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Nova Scotia Herpetofaunal Atlas
Tadpoles and Larvae

Identifying Amphibian Larvae

Welcome to our new webpage on amphibian larvae! Many of you have asked us how to distinguish tadpoles of different species, so we decided to put together a preliminary guide. Learning to distinguish the different tadpoles will be challenging, but ultimately should be very rewarding. After all, how many naturalists can say that they know the difference between a Green Frog tadpole and a Bullfrog tadpole? We are confident that with time and patience, you will be able to reliably identify some species (e.g. Bullfrog tadpoles). Identification of other species may not be possible using gross morphology - even the experts have to dissect the tadpoles and look at the mouthparts. For instance, Yellow-spotted and Blue-spotted Salamander larvae are extremely difficult to identify and as far as we know have no distinguishing features. When using tadpole size, be sure to consider the age of the tadpole. All newly hatched tadpoles are very small and difficult to distinguish (but you probably won't see the small ones). Use tadpoles with legs to compare size.

The information on this webpage was taken from a variety of books and webpages (see bottom of page), which may not be entirely accurate for Nova Scotia because tadpoles can change shape depending on habitat and the kind of predators present. To get a perspective on Nova Scotia tadpoles, Fred Scott examined the entire collection of specimens from the Nova Scotia Museum of Natural History. However, there were few specimens and those present were often poorly preserved or unidentified. We would welcome any additional information (morphology, habitat, behaviour) and any clear pictures of Nova Scotia tadpoles.

If you have any doubt whatsoever about your identification, please do not enter the information as an atlas record. If you would like more help, feel free to send us a picture of the habitat and the tadpole. Pictures taken with the subject next to a ruler and with information on the habitat type and time of year are the most useful.

Before you begin with the species descriptions, take a look at the drawing below. It will help you understand the terms used to describe tadpole anatomy.

Drawing by Fred Scott

Species and ease of identification

Salamanders
Yellow-spotted Salamander - Extremely HARD
Blue-spotted Salamander - Extremely HARD
Eastern Redback Salamander - N/A
Four-toed Salamander - EASY
Red-spotted Newt - EASY

Frogs

Eastern American Toad - EASY
Spring Peeper - EASY
Wood Frog - EASY
Leopard Frog - Extremely HARD
Pickerel Frog - Extremely HARD
Mink Frog - Extremely HARD
Green Frog - Extremely HARD
Bullfrog - EASY

