Impacts of Pesticides on Mammals

Mammals can be directly exposed to pesticides, but are most commonly affected indirectly, through groundwater contamination and runoff, or through secondary poisonings such as ingesting prey that has been exposed to pesticides.

  • In 2014, a mountain lion in California was found to be experiencing mange (parasitic mites) as a result of pesticide poisoning due to rodenticides moving up the food chain.
  • In 2012, the U.S. Fish and Wildlife Service (FWS) announced a proposal to list the fisher (part of the weasel family) as threatened under the Endangered Species Act (ESA) due to the impact of rodenticides used in illegal marijuana operations. 
  • Neurotoxicology and Teratology published a study on the neurobehavioral toxicology of pyrethroid insecticides in 2008. Researchers found that decreased motor skills and coordination, slow response rates, and startle responses to noise are other possible effects of pesticide exposure in mammals.
  • Atlantic Bottlenose Dolphins
    Atlantic Bottlenose Dolphins. Photo by Pete Markham
    Research summarizing toxicological data on the effects of the organochlorine pesticides DDT, and its metabolites, found that these organochlorine compounds can impair female fertility by altering ovarian development and function in mammals.
  • Banned in 1972 for its toxic and deadly effects, DDT still persists in the environment and impacts wildlife. Levels of DDT remain dangerously high in some species of marine mammals, such as the short beaked common dolphin, killer whale, and common bottlenose dolphin
  • Evidence, published in Human and Ecological Risk Assessment, has shown that aquatic mammals exposed to general levels of DDT and other, newer pesticides, have impacted reproductive, immune and endocrine function.

Economic Cost

Mammals provide many ecosystem services. Some mammals provide food, clothing, and other materials that are used by humans. They provide the opportunity for recreational activities, such as zoos, horseback riding, hunting or animal watching. Other mammals, such as the cow, are revered and worshiped in certain communities for their religious affiliation. All mammals are responsible for ecologic biodiversity in some way, whether it be large or small. For example: bears eat berries and then travel, excreting the berries farther away, which gives plants the ability to spread and grow where they otherwise could not.

Pesticides can and do negatively impact mammals and the ecosystem services they provide, but the full economic impact can be difficult to define. The services listed above may not have a direct price associated with them, but it can be assumed that the impacts of pesticides on mammals cause some economic burden due to loss of ecosystem services. One can assume that prices will climb as mammal populations decline while the demand for the services they provide remains constant. If domesticated mammals that humans depend on for food decline due to pesticide exposure, society would experience an increase in the price of food. Similarly, if there is a drop in the number of mammals that provide biological diversity, ecological stability could easily be threatened, which in turn would affect human life.

Litigation & Lawsuits

Indiana bat
Indiana bat. Photo by USFWSmidwest. 

In 2015, EPA was sued for violating the Endangered Species Act (ESA). The lawsuit documents EPA’s failure to consult with the U.S. Fish and Wildlife Service (FWS) regarding the impact of the herbicide on two endangered species: the Indiana bat (and the whooping crane). A motion was filed against EPA after the decision was made to expand the use of Enlist Duo to nine additional states.

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