Wildlife

Toxic Cities

On Sept. 9, 2019, a mountain lion was found dead in the Santa Monica Mountains. It was the fifth mountain lion to die from consuming rat poison in that region. Rodenticides aren’t the only health risks that urban wildlife face. Wildlife living in cities or suburban areas experience unique health challenges compared to their country cousins, often due to human activities.

A recent study found that overall, urban wildlife had poorer health than wildlife in more natural areas. This was mostly due to urban animals having more toxicants in their tissues. Toxicants are toxic substances artificially introduced into the environment by human activity and include pesticides, industrial pollutants and heavy metals.

Toxicants can potentially harm animals’ reproduction, development and survival. Exposure to heavy metals has been found to weaken the immune system of tree swallows, possibly making animals more susceptible to disease or less able to recover from infection.

Another study demonstrated that exposing amphibians to pesticides increased their susceptibility to infection with a parasitic worm. Amphibian populations are in decline globally, in part due to disease, and so it is important to understand how toxicants influence disease to conserve threatened populations.