In psychology and basic medical science, many studies have been performed with experiments on animals such as rats and mice, to clarify mechanisms of mental disorders. With this aim, several "mental disorder model" rats and mice have been developed by genetic manipulation, giving psychotropic drugs, injuring their brain or breeding under special conditions. "Social interaction test" is one of the experimental protocols to evaluate their appropriateness. However, this test is not popular because of lack of reproducibility. Thus, we consider the robotic agent that interacts with a rat/mouse in the social interaction test provides new opportunities to perform it under more strict conditions. We have then developed a quadruped animaroid, WR-1. WR-1 has four 3-DOF legs, 2-DOF waist and 1-DOF neck. WR-1 walks with both crawl and trot gait. WR-1 also reproduces rearing and head shake behavior. Size of WR-1 is larger and motion performance lower than those of a mature rat. However, in a social interaction test with a rat and WR-1, some social interactions were observed between them.