RESEARCH

at the Bishops Mills
Natural History Centre


[Frederick W. Schueler in the field]




Autumnal feeding behavior
of Cepaea nemoralis snails



photos and journal by Aleta Karstad

On the evening of 14 October 2005 at 22:50 I released a small jar full of Cepaea snails that Fred had picked up and measured from their wanderings on the pavement of the "Our Streets" transect. He had mentioned that tonight many of them were up in the vegetation along and overhanging the pavement, and when I glanced into the dead Queen Anne's Lace stems by the fence in the light of the streetlamp, I noticed a constellation of snails up in the dry Queen Anne's Lace (Carrot - Daucus carota) like early Christmas ornaments. There was at least one per plant, and up to three on some. I didn't notice whether the snails were active or resting at the time.

On the next morning at 9:30 (temperature 13C, overcast after intermittent rain) there were many fewer snails on the stems. I went out with Timothy Thomas to photograph them at 14:30 (19C and sunny) and saw about 7 large adults and at least a dozen of this year's juveniles (3 - 5 mm diameter). Most of the adults were resting on the stems, but not sealed up with dried mucus as they do when they are dormant. Most of the little ones were at the tops. The brown skins of many of the dry Carrot stalks were peeled off in patches, revealing the fibrous structural core of the stems gleaming in bright ivory, and suggesting that the snails had been climbing the stems to feed on the dried skins of the Carrot stalks.

Tonight at 22:30 (10C and breezy) we went out with the spotlight and camera to see if the snails were climbing again by night, but the stems were bare, dry, and devoid of snails. Three small individuals were seen on the only patch of damp pavement edge near the intersection, and none on the dry road. On a previous wet night, Fred had noticed that they were up on the vegetation for the first time this year, but his attention was so focused on the road that he did not look over into the Queen Anne's Lace.

It is wonderful to have seen the snails doing things en masse, according to season and weather, and I feel fortunate to have witnessed brief and surprising periods of "group activity" in the usually secretive lives of these large, jewel-like invertebrates. One of the lessons we are learning in our programme of nocturnal street surveys is that there are lots of seasonally timed activities that you miss if you don't make daily (or nightly) observations.






[Queen Anne's Lace stems]
[adult Cepaea on Queen Anne's Lace stem]
[Adult Cepaea on Queen Anne's Lace]
[young Cepaea on Queen Anne's Lace flower]


30 Main St., Bishops Mills
RR#2
Oxford Station, Ont. K0G 1T0
Canada

(613)258-3107

Aleta Karstadkarstad@pinicola.ca