Contrasting the roles of learning in butterflies foraging for nectar and oviposition sites

Abstract

We successfully trained adult Edith's checkerspot butterflies, Euphydryas editha, to modify their alighting preference for a novel flower and to reduce their handling time when searching for nectar in a flower that was difficult for them to use. Butterflies caught feeding from the difficult flower (manzanita, Arctostaphylos spp., Ericaceae) in the field were able to find its nectar more quickly than butterflies caught feeding from a simpler flower (pussypaw,Calyptridium umbellatum , Portulacaceae), providing evidence that these learning abilities contribute to natural foraging behaviour. The strong role of learning in nectar foraging contrasts with results of prior experiments that failed to show any role of learning in oviposition behaviour by butterflies in the same population that we studied. These butterflies had failed both to improve their finding of host plants with experience and to change their host preferences as a result of exposure to different hosts. Euphydryas editha can learn to prefer and use particular nectar species, but do not learn to prefer or find plants for oviposition. Comparison between oviposition and host feeding is consistent with theoretical predictions that learning should be more pronounced with respect to behaviours whose performance provides information about effects on fitness, or where each of many performances has a small effect on fitness. It is not consistent with the hypothesis that learning may occur in some behaviours because it is necessary in other contexts.