Amphibian Migration 2017

It seems as though the seasons come and go in a flash, and even more so in temperate regions. The longest season in the mind of a herpetologist tends to be winter, but I think many of us have acknowledged a deviation from this trend in 2017. Particularly, reptile/amphibian enthusiasts of the northeast have experienced what seemed to be an expedited winter, relatively mild with little to no snowfall. In addition, temperatures in some of the colder months such as February have been uncharacteristically high, sometimes peaking into the low 70's. As a result, the emergence of our herpetofauna has been in some ways premature.  Eastern Milk Snakes basking in warm winter sunlight, Eastern Hognose surfacing months before they're "supposed to". It's been a perplexing onset and conclusion of mid-winter, but you won't hear many of us complain. Although, I think the troublesome echoes of climate change break up our bliss from time to time. I think that's a discussion for another day.

For one group of amphibians it's been business as usual. Every year in late winter to early spring, the forest floor of mesic woodlands bursts into life in the form of awakened vernal pool obligates. Members of a few amphibian families and genera emerge from underground (or leaf litter) refugia and make their way to temporary pools where the propagation of future generations takes place. We see, and more often hear a member of the Hylidae (Treefrog) family get the festivities started as they "peep" from emergent vegetation. Of course I'm referring to the aptly named Spring Peeper - Pseudacris crucifer. These tiny chorus frogs call in concert, broadcasting their reproductive viability to nearby females. Morphologically they're characterized by possessing a prominent "x" in their back, which can be perceived as a cross; hence the specific epithet crucifer. Here's a look at one (of many) I escorted off a potentially dangerous highway: 

One other frog participant of the amphibian migrations is considered to be a vernal pool obligate. It's known as the Wood Frog - Lithobates sylvaticus, and belongs to the Ranidae (True Frog) family. There are few species more hardy than the Wood Frog as they've remarkable abilities of withstanding freezing temperatures. There are a number of videos showing their ability to freeze, thaw and recover, and I encourage you to check those out. It's a small to medium sized frog with a characteristic dark "mask" on its face. They vary in their coloration from dark brownish-gray to tan and even shades of red in some instances. They're among the first amphibians to surface and make their way to ephemeral (temporary) pools where their offspring can develop devoid of any threat from predatory fish. Here's a look at some of that color variation:

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Interestingly, I had a first experience this year relative to the amphibian migration. I assumed for years that at the conclusion of the breeding frenzy amphibians would wait until a night with ample rain to leave their pools. However, on the morning after the first wave of amphibians, while standing along the bank of a vernal pool I started to hear short intermittent disruptions of the leaf litter. I periscoped my surroundings and eventually caught sight of what was moving about. All around me, Wood Frogs were hopping out of the pool and up the steep bank. I found it interesting for a few reasons. For one, it was the first time I witnessed frogs leaving a breeding pool, as I tend to catch them when they're on their way to them. Second, there were very few clouds in the sky and the sun was radiating rather strong. It didn't seem like a good time for an animal at risk of dehydration to leave a saturated habitat. Lastly, what struck me the most was the fact that the frogs seemed to leave in unison. One minute the bank was quiet, seemingly devoid of life. But in an instant a slew of what must've been exhausted Wood Frogs emerged from the water to enter their upland habitat. Shortly after their departure from the pool male Wood Frogs began to call, which I thought was interesting. I immediately pondered whether or not the frogs leaving were females, but it remains a mystery. Here's one of many spotted leaping uphill: 

Both Spring Peepers and Wood Frogs, on occasion, share their migratory routes with a distant relative or two. The Yellow Spotted Salamander - Ambystoma maculatum may be the most abundant member of its genus here in Pennsylvania. They belong to a somewhat secretive family of salamanders, the Ambystomatidae, commonly called the mole salamanders. Their common name refers to their habitat of remaining underground in burrows for extended periods of time. Ambystoma maculatum is marked with brilliant yellow spots which can vary both in size and abundance. Some may lack spots entirely, causing them to resemble a species I'll get to in a bit. I had the opportunity to help a few across a dark road in northern Jersey one night in February. In the end I'd see about a dozen, which is much less than I'd usually encounter during the full onset of their explosive migrations. No matter the case, I really love these guys and twelve was plenty. Here's a look at one I photographed with my new camera set up: 

I could go on and on about Yellow Spotted Salamanders, as there's so much to be said about them. Perhaps I'll do an informational post on them in the future. However, what prompted and inspired me to write this post is what I'll leave you with. I've found that the inability to find certain species is a common plight among naturalists. I'm sure there are plenty of variables that go into that, such as knowledge of life history, knowledge of historical distributions, etc. It takes time to accumulate the tools needed to find elusive critters. On the same morning of the emigrating Wood Frogs, a familiar but technically unfamiliar amphibian was spotted trotting along the pool's periphery. It was submerged of course, but walking about for reasons I'm unsure. It's tail was laterally compressed like a crocodile, skin a non-descript slate gray. They call it the Jefferson Salamander - Ambystoma jeffersonianum: 

My history with these guys is kind of abstract. I found a few metamorphs during my first season as a field herper, and I'd seen some egg masses over the years. However, I hadn't seen an adult up until this point. This particular population is isolated on a mountain, so finding one via roadcruising wasn't an option. They tend to move before Yellow Spotted Salamanders do, and even migrate the pool when it's still frozen. Hence, timing the Jefferson Salamander migration can be tricky,  at least for me it was. I'd long suspected these alien like creatures were my favorite member of its genus and this interaction definitely confirmed that. Perhaps it's their habitat specificity (steep slopes in deciduous forests, upland from ephemeral pools), or the degree of difficulty finding them relative to other Ambystoma species in the region. Or maybe it's just their ridiculously long toes. The heart of it's range is here in the northeast, much like the Wood Turtle, and for whatever reason I've always had some sort of civic affinity for species endemic to this region. It was a pleasure to have finally met this species in it's mature form. 

That's all for the amphibian migration, for now anyway. I suspect the next warm spell and rain will cause some of these guys to migrate once more. The pool with the Jefferson sals and Wood Frogs already had egg masses for both species, so they're likely to be finished. Interestingly enough, I didn't see any Yellow Spotted Salamander eggs. They may have yet to migrate. Hopefully I'll be there when they do. Until then...

There's a world we can visit

-S.Harris