'Ambidexterity' in bat wings as evidenced by bone weight

1. Comparable right and left wing bones of three species of bats failed to demonstrate one-sided dominance, although such dominance is widespread in tetrapods. 2. When similar units are compared, some of the bones from one side are heavier, some are lighter, than those from the other side. This appears to represent a compensatory mechanism for achieving balanced weight and propulsion. 3. The criterion used by Dogra & Singh (1971) for deciding whether or not a difference exists between comparable units (i.e. that an observed difference in weight is 'real' if the difference is at least one per cent of the weight of the greater element) is not statistically valid in the three species of bats used in this study. Sole use of this criterion to determine one-sided dominance can therefore be misleading.