Biological Journal of the Linnean Society, 9: 323-330. With 3 plates and 1 figure
December 1977
Behaviour of a young smooth snake, Coronella
austriaca Laurenti
IAN F. SPELLERBERG
Biology Department, Southampton University, Southampton SO9 5NH
Accepted f o r publication May 1 9 7 7
In August 1976 two broods of the endangered smooth snake (Coronella austriaca) were rescued
from a fire at a National Nature Reserve. This material provided a unique opportunity in which
to observe the behaviour of the young animals before they were returned to nearby heathland.
It soon became apparent that the young snakes have narrow food preferences because only the
young of lizards were taken. However, evidence is presented which suggests that later they do
take the young of small mammals as d o adult smooth snakes. Observations on other aspects of
their behaviour. such as burrowing, have helped to elucidate the complex day to day behaviour
of the adults.
CONTENTS
Introduction
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Observations
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Discussion
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Acknowledgements
References
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323
324
329
330
330
INTRODUCTION
Of the six indigenous reptile species in the British Isles (excluding the
Channel Isles), two are now protected under the Conservation of Wild
Creatures and Wild Plants Act 1975.One of these is the sand lizard (Lucertu
agilis) which is restricted in distribution to southern England but there is also a
small remnant population in north-west England, and the other is the smooth
snake (Coronella uustriaca) which has a distribution limited to southern
England. Little is known about the ecology and behaviour of the smooth snake
(Spellerberg & Phelps, 1977) and there are no published accounts which deal
with the behaviour of young smooth snakes.
In the summer of 1976, Britain experienced a very dry summer and there
were a large number of fires which destroyed vast areas of forest and heathland.
During mid-August 1976 one of these fires destroyed much of the 250 ha of
heathland at the Hartland Moor National Nature Reserve in Dorset (Moore,
323
324
1.
P. SPELLERBERG
1976). Following this fire, a rescue operation was organised by the Nature
Conservancy Council in an attempt to retrieve specimens of the rare reptiles
from the ashes before they fell victim t o avian predators. In a small way the
operation was successful in that some adults and young of both species were
collected and this then provided a unique opportunity to observe the feeding
ecology and behaviour of young smooth snakes. Information obtained and
presented here may be of considerable value in formulating future management
plans for the conservation of this species which is an important secondary
carnivore in the Dorset heathland and woodland communities. Subsequent to
being kept in captivity over the winter, the object was to return the collected
specimens to the wild and so hopefully aid the recolonization process.
OBSERVATIONS
Pre-fire status of reptiles on the Reserve
A previous fire in 1959 had destroyed part of this Reserve, but since that
time regeneration of the vegetation has occurred and it became once again an
important remnant of a formerly much more extensive heathland in southern
England. Both wet and dry heathland communities (Gimingham, 1972) were
well established and in addition to the common species Calluna vulgaris, there
were also areas of the now very restricted Dorset Heath Erica ciliaris. Particular
attention was brought to bear on the smooth snake at Hartland Moor in 1969
and since that time research by several workers has been directed at the general
population ecology of that species. From the results of mark release studies it
became evident that the smooth snake was widespread throughout most of the
Reserve, and that there were recognisable concentrations in certain areas. By
making use of data from population studies elsewhere in southern England
(Spellerberg ?i Phelps, 1977) Goddard (pers. comm.) has estimated that the
smooth snake population prior to the 1976 fire was in the region of 700 to
1050 animals. If this is a good estimate, then it was perhaps not surprising that
none of the surviving reptiles were marked animals from the population studies.
