Little seems to be published or recorded on Helix pomatia in the UK and the intention of this ‘work’ is to provide accessible information, and also to investigate behaviours others before have commented upon.
General information can be found on http://en.wikipedia.org/wiki/Helix_pomatia
I’ve always been fascinated by snails. Even aged three I’d rather rather race snails on the doorstep than play with my cousins.
I acquired 2 adult Helix pomatia in 1971 from a bank-hedge in the Cotswolds before their protection under the 1981 Wildlife and Countryside Act.
A diversion to Chedworth Roman villa on the way to my cousin’s wedding in Shropshire was the only way my parents could entice me to attend. The two snails mated successfully and I kept them in sandwich boxes for two years until I had my own property in Somerset where I released them into the garden.
I collected another 4 a few years later, and the population within the garden steadily increased to an estimated 40 individuals without assistance. The garden was a wild-type cottage garden with lots of local stone, rubble and rockeries. Although not in the part of the UK where this species of snail can be found naturally they seemed to thrive reasonably well in small numbers. Nothing prevented them from wandering beyond the garden, although there were wall boundaries on two sides.
The garden was extended and made more formal with bigger lawns and no vegetable patch in 2002, (Gallery 4) and the numbers steadily declined. If I came across a juvenile it was collected and reared in a propagator until adulthood to increase its survival chances, then released.
In early 2006, as the house was put on the market for sale, I decided to collect whatever snails were still in the garden and take them with me to wherever I went. I suspected there were only 5 individuals left, but during the next couple of months I found 10 adults and one large juvenile and placed them in large propagators and fed them well.
These 11 snails became the basis of this study.
Although they may not have liked being enclosed initially, the fact there was no shortage of their favourite foods each day, (Iceberg lettuce, fresh dandelion leaves, dried stinging nettles and cardboard toilet roll spools) meant they soon put on condition. Also a potential mate was always available.
During the summer I provided them with transparent egg-laying pots and between them they laid 608 eggs from 12 clutches, some individuals laying twice. (Table 1) Each clutch was counted and I observed the numbers of eggs were much more than clutches I’d come across in the garden in previous years. I also recorded the mortality rate among the juveniles - about 70 died. I saw baby snails between and within clutches grew at varying rates.
The 11 adults successfully hibernated as did over 500 young. Most of these were released in the following spring and summer in an existing recognised site under the instruction and direction of English Nature. Thirty three snails were kept.
I realised from these unscientific observations I had a lot of potential research work ahead, as well as young snails to rear, so planned a more structured programme for 2007 as it seemed unlikely I’d move after all.
My first challenge was to find a system of permanently marking the adults so I could monitor the behaviour of each individual..
In my previous research in Cepaea hortensis and Cepaea nemoralis in the 1980’s identification could be achieved by drilling small holes into the lip of the shell – each hole representing a number from 1 – 5.
The shells of Helix pomatia are too thick to do this with a hand drill, and my numbers too small to take risks with anything more powerful. Therefore I tried various shell-marking systems with different pens, inks and paints. Nothing worked particularly well as the adults bury themselves frequently which erodes the outer layers of shell. (Old snails can be recognised for being nearly white, while newly grown adults are golden).
To improve identification I also measured each individual with callipers. (Gallery)
Tippex correcting fluid turned out to be the most durable product I could find and with it random letters of the alphabet were painted on the shells. (Gallery).
I kept the snails in propagators for the entire year and all information can be seen in (Tables 2 and 3).
In the autumn and following spring once the hatchlings were large enough to handle they were released. Five fast growing specimens were retained from each clutch (Table 4)
Having only 11 adult snails meant that in spite of shell erosion identification was possible and so in 2008 I released them back into the garden. This was done after their hibernation in boxes in a cool shed, and a three week period of fattening on favoured foods after they woke. They also ate the cardboard spools of toilet rolls (Gallery) which had been provided for them to hide in, and newspaper.
Rather than carrying them to sheltered parts of the garden and distributing them randomly, I placed their boxes in a shaded area and just took the lids off. (Gallery) From there the snails could roam free although I kept a constant food supply in the propagator area as they seemed reluctant to move. There was ten feet of gravel to cross which I thought might be off-putting but they seemed not to mind it, also happily buried themselves within it.
Simple observations revealed each snail behaved differently. Some were sighted in the garden many times and some were scarcely seen (Tables 5 & 5A). They roamed the entire garden which meant by October collection time three were not found. Two very old ones died during the year. There was also strong evidence of homing instinct – most returned to the propagator area from time to time which meant crossing the gravel.
One snail was seen 67 times during the year, and another 54 times, and coincidence or not these were the two largest individuals, and in contrast the smallest one was recorded but once and the next smallest only 11 times. On average snails were observed about 30 times. I didn’t record visible snails unless there was evidence of movement from the previous sightings.
I observed courtship and egg laying as well (which was unseasonably late) and found 50 very small juveniles to rear in boxes to increase their chance of survival.
In October I collected whatever adults I could find (six) to hibernate them in propagators again. About 300 juveniles hatched in 2007 were released during the year.
Old marked snails were released in April, now only numbering 6 individuals. Also released were 27 uniquely marked home grown and now mature individuals from the 2006 clutches. Three snails had been retained from each clutch to improve the gene pool.
All snails were released in a central flower bed surrounded by lawn (see Table 8) and all behaviour was recorded until 15th July. (Table 6)
Three growing juveniles from the nineteen 2007 clutches were reared but not released. They will be cross mated in 2010. Surviving 2008 hatchlings were also reared.