What can be a function of shelter for ponies in the field?

Shelter plays a critical role in protecting ponies from a variety of environmental factors, and one of its important functions is indeed to shield them from flies. Flies can be a significant source of discomfort and stress for ponies, potentially leading to health issues such as skin irritations, infections, or reduced overall well-being. Providing a shelter can offer a refuge from flying insects, allowing ponies to rest and seek relief from pestering pests.

In contrast, while prevent boredom and providing visibility are beneficial aspects of an environment for ponies, they are not direct functions of shelter. Access to better grass is also not a primary function of shelter; instead, it pertains more to pasture quality and accessibility rather than the role of the structure itself. Therefore, the primary focus of shelter in this context is its protective capacity against flies and other environmental stressors.