Cooperative breeding often evolved in harsh and arid habitats characterised by high levels of environmental uncertainty. Most forms of cooperative behaviour have energetic costs and previous studies have shown that the contributions of individuals to alloparental provisioning are conditional on the food intake of individuals. However, the effect of naturally occurring, extreme environmental conditions on the persistence of costly forms of cooperative behaviours and their coordination by communication remain unknown. Here, we show that in meerkats (Suricata suricatta) the probability to act as sentinel, a cooperative vigilance behaviour, was the same for typically occurring dry and wet conditions, but significantly reduced during a drought condition with almost no rain, especially in young individuals, members of small groups and groups with pups. The duration an individual stayed on sentinel guard, however, was most reduced during dry conditions. Besides reductions in sentinel behaviour, the vocal coordination of foraging meerkats differed when comparing drought and wet conditions. Individuals responded more strongly to playbacks of sentinel ‘all-clear’ calls and close calls, resulting in less vigilance and more foraging behaviour during the drought condition. We conclude that while meerkats are adapted to commonly occurring dry periods with low rainfall, the extreme drought period with almost no rain, led to a decrease of the frequency of costly forms of cooperative behaviours in favour of behaviours that maximize direct fitness benefits and also affect the vocal coordination among group members.