vector<unique_ptr<Animal>> zoo;
zoo.emplace_back(new Elephant);
zoo.emplace_back(new Zebra);
zoo.emplace_back(new Bear);
cout << "Feading time (f) or Bedtime (b)?";
char c;
cin >> c;
void (Animal::*ap) () = c == 'f' ? &Animal::eat : &Animal::sleep;

for (auto it = zoo.begin(); it != zoo.end(); it++) {
  ((**it).*ap)(); // can't use '->' with unique ptrs
}