Testing assumptions of mark-recapture protocols for estimating population size using Australian mound-building, subterranean termites

1. Forager population size of two species of mound-building, subterranean termite (Coptotermes lacteus, Rhinotermitidae and Nasutitermes exitiosus, Termitidae) was estimated using three mark-recapture protocols. These estimates varied widely within and between colonies (approximate to 0.3-200 million for C. lacteus and 0.2-3 million for N. exitiosus). The variation in the estimates is explained in part by violation of the assumptions of the protocols.

2. The fat-stain markers, although persistent in the laboratory, faded rapidly in the field, and were transferable from marked individuals to unmarked individuals by cannibalism.

3. Marked individuals did not mix randomly or evenly with unmarked foraging individuals in space or time, as marked individuals were recaptured in widely varying numbers at different feeding sites sampled simultaneously. Importantly, foragers displayed feeding site fidelity and avoided disturbed feeding sites.

4. The likelihood of recapture differed between castes and instars; there was a higher recapture rate of large workers and soldiers relative to smaller workers.

5. The mark-recapture protocols provided inaccurate and unreliable forager population estimates, up to two orders of magnitude larger than direct counts of entire mound colonies. Thus the weighted mean estimates from more complex triple-mark-recapture protocols were not necessarily better than Lincoln index estimates from simpler single-mark-recapture protocols.

6. Mark-recapture studies may provide useful information about forager behaviour and foraging territories.