Population assessment and foraging ecology of the rare solitary bee Anthophora retusa at Seaford Head Nature reserve

Anthophora retusa is a rare solitary bee which has declined throughout Britain and other European countries since the 1990s. It is thought to be restricted to five sites in Britain. However, information on these remaining populations is limited. Knowledge on population size, dispersal distance, habitat and forage requirements are important for successful conservation of species. The population of A. retusa at the Seaford Head Nature reserve in East Sussex was surveyed. Using mark recapture the population was estimated in 2018 and 2019 to be fewer than 200 individuals, with the male population increasing from 47 in 2018 to 167 in 2019. The female population was 44 in 2018 but due to zero recaptures in 2019, no population estimate was possible. Bees seem to be geographically restricted to a 25ha area within the reserve. The most visited flower species by females was Glechoma hederacea (66% of visits) but flower preference changed throughout the flight season, shifting to Fabaceae species and Iris foetidissima with 16 plant groups identified in pollen samples. Although the exact location of nesting sites was not determined with certainty it’s thought they are nesting in the loess deposits at the top of the inaccessible sea cliff face. The average distance between recaptures was 122m, perhaps indicating low dispersal. This project suggests the presence of appropriate nesting sites, potentially soft exposed soil, may be limiting A. retusa distribution as they appear to forage on common plant species. More research is needed on the exact nesting requirements of the species.