I've had a male Russian for about 9 years and recently acquired a female. After making sure that she was healthy, I attempted to introduce them together in the same outdoor pen (about 8'x 8'). The male is very agresssive, nipping at the female and chasing her around the pen. I'm not sure if this is mating behavior or if he's being agressive and is a threat to harm her. Any information is greatly appreciated.