Even honeybees know instinctively to use social distancing when their hive is under attack from a parasite, finds a new study published in Science Advances (1). A team involving researchers from University College London, UK, and the University of Sassari, Italy, found that colonies of honeybees react to the presence of mites by increasing the space between young and old bees and reducing the number of interactions.
The study looked at multiple colonies, including hives infected with the mite Varroa destructor and healthy hives, to determine how the bees would attempt to reduce the spread of the parasite in the colony. The Varroa mite is one of the most serious enemies in honeybee colonies and the most important factor in the global honey bee health decline.
Honeybee colonies have an outer compartment, where the adult bees work, and an inner compartment exclusive for the queen and the brood. The researchers found that bees minimise contact between the two chambers when the hive is infected, allowing the most valuable individuals—the queen and young bees— to be protected from the outside environment and spread of disease.
“Here, we have provided the first evidence that honeybees modify their social interactions and how they move around their hive in response to a common parasite,” said Dr. Alessandro Cini, from the UCL Centre for Biodiversity & Environment Research, UCL Biosciences, and one of the authors of the study. “Honeybees are a social animal, as they benefit from dividing up responsibilities and interactions such as mutual grooming, but when those social activities can increase the risk of infection, the bees appear to have evolved to balance the risks and benefits by adopting social distancing.”
Comparing healthy and infected hives, the team observed that honeybees refrain from participating in foraging dances, which can easily increase mite transmission. It seems that adult bees tend to spread out and move towards the periphery of the hive, while young bees and the queen move towards the centre. This behaviour increases the distance between the two groups and minimises the spread of disease.
“The observed increase in social distancing between the two groups of bees within the same parasite-infested colony represents a new and, in some ways, surprising aspect of how honeybees have evolved to combat pathogens and parasites,” said Dr. Michelina Pusceddu, from the Dipartimento di Agraria, University of Sassari.
“Their ability to adapt their social structure and reduce contact between individuals in response to a disease threat allows them to maximise the benefits of social interactions where possible and to minimise the risk of infectious disease when needed. Honeybee colonies provide an ideal model for studying social distancing and for fully understanding the value and effectiveness of this behaviour.”
Curiously, this is not the only example of social distancing in wild animals. For example, baboons avoid contact with other animals with gastrointestinal infections, and ants infected with a pathogenic fungus will remove themselves from their community.
(1) Pusceddu M, Cini A, Alberti S, Salaris E, Theodore P, Floris I and Santa A (2021) Honey bees increase social distancing when facing the ectoparasite Varroa destructor. Science Advances DOI: 10.1126/sciadv.abj1398