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1. Intranasal oxytocin drives coordinated social approach

   https://doi.org/10.1038/s41598-021-97468-0  

   Monari, Patrick K. ; Rieger, Nathaniel S. ; Schefelker, Juliette ; Marler, Catherine A. ( December 2021 , Scientific Reports)

   null (Ed.)

   Abstract Coordinated responses to challenge are essential to survival for bonded monogamous animals and may depend on behavioral compatibility. Oxytocin (OT) context-dependently regulates social affiliation and vocal communication, but its role in pair members’ decision to jointly respond to challenge is unclear. To test for OT effects, California mouse females received an intranasal dose of OT (IN-OT) or saline after bonding with males either matched or mismatched in their approach response to an aggressive vocal challenge. Pair mates were re-tested jointly for approach response, time spent together, and vocalizations. Females and males converged in their approach after pairing, but mismatched pairs with females given a single dose of IN-OT displayed a greater convergence that resulted from behavioral changes by both pair members. Unpaired females given IN-OT did not change their approach, indicating a social partner was necessary for effects to emerge. Moreover, IN-OT increased time spent approaching together, suggesting behavioral coordination beyond a further increase in bonding. This OT-induced increase in joint approach was associated with a decrease in the proportion of sustained vocalizations, a type of vocalization that can be associated with intra-pair conflict. Our results expand OT’s effects on behavioral coordination and underscore the importance of emergent social context. 

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2. Pair-bonding leads to convergence in approach behavior to conspecific vocalizations in California mice (Peromyscus californicus)

   https://doi.org/10.1371/journal.pone.0255295  

   Rieger, Nathaniel S. ; Monari, Patrick K. ; Hartfield, Kamryn ; Schefelker, Juliette ; Marler, Catherine A. ( August 2021 , PLOS ONE)

   Rosenfeld, Cheryl S. (Ed.)

   Pair-bonding allows for division of labor across behavioral tasks such as protecting a territory, caring for pups or foraging for food. However, how these labor divisions are determined, whether they are simply intrinsic differences in the individual’s behavior or a coordinated behavioral response by the pair, remains unknown. We used the monogamous, biparental and territorial California mouse ( Peromyscus californicus ) to study how behavioral approach to an aggressive vocal stimulus in a novel environment was affected by pair-bonding. Using a three-chambered vocal playback paradigm, we first measured the amount of time individuals spent in close proximity to aggressive bark vocalizations. We found that animals could be categorized as either approachers or avoiders. We then paired individuals based on their initial approach behavior to an opposite sex individual who displayed either similar or different approach behaviors. These pairs were then retested for approach behavior as a dyad 10–11 days post-pairing. This test found that pairs showed convergence in their behavioral responses, such that pairs who were mismatched in their approach behaviors became more similar, and pairs that were matched remained so. Finally, we analyzed the ultrasonic vocalizations (USV) produced and found that pairs produced significantly more USVs than individuals. Importantly, increased USV production correlated with increasing behavioral convergence of pairs. Taken together, this study shows that pair-bonded animals alter their approach behaviors to coordinate their response with their partner and that vocal communication may play a role in coordinating these behavioral responses. Overall, our findings indicate that pair-bonding generates an emergent property in pairs, adjusting their combined approach behavior towards a new aggressive stimulus representing a potential challenge to the bonded pair. Such findings may be broadly important for social bonding in other social systems. 

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3. Responses of a pair‐living, sexually monogamous primate to the simulated presence of solitary individuals: A field playback experiment

   https://doi.org/10.1111/eth.13222  

   Garcia de la Chica, Alba ; Wood, David Bechtel ; Rotundo, Marcelo ; Fernandez‐Duque, Eduardo ; Goymann, ed., Wolfgang ( August 2021 , Ethology)

   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.

    

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4. What about Females? Urban Female Song Sparrows Elevate Aggressive Signaling Compared to Rural

   https://doi.org/10.1093/icb/icac106  

   Lane, Samuel J. ; Sewall, Kendra B. ( July 2022 , Integrative And Comparative Biology)

   The costs and benefits of breeding behaviors are influenced by environmental conditions, and habitat variation can shift the degree to which behaviors are expressed. Novel urban habitats have been shown to differ significantly in disturbances such as noise, light at night, and human presence, as well as resource availability, compared to rural habitats. Perhaps because of these environmental differences, urban males of several species are consistently more aggressive than rural males, raising the hypothesis that greater territorial aggression is beneficial in urban habitats. Though often ignored, female songbirds of many species also perform aggressive territorial behaviors toward conspecifics during the breeding season. For socially monogamous songbirds, this aggression functions to ensure partner fidelity and secure resources for reproduction. Studies of the effects of urbanization on songbird behavior have yet to determine if urban females also express greater territorial aggression. Importantly, energetically demanding behaviors such as territoriality and parental care should constrain one another, leading to behavioral trade-offs during the breeding season. Though territorial aggression and parental care are inversely related in males of several species of songbird, this relationship is understudied in female songbirds, particularly those facing environmental change, such as urbanization. In this study, we compared aggressive signaling and a measure of parental care (maternal nest visitation rates) between female song sparrows (Melospiza melodia), living in urban and rural habitats. We hypothesized that female aggressive signaling would be higher in urban environments compared to rural, and negatively correlated with maternal visitation rates. We found that urban females, like males, expressed increased aggressive signaling compared to rural. However, female aggressive signaling was not related to our measure of maternal care, suggesting females aren't facing a trade-off between these two behaviors. Collectively, our results are consistent with the hypothesis that urban habitats promote territorial aggression in female song sparrows. As urbanization continues to spread, understanding the behavioral changes animals employ in urban environments requires studying individuals of different sexes and age classes, and will help us understand how some species are able to cope with human-induced rapid environmental change.

    

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5. Simulated infection alters the behavior of pair bonded songbirds and their healthy neighbors

   https://doi.org/10.1093/beheco/arac120  

   Love, Ashley C. ; Anthony, Anna C. ; Nash, Aimee ; Campos-Melara, Angel ; Kodali, Jahnavi ; DuRant, Sarah E. ; Ridley, ed., Amanda ( February 2023 , Behavioral Ecology)

   While infection and perceived infection risk can influence social and reproductive behavior in several taxa, relatively little is known about how infection specifically affects pair bond behaviors. Some pair bond maintenance behaviors may be costly to maintain during infection, and infection could promote avoidance behaviors within an established pair. Many species exhibiting pair bonds are part of larger social groups, and behavioral shifts in established pairs can result in altered extra-pair contact rates that could also shape disease transmission. Using captive zebra finches (Taeniopygia guttata), we examined how an immune challenge with lipopolysaccharide (LPS) influences activity, social behavior, and pair bond maintenance behaviors in established pairs and their healthy neighbors. We observed shifts in individual and pair maintenance behaviors in both immune-challenged pairs and healthy pairs exposed to a social cue of infection (sick conspecifics). Specifically, LPS-challenged birds decreased activity and social interaction attempts relative to control birds, consistent with LPS-induced sickness behavior. LPS-challenged birds also increased the frequency of clumping (perching together in bodily contact) between individuals within a pair. Healthy birds exposed to immune-challenged conspecifics decreased flight activity and increased self-preening, behaviors which could function to limit infection risk. Exploring how both infection and the perceived risk of infection shape behaviors within and among paired individuals will increase our understanding of the role of social behaviors in shaping disease dynamics.

    

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