Salamanders *Yellow-spotted salamanders* Time larvae are present: Early May to August. Description: Newly hatched and older larvae are dull olive green and do not have any noticeable markings. All larvae have white bellies with no pigmentation. The tail fin is finely stippled/lightly mottled with dark pigmentation at the tip. Juveniles look like adults but have lighter bellies and less noticeable spotting on their backs. Larval period: 2-4 months. Some populations may overwinter as larvae. Habitat: Tadpoles are found in woodland ponds, vegetated coves of lakes, quiet vegetated portions of streams, and roadside ditches. Tadpoles have never been observed from lakes with large predaceous fish. Water bodies may be ephemeral. Confusing Species: Yellow-spotted salamander larvae are very difficult to distinguish from Blue-spotted Salamander larvae. We do not recommend submitting atlas records for the larvae of either species.	Yellow-spotted Salamander larva (Photo from the Massachussetts Vernal Pool Association ) Photo: Scott Egan (photo from Rhode Island)
*Blue-spotted salamanders* Time larvae are present: Early May to August. Description: Newly hatched larvae have dark brown backs with yellowish bars on their sides. Older larvae are brownish with a yellowish stripe along their side that fades with time. The stomach has no marking except for some dark pigment around the edge of the lower jaw. Older larvae also have dorsal fins with many black blotches. Newly transformed juveniles have yellowish spots on their stomach and back. Larval period: 2-3 months. Habitat: Larvae are found in shallow woodland ponds and ditches that do not contain large, predaceous fish. Confusing Species: Blue-spotted salamander larvae are very difficult to distinguish from Yellow-spotted Salamander larvae. We do not recommend submitting atlas records for the larvae of either species.	Blue-spotted Salamander larva (Photo from the Massachussetts Vernal Pool Association )
*Eastern Redback Salamander* No larval stage: Juveniles, which look like miniature adults, hatch in August or September.
*Four-toed Salamander* Time larvae are present: Mid-May to June. Description: Hatchlings are slender with prominent eyes and have a mottled yellowish brown back. Their tail fin tapers forward almost to the head. Newly transformed individuals resemble adults, but have shorter tails . Larval period: About 1 month. Habitat: Sphagnum bogs.	Photo: Wayne Van Devender (photo not from Nova Scotia)
*Red-spotted Newts* Time larvae are present: July to September. Description: Red-spotted Newt hatchlings are yellowish green with two wide dark bands that extend down either side of the back. Older larvae have a distinct black line through the eye. Juveniles turn red 1-2 weeks after metamorphosis. Larval period: Aquatic newt larvae usually transform into the terrestrial eft, although in some populations this step is skipped and the larvae transform directly into the aquatic adult. The aquatic larval stage lasts 4-6 months, and the eft stage lasts 1-7 years. Some aquatic adults may return to land as efts.	Photo: Scott Egan (Photo from Rhode Island) Photo: Scott Egan (photo from Rhode Island)
Frogs *Eastern American Toad* Time tadpoles are present: May to mid-August. Distinguishing features: Toad tadpoles are typically small and black although you can see golden spots at magnification. The dorsal fin is low and the tail is rounded at the tip. Larval period: 5-10 weeks. Newly metamorphosed toadlets are tiny (10mm in length). Habitat: Lake and pond shallows. Look in clear shallow water in open areas. Toads avoid laying eggs in areas where Wood Frog tadpoles are present. Behaviour: Toad tadpoles generally congregate in large (sometimes 1000s), gregarious groups. The tadpoles sink when they are not swimming, and so are often seen resting on the bottom. Tadpoles are so closely aggregated that they practically touch each other. Tadpoles are out in the open. Confusing Species: Toad tadpoles resemble Wood Frog tadpoles, however, the time of year that the tadpoles are present and behaviour can be used to help differentiate the two species. Toad tadpoles are not present in early spring and are more closely aggregated than wood frogs.	Photo: Scott Egan (photo from Rhode Island) Photo: Jim Wolford (photo from Newfoundland)
*Spring Peepers* Time tadpoles are present : April to August. Distinguishing features: Spring Peeper tadpoles are the only tadpoles in Nova Scotia with lateral eyes. All the other local tadpoles have dorsal eyes. Body colour is uniform ranging from brown to transparent. Throat is speckled. Tadpoles are small and light in colour relative to other tadpoles. Larval period: 90-115 days. Behaviour: Tadpoles are usually seen in mid-water in loose groups. Habitat: Tadpoles are found in or near vegetation in shallow still water. Drawing by Fred Scott	Photo: Scott Egan (photo from Rhode Island)
*Wood Frogs* Time tadpoles are present : April to June. Distinguishing features: Wood frog tadpoles are globular and uniformly dark. Their tail fin is high and starts at or just before the body-tail junction. Larval period: 2 - 3 months. Habitat: Wood Frog tadpoles are found in any body of water near on in woods, especially if the pond is well shaded by trees. Water bodies may be ephemeral. Wood Frog tadpoles are found in open areas. Behaviour: Wood Frog tadpoles aggregate in small, spread out groups. Group size is smaller and the distance between tadpoles is greater (generally more than 1 cm apart) than in Toads. Wood Frog tadpoles are usually off the bottom. Confusing species: Toad tadpoles could be confused with Wood Frog tadpoles because they are about the same size and colour, however, toad tadpoles are not present in the early spring and they aggregate more closely together than wood frogs.	Photo: Scott Egan (photo from Rhode Island) Photo: Scott Egan (photo from Rhode Island)
*Leopard Frogs* Time tadpoles are present : May to August (but sometimes September and early October). Some tadpoles may overwinter. Distinguishing features: Leopard Frog tadpoles have a white lip line that is absent from other NS tadpoles. The dorsal fin has a low to medium arch and the body is somewhat flattened. Larval period: 2-2.5 months. Tadpoles transform in July and August, sometimes Sept and early Oct. Habitat: Tadpoles are found among plants in the shallows of ponds, lakes, cattail marshes or drainage ditches. Confusing species: Pickerel Frogs. Look for the white lip line in Leopard Frogs and a highly arched tail in Pickerel Frogs. Probably not possible to distinguish these tadpoles using gross morphology.	Photo: Ronn Altig (photo not from Nova Scotia)
*Pickerel Frogs* Time tadpoles are present : Mid-May to mid-August. Some tadpoles may overwinter. Distinguishing features: Pickerel frog tadpoles are purplish black with light spots. Their tail is highly arched, uniformly speckled, and begins on the body before the body-tail junction. Larval period: 3 months. Habitat: Tadpoles are found at the edges of lakes and in strings of ponds. Confusing species: Leopard Frogs. Look for the white lip line in Leopard Frogs and a highly arched tail in Pickerel Frogs. Probably not possible to distinguish these tadpoles using gross morphology. Photo: Scott Egan (photo from Rhode Island)	Photo: Ronn Altig (photo not from Nova Scotia) Photo: Scott Egan (photo from Rhode Island)
*Mink Frogs* Time tadpoles are present : Because the larval period in Mink Frog takes a year, tadpoles are present all summer. Distinguishing features: The body of Mink Frog tadpoles is not noticeably flattened. The tail has a long, low arch and starts near the body-tail junction. There are no black markings on the last third of the tail. Larval period: One year. Habitat: Tadpoles are found in vegetated coves of lakes or slow-moving vegetated streams. Mink Frogs appear to tolerate cooler water. Confusing species: Very difficult to distinguish from Green Frog tadpoles. Look at the dorsal fin position (see diagram at top of page) and habitat. The dorsal fin in Mink Frogs starts near the body-tail junction. In Green Frogs, the dorsal fin starts after the body-tail junction. Habitat can also help separate the two species. If you are trying to decide between a Green Frog and a Mink Frog and you find the tadpole in a roadside ditch or in small roadside ponds with no connection to a large body of water, you have a Green Frog tadpole.	Photo: Ronn Altig (photo not from Nova Scotia)
*Green Frogs* Time tadpoles are present : Because Green Frog tadpoles can take two years to transform, first and second year tadpoles are present throughout year. Young of the year appear in June. Distinguishing features: Green Frog tadpoles have a body that is noticeably wider than high (appears flattened). The tail fin is long with a low arch and is about 2/3 of the tadpole's total length. There are no spots on the tail fin, but the last third of the tail often has a black mottled pattern. The dorsal fin begins after the body-tail junction. Habitat: The most ubiquitous frog in Nova Scotia, Green Frogs are found in almost every body of water, especially small roadside ponds. Tadpoles tend to stay in the vegetation. Confusing species: Very difficult to distinguish from Mink Frogs (see above). Green Frog tadpoles can also be confused with Bullfrog tadpoles but usually can be distinguished. Bullfrog tadpoles have tails that are clearly different from Green Frogs. Note that spots with sharp margins are present on the dorsal fin of Bullfrog tadpoles but are missing from Green Frog tadpoles (see below for other distinguishing features) . Larval period: Up to two years.	Photo: Scott Egan (Photo from Rhode Island)
*Bullfrogs* Time tadpoles are present : Because the larval period in Bullfrogs can take three years, first, second, and third year tadpoles are present throughout year. Young of the year appear in June. Distinguishing features: Bullfrog tadpoles are brownish green and often have a yellowish belly. Their body shape is rounded so they wobble when they swim. The tail is noticeably arched and is about 3/5 of the tadpole's total body length. The body and tail have many small bordered black spots. Note that the spots are present on the dorsal fin but absent on the ventral fin. Larval period: Two to three years. Habitat: Large ponds, vegetated streams, vegetated coves of lakes. The tadpoles are often in the open and are readily seen. Confusing species: Can be confused with Green Frogs - look for dots on the dorsal fin and body shape (see below).	Photo: Scott Egan (Photo from Rhode Island) Photo: NS Museum of Natural History (Photo from Nova Scotia)

