Social distancing used by honeybees to fend off parasites

Social distancing isn’t limited to humans as a new study has found that honeybees also use social distancing to protect against parasites. The study has been published in in Science Advances.

Social distancing among honeybees is generally seen when hive is under threat from a parasite. The study demonstrated that honeybee colonies respond to infestation from a harmful mite by modifying the use of space and the interactions between nestmates to increase the social distance between young and old bees.

The study provides the first of its kind evidence of such a behavior among honeybees. We already know that honeybees are social insects and interact among themselves through touch. These social interactions can increase the risk of infection, the bees appear to have evolved to balance the risks and benefits by adopting social distancing.

Among animals, examples of social distancing have been found in very different species separated by millions of years of evolution: from baboons that are less likely to clean individuals with gastrointestinal infections to ants infected with a pathogenic fungus that relegate themselves to the suburbs of anthill society.

The new study evaluated if the presence of the ectoparasite mite Varroa destructor in honeybee colonies induced changes in social organisation that could reduce the spread of the parasite in the hive. Among the stress factors that affect honeybees, the Varroa mite is one of the main enemies as it causes a number of harmful effects on bees at individual and colony level, including virus transmission.

Honeybee colonies are organised into two main compartments: the outer one occupied by the foragers, and the innermost compartment inhabited by nurses, the queen and brood. This within-colony spatial segregation leads to a lower frequency of interactions between the two compartments than those within each compartment and allows the most valuable individuals (queen, young bees and brood) to be protected from the outside environment and thus from the arrival of diseases.

By comparing colonies that were or were not infested by the Varroa mite, the researchers found that one behaviour, foraging dances, that can increase mite transmission, occurred less frequently in central parts of the hive if it was infested. They also found that grooming behaviours became more concentrated in the central hive. The researchers say it appears that overall, foragers (older bees) move towards the periphery of the nest while young nurse and groomer bees move towards its centre, in response to an infestation, to increase the distance between the two groups.

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