 In the US, it is sometimes the practice to have some fox cubs chased but allowed to escape in order for them to learn evasion techniques and so that they can be tracked again in the future.Many foxes evade the hounds by running up or down streams, running along the tops of fences, and other tactics to throw the hounds off the scent.Once the season properly starts (usually from early November in the northern hemisphere, or May in the southern hemisphere), the idea is to drive the fox from the covert and pursue the scent that it leaves for long distances over open countryside.