Behaviour

The grass snake has at its disposal a whole range of ways how to defend or protect itself when attacked. (among others Hediger 1971, Heußer & Schlumpf 1962, Kabisch 1978, Mertens 1946).

Individual reactions and ways of behaviour for warning and threatening of the grass snake are explained in the following paragraphs. They are divided into the following titles:
 

Reactions of flight:

"Early evading"

Flight

"Slipping away during handling"

Emptying of postanal gland

"Rotation about its own axis"

Aggressive behaviour:

Symbolic stab

"Cobra position"

Biting

Defensive behaviour:

"Warning darting of tongue"

Throwing up nutrition

"Coiling"

Pretending to be dead

Issuing of blood (Mucous membrane of the mouth)

Unusual threatening and warning behaviour:

Vibrating of the tail

"Sidewinding"

"Jumping"

Complex behaviour

Description of terms

During this project quantitative data have been collected only regarding the ways of behaviour described below which were given the following short titles (also in the graphics):

"Zero – Hissing – Attacking – Pretending to be dead – Issuing of blood – Cobra Position – Sidewinding "

"Zero" – No visible threatening or warning reaction; those grass snakes which emptied their postanal glands, excreted excrements or tried to "slip away" were also considered to belong under category "Zero".

"Attacking" – is equivalent to the "Symbolic stab".

Warning and threatening reactions during catch and mapping

Table 28 describes the reactions of the grass snakes in Wuppertal, Solingen, Wipperfürth and Mettmann during catch and mapping. Animals which are not autochthonous were excluded (Natrix n. persa and Natrix n. scutata).

Table 28: The figures refer to the horizontal lines only. A threatening and warning behaviour was often observed successively during mapping; this behaviour is included in the table.

n = Number of grass snakes; divided into female, male and juvenile grass snakes; Zero = no visible threatening or warning reaction(s), except emptying of postanal glands and/or excreting of excrements; Hiss(ing) = loud hissing with dorsoventrally flattened head and fore body; Attack(ing) = "Symbolic stabs" flat over the ground with closed mouth and s-shaped fore body; Dead (pretending to be) = with opened mouth and slackened muscles as well as presenting part of the belly; Blood (issuing of) = blood mixed with saliva issued from the opened mouth, only animals pretending to be dead. Cobra (position) = with upright fore body and flattened head, attack with loud hissing; Bite(ing) = bites aiming at the hand; Sidew(inding) = way of moving of snakes which live in deserts: rapid forward movement of the body touching the ground at only two or three spots.

"Early evading"

If the grass snake realises a thread early enough, it slowly withdraws into nearby hiding-places (holes of small mammals, cavities between stones etc.) when approached up to a distance of 8 metres. Since the snakes move slowly and calmly through the vegetation during this evading behaviour very often they are not noticed.

"Flight"

I suppose (basing on observations in the open land) that grass snakes which try to get away with a lot of noise when approached up to a distance of 1 – 0,5 m have been surprised during sleep and therefore show this strong and unplanned behaviour. Very often these animals fail to hide in a nearby spot or actually "throw" themselves into the water.

Since snakes are not able to close their eyes it is difficult to see if they are really asleep. In a terrarium I have observed that the snakes follow movements near their head with their eyes and that the pupils change their diameter during focussing. On the other hand, if the snakes were laying still with glassy pupils and then startled, their flight reaction was much stronger even with animals used to a terrarium.

"Slipping away during handling"

During handling many snakes tried to get away by means of a "normal sneaking away" without showing any other visible reaction. This behaviour varies a lot depending on age and sex: female snakes showed this behaviour in 7,7 % of situations, male snakes in 21,3% and juvenile snakes shorter than 30 cm in more than 71 % of 206 situations in total.

Emptying of postanal glands

During catch and mapping the snakes often emptied their postanal glands. These glands end in the cloaca and secrete a fetid liquid. The stench lasts for several hours and is also difficult to wash away. Due to anatomic reasons, female snakes have larger postanal glands and secret more liquid than male snakes [KABISCH 1978]. At the same time, the snakes often emptied their bowels. Young animals showed this behaviour less often than adult ones.

