title: Investigating the impacts of field-realistic exposure to a neonicotinoid pesticide on bumblebee foraging, homing ability and colony growth.
abstract: The ability to forage and return home is essential to the success of bees as both foragers and pollinators. Pesticide exposure may cause behavioural changes that interfere with these processes, with consequences for colony persistence and delivery of pollination services.We investigated the impact of chronic exposure (5-43 days) to field-realistic levels of a neonicotinoid insecticide (2·4 ppb thiamethoxam) on foraging ability, homing success and colony size using radio frequency identification (RFID) technology in free-flying bumblebee colonies.Individual foragers from pesticide-exposed colonies carried out longer foraging bouts than untreated controls (68 vs. 55 min). Pesticide-exposed bees also brought back pollen less frequently than controls indicating reduced foraging performance.A higher proportion of bees from pesticide-exposed colonies returned when released 1 km from their nests; this is potentially related to increased orientation experience during longer foraging bouts. We measured no impact of pesticide exposure on homing ability for bees released from 2 km, or when data were analysed overall.Despite a trend for control colonies to produce more new workers earlier, we found no overall impacts of pesticide exposure on whole colony size.Synthesis and applications. This study shows that field-realistic neonicotinoid exposure can have impacts on both foraging ability and homing success of bumblebees, with implications for the success of bumblebee colonies in agricultural landscapes and their ability to deliver crucial pollination services. Pesticide risk assessments should include bee species other than honeybees and assess a range of behaviours to elucidate the impact of sublethal effects. This has relevance for reviews of neonicotinoid risk assessment and usage policy world-wide.
authors.affiliation: School of Biological Sciences Royal Holloway University of London Egham TW20 0EX UK; Botany and Plant Science School of Natural Sciences and Ryan Institute National University of Ireland GalwayIreland.
authors.forename: Dara A
authors.initials: DA
authors.lastname: Stanley
authors.affiliation: Graduate Interdisciplinary Program in Entomology and Insect Science University of Arizona Tucson AZ 85721 USA.
authors.forename: Avery L
authors.initials: AL
authors.lastname: Russell
authors.affiliation: Lunar and Planetary Laboratory University of Arizona Tucson AZ 85721 USA.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Morrison
authors.affiliation: School of Biological Sciences Royal Holloway University of London Egham TW20 0EX UK.
authors.forename: Catherine
authors.initials: C
authors.lastname: Rogers
authors.affiliation: School of Biological Sciences Royal Holloway University of London Egham TW20 0EX UK; School of Environmental Sciences University of Guelph Guelph ON N1G 2W1 Canada.
authors.forename: Nigel E
authors.initials: NE
authors.lastname: Raine
keywords: RFID tagging; agrochemical; bumble bee Bombus terrestris; flower‐visiting insects; insecticide; navigation; neonicotinoids; pesticide exposure; pollination