Wild vampire bats tend to practise social distancing when they are sick, as per a new study published in ‘Behavioural Ecology’. The study investigated how sickness behaviour reduces individual connectedness in a ‘high-resolution dynamic social network’. This type of social distancing does not ask for cooperation from others and is said to be common among the species.
For the field experiment, 31 adult female bats from a roost inside a hollow tree were captured and injected with a substance that gave them bacterial symptoms. Also, other bats were given ‘saline injections’ and put in a control group. It was then concluded that a control bat had a 35 per cent chance of associating with a sick bat and a 49 per cent chance of associating with a healthy one. The study said, “The ‘sick’ bats showed a clear decrease in social connectedness (degree, strength, and eigenvector centrality). Bats in the control group encountered fewer ‘sick’ bats and also spent less time near them. These effects varied by time of day and declined over 48 hours. High-resolution proximity data allow researchers to define network connections based on how a pathogen spreads”.
The sensors weighed 1.5g and were glued to ‘dorsal fur using skin-bonding latex adhesive’. A ‘proximity index’ was defined for the per cent quantile of all RSSI values. ‘85 per cent’ was used to define ‘association’. The study says, ‘ We chose this value by using the same RSSI value as a previous study linking wild associations to captive interactions (?27 dBm). Past work suggests these associations involve proximity of about 0-50 cm’.
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