Insects can feel pain, according to mounting evidence – here’s what it means for animal welfare laws

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At least a trillion insects are killed each year for food and feed. Routine slaughter methods include extreme heat and cold, often preceded by starvation. In comparison, “only” about 79 billion mammals and birds are slaughtered each year.

Researchers have long recognized that the survival value of pain means that many animals experience it, supposedly with the exception of insects. But we looked at over 300 scientific studies and found evidence that at least some insects do feel pain. Other insects, meanwhile, have not yet been studied in sufficient detail.

We also conducted our own study of bumblebee response to potentially noxious stimuli. The way they reacted to stimuli was similar to pain responses in humans and other animals that we accept to feel pain.

Pesticides kill trillions more wild insects each year. The actual cause of death is often paralysis, asphyxiation or dissolution of internal organs, sometimes over several days.

If insects feel pain, insect breeding and pest control would cause massive suffering. Yet animal welfare debates and laws almost universally ignore insects. One reason is that historically insects were often considered too simple with too short a lifespan. But the evidence that insects feel pain is mounting.

The question of whether insects feel pain is difficult to answer. Pain is an inherently private experience. The difficulty of diagnosing pain when the being in question cannot speak is illustrated by the relatively recent treatment of babies during surgery.

As recently as the 1980s, many surgeons thought babies couldn’t feel pain and rarely used anesthetics because they thought babies’ obvious responses, like screaming and writhing, were just “reflexes”. Although we still don’t have proof that babies feel pain, most now accept that they do with near certainty.

For any being who cannot directly communicate their suffering, we must rely on common sense and probability. The more pain indicators found, the higher the probability. It is important to use consistent criteria for all animals and to look for the same behavioral indicators of pain in insects that one would use in a companion cow or dog.

pain in the brain

Most animals exhibit “nociception” – the processing of noxious stimuli that can lead to reflex-like responses. Scientists have long known that insects exhibit nociception. However, if an animal detects potentially damaging stimuli, this is not necessarily an indicator of “ouch” pain, which in humans is generated in the brain. Nociception and pain can occur, to some extent, independently of each other.

In a recent study, we discovered that bumblebee responses to heat depend on other motivations. We gave the bumblebees four feeders: two heated and two unheated. Each feeder dispensed sugar water, which the bumblebees love.

When each feeder had the same concentration of sugar water, bees avoided both heated feeders. But when heated feeders dispensed sweeter sugar water than unheated feeders, bumblebees often chose heated feeders. Their love of sugar outweighed their hatred of heat. This suggests that bees feel pain because (like humans) their responses are more than just reflexes.

Bumblebee insect on an apricot flower

The bees also remembered heated and unheated feeders, and they used this memory to decide which one to feed on. So the compromise happened in the brain.

Insect brains alter their behavioral responses to harm in other ways. For example, hungry flies are less likely to fly away from extreme heat than satiated flies. Decapitated flies can still jump but they do not show this difference, demonstrating their brain’s involvement in heat avoidance. Communication between the brain and the sensitive part of the body is also compatible with pain.

Other Pain Indicators

The framework we used to assess the evidence for pain in different insects is the one that recently led the UK government to recognize pain in two other major invertebrate groups, the decapod crustaceans (including crabs, lobsters and prawns) and cephalopods (including octopus and squid), including them in the Animal Welfare (Sentience) Act 2022. The framework has eight criteria, which assess whether an animal’s nervous system can withstand pain (like brain-body communication) and whether his behavior indicates pain (like motivational trading). off).

Flies and cockroaches meet six of the criteria. According to the framework, this amounts to “strong evidence” of pain. Despite weaker evidence in other insects, many still show “substantial evidence” of pain. Bees, wasps and ants meet four criteria, while butterflies, moths, crickets and grasshoppers meet three.

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Beetles, the largest group of insects, meet only two criteria. But, like other insects that received low scores, there are very few studies of beetles in this context. We found no evidence of an insect not meeting all the criteria.

Our findings are important because the evidence for pain in insects is roughly equivalent to the evidence for pain in other animals that are already protected by UK law. Octopuses, for example, show very strong evidence of pain (seven criteria).

In response, the UK government included both octopuses and crabs in the Animal Welfare (Sentience) Act 2022, legally recognizing their ability to suffer.

The UK government has set a precedent: strong evidence of pain warrants legal protection. At least some insects meet this standard, so now is the time to protect them. For starters, we recommend including insects under the Animal Welfare (Sentience) Act 2022, which would legally recognize their ability to sense pain. But this law only requires the government to consider their welfare when drafting future legislation.

If we want to regulate practices such as agriculture and scientific research, the government must extend existing laws. For example, the Animal Welfare Act 2006, which makes it an offense to cause “unnecessary suffering” to animals covered by the act. This can lead to insect farms, like conventional farms, minimizing animal suffering and using humane slaughter methods.

The Animals (Scientific Procedures) Act 1986 regulates the use of protected animals in any experimental or scientific procedure which may cause pain, suffering, distress or lasting harm to the animal. Protecting insects under this law, as octopuses already are, would regulate insect research, reduce the number of insects tested, and ensure that experiments have a strong scientific rationale.

Finally, pesticides are a huge welfare issue for wild insects. We recommend developing more humane pesticides that kill insects faster and minimize their suffering.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The conversation

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Matilda Gibbons receives funding from Queen Mary University of London.

Andrew Crump receives funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program, Grant Number 851145. He is affiliated with the Animal Welfare Research Network, the Association for the Study of Animal Behavior and the Universities Federation for Animal Welfare.

Lars Chittka receives funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program, Grant Number 851145.

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