Optimistic tortoises are bolder — Long-term mood states identified in red-footed tortoises

At a glance
Paper published: July 8, 2025 · Animal Cognition 28(1):52
Research institutions: University of Lincoln, UK
Subject: 15 red-footed tortoises ( Chelonoidis carbonaria)
Researchers: Tom Hoehfurtner, Anna Wilkinson, Sophie A. Moszuti, Oliver H. P. Burman
Key findings: Individuals kept in better housing conditions interpreted ambiguous situations optimistically, and these optimistic individuals also displayed fewer anxious behaviors when faced with unfamiliar objects.

What happened?

The notion that “reptiles lack emotions” is a long-standing belief among keepers. In July 2025, a research team from the University of Lincoln, UK, Animal Cognition A study presented findings that directly contradict this common belief. Conducted on 15 red-footed tortoises, the study provided evidence that tortoises, like mammals and birds, can experience a sustained ‘mood state’ that goes beyond momentary reactions.

The study was led by Professor Anna Wilkinson, an animal cognition researcher, and Professor Oliver Burman, an animal behavior and welfare researcher. A photo of ‘Geoff,’ one of the red-footed tortoises featured in the experiment, was released alongside the study findings and garnered significant attention.

Research Methodology — What is a ‘cognitive judgment bias task’?

The tool employed by the research team is the ‘cognitive judgment bias task,’ originally used in studies on human depression and anxiety. The principle is simple: it applies the same logic found in humans—where optimists tend to interpret ambiguous situations positively and pessimists negatively—to animals.

In the experiment, the tortoises were first trained to approach two specific locations: a ‘positive’ location offering a food reward and a ‘negative’ location offering no reward. Subsequently, the research team introduced several ambiguous intermediate locations between the two. By measuring how quickly the tortoises approached these ambiguous locations, the researchers assessed whether the individuals viewed the situation optimistically or pessimistically. Additionally, they conducted separate tests for anxious behavior, measuring the speed of the tortoises’ reactions to unfamiliar objects and environments, as well as the extent to which they extended their necks.

Key Results

The results revealed two main findings. First, individuals kept in relatively better housing conditions (regarding space, hiding spots, temperature gradients, etc.) approached the ambiguous location more quickly—indicating an optimistic outlook. Second, individuals demonstrating such optimism also showed shorter hesitation times and fewer anxiety-like behaviors when placed in novel object or novel environment scenarios. In other words, the results of the cognitive bias test aligned with those of the separate anxiety-like behavior tests. This suggests the existence of a relatively consistent individual disposition—or ‘mood state’—rather than merely a reaction to a specific moment.

Why is this important?

For a long time, reptiles were viewed as animals that merely react reflexively without experiencing sustained emotional states. This perception is partly why welfare standards for reptiles have been far more lenient than those for mammals and birds. Professor Wilkinson stated, “Understanding whether animals can experience moods is essential for establishing appropriate welfare standards.” Given that the UK’s Animal Welfare (Sentience) Act 2022 officially recognizes the potential for animals to experience emotions, research like this—which provides empirical evidence for specific animal groups—has direct implications for law and policy.

There are also practical implications for keepers. The study reported a correlation between the quality of the captive environment and an individual animal’s tendency toward optimistic or pessimistic judgment. In other words, environmental conditions—such as the availability of hiding spots, activity space, and temperature gradients—can influence not only physical health but also how the animal perceives the world. As the keeping of reptiles as pets becomes more common, this finding could shift the conversation on husbandry environments beyond the bare minimum of simply ensuring animals eat and grow.

Limitations and Differences from Existing Knowledge

The study involved a sample of 15 tortoises—a size too small to generalize findings to the entire species. While a correlation was observed, this does not prove a direct causal link where the captive environment ’causes’ a specific mood state; other variables, such as an individual’s genetic predisposition or past experiences, may also play a role. Furthermore, additional verification is required to determine whether these results apply to reptile species other than the red-footed tortoise. Nevertheless, given the scarcity of prior research using behavioral indicators to substantiate sustained mood states in reptiles, this study is significant for offering a concrete counter-argument to the prevailing assumption that reptiles lack emotions.

Points for Keepers to Note

This study does not endorse specific brands of feed or enclosures. However, it is worth noting that providing basic environmental conditions—such as hiding spots, activity areas, and temperature gradients—can influence an individual’s behavior and decision-making tendencies, going beyond the mere goal of keeping the animal alive. Husbandry Guides The practical takeaway from this study is the importance of checking species-specific temperature, humidity, and environmental requirements—such as those found on herp.blog—and designing enclosures that offer genuine opportunities for exploration and hiding, rather than just meeting minimum standards.

“Key Points

• A research team from the University of Lincoln conducted both cognitive bias and anxiety-related behavior tests on 15 red-footed tortoises.
• Individuals kept in better environments made more optimistic judgments, and those optimistic individuals exhibited fewer anxiety-related behaviors.
• This provides behavioral evidence that reptiles can experience sustained “mood states” that go beyond momentary reactions.
• Limitations include the small sample size (15 individuals) and the fact that the findings indicate a correlation rather than proving causation.
• This adds to the evidence that the quality of the captive environment can impact an individual’s welfare and behavior.

Related Documents

• Husbandry Guide — Species-specific temperature, humidity, and environmental conditions
• Reptile Wiki — Ecology, distribution, and behavior by species
• Reptile News
• Health management through reptile weight tracking

Sources and References

• Hoehfurtner, T., Wilkinson, A., Moszuti, S.A., Burman, O.H.P. (2025). Evidence of mood states in reptiles. Animal Cognition 28(1): 52. DOI: 10.1007/s10071-025-01973-y.
• University of Lincoln (2025-07-08). New study shows tortoises experience feelings similar to our own (Press release).

Date Details: Paper/Press Release Published July 8, 2025 · Article Reviewed August 2026 “On the 25th.