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Abstract Loud calls play an important function in regulating the use of space and structuring social groups and mating systems in a wide range of taxa. In pair‐living territorial animals, where encounters with neighbors and solitary conspecifics are common, these calls are mainly associated with resource defense or mate guarding behaviors. Owl monkeys (Aotus azarae) live in groups of one pair of reproducing adults and 1–4 younger, non‐reproducing individuals. Both sexes disperse when they are around 3 years of age; they become solitary floaters who compete to replace same‐sex adults from other groups. Here, we examined the behavioral responses of Azara's owl monkey pairs toward calls of unpaired and unfamiliar males and females to better understand if the competition between floaters and groups is in relationship to the defense of their territory, their mates, or both. We collected behavioral data from six groups, before, during, and after the playing back of unfamiliar male and female loud calls and of a control stimulus at the center and border of their home ranges. Overall, our results showed that the playback location did not elicit differential responses in the monkeys and that both sexes were more reactive to male than female unfamiliar calls, as evidenced by higher rates of sociosexual and vocal responses, movement toward the playback, and intergroup encounters during and after the experiments. Our study indicates that paired male and female owl monkeys mainly defend their partners toward intruders and emphasizes the need of including the role of sexual competition on both sexes in models about the evolution of pair‐living social organizations and sexual monogamy mating systems. 

Abstract It is well known that fishing is size‐selective, but harvest may also inadvertently target certain behavioral types or personalities. Changes in the abundance of behavioral types within a population have implications for fisheries management, including affecting catch rates, individual growth, and food web dynamics. Using streamside behavioral assays, we quantified the repeatability of behaviors in a population of Baikal grayling (Thymallus baicalensis) in northern Mongolia, a popular sport fish and important local predator. We assessed whether different angling techniques (i.e., fly or spinning gear) collected different behavioral types and whether variation in behavior was associated with body condition or diet (i.e., using stable isotope analysis). Surprisingly, we found no evidence for consistent individual differences in several behaviors within this population. Furthermore, differences in mean behaviors were not predicted by angling gear, body condition, or carbon and nitrogen isotopic signatures. We suggest that since this is a fished population, the range of behavioral variability in the population may have been reduced through previous behaviorally selective harvest. This might explain both the lack of difference in mean behaviors between fish caught by both gear types and the lack of evidence for consistent individual differences in behavior within the sampled population. 

Abstract Temperature influences the expression of a wide range of behavioral traits in ectotherms, including many involved in the initiation of pair formation and mating. Although opportunities to mate are thought to be greatest when male and female activity overlap, sex‐specific behaviors and physiology could result in mismatched thermal optima for male and female courtship. Here, we investigate how conflicts in the thermal sensitivity of male and female courtship activity affect patterns of mating across temperatures inEnchenopa binotatatreehoppers (Hemiptera: Membracidae). These plant‐feeding insects coordinate mating with plant‐borne vibrational signals exchanged in male–female duets prior to pair formation. We manipulated temperature across an ecologically relevant range (18–36ºC) and tested the likelihood of individual male and femaleE. binotatato engage in courtship activity using vibrational playbacks. We then staged male–female mating interactions across the same temperature range and quantified the thermal sensitivity of mating‐related behaviors across stages of mating. Specifically, we measured the timing of duetting, the likelihood for key pre‐copulatory behaviors to occur, whether the pair mated, and copulation duration. We found sex‐specific thermal sensitivity in courtship activity: Males showed a clear peak of activity at intermediate temperatures (27–30ºC), while females showed highest activity at the hotter thermal extreme. Mating rates, courtship duets, and copulatory attempts were less likely to occur at thermal extremes. Also, duetting occurred earlier and copulation was shortest at higher temperatures. Overall, our data suggest that sexes differ in how temperature affects mating‐related activity and some processes involved in mate coordination may be more sensitive than others across variable thermal environments. 

Abstract Brown‐headed cowbirds (Molothrus ater) are generalist obligate brood parasites, laying in the nest of nearly 300 avian species, and successfully parasitizing well over 100 host species. Cowbird eggs are generally considered non‐mimetic, although some have suggested that cowbird eggs resemble several of their host species’ eggs. To date, no investigation has examined the level of avian‐perceived similarity between cowbird and diverse host eggs in the contexts of light characteristics at the nest and the visual system of the relevant viewer. Because the cowbird exploits a wide range of species that lay in a variety of nest types, hosts view these eggs under an array of light conditions which could facilitate or hinder egg discrimination. When considering the visual system of the relevant viewers and the light conditions at their nest, we found that the coloration of cowbird eggs was more similar to host than non‐host species’ eggs. Host responses (whether they accept or reject cowbird eggs) were not statistically different when hosts perceived a large chromatic difference between their own eggs and the cowbird's eggs. Instead, we found that host responses were predicted by the degree to which nesting light conditions facilitated color similarity between host and cowbird eggs, such that hosts typically nesting under light conditions where this color discrimination task was more challenging were more likely to reject cowbird eggs. This suggests that the nesting light environment may have selected for increased coevolved egg recognition abilities in a suite of cowbird host species, even in the absence of parasitic egg color mimicry.