Amphibians

Amphibians: the first vertebrates

Amphibians are older than the dinosaurs. In fact, they were the first group of vertebrates to bravely set out on land some 350 million years ago. All other terrestrial vertebrates — from dinosaurs to humans — owe their existence to the amphibians.

The importance of amphibians

Amphibians are quite important to ecosystems:

• An individual frog or toad can eat thousands of insects over one summer.
• Amphibians, their eggs and larvae are an important food source for many fish and birds.
• Amphibians are sensitive to changes in both water quality and adjacent land-use practices, so their populations can serve as indicators of overall environmental quality.

Amphibian monitoring programs

Many of Alberta's amphibian species are being monitored under two long-term programs, the Alberta Volunteer Amphibian Monitoring Program (AVAMP) and the Researching Amphibian Numbers in Alberta (RANA) program. To learn more about becoming involved in these programs, see:

• Amphibian Monitoring in Alberta

Classification

Amphibians form a distinct class of vertebrates (Class Amphibia) with over 4000 species world-wide. Within this class, there are four orders:

• Order Anura – includes frog and toad species
• Order Caudata – includes salamander species
• Order Gymnophiona – includes caecilians, legless amphibians that resemble earthworms or snakes
• Order Temnospondyli – includes prehistoric amphibian species that are now extinct

Only two of these orders, the Caudata (the salamanders) and the Anura (the frogs and toads), are found in Canada.

Anatomy and common characteristics

Amphibians have no unique anatomical structure, such as the feathers of birds, which sets them apart from all other animals.

However, there are some characteristics that all amphibians share:

• They are ectothermic (sometimes referred to as cold-blooded); their body temperature varies with that of the environment
• They have soft, generally moist skin without scales
• They lay eggs without shells; to prevent their eggs from drying up, amphibians lay them in water or a damp environment
• They have a two-stage life history

Life cycle

The most obvious characteristic of amphibians is their two-stage life history:

Stage One: Larval

When amphibians hatch from their eggs they are in a gilled larval form. In frogs and toads, these larvae are referred to as tadpoles.

Stage Two: Adult

After several weeks or months, these larvae change (metamorphose) into the adult air-breathing form.

Some individuals remain in the aquatic stage and continue to grow and mature. This phenomenon (referred to as neoteny) is common in the Tiger Salamander.

Species identification

Within Alberta there are 10 species of amphibians:

• There are two salamander species
• There are eight species of frogs and toads that can be subdivided as follows:
  • Spadefoots (one species)
  • Tree frogs (one species)
  • True frogs (three species)
  • True toads (three species)

Tips to identify amphibians

In general, it is quite easy to determine the amphibian species in question. Unfortunately, colour is not always a reliable indicator as many species can display a range of colours.

Often the pattern of spots or stripes is the best indicator for the frogs.

Initially, the toads can be more difficult to identify as they all seem large and warty. However, the presence or absence of a ridge between the eyes is an obvious and reliable diagnostic key.

Identification Key to Adult Amphibians

The following key works best if you have an unidentified amphibian species in hand. It should allow you to identify any amphibian native to the province.

How to use the key

Start at 1 and choose the option (A or B) that best describes the amphibian in question.

Proceed to the next number as indicated by your choice and choose the option presented there.

Repeat until you reach a species name that is linked to its description.

To confirm your identification, compare the amphibian in question with the photographs and range maps that accompany the species descriptions.

1	A.	Body covered with scales	You've got a reptile!
	B.	Body does not have scales	go to #2
2	A.	Hind legs same length as front legs and are not modified for hopping Long tail	go to Salamanders #3
	B.	Hind legs much longer than front legs, and are muscular and modified for hopping No tail	go to Frogs and Toads #4
Salamanders
3	A.	Irregular yellowish stripe (may be broken) down back 4th toe on hind foot noticeably longer than the other toes long toes	Long-toed Salamander
	B.	Back and sides striped or spotted 4th toe about the same length as others	Tiger Salamander
Frogs and Toads
4	A.	Dorsolateral folds (ridges) present: you can see a fold or ridge of some kind running along the animal's back at the sides	go to True Frogs #5
	B.	Dorsolateral folds absent: animal's back at the sides shows no discernable folds or ridges	go to True Frogs #7
True Frogs
5	A.	Green or brown Light-coloured dorsolateral folds Dark spots with a light border	Northern Leopard Frog
	B.	Dorsolateral folds small and not light-coloured	go to #6
6	A.	Dark eye mask Back smooth No red on belly	Wood Frog
	B.	No eye mask Small warts on back Red colour on belly	ColumbiaSpotted Frog
7	A.	Skin fairly smooth Parotoid (poison) glands absent from shoulders	go to Spadefoots and Tree Frogs #8
	B.	Skin very warty Parotoid (poison) glands present on shoulders	go to True Toads #9
Spadefoots and Tree Frogs
8	A.	Large, squat body Single black knob or "spade" on hind feet Pupil vertical	Plains Spadefoot
	B.	Small, slender body No knob on hind feet Pupil horizontal	Boreal Chorus Frog
True Toads
9	A.	No cranial crest (raised ridge between eyes)	Western Toad
	B.	Cranial crests present	go to #10
10	A.	Cranial crests parallel or joined behind eyes to form one raised ridge Belly spotted	Canadian Toad
	B.	Cranial crests diverge behind eyes Belly unspotted	Great Plains Toad

Page Navigation

Skip to breadcrumb trail

Page Information

Posted: October 9, 2009