to the ants can influence the structure of their nest. By comparing nests constructed by ants from different colonies and species under different environments, we found that internal factors contribute more strongly than external factors to the extended phenotype.

In social animals, reproductive maturation can be accelerated by nutritional advantages or the arrival of suitable mates. In geladas, the immigration of unrelated males prompts female maturation. Here, we report that—above and beyond this male effect—female geladas mature earlier if their mothers are high-ranking, which likely improves access to high-quality foods, and if they live in large groups, which experience higher rates of infant mortality and more frequent exposure to loitering, unrelated males.