The Colorado River toad (''Incilius alvarius''), also known as the Sonoran Desert toad, is a
toad
Toad (also known as a hoptoad) is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands.
In popular culture (folk taxonomy ...
species found in northwestern
Mexico
Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
and the
southwestern United States
The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...
. It is well known for its ability to
exude toxin
A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...
s from glands within its skin that have
psychoactive
A psychoactive drug, psychopharmaceutical, mind-altering drug, consciousness-altering drug, psychoactive substance, or psychotropic substance is a chemical substance that alters psychological functioning by modulating central nervous system acti ...
properties.
Description
The Colorado River toad can grow to about long and is the largest toad in the United States apart from the non-native
cane toad
The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, Terrestrial animal, terrestrial true toad native to South America, South and mainland Central America, but which has been Introduced spe ...
(''Rhinella marina''). It has a smooth, leathery skin and is olive green or mottled brown in color. Just behind the large golden eye with horizontal pupil is a bulging kidney-shaped
parotoid gland
The parotoid gland (alternatively, paratoid gland) is an external skin gland on the back, neck, and shoulder of some frogs (especially toads), and salamanders. It can secrete a number of milky alkaloid substances (depending on the species) known ...
. Below this is a large circular pale green area which is the
tympanum or ear drum. By the corner of the mouth there is a white wart and there are white glands on the legs. All these glands produce toxic secretions. Its call is described as, "a weak, low-pitched toot, lasting less than a second."
Dogs (''Canis familiaris'') that have attacked toads have suffered paralysis or even death.
Raccoon
The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...
s (''Procyon lotor)'' have learned to pull a toad away from a pond by the back leg, turn it on its back and start feeding on its belly, a strategy that keeps the raccoon well away from the poison glands.
Unlike other vertebrates, this amphibian obtains water mostly by
osmotic absorption across its abdomen. Toads in the family Bufonidae have a region of skin known as "the seat patch", which extends from mid abdomen to the hind legs and is specialized for rapid rehydration. Most of the rehydration is done through absorption of water from small pools or wet objects.
Distribution and habitat

In the
United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
, the Colorado River toad is found in the lower
Colorado River
The Colorado River () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The river, the List of longest rivers of the United States (by main stem), 5th longest in the United St ...
and the
Gila River
The Gila River (; O'odham ima Keli Akimel or simply Akimel, Quechan: Haa Siʼil, Maricopa language: Xiil) is a tributary of the Colorado River flowing through New Mexico and Arizona in the United States. The river drains an arid watershed of ...
catchment areas, in extreme southwestern
New Mexico
New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
and much of southern
Arizona
Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...
. It is considered possibly
extirpated
Local extinction, also extirpation, is the termination of a species (or other taxon) in a chosen geographic area of study, though it still exists elsewhere. Local extinctions are contrasted with global extinctions.
Local extinctions mark a chan ...
from
California
California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
. In Mexico, the toad is found in the states of
Sonora
Sonora (), officially Estado Libre y Soberano de Sonora (), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is divided into Municipalities of Sonora, 72 ...
,
Sinaloa
Sinaloa (), officially the (), is one of the 31 states which, along with Mexico City, compose the Federal Entities of Mexico. It is divided into 18 municipalities, and its capital city is Culiacán Rosales.
It is located in northwest Mexic ...
, and
Chihuahua. It lives in both
desert
A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...
and
semi-arid
A semi-arid climate, semi-desert climate, or steppe climate is a aridity, dry climate sub-type. It is located on regions that receive precipitation below Evapotranspiration#Potential evapotranspiration, potential evapotranspiration, but not as l ...
areas throughout its range. It is
semiaquatic
In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...
and is often found in streams, near springs, in
canal
Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface ...
s and drainage ditches, and under water troughs.
[ The Colorado River toad is known to breed in artificial water bodies (e.g., flood control impoundments, reservoirs) and as a result, the distributions and breeding habitats of these species may have been recently altered in south-central Arizona. It often makes its home in rodent burrows and is ]nocturnal
Nocturnality is a ethology, behavior in some non-human animals characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnality, diurnal meaning the opposite.
Nocturnal creatur ...
.
Biology
The Colorado River toad is sympatric
In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...
with the spadefoot toad (''Scaphiopus'' spp.), Great Plains toad (''Anaxyrus cognatus''), red-spotted toad (''Anaxyrus punctatus''), and Woodhouse's toad (''Anaxyrus woodhousei''). Like many other toads, they are active foragers and feed on invertebrates, lizards, small mammals, and amphibians. The most active season for toads is May–September, due to greater rainfalls (needed for breeding purposes). The age of ''I. alvarius'' individuals in a population at Adobe Dam in Maricopa County, Arizona
Maricopa County () is a County (United States), county in the south-central part of the U.S. state of Arizona. As of the 2020 United States census, 2020 census the population was 4,420,568, or about 62% of the state's total, making it the List ...
, ranged from 2 to 4 years; other species of toad have a lifespan of 4 to 5 years. The taxonomic affinities of ''I. alvarius'' remain unclear, but immunologically, it is similarly close to the ''boreas'' and ''valliceps'' groups.
