In the Aspen Parkland ecoregion, deer and other large ungulates are a hazard to traffic, resulting in potential animal or human deaths, especially in the autumn mating months or when deer are searching for feeding grounds in the spring. The defence mechanism of deer in the face of a threat is to freeze. There are over 3,500 deer–auto collisions per year in Saskatchewan. A number of measures have been implemented to increase awareness such as fencing, feeding programs, automobile whistles. Deer mirrors along the edges of highways were installed for reducing deer-vehicle collisions. The Wildlife Warning System is triggered by highway vehicles, setting off lights, sounds and or odours ahead of the approaching vehicle to frighten away animals. A system that detects vehicle was installed in 2002 near Harris to reduce the quantity of mule deer–automobile accidents for a two-year testing period. Another system detects large animals and sets off a warning system to drivers of vehicles, alerting them that an animal is on or near the highway ahead of time.