Thermal landscapes reorganize movement through behavioural-state transitions in an endangered ungulate
This study demonstrates that thermal landscapes reshape the movement of endangered hirola antelope through predictable, nonlinear transitions among distinct behavioral states—specifically a shift toward resting above a 33°C threshold—rather than a uniform suppression of activity, offering a mechanistic framework for predicting wildlife responses to climate change and guiding conservation strategies.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
The way animals move across the land is one of the most fundamental forces shaping their survival. It determines where they find food, how they avoid predators, and crucially, how they cope with the weather. For large herbivores living in hot, dry places, the daily struggle is a balancing act between the need to eat and the need to stay cool. As the planet warms, scientists are increasingly concerned about how these animals will adapt. Do they simply move less when it gets hot, or do they change the very way they behave? Understanding this is vital for conservation, because if we do not know how a species reacts to heat, we cannot protect it effectively in a changing climate.
In the semi-arid rangelands of north-eastern Kenya, a team of researchers set out to answer these questions by studying the hirola, the world's most endangered antelope. With only about 500 individuals remaining, every detail of their life matters. The scientists fitted seven female hirola with GPS collars that recorded their location every hour for several years. By analyzing over 134,000 of these location points, they could see not just where the animals went, but what they were actually doing at any given moment. They used a statistical method that sorts movement patterns into distinct categories, allowing them to distinguish between an animal that is resting, one that is grazing, and one that is traveling. This approach revealed that the hirola do not simply slow down when the temperature rises; they reorganize their entire day.
The study identified four clear states of movement. The animals spent roughly 38 percent of their time foraging, 33 percent moving slowly in a directed way, 28 percent resting, and a tiny fraction, less than 1 percent, moving very fast. What the researchers found most striking was how heat reshaped these habits. As the ground temperature rose, the hirola did not stop moving entirely. Instead, they made a sharp, predictable switch. When the land surface temperature reached approximately 33 degrees Celsius, the animals stopped traveling and began to rest much more often. However, the time they spent eating remained remarkably stable. Even as the heat intensified, the hirola protected their feeding time, cutting back on travel instead. This suggests a sophisticated strategy where the animals prioritize finding food while minimizing the energy spent on moving through the heat.
This shift is not a gradual slowing down but a distinct threshold. Below 33 degrees, the animals continue to travel, but once that temperature is crossed, their behavior changes abruptly. The researchers observed that during the hottest part of the year, the hirola reduced their travel significantly while keeping their foraging effort steady. This indicates that the animals are not just passively suffering from the heat; they are actively managing their time budgets to survive. They shift their movement to cooler parts of the day and rest during the peak heat, ensuring they still get enough to eat without overheating.
The study also looked at whether individual animals had their own unique styles. The answer was yes. Some hirola consistently spent more time traveling than others, and these differences remained stable across different seasons. One particular animal, which had the largest home range of the group, was also the one that spent the most time traveling. This suggests that individual personality or strategy plays a real role in how these animals navigate their world. Furthermore, the researchers found that hirola that lived close together tended to move in sync. A bonded pair of females was found to be in the same behavioral state—whether resting, eating, or traveling—at the same time far more often than would happen by chance. This coordination was strongest when resources were scarce, suggesting that sticking together helps them track food and water more effectively.
These findings offer a new way to look at how climate change affects wildlife. Rather than assuming that animals will simply become less active as the world gets hotter, this research shows they will likely change the structure of their day. They will trade travel time for rest, but they will fight to keep their feeding time. For the hirola, and other endangered species in similar environments, this means that conservation efforts must focus on protecting the specific times and places where they can feed without overheating. Identifying these thermal limits helps scientists predict where these animals can survive in the future and how to plan for their safe relocation if their current habitats become too hot. The study provides a clear, measurable framework for understanding these complex decisions, moving beyond simple observations of activity to a deeper understanding of how animals think and behave under pressure.
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