Jennifer Siani

Golden Lion TamarinJennifer Siani

Advisor: Jim Dietz
PhD Graduate, '09, Behavior Ecology Evolution Systematics
From: Pennsylvania
Education: Bachelor of Science in Animal Bioscience from Pennsylvania State University, 2001
Research location: Poço das Antas Biological Reserve, Rio de Janeiro State, Brazil
Interesting Fact: She had never been camping before conducting international field work.

Since Washington D.C. is such a hotspot for government and nonprofit organizations as well as being full of networking opportunities, Jennifer felt that UM was the ideal place to be. As a graduate student in the BEES program, Jennifer decided to focus on parent-offspring interactions, which she believes are a fundamental component of her primary interest, social behavior. She became familiar with a small primate called the golden lion tamarin and was very attracted to the complexity of their social behaviors.

Jennifer Siani
Golden lion tamarins are one of the most unique and rare species in the world, with just over 1,000 individuals found in the wild.
Golden Lion Tamarin

Why Golden Lion Tamarins are Cooperative Caretakers

Golden lion tamarins (GLTs) are one of the most unique and rare species in the world, with just over 1,000 individuals found in the wild at the Poço das Antas Biological Reserve in Brazil. They live in groups of 3-13 individuals, and the dominant female can have up to four babies each year. Jennifer wanted to figure out why GLTs would take care of infants that aren't their own - why they would want to be cooperative caretakers. To do this Jennifer looked at three different things: infant preference for caregivers and the distribution of infant care, the cost of caretaking to individuals, and how infant signals affect caretaking.

To investigate the distribution of infant care, Jennifer determined whether there was a reproductive division of labor such that certain individuals predominantly carried infants while others predominantly provided solid food. She also measured the rates of initiations and rejections of care by both caregivers and infants to see if caretakers had preferences for certain infants and vice versa. Jennifer found that there were no biases based on infant or caregiver sex for the amount or type of care given regarding solid food and transportation.

Jennifer then looked at whether there was a cost to the individuals in terms of a change in physical condition and/or time budgets. To do this she used her behavior data and the weights of group members over three field seasons. She found that behavioral changes and time allocation costs do occur, but physical costs do not occur for caregivers. Thus, just because changes in time allocation are being made there is not necessarily an energetic cost. This indicated to her that caregivers could just be flexible in their time allocation, not necessarily that there is a reduction in effectiveness of care strategy. Though there do not appear to be ecological costs of care, Jennifer is still trying to determine whether this is true.

Understanding Infant Calling Signals

Finally, Jennifer wanted to look into infant calling signals. GLT infants essentially cry all the time indicating that these signals may give caregivers clues to the needs of the infants since there are potential costs to crying constantly such as high-energy outputs and increased predation probability. Jennifer wanted to know which caregivers respond to infant signals, if they were more likely to respond when engaged in certain activities and if caregivers were more likely to respond to the cries when they were from an infant in their group. To measure this she recorded vocalizations of different infants and then played the cries back to each separate group and monitored caregiver behavior. She found that reproductive individuals, both the mother and father, were more likely to respond to the infants' cries. The overall response rate was fairly high at 40%, and caregivers were more likely to respond when traveling but there were no behavior categories that prohibited a response. She did not see variation in the response rate based on the coefficient of relatedness between the infant and caregiver. As a result Jennifer does not believe that GLTs discriminate kin based on the infant's vocalizations.

Moving Forward with Monkey Research

Overall, Jennifer was trying to address variation in infant care from the standpoint of caregivers and infants. She would like her work to be used in order for other researchers to reassess the explanations of why cooperative care giving occurs. She is not convinced that it is related to issues of energy costs and believes that more research needs to be performed regarding the influence of infants on cooperative care. In the future Jennifer thinks that this information could help us understand the behavior of human babies. In addition, she hopes that this study will trigger other researchers to increase the number of wild monkey research on infants in order to develop a better understanding of how all of the components interact outside of a regulated environment.

Jennifer has not yet chosen a future path but is interested in animal welfare issues and animal control. To this end she is looking at positions related to population dynamics and wildlife management in the government and non-profit sectors.