Final answer:
The #1 potential complication when restraining gerbils is fur slip, which is a defense mechanism caused by improper handling or stress. Handlers need to use proper techniques to prevent it and be aware of other handling issues such as tail slip, nail slip, and the risk of overheating.
Step-by-step explanation:
The #1 potential complication when restraining gerbils is fur slip. This condition occurs when a gerbil is handled improperly or feels threatened, leading it to release large patches of fur to escape predation or capture. It's a defense mechanism that can be quite stressful for the gerbil. It's important for handlers to be gentle and knowledgeable about proper restraint techniques to avoid causing fur slip, as this might also lead to skin injuries or infections.
In addition to knowing how to properly handle a gerbil to prevent fur slip, understanding the other options helps to ensure comprehensive care. Even though tail slip and nail slip are not as common, they're potential issues that can occur with improper handling.