Honeybees use social distancing to protect themselves against parasites

Credit: Pixabay/CC0 public domain
A new study reveals that honeybees can increase social distancing in situations where their hive is threatened by a parasite. It was conducted by an international team of researchers from UCL and University of Sassari (Italy).

Science Advances published a study that showed honeybee colonies can respond to an infestation by a harmful mite. The study modified the space and interactions between nestmates to increase social distance between the young and the old bees.

Dr. Alessandro Cini, UCL Center for Biodiversity & Environment Research and UCL Biosciences was co-author. He stated: "Here we provide the first evidence that honeybees alter their social interactions as well as how they move about their hive in reaction to a common parasite.

Honeybees are social animals. They benefit from sharing responsibilities and interactions like mutual grooming. However, when these social activities can increase infection risk, the honeybees seem to have evolved to balance both the benefits and risks by adopting social distancing.

Examples of social distancing in animals have been discovered in many species that are separated by millions of generations of evolution. These include baboons who are less likely than others to clean individuals with gastrointestinal problems to ants with pathogenic fungus infections that force them to live in the suburbs.

Trophallaxis (feeding) and honeybee allogrooming behavior (upper right). Credit: University of Sassari, Dr Michelina Pusceddu

New research examined whether Varroa destructor, an ectoparasite mite that lives in honeybee colonies, caused changes in social organization which could decrease the spread of this parasite. Varroa mite is a major stress factor that can affect honeybees. It causes many harmful effects on the bees at both the individual and colony levels, including virus transmission.

Honeybee colonies are divided into two main compartments. The outer compartment is occupied by foragers and the inner compartment is occupied by nurses, queen, and brood. This spatial segregation within a colony allows for fewer interactions between the two compartments than within each one. It also protects the most important individuals (queens, young bees, and brood), from the external environment and prevents them from contracting diseases.

Researchers compared colonies infested with the Varroa mite to determine which colony was more likely to have mites. The researchers also discovered that grooming behaviors were more concentrated in the central part of the hive. According to the researchers, it seems that foragers (older bees), move towards the nest's periphery while younger nurse and groomer bees move towards the center. This is in response to an infestation.

Michelina Pusceddu, Dipartimento di Agraria University of Sassari, was the lead author. She stated: "The observed rise in social distancing among the two groups of honeybees within the parasite-infested colonies represents a surprising aspect of how honeybees evolved to combat pathogens.

"Their ability adapt their social structure to reduce contact between people in the face of a disease threat allows for them to maximize social interaction and minimize the risk of contracting infectious diseases when necessary.

"Honeybee colonies are a great model to study social distancing, and to fully understand the effectiveness and value of this behavior."

Learn more Hygienic honeybees are less likely to be attacked by destructive parasites

Michelina Pusceddu and colleagues, Honey bees increase social distance when faced with the ectoparasite Varroa destroyor, Science Advances (2021). www.science.org/doi/10.1126/sciadv.abj1398 Journal information: Science Advances Michelina Pusceddu et al, Honey bees increase social distancing when facing the ectoparasite Varroa destructor,(2021). DOI: 10.1126/sciadv.abj1398