How to check if a game object has stopped moving

StuckSheepCheck.cs

using UnityEngine;
using System.Collections;

public class StuckSheepCheck : MonoBehaviour {

	public GameObject Sheep;
	public GameObject SheepTwo;
	private Rigidbody2D SheepRigidbody2D;
	private Rigidbody2D SheepTwoRigidbody2D;

	void Start() {
		this.SheepRigidbody2D = Sheep.GetComponent<Rigidbody2D>();
		this.SheepTwoRigidbody2D = SheepTwo.GetComponent<Rigidbody2D>();
	}

	void FixedUpdate () {
		this.CheckIfSheepIsStuck();
	}

	private void CheckIfSheepIsStuck() {
		if(this.SheepRigidbody2D.IsSleeping() && this.SheepTwoRigidbody2D.IsSleeping()) {
			SheepGameEnder.Instance.EndGame();
		}
	}
}