Geographic Range
Yosemite toads are found in a small area of the Sierra Nevada Mountains in California.
They have never been found outside of California.
Bufo canorus
range from the Blue Lakes region of Ebbets Pass to Kaiser Pass located near Evolution
Lake in the Darwin Canyon area. They are found at high elevations in only two Californian
counties, Alpine and Fresno counties.
Habitat
Yosemite toads are found in wet mountain meadows, often near pine forests. Even though
they spend most of their time on land, they are never far from a permanent body of
water. In their juvenile stage, Yosemite toad tadpoles swim in shallow pools of melted
ice water, and in slow moving mountain streams.
Bufo canorus
live at high elevations, anywhere from 1950 meters to 3450 meters up on a mountain
side. These grassland amphibians burrow under the soil, crawl beneath rocks and fallen
logs and seek shelter in abandoned rodent holes during the night.
- Habitat Regions
- temperate
- terrestrial
- Terrestrial Biomes
- savanna or grassland
- mountains
- Aquatic Biomes
- rivers and streams
- temporary pools
Physical Description
Bufo canorus
are moderate size amphibians ranging from 4.5 cm to 7.5 cm. They show the highest
degree of sexual dichromatism, different coloration between sexes, found among Californian
toads. As in most sexually dimorphic animals, males exhibit brighter colors than
females. Yosemite toad males are olive green to yellow green with small dark flecks,
while females are gray or brown with large dark spots.
The young tadpoles look nothing like the adult toads, but it only takes them 7 to
9 weeks to metamorphose into adults. Yosemite toads are closely related to three
other toads, the black, western and Amargosa toads. Together they make up the "boreas
group." The Yosemite toads' high degree of sexual dichromatism distinguishes them
from their relatives. Other features that distinguish the
B. canorus
from closely related species are their smaller size, wider paratoid glands and lack
of a vertebral stripe.
- Other Physical Features
- ectothermic
- heterothermic
- bilateral symmetry
- poisonous
- Sexual Dimorphism
- sexes colored or patterned differently
- male more colorful
Development
Yosemite toads lay their eggs in shallow pools of water from May to mid August. Eggs
hatch in 10 to 12 days and tadpoles metamorphose into adults seven to nine weeks after
hatching. The first few years of
Bufo canorus
lives are not reproductive. Females reach reproductive age at four to six years
and males at three to five years.
The biggest cause of mortality among tadpoles is desiccation. When the snowfall is
low the pools of water that form in the spring dry up too quickly for the toads to
metamorphose in time. Recent drought in California may be one reason this toads'
population has greatly declined.
- Development - Life Cycle
- metamorphosis
Reproduction
Yosemite toads spawn, lay eggs, in shallow pools and slow moving streams in mountain
meadows. After hibernation the males leave the meadows and search for water. They
arrive at their breeding sites several days before the females. Both sexes are active
during the day and there are about ten times as many males at breeding sites as females.
Males stay at an individual site for a maximum of two weeks and females only for a
few days. Both sexes try to increase their fitness by mating as often as possible
with as many partners as possible. The males try to attract their mates by emitting
very melodious sounds during the day. Many people mistake the mating calls of the
Yosemite toads for songs of spring birds.
Canorus
means "tuneful" in Latin.
- Mating System
- polygynandrous (promiscuous)
Breeding season of
B. canorus
begins in May, when the ice melts and forms shallow pools, and continues until mid
August. Like most frogs and toads, Yosemite toads have external fertilization.
The females lay their eggs in single or double strands and sometimes in clusters in
shallow water and the males fertilize them. Females may lay anywhere from 1500 to
2000 eggs. These hatch in less than a week and a half and metamorphose into adults
in about two months. A temperature of below 31 degrees Celsius must be maintained
in order for the eggs to develop. For the larvae to survive, a temperature of less
than 36 degrees Celsius is necessary. Adults do not seem to react to varying temperatures
during their active season; instead they are sensitive to moisture. The females reach
reproductive age at four to six years and males at the age of three to five.
Bufo canorus
have been known to hybridize with
Bufo boreas
in the northern parts of their range.
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- oviparous
Yosemite toads do not exhibit parental care. After eggs have been fertilized both
parents go in search of other mates.
- Parental Investment
- no parental involvement
Lifespan/Longevity
B. canorus
is a long living species. Females live at least 15 years while males live shorter
lives of at least 12 years.
Behavior
Yosemite toads are only active during the day. During the night they burrow in soil,
under logs, and in rodent tunnels. They are solitary creatures except during the
breeding season, when males are found congregated around shallow pools of water emitting
their melodious trills.
B. canorus
start hibernation in late September or early October, and they come out of their
deep sleep sometimes in April, May or July depending on temperature. Even though
the Yosemite toads keep to themselves they are not territorial.
