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|The examples and perspective in this article deal primarily with North America and do not represent a worldwide view of the subject. (December 2010)|
A deer-vehicle collision occurs when one or more deer and a human-operated vehicle collide on a roadway. It can result in deer fatality, property damage, and human injury and/or death.
In 2000, of the 6.1 million lightweight motor vehicle collisions reported in the US, 1 million involved animal-vehicle collisions. Deer–vehicle collisions lead to about 200 human deaths and $1.1 billion in property damage every year. State and federal governments, insurance companies, and drivers spend an addition $3 billion in an effort to reduce and manage the increasing number of deer-vehicle collisions. The term “deer-vehicle collision” is commonly annotated throughout safety agencies as DVC.
Deer–vehicle collisions have occurred since roadways have been built in close and direct proximity to direct habitat, also known as deer habitat fragmentation. White-tailed deer, the most common deer involved in deer-vehicle collisions, have steadily increased in numbers since the turn of the 20th century. Currently, it is estimated that 20 to 30 million deer populate North America. The actual number of animals killed in deer-vehicle collisions is not known because no such database exists. In 1981 study, it was concluded that “large animals,” which included deer, accounted for 26% of animals killed each year in collisions with vehicles on interstates and country roads.
The expansion and technological advances of roadways in the US have increased the number of deer-vehicle collisions. The increased amount of habitat fragmentation, due to expanding technology, has increased the likelihood of a deer-vehicle collision.
In the United States, the state with the highest number of deer-vehicle collisions is Pennsylvania, with an estimated 115,000 collisions in 2013 causing $400 million in damage. West Virginia is the state with the highest risk that a motorist will hit a deer while driving.
The main contributing factor of a deer-vehicle collision has been contested among studies and statistics. Many factors are yet to be identified or understood. At this point, a main factor in all deer-vehicle collisions has not been concluded, but the most argued is the proximity of roadways to deer-populated forestry. Significant factors also include: urban population and deer density. Also, studies have shown that, nationally, most deer vehicle collisions occur between May and November because of deer mating season and foraging before the winter months.
Habitat fragmentation occurs when human technology encroaches upon the natural habitats of animals. As human beings live in closer proximity to animals they are more likely to encounter one another. The most common type of habitat fragmentation across the United States is roadways and highways in forests and other deer-inhabited areas. Because highways are isolated points of fragmentation, deer wander about them freely because they see little to stay away from. Roadways and highways located in sparsely-populated areas are usually built along rives and lakes of mountains and plains. These areas attract deer because they render safe havens and excellent foraging. Roadways and highways within densely populated deer habitat lead to more prevalent deer-vehicle collisions.
A contributing factor to deer-vehicle collisions, as preventable as it is prevalent, is the time of day at which motorists travel through deer habitation. During the daytime, motorists can more easily see and avoid hitting deer. At night, most especially during the dusk and dawn hours, deer are much harder to see, and therefore easier to hit.
The most important but largely overlooked contributing factor to deer - vehicle collisions is the reduction of populations of top predators. One of the most significant effects of the large predators is the control of populations of large herbivores, such as white tailed deer. It has been estimated that deer populations in Eurasia and North America are six times lower in areas with wolf than in areas without wolf. Since wolf and puma´s populations have been extirpated or reduced from most of the USA populations of deer have become superabundant. More than 100 lives and millions of dollars in property damage will be saved in the USA alone just by being more tolerant to these animals.
The US Government does not sanction any specific manufacturer that may reduce or monitor deer-vehicle collisions. The investigation and implication of deer-vehicle collision prevention methods remains a responsibility of state governments. Such products are usually heavily tested and studied before being endorsed by them. State organizations such as the departments of transportation or game and fisheries usually handle the investigation of deer-vehicle collision prevention methods and products. State wildlife agencies have much concern for the preservation of deer and other wildlife that become involved in vehicle collisions due to roadway expansion and development.
The deer whistle is the most widely studied and scrutinized form of deer-vehicle collision prevention method. Deer whistles are products that attach to a vehicle and act as an alarm system for deer and other wildlife. The manufacturing of deer whistle products has emerged into a multimillion-dollar industry.  Their manufacturers advertise that ultrasound, which they say deer can hear but humans cannot is emitted as air passes through the whistle. Most deer whistles are about 2 inches long and are bullet shaped. They cost between $20 and $25 and are designed to be attached to the bumper of a vehicle. When a vehicle moves faster than 35 mph, a whistle sound is induced which is believed to ward off animals from a roadway. The deer whistle is marketed to prevent deer-vehicle collisions. The effectiveness of deer whistles is disputed among agencies because of the conflicting reports available. The study and documentation of deer whistles is generally poor, and a conclusive decision about the effectiveness of the deer whistle cannot be made.
Some research has been published about the function and capability of deer whistles. Deer have an auditory range of two to six kilohertz (kHz), but only a select few deer whistle products have ranges within that of a deer’s. Some manufacturers claim that deer can hear the whistle up to a quarter-mile away, but no research has solidified that claim. Another point of concern is that the amount of noise from a vehicle may compromise the clarity of the deer whistle. Because the whistle is vehicle-mounted there is little that can be done about mitigating vehicle noise. Others also argue the whistle’s location on the vehicle as being susceptible to dirt and insects which would eventually clog the passageway of the whistle, rendering it useless. The idea of a non-air-activated whistle has been discussed but little research has been done on the effectiveness of such products, and is highly recommended. Deer whistles generally have a questionable level of effectiveness but are advertised as aiding in the prevention of DVCs. A concern amongst studies is the impact the whistle has on the psyche of the driver, and the driver’s sense of security.