Post-fire care of young smooth snakes
After the fire at the Hartland Moor National Nature Reserve, the burnt areas
were searched commencing 26 August 1976,and on subsequent days nine adult
C. austriaca (plus one dead pregnant snake) and two broods of young (five and
eight) were collected (Plate 1). In addition t o these a total of 30 L. agilis were
rescued. The snakes as well as the lizards had apparently survived the fire by
remaining at the bottom of ‘fox holes’ (Plate 2), (the area was at one time a
military training area), in rabbit burrows, or in natural ground crevices. As the
young were in moult or had recently moulted, they were probably born during
the fire or soon afterwards: observations on other young smooth snakes have
shown that the first moult occurs within a few days following birth. The brood
of eight were found in a ‘fox hole’ which also contained a large adult female
showing signs of having recently given birth. The smooth snakes were
immediately brought to Southampton University and there retained in large
tanks containing a substratum of moist peat. Dishes of water were also
BEHAVIOUR OF CORONELLA AUSTRIACA
325
Plate 1. The five young smooth snakes photographed shortly after collection at Hartland Moor.
1
I
I
m
Plate 2. One of the holes (1 x 1.6 m) in which the young smooth snakes were found after the
heathland fire.
provided and the adult snakes readily drank during the first few hours of
captivity.
The young animals were similarly accommodated (one brood in each tank)
but one in the brood of five which had slight burns on the dorsal scales later
died on 30 August. Both tanks had water dishes, 5 cm of moist peat and one
326
I. F. SPELLERBERG
half of the tank contained the stems of Calluna. The contents from sweep
netting (spiders, crickets and flies) were introduced together with earthworms
and Tenebrio larvae. The light periods in the laboratory were similar to outdoor
conditions and a lamp placed above each of the tanks provided a temperature
in the tank of 2OoC at night and 23°C during the light period.
Four hours after being placed in the tanks, most had submerged in the peat
although from time to time some remained coiled on the surface and some
moved about briefly. A common position adopted was to have the body
submerged in the peat while the head was just protruding above the surface:
this has also been observed in the field. On the second day in captivity the tank
containing the eight young was provided with a box at one end containing
moist peat, and the substratum of peat in the remaining part of the tank was
allowed to dry. From then on it was found that, and particularly at night, the
young snakes would burrow in the box of moist peat and not in the dry
substratum. Each morning after the light came on, the snakes would emerge,
bask for about 30 minutes then move around the rest of the tank and later
return to burrow in the moist material provided.
Feeding behaviour
Up until 4 September all surviving snakes were very alert to the activity of
other animals in the tank. When a spider or cricket crossed their path, it was
investigated by a young snake, flicking of the tongue occurred but none were
seen t o feed, Many hours were spent in attempts to induce the snakes to feed
and although at times they showed considerable interest in some of the
invertebrates, it seemed that they would not feed on the animals so far
provided. On 4 September, and in desperation, a young common lizard
(Lacerta vivipara) weighing 0.44 g was placed in the tank containing eight
young and immediately all snakes approached rapidly. One grasped the lizard
about its thorax and another snake seized the lizard’s cast tail. Both snakes
with food in their mouths then swiftly avoided the other snakes and the lizard
was eaten in 20 minutes.
By 7 September it was evident that the young snakes could not be induced
to feed on anything but the young of lizards. Those which had not been given
food had on average lost 5% of their body weight (from the time of collection)
and as they were becoming increasingly active it was decided to release all but
one (that which had eaten the lizard). In collaboration with the Nature
Conservancy Council the young snakes were placed on unburnt sections of the
Reserve where it was known that a population of smooth snakes still survived.
At four weeks from the time of collection the one remaining smooth snake
was given a young legless lizard (Anguis fragilis) weighing 0.82 g and in the 7th
week (Fig. 1) it also readily accepted a 2.16 g common lizard. As on previous
occasions, the movement of the lizard seemed to act as a signal for the smooth
snake to approach rapidly and seize its prey. The second common lizard was
only a little less in weight than the young smooth snake (Fig. 1) and the
ensuing behaviour was of considerable interest. The lizard was taken by the
snake at the base of its tail while the lizard in turn grasped the snake in its jaws.
Following this, the snake then slowly manoeuvred its jaws forward along its
prey and at the same time coiled its body around the lizard. Fifteen minutes
BEHAVIOUR OF CORONELLA AUSTRZACA
327
after the introduction of the lizard, the snake had overpowered the lizard
which then released its grasp. After 39 minutes only 2 cm of the lizard’s tail
remained visible and by 42 minutes the prey had been swallowed.
