Researchers find key to boosting populations of bumblebees

Bumblebees need a diverse diet with lots of different flowers and landscapes in order to reproduce successfully, a study has shown.

The insects thrive when there are a ‘wide variety’ of flower-rich areas in the landscapes, from gardens to hedgerows to flower strips.

The research could help to safeguard their numbers.

Bumblebee numbers are declining – along with many other insects – and they are highly important pollinators, because they pollinate many different plant species and are extremely resilient.

They also manage to fly at temperatures that are too cold for other pollinators, according to researchers at the University of Gottingen in Germany.

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The scientists established bumblebee colonies in central and northern Germany and collected pollen from bumblebees returning to their hives in order to investigate the importance of pollen nutrition and habitat diversity.

Lead author Sandra Schweiger, a researcher in functional agrobiodiversity, said: "Our study shows that it is not individual habitats, such as flower-rich gardens, or semi-natural habitats, such as hedgerows or flower strips, that contribute to reproductive success for the large earth bumblebee Bombus terrestris.

"In fact, it is rather the diversity of habitats across the entire study landscape that is important.

"So a wide variety of flower-rich landscape elements must be present. In addition, a diverse pollen diet can contribute to better colony growth and more offspring, especially for young queens."

Professor Catrin Westpha said: "A balanced pollen diet reduces the negative effects of infestation of the colonies with parasitic wax moth larvae, which can severely harm the reproductive success of the bumblebees."

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Last year, a study warned that bees which are exposed to just one dose of pesticide have fewer offspring and can take generations to recover.

Researchers analysed the effects of imidacloprid, a neonicotinoid pesticide, on bees. Pesticides have been linked to population decline in bees, but researchers had never analysed the generational effects of the chemicals.

Clara Stuligross and Neal M Williams, of the University of California, exposed bees to the chemical in a controlled setting.

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They found that bee larvae exposed to the chemical produced 20% fewer offspring after they became adults.

They also found that multiple exposures led to even fewer offspring.

Those that were exposed as larvae, for example, and were then exposed again as adults had 44% fewer offspring, which, the researchers noted, represented approximately 10 fewer offspring out of a normal group of 24.

Watch: Are honeybees competing with bumblebees for resources?