Sentinel species are , often animals, used to detect risks to humans by providing advance warning of a danger. The terms primarily apply in the context of environmental 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.
Historical examples
Many observations of animals point to toxicity in food, water or air that would or could harm humans.
Canaries
The classic example is the "
domestic canary in the
Coal mining". The idea of placing a
Warm-blooded in a mine to detect
carbon monoxide was first proposed by John Scott Haldane in 1895,
and canaries were used as early as 1896.
Countries such as Britain, the United States, and Canada used canaries as a sentinel species.
Well into the 20th century, coal miners brought canaries into coal mines as an early-warning signal for toxic gases, primarily carbon monoxide.
The birds, being more sensitive, would become sick before the miners, who would then have a chance to escape or put on protective
respirators. In some cases, the canaries were kept in cages with dedicated
Oxygen tank so the birds could survive after their illness provided a warning.
"Canary in the coal mine" is now used as an idiom for a person or thing that warns people of danger.
Cats
In
Minamata Bay, Japan,
Domestic cat developed "
Minamata disease" before humans were affected due to eating mercury-contaminated fish.
Dogs
Dogs were recognized as early as 1939 to be more susceptible to tonsil cancer if they were kept in crowded urban environments.
Studies similarly found higher disease rates in animals exposed to
tobacco smoke.
Poultry
Yushō disease was discovered when poultry began dying at alarming rates due to polychlorinated biphenyl (PCB) poisoning, although not before approximately 14,000 people were affected.
Roses
Rose bushes are often planted at the ends of vine rows in
Vineyard. One hypothesized reason is that roses are highly susceptible to
powdery mildew, which can also afflict
Grapevines. Finding mildew on the roses is therefore sometimes taken as an early warning sign to take preventive measures to protect the adjacent vines. However the effectiveness of this practice is debated, since roses and vines are affected by different species of mildew (although both species occur under similar weather conditions).
Mussels
In Poznań, Poland, where eight
Mussel equipped with sensors are used to ensure the safety of the city's
drinking water. These mussels act as
Bioindicator, meaning they provide a reliable estimation of water toxicity by responding to changes in water quality.
Characteristics
Animal sentinels must have measurable responses to the hazard in question, whether that is due to the animal's death, disappearance, or some other determinable aspect.
Many of these species are ideally unendangered and easy to handle. It is important that the species' range overlap with the range being studied.
Often the ideal species is determined by the characteristics of the hazard.
For example, are susceptible to air 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.[Arthur D. Bloom, Frederick de Serres, Ecotoxicity and Human Health: A Biological Approach to Environmental Remediation, CRC Press: 1995, , page 76.]
Specific applications
Toxic gases
Canaries were iconically used in
coal mines to detect the presence of
carbon monoxide. The bird's rapid breathing rate, small size, and high metabolism, compared to the miners, led birds in dangerous mines to succumb before the miners, thereby giving the miners time to take action.
Air and water pollution
A number of animals have been used to measure varying kinds of air pollution. These include
for air pollution,
bivalve molluscs for online water-quality survey and
for atmospheric lead.
Bats and swallows have been used to monitor pesticide contamination due to their diet of insects that may have been affected by the chemicals.
Aquatic DDT pollution has been quantitatively measured in California fish. PCB has been measured through the analysis of fish livers.
Scientists also monitor crayfish in the wild in natural bodies of water to study the levels of pollutants there.
The Protivin brewery in the Czech Republic uses crayfish outfitted with sensors to detect any changes in their bodies or pulse activity in order to monitor the purity of the water used in their product. The creatures are kept in a fish tank that is fed with the same local natural source water used in their brewing. If three or more of the crayfish have changes to their pulses, employees know there is a change in the water and examine the parameters.
Infectious diseases
The discovery of West Nile virus in the Western Hemisphere was heralded by an outbreak of disease in crows and other wild birds. Other emerging diseases have demonstrated linkages between animal health events and human risk, including
monkeypox,
SARS, and
avian influenza. In outbreaks of bubonic plague, rats begin dying out before humans.
Household toxins
may provide early warning of
lead poisoning hazards in a
home, and certain cancers in dogs and
have been linked to household exposures to
,
cigarette smoke, and other
carcinogens.
Cultural references
-
Kurt Vonnegut in an interview compared the function of artists in human society to coal-mine canaries; see Wikiquote.
[Interview "Physicist, Purge Thyself" in the Chicago Tribune Magazine (22 June 1969)]
-
"Canary in a Coalmine" is the title of a non-single track on The Police's 1980 album Zenyatta Mondatta.
-
"Canary in a Coalmine" is the title of a non-single track on The Crane Wives' 2012 album The Fool in Her Wedding Gown
-
American professional baseball league Charleston Dirty Birds are named for canaries in coal mines.
See also
Further reading
External links
