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Abstract1. Substantial reductions in the distributional ranges of several species of bumblebee have been recorded in the UK. Loss and fragmentation of suitable foraging and nesting habitat to agricultural intensification is thought to be the main driving force behind declines.2. Limited knowledge of species ecology means that effective conservation management prescriptions cannot be put into place.3. Here we investigated the spatial dynamics of two UK Biodiversity Action Plan bumblebee species, Bombus sylvarum and Bombus humilis. For the first time, microsatellite DNA analysis was used to estimate foraging distances in rare bumblebees.4. Sisterhoods were identified between bees sampled at discrete forage patches within a fragmented landscape. Using these sisterhoods, minimum estimates of maximum and mean foraging distances were calculated from distances separating sister bees.5. Minimum mean foraging distances were calculated as 475 ± 97m for B. humilis and 231 ± 58m for B. sylvarum. Mean distances were significantly greater for B. humilis than B. sylvarum (P<0.001).6. The differences between the spatial scales that the species were recorded over highlighted a need for further research into the spatial dynamics of rare and more ubiquitous foraging bumblebees.4