Caught on camera

Finding the wild in the city (This first appeared in The Other Paper)

A bobcat eyes our camera near Patchen Road in South Burlington


What lives in those woods? This question has started many a scientific career. In the case of trees, a simple stroll may provide the answer. But sometimes we need other tools such as microscopes. Mammals are notoriously difficult to watch which explains the abundance of birders while mammal watchers are thin on the ground.

One inexpensive tool exponentially increases your chances of answering the question “what mammal lives here?” Infinitely patient “trail cameras” or “camera traps” allow even the worst mammal tracker to detect, photograph and appreciate the truly amazing mammals that frequent our woods, fields and back yards.

Starting in November, the South Burlington participants in the Vermont Master Naturalist program teamed up with four Saint Michael’s College students to install 25 cameras in South Burlington. We focused 16 cameras on the Underwood Property on Nowland Farm Drive and the adjacent woods to the south. A second set was pointed at I-89 underpasses and culverts near the Whale Tails and Centennial Woods.

Predictably, we photographed more than a few squirrels, deer and raccoons, but I found the spectacular predators we photographed far more fascinating. We learned from our cameras that we share South Burlington with no fewer than six native predatory mammal species, and a couple of domestic species.

It will surprise few that our photographs included coyotes and one in particular was quite startled by our camera beating a hasty retreat into the woods. Red foxes were rarer and seemed less camera shy. The first of a pair of grey foxes emerging from a culvert paused for a few frames to eye our camera before going about his or her business. The likely mate of the first popped out a minute later without a second glance.

One of our Centennial Woods cameras detected a mink on its first day, but this species was rare by comparison to foxes and coyotes. Fishers, or “fisher cats” as many call them, cousins of the mink, were slightly more common.

Fishers of course are not cats at all, but we did photograph some actual cats. Bobcats showed up in all three locations making them the most widely detected of the native carnivores during our brief study. We photographed a few domestic dogs and a domestic cat made frequent rounds of our Underwood cameras.

As an ecologist, I was quite pleased to see such a healthy community of small predators wedged among our dwellings, highways and human communities. These predators, together with the more omnivorous raccoons and opossums we photographed, help control rodent populations that might otherwise infest our town.

We did, indeed, detect some of these rodents. In addition to squirrels, mice showed up occasionally, but not in high numbers. This is in no small part due to the diverse predators keeping them in check and reducing our chances of contracting Lyme disease. Thankfully, at least from my point of view, we did not detect a single rat. I was curious if this was some fluke of camera placement, so I went to iNaturalist, a free database of natural history observations gathered by citizen scientists and our numbers mirror trends in Vermont.

I hope that our photographs are of interest and can contribute to a growing appreciation of the carnivores that help keep our yards pest free. And, if you decide that a trail camera is another way for you to enjoy the outdoors, for science fair, or just to ask, “who lives in my yard?”, please consider contributing your photographs to iNaturalist where your fellow scientists will appreciate the data and help with identifications.

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Declan McCabe is a South Burlington resident, naturalist and professor of biology at Saint Michael’s College.

If it looks like a snail....it might be a caddisfly

If it looks like a snail....it might be a caddisfly

After a year long hiatus to work on other things, I'm back to the blogosphere.  For my first foray of 2020, I present to you an article I wrote for The Outside Story in September 2019.

While sampling in the LaPlatte River, students noticed what looked like rough black pebbles about the size and shape of well-worn pencil erasers. I suppressed my mild distress as they started to discard the ‘pebbles;’ when sampling aquatic insects, I discard little.

Note black grains of magnetite. Photo by Erin Hayes Pontius 

I gathered the students around and balanced one of the pebbles on my finger and simply said “watch.” Shortly thereafter, the pebble was making its way off my fingertip seeking wetter and cooler places.

We placed several of the animals in dishes and distributed them along with hand lenses. Discoveries and observations were made on all sides. “When you see it up close, it’s obviously a snail.” “Hang on, it seems to have legs.” “It just blew a bubble out the back end.” “Hey, they pull back into the shell if you poke them.” “Somehow they stick to my forceps.”

Unplanned observations testing no particular hypothesis are essential components of field biology. The animals were snail-cased caddisflies, Helicopsyche borealis. When empty cases were first observed, a biologist described them as snails with the unique ability to incorporate sand grains into their shells.

The truth is more interesting. Caddisflies in the genus Helicopsyche bind sand grains together to make protective cases. Case making is common in caddisflies, but snail-shaped cases are unique to just one genus, at least in North America. That snails and caddisflies have evolved to produce very similar protective structures is a remarkable example of convergent evolution.

In common with snail species, Helicopsyche shells, or cases, generally coil in one direction. When Robert Hinchliffe and Richard Palmer from the University of Alberta examined 150 Helicopsyche cases from the Royal Ontario Museum collection, they found that all coiled to the right. When I look at preserved specimens in my collection, I have yet to see any coiled to the left, but now I’m inspired to look more carefully.

As my students looked carefully at their specimens, they made observations I can’t make from pickled samples; for example, the bubble that escaped from one case. Like many caddisflies, Helicopsyche larvae wriggle to create small water currents through their cases. This brings in oxygenated water and flushes away caddisfly waste. The waste produced by a single Helicopsyche must be scant indeed; but in aggregate I’m sure that their output, together with that of other species grazing on the rocks of the LaPlatte River, provides organic matter for an array of other tiny organisms that eke out their existence by gathering or filtering particles from the water.

Helicopsyche larvae eat periphyton – a blanket term that refers to the algae, diatoms, bacteria, and fungi that grow on clean rock surfaces. In some situations, the snail-shaped Helicopsyche case serves as a mobile garden. Jennifer Cavanaugh and colleagues from the University of Wisconsin discovered that larvae from one caddisfly species grazed periphyton right off the cases of their peers. It would be interesting to see if Helicopsyche cases provide similar movable feasts in the LaPlatte River.

Why the caddisfly cases stuck to students’ metal forceps proved to be the most challenging question of the afternoon. My first thought was that the caddisflies were grabbing on with their six limbs, as river insects do. My students rapidly disabused me of this simplistic notion. I was schooled when one student showed me that even when the insects were completely withdrawn into their protective armor, the cases seemed magnetically attracted to the forceps.

Magnetism proved to be the answer. After preserving some Helicopsyche cases in alcohol, and bleaching off the periphyton, the mystery was solved. The now empty cases still clung to metal. On examination under the microscope, small black grains were present among the brown and white sand grains. And when I carefully disassembled the cases, and dissected out the black grains, only the black grains were attracted to the forceps. The caddisflies had incorporated some magnetite into their cases.

We counted our caddisflies and other insects before returning them to the stream. Data sheets were filled, metrics of biodiversity calculated, and hypotheses tested; this was the planned point of the trip. But a great many more interesting lessons were learned simply by watching an insect as small as a shirt collar button. I like that it was many people looking closely and that each person noticed something different – the best part of an overall lovely afternoon, I thought.

This article was written for Northern Woodlands Magazine's Outside Story and first published on September 30th 2019  Visit the archive! The image, taken at Saint Michael's College, has been shared on Wikimedia Commons.

Declan McCabe teaches biology at Saint Michael’s College. His work with student researchers on insect communities in the Champlain Basin is funded by Vermont EPSCoR’s Grant NSF EPS Award #1556770 from the National Science Foundation.