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A Physiological Evaluation of Social Bonding in Western Lowland Gorillas (Gorilla gorilla gorilla).

Leeds, Charles Austin

Abstract Details

2019, Doctor of Philosophy, Case Western Reserve University, Biology.
The strength of one’s social bonds has direct links to fitness, health and welfare. Evaluations of social bond strength are relatively straightforward for gregarious species through direction observation of affiliative behavior, but can prove difficult for less gregarious species. The western lowland gorilla (WLG: Gorilla gorilla gorilla) is one such social species that engages in low rates of affiliative behavior. Assessing variation in the neuroendocrine hormone oxytocin (OXT), which is the physiological driver of social bonds, in relation to social demographic variables may prove useful to better understand how gorilla form bonds and how these bonds vary in the zoo environment. The overall objective of this dissertation was to evaluate variation in WLG salivary and urinary OXT. Biological samples were collected from 143 gorillas living at 25 zoos. Using both experimental and exploratory methodology, this dissertation successfully validated the measurement of OXT in unextracted WLG saliva and urine. Specifically, significant changes in both salivary and urinary OXT were detected following an intranasal challenge and spontaneous social events. This methodology was then used to assess variation in OXT following interactions with animal care staff (ACS) and in baseline samples. Following positive reinforcement training with ACS, salivary OXT concentrations did not change, but OXT did increase following play with ACS. This indicates that relationships between WLG and ACS in zoos, at least in certain contexts, are viewed as positive and affiliative by WLG. In a large-scale evaluation of OXT, multiple demographic and husbandry factors were associated with variation in OXT. Notably, OXT was greater in males living in bachelor groups compared to mixed-sex groups, providing evidence that male WLG form comparatively stronger bonds with other males than with females. This is supported by field studies of WLG that demonstrate males form dispersed, affiliative social networks with related males. Greater OXT concentrations were also associated with lactation in female WLG. This finding was expected based on the natural functioning of OXT and further validated our measurement of OXT in unextracted urine. Lastly, ACS perceptions of bonding were assessed in relation to OXT. Interestingly, ACS ratings of social bonding did not differ between mixed-sex and bachelor groups, indicating ACS perceive both group types to provide meaningful social environments for WLG. ACS also identified peripheral group members within their respective WLG groups. Peripheral status was negatively associated with OXT concentrations, indicating more socially distant group members maintained comparatively weaker social bonds than more integrated group members. Overall, these findings have improved our understanding of how WLG form social bonds and how social bonds vary in relation to husbandry and management practices. Of specific importance, this study further demonstrates the significant social value of bachelor groups for male WLG.
Kristen Lukas, PhD (Committee Chair)
Mandi Schook, PhD (Committee Member)
Patricia Dennis, DVM, PhD (Committee Member)
Mark Willis, PhD (Committee Member)
Tara Stoinski, PhD (Committee Member)
201 p.

Recommended Citations

Citations

  • Leeds, C. A. (2019). A Physiological Evaluation of Social Bonding in Western Lowland Gorillas (Gorilla gorilla gorilla). [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1554396989561718

    APA Style (7th edition)

  • Leeds, Charles. A Physiological Evaluation of Social Bonding in Western Lowland Gorillas (Gorilla gorilla gorilla). 2019. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1554396989561718.

    MLA Style (8th edition)

  • Leeds, Charles. "A Physiological Evaluation of Social Bonding in Western Lowland Gorillas (Gorilla gorilla gorilla)." Doctoral dissertation, Case Western Reserve University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1554396989561718

    Chicago Manual of Style (17th edition)