Although many national park visitors enjoy the companionship of their dog pets when on vacation, dogs are not a beneficial addition to natural ecosystems such as those found in Joshua Tree National Park.
While dogs, when accompanied by their owners, are allowed in the park, their activities are restricted by the Code of Federal Regulations:
Pets must be restrained on a leash that does not exceed six feet in length, or otherwise be physically confined at all times.
Leaving a pet unattended and tied to an object is prohibited.
Following are some of the experiences, studies, and rationales that have led to the National Park Service restrictions on dogs in Joshua Tree National Park:
Free ranging dogs are a serious threat to wildlife in Joshua Tree National Park. During 2002, free ranging dogs from adjacent communities attacked and killed bighorn sheep. Occaisionally, a desert tortoise, a federally listed threatened species, is found to have been chewed on by dogs. In a report on wildlife conditions in national parks in 1935, Wright and Thompson recommended that dogs not be brought into national parks or "at the very least" be kept on leash (1935, G. M. Wright and B. H. Thompson, Fauna of the National Parks of the United States, National Park Service, Department of Interior, Government Printing Office, Washington, DC). Leashed Dogs and Wildlife
Even leashed dogs have the potential for substantial negative effects on wildlife. Dogs are members of the family, Canidae, that includes wolves, coyotes, and foxes.
Along with the family Felidae (lions, bobcats), Canidae species are first order predators and as such exert stress upon prey species. Prey animals are acutely aware of the presence of hunting canids. They become more alert and often take escape measures - running, freezing, burrowing, climbing, flying, or hiding - when they sense hunting canids near by. A wild animal may become used to the presence of a human or horse, but will always react to a leashed dog entering its territory as if it were a wild canid. Permitting dogs, even leashed dogs, onto trails is the same as introducing a large number of surrogate predators into the ecosystem. There are seasons and times of drought, limited forage, post-rut, extreme temperatures, pregnancy, lactation, or new-born when wildlife are at energy levels so marginal any disturbance that causes extra stress and uses precious energy will make the difference between life and death. It is a general tenet in the science of natural resource management that unnecessary stress to wildlife be reduced or eliminated in order to give animals an increased margin of survival.
The National Park Service has addressed this issue by prohibiting visitors from chasing or harassing wildlife and by not allowing dogs on trails. R. A. McArthur et al. (1982 and see C. Sime 1999) conducted human disturbance trials in which a person approached a group of bighorn sheep: alone from a road, from the road accompanied by a leashed dog, and from a ridge away from the road. The strongest reaction (milling, fleeing) occurred when the sheep saw a human with a leashed dog. There was no evidence of habituation in repeated trials. McArthur et al. (1982) concluded, "The presence of dogs on sheep range should be discouraged."
In land management areas where dogs are allowed on trails, hunters will take their dogs into a protected area on leash, giving the impression of legally walking their dogs, then unleash them to chase wildlife out of the preserve into a firing line of hunters waiting outside the boundary. State and Federal law enforcement officers, including the National Park Service is aware of this illegal activity on public lands.
Should a female bear with cubs encounter a dog, leashed or not, the chances are very high that she will attack the dog and the owner to protect her cubs. This issue has been documented in the study "Bear Attack" by Dr. Steve Herrero of Canada. Dogs and Horses
Leashed dogs encountering horses on narrow trails have been known to bark and lunge causing the horses to stampede, risking injury to themselves and their riders. Horses are used as pack animals and for transportation by park visitors, concessionaires, and by Park Service employees. The National Park Service believes that the risks of human and horse injury are far too great to allow even leashed dogs to mix with horses.
Some people do not like to encounter a dog, even a leashed dog (P. T. Corkery, San Francisco Examiner, March 28, 2003). Some non-dog owners are made uncomfortable, even frightened, when a strange dog comes close, barks, or shows aggression. Since dog owners consider close contact with their dog to be a pleasant experience, they may think that everyone enjoys this too and not be sensitive to the experience of other park visitors. (Chester, 2003).
Public lands managers have found that even where dogs on leash are permitted on trails, owners often allow their dogs to run free. In a survey conducted at Angeles National Forest, where dogs are allowed on trails as long as they are on a leash, 90 percent of the dogs observed on trails were off leash (Chester, 2003).
Dog feces has a high nitrogen content and can negatively affect soils, watersheds, and plants; it is unsightly and negatively affects the experience of park visitors. Yet, dog owners frequently ignore requirements to scoop up after their pets. Patrick Murphy counted 1,492 piles of dog feces on a single trail (Sanitas Valley Trail) in Boulder, Colorado in one month, despite a city ordinance requiring dog owners to pick up after their pets (Chester, 2003).
Dogs can transmit a number of pathogens to humans and wildlife via feces, through blood-sucking insects, or directly to other species. Toxocaria can cause blindness in children. Parvovirus affects other canines, and was the source for wolf-pup mortality in Glacier National Park in the early 1990s. Muscle cysts ( Sarcocystis spp. ) affects ungulates such as deer and bighorn sheep. Leptospirosis is a bacterial disease that affects the kidneys and urinary tract of most mammal species. Parasites, such as ticks, keds, tapeworms, and fleas are well-known problems in dogs that can be passed to other animals, including humans. (Chester 2003).
Carolyn A. Sime, Montana Chapter of the Wildlife Society, "Domestic Dogs in Wildlife Habitats" Chapter 8, September, 1999.
Tom Chester "Effects of Dogs on Wildlife, 2003.