It’s a snake-eat-snake world: Predation on an adder (Vipera berus) by a smooth snake (Coronella austriaca) in a nature reserve in the north of the Netherlands

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Vipera berus (Linnaeus, 1758), the adder, is a medium-
sized viper (total length usually up to 65 cm, rarely up to
90 cm) that has the widest distribution of all terrestrial
snakes. It is also the northernmost snake in the world
with populations north of the Arctic Circle (Anderson,
2003). Its range extends from the Atlantic coasts
of Great Britain and France in the west to Sakhalin
Island north of Japan in the east, and from northern
Scandinavia in the north to the Balkan Peninsula in the
south (Schiemenz, 1985; Mallow et al., 2003; David
and Vogel, 2010). Within Europe the adder has a patchy
distribution within the southernmost parts of its range,
where populations are often confined to higher elevations
(Schiemenz, 1985; Speybroeck et al., 2016). In the
Netherlands this species is restricted to specific areas
on sandy soils in the eastern part of the country where
it mostly inhabits heathlands and moorlands (Creemers
and van Delft, 2009; van Delft and Janssen, 2015).
Coronella austriaca Laurenti, 1768, the smooth snake,
is a medium-sized colubrid (total length usually up to 70
cm, rarely up to 90 cm). Its range extends from Portugal
in the west to the Ural Mountains in the east, and
northwards to southern Scandinavia. Towards the south,
it reaches the Balkan, Iberian and Italian Peninsulas, and
also some Mediterranean islands such as Sicily (Santos
et al., 2008; Speybroeck et al., 2016). Like the adder
this species is confined to mountainous areas within its
southernmost part of its range in Europe (Speybroeck
et al., 2016). In the Netherlands the smooth snake, like
the adder, is confined to sandy soils and mostly found
in heathlands and moorlands with the adder covering
43% of the 1x1 kilometre grids that are inhabited by
the smooth snake (Creemers and van Delft, 2009). This
rather elusive snake is known to detect its prey by means
of chemosensory perception of preferred prey types
(Amo et al., 2004; Pernetta et al., 2009). The diet of the
smooth snake mainly consists of lacertid lizards, shrews
and small rodents (Goddard, 1984; Rugiero et al., 1995;
Reading and Jofré, 2013). The typology of consumed
prey changes depending on snake size, with small snakes
usually taking more lacertids than small mammals and
vice versa for large snakes (Reading and Jofré, 2013).
Although this species is known to occasionally feed
on other snakes, including vipers (Rugiero et al., 1995;
Luiselli et al., 1996; Reading and Jofré, 2013), the
predatory behaviour is rarely observed and not much
is known about the specific predation process. In the
present contribution, the author reports a rare observation
of an adult smooth snake feeding on a juvenile adder.
On 5 September 2017, at 15:04, the author made the
observation during a survey for a long-term population
study on both species. The survey took place in
the Fochteloërveen in the border area between the
Province of Friesland and the Province of Drenthe (the
Netherlands). The Fochteloërveen is a large peat moor
area where smooth snake and adder habitats overlap
almost entirely. The habitat where this event took
place consists of old heathland on a sandy ridge with
dominating plants being common heather (Calluna
vulgaris) and purple moor grass (Molinia caerulea).
The two snakes were completely exposed in a narrow
clearing in the heather. Based on the time of year and
body size the adder was at most a couple of weeks old
and approximately 15 cm long. The smooth snake was
an adult with a total length measuring approximately
55 cm. Both snakes were not handled and distance was
kept to prevent disturbing the predation process while
recording the event. On encountering both snakes, the
smooth snake had just grabbed its prey by the back
Herpetology Notes, volume 11: 729-731 (2018) (published online on 31 August 2018)
It’s a snake-eat-snake world: Predation on an adder
(Vipera berus) by a smooth snake (Coronella austriaca) in a
nature reserve in the north of the Netherlands
Jelmer Groen1,*
1 Ecological Consultancy FaunaX, Badweg 40, 8401BL,
Gorredijk, The Netherlands.
* Corresponding author. E-mail: jelmer_groen@hotmail.com

Jelmer Groen
730
of the head attempting to constrict it, and the adder
was struggling to release itself (Fig. 1A). The smooth
snake seemed to have difficulties subduing its prey by
constrictions, resulting in the snake loosening its grip
with the upper half of its body, enabling it to stretch
and twitch its prey’s neck, slowly immobilising it while
retaining the same position (Fig. 1B-D). Eight minutes
after the approximate initial attack, only the adder’s
tail was still moving. The smooth snake didn’t loosen
its grip any further during the remainder of the attack.
Caudal movements of the prey stopped more than an
hour after the initial attack. Only after this, the smooth
snake fully loosened its grip (Fig. 1E) and the adder
was swallowed (Fig. 1F); a process that was completed
in three minutes. The process from the moment of the
initial attack to consumption of the prey took 1 h 21 min.
Figure 1A-F. A Smooth snake (Coronella austriaca), total length approximately 55 cm, observed while predating on a juvenile
adder (Vipera berus), total length approximately 15 cm, in the nature reserve Fochteloërveen, Province of Friesland, the
Netherlands.

To the best of the author’s knowledge, this is the first
detailed report of a smooth snake predating on an
adder. It is not known, if the way the smooth snake
immobilised the adder is typical behaviour for this
species. An anecdotal but similar observation (Peter
Keijsers, personal communication) suggests that at least
in some cases no constriction occurs and a juvenile
adder might be swallowed without any effective form
of immobilisation, completing the process in a much
shorter time frame, but with a higher risk of being bitten
for the smooth snake. Future records can shed more
light on this question.
Acknowledgements. The field survey, during which this
observation was done, was carried out under the permit
FF/75A/2016/015 issued by Reptile, Amphibian and Fish
Conservation the Netherlands (RAVON), and with a permission
from the nature association Vereniging Natuurmonumenten. I
would like to thank Pedro Janssen for writing a pre-peer review.
I am also grateful to Tariq Stark for his comments to previous
versions of this article and correcting the English text. I thank
Vaclav Gvozdik for comments on the manuscript.
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Accepted by Vaclav Gvozdik