- Key Behaviors
- terricolous
- fossorial
- saltatorial
- diurnal
- motile
- hibernation
- solitary
Communication and Perception
During breeding season
B. canorus
males assemble in the day and call to the females in choruses. Their melodious calls
are often mistaken for bird calls.
- Other Communication Modes
- choruses
Food Habits
The feeding patterns of the adult and larvae Yosemite toads differ.
Bufo canorus
larvae eat plankton and detritus, while the adults are primarily insectivorous.
In the summer,
hymenopterans
are a major part of the toads' diet. Some specific foods of
B. canorus
are
ants
,
centipedes
,
spiders
,
ladybird beetles
,
mosquitoes
,
weevils
,
tenebrionid beetles
, and
millipedes
.
- Primary Diet
- carnivore
- Animal Foods
- insects
- terrestrial non-insect arthropods
- Plant Foods
- phytoplankton
- Other Foods
- detritus
Predation
It may be that the coloration of
B. canorus
makes it hard to spot for predators. These toads' main defense mechanisms against
predation, however, are their poison glands. Like many other toads, this species has
enlarged paratoid glands at the side of its neck. The paratoid glands secrete a white
poison that protects the Yosemite toads from prospective predators by causing nausea,
inflammation of the mouth, or irregular heart beat. This poses a danger to the toads'
predators and can be irritating to humans if it gets into the mouth or eyes. In extreme
cases the poison can cause death to its ingestor. The taste of the mucous-like poison
is also very unpleasant.
- Anti-predator Adaptations
- cryptic
Ecosystem Roles
The Yosemite toads and tadpoles provide a minor food source for birds and snakes in
the Sierra Nevada Mountain ecosystem. Their number and success may be an indicator
of the amount of pollution in that ecosystem, but this has not yet been determined.
The toads' soil burrowing habits may also contribute minimally to the aeration of
the soil.
- Ecosystem Impact
- soil aeration
Economic Importance for Humans: Positive
Yosemite toads may be beneficial to people by controlling populations of insects. The poison in the paratoid glands may also be beneficial once researched.
- Positive Impacts
- research and education
- controls pest population
Economic Importance for Humans: Negative
The poison in the paratoid glands of the Yosemite toads irritates the skin and causes
inflammation, and may be dangerous to humans if it gets into the eyes and mouth.
- Negative Impacts
- injures humans
Conservation Status
In addition to its listing as an endangered animal on the IUCN Red List,
Bufo canorus
is a Category 2 candidate for listing as an Endangered Species by the United States
fish and Wildlife Service. Vehicular traffic kills, prolonged periods of drought,
and disease all claim partial responsibility in the rapid decline of
Bufo canorus
. Attempts are being made at various zoological institutions throughout the U.S. to
successfully breed and reintroduce this species back into its native range.
Additional Links
Contributors
David Armitage (editor), Animal Diversity Web.
maria filipowska (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- terrestrial
-
Living on the ground.
- tropical savanna and grassland
-
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
- savanna
-
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
-
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
- mountains
-
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- heterothermic
-
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- poisonous
-
an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- external fertilization
-
fertilization takes place outside the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- fossorial
-
Referring to a burrowing life-style or behavior, specialized for digging or burrowing.
- saltatorial
-
specialized for leaping or bounding locomotion; jumps or hops.
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- hibernation
-
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
- solitary
-
lives alone
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- choruses
-
to jointly display, usually with sounds, at the same time as two or more other individuals of the same or different species
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- phytoplankton
-
photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)
- detritus
-
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
- cryptic
-
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
- soil aeration
-
digs and breaks up soil so air and water can get in
- poisonous
-
an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
- metamorphosis
-
A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.
References
Davidson, C., C. Kagarise Sherman. July 1994. "Bufo canorus - Yosemite Toad" (On-line ). Species Tour of California. Accessed 3/19/03 at http://ice.ucdavis.edu/Toads/canorus.html .
Hammerson, G. October 2002. "Bufo canorus" (On-line ). NatureServe Explorer: An online encyclopedia of life. Accessed 03/19/03 at http://www.natureserve.org/explorer .
Kagarise Sherman, C. 1980. A comparison of the natural history and mating system of two Anurans : Yosemite toads (Bufo canorus) and black toads (Bufo exsul). Thesis (Ph. D.)--University of Michigan: 378-394.
Leonard, W. 2002. "Yosemite Toad" (On-line ). eNature.com. Accessed 03/19/03 at http://www.enature.com .
Romanisic, J., Y. Chaver. 2002. "Bufo canorus" (On-line). Amphibia Web. Accessed March 19, 2003 at http://amphibiaweb.org/ .
Shaffer, B., G. Fellers, A. Magee, R. Voss. 2000. The genetics of amphibian declines: population substructure and molecular differentiation in the Yosemite toad, Bufo canorus (Anura, Bufonidae) based on single-strand conformation polymorphism analysis (SSCP) and mitochondrial DNA sequence data. Molecular Ecology , 9/3: 245-257.