Marjan van Hulsel is back from Peru and spent two days in Leiden to discuss her observations.
Without any analyses of the material, it is clear that the following preliminary conclusions can be reached:
– In Laraos region, the ‘cork-skrew’ shells were only observed on a South-facing slope exposed to the winds blowing up the Río Cañete valley.
– Two Bostryx species exhibiting these morphs we found allopatrically on this slope; B. imeldae was only present on the upper part, B. zilchi on the lower part of the slope.
– in Tembladera region, carinated and ‘normal’ Scutalus species were found sympatrically, which relatively few hybrid specimens mixed.
– in the area where both species were most abundant, S. baroni was relatively more frequent on the upper part of the slope, and S. cretaceus relatively more frequent on the lower part.
Further analyses of the many data collected may start to give some clues on this phenomenon, but undoubtedly will also present more questions.
Some other observations:
Some shells showed probably signs by predation. However, no actual predation was observed and it remains unknown what animal may have caused this. BTW: note the thick mucus remnants on spots where snails possibly have been inactive for prolonged periods.
Scutalus species not only occur here on the rocks, but also on trees and cacti. This movie shows that they can reach heights which are usually associated with arboreal snails. The highest altitude above the ground where Marjan observed a Scutalus cretaceus was 5 m!
Finally, some pictures of snails; the longer you look, the more you see…