Western Toad
|
| Common Name: | Western Toad |
| Scientific Name: | Anaxyrus boreas |
| Code: | A-ANBO |
| Status (B.C.): | Yellow |
| Status (COSEWIC): | Unranked |
|
|
At a Glance
Adult Western Toads have stocky bodies with short legs, and tend to walk rather than hop.
Their thick skin appears dry and bumpy and can range in colour from pale green to grey,
dark brown, and red. They typically have pale-coloured bellies mottled with black, and
a pale coloured stripe down their backs. Their beautiful gold-flecked
eyes have distinctive horizontal oval pupils. Behind each eye is a prominent oblong or
kidney-shaped swelling called a parotoid gland.
Adults range from 5.5 to 14.5 centimetres in body length, excluding the hind legs. Males are
generally smaller than females and have dark pads on their thumbs that help them cling to the female during mating. Their skin is usually less rough and blotched than the females' skin.
Western Toad eggs look like small black pearls laid single file in long
strings in the water. Tadpoles are black or charcoal coloured, with a dark, rounded fin along the length of their tail. Tadpoles metamorphose into toadlets as
small as 6 millimetres long that resemble miniature adults.
Home Sweet Home
Western Toads use three different types of habitat:
breeding habitats, terrestrial summer range, and winter hibernation sites. Preferred
breeding sites are permanent or temporary water bodies that have shallow sandy bottoms. After breeding, adult Western Toads disperse
into terrestrial habitats such as forests and grasslands. They may
roam far from standing water, but they prefer damp conditions. Western Toads spend much of their time underground; though they are capable
of digging their own burrows in loose soils, they generally shelter in
small mammal burrows, beneath logs and within rock crevices. They hibernate in burrows below the frostline, up to 1.3 metres underground.
This is the Life
Adult Western Toads migrate to communal breeding sites in early spring. The males search the wetland for available females. Males clasp females from behind and fertilize the eggs as the female deposits them in the water. Male toads produce a quiet, twittering ‘release call’ if they are accidentally grasped by another male. They make this call at any time of year if they are grasped around the body, but most often during the breeding season. In some areas, male toads may also call to alert females to their presence.
Once laid, the eggs quickly develop into tadpoles that hatch and swarm in groups of hundreds or thousands of individuals through the warmest, shallowest water available. By the end of the summer, the tadpoles transform into toadlets and leave the water. Dense aggregations of toadlets are often found hidden along the shore of breeding sites, and clustered in piles when the weather turns cool. These toadlets grow to maturity in two to three years, and may live ten years or more.
After spring breeding, Western Toads spend the summer and fall foraging in warm, low lying areas. They are primarily nocturnal, but are active during the day at higher elevations and latitudes. As the weather gets cold in fall and winter, Western Toads retreat into hibernation to await spring.
What’s on the Menu?
Western Toads are wonderfully adept at capturing a wide variety of insects and invertebrates. Over 95 percent of their adult diet consists of flying insects, ants, beetles, sowbugs, crayfish, spiders, centipedes, slugs, and earthworms. They will also take larger items if given a chance. Tadpoles are herbivores, feeding on aquatic plants, detritus and algae.
Although Western Toads are less tasty than other amphibian species, they are on the menu for a host of other animals. In B.C., garter snakes are a major predator of metamorphosed toads. Toads are also taken by birds, mammals and even other amphibians; adult Columbia Spotted Frogs have been seen feasting on newly metamorphosed toadlets. Western Toad tadpoles are vulnerable to birds, fishes and predaceous insect larvae.
Where and When
Western Toads are found west of the Rocky Mountains, from Mexico to southern Alaska. They
are found in semi-arid and wet forested regions of B.C., except in the north-east. They can
be found at elevations from sea level to at least 2250 metres.
Western Toads are active between January and October, depending on latitude and elevation.
Breeding and egg deposition can occur between April and July, often after rains when local
snow and ice have melted. Eggs hatch in 3 to 12 days, depending on water temperature. Tadpole
development, also dependent on water temperature, takes six to eight weeks. Hibernation lasts
from November through to April.
How Are They Doing?
Western Toads are relatively common in most of B.C., although
population declines are suspected in the southwestern part of the
province.
In the United States, Western Toad populations have
suffered significant losses. They have disappeared throughout broad
areas of their historic range, and are now a candidate for
endangered species listing in the U.S. The centre of the world’s
distribution of Western Toads has shifted from the U.S. to B.C.
The cause for such declines is still uncertain, but a combination of
threats is suspected. One of the greatest impacts on Western Toad
populations in B.C. is habitat destruction. Development in and
around wetlands can destroy or isolate populations. Migrating toads
are killed by traffic on roads. Pollution, the introduction of
aquatic predators (e.g., stocking lakes with fish), and the spread
of diseases are also harmful. Large-scale concerns such as global
warming and ozone depletion can affect Western Toads by changing
temperatures, affecting water levels, and increasing ultraviolet
radiation.
Western Toads are on the provincial Yellow List,
and are considered a species of conservation concern.
How We’re Helping
We are aiming to learn more about the distribution and ecology of
Western Toads in B.C. Identifying breeding sites and assessing
terrestrial habitat requirements is particularly important in order to
protect this species. Monitoring programs will help track Western Toad
populations over the long term.
Western Toads are protected under the
British Columbia Wildlife Act.
How You Can Help
Learn about Western Toad ecology and share your knowledge of
these fascinating creatures with others. Be an advocate for
amphibians – protect toads and their habitat in your neighbourhood.
Contributing Western Toad sighting information to B.C. Frogwatch and
monitoring breeding sites are wonderful ways to support Western Toad
conservation.
No Kidding!
- The ‘warts’ on the Western Toad are not warts at all, but glands
that produce a bitter, sticky, white fluid when the toad feels
threatened. The fluid can cause an animal’s eyes or mouth to tingle
or feel numb. This makes Western Toads unpleasant to eat, but will
not give you warts!
- Western Toads can identify predators by recognising the chemical
cues they emit. Incredibly, tadpoles injured by predators release
chemicals that warn others of impending danger. Some evidence even
suggests that chemical cues enable Western Toad tadpoles to
recognise their siblings!
- Female Western Toads produce an average of 12,000 eggs, or as
many as 16,500 eggs, in a single clutch! More than 99% of these
won’t survive to adulthood. Those that do may live for several
years, as their skin secretions are highly distasteful to would-be
predators. In captivity, individuals have survived for up to 36
years!
Photo © Wally Edwards. No reproduction or distribution without permission.
Top