Large animals move more slowly because heat management limits their pace
A growing body mass makes cooling the body a bigger challenge for large animals, which is a key reason their movement tends to be slower. This insight comes from a study published in PLOS One that explores how body size and structure shape travel speeds in the animal kingdom.
Whether an animal can travel far or fast is vital for survival. It influences where it can migrate, how it finds food, where it can locate mates, and the potential to establish new territories. Human civilization, with its expanding footprint and habitat fragmentation, has intensified these challenges for many species, making efficient movement more critical than ever.
Researchers led by Alexander Dyer built a mechanical model that simulates how energy flows through an animal’s body during movement. The team aimed to understand how different physical features of an animal—such as limb length, body shape, and thermal regulation—shape overall speed. To ground the model in real-world data, they collected detailed information on body structure and lifestyle for 532 species, ranging from small to large, and tested how these traits predict movement patterns across diverse taxa.
Their hypothesis suggested that larger animals could gain speed because longer wings, legs, or tails offer more efficient propulsion and leverage. Yet the data revealed a nuanced picture: medium-sized species typically achieve higher average speeds over long distances. The authors propose that this outcome reflects a balance between locomotor capacity and heat dissipation. When muscles work hard, heat builds up, and larger animals must allocate more time to shedding that heat, which slows sustained travel. In other words, the pace of movement can be explained by how well an animal converts energy into motion while keeping overheating in check. From a physics standpoint, the cooling efficiency tends to scale with skin area, while heat production scales with body mass, and this divergence helps account for why massive bodies do not always translate to the fastest travel over extended ranges. A simple analogy often cited is that the mass of a solid sphere increases more quickly than its surface area, which limits cooling for heavy objects as they move.
In related work, researchers have noted that moths possess tails that appear to function as lifelike lures or decoys for approaching bats, illustrating how even seemingly subtle traits can influence survival strategies. These findings underscore the broader idea that movement, energy use, and thermoregulation are tightly linked to an animal’s anatomy and ecological role, shaping how different species navigate their environments and respond to changing conditions on landscapes altered by human activity. Marked observations from the study emphasize the importance of integrating body design with environmental pressures when predicting migration, foraging, and mating dynamics across the animal world, and they invite further investigation into the ways heat management constrains performance across large-bodied lineages. (Attribution: study reported in PLOS One, summarized by researchers in comparative physiology and mechanical modeling.)