Late Season Peeping
Nature Bummin’ with MCHT Steward Kirk Gentalen
So-called “Spring” Peepers
The old timers say, “happens every ’tember,” and the old timers are right! After a summer of silence, some Spring Peepers start peeping again each September (or “each ‘tember” if you’re an old timer). You know Spring Peepers, the little tree frogs with the X on their back. Maybe you know them by their Latin name, Pseudacris crucifer. Maybe you know them by their peeps—they make an awful lot of racket in the spring, but I’ve only ever heard one person complain about their noise and I’m pretty sure I was joking at the time.
They don’t annoy anyone with their September peeps either (even me jokingly). In fact, for many they may be “peeping under the radar” as only a very small percentage of Peepers go for the “late season peeping”. And those that do peep tend to for short stretches, maybe just a handful of peeps at a time. So, it’s nothing like the deafening thunder released in Spring from a pool full of sexually charged male Peepers all peeping for mates. But some do peep in September, and just about every trail and preserve I visited last month had one or two Peepers peeping nearby.
We know why Peeper’s peep in spring, it’s to mate. At that time, their common name makes perfect sense. The peeping in spring comes down to a traditional tale of males yelling and females selecting—a classic in a lot of ways. Here’s what Thomas Tyning wrote about springtime Peeper calling and selection in “A Guide to Amphibians and Reptiles.”
Field researchers have determined that females are able to distinguish individual males by unique characteristics of the call and may be choosing mates based on criteria unknown to us at this time.
To which Wiki now adds: “Older, larger males tend to have faster and louder calls that are preferred by the females.”
Take Wiki for what it’s worth, but the frogs are mating in spring, and that’s the point. In September they aren’t mating, even though apparently some males may be interested. Probably some females too. And why not?
Day light length (DLL) and one of the two best solstices
Over the years, I’ve gotten into a habit of pointing in the direction of any late season peeping Peepers and asking out loud “why are you peeping?” regardless of whether anyone else was around. The frogs never answered, and the people nearby often look confused, but late season peeping has always got me thinking about the influence of changing day light length. Then again what doesn’t get us thinking about the ever-changing day light length and its influence on the world? It’s been this way for years. Alright, might be time for a little background info.
A major lesson I took away from my college Ornithology course (taught by that crossbill guy from two NBs back!) had to do with Photoperiodism, or the response of an organism to seasonal changes in day length. And it’s totally cool. Birds have photoreceptors which are specialized cells that detect light in their brains—in their Ventromedial Hypothalamuses to be exact (I’ll refer to this as “VH” from here on out). Birds are both thin-skulled and not-so-thick-brained as the VH is found as deep inside of a bird brain as possible. That’s right, the cells that interpret light and influence the major aspects of a bird’s life is as far away from light as possible. Must be really sensitive, I won’t make fun of it.
The VH reads the length of daylight and initiates gland activity and changes in hormonal levels accordingly. Take Winter Solstice (Dec 20ish) for example, where in the northern hemisphere, it’s the day of the year that daylight length (DLL from here on out) will switch from getting shorter and begin to increase in length. For birds of the northern hemisphere, it’s the beginning of physical and behavioral changes which allow for a slew of events such as molt, courtship activities, and migration. We are big fans of changes in DLL.
It doesn’t take long for signs of these changes to be seen. Come mid-January (three to four weeks after the solstice), I start to notice Black Guillemots from the Vinalhaven ferry that look a bit patchy as they begin their molt from non-breeding plumage (white) to their breeding plumage (hot to trot, jet black with white wings). Winter is just getting going and Guillemots are getting all primped up for courtship and potential breeding that is months away. As Ranger Perry used to say, “Look sharp or B flat”. And the loons are close to follow with their molt thing starting in February. All from the connection of an increased DLL and a photoreceptive brain. Ain’t nature cool?
The Other Solstice
Conversely, the other solstice (some call it summer) is the day of year when, of course, DLL starts to decrease in the northern hemisphere, triggering another set of changes for many northern hemisphere birds. As the days get shorter, birds prepare for overwintering and migration (or a little of both). They begin to pack on the calories as territories break down and form mixed age and species flocks. And there is usually a post-breeding molt tossed in there somewhere as well. Those photoreceptors are funky cool.
If you learn one thing from reading these Nature Bummin’ posts, please let it be that daylight length plays a major role in bird’s lives. Thank you.
