What is a primary indicator of rust coloration in rabbits?

Rust coloration in rabbits is primarily associated with fading due to sunlight exposure. When rabbits are frequently exposed to direct sunlight, their fur can lighten or develop a different hue, leading to a rust-like appearance. This discoloration is often a result of the degradation of pigments in their fur caused by UV radiation.

Other factors that can influence a rabbit's coloration, such as health problems, breeding issues, and improper feeding, do not specifically lead to rust coloration as prominently as the effects of sunlight. Health problems may cause changes in fur condition but do not directly correlate to rust coloration, while inability to breed or improper feeding affects overall well-being rather than specific color distortion. Thus, the impact of sunlight exposure on the fur's coloration is the most relevant factor when discussing the primary indicator of rust coloration in rabbits.