Typically invasive alien species are bad. Known to cause many species declines and in turn extinctions, they overwhelm or out complete local species. Unfortunately man’s best friend, the domesticated dog, is an alien to many parts of the world. And as our best friends, we have taken them around the globe with us. Consequently, dogs are a significant cause for species declines and extinctions around the globe, having become the third most significant invasive alien mammalian predator. However, often they are overlooked and not considered as a serious threat to wildlife.
Please read: Why wolves became domesticated dogs.
An article by the BBC discussed 5 impacts that domestic dogs have on wildlife around the world. Here we are going to discuss 4 of them:
- Competition for prey
- Disturbing the ecosystem
- Transmission of diseases
In Chile, pumas are significant predators of the small Pudu. One of the worlds smallest deer. Now a study suggests dog predation as a significant factor behind the decline of Pudu. Here in Europe we do not have Pudu, but we have livestock. However, wolves continually take the blame for killing sheep. Nevertheless between 2008-2016, no sheep or goats were killed by wolves in Austria. In 2017, a total 17 goats or sheep were killed. Despite this, around 10,00 animals were lost to inclement weather in Austria. Yet dogs are overlooked, according to the All Parliamentary Group on Animal Welfare (APGAW) in Britain 15,000 sheep were killed by dogs in 2016 while 280 were killed in Poland. Moreover, 40% of the attacks in Britain are attributed to have been killed by straying or unaccompanied dogs according to the National Sheep Association.
In the same regard, feral dogs compete with other predators for prey items; such as with Gray wolves in Poland. Further, in Southern Chile, where the greatest concentration of pumas in were 0.06 km2, feral dog densities were as high as 7.3 per km2. Therefore, they are likely competing for prey.
Disturbing the ecosystem
Predator species evoke behavioural responses in prey species. For example, prey species spend more time being vigilant and watching for predators, or hiding, reducing parental care, spending less time resting etc. Further, American Lynx (or Bobcat) have been shown to avoid trails and avoid areas where dogs are more active. Meanwhile, the European Lynx is greatly disturbed when dogs enter their dens. in order to feed off of the lynx’s stashed food.
Contrasted, a single German Shepherd dog disturbed the ecosystem in New Zealand by killing 13 radio tracked kiwi’s out of a total of 23. An additional, conservative estimate states 500 or more birds might have been lost.
Transmission of diseases
Additionally diseases can transfer from dogs to wildlife. For instance, some dogs are carriers of canine distemper virus (CDV). A tragic example of this was in 1994, when the Serengeti lion population contracted morbillivirus, which is a relative of CDV. Believed to transmit from dogs to hyenas and subsequently to lions. The disease claimed the lives of approximately 30% of the lion population.
The effects and what can be done
The Global Invasive Species Database states that domestic dogs threaten a total of 191 IUCN Red List species. However dealing with this threat is a challenge. Proposed solutions include shooting or poisoning feral dogs to control their populations. Additional suggestions are spaying and neutering feral dogs in combination with vaccinations which would limit numbers and ensure a healthy population. These suggestions range from unethical to costly. However it is also important to consider the health of the wildlife that is affected by feral dogs.