Animals Are More Sentient Than You Think

“Hello, how’re you doing?” This is what I often say to the small black teddy bear sitting on top of the pile of old letters by my London apartment’s front door. I know she cannot hear me or understand me—she is not a sentient being—but I say it anyway. Why? Because this constantly reminds me that it is up to me to treat all sentient beings with respect, even those who may not understand human language. I am an ethical vegan, you see. I follow a philosophy based on avoiding harming any sentient being, and to be true to it I need to pay close attention to everything I do, and how I treat everyone around me. 

What is sentience, anyway? This concept has been defined in many ways, and definitions change with culture. Some say that is the ability to feel “pain and pleasure,” others say is the ability to experience “suffering and happiness,” or “emotions and moods.” Some may not accept all animals feel pain or suffering, claiming they need a sophisticated level of cognition or consciousness—they argue some animals they consider “inferior,” such as worms and insects, are not sentient. I disagree with this anthropocentric view.  

When I was writing my book “Ethical Vegan: A Personal and Political Journey to Change the World,” I spent some time researching the issue of sentience, and I finally arrived at my own definition:

At its most basic meaning, sentience is the ability to experience positive and negative sensations, which requires two things: firstly, senses to perceive the sensations from stimuli coming from the environment, and, secondly, a nervous system to process such sensations and translate them into experiences which allow the animals to react accordingly, depending on whether they are negative or positive (i.e. fleeing from an adverse environment or moving towards a source of food or a mate). 

Sentient earthlings

Concepts such as “feelings” are subjective, and therefore available only to the animal experiencing them, and we could never prove any organism (including a human) is sentient if we based it only on that. Fortunately, we do not need to know exactly what animals are feeling, but only whether they are experiencing something positive or negative, and the behavior of the animals can tell us that. Animals are sentient because they can behave in a way that means they can profit from the information sentience provide them. They can move away from something bad and get closer to something good. They can swallow something tasty and spit out something nasty. 

They can feel, experience, and judge, and once they have judged, they can behave accordingly. We don’t need to know exactly how they feel, what they experience, or how they reason. We only need to observe how they behave. This is how we know most animals are sentient, and that rocks, plants, and teddy bears are not. I am an ethologist (a zoologist specialized in animal behavior), and I have never seen any animal other than poriferans (aquatic sponges) behaving in such a way that suggests a lack of sentience. 

Once life evolved the ability to move and become independent from photosynthesis, sentience inevitably evolved with it. Feeling pain is a particularly useful tool for avoiding injury and death, and the animal species whose members did not feel pain most likely became extinct. Equally, feeling comfort, pleasure, and even delight when finding maternal protection or succeeding in mating courtship will increase the chances of reaching a reproductive age—and once there, reproduce—which natural selection would favor. In fact, on planet Earth, with liquid water, a dynamic atmosphere, solid ground, and moving soil, sentience is likely to evolve independently all over the place. When you can dive to catch your dinner, fly to avoid winter, bask on a rock to catch the sun, or dig a hole to hide from predators, sentience is what you need. It makes sense, right?     

It should be a no-brainer, but it is not. In a world where animal exploitation is heavily entrenched in most aspects of all human societies, commercial and cultural forces constantly work to deny the quality of sentience to non-human animals. Even when today’s science clearly shows most animals are sentient, this denial is mainstream. Although all jurisdictions in developed countries accept all mammals and birds are sentient, and most also include the rest of the vertebrates (reptiles, amphibians, and fish), as far as invertebrates are concerned—who make up the majority of animals on this planet—there is much resistance. 

However, in the last few years, there has been some progress. In various pioneering countries (such as New Zealand, Norway, Switzerland, Canada, and EU nations), some invertebrates are beginning to be accepted as sentient, and therefore are becoming legally protected like their vertebrate counterparts. In particular, cephalopods (a type of mollusk which includes octopus, cuttlefish, and squid) and decapods (a type of crustacean which includes crabs and lobsters).

What about the tiny animals?

With time, I hope more invertebrates will make it to the official list of protected sentient beings. Having studied social wasps for many years—who taught me many things about life and started me on my journey to veganism—I do not doubt that insects and arachnids are sentient too. Not an unexpected conclusion from a vegan zoologist, you may think. However, what is surprising is that within the “vegan” world—with its non-speciesist philosophy which predicates no animal species should be discriminated against—some people often referred to as ostrovegans eat bivalves (aquatic animals such as mussels, oysters, and clams characterized by having two shells that can close the animal in) because they don’t consider them sentient. In my book I explain why I think they are wrong:

First of all, they are mollusks, and other mollusks have now been recognized as sentient beings. Second, they all have senses. In particular, all have mechanoreceptors (touch) and chemoreceptors (taste). They also have statocysts which help them to sense and correct their orientation, and light-sensitive cells that can detect a shadow (some have actual eyes, such as scallops, who have more complex eyes with a lens, a two-layered retina, and a concave mirror). Third, they do have a nervous system, which consists of a nerve network and a series of paired ganglia (they don’t have a central nervous system but we know this doesn’t matter if they still have enough interconnected neurons spread in different parts of the body). Fourth, research has found endogenous morphine (a natural analgesic) in specific bivalve tissues appears to be involved in the response to physical trauma. Fifth, they react to negative experiences appropriately.

[…] Finally, we have the issue of mobility […] They do move, actually. Sometimes very slowly (as adult marine mussels can attach and detach byssal threads to attain a better position in the subtract), sometimes at mid-speed (as freshwater mussels have a muscular ‘foot’ that helps them burrow and move small distances), sometimes quite fast (as sea scallops swimming away from immediate danger), sometimes in their larva stages (as in marine mussels where the round microscopic larva drifts for three weeks to six months, before settling on a hard surface), sometimes they move parts of their bodies, which has the same effect of fleeing from a bad situation (such as closing their ‘valves’ to no longer be ‘out there’), as in oysters and others.

I know all the animal figurines and stuffed toys I own are not sentient, but casually greeting them reminds me I should ensure I don’t deprive any sentient being I encounter of the respect they deserve, even if they look very different to me, or they hardly move. I also politely greet each aphid and caterpillar I meet on the plants of my small veganic garden when I carefully inspect them before I take the portion of my food share.

I always imagine they greet me back, and that makes me feel good.