A Pair of Equinoxes and the Other Solstice
So, with daylight on our minds (and on our Ventromedial hypothalamuses!) we return to Peepers peeping in the fall. Going out on a limb here, but unlike the Black Guillemots, Peepers in Maine are probably not as in tune with changes between the pre- and post-Winter Solstice day lengths. I say this because Peepers spend the cold months mostly frozen—frozen in time as only a frozen cold-blooded animal can. That’s right—when temps drop a Peeper’s liver pumps glucose into its blood system, and in as such, glucose then concentrates in a Peeper’s cells. To make room for the glucose much of the water within said Peepers’ cells is moved to spaces between cells, where it will freeze during the winter. This protects a cells content from ice damage and allows Peepers to tolerate temps reportedly as cold as -21C, (but -8 C is another limit that turned up), as they hibernate under logs, leaf litter or behind loose bark on trees. Now that is cold blooded.
They may not ever see the winter solstice, but mid-coast Maine Peepers would be aware of DLL status around all of the equinoxes, however, both in the spring and fall. You know the equinoxes – the two days a year at where the sun crosses the celestial equator, when day and night are of approximately equal length. These days are September 22ish and March 20ish. I have heard (and seen) Peepers a week or more before the spring equinox, but a lot start peeping in the three weeks after the equinox. This makes for a time frame of roughly March 10th—April 14 for Peepers to really get peeping—microclimates, thaw out, and other weather factors withstanding. Or is it not withstanding? Whatever.
The summer solstice—the day of the year with the longest day light length—can be found right between the equinoxes—June 20ish. In a way, DLL forms a carbon copy of itself at the same (time) distance from the solstice. For example, the DLL of June 10th (ten days before solstice) is about the same as DLL on July 1st (ten days after solstice). I call it a carbon copy because while the DLLs may match, the two days are going in different directions—in June the days are getting longer, where in July day light length is getting shorter. Man, I like thinking like this.
Now think of the equinoxes as calendar landmarks. With the Peepers, I was saying that in mid-coast Maine an observer might start to hear them two weeks prior to Spring Equinox, but certainly they kick in during the first three weeks after the Spring Equinox. (dually noted ad nauseum—there can also be a lot of weather factors that play a role in ‘on the ground’, year to year timing). That said—in our DLL carbon copy on either side of the summer solstice the two weeks prior and three weeks after the spring equinox corresponds/matches the day length of the three weeks prior to and the two weeks after the Fall Equinox. In other words—DLL wise mid-March to mid-April matches the month of September, (‘tember if you are an old timer). Makes sense to me.
So that’s what I’ve been going with for years—or maybe I should I say has satisfied my curiosity. I’ve answered the question I’ve asked a whole bunch of times—why are you peeping? It’ DLL. But I never knew if I was right, or even close to being right.
So, this year I did it
Not sure why things take so long to click with me, but after years of pointing and asking I finally decided I would see what others have to say on this subject. So, I searched ‘Why do Spring Peepers peep in fall?’ and the first thing that came up was this:
‘There are several hypotheses as to why these frogs are calling in autumn, but one has to do with environmental conditions. The shortness of the days, lower angle of the sun, increasing rainfall, and cooler temperatures are very similar to spring conditions when these frogs become active.’ (Beyond your Backdoor—Dec 9, 2020)
Boom! Drop the mic kind of moment. The world is similar in September as it was from mid-April to mid-March, in reverse chronological (going backwards time wise here—I need a carbon copy calendar!).
But then I kept reading (took me long enough again) and my mind was continuously being blown away (hope I’m not building this up too much).
Spring in mind, again
The column quoted above had a quote within it from one David Skelly, director of the Yale Peabody Museum of Natural History.
“These environmental cues may prod them into calling, since they undergo physiological changes during late summer and fall that will enable them to breed as soon as they become active after a long period of dormancy.”
Oh, my word. I think about vernal pools, about amphibian migration, about tadpole development, about wintering dormancy—I think about these things every year, all the time, constantly (two of these are exaggerations). But I hadn’t thought about frogs (and salamanders I bet!) getting ready for spring in the fall. Not getting ready for winter—not these sugary cubes of freezable amphibians—no need for that. Find a semi-warm spot, sleep, and wake up randy and ready for action—that’s a Peeper’s winter.
Then I found this in the Burlington Free Press, Michael Caduto, Outside Story, Sept. 24, 2016
[Peepers] need to be physiologically prepared for calling and breeding in the spring as soon as they thaw out. If you consider that their body temps may be below freezing when they are in the leaf litter during the winter, they are essentially in cold storage. They have to be ready to breed when they enter the leaf litter. As far as their bodies are concerned, they are only minutes away from breeding when they shut down in the fall.
— Jim Andrews, adjunct assistant professor in the Rubenstein School at the University of Vermont, and Vermont’s go-to ‘expert on all things herpetological’
I’ve just read that quote for like the 8th time and each time I find myself saying—this is so interesting. Never thought of it like that, but it totally makes sense (of course it does doofus!). Caduto then dropped this little nugget about physiological changes.
