Grumpy tortoise? Reptiles can experience mood swings too

For decades, reptiles – including tortoises – have lingered in the background of animal sentience discussions. Popular imagination often casts them as simple, instinct-driven beings – unfeeling and unaware.

Unlike mammals and birds, they rarely show overt emotion, leading many to dismiss the idea that reptiles might feel in complex ways.

But a new study from the University of Lincoln has disrupted that belief, offering compelling evidence that red-footed tortoises (Chelonoidis carbonaria) can experience long-term mood states.

Published in the journal Animal Cognition, the study reveals that tortoises can show optimism and pessimism depending on their environment. These emotional states then shapes their response to the world around them.

The implications are profound. If tortoises can feel mood shifts similar to mammals and birds, we must rethink how they are treated in captivity and reconsider their place in the story of animal consciousness.

What moods mean in animals

Mood and emotion are not the same. Emotions are short-lived responses to immediate situations, like fear when chased or joy at finding food. Moods, on the other hand, linger.

They form a kind of emotional background noise, influencing how an animal perceives new experiences. Scientists call these “free-floating” states, unattached to specific triggers but powerful in shaping behavior.

In humans and other mammals, we have tested mood using cognitive bias tasks. These tests explore how an individual interprets ambiguous situations.

Someone in a good mood will expect a positive outcome, while someone in a bad mood will expect the worst. Until now, no study had used this method on reptiles.

That gap has finally been closed. Researchers at Lincoln tested 15 red-footed tortoises to determine if they could exhibit mood-driven bias. Their approach was clear and controlled, building on established methods from mammal studies.

Tortoises respond to uncertainty

Each tortoise was trained in a simple spatial judgment task. A bowl placed in one spot always contained a food reward (rocket leaves).

The same bowl, placed elsewhere, never had food. Once trained, tortoises were presented with the bowl at three new, in-between locations: one near the positive spot, one in the middle, and one near the negative.

How quickly a tortoise approached the bowl at each of these ambiguous points showed its expectation. Quick approach meant optimism. Hesitation meant doubt or pessimism.

Every trial was carefully timed, filmed, and structured to avoid smell-based cues or random behavior. The test was fair.

Interestingly, the tortoises judged the near-positive and middle spots more optimistically. They moved faster toward these bowls, showing an “optimistic skew” similar to that seen in mammals and birds. This alone is a strong sign of mood in action.

Anxiety measured in action

To confirm that mood shaped behavior beyond just one task, the tortoises were also subjected to two classic anxiety tests: the novel object test and the novel environment test.

These are used widely in animal cognition to assess emotional reactions to unfamiliar situations.

In the novel object test, each tortoise encountered an unusual item, a colorful bead coaster, inside a familiar arena.

The researchers recorded how long it took the tortoise to approach the object, how far it extended its head, and how quickly it began to move. Confident, relaxed tortoises moved sooner and extended their heads farther.

Tortoise mood affects behavior

The novel environment test changed the tortoises’ surroundings. Different textures, colors, and patterns created a new sensory world.

Again, tortoises were watched for how they responded to unfamiliarity. The researchers noted that tortoises who showed optimistic bias in the earlier task also behaved with more confidence in these settings.

For example, tortoises that approached ambiguous bowls faster also reached new objects more quickly.

Some even extended their heads farther in strange environments, indicating comfort and curiosity. These behavioral links show a deep connection between mood and action.

Rethinking reptile feelings

The authors of the study interpret these results as remarkable. The presence of a mood state in a tortoise means that reptiles do not simply react. They evaluate, anticipate, and feel. That changes the ethical landscape.

“Animal welfare concerns are reliant upon evidence that a given species has the capacity to experience affective states,” said Anna Wilkinson, a professor of Animal Cognition at the University of Lincoln.

“With reptiles becoming increasingly common as pets, it is essential for us to study their moods and emotions to try to understand how captivity may impact them.”

Professor Oliver Burman noted that the research represents a significant shift in our understanding of what reptiles can experience, with important implications for how we care for these animals in captivity and interact with them in the wild.

The researchers emphasized that these findings align reptiles more closely with mammals and birds in terms of emotional capacity.

While reptiles may lack certain emotional expressions seen in other animals, they still experience shifts in affective state. Their moods impact how they explore, respond, and behave.

Tortoise mood and the roots of emotions

Reptiles diverged from mammals and birds hundreds of millions of years ago. That makes this discovery even more significant. If a tortoise, members of one of the oldest lineages of land animals, can experience mood, then the evolutionary roots of emotion run deeper than we thought.

The study references earlier research that found reptiles do show some emotional behavior, such as emotional fever and response to enrichment.

But until now, no one had shown that they could experience long-lasting, mood-like states. These new results argue against the idea that reptiles have a narrow emotional spectrum.

They suggest that affective states, both emotional and mood-based, might be ancient features of vertebrate brains. These are not recent innovations. This insight matters for biology, psychology, and ethics.

Reptiles need more than basics

The researchers argue for major changes in how we house and care for reptiles. Current enclosures often focus on physical health and basic habitat needs.

But if tortoises have moods, then their emotional well-being must also be addressed. That means offering larger enclosures, complex terrain, opportunities for exploration, and mental stimulation.

According to the researchers, we should assume that they are not only capable of suffering but also experiencing enduring positive moods. Captive reptiles deserve spaces that support both.

The research also expands the toolkit for welfare assessments. Behavioral and mood-based testing can help zookeepers, researchers, and pet owners recognize when a reptile like a tortoise is distressed or thriving.

Rethinking how we see tortoises

For too long, tortoises have been treated as slow-moving curiosities. But this new evidence invites us to see them differently. They can be optimistic, feel anxiety, and might even experience contentment.

This is not just about red-footed tortoises. It is about revising our relationship with all reptiles. The cold-blooded no longer seem cold-hearted. They are thinking, feeling beings. And now we have the science to prove it.

The study is published in the journal Animal Cognition.

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