Trapline foraging by bumble bees: II. Definition and detection from sequence data

Trapline foraging—repeated sequential visits to a seriesof feeding locations—presents interesting problems seldomtreated in foraging models. Work on traplining is hampered bythe lack of statistical, operational approaches for detectingits existence and measuring its strength. We propose severalstatistical procedures, illustrating them with records of interplantflight sequences by bumble bees visiting penstemon flowers.An asymmetry test detects deviations from binomial expectationin the directionality of visits between pairs of plants. Severaltests compare data from one bee to another frequencies of visitsto plants and frequencies of departures to particular destinationsare compared using contingency tables; similarities of repeatedsequences within bees are compared to those between bees bymeans of sequence alignment and Mantel tests. We also comparedobserved movement patterns to those generated by null modelsdesigned to represent realistic foraging by non-traplining bees,examining: temporal patterns of the bee's spatial displacementfrom its starting point using spectral analysis; the varianceof return times to particular plants; and the sequence alignmentof repeated cycles within sequences. We discuss the differentindications and the relative strengths of these approaches