Investigating social networks and their benefits in captive ring-tailed lemurs

Student Spotlight - Lina Syrimi

Undergraduate Research at the University of Derby

Email: pantelinasyrimis@gmail.com

 

Project Poster

Project Summary

Social interactions among individuals are vital for the formation of complex social relationships and structures in human and non-human societies ^1-2. For animals that live in groups, complex relationships induce the evolution of behavioural strategies such as cooperation, where individuals of the group help each other in some way. Cooperation, often at a cost to the individual giving the help, seems to go against current scientific theory that individuals act in their best interests to increase their own survival and reproduction chances ³. However, the reciprocation of behaviours such as grooming and huddling could favour cooperation among individuals.

Via the application of social network analysis (SNA), the diagrammatic representation of an animal group can be visualized (e.g Figure 1 below). Thus, the social network systems of species can be interpreted and understood on a deeper level ⁴.

Figure 1 - Example of Social Network Analysis (SNA) visualisation depicting the display (F) and reception (R) of affiliative interactions among the individuals of enclosure three. The directionality and thickness of the lines vary among the individuals who instigate (F) and receive (R) interactions.

Female dominance and the complexity of social structures in ring-tailed lemurs (Lemur catta) make this species intriguing to apply SNA to. The directionality of different interactions (who interacts with whom) was expected to vary with individual characteristics like age, dominance, and sex, and affect their social networks as well as the acquisition of the corresponding social benefits.

This hypothesis was tested on 36 captive ring-tailed lemurs. The lemurs were housed in three separate enclosures at Pafos Zoo, Cyprus. In total, instantaneous scan sampling was used to collect 924 total hours of affiliative, agonistic, sexual, and submissive interactions from June to September 2021. Using photo identification to memorize the different features of each lemur and identify them during the observations was challenging. Nevertheless, it was a great alternative method for identifying the individuals, as handling the lemurs to fit collars around their neck could result in them experiencing stress.  

Overall, I found that the social structure was mostly maintained via affiliative behaviours. Although previous studies found submissive individuals to instigate most one-sided affiliative interactions ⁵, the results indicated that in a troop, affiliation was mostly exhibited by adult females. Maternal care, assertiveness, and higher levels of oxytocin found in more dominant individuals could explain these results ^6-8. Among adult and immature females, affiliation and aggression were associated with dominance. Among males, aside from affiliation and aggression, dominance was also associated with the display of sexual behaviours.

Adult females had access to most social benefits, such as access to the new-born, food resources, and receiving affiliative interactions. However, submissive females who were affiliative or older had access to social benefits like receiving grooming and having access to allogrooming (when two individuals are simultaneously grooming each other) and huddling sessions. In males, dominant or affiliative males were the ones to obtain the most social benefits, such as access to food, playing, and huddling sessions. These findings were in agreement with those of previous research ⁹, which demonstrated that females display higher tolerance to affiliative and central males.

My study was subject to a few limitations. The age of most lemurs and their relatedness to each other was unknown. Moreover, there was an imbalance between the sample sizes of the three enclosures, with enclosures two and three having a much smaller sample size than enclosure one.

Nevertheless, future studies could accommodate for the complications I faced and account for other variables such as the effect of personality variations in the display of different behaviours in captive and free-ranging ring-tailed lemurs.

References

1. Wey, T., Blumstein, D., Shen, W. and Jordán, F. (2008) Social network analysis of animal behaviour: a promising tool for the study of sociality. Animal Behaviour, 75, 333-344. https://doi.org/10.1016/j.anbehav.2007.06.020
2. Gelardi, V., Godard, J., Paleressompoulle, D., Claidiere, N. and Barrat, A. (2020) Measuring social networks in primates: wearable sensors versus direct observations. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 476, p.20190737. https://doi.org/10.1098/rspa.2019.0737 
3. Fehl, K., Daniel, J. van der Post and Semmann, D. (2011) Co-evolution of behaviour and social network structure promotes human cooperation. Ecology Letters, 14, 546-551.  https://doi.org/10.1111/j.1461-0248.2011.01615.x
4. Funkhouser, J., Mayhew, J. and Mulcahy, J. (2018) Social network and dominance hierarchy analyses at Chimpanzee Sanctuary Northwest. PLOS ONE, 13, e0191898. https://doi.org/10.1371/journal.pone.0191898
5. Nakamichi, M. and Koyama, N. (1997) Social relationships among ring-tailed lemurs (Lemur catta) in two free-ranging troops at Berenty Reserve, Madagascar. International Journal Of Primatology, 18, 73-93. https://doi.org/10.1023/A:1026393223883
6. Plesker, R. and Mayer, V. (2008) Nonhuman primates mask signs of pain. Laboratory primate newsletter, 47, 1-30.
7. Li, Y., Hassett, A. and Seng, J. (2019) Exploring the mutual regulation between oxytocin and cortisol as a marker of resilience. Archives of Psychiatric Nursing, 33, 164-173. https://doi.org/10.1016/j.apnu.2018.11.008
8. Nandam, L., Brazel, M., Zhou, M. and Jhaveri, D. (2020) Cortisol and Major Depressive Disorder—Translating Findings From Humans to Animal Models and Back. Frontiers in Psychiatry, 10, 1-15. https://doi.org/10.3389/fpsyt.2019.00974
9. Gould, L. (1997) Affiliative relationships between adult males and immature group members in naturally occurring ringtailed lemurs (Lemur catta). American Journal of Physical Anthropology, 103, 163-171. https://doi.org/10.1002/(sici)1096-8644(199706)103:2<163::aid-ajpa3>3.0.co;2-v