Research into the reproduction of the Spring Peeper, which was published in Herpetologica, reveals that although ovulation won’t occur until spring arrives, the stage is indeed set in autumn for the next mating season. Male sex organs develop from late June through early September. By the time Peepers are ready to hibernate, their sperm has matured. Autumn females have already formed eggs for the next breeding season; these are nearly two thirds the size they will ultimately become in the springtime.
— Michael Caduto, Sept 24, 2016
H.A.T. – How about that.
Well, well, well—kinda sounds like Peepers spend much of their lives focused on spring—getting ready for the season or actually being in season. And who can blame them?
You can probably guess which part of the last quote catches my eye every time I read it. It’s the time frame of ‘late June through early September’. Now, there are undoubtedly many factors involved, so it could be coincidence in timing but late June to me means ‘after Summer Solstice’ and we all know what that means (ugh, not again!)—shorter DLLs! It’s understood and (seemingly almost entirely) accepted as fact that Spring Peepers are influenced by environmental cues—so couldn’t a change in DLL—as well as angle of the sun, temps etc.—likely cue them to begin development sexually? Would it be correct to look at a Spring Peeper’s reproductive/life cycle as beginning with the shortening of the DLLs? Spring Peepers’ life cycle in Maine starts in June?
I can’t find anything on the potential connection between shorter DLL and Spring Peeper testicle development (that’s a good one to have in the memory of your favorite search engine), but just the thought of it—and of amphibian sexual development in the fall—turns the calendar upside down and shakes it a little for me. But this would make the common name “Spring Peeper” correct if their “spring” has already started by September when they start peeping! They truly are Spring Peepers!
Soooo, why do they peep in the fall again?
One article called Peeper late season peeps a “tease”, but I don’t think that term nails it. There is no teasing for the individuals involved—those dudes are ready. Maybe a teaser for the nature observer who hears it—a little “ha, ha, you’ll have to wait till Spring”. But that would make Peepers annoying and there is no need to start complaining about them now.
I do wonder if the select males that peep in September aren’t wasting (sexual) energy that would be best used after the thaw. A little too excited maybe? Or are they just that much readier come spring? How can you study something like that? Is it possible? While we are at it—what about birds that breed in North America but overwinter south of the equator? Wouldn’t it be the shortening of DLL (our winter solstice is their summer solstice) that initiates physical/behavioral changes associated with mating? And is it confusing for a bird brain to go across the equator—let’s say in March and April—to have DLL suddenly increase? Man, there is a lot going on here…
But hey, Peeper’s peep because they can. They peep because they feel like it. They peep because they are ready. They peep because March is only seconds away when you are cold blooded, and temps start to head towards freezing. They peep because of changes in and similarities between DLLs, and I love that day light length has something to do with all this. So many natural things to be at the mercy of in this world—“tides” stick out as a major one, one’s intestinal fauna is another—but day light length is right up there. Feels better than being at the mercy of intestinal fauna, if you know what I mean?
Seasonal perspectives and generalizations.
Some people love spring for all its green and birthiness as much as they love fall for its crisp days and decaying leaves. Common thread here is change, which is good because change is always happening. Changes in seasonal perspective can be a shock to the system, especially when you find out that a Spring Peeper’s spring doesn’t really start in the spring. The classic “Fall” perspective—full of getting ready for the winter, decay, declining temps and soup—has some birthiness to it as well, and not just with mushrooms releasing spores—their next generation. We’re talking frog egg and gonad development here, serious stuff—and Peepers aren’t alone here—Wood Frogs are on a similar schedule! But perspective changes, yes, we are always ready for them, for personal growth.
Purple and white asters are in bloom now that it’s colder, and rumor has it that the royal shrubbiness Witch Hazel doesn’t bloom until temps drop below 45C. Heck, Skunk Cabbage grows in the winter, melting any snow in its way and snow fleas are just one of several/many species of insects that are active on snow. The world is full of exceptions to the rules, which is why, I guess, they are rules rather than laws. Generalizations can make for good rules of thumbs.
That said, and I’ve said it before, and I’ll type it again—generalizations are stupid. This in itself is generalization, of course, thus making it a joke and not a very good one at that (the uncensored version is better). I’m probably not alone on this, but I often don’t realize the exceptions to the generalizations that my perspective might be (at least) partially based on. That is until one smacks me in the face and rocks my world. And that’s a good smack, one that often starts a train of thought down a new path. Sometimes those smacks are called epiphanies, (or ‘phanies if you are an old timer). We are “fannies” of these.
See you out there.
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