Foal Morphology: Here Come Those Legs!

We all know foals look like they’re "all legs," and new research is honing in on the physical and evolutionary advantages of that lanky morphology. It's all about keeping up with the herd, say the researchers, especially for migrations.

"The long legs of juvenile horses make them able to manage the lower speeds frequently necessary for migrating," said Bruno Grossi, PhD candidate in the department of ecological sciences at the University of Chile in Santiago and primary author of a recently published study on foal morphology. "Foals have longer legs than what you would see on an adult animal of the same weight (adult pony or goat). This disproportion gives them an efficient step which allows them to have longer strides without having to add the extra work of more steps to keep up."

Grossi likened the lower-speed steps of the foal to an "inverted pendulum" model, in which a mass has to be balanced above a pivoting point.

Surprisingly, however, this model does not apply with higher speeds, according to Grossi. "In the trot-to-gallop transition, for example, leg length had little importance," he said. "This is probably due to the fact that at these speeds, aerobic capacities and muscular power are more relevant."

Grossi and his team compared measurements between a group of foals and their dams, including speed at transitions, force (energy used) during those transitions, and the lengths of various parts of the body. While a foal’s body length and height were about 60 to 70% of that of its mother, leg lengths were very similar to adult measurements, he said. Canon bones and pasterns were essentially adult-sized by two months of age. However, foals had significantly less erect posture in the hind legs compared to adult horses.

"Our study shows that these morphological differences make it so that foals move in a manner that is dynamically different from the way adults move," Grossi said. "But it's an efficient way to keep them close to their mothers at migration speeds."

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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