Riley Barrington and Dee Higley, Psychology
This research project originally started out with the purpose of correlating aggression rates in rhesus macaque monkeys with the level and type of oxytocin receptor that that monkey possessed. Blood samples were to be taken, level of scarring and wounds analyzed, and observations done to predict their average level of aggressive activity. Oxytocin has been implicated in a number of pro-attachment behaviors, including bonding with pair-mates and offspring, but has conversely been shown to increase aggressive behaviors toward those who pose a threat to either of the afore mentioned. Because Rhesus macaques are notoriously aggressive, I was interested in seeing if the higher the levels of oxytocin would correlate with higher levels of aggression. However, due to some unforeseen obstacles, mostly the time it takes to gain approval for blood draws, I was not able to start collecting samples until the very end of the internship at the California National Primate Research Center (CNPRC). Consequently, I was not able to analyze scarring or submit samples yet for genotyping. I slightly changed my project, then, to focus more on the behavioral aspects of aggression, and used the CNPRC’s Bio- Behavioral Assessment (BBA)1 to analyze the changes in aggressive rates from infancy to adulthood. Furthermore, I selected subjects who had engaged in previous aggressive bouts, resulting in the loss of one or more of the following; finger, toe, tail. I hypothesized that the more body parts missing; the more aggressive that animal would be rated during observations. I also predicted that the animals that were most aggressive during behavioral observations would highly correlate with high anxiolytic reactions measured during the BBA process.
Subjects were 30 adult Rhesus macaques, with each animal missing one, two, three, or none of their fingers, toes, or tail. Each subject was observed a total of 4 times (morning and afternoon times) with each observation last 5 minutes. Frequency of behaviors recorded included; Social Proximity; Infant Proximity; Grooming; Walk-by’s; Give/Receive Aggression; Give/Receive Escalated Aggression; Give/Receive Displacement; and the number of social partners within proximity at the end of the 5 minutes observed. Data was then entered into an excel file, which was then analyzed using the SPSS program.
Preliminary results found high correlations for current aggressive behaviors and BBA assessed temperaments, showing a consistency in long term behaviors, especially with anxiety-related behaviors and vigilance scores, which seems to follow the studies hypotheses.
This study had many strengths and limitations, which is to be expected in a pilot study such as this. Because we had a large repository of information through the BBA Assessments, making it possible for many different analyses to be done before submitting a final paper with the results. Our N, however, was relatively small, with only 30 subjects analyzed. Due to the aggressive nature of the animals observed, we had to re-select some subjects simply because they died. Our findings, however, are very positive, showing that behaviors analyzed during infancy remain highly consistent in adulthood. Our next step will be to send blood samples from our subjects to be genotyped and analyzed for oxytocin levels. I would still like to see how oxytocin interacts with aggressive responses.
This study’s primary purpose was to see how aggressive rates correlated with the intensity of wound history and their temperaments during the BBA Assessment. Understanding how aggressive responses stay relatively constant throughout maturity is very important and can aid in future therapy tactics that can help human populations to re-work natural aggressive responses to obtain a different behavioral response to stressors. Further research is needed to continue looking into all the avenues in which aggression works, including the oxytocin receptor.
- The BBA is a battery of assessments done when a monkey is about 3-4 months of age. These assessments include HPA cortisol rates, levels of anxiety, movement, etc. after being separated from their mother. Infants are then returned to their mother no later than 25 hours after being separated, and are then returned to their neonatal group.