undefined reference to vtable, even though virtual function was indeed implemented

Question

It is probably a sily mistake... I started to code using C++ language. I have created an abstract class:

class Animal{
    protected:
        string name;
        int age;
        string noise;
        string scientific_name;

    public:

        Animal(){

            cout<<"teste"<<endl;
        }

        virtual void setScientificName();

        string getName(){
          return name;
        }



        int getAge(){
            return this->age;
        }
        //virtual int getAge();


        string getScientificName(){
            return scientific_name;
        };

};

Derivated it into to other classes:

class Dog: public Animal{




    public:

        Dog():Animal(){
            setScientificName();
        }

        void setScientificName() override {
            scientific_name = "Canis Lupus Familiaris";
        }
};

class Cat: public Animal{


    public:
        Cat():Animal(){
            setScientificName();
        }

        void setScientificName() override {
            scientific_name = "Felis catus";
        }
};

Tested it:

int main()
{
    Cat c;

    cout << "Hello world! " << c.getScientificName() << endl;
    system("Pause");
    return 0;
}

Even though I have implemented the virtual function, I´ve got the error:

||=== Build: Debug in teste (compiler: GNU GCC Compiler) ===| obj\Debug\main.o||In function ZN6AnimalC2Ev':| C:\Users\study\Código em C\teste\main.cpp|15|undefined reference to vtable for Animal'| obj\Debug\main.o||In function ZN6AnimalD2Ev':| C:\Users\study\Código em C\teste\main.cpp|6|undefined reference to vtable for Animal'| ||error: ld returned 1 exit status| ||=== Build failed: 3 error(s), 0 warning(s) (0 minute(s), 2 second(s)) ===|

Why?