Recently I have, once again, begun spotting grass snakes (Natrix natrix) which is one of the three snake species inhabiting Latvia.
It is not easy to find research about these snakes and I was unable to answer some of the questions that arose after my observations.
On my walks I have observed grass snakes mostly in the types of habitats that have already been described in encyclopedic data and publications (ecotones such as woodland edge, riparian areas but also open woodlands).
However, I have noticed a slight preference by these snakes regarding the specific ground cover (microhabitat feature).
More precisely, in a forest environment I frequently notice them on mosses.
In my region, riparian forests have become rather narrow strips in many places and the grass snakes can sometimes be found throughout the entire forest band or close to smaller glades / clearings.
When I have observed them in such types of habitats, I often see them basking on mosses rather than in taller herbaceous vegetation or on bare ground (covered with small-sized woody litter).
Meanwhile, when they bask on trails, bare soil is apparently selected for as it absorbs light radiation and grows warm rather easily.
I was wondering if there are, indeed, associations that such snakes (and other cold-blooded animals, e.g., lizards) truly form with specific types of ground cover or if this impression is biased due to the comparative ease of observation of the snakes on short vegetation (mosses) which is also relatively light in colour compared, e.g., to bare forest soil that can camouflage the snake better.
It might make sense for the snakes to bask on the mosses because mosses seem to be warmer than other vegetation although I cannot find publications, either, that attest to this or counter the claim.
I just know that they feel pleasantly warm to the touch compared to other forest ground covering vegetation and it might not be a consequence of absorption but rather some other heat conductive mechanism (or microclimate forming process).
In any case, mosses might be preferred to taller vegetation because taller vegetation would dissipate the radiation that reaches the levels where snakes can bask and snakes might not be able to bask as effectively around other forest floor community species as on the more exposed surface of the mosses.
I am wondering whether there is truth to my observation/impression.
Meanwhile, in our folk songs, it has also been frequently mentioned that snakes (not specifying the species) bask on tree stumps.
I have never observed snakes, e.g., on fallen tree logs or stumps or piles of dead branches but where I live, most trees that are felled are not of great size and the folk songs were probably referring to felled old-growth trees that reached sufficient diameter for a snake to rest on their stumps easily.
In the songs it was not always clear whether the habitat type would be a forest clearing or a stump inside of a forest (a result of selective thinning most likely – because I cannot imagine that windthrown trees can offer much of smooth stump area to be basking on, they break and leave rather pointy, splintery, unsmooth, uneven stumps).
However, it seems that the Latvians used to observe a phenomenon where the snakes sought to bask on objects slightly elevated above the rest of the vegetation.
Thus, open areas (trails), low growth vegetation areas (mosses) and slightly raised surfaces (felled tree stumps) might be studied for snake basking activity.
These observations and references have made me wonder whether there might be attributes to particular land covers that make some surfaces more desirable for basking than others.
I believe this is relevant because in many forests and ecotones the ground cover is changing.
With the massive input from fertilizers (eutrophication) tall herbaceous vegetation (especially, nitrogen loving species like goutweed or nettles) prevail.
Bare ground spots or low growth vegetation disappears from such forest patches.
Vast clearings predominate in forestry methods and while the folk songs cite the snake’s preference for tree stumps, large clearings might not be beneficial because they might grow too hot too early in the day.
Therefore I am wondering if these changes have affected the snakes’ basking site availability.
Notes by Ieva 