Identifying Amphibian Eggs in the Lowlands of Western Washington
By Chris Byrd
The breeding season for amphibians in the lowlands of Western Washington begins in mid-winter and extends into the spring depending on the temperature and moisture needs of breeding adults.
Adult amphibians breed in areas of still water that contain water long enough for full development of the larval into the adult form.
Movement to breeding areas typically occurs on wet nights with temperatures well-above freezing.
Many amphibians show site fidelity by moving to traditional breeding sites where the individual was born and breeding has been successful in the past. Some individuals will wander and colonize new sites.
Northern Red-legged Frog (Rana aurora):
Northern red-legged frogs breed primarily in February and March in the Puget Trough. The breeding behavior of northern red-legged frogs is typical of the genus with males establishing territories in breeding ponds via vocalizations and aggression. Females that enter the pond are grasped in amplexus (see image below) by the male. Fertilization is external as the male emits sperm onto the eggs of the female outside of the female’s body.
Unlike other Ranid frogs female red-legged frogs lay their egg masses separate from those of the other females.
Egg masses of red-legged frogs can be identified by the following characteristics:
1) The mass is about the size of a cantaloupe.
2) The mass is soft slipping through the fingers if attempts are made to lift from the pond.
3) Individual eggs have a wide jelly coat giving the mass the appearance of having fewer eggs for its volume than other species.
4) The mass is usually attached to submerged woody debris or aquatic vegetation.
5) Mass floats to the surface and spreads out near hatching time.
Oregon Spotted Frog: (Rana pretiosa):
Oregon spotted frogs breed in February and March in the Puget Sound lowlands. These are highly aquatic frogs. The breeding cycle of spotted frogs follows the pattern of other true frogs.
Egg masses of Oregon spotted frogs can be identified by the following characteristics:
1) Egg masses similar in size to red-legged frog masses.
2) Eggs laid in communal masses.
3) Egg masses often with tops above the water-line.
4) Thin layer of jelly on individual eggs.
5) Eggs appear tightly packed in the mass .
American Bullfrog (Lithobates catesbeianus):
American bullfrogs breed later in the spring as water temperatures increase. Male bullfrogs advertise with a distinct deep “jug-o-rum” call. The rest of the breeding cycle is similar to other frog species in North America.
Egg masses of bullfrogs can be identified by the following characteristics:
1) Sheet of eggs laid on the surface of the water.
2) Egg mass may appear frothy.
3) Eggs very small.
Pacific Chorus Frog (Pseudacris regilla):
The diphasic “krek-ek” advertising call of male pacific chorus frogs is one of the seminal sounds of the coming spring. Males hold aquatic territories that they defend with physical aggression and vocalizations from other conspecific males.
Females lay their egg masses on aquatic vegetation in shallow still waters. Pacific chorus frogs have fast larval development allowing them to use aquatic habitats that hold water only seasonally.
Egg masses of Pacific chorus frogs can be identified by the following characteristics:
1) Egg masses oblong in shape.
2) Individual eggs with a thin jelly layer.
3) More eggs per unit area than species with similar egg masses.
4) Mass soft and amorphous when removed from the water.
5) Attached to aquatic vegetation in shallow water.
Northwestern salamander (Ambystoma gracile):
Northwestern salamanders move to breeding ponds in February. Males spend more time in breeding ponds than females. Males leave their spermataphore (containing their sperm) on the bottom of the pond. The female will pick up the spermataphore with her cloaca and store the sperm until eggs are laid.
In the lowlands of Western Washington many northwestern salamanders breed in their larval form.
Egg masses of northwestern salamanders can be identified by the following characteristics:
1) Egg mass is firm.
2) Second jelly coat gives the egg mass a wavy appearance.
3) Eggs often laid on submerged woody material.
4) Egg mass with green coloration due to symbiosis with an algae
Note: Breeding neotenic salamanders (larval) lay eggs that are softer and laid on the bottom of ponds instead of on submerged debris.
Long-toed salamander (Ambystoma macrodactylum):
The breeding cycle of the long-toed salamander is similar to that of other Ambystomid salamanders such as the northwestern.
Egg masses of long-toed salamanders can be identified by the following characteristics:
1) Eggs laid in small masses or singly.
2) Egg masses chicken egg-sized.
3) Jelly coat thick on each individual egg.
4) Eggs look widely spaced within the mass due to the size of each egg.
5) Egg mass is soft.
Rough-skinned Newt (Taricha granulosa):
Rough-skinned newts can be highly aquatic sometimes spending most of the year in breeding ponds. Male rough-skinned newts grasp females entering the breeding pond in an amplexus position using both the front and hind limbs. The male then uses its enlarged tail to move her away from other males. Other portions of the breeding cycle are similar to other salamanders.
Egg masses of rough-skinned newts can be identified by the following characteristics:
1) Eggs laid singly in dense vegetation.
2) Jelly coat thinner than long-toed salamander eggs.
Amphibian Eggs: Concluding Thoughts
Identifying amphibian eggs can be a valuable addition to many wildlife conservation projects. It can also be a fun springtime activity for the whole family. I hope this mini-guide enhances your outdoor adventures!
Additional Resources on Amphibian Eggs:
About the Author: Chris Byrd is a core instructor at Alderleaf. He has been teaching naturalist skills for over twenty years. Learn more about Chris Byrd.