Report from a drainage swale

Report from a drainage swale. July 2014

Greg Gerritt Watershed Steward Friends of the Moshassuck


I am spending more and more time by a little drainage swale in the North Burial Ground. So much that my wife gave me a chocolate toad Valentine treat this year. And it will be in a video. Just below the maintenance building and sitting within a stones throw of I-95 this particular swale usually has water, but has been known to go dry at any season of the year if we go three or 4 weeks without rain. When I began spending time at the drainage swale I was focused on the life in the pond. I will return to that shortly, but this year an additional interest has been it’s functioning as a rainwater runoff catchment basin.
It turns out that our community is now ready, 17 years after we started talking about it, for a new way to manage rainwater. Doing it in ways that clean and recycle the water within the ecosystem is becoming the norm. Of special concern is what we do when the rainwater comes in the torrents that climate change is already bringing to us. The word is getting out about rainwater gardens, filtering systems to clean and infiltrate rainwater and never let it into the sewage system, such as the new installations at J. T. Owens Park and Providence College. What is so interesting about the NBG swale is that instead of filtering and draining it holds the water, and therefore has turned into some very interesting wildlife habitat. As Rhode Island looks to ever more Green Infrastructure I am going to push for at least some rainwater management efforts that increase wildlife habitat, especially for amphibians, among the most endangered taxa on Earth.


I visit the Burial Ground and the drainage swale in all seasons, and it is almost always an interesting place. But from May to July it is at its best. From the time the Toads and Tree Frogs start calling in the spring, May 10th in 2014, the first evening over 60 degrees, the place really perks up. The vegetation explodes with cattails shooting up and the pickerelweed starts covering more and more of the pond. Pickerelweed seems to retreat in the winter and then grow from runners spreading to cover the whole pond by late June. Then come their purple flowers that attract all kinds of insects and the aerial show of dragonflies and bees comes to town.


It was the Fowler’s Toad tadpoles that first caught my eye 5 years ago, I was walking along the shore looking for life and there they were. They have become a lodestone that draws me back for hours at a time in the late spring. Fowler’s Toads, Bufo fowleri is a grey mottled toad 2 or 3 inches long native to eastern North America, pretty similar to the American toad. I have only seen the adult toads 3 or 4 times, including once this spring sitting on the bottom of the pond, but I am quite familiar with very young toads and the tadpoles that precede them.


About 7 days after the first night of mating 1/8-inch long tadpoles appear. And with the same time lag new pulses of tadpoles followed each night of successful mating until there were at least 6 different age classes in the pond this spring, and even after the first newly transformed toads hopped away up the hill in late June there continued to be young tadpoles swimming about into mid July and new pulses of tiny toads.  Fowler’s Toad tadpoles are little black things that swim hither and yon in the pond, moving almost randomly, stopping frequently to eat. They land on vegetation and start scraping algae and bacteria off. I found out that the tail of a tadpole, in addition to being used for swimming, is mostly intestine for digesting the large quantities of low energy food that they feed on.


I tend to think of the tadpoles as colonial but not social. Often they clump together in large schools, grazing and resting, but they seem almost oblivious to each other, as the only interactions among them are when they accidentally bump into each other. In fact other than swimming and eating the most characteristic movement of a Fowler’s Toad tadpole is shaking vigorously, which appears to be their all purpose response to any irritation, whether it be human, insect, microscopic irritant, or another tadpole.


Over the course of 4 or 5 weeks the tadpoles grow to about 1 inch long, develop legs, shrink to ½ the size of the largest tadpoles as all the stored nutrients are transformed into legs, and hop away from the pond to feed on insects (hence no longer needing a massive intestine), and return the next spring for some very wild nighttime choruses. As this is a video project I have some video of the lights from cars and Benny’s on Branch Avenue as well as the moon, as the sights to accompany the walls of sound that that the toads and tree frogs make on warm spring nights.


Three years ago it became obvious to me that this was a great site for a video project, as you can stand on the edge of the pond and easily get very interesting and informative views and footage of tadpoles in their element in the early part of the season. I then sought out youth programs to see if there were any kids that could be attracted to the project. When no programs were able to get involved (a project that starts in the spring and continues into summer vacation is problematic and the Burial Ground is not really near any schools or child centers for convenient walking) I decided to do the videos myself and found support for equipment from the RI Rivers Council, whose support is greatly appreciated.


