There are not very many things that police do that ought to be handled by other agencies, but there are a few.
First of all, I would argue that animal control should not be a police duty. The police should not be in charge of rounding up stray dogs or telling the owners of loose dogs to keep them controlled. These are not things that require police skills and could be easily done by other people. This would free up police officers to do things that only they can actually do.
Second, I would say that police should not be in charge of enforcing truancy laws. Here again, there is no need for a trained police officer to be spending his or her time asking teens whether they should be in school. Surely school districts could have people who could do this without having to have all the training and equipment that police officers have.