Mutató esetében miért nem működik az operator++?

//main.cpp

# include <iostream> //std::cout,std::cin,std::cin.get,std::endl;

# include <string> //std::string;

# include <cstring> //strlen

# include <stdlib.h> //# define EXIT_SUCCESS 0;

# include <algorithm> //std::sort;

# include <windows.h> //Sleep(1000),exit(0)

typedef unsigned short ushort;

typedef unsigned int uint;

using std::cout;

using std::cin;

using std::endl;

using std::string;

using std::sort;

enum BREED {HASKI,TERRIER,PINCSI};

class Mammal

{

public:

Mammal();

Mammal(ushort age,ushort weight);

Mammal(const Mammal &rhs);

virtual ~Mammal();

const Mammal operator++(int) {++itsWeight;return *this;}

virtual void Speak()const {cout <<"Mammal beszel \n";}

virtual Mammal* Clone()const {return new Mammal(*this);}

void Sleep()const {cout <<"Mammal alszik \n";}

void SetAge(ushort age) {itsAge = age;}

void SetWeight(ushort weight) {itsWeight = weight;}

ushort GetAge()const {return itsAge;}

ushort GetWeight()const {return itsWeight;}

protected:

ushort itsAge;

ushort itsWeight;

private:

};

class Dog: public Mammal

{

public:

Dog();

Dog(ushort age,ushort weight,BREED breed);

Dog(const Dog &rhs);

~Dog();

virtual Mammal* Clone()const {return new Dog(*this);}

void Speak()const {cout <<"Dog beszel \n";}

void Sleep()const {cout <<"Dog alszik \n";}

void SetBreed(BREED breed) {itsBreed = breed;}

BREED GetBreed()const {return itsBreed;}

protected:

private:

BREED itsBreed;

};

Mammal::Mammal():

itsAge(2),

itsWeight(6)

{cout <<"Mammal Konstruktor \n";}

Mammal::Mammal(ushort age,ushort weight):

itsAge(age),

itsWeight(weight)

{cout <<"Mammal ushort,ushort Konstruktor \n";}

Mammal::Mammal(const Mammal &rhs):

itsAge(rhs.GetAge())

{cout <<"Mammal copy konstruktor \n";}

Mammal::~Mammal()

{cout <<"Mammal Destruktor \n";}

Dog::Dog():

Mammal()

{cout <<"Dog Konstruktor \n";}

Dog::Dog(ushort age,ushort weight,BREED breed):

Mammal(age,weight),

itsBreed(breed)

{cout <<"Dog ushort,ushort,BREED Konstruktor \n";}

Dog::Dog(const Dog &rhs):

Mammal(rhs)

{cout <<"Dog copy konstruktor \n";}

Dog::~Dog()

{cout <<"Dog Destruktor \n";}

//main

int main()

{

Mammal *pMammal = new Dog;

pMammal->Clone();

pMammal++; //Futási hiba!

delete pMammal;

return EXIT_SUCCESS;

}