Dr. Pokras is a veterinarian but he isn't like most other veterinarians; he specializes in taking care of wild animals. Most of the animals he treats were found and brought into his clinic by the public. Mark says that really loving animals is a critical part to doing his job. But if you really want to accomplish great things in taking care of animals or preserving animal populations it takes a reasonable amount of technical training as well. This means math and science. For instance, Mark often tries to determine if a particular animal species has a viable population in one certain location. A viable population means there are enough animals to perpetuate the species. However, it takes math to determine a viable population. The variables are things such as the size of the land involved, the number of males and females and the age distribution of both. You need to know the reproductive age for that species, as in how old they have to be before they can reproduce. Then you need to factor in the gestation period, or how long it takes for the female to have a baby and how long is that baby dependent on its mother. Another variable is how often can the female reproduce and how many young does she have when she reproduces? "Looking at all this mathematically is a nice straight forward way of approaching the problem and understanding what you need to do to control things," says Mark.