Before 1983 we didn’t even know bees sleep. However, from that time onwards literature on this matter kept on growing more and more. Thanks to the efforts of many researchers, we now know a good deal about bees’ sleep.
The way bees sleep does not differ from the way many mammals and birds do. When bees sleep their muscles lose tone, their reaction to stimuli is slower and less energetic, their body temperature lowers and they move less. Also, they prefer sleeping in dark environments. All these facts lead scientists to a conclusion; it is most probable that bees have an internal circadian rhythm of about 24 hours following the alternating of day and night.
But why do bees sleep? Research has shown how sleep in bees not only links to energy preserving, but also to proper body functioning. Waggle dance is one such function. Bees perform it whenever they want to communicate the location of a given food source to their nestmates. Bees use this dance to communicate two things; direction and distance. Lack of sleep affects information’s accuracy about the direction in which to find the food source. Bees follow gravity to orientate themselves in the process, forming an angle while dancing. Researchers suggest this task is more demanding for bees. If they did not sleep well, bees will be far less accurate. Information about distance is not influenced by sleep deprivation, so researchers concluded this second task is less demanding.
Sleep deprivation affects memory as well. Researchers noted how sleep-deprived bees find it more difficult to consolidate navigation memory, so it is less likely for sleepy bees to remember which route they took during their last journey out of the hive.
Most of the scientific community agrees on the fact that bees are subjected to a variety of stress factors such as pesticides, lack of quality food and parasites. Stress can result in a less functioning immune system, making bees more susceptible to other stress factors as well. Stressed bees live a shorter life, which means the colony population may shrink, and it is not easy for a colony to recover from that.
Could it be that migratory beekeeping is damaging for bees’ health? The US is famous for this phenomenon. In order to take advantage of the many crops growing at different times of the year in different places, more than a million hives is moved across the country many times a year. Studies have shown how changing hives’ location can lead to a greater loss of colonies’ population – some of them live a shorter life, others drift away from the hive.
Many beekeepers reported an increase in nosema infections as well as greater oxidative stress in their colonies after moving the hives. Nevertheless, links between these phenomena and migratory beekeeping is yet to be fully proven, meaning there is still (more than one) room for research in this field.