Saturday, April 24, 2010

Breezy Heights Xerolenta (oil on canvas 5 x 7 in.) Sold

23 April finds us on a seldom-used but well-paved stretch of Breezy Heights Road, by the big quarry south of Antrim Ontario.  A thriving population of the introduced snail Xerolenta leaves its empty shells littered so abundantly in the roadside ditch and on the dry lichened and mosssy ground between sprawling Juniper bushes, that the shells appear to be a part of the gravel substrate.

From a slow moving vehicle we can see constellations of shells on the grey crushed limestone of the road shoulders, and where the off-road habitat was similar among spreading Junipers. We walk slowly back and forth on both sides of the road, scanning the  littered shells for an hour and a quarter, finding each cluster somehow defective in composition, or with not enough fresh, shells which show the brown stripe.  I was amazed that Fred's patience matched my own in this endeavour, as the afternoon sun dropped toward the horizon and my painting time became seriously shortened.  We finally came upon this naturally pleasing arrangement of empty shells (where the live snails are is anyone's guess...) on the east side of the road and I settle down on a cushion to paint it as I see it, with no rearranging of shells at all.



We first learned of Xerolenta obvia (then Helicella obvia) when Wayne Grimm and Glen Wiggins published an account of a colony in Bethany, Ontario. In the 1990s we made some efforts to map the limits of this colony along roads and railways around Bethany.

This fall, we learned from the Canadian Food Inspection Agency (for whom we produced the book on introduced land snails and slugs in Canada) that the species had been found along Breezy Heights Road, near Antrim, and afternoon we headed out from Ottawa, so that I could see this spectacle, and we could map some of the limits of this colony.

Fred has set himself the task of seeing how extensive the colony is in the quarry, and as soon as I am settled to paint, he was over the roadside berm and into the quarry, first crossing a gravel flat where the Xerolenta shells were present in greater abundance than anywhere on the roadside, and then down steps of bedrock to the lowest level of the quarry and out onto tongues of "over burden" (soil and stumps) that had been bulldozed into the surrounding Cedar forests. Here there were few or no Xerolenta, and he found that the shells thinned out or disappeared when ever he got off the open quarry and into forest or solidly vegetated sod. So the snails inhabit the entire 600m quarry, back to its SW border at the forest -- especially where the vegetation is scattered Knapweed plants. In November Fred and Robert had found shells along 1.4 km of Breezy Heights Road, so the SW margin remains to be determined in the trailer park to the northwest, and the residences to the southeast of the quarry.

It's along roads that the open habitat the Xerolenta use is artificially created, and there's no telling how they'll stread along the eastern Ontario Road network.

2 comments:

  1. Aletas' painting site was at 45.341764N 76.19523W in case anyone wants to go and see for themselves the spectacle of these millions (ca 300/sq m in the best habitat, so there's 1 million in a 58 m square) of snail shells (or in the summer, the living snails clustered on the Knapweed that seems to be their preferred vegetation here). This may be a foretaste of what many of our roadsides will look like in a couple of decades, as the snails get wafted hither and yon by the assistance of vehicles.

    On our way out to the site, we'd stopped at a few places along the west-bound Hwy 417 adjacent to the quarry, and not-found Xerolenta in two of them and found it at another of these sites north of the road. In November Robert Forsyth and I had found it along the south side (E-bound) of the 417 adjacent to the quarry, and as we drove back into Ottawa in the evening, Aleta and I were appalled at the myriads of kilometres that need to be searched to find an invasive species that's accidentally dispersed.

    The 417 needs to be searched especially between 45.356376N 76.222293W (Kinburn Sideroad) and 45.356376N 76.222293W (Panmure Rd), so if anyone feels the need to stop and stretch along that part of the highway, or anywhere else, along any road with shallow-soil limey Juniper barrens on the roadside, locations where Xerolenta are or aren't found would contribute to a publication on its status in Ontario that Eric Snyder is putting together.

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  2. At the time this was written we hadn't read down into an e-mail thread we'd had forwarded from the CFIA to realize that it was Ross Layberry who had discovered the colony in September, 2009, and that he had mapped the extent of the snails along the "seldom-used but well-paved" Breezy Heights Road, which he'd known was the former Hwy 17, and also along the old Hwy 17, on the other side of the current highway, both as the road of that name, and as the abandoned track paralleling the new highway for a ways on the SE side.

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