Drawing by Fred Scott

The information on this web page was taken from:

Tadpoles of the United States and Canada: A Tutorial and Key
A Virtual Exhibit on Canada's Biodiversity: Focus on Amphibians
The Canadian Amphibian and Reptile Conservation Network
A guide to frog egg identification and metamorphic timing
Cockran, C.C. and C. Thoms. 1996. Amphibians of Oregon, Washington, and British Columbia. Lone Pine Publishing. Alberta.
Gilhen, J. 1984. Amphibians and Reptiles of Nova Scotia. The Nova Scotia Museum. Halifax, NS.
Halliday, T. and K. Adler. 1991. The Encyclopedia of Reptiles and Amphibians. Facts on File Inc. New York.
Hunter, M.L. Jr., A.J.K. Calhoun, and M. McCollough. 1999. Maine Amphibians and Reptiles. The University of Maine Press. Maine.
McDiarmid, R.W. and R.Altig. 1999. Tadpoles: The Biology of Anuran Larvae. The University of Chicago Press. Chicago.
Petranka, J.W. 1998. Salamanders of the United States and Canada. Smithsonian Institution. Washington.
Stebbins, R.C. and N.W. Cohen. 1995. A Natural History of Amphibians. Princeton University Press. New Jersey.

All photos used with permission.