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Guano is the excrement (feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

 and urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

) of seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...

s, cave dwelling bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s, and seals
Harbor Seal
The harbor seal , also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere...

. Guano manure
Manure is organic matter used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are trapped by bacteria in the soil...

 is an effective fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

 due to its high levels of phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

 and nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 and also its lack of odor. It was an important source of nitrates for gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...

. Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 that is deficient in organic matter can be made more productive by addition of this manure.


Guano consists of ammonium oxalate
Ammonium oxalate
Ammonium oxalate, C2H8N2O4, is an oxalate salt with ammonia. It is a constituent of some types of kidney stone. Found also in guano....

 and urate, phosphates
Phosphoric acid
Phosphoric acid, also known as orthophosphoric acid or phosphoric acid, is a mineral acid having the chemical formula H3PO4. Orthophosphoric acid molecules can combine with themselves to form a variety of compounds which are also referred to as phosphoric acids, but in a more general way...

, as well as some earth salts and impurities. Guano also has a high concentration of nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

s. Bird guano has a fertilizer analysis of 11 to 16 percent nitrogen, 8 to 12 percent equivalent phosphoric acid, and 2 to 3 percent equivalent potash. Bat and seal guano are lower in fertilizer value than bird guano.


The word "guano" originates from the Quichua
Kichwa is a Quechuan language, and includes all Quechua varieties spoken in Ecuador and Colombia by approximately 2,500,000 people...

 language of the Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

 and means "the droppings of sea birds". Andean peoples collected guano from the coast of Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

 for use as soil enricher. The rulers of the Inca Empire
Inca Empire
The Inca Empire, or Inka Empire , was the largest empire in pre-Columbian America. The administrative, political and military center of the empire was located in Cusco in modern-day Peru. The Inca civilization arose from the highlands of Peru sometime in the early 13th century...

 assigned great value to guano, restricting access to it and punishing any disturbance to the birds with death.

Guano has been harvested over several centuries along the coast of Peru, where islands and rocky shores have been sheltered from humans and predators. The Guanay Cormorant
Guanay Cormorant
The Guanay Cormorant or Guanay Shag is a member of the cormorant family found in on the Pacific coast of Peru and northern Chile...

 has historically been the most important producer of guano; its guano is richer in nitrogen than guano from other seabirds. Other important guano producing species off the coast of Peru are the Peruvian Pelican
Peruvian Pelican
The Peruvian Pelican, Pelecanus thagus, is a member of the pelican family. It lives on the west coast of South America, from Lobos de Tierra Island in Peru to Pupuya Islet in Chile....

 and the Peruvian Booby
Peruvian Booby
The Peruvian Booby, Sula variegata, is an endemic bird of the Peruvian current whose distribution is restricted to the west coast of South America from Punta Pariñas in Peru to Concepción in Chile . It is the second most abundant seabird species that inhabits the Peruvian Coast and the second...

In November 1802, Alexander von Humboldt
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...

 studied guano and its fertilizing properties at Callao
Callao is the largest and most important port in Peru. The city is coterminous with the Constitutional Province of Callao, the only province of the Callao Region. Callao is located west of Lima, the country's capital, and is part of the Lima Metropolitan Area, a large metropolis that holds almost...

 in Peru, and his subsequent writings on this topic made the subject known in Europe.

The high concentration of nitrates also made guano an important strategic
Military strategy
Military strategy is a set of ideas implemented by military organizations to pursue desired strategic goals. Derived from the Greek strategos, strategy when it appeared in use during the 18th century, was seen in its narrow sense as the "art of the general", 'the art of arrangement' of troops...

 commodity. The discovery during the 1840s of the use of guano as a fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

 and its Chile saltpetre
Sodium nitrate
Sodium nitrate is the chemical compound with the formula NaNO3. This salt, also known as Chile saltpeter or Peru saltpeter to distinguish it from ordinary saltpeter, potassium nitrate, is a white solid which is very soluble in water...

 content as a key ingredient in explosives
Explosive material
An explosive material, also called an explosive, is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure...

 made the area strategically valuable.

In this context the US passed the Guano Islands Act
Guano Islands Act
The Guano Islands Act is federal legislation passed by the U.S. Congress, on August 18, 1856. It enables citizens of the U.S. to take possession of islands containing guano deposits. The islands can be located anywhere, so long as they are not occupied and not within the jurisdiction of other...

 in 1856 giving citizens discovering a source of guano the right to take possession of unclaimed land and entitlement to exclusive rights to the deposits. However, the guano could only be removed for the use of citizens of the United States. This enabled US citizens to take possession of unoccupied islands containing guano.

Control over guano played an important role in the Chincha Islands War
Chincha Islands War
The Chincha Islands War was a series of coastal and naval battles between Spain and its former colonies of Peru and Chile from 1864 to 1866, that began with Spain's seizure of the guano-rich Chincha Islands, part of a series of attempts by Isabel II of Spain to reassert her country's lost...

 (1864-1866) between Spain and a Peruvian-Chilean alliance since Spain occupied with its navy the Chincha Islands
Chincha Islands
The Chincha Islands are a group of three small islands 21 km off the southwest coast of Peru, to which they belong, near the town of Pisco,...

 depriving Peru of lucrative income.

In the second half of the 19th century guano extraction was eclipsed by salpeter
Salpeter may refer to:*Nitre*11757 SalpeterPeople with the last name Salpeter* Edwin Ernest Salpeter , U.S. astronomer* Greta Salpeter , U.S. musician...

 in the form of caliche
Caliche may refer to:*Caliche, a hardened deposit of calcium carbonate.*Caliche slang, a collection of slang words unique to Salvadoran Spanish....

 extraction from the interior of Atacama Desert
Atacama Desert
The Atacama Desert is a plateau in South America, covering a strip of land on the Pacific coast, west of the Andes mountains. It is, according to NASA, National Geographic and many other publications, the driest desert in the world...

