The slippery snake: interview with Wietse Chanet

By what can you recognise the smooth snake?

The smooth snake(Coronella austriaca) is a non - venomous, 50 - 70 cm long snake. The animal has a dark band running from the nostril through the eye to the corners of the mouth and a brown - grey coloured back with a pattern of dark spots. The scales on the head of the smooth snake form a pattern that is unique to each individual. The smooth snake is one of two species of snakes found in Grenspark Kalmthoutse Heide, the other being the venomous viper(Vipera berus). The difference between the two species can be seen, among other things, in the back: unlike the smooth snake with its scattered dark spots, the viper has a continuous dark zigzag stripe. The eyes of both species are also different: the smooth snake has a horizontal pupil, while the viper has a vertical one.

What are the ideal living conditions for the smooth snake?

The smooth snake prefers dry areas, but can also occur near fens and in river valleys. The most popular habitat types are dry heathlands, dry grasslands, clearings in deciduous forests and forest edges. To regulate its body temperature, the smooth snake needs sites with both open and sunny areas and sheltered and shaded areas formed by small shrubs such as common heather(Calluna vulgaris) and bilberry(Vaccinium myrtillus).

How is the smooth snake monitored in Grenspark Kalmthoutse Heide?

To monitor the population of the smooth snake, volunteers go out frequently to look for the animals. They then walk along predetermined transects and look around carefully to see if they can spot snakes. They use the plate method where they check plates laid in the Grenspark under which the animals can warm up and hide. When a snake is found, the sighting is recorded in the snake portal: a website used for monitoring snakes in Belgium and the Netherlands. The sighting then includes as many variables as possible: location, time of day, observer, weather conditions, ... and when there is the possibility of prudent manipulation, gender, length, weight, etc. are also determined. As mentioned earlier, smooth snakes can be recognised individually based on their head scales. This allows observers to identify any animal found by comparing the head with photographs of the heads of known snakes in the same area. However, when the number of known snakes increases, this can be quite a task. Therefore, each identified snake is also given a label of 6 numbers, based on the location and colour of the scales on the head. After determining this unique code, observers can also add this code to the sighting they have made in the snake portal and check if and how many times the animal has already been found. This method is very useful for ecological research on the smooth snake as it causes little disturbance to the animals and allows individuals to be tracked throughout their lives.

Why is it important to monitor this species?

The smooth snake is a species protected by Belgian law and listed as endangered on the Red List for amphibians and reptiles in Flanders. Therefore, it is very important to monitor the state of populations, such as those in the Grenspark Kalmthoutse Heide, as closely as possible. However, the animals are difficult to find and observe as they make perfect use of the ground cover and vegetation structure. This leaves many questions about the demography and ecology of this cryptic species. With the monitoring of the smooth snakes in the Grenspark, more insight into the lives of these special animals can be gained, which will make an important contribution to their survival.

What did you research during your internship and what are your findings?

The aim of my internship was to analyse the number of sightings of pregnant smooth snakes in Grenspark Kalmthoutse Heide over time and to link these sightings to weather conditions. The analysis of observations over many years showed, among other things, that the number of pregnant females makes up a relatively large proportion of the total number of individuals and that the ratio of pregnant females to total snakes remains fairly constant over the years. The graphs created also show a recovery of the smooth snake population after the major fire in 2011. Finally, this part of the analysis confirmed that the smooth snakes in the Grenspark Park reproduce annually, which is quite exceptional.

The analysis of the weather during observations of pregnant smooth snakes gave the following interesting results. The average temperature during field visits when a pregnant female is found is 19.83°C, but they can be found at temperatures between 15°C and 30°C. All smooth snakes are generally more visible during cloudy skies, as they need more time to warm up, but pregnant females are seen at significantly higher cloud cover than any other smooth snake. Almost half of the studied sightings of pregnant females occurred during fully covered skies. This could possibly be explained by the fact that pregnant females need more energy for embryo development and thus need to stay outdoors longer during very cloudy days. Wind directions during field visits where pregnant females were observed were significantly different from those during field visits where either non-pregnant females or any non-pregnant animal was seen. The results show that pregnant females are observed more frequently in north-westerly and north-easterly winds and non - pregnant females and all non - pregnant animals in westerly winds. This is consistent with the frequent sightings of pregnant females under more cloudy skies, due to an unstable atmosphere under north-westerly winds, and under warm temperatures, due to north-easterly winds.

Curious about the full report? Read it here.

See a smooth snake during your visit to the Grenspark?
Send a photo with location to grenspark. This info can help us monitor the animal even better.