The amphibian cruise

Nature bummin’ with Kirk Gentalen—

Wood frog

Migration is pretty cool, and the “moving from one place to another” as a survival behavior can be observed across the spectrum of the animal kingdom. From the incredible journey of Monarch butterflies, to American lobsters that seasonally move to and from deeper waters, or the springtime return (and subsequent fall departure) of brilliantly patterned and melodic Warblers—migration and its associated lessons are well represented on the St. George peninsula.

As far as the category of “late March, relatively warm, rainy night” migrations is concerned though, it’s amphibians that rule! On evenings when temperatures first reach a toasty 40 degrees (or higher), and the ground is wet with rain, wood frogs and spotted salamanders act as if a starter’s pistol has declared that a race has begun. With frogs hopping and salamanders cruising (I think that’s what they do), a somewhat chaotic scene can appear “out of nowhere” as they make their way through the woods, with some populations even crossing roads to vernal pools in hopes of breeding. A race worth running! When the timing is right, these are the nights that family drives were made for.

Vernal, or “spring” pools are bodies of water that “go completely dry” on enough of a regular basis so fish and other predators can’t establish populations within. The fewer predators, the safer life is for eggs. Young spotted salamanders and wood frogs are so reliant on these pools they are considered “vernal-pool-indicator species.” On the flip side, a pool drying up also means there is a limited time for eggs to be laid and for juvenile frogs and salamanders to mature before “the well runs dry” so to speak. Seems like a good strategy to get to the pools as quick and early as possible.

Spotted salamanders

In theory, most to all vernal-pool amphibians in an area will migrate the same night from their overwintering burrows to these temporary pools. This kind of strict schedule is, however, seldom a reality as differences in amounts of snow cover, in rain starting times, and in the distances individuals have to migrate can stretch a population’s migration length from a single night to a week or more. Some individuals go to impressive lengths to get to their vernal pools­­—spotted salamanders are known to travel up to 815 feet to get to a pool, and wood frogs have been documented migrating over 1500 feet! That’s more than some people move in a day and these amphibians are tiny!

And so every year in late March we keep an eye on the weather in hopes of predicting and observing a part of this mass amphibian migration. This year has been no different, and on the last few nights of March the conditions for amphibian migration were achieved—wet, warm and rainy! And even though there was more than a foot of snow blanketing my back yard and other places, I got in my truck, turned up the Iron Maiden music because energy is key on drives like this—and hit the roads for my first amphibian cruise at about 10:30pm. I had given the rains half an hour to soak the road but apparently it wasn’t enough time to melt much snow and I saw no migration on the roads at first. Wood frogs and spotted salamanders have no problem crossing snow, they just have to get out of the ground first!

One wood frog road crossing that I have watched the last few springs happens to face south and on this night the ground on both sides of the road was completely void of snow. To my pleasure, a handful of wood frogs greeted my headlights with a hop or two as I pulled into the “zone.” My goal was to snag a few—for educational purposes—and then “help” the others finish their crossing instead of being crushed by other cars. Catching frogs is an art form that often requires patience and stealth. But on a 40-degree night no art form is necessary as the frogs—being the coldblooded critters they are—were barely moving and barely awake. Simply walk up to ‘em and pick ‘em up—getting your hands wet first! These are good times.

The rest of the drive was quiet on the amphibian front, but the rain continued through that night and most of the next day, melting a huge chunk of the remaining snow. The roads did go dry over the course of a sunny afternoon, but fortunately the rains came back late and I found myself doing the amphibian cruise at 11pm. And what a difference a night can make! The snow was still patchy, but things had opened enough so that wood frogs and spotted salamanders were able to get their migrations going. I observed both species at several road-crossing locations, but the overall number of individuals felt low—giving the impression that there would be another night (or two!) of movement before things are over. Twist my arm and I’ll go back out! Hopefully with the family next time!

PHOTOS: Kirk Gentalen

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