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Jenna DiNapoli
&
Dr. Vicky Oelze
Primate Ecology and Molecular Anthropology (PEMA) Lab
Introduction
Female chimpanzees (Pan troglodytes) tend to disperse from their natal community upon reaching sexual maturity. Arriving in a new community with a sexual swelling as a “social passport” is thought to aid in soliciting male support and reducing hostility from resident females. However, the integration process into a new community is not well documented, as immigrant females tend to be unhabituated to human researchers, preventing direct observations.
This project investigates several aspects of the social integration of immigrated females into a chimpanzee community utilizing long-term camera trap (CT) footage. Our focal subjects are two identified immigrant female chimpanzees, named Kasolya and Corona, which we follow through the first months and years of their social integration process, offering insights into how adolescent female chimpanzees navigate the potentially costly event of dispersal and form social relationships within a new community.
We document the utility of CTs to monitor newly arriving females in comparison to observational data, and how newly immigrated females react to CTs in their new surroundings. We then monitor the nature and duration of sexual swellings in these immigrant female chimpanzees to test the social passport hypothesis. Further, we explore the process of social integration by assessing which community members (sex and age class) they initially associate with in close proximity and how this changes with time. We also assess temporal changes in the demographic aspects of social interactions and evaluate the nature of these behavioral exchanges, and whether these are affiliative, agonistic, or sexual.
Methods
Using camera trap footage spanning from 2017-2020:
I documented CT reactions which included staring directly at the camera for several consecutive seconds, acting nervous or spooked, touching the camera, or any other interaction or behavior instigated by the presence of the CT.
I developed categories to estimate physical proximity to other individuals (body-contact, being within arms-reach, < 3m away, or > 3m away)
To obtain information about the duration that sexual swellings were maintained, I created a scoring guide from 0 - 3. These scores were assigned based on swelling size (0 being none) and aimed to show how long new female chimpanzees maintain their adolescent swelling and exhibit their first adult size swelling after immigrating to new community.
Behavioral data focused on all behaviors received by immigrant females by other chimpanzees from the Issa study community. I constructed an ethogram to categorize specific behavior as affiliative, agonistic, or sexual, and whether these behaviors were received by adult females, by adult males, and or by immatures.
Results
Results
Detection
Between 2017-2020, ~14,786 videos were recorded of the Issa chimpanzees. Of these, 487 were of immigrant female chimpanzees during the first months and years in which they arrived at their new community.
371 videos recorded of Kasolya
116 videos of recorded of Corona
Swelling variation.
Kasolya exhibited a swelling with a score of 1 in every video for the first 5 months after her arrival. Her first maximal swelling occurred 2 years after she transferred into the group.
The first video recorded of Corona showed a swelling score of 1, however she was not recorded again until August of 2020, with a swelling score of 2. From then on, her swellings seem to exhibit a typical estrous cycle.
CT reactions
CT reactions were anticipated to be more frequent during the first months of the immigrant female chimpanzee arriving at a new community, and reduce in frequency as the individuals became habituated to their presence.
Kasolya exhibited most CT reactions within her first year (2018), less in her second year (2019) and by 2020 had no CT reactions at all.
While Corona had less overall footage available, the last month of footage showed no CT reactions.
Party size, composition, and proximity
We found that both immigrant females were in close proximity most often with immature males, and for Kasolya, this was followed by adult males.
Behavior Results for Kasolya
Behavioral results for Corona
Affiliative behavior was usually during co-feeding events for all age-sex class. Most agonistic behavior from adult males was from displays.
Sexual behavior was received from immature males more often than adult males
Conclusion
Conclusion
Photos courtesy of GMERC
Using camera trap footage in this context has never been tested before, and my results show their utility in detecting early observations of immigrant female chimpanzees and several aspects of the social integration process
Acknowledgements
Acknowledgements
Thank you to the Koret Foundation for the financial support during this project, and Dr. Vicky Oelze for her mentorship and guidance throughout. I thank the Greater Mahale Ecosystem and Conservation (GMERC) leadership team, Alex Piel and Fiona Stewart for their collaboration with the PEMA lab at UCSC as well as the Chimpanzee Video Coding Team members who have coded all camera trap footage between 2017 and 2020. Our team thanks the Tanzania Wildlife Research Institute (TAWIRI), Tanzania Commission for Science and Technology (COSTECH), and Tanganyika District for permission to carry out this research using camera traps. Finally, we are immensely grateful to the GMERC field teams for regular maintenance of the camera trap arrays over the years.
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