Of course mice (mammals) are vertebrates...., as they have vertebrae (bones). In contrast with arthropods (insects, spiders etc), for example, which are invertebrates, as they don't have vertebrae (specifically arthropods have exoskeleton instead). Check the examples of vertebrate and invertebrate animals given on the page of the following link: https://www.animalwised.com/examples-of-vertebrate-and-invertebrate-animals-39.html