Many people think of donkeys as hardy little equids that are typically easier to maintain than horses. If they have one weakness, however, it’s their lack of an insulating winter coat. Recent study results from the U.K. revealed that donkeys’ hair coats hardly change across the seasons, meaning they aren’t nearly as well-equipped to deal with cold weather as many people might believe.

“The initial idea (for the study) came from the Donkey Sanctuary,” noted researcher Britta Osthaus, PhD, senior lecturer at Canterbury Christ Church University. “This study is part of a larger project that also collected data on the use of shelters in correlation with temperature, wind, insect density, and precipitation.

“It is a saying amongst donkey owners that donkeys aren’t waterproof, but nobody had tested the hair properties in a systematic way,” she added.

The research team collected hair samples from 18 donkeys, 16 U.K.-native cold-blood horses and ponies, and eight mules (all of varied ages) during the months of June, September, December, and March, from 2015 to 2016. After drying samples, the researchers weighed and measured them for comparison