Friday, April 19, 2019

A Short, but Dramatic Performance

Did you catch it this year? It’s a short, but dramatic one-act performance, and there’s not much advance publicity.

Wood Frogs – the earliest amphibian song of the spring. There may still be ice in some corners of their vernal pools, but unnecessary delay is not an option. Their vernal pools are beneficial to tadpoles because there are no fish present to eat them. However, these pools may not hold water year round. Males fertilize eggs as the female releases them, and then the tadpoles must hatch and mature before the pools dry up. It’s all quite urgent. 

Wood Frogs are forest dwellers, not surprisingly, and they live in solitary silence. As you may know, they can actually freeze during the coldest times in winter. Glucose replaces water that is drawn out of their organs and into their abdominal cavities so their organs are not damaged. It takes a little time to “thaw,” but when the process has completed, they can take to the stage.

Males respond to the early spring urgency by pouring in from surrounding woods to the vernal pools, and females follow shortly thereafter.

Males promptly begin calling, or “advertising.” I refer to these as "songs," but the proper term is “advertisement calls” - and advertising  is exactly what they are doing.

It’s an amphibian cacophony. The water bubbles and ripples with frogs, each attempting to out-sing the others. Their performances intensify as females arrive, and the chorus can be heard before the stage is even visible.  

So each spring I compulsively watch the weather forecast and balance that information against my academic schedule and all those other necessities that adult humans need to address…and hope there will be a point of convergence.

I’d heard and recorded Wood Frogs singing with Spring Peepers and a large chorus of Western Chorus Frogs at The Wilderness Center on March 24th, but that’s in the southeast corner of Stark County near the Wayne County line. 

We only had to wait a little longer up here by Lake Erie.
I hurried to the wetland area at North Chagrin Reservation’s Wilson Mills trailhead on March 27th, as conditions seemed promising. Before I even reached the water I could hear that my guess was exactly correct this year! 

Not only could I hear Wood Frogs, but to my surprise, soon I could even see them! It wasn't just the usual part of a head or some eyes above the water, but the actual frogs. 

I went back after dark on the 28th and again on the 29th. More frogs were calling.

The marsh is on either side of the dirt trail, and it’s possible to get close to the frogs if one doesn’t mind sitting and kneeling on the ground. I was able to study their behavior in greater detail than I have in the past, as I can’t generally get close enough without the frogs simply going silent. Maybe I appear to be some kind of large, awkward wading bird with plans to eat them.
But they quickly determined that I was too slow and clumsy to be a threat to anything, and they generally ignored me. Some came right up to the edge of the water as if attracted to my flashlight. 

People often describe the Wood Frogs’ calls as sounding like quacking ducks. Do they? Two Mallards decided to add their voices to the Wood Frog chorus when I was recording. The Mallards’ calls are a little lower in pitch, but there’s a definite similarity in tone quality.
Because the water was shallow, I could even see them underwater, enabling me to observe how their behavior corresponds to their calls.

The single “quack” call is typically made when the male is in one place. He may move, then begin calling again. The cacophony results from multiple males calling at the same time but with no synchronization, unlike the back-and-forth of Western Chorus Frogs. 

I was finally able to observe the paired vocal sacs on the sides of their heads. They inflate and deflate quickly to make the emphatic “quack” call.

But I knew there were times I’d also hear a rapid series of calls from an individual male. What did that communicate? Since I could observe them more closely, I could see that consecutive calls accompanied the male swimming after another male or defiantly approaching one that had gotten too close.

Even if the frog himself wasn't quite visible, I could see the concentric circles of the ripples he generated during the confrontation.

I didn’t witness the details of male interactions with females, as there were generally a number of noisy, agitated males in the vicinity. When males and females were joined in amplexus (when the male holds onto the female from above and fertilizes the eggs that she releases) they generally were silent. 

A male might occasionally call if another male tried to break apart the amplexus bond. 

But in a week or a little longer, the excitement was over for another year and the Wood Frogs silently returned to the forest. Consider yourself fortunate when you spot one now, as their colors blend impressively well with the forest floor and low vegetation. 

As spring progresses, Spring Peepers and Western Chorus Frogs will still be singing as the Wood Frogs depart, and Leopard Frogs and Pickerel Frogs will begin calling shortly thereafter. Green Frogs and American Toads follow, finallyjoined by Bullfrogs and the beautiful Gray Treefrogs.
But the Wood Frogs are a voice of spring’s first challenge to winter: urgent, dramatic, and so welcome. 

Wednesday, February 13, 2019

Annual Promises to Myself

(North Chagrin Reservation's Rogers Road field, 8-18-18. .He's probably a Forbes's 
Tree Cricket but I can't rule out Black-horned Tree Cricket. Why? Read on.)

