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No Dogs! Why Not?

The impacts of dogs on wildlife and water quality: A literature review

Compiled by Lori Hennings for the Portland, Oregon Metro Parks District, April 2016


Any human related activity can disturb wildlife. In order to meet The Nature Institute’s dual goals of protecting natural resources and providing access to nature, TNI has tried to strategically locate trails in less sensitive habitat and to ensure that human activity is as non-disruptive as possible. Part of that strategy has been to allow public access, while limiting certain activities such as bringing dogs into natural areas.

The evidence that dogs negatively impact wildlife is overwhelming. It is clear that people with dogs – on leash or off – are much more detrimental to wildlife than people without dogs. Dogs (Canis lupus familiaris) are considered to be a subspecies of wolves (Canis lupus), and wildlife perceive dogs as predators. (30)  Impacts include:

  1. Physical and temporal displacement – The presence of dogs causes wildlife to move away, temporarily or permanently reducing the amount of available habitat in which to feed, breed and rest. Animals become less active during the day to avoid dog interactions. Furthermore, the scent of dogs repels wildlife and the effects remain after the dogs are gone.
  2. Disturbance and stress response – Animals are alarmed and cease their routine activities. This increases the amount of energy they use, while simultaneously reducing their opportunities to feed. Repeated stress causes long-term impacts on wildlife including reduced reproduction and growth, suppressed immune system and increased vulnerability to disease and parasites.
  3. Indirect and direct mortality – Dogs transmit diseases (such as canine distemper and rabies) to and from wildlife. Loose dogs kill wildlife.
  4. Human disease and water quality impacts – Dog waste pollutes water and transmits harmful parasites and diseases to people.


Click here to read the full literature review.