estimation of worker ant populations by the mark-release-recapture method: an improved marking technique

(1) The methods for estimating ant populations were reviewed and the Petersen method appeared best, although previous workers had experienced difficulties with contamination when using radioactive markers. (2) A satisfactory technique of marking was developed, which involved feeding with the isotope 32P and then starving for a period of days before release to prevent trophallactic exchange. (3) It is shown that marked workers of the genera Tetramorium, Lasius and Myrmica retain the 32P in their tissues and do not pass it to unmarked individuals. (4) Ant mortality is not increased by marking. (5) Methods of counting live marked samples using Geiger-Muller probes and the preparation of autoradiographs are described. (6) The method was used to estimate field populations at Newborough Warren National Nature Reserve, and the mean worker populations for colonies were found to be: M. rubra 954+-144 (eighteen estimates, thirteen colonies), M. ruginodis 579+-77 (nine estimates, six colonies), Lasius niger 5462+-812 (sixteen estimates, nine colonies). (7) The present data are compared with other ant population data obtained by the Petersen method.