After this time no further food in the form of lizards was available and by
the 11 th week the young smooth snake had once again become very active and
had lost weight (Fig. 1). It was then decided to offer the snake a new born
mouse (1.48g) in the hope that, like adult smooth snakes, it would feed on the
young of small mammals (Spellerberg & Phelps, 1977). Although the mouse
weighed very little it was bulky compared to small lizards but nevertheless the
young snake became very alert and rapidly approached the potential prey
despite that the mouse showed little sign of movement. The smooth snake
quickly used its tongue to sense the mouse and then seized it by the head
(Plate 3). It was lifted from the ground, carried over to the water dish, dipped
into the water, carried to the far end of the tank, and then slowly swallowed
over a period of 45 minutes. Two days later a further new-born mouse was
introduced to the tank but the snake showed no interest and when the mouse
was held close to the snake, the latter responded by striking but not biting. The
rejected food was then removed.
On the 13th week (Fig. 1) another young mouse was offered and this time it
was readily taken but on this occasion it was swallowed tail first (observed only
once) and the whole process took 62 minutes. From that time onwards young
mice were readily taken (Fig. 1) and provided the snake was not sloughing or
had not recently been fed, the prey was always quickly taken, carried off, then
swallowed in about 20 minutes. It became clear that this young snake could
both see its prey and also when necessary detect it by scent. Once when the
snake was submerged in the peat, a mouse was introduced and gently moved
across the substratum, it was then partially buried. Later the young snake
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328
1. F. SPELLERBERG
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Plate 3. The young smooth snake in captivity taking a new-born mouse. Note the edge of a
water dish on the left and an entrance to a burrow on the top centre of the photograph.
emerged and it was not long before it had detected the scent trail which was
quickly followed while the snake made rapid tongue movements. The prey was
soon located and 'seized.
Thermoregulatory behaviour
Three cycles of behaviour seemed to be linked to the thermoregulatory
responses of this young snake: that is diurnal behaviour, feeding and sloughing.
The diurnal behaviour of the young snake was linked closely to the lightdark
cycle. Shortly after the start of each light phase, the snake would emerge and
then bask in a coiled position beneath the lamp. This first basking interval of
the day was then followed by periods of burrowing (several shallow burrows
were constructed), movement about the tank, and shorter periods of basking.
At the end of the light phase the young snake would quickly submerge if it had
not already done so. On a few occasions the tank was examined during the dark
phase but at no time was the snake seen to be active. Periods of prolonged
basking followed each meal and usually only at night would the snake
submerge. During the next few days the basking periods gradually diminished
in duration and more and more activity occurred during the light phase.
During the time leading up to a moult, the behaviour was more complex in
that the young snake, during the light period, divided its time between short
basking periods and submergence in the moist peat. Little activity occurred
until the sloughing process had been completed.
The sloughing cycle and aggressive behaviour
Each sloughing period lasted for about eight days and during this time the
snake was usually either basking or was submerged in the moist peat. In colour
BEHAVIOUR OF CORONELLA AUSTRIACA
329
it appeared rather dull brown and when three days into the sloughing period
the eyes took on an opaque appearance. After five days the eyes became clear
and after a few days the whole skin would be shed. For a few days after the
sloughing period the snake’s new skin was a silvergrey in appearance and had a
noticeable lustre.
When active, any movement inside the tank seemed to very quickly gain the
attention of the snake. If sleeping and then disturbed, the young snake would
quickly strike and throw its body forward while its head took on a very
flattened appearance (triangular shape from above). Once when I aroused the
snake from sleeping, by gently blowing on its body, the young animal
immediately became alert, flattened its head, uncoiled and vibrated the last
2 cm of its tail. This tail movement was quite unexpected but it was very
noticeable because the vibrating portion was held well above the substratum. A
strike position was assumed and tongue movements were very rapid. It then
slowly left its basking position and submerged into one of its burrows.
