Let's stick together: Infection enhances preferences for social grouping in a songbird species

Abstract

Acute infections can alter foraging and movement behaviors relevant to sociality and pathogen spread. However, few studies have directly examined how acute infections caused by directly transmitted pathogens influence host social preferences. While infected hosts often express sickness behaviors (e.g., lethargy) that can reduce social associations with conspecifics, enhanced sociality during infection might be favored in some systems if social grouping improves host survival of infection. Directly assaying social preferences of infected hosts is needed to elucidate potential changes in social preferences that may act as a form of behavioral tolerance (defined as using behavior to minimize fitness costs of infection). We tested how infection alters sociality in juvenile house finches (Haemorhous mexicanus), which are both highly gregarious and particularly susceptible to infection by the bacterial pathogen Mycoplasma gallisepticum (MG). We inoculated 33 wild‐caught but captive‐held juvenile house finches with MG or media (sham control). At peak infection, birds were given a choice assay to assess preference for associating near a flock versus an empty cage. We then repeated this assay after all birds had recovered from infection. Infected birds were significantly more likely than controls to spend time associating with, and specifically foraging near, the flock. However, after infected birds had recovered from MG infection, there were no significant differences in the amount of time birds in each treatment spent with the flock. These results indicate augmented social preferences during active infection, potentially as a form of behavioral tolerance. Notably, infected birds showed strong social preferences regardless of variation in disease severity or pathogen loads, with 14/19 harboring high loads (5–6 log10 copies of MG) at the time of the assay. Overall, our results show that infection with a directly transmitted pathogen can augment social preferences, with important implications for MG spread in natural populations.

Social interactions do not affect mycoplasma infection in griffon vultures

“…Mycoplasma infection status was not related to social behavior during feeding or roosting, suggesting that the social interactions of griffon vultures do not impact mycoplasma infection. Our findings contrast with previous studies in which birds that were more social were also more likely to be infected with mycoplasma (Dhondt et al, 2007;Adelman et al, 2013;Adelman et al, 2015;Sawicka et al, 2020;Hawley et al, 2021;Briard & Ezenwa 2021;Langager et al, 2023). Thus, social behaviors may have different implications for mycoplasma spread across different bird and bacteria species (Sumithra et al, 2013;Sawicka et al, 2020).…”

Pathogen-Mediated Alterations of Insect Chemical Communication: From Pheromones to Behavior

“…Intriguingly, recent research has revealed that infection with the bacterial pathogen Mycoplasma gallisepticum Edward and Kanarek, 1960 (Mycoplasmatales: Mycoplasmataceae) can lead to an increase in social preferences among juvenile house finches Haemorhous mexicanus (P.L. Statius Muller, 1776) (Passeriformes: Fringillidae) [35]. Specifically, infected finches spent more time associating with healthy flocks compared with uninfected individuals, with significant implications for Mycoplasma transmission.…”