This is not about New Year’s resolutions. It’s about those promises we make to ourselves when we plan what we really want to explore and study in the coming year’s field season. I keep more of these than I ever did with New Year’s resolutions.

In 2018, I kept a promise I made to myself at the end of the 2017 field season: that recording and documenting the look-alike Forbes’s Tree Crickets and Black-horned Tree Crickets would be my primary 2018 focus as soon as these two species began to mature in early August. (Regular readers of this blog know that I've been studying these tiny, but impressive singers for several years now.) 

I'd tried documenting them as best I could while doing surveys of all the other species of singing insects I might find. I obtained considerable information, but also learned that I needed to focus very specifically on these two cricket species if I were going to get as much information as possible toward sketching out a map of where each species  and both species are found. Singing insect season isn’t really that long - especially those magically-warm nights that are so excellent for insect song. So through dense blackberry tangles and thick stands of goldenrod taller than I am, I kept that promise to myself this past year.

The 2018 plan

I would record crickets in new NE Ohio locations. In addition, I would also revisit other sites where I’d recorded previously but felt my accuracy and sample sizes could improve.

I did indeed return to some of the places where my previous sample sizes had been very small, and I recorded more crickets there. If I wasn't entirely convinced of the accuracy of the temperatures I’d noted at the time – usually because of sunlight interference - I returned to increase my precision. 

Temperature is such an important factor! The difference between these species can be determined by how many wing strokes per second there are in songs recorded at a given temperature. Black-horned Tree Crickets will have fewer wing strokes per second than Forbes’s at the same temperature. It’s difficult to hear the difference, but easy to see on a sonogram. 

Sunlight had been a annoying problem. At the same air temperature, a cricket singing in the sun is warmer than a nearby individual in the shade. His song will have more wing strokes per second, possibly resulting in an inaccurate identification of the species.

The difficulty is eliminated at night. All I need to do is put my thermometer probe as close to the singer as possible  - ideally on his exact leaf if he'll permit it - and note the temperature. Getting as much data as possible after dark is ideal, and a very overcast day is a reasonable option as well

I consistently obtain that essential temperature for every individual I record. Even at night, the temperature at the top of the goldenrod may be warmer or cooler than farther down the same plants. I can't be certain of the species just by ear (though I'm getting closer), so I initially identify them only by the genus name, "Oecanthus," and the individual's number in the list of recordings. The Frohring Meadows individual in the recording below was a Forbes's, as were all the others I recorded at this Geauga County park in 2018. However, I labeled them by species only after reading their sonograms. 

I’ve been adding to my Google map of northern Ohio Forbes’s and Black-horned Tree Crickets each year. 

Here’s the link – you can see the details and specific information for yourself. The purple pins are the Forbes’s, the turquoise are the Black-horned, and the orange represent where I found both living together. (A pale purple pin means overwhelmingly Forbes’s and pale blue represents overwhelmingly Black-horned.)

As soon as the first Forbes’s and Black-horned Tree Crickets of 2018 began to sing in early August, I was ready.

Lorain/Erie county line

 Which species is he? Keep reading - he was at Wolf Run Preserve.

Dr. Jim Bissell, Curator & Head of Botany and Director of Natural Areas at the Cleveland Museum of Natural History, strongly encouraged me to take a look and listen for the singing insects at Wolf Run Preserve on the Vermilion River. This river edge preserve is located on the boundary of Lorain and Erie counties not far from Lake Erie. I have less information on Lorain County that the other counties in the Greater Cleveland region because night access has seldom been available, so this was certainly an intriguing idea. 

Almost every one of the look-alike tree crickets I’ve found along and close to Lake Erie from Ottawa National Wildlife Refuge all the way east to Lakeshore Reservation in eastern Lake County has been a Forbes’s Tree Crickets. I expected these would be as well. Still, I recorded 11 individuals in the meadow area of the property - every cricket I could approach closely enough to adequately record - just to be sure.

Imagine my amazement when I discovered that every singer  was a Black-horned Tree Cricket! Notice how that bright turquoise pin jumps out in surprise amidst all the purple! 

So why would this be? Should I go back next year and try to get access to other areas nearly? 

As you can see, I’m starting my 2019 promise list right now.  

Black-horned Tree Cricket at Wolf Run Preserve on the Vermilion River.

Who lives where?

In general, almost all my recording sites have had entirely Forbes’s or a mixture of both species. The sites with only Black-horned Tree Crickets are very uncommon. 

