Early Spring Egg Masses

Before the trees have leafed out and obscured the brown tangles of understory, the early months of spring reveal hidden features across the forest's barren landscape.  White and pink wildflowers start to poke up through the leaf litter, attracting the season's first insects.  The stillness in the air makes the absence of migratory birds conspicuous, as the quiet forest awaits their jubilant calls.  Large mammals, like deer and coyotes, tread the same well-worn paths winding in thin lines up and down the wooded slopes. They have managed to eke out a living on this sparse landscape for months.

It is easier to navigate the rolling hills and ravines this time of year.  Little things, left behind by the fall and winter, now stand out.  White, sun-bleached bones—the vertebrae of a deer or the empty shell of a box turtle—linger eerily in the leaf litter.  The signs of other humans—an old beer bottle or an abandoned glove—reveal that you are not the first to venture this way.

These transitional months also reveal larger structures: the rusted out hood of a truck, or the crumbling outline of bricks where a cabin once stood.  As Carl and I hiked, the huge maw of a long abandoned train tunnel loomed into view.  Decommissioned over a century ago in 1916, the route of the old Cincinnati, Hamilton & Dayton Railroad still snakes through the forested ravine bottoms.  The tunnel is lodged out of view of most hikers, sitting in a state of decay among the hillsides.  I was amazed to see this forgotten chunk of Ohio's history, still standing as a token to the past.

A Jefferson salamander egg mass.

The early March morning was between 39 and 40 degrees Fahrenheit—right on the cusp of frog calling weather.  The brisk air felt full of potential.  With a little luck on our side, I imagined we could find anything.  Spotting the year’s first surface active garter snake or the first batch of salamander eggs feels like stumbling upon a secret.  For that moment, just you and the frogs know that life is beginning to stir.  Herps are true harbingers of spring. Following the subtly rising temperatures, salamanders start moving, frogs start calling, and egg masses start popping up everywhere.  

Carl had picked out a series of small pools on his topographic map for us to survey.  This spring was turning out to be rather fickle.  Temperatures had briefly risen into the mid-seventies only to plummet back into snow and ice days later.  We weren't sure what would be active, if anything.

The first small pond we arrived at was nothing special.  Around 15 feet across and almost perfectly round, it was clearly an old man-made farm pond that had been reclaimed by the forest.  The sparse shoots of reeds and gasses that grew around its edges were still brown and bent.  Spring warmth felt a long way off.  

As I stood on the bank, I noticed dozens of speckled, floating blobs attached to the woody reeds.  Most of these blobs were about the size of my fist, but a few were even larger.  They sat singly or in aggregations, revealing that just nights before, countless mole salamanders had migrated here to breed.  I scanned the shallows in case any adult salamanders had been left behind, but the cloudiness of the water obscured everything below a few inches.  By now, most breeding adults would have already returned to the woodlands or buried themselves in the muddy banks.    

A large group of spotted salamander eggs. Note the white egg mass in the center.  Front left there is also a wood frog mass.

Carl leaned forward with his dip net and gently scooped up two of the gelatinous balls.  One was an opaque, milky white, like the glassy eyes of a dead frog.  The other was so clear I could see each of the tiny embryos developing within.  Carefully, so as not to drop the precious cargo, Carl placed the clearer of the two in my cupped hands.  

The egg mass didn't feel like anything I had ever held before.  There was nothing slimy or unsettling about it.  Instead of oozing through my fingers, it firmly retained its shape—splitting along seams between eggs rather than melting together.  Its weightiness reminded me of a water balloon threatening to slip out of my grasp with the slightest movement.  The circular embryos were evenly spaced, each with a little, glowing halo of protective jelly.  As sunlight defracted through its multiple layers, the egg mass seemed to radiate its own light and warmth.  It was really a beautiful object. 

A spotted salamander egg mass.

Composed of around 50-150 eggs, these large masses would develop into larval spotted salamanders (Ambystoma maculatum) in 4-7 weeks.  Why some spotted salamander eggs are opaque while others are clear isn’t fully understood.  This variation is determined by the presence or absence of a glycoprotein found in the outer jelly layer.  In Ohio, there doesn't seem to be any fitness advantage for clear versus opaque eggs.  Some research, however, suggests clear egg masses may contain fewer eggs with a higher hatching success rate.

Red-spotted newts feasting on developing spotted salamander larvae.

As we moved down the pond, Carl came across a cluster of eggs that had turned yellow with a type of symbiotic algae.  This algae helps speed up the embryo’s rate of development, improving the larvae’s chances of survival.  The protective jelly that surrounds each egg was starting to break down, revealing the more developed embryos within.  Two red-spotted newts (Notophthalamus viridescence) feasted happily away on the not-yet-motile larval salamanders (a Type I Functional Response for my ecology nerds out there).  For newts and other cannibalistic amphibians, salamander eggs are an all you can eat buffet.  Requiring no time or effort to catch, the number of eggs a newt can eat is only limited by stomach size and speed of digestion.

