RAUK - Archived Forum - Natrix tessellata hybrid?

In the alien species/Natrix tessellata topic area I posted a message regarding the strange phenotypic mix of the Natrix tribe to be found at Newdigate in Surrey, and stated that there appeared to be Natrix tessellata hybrids present at the site.

Having questioned this bold statement (because I consider the possibility of hybridisation between N. tessellata and othermembers of the genus somewhat unlikely) I again reviewed my pictures of specimens photographed at the Newdigate site, and I am still no closer to a conclusion!

I have not photographed specimens of the typical British species Natrix natrix helvetica at the site, almost certainly because of the prevalence of hybridisation with European types:

Typical N.n.helvetica Berkshire specimen

Many individuals are boldly marked and have dorsal stripes typical of Natrix natrix persa:

Some specimens appear to be hybrids of Natrix tessellata. It could be argued that they are typical of the olive grey form of Spanish Natrix natrix astreptophora but the positioning of the nostril, and the fact that there appear to be two preocular scales as opposed to the one of Natrix natrix sp. seems to preclude this. And yet...there are only seven upper labials...hence my assuption of a natrix/tessellata hybrid:

Having reviewed the case again, my own feeling is that it is not, and cannot be a hybrid, and that the apparent separation of the preocular scales may not be as complete as it looks.

Any thoughts will be very welcome!!!

Many thanks

Peter Sutton 

Here are a couple of close-ups of the pre-ocular scales of the olive grey Natrix sp.:

There appear to be two pre-ocular scales suggesting Natrix tessellata, this specimen had no yellow collar scales and a comparatively large triangular head.

Peter Sutton

Hi Peter,

Sorry I can't really help with your Snakes and I don't want to detract from the subject as I'm extremely interested myself. I've heard about Newdigate as a site for exotics several times in the past. Could you give us a potted history with details on which species (reps and amphibs) were released and which, if any, survive today. I assume it was just reptiles and amphibians, although if it was research laboratory, as I've heard, were any mammals let loose? Thanks in advance

Dave

Hi Dave,

I have been visiting the Newdigate site virtually every year for over 20 years and I am currently writing a historical account of the reptiles and amphibians that have been recorded there.

In brief, the site (which was formerly partially accessible through the owner of the now closed aquatic nursery, but is now fenced off with a high tech. security system and requires specific permission from the owner of the (Bill Kear) Plant Hire company which occupies part of the site) is well known for its extant populations of Alpine Newt and Italian Crested Newts, Edible and Pool Frogs.

Formerley there were populations of species which have been documented in literature such as the Fire Salamander (per Wycherley and Anstis (Surrey herp atlas), and those that have not including Wall Lizards (sp. unknown), a colony of European Tree Frogs, Marbled Newts, and a couple of other species (all based on accounts from the owner of the aquatic nursery) which have not been documented.

The Natrix sp. present indicate, as above, a high degree of hybridisation with N.n.helvetica.

All three British newts are present, and hybridisation between T. cristatus and T. carnifex is perceived to be a significant problem, although the resulting hybrids are reported to have much reduced fecundity which limits their ability to establish a wider distribution.

There are still Red-eared Terrapins in the adjacent Brook, and I believe there were once E. orbicularis but have not been able to substantiate this. 

For me the Newdigate site has always been a special place, from the first time I turned up as a boy on an old rusty bicycle after reading about the presence of Alpine Newts in Christopher Lever's 'Naturalised Animals of the British Isles'. At present the ponds are still there but the owner of the site has little or no interest in maintaining them and they are beginning to get shaded with scrubby growth and trees. If I had the money I would buy the site for posterity! I will never tire of studying water life in those remarkable ponds, or watching water frogs sitting among the colourful blooms of old Victorian strains of water lily that still grow at the site to this day.

Kind regards

Peter Sutton

Peter,

I read your post with interest, but I wondered why you think that the hybridisation would be so out of the question?

I shouldn't place too much emphasis on the facial scales as I have seen helvetica with two preoculars. here posted are two pics, one showing a three post ocular example with nasal opening on an independent scale and another with two post oculars and nasal vent /opening adjoining two scales. there are a lot of variants out there, and I would say that some measure of hybridisation has gone on at some stage.

Cheers. Robert

And heres one with two preocular scales, with one larger scale in front of those (as opposed to two inter connecting) and three post ocular scales and I would say that it is a Helvetica?

Cheers

Robert

Hi Steve,

Gone I'm afraid. I have the exact location for where the Wall Lizards used to occur, but the colony was small and localized and has not been seen for many years. I have been visiting the site since the mid-eighties and I have never seen a Wall Lizard there. This is among a number of species whose existence at the site has been definite but transitory.

All best

Peter

Hi

A Wall Lizard colony has been present at the old Xenepus site in Nutfield, Surrey for decades.... and was still there a couple of years ago.

Julia