I have now being doing videos of the drainage swale and other life in the North Burial Ground for 18 months, beginning in January 2013. I have winter pictures including a frozen pond and snow, pictures of a chocolate Valentine’s toad in the snow proclaiming it is all about Toad Love, pictures of dry cracked mud in the summer, footage of vegetation, insects, Gray Tree Frogs, and fall leaves, but mostly video of Fowler’s Toad tadpoles. At the other pond in the Burial Ground I focus on birds turtles, and bullfrogs. I focus on the Toads primarily because they are easy to see in the pond and capture for close-ups, partly because the transformation from tadpole to toad fascinates me, and to be able to watch, record, and share it in detail is a treat.


Most of the in pond shots of tadpoles (and other pond creatures) are magnified, sometimes to 100 times, depending upon the brightness of the sun that day and the other conditions. And for many of the things I am capturing with the camera the best technique is to focus the camera on something interesting and then walk away and let the animals do their thing. In addition to capturing moments that I do not have the patience to observe in real time, the magnification allows everyone to see things that are so small that you cannot see them with the naked eye or even in the camera’s view screen. I see things when watching the dailies that I had no idea were there when I was filming.


This has given me insight into both what else lives in the pond (just wait until you see the dancing midge larva) and the behavior of the tadpoles. Without the camera I would never have been able to observe in detail how tadpoles eat, and I know that I never would have come to the conclusion that they are colonial but totally socially oblivious. Recently I have gotten into the habit of shooting some high magnification video of mudflats just to keep track of the tiny ones, though as the vegetation grows, the places one could do that are rapidly disappearing, and as of late June it is almost impossible to see into the pond, especially when the water is relatively low. At high water the swale extends to cover some of the mowed grass that normally surrounds it, and the visibility of the tadpoles in those sections is very good.


Last year was the first year of the video project, and for me the first time I had ever used a video camera. When I started I had no idea how to connect the camera to the computer and use the program to edit the movies. I am still learning how to edit and just recently I learned to do sound editing, music and voice-overs, something I am just beginning to put into Moshassuckcritters videos.


My goal all along has been to film all of the stages of development from mating to tadpoles to toads to returning to breed. Some stages are harder to capture than others, especially once they leave the pond, but I am developing a much larger library due to a focus on captive shots throughout the tadpole development cycle this year and a couple of days in mid June where the light and scene were excellent for capturing leg development in free swimming tadpoles and nearly every size tadpole imaginable were present in the pond and showed up in my net. To record leg development I net tadpoles, transfer into small pond water filled containers that are the right size to zoom in on so the tadpole is not constantly going out of the picture. My goal is 5 seconds of tadpole calmness for each videoed tadpole so leg size can be recorded. I expect as I go over 8 weeks of near daily video clips I shall be able to make a pretty good progression video for the development of Fowler’s toads in this particular place. Last year’s progression video was okay.  It was even entertaining considering I had almost no control over the audio except to use what was on the film or mute it and all the captions are paper signs I shot video of and edited in and only late in the season did I start capturing tadpoles for close-ups. We should know in a month or two whether I can put together a better quality and easier watching video that provide useful information for those who want to know more about tadpoles in the city and hold eyeballs. I have several stories to convey, feeding behavior, swimming, and developmental changes over the course of the spring, and will do several of the projects in varying length videos including some very short ones.


Another of my goals with this project has been to use it to promote knowledge of biodiversity in the city with the hope of attracting some of the next generation of environmental activists from urban neighborhoods to ground themselves in biology and the natural world so they are more prepared for the struggle. I have not really been successful in this endeavor beyond sharing my videos on YouTube. Hopefully as more and more work goes into urban biodiversity, and the quality of the videos improves, more folks will take advantage of the resource I am providing.


Video from the project is primarily available at with links at the Friends so the Moshassuck website and at the blog   where most of the various writing I do is posted and Moshassuckcritters videos appear.


