Abstract:
Circadian rhythms in gut microbiota composition are crucial for metabolic function, yet the
extent to which they govern microbial dynamics compared to seasonal and lifetime processes
remains unknown. Here, we investigate gut bacterial dynamics in wild meerkats (Suricata
suricatta) over a 20-year period to compare diurnal, seasonal, and lifetime processes in
concert, applying ratios of absolute abundance. We found that diurnal oscillations in bacterial
load and composition eclipsed seasonal and lifetime dynamics. Diurnal oscillations were
characterised by a peak in Clostridium abundance at dawn, were associated with temperatureconstrained foraging schedules, and did not decay with age. Some genera exhibited seasonal
fluctuations, whilst others developed with age, although we found little support for microbial
senescence in very old meerkats. Strong microbial circadian rhythms in this species may
reflect the extreme daily temperature fluctuations typical of arid-zone climates. Our findings
demonstrate that accounting for circadian rhythms is essential for future gut microbiome
research.
