Late season reptiling

With temperatures starting to drop and days becoming shorter early October is about the latest realistic time of year to catch up with some of the reptile species we more commonly associate with the summer. Harwood Dale, near Scarborough is perhaps under rated in terms of its natural history, in comparison to the expanses of heather moorland and woodlands of the North York Moors. The dale extends from Burniston up to Fylingdale Moor and includes a range of habitats from lowland pasture to upland heath. After heaving some luck with adders in the spring I decided to check an area of, productive regenerating, clear fell, conifer plantation at the northern edge of the dale.

Common Lizard

Autumn is without doubt a productive season to search for common lizards in North Yorkshire, with September being particularly productive. Lizards can be found basking at any time of day as they prepare for hibernation, typically when temperatures exceed 9^oC and there is enough direct sunlight to warrant efficient thermoregulation. Basking at this time of year is often extended due to the lower mean temperatures and features with a south facing aspect are sought, especially ones with a good heat conductivity like stones and logs. Dry stone walls are a particular favourite as they offer good thermoregulation habitat close to cover, especially where vegetation grows up them and is not to heavily grazed. Common lizards do not excavate their own refugia and are dependent on what is already present at a site, meaning favourable areas like dry stone walls can result in high densities in an enclosed area.

Male common lizard basking on a dry stone wall, Harwood Dale.

When lizards enter hibernation they need to have built up substantial fat and glycogen reserves, which helps them survive the winter. Common lizards are not specifically communal during hibernation, although good numbers may gather at a particularly good spot. Hibernacula are usually frost free crevices, holes and cracks below ground, in banks, under logs/stones or disused small mammal burrows. Common lizards are quite tolerant of cold so mortality of adults in particular is usually low throughout cold winters. Mild wet winters are thought to result in higher rates of morality in this species.

In total I managed approximately 20 adults and 12 juveniles, anecdotally some of the common lizard populations here appear to have done very well despite the poor summer, which is interesting and maybe a topic for another post.      

Adder 

In addition to lizards, it was pleasing to find a juvenile adder, one of this year's offspring and evidence of some successful breeding at the site. Amazingly juvenile adders do not feed until well into their first summer of life, spending their entire first winter living from yolk reserves, from their mother.  This stored yolk is extremely rich in protein and can enable you snakes to actually grow in the period between birth and hibernation. This individual (in the photo below) is showing another trait commonly seen in adders, and one which can make photographing them frustrating on occasions. Whilst basking adders often position their eyes into the shade, either in the shadow of a leaf or similar object or by tucking the head below their body. Adders do not have eyelids and subsequently bright sunshine can cause damage/discomfort to the eye, especially in a young snake where the eye is not fully developed.  

Juvenile adder basking in a safe area, close to cover, note the shading over the eye.

 



 

Unfortunately no slow worms were found, undoubtedly if I had dug a bit deeper and lifted some refugia I may have ound some. However due to the disturbance this causes I am reluctant to do this from late September onwards, when damage could be caused to a wide variety of creatures.