Thread: no default constructor error

I get the error:

error C2512: 'Mouse' : no appropriate default constructor available
Error executing cl.exe.

in the following code, and I can't figure out why the class Mouse default constructor is called:

Code:

#include <iostream>
using namespace std;

class Mouse
{
public:
     Mouse(int n)
	 {
		 length = n;
	 }	
	 
	 void Display()
	 {
		 cout<<length<<endl;
	 }

	 int GetLength()
	 {
		 return length;
	 }
	 
private:
     int length;
};

class Cat
{
public:
	Cat(Mouse m)//********ERROR
	{
		member1 = m;
	}
	

	void Display()
	{
		cout<<member1.GetLength()<<endl;
	}

private: 
	Mouse member1; 
};

int main()
{
	Mouse my_Mouse(3);

	Cat my_Cat(my_Mouse);

	my_Cat.Display();

	
    return 0;
}

If I add a default constructor to class Mouse, then it works fine. When is the default constructor called?