Supplementary material from "Lactate as a Key Energy Source Facilitating Cooperative Behaviour in Helper Damaraland Mole-Rats"

This study explores the metabolic factors that may aid in the division of labour in cooperatively breeding Damaraland mole-rat (Fukomys damarensis) colonies, particularly during digging activities. In these group-living mammals, both breeders and non-breeders participate in digging, among other cooperative tasks; however, non-breeding males and females (NBFs), often referred to as ‘helpers’, undertake this task at a higher frequency and engage in other energetically demanding activities more often than their breeding counterparts. We investigated how variation in glucose and lactate levels, two key energy substrates, relates to different levels of digging activity between breeders and non-breeders, and how these metabolic patterns might underpin reproductive differences in activity and energy budgets. While both breeding females (BFs) and NBFs exhibited similar decreases in glucose levels after digging, lactate dynamics revealed a key distinction, NBFs experienced a significant drop in plasma lactate, suggesting lactate utilisation. In contrast, BFs showed an increase in lactate, indicating its accumulation rather than utilisation, potentially contributing to their reduced involvement in digging activity. These findings suggest that lactate recycling and metabolism may play a crucial role in sustaining prolonged physical exertion in NBFs, providing a potential physiological explanation for the division of labour in mole-rat colonies.