Oxygen consumption and evaporation during parturition in a vespertilionid bat (Pipistrellus pipistrellus)

Oxygen consumption and evaporation were measured in a single pregnant pipistrelle bat during labour and parturition of twins, using an open-flow respirometry system. During 233 min of measurements, three distinct phases were noted, which we suggest represent prelabour, labour and grooming or suckling the young. On the basis of this hypothesis, during labour and parturition, oxygen consumption was a maximum of 8.9% of daily energy expenditure, evaporation was 2.7% of daily water turnover, and total water loss was 5.5% of daily water turnover in free-living bats in early lactation. We estimated that, for the mother and young combined, oxygen consumption associated with grooming and suckling would be equivalent to 37.5% of daily energy expenditure of the mother, if carried out continuously. Similarly, evaporation due to grooming and suckling would be equivalent to 16.4% of daily water turnover. In terms of daily energy expenditure and daily water turnover, labour and parturition are therefore cheap, but grooming and suckling (even ignoring costs in terms of losses in the milk) are expensive.