Breeding
The breeding season starts in July, when the rainy season begins, and can last up to August. Normally, 1–3 days after the rain is when toads begin to lay eggs in ponds, slow-moving streams, temporary pools or man-made structures that hold water. Eggs are 1.6 mm in diameter, 5–7 mm apart, and encased in a long single tube of jelly with a loose but distinct outline. The female toad can lay up to 8,000 eggs.
Psychotropic uses
The toad's primary defense system is glands that produce a poison that may be potent enough to kill a grown dog. These parotoid gland
The parotoid gland (alternatively, paratoid gland) is an external skin gland on the back, neck, and shoulder of some frogs (especially toads), and salamanders. It can secrete a number of milky alkaloid substances (depending on the species) known ...
s also produce 5-methoxy-dimethyltryptamine (5-MeO-DMT) and bufotenin (which is named after the '' Bufo'' genus of toads); both of these chemicals belong to the family of hallucinogenic tryptamines
Substituted tryptamines, or simply tryptamines, also known as serotonin analogues (i.e., 5-hydroxytryptamine analogues), are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all trypt ...
. Bufotenin can be toxic.
When vaporized, a single deep inhalation of the poison produces strong psychoactive effects within 15 seconds. After inhalation, the user usually experiences a warm sensation, euphoria, and strong visual and auditory hallucinations, due to 5-MeO-DMT's high affinity for the 5-HT2 and 5-HT1A serotonin receptor
5-HT receptors, 5-hydroxytryptamine receptors, or serotonin receptors, are a group of G protein-coupled receptor and ligand-gated ion channels found in multiple tissues including the central and peripheral nervous systems. They mediate both ex ...
subtypes.
Bufotenin is a chemical constituent in the secretions and eggs of several species of toads belonging to the genus '' Bufo'', but the Colorado River toad (''Incillius alvarius'') is the only toad species in which bufotenin is present in large enough quantities for a psychoactive effect. Extracts of toad secretion, containing bufotenin and other bioactive compounds, have been used in some traditional medicines such as ''ch’an su'' (probably derived from ''Bufo gargarizans
The Asiatic toad or Chusan Island toad (''Bufo gargarizans'') is a species of toad endemic to East Asia. The species was previously classified as ''Bufo bufo gargarizans'', a subspecies of the common toad.
Distribution and habitat
It is commo ...
''), which has been used medicinally for centuries in China, as a herbal remedy often illegally imported to the USA that can be prepared as a tea.
The toad was "recurrently depicted in Mesoamerican
Mesoamerica is a historical region and cultural area that begins in the southern part of North America and extends to the Pacific coast of Central America, thus comprising the lands of central and southern Mexico, all of Belize, Guatemala, El S ...
art", which some authors have interpreted as indicating that the effects of ingesting ''Bufo'' secretions have been known in Mesoamerica for many years; however, others doubt that this art provides sufficient ethnohistorical evidence to support the claim.
In addition to bufotenin, ''Bufo'' secretions also contain digoxin
Digoxin (better known as digitalis), sold under the brand name Lanoxin among others, is a medication used to treat various heart disease, heart conditions. Most frequently it is used for atrial fibrillation, atrial flutter, and heart failure. ...
-like cardiac glycoside
Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by inhibiting the cellular sodium-potassium ATPase pump. Their beneficial medical uses include treatments for ...
s, and ingestion of the poison can be fatal. Ingestion of ''Bufo'' toad toxins and eggs by humans has resulted in several reported cases of poisoning, some of which resulted in death. The first reported death associated with the ingestion of ch'an su was that of a young woman who consumed it as a prescribed (by a Chinese herbalist) Chinese herbal remedy mixed into a tea (an approximately 100ml bowl). Immediately upon ingesting the ch'an tea, the woman experienced vomiting, difficulty breathing, and gastric tenderness, which spurred her husband to take her to the emergency room, where she died two and a half hours after drinking the tea.
Contemporary reports indicate that bufotenin-containing toad toxins have been used as a street drug; that is, as a supposed aphrodisiac
An aphrodisiac is a substance that increases libido, sexual desire, sexual attraction, sexual pleasure, or sexual behavior. These substances range from a variety of plants, spices, and foods to synthetic chemicals. Natural aphrodisiacs, such as ...
, ingested orally in the form of ''ch’an su'',[ and as a psychedelic, by smoking or orally ingesting ''Bufo'' toad secretion or dried ''Bufo'' skins. The use of ''chan'su'' and ''love stone'' (a related toad toxin preparation used as an aphrodisiac in the ]West Indies
The West Indies is an island subregion of the Americas, surrounded by the Atlantic Ocean, North Atlantic Ocean and the Caribbean Sea, which comprises 13 independent island country, island countries and 19 dependent territory, dependencies in thr ...