Forbes’s Tree Crickets are generally the expected species along the lakeshore. Yet inland at the Holden Arboretum in Lake County, all the look-alike crickets I’d previously recorded in the Prairie Garden and along Sperry Road have also been Forbes’s. 

I was a little dubious about the Holden results and decided to recheck the goldenrod-filled meadows along Sperry Road near the Working Woods. The tally? 19 Forbes’s and no Black-horned, even though Holden is considerably inland from Lake Erie. I feel confident about my earlier recordings now, and also about those 19 crickets I recorded on a warm, but very overcast late afternoon shortly before rain showers moved in.

There are also Forbes’s Tree Crickets at Orchard Hills Park in Geauga County near the Lake County border, and I recorded 13 more Forbes’s 12 miles due south at Frohring Meadows. Cleveland Metroparks’ Acacia Reservation, a former golf course in a dense retail area next to I-271, also has Forbes’s Tree Crickets. Clearly, this more western species has a strong six-legged foothold in locations east of the Cuyahoga River. 

Other areas have a mixture of both species, that can even be found singing next to each other in the same meadow. Although we humans have great difficulty hearing the difference, the female tree crickets have no problem distinguishing who’s who. 

Range maps have shown our entire area to be the exclusive home of Black-horned Tree Crickets, but that’s clearly not the case. Are there areas in our region where Black-horned Tree Crickets are the majority? Are they ever the only one of the two species present? Wolf Run Preserve was one case, but what about farther east?

The mysterious Portage County

Herrick Fen, upper left. Morgan Park, upper right. Breakneck Creek, lower right. 
Kent Bog, lower left. The turquoise pin the the middle is Towners Woods.

 Breakneck Creek Preserve, 8-26-18. Visual identification is not possible.

The most likely area in which to find Black-horneds seems to be Portage County. I found exclusively Black-horned along the Butterfly Trail at Towners Woods in both 2017 and 2018, and Breakneck Creek Preserve had 13 Black-horned and 7 Forbes’s in 2018. 
   This Breakneck Creek female was near a Forbes's male, as confirmed by my recording. 
   It seemed likely that she, too, was a Forbes's. However, I can't confirm this because the      females don't sing

I had assumed Kent Bog could be a reliable place to find Black-horned, as I recorded 5 Black-horned and 2 Forbes’s in 2017. My recordings and temperatures were accurate.

Yet when I went back in September 2018 with tree cricket citizen scientist extraordinaire Nancy Collins, I recorded 12 Forbes’s and NO Black-horneds in the goldenrod-filled field next to the bog in 2018. Zero. My recording and temperature methods were identical both years. What was different? 

On to another of Portage County’s bogs and fens. Herrick Fen’s tall, dense goldenrod approaching the boardwalk is generously adorned with singing with Black-Horned Tree Crickets. I recorded 14 of them in 2017, and those were just the crickets that were accessible to me (with difficulty, I might add).  Yet I found 4 Forbes’s Tree Crickets but no Black-horneds along the boardwalk in the fen itself. Why this difference? The vegetation in the fen area? Less density among the plants? But if Forbes’s is a more western species, why would I find them in a Portage County fen that is surrounded by Black-horned Tree Crickets? How long have they been there?

Although Portage County may be the best place in the Cleveland region to search for Black-horned Tree Crickets, there’s no guarantee that a plethora of Forbes’s might not turn up instead. Morgan Park had a wealth of singing tree crickets in the meadow when I visited on 8-20-18, and to my surprise, 21 were Forbes’s with only 2 Black-horned. 

The area in which I made all those recordings was primarily a goldenrod meadow. Would the results have been different if I’d recorded in the nearby wetland area that’s being restored?

It seems that each time I’ve thought I could begin to consider some conditional conclusions about what I was discovering, I found I was puzzled instead. I brought individual crickets home from this county so that I could verify the accuracy of my species identifications from these locations. My in-house recordings always matched the species identifications from the field. 

I reminded myself that I was making recordings and observations. I had neither enough information nor enough background to make conclusions about what I was finding, so maybe I was writing a mystery without any idea how it would end.

Well, Portage County, I’ll be making additional trips out your way in 2019…

Burton Wetlands, Geauga County

I also paid a visit to one of my oldest friends: Burton Wetlands. I did a two-year singing insect survey for the Geauga Park District as a Small Grant Program recipient in 2010-2011 and got to know this park better than any other since that time. But there was still something I needed to learn: Black-horned, Forbes's, or both?

Burton Wetlands in Geauga County has a glacial kettle lake, and a significant area of the park consists of goldenrod-filled former agricultural land. My intensive time there occurred  before Nancy Collins alerted me to the fact that both Black-horned and Forbes's were possible species in my area.