Of the give or take 50 egg masses in the pond, most had been laid by spotted salamanders. Carl identified a few smaller masses, composed of only two dozen embryos, as the eggs of Jefferson Salamanders (Ambystoma jeffersonianum).  Despite adult Jeffs growing to similar dimensions as spotted salamanders, their egg masses are consistently smaller and hatch within a month’s time.

A raft of wood frog eggs.

While mole salamanders typically breed in fish free ponds and vernal pools, many of Ohio’s amphibians aren't picky when it comes to shallow, temporary water.  Road side ditches and tire ruts can provide breeding habitat for many salamander species and their froggy relatives.  

As we hiked back towards the vehicle, we stopped to examine a flooded patch of trail filled to the brim with egg masses.  Female wood frogs (Rana sylvatica) breed earlier than any other ranid frog in Ohio.  Eggs are laid in a communal raft that can span several meters (each female produces well over a thousand eggs).  These large aggregations can be distinguished from spotted salamander egg masses by the lack of a gelatinous sheath around the eggs.  Tadpoles become free swimming in as little as 1-2 weeks.

Three mountain chorus frog egg masses.

Having developed my search image for eggs, I realized we had overlooked a few tiny masses in the cloudy tire ruts next to the truck.  Similar in size to the egg masses of Jefferson salamanders, these eggs belonged to a specialist of tiny, shallow pools and roadside ruts: the mountain chorus frog (Pseudacris brachyphona).  These chorus frog eggs were covered in a thin layer of sediment and would take only a week to ten days to hatch. We scanned the pool, hopeful that a lingering adult might be within grasp.  These small treefrogs are a real challenge to spot, and often stop calling at the first sign of inquire. 

Carl dip netting for mountain chorus frogs.

On our way to the next pond, I thought I heard the deep, throaty croak of a mountain chorus frog coming from a series of roadside ditches.  We immediately pulled over to investigate.  While Carl sampled the water-filled ruts with his dip net, I scanned the shallow pools for eggs and amphibians.  I was met with a surprise floating just centimeters below the surface: an egg mass made up of a single strand, tightly coiled into a series of corkscrews.  I knew immediately these eggs belonged to an American toad (Anaxyrus americanus).  What was so surprising about this find was the fact that American toads don't typically start breeding until late March or early April.  These eggs were nearly a month early!  This spring was turning out to be very peculiar indeed.

American toad eggs.

The second pond we arrived at was more picturesque than the first.  Green shoots were beginning to push up through its murky water.  We found more floating spotted salamander egg masses as well as adult frogs.  Several spring peepers were beginning to call as the day warmed.  One frog made a more distinct gck-gck-gck call.  To my amusement, Carl imitated the call in hopes of locating the chorus frog, but his dip net only managed to snag a few peepers, tadpoles, and a red-spotted newt.  The mountain chorus frogs remained illusive.

We hiked along the old railway, following the calls of chorusing frogs.  Just as we reached a series of vernal pools, a large four-wheeler plowed its way through the mud and water towards us.  We watched from the sidelines, grimacing as our frogs fell silent as their habitat was torn to shreds.  Thankfully, the four-wheeler avoided the largest and most prominent of the vernal pools (sparing at least some animals, although we did find several egg masses that had been flung into the woodland).

As I got ready to dip net one of the pools, a frog leapt from the bank.  Frantically, I plunged my net under the spot where the amphibian's ripples had disappeared.  The net came up empty, but the disturbance coaxed the frog back up to the surface.  As it hung in the water, I could tell it wasn't a spring peeper.  In fact, it wasn't just one frog, but an amplexing pair of mountain chorus frogs.  I scooped the floating pair up easily.

With frogs in hand, I was able to examine my catch more closely.  I was immediately impressed by the size of these chorus frogs.  They were certainly on the larger end of the spring peeper scale, and well over twice the size of a western chorus frog.  Still only an inch or so in length, their bumpy, gray skin reminded me more of a small gray treefrog than their closer peeper relatives. Their two deep orange eyes were lightly masked and their legs and back were marked with subtle, dark striations.  Mountain chorus frogs are found only in the southern portion of the state, where they are extremely scarce during most of the year.  They emerge during the spring breeding season to call and breed, before disappearing again by early summer.

Soon, the egg masses we had discovered would start hatching, and the still pools and roadside ruts would be transformed into a bustling ecosystem of baby amphibians.  Carl and I had plans to return to some of these pools in the future to monitor their progress.  I always enjoy documenting the various life stages of Ohio's reptiles and amphibians.  Observing an organism during all parts of its life cycle is key to understanding its natural history.  There is no substitute for getting out into the woods and studying the real thing.

Until next time and keep living the field life,
Ryan B. Wagner