Enough about the project, you can watch the videos. If anyone wants to join the project, happy to discuss it further. So here is what I now know about Fowler’s Toads and their development through the course of the spring.


Fowler Toad adults head to the water for breeding beginning in May. It appears that breeding season starts when temperatures after dark are above 60 degrees Fahrenheit. (16 degrees Celsius). The toads start calling after sunset, but do not reach full chorus until it is dark. This is what they sound like:


They mate on many different evenings, probably as often as conditions are right, but the population of adults at this particular pond is not very large. I could not make an exact count, maybe next year that is another thing to add to the list of things to record, but I figure there were at most about 10 or 20 Toads scattered about the shore. Even so, the chorus is hypnotic. The evenings of frolic produce thousands of tadpoles, with the numbers varying quite a bit from year to year. This year the numbers seem down a bit from the last two years, though the length of the breeding season may have produced more tadpoles than I realize. All I know is that I have video of thousands of tadpoles in the water at one time as I panned the pond in late May, and that I can only video a small portion of the pond.


Fowler’s toads have some flexibility. This year mating commenced on May 10 and continued well into June. Last year the pond was dry until May 25, at which point mating commenced, again with mating on a series of evenings. I do not know where the toads deposit their eggs.


Gray Tree Frogs share the drainage swale with the Toads. They commence mating season within days of the Toads, and after May 15 Tree Frog mating calls predominate my recordings. Tree frog tadpoles appear much later than Fowler’s toad tadpoles, and are much harder to observe. There are probably a variety of reasons for this, but the current hypothesis is that they stay deeper in the water than the Fowler’s Toads and only come near enough to shore to be seen or caught when the swale is at high water. Last year’s conditions seemed better for observing the Tree frogs and a 2013 video of them is available at



Toad tadpoles appear within 7 days of mating, This year I recorded them on May 17 and the first night of mating was May 10. I think that as the water warms up the eggs turn to tadpoles a bit faster, and I would not be surprised if late season tadpoles develop faster than early season tadpoles due to the warmer water keeping the metabolic fires running hotter and the greater availability of food.


The rear legs develop first and take a fair bit of time to grow to full size. Given all the different sizes I have recorded, and the length of the breeding season, I am guessing that legs begin to appear when they are two to three weeks old, but I have not done a detailed enough analysis of the progression I have recorded to make the case for sure. I may try to come up with a better methodology for this analysis next year even as I do more detailed analysis of this year’s film to see what I can learn.


Front legs start to appear after rear leg development is essentially complete. As the rear legs grow they are used in locomotion on the floor of the pond, but swimming continues to be dominated by tail-powered locomotion. I have not been able to garner a very good series of front leg growth pictures. I think a detailed look at all of my 4 legged tadpole pictures will give me a better sense of this, but my impression is that once the front legs start to appear they very quickly develop and grow out. At the 4 legged with tail stage the legs come to complement the tail in locomotion, especially on the pond bottom.


With 4 legs complete the tail shrinks rapidly and the toad becomes an air breather. They continue to be able to swim, remember the toad found on the bottom of the pond, and the large one I keep hearing jump but never catch a glimpse of, but now adopt the typical anuran hopping locomotion, which allows them to spend much more time on dry land chasing insects. They appear to hang around the pond for a day or so, getting their land legs. Then waves and waves of less than ½ inch toads start hopping up the hill and away from the pond.


As noted I have only seen adult toads away from the pond 3 or 4 times over the years, so I have no direct knowledge of their behavior, but Wikipedia says they burrow into the ground for the winter, and the Burial Ground has that easy digging sandy soil that makes for good toad habitat and easier digging for burials in the times people dug them with shovels.


Biologists in Rhode Island have informed me that Fowler’s Toads are rarely encountered in here. Gray Tree Frogs are more common. I was also told that neither Fowler’s Toads nor Gray Tree Frogs have been recorded in Providence for 100 years until my video record. This could be because neither are found elsewhere in the city (possible) or because the few folks who know where are not spreading that information. In any case I do not know of any other similar habitat in Providence.


I hope to continue this essay when I know more, but until then, thanks for reading and check out Moshassuckcritters on YouTube.


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