What can cause serious damage to a trained raptor's leg scales?

The correct choice highlights the importance of properly fitting equipment for a trained raptor. Excessive bating, which refers to the bird's flapping and tugging at its restraints, can lead to injury or damage to the leg scales if the jesses are not properly adjusted. Ill-fitting jesses can cause friction, leading to abrasions or sores on the raptor's legs. This emphasizes the necessity for falconers to regularly check and ensure that the jesses fit securely but comfortably to prevent any unnecessary stress or injuries to the bird.

The other options, while they can impact a raptor's overall health, do not specifically address the damage to leg scales that poorly fitted jesses can cause. Overexertion might lead to fatigue or injury elsewhere, an insufficient diet could affect the bird's health and performance in other areas, and cold temperatures might influence behavior or even health issues, but none of these are as directly connected to the physical damage of leg scales as the issue of jesses and bating.