I posted this a short while ago and it's worth putting back up. Somebody else, I'm sorry but I forget who, posted a great guide to identifying lungless salamander larvae. I'm really hoping he has a backup to post. I made some edits to this based on feedback which were not backed up and I'm happy to make changes or improvements people suggest.
Ok northeasterners, I hope this helps somebody! Now that many of the early spring amphibians have ended their migrations to wetlands, bred, and in many cases moved back uphill, the time has come to get into the field and keep track of egg masses. This time of year up until about the end of May (this far north anyway) there are only a handful of mass-laying species we have to worry about:
Northern Leopard Frogs
In this post I will not be dealing with mid-summer breeders such as Bullfrogs and Green Frogs, or species that do not lay noticeable egg masses such as Eastern Newts, Blue-spotted Salamanders, or Spring Peepers, etc, which all lay individual eggs or groups of 2-3 eggs attached under leaves and debris. Please note that old egg masses that have hatched out or are about to hatch may be tattered, torn, or completely separated into a film.
Let's start simple. Frog eggs vs. salamander eggs. Telling the difference between the two is quite easy. Frogs lay individual clear eggs with a visible embryo contained within each egg. With frogs, the outside edge of the egg mass is made up of the eggs themselves. Salamanders take it a step farther and coat the entire egg mass with an additional layer of jelly, presumably as protection from predators such as newts. These two photos demonstrate the difference clearly:
Frog eggs. Notice that you can easily see the contour of each individual egg on the outside of the mass.
Salamander eggs. Notice that there is a layer of jelly, in this case about a finger-width wide, surrounding the mass of eggs.
And the two together:
Now we'll go down the list.Wood Frog
Wood frog egg masses are pretty easy to identify. You would expect to find Wood Frogs breeding in ponds, vernal pools, and marsh edges in or near forested habitat at varying elevations. A typical egg mass can have between 500 and 2000 eggs. The embryos start out black on top and white on the bottom, as do most open-water amphibian eggs, but as the embryo develops into a tadpole the white is lost. A fully-formed mass that has been in the water for a day or so is about the size of a softball and the clear space between the embryos and the margin of each egg is many times greater than the width of the embryo (see the first photo posted).
At a glance, Wood Frog egg masses underwater will look something like this:
Often, groups of Wood Frogs will lay their eggs in close proximity, usually around emergent vegetation:
Sometimes amphibian eggs can get an opaque hue to them. In Spotted Salamanders that is a genetic trait but I do not know for certain if that is true for Wood Frogs and other amphibians as well.Northern Leopard Frog
Leopard Frog eggs look a lot like Wood Frog eggs with a couple key differences. The embryos are about the same size but the eggs themselves are much smaller and tighter. The clear space between the margin of the eggs and the embryo is usually the about the same thickness as the embryo itself. Because Leopard Frogs lay more eggs per mass than Wood Frogs (2000-4000) but the eggs are much smaller, the entire egg masses end up being about the same size (think baseball-softball).
Leopard Frogs typically lay their eggs in lake and river flood planes where sedimentation and silt can build up pretty quickly. It is not uncommon to find them covered in a thin layer of matter:Pickerel Frog
If you can identify Leopard Frog eggs you can identify Pickerel Frog eggs. The egg masses are almost exactly the same except instead of the eggs being black on top and white on bottom, they are brown on top and yellow on bottom. Pickerel Frogs are usually higher in elevation as well.American Toad
Where I live, the American Toad is the only frog that lays its eggs in a long string. A single strand could have between 2,000 and 20,000 eggs depending on the size of the female.
I've never seen Fowlers Toad eggs and don't know if there is a good way to tell them apart. At least I'm being honest. If you have photos or ID tips, post 'em!Spotted Salamander
Spotted Salamander egg masses are made up of about 50-250 eggs, can be as large as a grapefruit, and are very dense/firm. Usually they are laid in ponds, vernal pools, and marsh edges without fish. If you pick up a Spotted egg mass it will usually hold its shape in your hand. Eggs are usually attached to sticks, branches, and vegetation below the surface of the water.
Even as the egg mass ages and the embryos develop you can see that it is firm and continues to hold its shape when pulled from the water.Jefferson Salamander
Pure Jefferson Salamander eggs are laid in masses of 20-30 eggs but females usually lay multiple masses. Sometimes masses are laid in a line down a single stick and, once they swell with water, may fuse into one another and appear to make up a single mass. The masses closely-resemble those of Spotted Salamanders but, in addition to being much smaller, are not firm. If you pick up a Jefferson mass the eggs will run through your fingers or break off the stick before even making it into your hand.
In the above photos it almost looks like some of the eggs are about to fall right off the stick. Below you can see that the masses flatten out in my palm. The below eggs may be hybrids, I'll explain more about that next.Jefferson Salamander hybrids
Hybrids between Jefferson and Blue-spotted Salamanders exist. The two species cannot breed with one another however a hybrid line of mostly-parthenogenic females can breed with either pure species. It's a very complicated subject that I'd be happy to talk about in more detail in a different thread. Hybrids more closely-related to Blue-spotted Salamanders will lay individual eggs or small clusters of eggs under leaf matter. Those closer to the Jefferson Salamanders will lay egg masses that basically look like those of pure Jefferson Salamanders. Hybrid egg masses, however, usually have a hi proportion of nonviable eggs that do not develop. The dud eggs are usually gray and swell up quickly. The gray swelling is caused by the water mold saprolegnia. Saprolegnia can be seen in amphibian eggs of any kind but it is very common in Jeff/Blue-spotted hybrids. Below is a photo of an older hybrid egg mass. Do not take note of the yellow color, that is just a function of the age of the mass (see the last spotted salamander egg mass photo for another example of an older mass).
This is a rather extreme example, but out of about 30 total eggs, only 3 or 4 seem to be developing. Usually, according to my anecdotal observations, the ratio is closer to about 50/50. There are reasons for the nonviability that a genetics friend of mine recently explained to me. I fear repeating it here would fry a few brains.Final Notes
Many people are blown away at how large egg masses are relative to the size of the animals laying them but at one point, they had to all fit in there somehow. The answer is in the water. Eggs, when the are first laid, have very little water in them and there is almost no space between the embryos and the margin of each egg. Take a look at these two photos taken recently:
Immediately after leaving the amphibian the eggs start to take on water and quickly swell up to many times their original size and weight.
This post is limited currently to Vermont spring breeders. If you would like to add to the collection to increase the annual and geographical range then please post photos and, for new species, descriptions would be great because I won't know what the heck I'm talking about.