New publicly funded research by scientists at the Rothamsted Institute in Hertfordshire shows honeybees remain excellent foragers, even when sick.

Honeybees learn the position of landmarks around their hive as they explore, which helps them find their way to rewarding flower patches and home again. When they first venture outside the hive, or when a beekeeper moves them to a new location, honeybees perform ‘orientation flights’ to explore and to identify landmarks efficiently. These orientation flights have an interesting property: the bees alternate between smaller movements of local exploring and occasional longer flights that bring them new areas – a characteristic pattern of exploration known as a ‘Levy flight’, also exhibited by turtles, basking sharks and human hunter-gatherers.

The research, published earlier this week, shows that honeybees stick to this movement pattern in their orientation flights, even when the insects are infected with two diseases. However, they cover less distance than healthy bees.

To track the flights, the researchers used a harmonic radar with tiny transponders stuck to the bees’ bodies. Scientists from Rothamsted Research, Queen Mary University of London, University of Sussex, University of Exeter and Martin-Luther University in Germany who conducted the experiment said their findings show bees’ can remain functional even when struggling with infectious diseases.

The findings are relevant because honeybees are such important pollinators of agricultural crop plants and wild flowers, and disease is one of the key pressures cited as a reason for declines in bee populations in recent years. Bee species are also facing pressures from climate change, habitat loss and exposure to certain pesticides.

Honeybees can cover areas up to 300km squared in search of flowers. To find out more about how disease affects the bees’ movement, the researchers compared healthy bees with those infected either with a microscopic gut parasite called Nosema, or with the deformed wing virus that is spread by varroa mites. Using harmonic radar, they tracked 78 bees as they performed orientation flights.

Although diseased bees still exhibit the characteristic Levy flight pattern, the infections reduced their flying abilities. Bees with Nosema infection flew only half as far as healthy ones, covering just a third of the area, though their flight speeds were similar. Deformed wing virus had little effect on the distances the bees flew. However, the fact that diseases don’t alter exploring behaviour in the same way as, for instance, the time that bees allocate to different tasks, may have a basis in the structure of the bees’ brains.

Dr Stephan Wolf, lead author of the study, explained, “These remarkably robust searching abilities indicate that these are not learned but rather are hardwired in the bees, making them robust against pathogens and possibly other stressors and allowing these bees to still contribute to their colony”.