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In socially monogamous titi monkeys, involuntary separation from a pair mate can produce behavioral distress and increased cortisol production. The neuropeptide oxytocin (OXT) is thought to play an important role in the separation response of pair-bonded species. Previous studies from our lab have shown that chronic intranasal oxytocin (IN OXT) during development can have long-term effects on adult social behavior. In the current study, we examined the chronic and acute effects of IN OXT or Saline (SAL) on the subjects’ response to a brief separation from their pair mates. Subjects with a history of chronic IN OXT or SAL treatment during development received a single dose of OXT or SAL as adults 30 min before being separated from their pair mate. Chronic treatment consisted of a daily dose of IN OXT (0.8 IU/kg) or SAL (control) from 12 to 18 months of age. Subjects (N = 29) were introduced to a pair mate at 30 months of age. After the pairs had cohabitated for 5 months, pairs underwent two “Brief Separation” (OXT and SAL) and two “Non-Separation” (OXT and SAL) test sessions. Vocalizations and locomotion were measured as behavioral indices of agitation or distress during the Brief Separation and Non-Separation periods (30 min each). We collected blood samples after the Brief Separation and Non-Separation periods to measure cortisol levels. Our results showed subjects treated with chronic OXT had a reduction in long call and peep vocalizations compared to subjects treated with chronic SAL. Subjects treated with chronic SAL and acute OXT produced more peeps and long calls compared to animals treated with acute SAL; however, patterns in this response depended on sex. Cortisol and locomotion were significantly higher during the Brief Separation period compared to the Non-Separation period; however, we did not find any treatment or sex effects. We conclude that chronic IN OXT given during development blunts the separation response, while acute OXT in chronic SAL subjects had sexually dimorphic effects, which could reflect increased partner seeking behaviors in males and increased anxiety in females.

Socially monogamous prairie voles (Microtus ochrogaster) display remarkable individual variation in social behaviors, which has been associated with differences in early life experience and neuropeptide receptor densities. These differences are also seen in the wild, where approximately 70% of young voles remain in their natal group as non-breeding alloparents, while the other 30% disperse. We investigated whether natural variation in early parental care could contribute to offspring’s willingness to “disperse” (willingness to explore) in a laboratory context. Behavioral differences between dispersers and residents could also provide a way to interpret individual variation in other behaviors commonly observed under laboratory conditions. Breeder pairs ranked as high, medium or low-contact, according to the amount of early parental care they provided to offspring, were used to produce and rear experimental subjects. Effects of early parental care on the offspring’s willingness to disperse were seen at post-natal day 21, with high-contact offspring spending more time in the start cage and low-contact offspring spending more time exploring. Variations in parental care were also associated with differences in juvenile and adult behaviors that could potentially encourage philopatry or dispersal behavior in the wild. High-contact offspring displayed less anxiety-like behavior compared to low-contact animals. Low-contact offspring displayed the lowest amount of alloparental care. High-contact offspring spent more time in side-by-side contact with a potential partner compared to medium and low-contact offspring. These results suggest that variations in early parental care can impact weanlings’ exploratory behavior, but that philopatry is not driven by high anxiety.

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