Well into the 20th century coal miners used canaries to monitor levels of Carbon monoxide gas in the mine. Their measurement was very simple … when the canary fell off it’s perch, the miners had a very short time to evacuate the mine. When the miners suspected their might be major methane gas issues, they posted a guard to literally watch the canary. The good news was it worked for the miners … not so much for the canaries!
Researching the subject of animals as sentinels gives one a new perspective on the importance of our animal kingdom.
Animal sentinels, or sentinel species, are animals used to detect risks to humans by providing advanced warning of a danger. The terms primarily apply in the context of ecological hazards rather than those from other sources. Some animals can act as sentinels because they may be more susceptible, or have greater exposure to a particular hazard than humans in the same environment. People have long observed animals for signs of impending hazards or evidence of environmental threats. Plants, and other living organisms have also been used for these purposes.
Some historical examples:
In Minamata Bay, Japan, cats developed “dancing cat fever” before humans were affected, as a result of eating mercury contaminated fish. Dogs were recognized as early as 1939 to be more susceptible to tonsil cancer if they were kept in crowded urban environments. Similar studies did the same for animals exposed to tobacco smoke.
Some characteristics of the animals
Animal sentinels must have measurable responses to the hazard in question, whether that is due to the animal’s death, disappearance, or some other aspect.
For example, honey bees are susceptible to air pollution. Similarly both bats and swallows have been used to monitor pesticide contamination due to their diet of insects that may have been affected by the chemicals. By the same token, aquatic animals, or their direct predators, are used as sentinel species to monitor water pollution.
Some species may show effects of a contaminant before humans due to their size, their reproductive rate, or their increased exposure to the contaminant.
Today it is a common belief that cancers in dogs and cats have been linked to household exposures to pesticides, cigarette smoke, toxic cleaning agents and other carcinogens. Some speculate that animals could provide early warning of a terrorist attack using biological or chemical agents.
From a futuristic perspective there has been a call for linkage of human and veterinary medicine in a “One Health” approach that recognizes disease occurring in the animal kingdom may indicate human health risk. This approach would involve greater information sharing between human health, veterinary clinicians and public health professionals.
So, if you have made it to the end of this article … You now know why I like talking about Animals being guardians for our health.