Suckling behaviour in three species of voles

Summary Domestic mammals exhibit diversity in suckling behaviour, yet little is known about suckling in most wild species, including rodents with tenacious nipple attachment. This behaviour, whereby young cling tightly to nipples, has been interpreted as an adaptation to competition within and among litters for nipples and milk. Comparative studies of suckling behaviour of tenacious and non-tenacious species are lacking, however, as are studies placing patterns of suckling in a phylogenetic context. We compared suckling in prairie voles (Microtus ochrogaster; tenacious nipple attachment), woodland voles (= pine voles, M. pinetorum; tenacious nipple attachment) and meadow voles (M. pennsylvanicus; non-tenacious nipple attachment). We hypothesized that suckling behaviour of meadow voles differs from that of the other two species. We found that meadow vole pups display higher frequencies of nipple attachment, shorter durations of nipple attachment (significantly different from prairie voles only), more frequent nipple-switching, and no preference for nipple pairs (prairie vole and woodland vole young preferred the hindmost nipples). Mapped onto a phylogeny, our data suggest a suite of behavioural characters associated with suckling in prairie and woodland voles (tenacious nipple attachment, preference for hindmost nipples, and infrequent nippleswitching) and highlight diversity of suckling behaviour among closely related species.