What I found especially interesting about my 2018 recordings is that there were 9 Black-horned Tree Crickets that were all around the edge of Lake Kelso. I even recorded a few of them from the floating dock and by hanging over the observation deck by the poison sumac. Here's one of them:

There were no Forbes's by the glacial lake, yet I recorded 17 Forbes's (and no Black-horned) in the goldenrod meadows.

Just across the Summit County line

The Pond Brook Conservation Area of Liberty Park is in Summit County and Novak Sanctuary is in Portage County. Only six miles apart, they feel like the same region.

Crickets and katydids don’t know or care which side of the county line they’re on, and there are areas of Summit County – and even parts Geauga County - that feel quite similar to those just across the Portage County border. 

Summit and Portage certainly appeared to be an overlap zone, but there were also areas of exclusively Forbes’s in both counties. Bath Nature Preserve on the western side of Summit County has both species, yet I’ve only recorded Forbes across that county line in Medina County. Well inside Summit County, however, I recorded 29 Forbes’s and no Black-horned at Tallmadge Meadows in the Akron area of Summit County. 

In 2016, I did a similar survey across the county line in the Greater Cleveland Audubon Society’s Novak Sanctuary in Portage County - just six miles from Pond Brook in Summit County.

I recorded only Black-horned Tree Crickets at Novak in 2016 but subsequently found 7 Forbes’s and 5 Black-horned when I recorded in a larger area in 2017.

    Female ovipositing at Novak Sanctuary in Aurora, Portage County. She could be either         species, as both are present.

I definitely wanted to refine my search at Liberty Park's Pond Brook Conservation Area in Twinsburg. It has an abundance of appropriate habitat to support these tree cricket species. I know this preserve well, too. I explored some of its habitats in detail and made a singing insects species list there in August and September of 2013 - again, before I knew about the Forbes's Tree Crickets.

August 28th was one of those wonderfully warm, calm, humid nights I love for singing insects research. I recorded 15 Black-horned Tree Crickets and 9 Forbes’s at Pond Brook. At one point on the Buttonbush Trail, all the crickets on the brook side of the path were one species and those on the opposite side of the path were the other. I literally had Black-horneds singing by my left shoulder and Forbes’s by my right! 

Here are two of the crickets I recorded: both species are in close proximity and were recorded at the same temperature. You’ll hear other crickets in the overall chorus – especially the ubiquitous Jumping Bush Crickets – and Pond Brook itself in the background. 

Why are two such similar species living together in the same parks and preserves? Do they only seem similar to the unrefined hearing and vision of humans? How long have they coexisted? Is one displacing the other? Are why do some parks only have Forbes’s?

I’ve probably made a case for spending an entire summer in Portage and Summit Counties. 

So, 2019…

I’m definitely getting a clearer idea of where each species is found and the areas where they overlap. 2018 also brought surprises, and it seemed that addtional observations resulted in new questions.

If I go a little farther east into Ashtabula County next year, would I still find Forbes's along the lakeshore but then discover more Black-horneds as I explore farther inland? Could I perhaps find a couple of folks to join me in Mahoning or Trumbull County for a night survey or two to see/hear what’s similar a little east of mysterious Portage County? Would I find more Black-horned Tree Crickets than Forbes’s? Just where are the edges of the overlap zone– and why?

I’d also like to look a little farther south if I can get after-dark access. I have only limited and inconclusive recordings for places like The Wilderness Center. Tree cricket researcher Dr. Laurel Symes collected Forbes’s and Black-horned data in Ohio and documented both species in Clinton (Summit County) and North Canton (Stark County). This is a little south of where I’ve been recording, and I find it encouraging that my data seems consistent with hers.

And I can’t forget that I’ve barely skimmed the Table of Contents for what Lorain County might reveal…

I know, I know. The list is getting several years long, and perhaps longer than the number of years I may have to explore the locations and questions that are so intriguing to me. I already have some very interesting and rewarding singing insect teaching coming up in 2019, and the beginning of fall semester on August 26th will necessitate prioritizing my searches further.

I’m definitely getting a clearer idea of where each species is found and the places they overlap. This year also brought some surprises, and I found that the more data I collected, the more questions I have. 

The 2018 singing insect season ended like those before it; field clothes covered with burrs, various sticktights, and the ubiquitous tick trefoil seeds. Blackberry thorns were embedded in my arms and hands. My hair, as usual, seemed to harbor a goldenrod seed bank. 

Is it obvious that I can hardly wait for next August?

For more information on these crickets and my study of them, please see my Listening to Insects field guide entry here