This study investigates the metabolic factors driving the division of labour in cooperatively breeding Damaraland mole-rat (Fukomys damarensis) colonies, particularly during digging activities. In these highly social mammals, non-breeding males and females (NBFs), often known as ‘helpers’, handle most of the colony's labour, while queens perform less physically demanding tasks. We examined how glucose and lactate, key energy sources, are used during digging. While both queens and NBFs showed similar drops in glucose after digging, lactate dynamics revealed a crucial difference: NBFs experienced a significant decrease in plasma lactate, indicating they efficiently recycle lactate into energy. In contrast, queens exhibited a slower clearance of lactate, which may contribute to their quicker transient fatigue and limited involvement in burrowing tasks. This suggests that NBFs utilize lactate as an additional energy source, allowing them to dig for longer without accumulating the transient fatigue associated with lactate buildup. These findings highlight the role of lactate metabolism in supporting sustained physical activity in NBFs, revealing a physiological basis for the division of labour in mole-rat colonies. Beyond their reproductive and social roles, differences in how individuals rely on metabolic pathways may help explain why helpers take on the majority of a colony's physically demanding tasks.