No evidence for avoidance of visibly diseased conspecifics in the highly social banded mongoose (Mungos mungo)

Abstract

Individual host behavior may be influenced by infectious disease in ways that can alter population-level disease dynamics. A novel pathogen in the Mycobacterium tuberculosis complex, Mycobacterium mungi, has emerged among banded mongooses (Mungos mungo) in Northeastern Botswana. This host–pathogen system provides an opportunity to study how individual behavior and social interactions in a group-living species might respond to infectious disease. We used repeated focal observations of known individuals with an extensive ethogram to identify behavioral differences and social interactions between healthy individuals and those with clinical signs of tuberculosis (TB). Clinically diseased banded mongooses exhibited a significantly smaller proportion of time active and alert, a larger proportion of time resting, and a slower behavioral transition rate compared to healthy individuals. They also showed lower reciprocation of allogrooming by approximately 50 %. Despite these strong behavioral differences that may serve as visible cues for healthy mongooses to avoid diseased conspecifics, we found no evidence for avoidance of clinically diseased mongooses by healthy individuals or vice versa: Clinically diseased individuals did not have lower levels of social behaviors than healthy individuals, and clinically diseased mongooses were allogroomed at the expected level despite their decreased reciprocation. Our results show that in contrast to prior studies of other species, avoidance of diseased conspecifics did not occur in this highly social species. We discuss hypotheses for this lack of avoidance and potential implications for pathogen transmission.