While it is clear that vertebrates can feel pain, whether this holds for invertebrates too has been a matter of fierce debate in the scientific community. Now, a research team led by Queen Mary University of London has discovered that bumblebees are not only intelligent and innovative creatures, but may also be capable of experiencing pain. These findings suggest that bumblebees – and perhaps many other species of insects – should be included in animal welfare laws.
Previous studies have found that bumblebees are highly intelligent insects, able to do simple mathematics, understand the concept of zero, and distinguish among human – and probably bee – faces. Moreover, they show optimism when successfully foraging, and can become depressed if they are momentarily trapped by a spider. Thus, they are clearly capable of experiencing emotional states.
To discover whether these emotions include pain, the scientists looked at one of the criteria most commonly used to define pain in animals: “motivational trade-offs.” For instance, humans will endure a significant amount of pain at the dentist for the longer-term benefits of having healthy teeth, and hermit crabs will leave preferred shells to escape an electric shock only if the jolt is particularly high.
In order to assess whether bumblebees are capable of similar behaviors, the researchers gave them a choice between two high-quality feeders containing a 40 percent sugar solution, and two feeders with low percentages of sucrose. The feeders were placed on top of individual heating pads, which were initially all turned off. In such a situation, all the bees preferred the feeders containing the most sugar.
When the pads beneath the high sucrose feeders were warmed up to 55°C – a temperature high enough to cause discomfort, but not as high as to cause significant injuries – the bees were still choosing these feeders in order to get more sugar. However, when both the hot and the cool feeders contained high-sugar solutions, the insects always avoided the hot ones. “This is the first direct demonstration that arthropods can also do trade-offs,” said Jonathan Birch, an expert in Animal Sentience at the London School of Economics who was not involved in the study.
However, it still remains unclear whether bees really feel what we call pain. Nevertheless, given that insects represent at least 60 percent of all animals, this possibility should not be ignored. “There is still anthropocentrism in Western science that rejects the idea of caring about ‘dumb invertebrates.’ Papers like this one will gradually chip away at this self-centered attitude,” concluded Jennifer Mather, a zoologist at the University of Lethbridge.
The study is published in the journal Proceedings of the National Academy of Sciences.