How do we know that animals without tails are happy?

As a specialist in pet behavior, especially dogs and cats, I often get the question of how people can tell if an animal is happy if it has no tail to wag. My answer is that the tail serves a communicative purpose in all animals, but not only that. Many also use it to keep their balance. That is to say, it’s related to the biomechanics of their bodies and it helps them move around.

The first thing we should ask ourselves is why some animals that normally should have a tail, don’t. There could be several reasons. It could be congenital, meaning it was born without one due to a genetic defect. It could also be due to deliberate genetic selection, meaning breeders have created a tailless breed, such as French bulldogs or Boston terriers, and even some cat breeds. Another reason could be amputation due to a medical problem or for cosmetic reasons. It is important to know that the latter is illegal and very harmful for the animal’s well-being.

And how does not having a tail affect these animals? If it’s not due to amputation, which can cause chronic pain throughout their lives, it affects their balance, although they may compensate in other ways and live completely normal lives. But the main impact is on communication. That is why it’s very important to understand that both dogs and cats don’t communicate only with their tails; they have other ways of letting us know the emotions they’re feeling. So, in animals that don’t have tails, we must pay attention to those other forms of communication.

These include facial expressions, body posture and vocalization. To tell if a tailless animal is happy, you should look at its facial expression and body posture. But this shouldn’t be limited to animals without tails. It is reductionist to think that when dogs wag their tail they’re happy, and when they have it between their legs, they’re scared. Any emotion the animal is feeling will display a combination of different signals. For example, a dog may yawn because it’s stretching, but also because a child is approaching it and it feels uncomfortable. To understand an animal, you have to observe these other forms of communication and also pay attention to the context in which it finds itself.

To know if a tailless dog is happy, you should look at its rear end. When a dog with a tail is happy, it wags it in a relaxed, loose motion. However, if there’s no tail, the rear end will move all the same, usually accompanied by a move toward the person or other animal it’s interacting with. You can also observe its facial expression: if it’s happy, its mouth will be half-open, its breathing will be calm, its ears won’t be flattened but will have a natural posture, and its face will be relaxed. Some dogs also emit low-intensity (not high-pitched) barks and howls.

And then there are specific play postures. For example, a kind of bow with the front limbs extended, the chest touching the ground, and the hind limbs raised is very common. All of this is a reflection of joy.

As for cats, sometimes we extrapolate what we know about dogs and believe that if they move their tail from side to side, it indicates a positive emotional state, but what that tail movement really shows us is a totally opposite emotion: nervousness, restlessness and discomfort.

To tell if a cat is happy, you should observe whether its body posture is relaxed and whether it emits happy meows, which are usually short and high-pitched. Happy cats often come close and rub against the legs of a person or other animal. They may also flop to the ground and expose their belly. This isn’t necessarily an invitation to be petted; it’s more their way of letting you know they’re comfortable with you. The same thing happens when they purr, showing joy, or when they curl up to rest on you; it means they’re comfortable and happy, not afraid.

This article is part of a weekly science advice column called Nosotras respondemos, sponsored by the program L’Oréal-Unesco ‘For Women in Science’ and by Bristol Myers Squibb.