Large animals travel more slowly because they can’t keep cool

Elephants have to spend a lot of time cooling down their muscles, which lowers their speed. Image: Bernd Adam - Whether an animal is flying, running or swimming, its traveling speed is limited by how effectively it sheds the excess heat generated by its muscles, according to a new study led by Alexander Dyer from the German Centre for Integrative Biodiversity Research (iDiv) and the Friedrich Schiller University Jena, published now in the open access journal "PLOS Biology". An animal's capacity to travel is a crucial part of its survival and dictates where - and how far - it can migrate, find food and mates, and spread into new territories. This becomes even more challenging in a human-dominated world characterized by increasingly fragmented habitats and limited food and water resources under climate change. Relationship between animal size and traveling speed. Alexander Dyer and his colleagues developed a model to look at the relationship between animal size and traveling speed, using data from 532 species. While larger animals should be able to travel faster due to their longer wings, legs or tails, the researchers found it is particularly the medium-sized animals that typically have the fastest sustained speeds.