Immunoglobulin A and Physiologic Correlates of Well-Being in Asian Elephants

Zoological institutions aim to continually improve the lives of the animals under their stewardship. To this end, bull elephants are now increasingly maintained in all-male groups to mimic social conditions observed in the wild. While cortisol is the most frequently used “stress” biomarker, secretory immunoglobulin A (sIgA) as a measure of health and positive affect, and the social hormone, oxytocin, are increasingly viewed as additional markers of welfare. The introduction of a pair of bull elephants to an existing group of three bull elephants at Denver Zoo presented an opportunity to assess sIgA, oxytocin and cortisol in response to the socialization process. In this study, sIgA varied greatly between individuals and did not correlate with cortisol but did correlate with salivary oxytocin. sIgA and oxytocin concentrations differed the most between social and solo situations during the introduction period compared to before bulls were introduced, and after a stable group had been formed. In contrast to findings in some species, sIgA and oxytocin were higher when housed alone than socially. Nonetheless, these results suggest that sIgA and oxytocin may be involved in social engagement and establishment of new social dynamics, and thus provide more insight into overall welfare states.