DISCUSSION
Had more lizards been available, the young snake would have undoubtedly
continued to accept these as food. Previous authors such as Bund (1964) have
also remarked on the narrow food preferences of the young smooth snakes and
it has been suggested that this lack of flexibility in the feeding behaviour may
be disadvantageous for the species. A number of aspects however suggest that
there is a change in the smooth snake’s diet (in its first few years) from that of
mainly lizards to a predominance of small mammals. Information collected
over four years’ field research indicates that mammals form an important part
of the adult’s diet (Spellerberg & Phelps, 1977) whereas previously it was
thought that Lncertn ngilis was the major prey species. An examination of the
diversity and abundance of all the reptile species in several localities in England
is now underway and, in reference to food requirements of the smooth snake
populations, it seems that there is insufficient lizard biomass alone to support
the smooth snake populations. It would therefore be of considerable advantage
for this species if it were able to alter its food preferences and forage for small
mammals in addition to small reptiles. Yet at the same time this narrow
selection of prey by the young snakes may be one feature of what seems to be
a stenoecious species and one which, compared to the adder (Viperu berus)
appears to have poor powers of dispersal and colonization.
The behaviour of the young snake during feeding and particularly after it has
taken its prey, becomes relevant when viewed against a knowledge of the
adult’s behaviour. The adult smooth snakes are known to burrow in soft
substrata of heathland and woodland and they also appear to spend much of
their time submerged in the substratum or deep in the vegetation (Spellerberg
& Phelps, 1977). I t is suggested that adult smooth snakes search for the young
of small mammals such as mice and shrews and that good populations of small
mammals may be an important part of their ecology. A further aspect of the
burrowing behaviour seen in both young and adults may be linked to the
smooth snake’s foraging strategy. On several occasions they have been seen to
burrow in soft substratum and partially submerge themselves just below the
surface, but with the head exposed. It is possible that such a position could be
3 30
1. F. SPELLERBERG
used to conceal themselves from passing prey and so be part of the foraging
behaviour.
The temperature requirements of this species have been investigated and the
voluntary temperatures noted (Spellerberg & Phelps, 1975): voluntary minimum = 2OoC, voluntary mean = 27' C, voluntary maximum = 34"C. The prolonged basking periods following feeding are characteristic of snakes
(Spellerberg, 1977) and are necessary to maintain long periods of high body
temperatures which allow for efficient digestion. The association with a moist
substratum when sloughing is also important for snakes because it is probable
that it assists the process.
Compared to adders and grass snakes (Nutrix nutrix), the smooth snake is
more adaptable to the captive state and this may well be related to the
behaviour of these species which occurs when they are disturbed in the wild.
When approached, adders are very defensive, the grass snake will quickly and
noisily move away, the smooth snake is in comparison quite passive. This
behaviour may be of an advantage if it were thought necessary t o assist the
population status of this species by breeding it in captivity or by rearing the
young animals (taken from the field) with the object of assisting recolonization.
ACKNOWLEDGEMENTS
This research was supported by a scientific investigations grant from the
Royal Society. I am particularly grateful for the generous cooperation of the
Nature Conservancy Council and I thank P. Goddard, A. M. Nicholson and N.
D. Smith for their assistance during field excursions.
REFERENCES
BUND, C. F. VAN DE. 1964. De verspreiding van de reptielen en amphibieen in Nederland. Lacerta, 22:
1-72.
GIMINGHAM, C. H., 1972. Ecology ofhearhlands, 266 p. London: Chapman & Hall.
MOORE, P. D., 1976. Fire on heathland. Nature, 264: 112-113.
SPELLERBERG, I. F., 1977. Reptile body temperatures. The Herptile. (In press.)
SPELLERBERG, I. F. & PHELPS, T. E., 1975. Voluntary temperatures of the snake, Coronella austriaca.
Copeia, 1975 (1): 183-185.
SPELLERBERG, 1. F. & PHELPS, T. E., 1977. Biology, general ecology and behaviour of the snake,
Coronelb austriuca Laurenti. Biological Journal of the Linnean Sociery, 9: 133-164.