, not far from the guano areas. After the War of the Pacific
War of the Pacific
The War of the Pacific took place in western South America from 1879 through 1883. Chile fought against Bolivia and Peru. Despite cooperation among the three nations in the war against Spain, disputes soon arose over the mineral-rich Peruvian provinces of Tarapaca, Tacna, and Arica, and the...

 (1879-1883) Chile seized much of the guano as well as salpeter producing area making its national treasury grow by 900% between 1879 and 1902 due to taxes coming from the newly acquired lands.

By the end of the 19th century, the importance of guano declined with the rise of artificial fertiliser, although guano is still used by organic
Organic farming
Organic farming is the form of agriculture that relies on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm...

 gardeners and farmers. Superphosphate
Monocalcium phosphate
Monocalcium phosphate is a chemical compound with the formula Ca2. It is commonly found as the monohydrate, Ca2·H2O.-Fertilizer:Phosphorus is an essential nutrient and therefore is a common component of agricultural fertilizers...

 made from guano is used for aerial topdressing.


The ideal type of guano is found in exceptionally dry climates, as rainwater drains the guano of nitrates. Guano is harvested on various island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...

s in the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 (for example, the Chincha Islands
Chincha Islands
The Chincha Islands are a group of three small islands 21 km off the southwest coast of Peru, to which they belong, near the town of Pisco,...

) and in other oceans (for example, Juan de Nova Island
Juan de Nova Island
Juan de Nova Island is a low, flat, tropical island in the narrowest part of the Mozambique Channel, about one-third of the way between Madagascar and Mozambique at...

 and Christmas Island
Christmas Island
The Territory of Christmas Island is a territory of Australia in the Indian Ocean. It is located northwest of the Western Australian city of Perth, south of the Indonesian capital, Jakarta, and ENE of the Cocos Islands....

). These islands have been home to mass seabird colonies for many centuries, and the guano has collected to a depth of many metres. In the 19th century, Peru was famous for its supply of guano.

Bat guano is usually mined in caves and this mining is associated with a corresponding loss of troglobytic
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...

Biota (ecology)
Biota are the total collection of organisms of a geographic region or a time period, from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales. The biota of the Earth lives in the biosphere.-See...

 and diminishing of biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

. Guano deposits support a great variety of cave-adapted invertebrate species, which rely on bat faeces as their sole nutrient input. In addition to the biological component, deep guano deposits contain local paleoclimatic
Paleoclimatology is the study of changes in climate taken on the scale of the entire history of Earth. It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within rocks, sediments, ice sheets, tree rings, corals, shells and microfossils; it then...

 records in strata that have built up over thousands of years, which are unrecoverable once disturbed.

The greatest damage caused by mining to caves with extant guano deposits is to the bat colonies themselves. Bats are highly vulnerable to regular disturbance to their roosts. Some species, such as Phyllonycteris aphylla
Jamaican Flower Bat
The Jamaican Flower Bat is a species of bat in the family Phyllostomidae. It is endemic to Jamaica.-Source:* Chiroptera Specialist Group 1996. . Downloaded on 30 July 2007....

, have low fat reserves, and will starve to death when regularly disturbed and put into a panic state during their resting period. Many species will drop pups when in panic, with subsequent death, leading to a steady reduction in population. Research in Jamaica has shown that mining for bat guano is directly related to the loss of bat species, associated invertebrates and fungi, and is the greatest threat to bat caves on the island.


In agriculture
Agriculture is the cultivation of animals, plants, fungi and other life forms for food, fiber, and other products used to sustain life. Agriculture was the key implement in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that nurtured the...

 and gardening guano has a number of uses, including as: soil builder, lawn treatments, fungicide
Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...

 (when fed to plants through the leaves), nematicide
A nematicide is a type of chemical pesticide used to kill parasitic nematodes.One common nematicide is obtained from neem cake, the residue obtained after cold-pressing the fruit and kernels of the neem tree. Known by several names in the world, the tree was first cultivated in India in ancient...

 (decomposing microbes help control nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

s), and as composting activator (nutrients and microbes speed up decomposition).

See also

  • Guano Islands Act
    Guano Islands Act
    The Guano Islands Act is federal legislation passed by the U.S. Congress, on August 18, 1856. It enables citizens of the U.S. to take possession of islands containing guano deposits. The islands can be located anywhere, so long as they are not occupied and not within the jurisdiction of other...

  • Phosphate mining in Nauru
    Phosphate mining in Nauru
    The economy of Nauru has been almost wholly dependent on phosphate, which has led to environmental catastrophe on the island, with 80% of the nation’s surface having been strip-mined...

  • Histoplasmosis
    Histoplasmosis is a disease caused by the fungus Histoplasma capsulatum. Symptoms of this infection vary greatly, but the disease primarily affects the lungs...

  • Phosphorite
    Phosphorite, phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals. The phosphate content of phosphorite is at least 15 to 20% which is a large enrichment over the typical sedimentary rock content of less than 0.2%...

  • Bat Cave mine
    Bat Cave mine
    The Bat Cave guano mine , located in the western Grand Canyon of Arizona at river mile 266, above Lake Mead, was an unusual, expensive and noteworthy mining operation. The cave was apparently discovered in the 1930s by a passing boater. After several unsuccessful attempts by others to mine the...

External links