What are hollow guard hairs?

Hollow guard hairs are specialized types of fur found in some mammals, characterized by their tubular structure that creates an air-filled cavity. This design enhances insulation by trapping air, providing better thermal regulation and buoyancy in aquatic species. Hollow guard hairs also contribute to the overall texture and appearance of the animal's coat, often making it more water-resistant and durable. Examples can be found in animals like polar bears and some seals.