) has resulted in several cases of poisoning and at least one death. The practice of orally ingesting toad secretions has been referred to in popular culture and in the scientific literature as "toad licking" and has drawn media attention. Ken Nelson (under the pseudonym of Albert Most) published a booklet (illustrated by Gail Patterson) titled '' Bufo alvarius: The Psychedelic Toad of the Sonoran Desert'' in 1984 which explained how to extract and smoke the secretions.
Among the notable people who have spoken publicly about their experiences with the psychoactive agents in the poison are boxer Mike Tyson
Michael Gerard Tyson (born June 30, 1966) is an American former professional boxer who competed between 1985 and 2024. Nicknamed "Iron Mike" and "Kid Dynamite" in his early career, and later known as "the Baddest Man on the Planet", Tyson i ...
, comedian Chelsea Handler, podcaster Joe Rogan
Joseph James Rogan (born August 11, 1967) is an American podcaster, Ultimate Fighting Championship, UFC color commentator, comedian, actor, and former television host. He hosts The Joe Rogan Experience, ''The Joe Rogan Experience'', which is o ...
, television personality Christina Haack, and motivational speaker Anthony Robbins.
On October 31, 2022 the United States National Park Service
The National Park Service (NPS) is an List of federal agencies in the United States, agency of the Federal government of the United States, United States federal government, within the US Department of the Interior. The service manages all List ...
posted a warning on Facebook
Facebook is a social media and social networking service owned by the American technology conglomerate Meta Platforms, Meta. Created in 2004 by Mark Zuckerberg with four other Harvard College students and roommates, Eduardo Saverin, Andre ...
that people should not handle or lick the toad. Despite the warning's wide coverage in media, the post was made humorously and the Park Service has no records of people licking or otherwise harassing the toads in parks.
U.S. state laws
A substance found among the toxins the toad excretes when it is threatened, 5-MeO-DMT
5-MeO-DMT (5-methoxy-''N'',''N''-dimethyltryptamine), also known as ''O''-methylbufotenin or mebufotenin (), is a naturally occurring psychedelic of the tryptamine family. It is found in a wide variety of plant species, and is also secreted by ...
, is often dried into crystals and smoked. It is considered illegal in the United States, and categorized as a Schedule 1 substance, though law enforcement is increasingly less likely to enforce the laws with its growing popularity.
The toads received national attention in 1994 after ''The New York Times Magazine
''The New York Times Magazine'' is an American Sunday magazine included with the Sunday edition of ''The New York Times''. It features articles longer than those typically in the newspaper and has attracted many notable contributors. The magazi ...
'' published an article about a California teacher who became the first person to be arrested for possessing secretions of the toads. Bufotenin had been outlawed in California since 1970.
In November 2007, a man in Kansas City, Missouri
Kansas City, Missouri, abbreviated KC or KCMO, is the largest city in the U.S. state of Missouri by List of cities in Missouri, population and area. The city lies within Jackson County, Missouri, Jackson, Clay County, Missouri, Clay, and Pl ...
, was discovered with an ''I. alvarius'' toad in his possession, and charged with possession of a controlled substance after they determined he intended to use its secretions for recreational purposes. In Arizona, one may legally bag up to 10 toads with a fishing license, but it could constitute a criminal violation if it can be shown that one is in possession of this toad with the intent to smoke its secretions.[AZGFD.gov]
None of the U.S. states in which ''I. alvarius'' is or was indigenous – California, Arizona, and New Mexico – legally allows a person to remove the toad from the state. For example, the Arizona Game and Fish Department is clear about the law in Arizona: "An individual shall not...export any live wildlife from the state; 3. Transport, possess, offer for sale, sell, sell as live bait, trade, give away, purchase, rent, lease, display, exhibit, propagate...within the state."
Threatened species
Due to the rising popularity in collecting this toad, compounded with other threats such as motorists running over them, and predators such as raccoons eating them, U.S. states such as New Mexico and California have listed them as "threatened" and collecting ''I. alvarius'' is unlawful in those states. Collecting these toads is thought to cause stress to them, in particular during the process of "milking" where collectors rub the toads under the chin to cause it to secrete the poison in the form of a milky substance that is then scraped from the body of the toad. Robert Villa, who serves as president of the Tucson Herpetological Society, said in a 2022 ''New York Times'' interview, "There’s a perception of abundance, but when you begin to remove large numbers of a species, their numbers are going to collapse like a house of cards at some point."[
Efforts to breed the toads in large quantities to offset their losses in the wild are criticized as potentially attracting predators to these areas, and creating a disease vector for pathogens such as chytrid fungus, which can then spread to devastate more of them in the wild. Synthetic forms of the drug that collectors seek in the toad poison are fairly easy to produce and may offset overcollection.][
]
References
Further reading
*
*
External links
Arizona: Tucson Herpetological Society – pictures
{{Taxonbar, from=Q10534901
alvarius
5-HT2A agonists
Amphibians of Mexico
Amphibians of the United States
Causes of death
Toad, Colorado River
Amphibians described in 1859
Taxa named by Charles Frédéric Girard
Biological sources of psychoactive drugs
Psychedelic drugs
Psychedelic tryptamine carriers
Serotonin receptor agonists