The most obvious reason that makes researching animals more complex than humans is the number of species – one versus many. Karina Loyo of Prelude Dynamics discusses the various complications of animal studies, including regulatory complexities and the challenges in conducting research using animals. She identifies the main challenges as the following: the number of species, differences between species, handling of the experimental unit, housing challenges, access and observation window and obstacles, ability to communicate critical study details, and the need for experts to observe and evaluate.