"Rotation about its own axis"

During handling several grass snakes (less than 8 animals in total) tried to free themselves by rotating about their own axis. Not only a Natrix n. scutata (Russian grass snake) which was found in Monheim showed this behaviour but also an adult female snake from Kohlfurth. When held by its tail, the snake threw around its fore body by 360 degrees and transmitted this movement to the end of its body in order to get out of the grip.

Aggressive Behaviour

"Hissing"

The throat region swells and the grass snake audibly sucks up air. Body and head are flattened dorsoventrally. With a loud hiss that can be heard even in a distance of approximately 3 metres the snakes pushes the air out again.

16 % of 382 grass snakes in total showed this reaction. Again, in 61 cases a difference according to sex can be found because 59 % of the female snakes but "only" 26,2 % of the male snakes showed this behaviour, the remaining 14,8 % were juvenile animals with less than 30 cm total length. Hissing is a independent reaction only up to approximately 30 % which often occurs together with the "symbolic stab" or before akinesis.

Symbolic stab

Another reaction to a direct threat is stabbing with the head or the fore body. This always happens with a closed mouth and very often with loud hissing. The "symbolic stab" is made low over the ground and the enemy is always missed by several centimetres.

This behaviour is very impressing especially regarding large animals and it is also maintained over a longer period of time until the threat does no longer exist for the snake. After this reaction several animals run away or pretended to be dead.

"Cobra position"

In this position the snake vertically erects up to a third part of the total length of its body and hisses loud with its head flattened in a horizontal position (with closed mouth). The end of the body remaining on the ground moves on the spot in a "winding way".

The cobra position distinguishes itself from the "Symbolic stab" by the fact that the snake stabs forwards with its body upright and therefore the stab also has a downwards direction. The "symbolic stab" is usually made from a position where the grass snake is coiled together like a plate and the throat formed like an S. The head makes a rapid forward movement parallel to and with a low distance to the ground. A 96 cm long female snake was mapped four times in 1987 and has been found dead on the 27^th of October 1987. During the attempt to catch her on the 20^th of August 1987 the snake erected herself to a height of approximately 30 cm and conducted feint attacks on the spot with a strongly flattened head which had an almost triangular shape seen from above. During other mapping attempts she only hissed and then pretended to be dead. This "cobra position" has also been observed with a three-days-old grass snake, just to mention another example. When it was released the one-week-old animal erected its body and hissed.

The cobra position was used by 6 snakes during 382 mapping situations; three of them were juveniles.

Biting

The grass snake bites very seldomly (Kabisch 1978). During the investigation only two of the registered grass snakes did bite (< 0,5 %). An adult female snake which was injured and taken care of by me for several month bit me in the hand short before releasing her. The grass snake showed this behaviour only once during approximately 10 minutes. In order to exclude an "error" of the snake I immediately allowed her to bite me in the other hand five times. As opposed to Sievers [1959] I was not able to state pain or a numb and persisting feeling (poisoning) in the bitten extremities.

A male grass snake from Wipperfürth-Unternien bit my son into his hand when he wanted to release it at the habitat.

Defensive behaviour

"Warning darting of the tongue"

The aposematic darting of the tongue [amoung others Luttenberger 1978] where the tongue is swung around slowly up and down in a half circle and the tongue is extremely stretched out and the tips are wide apart, was observed only a few times by the mapping team.

Throwing up of nutrition

Some grass snakes regurgitated (threw up) their nutrition during handling or when persistingly disturbed. Some snake regurgitated already in the bag during transport. Even salamanders and frogs which had already been almost digested and were therefore difficult to be recognised were spit out.

"Coiling"

Several grass snakes curled themselves up hiding their head under the loops of their body. They remained in this position up to 20 minutes. This coiling is always the end of a reaction chain (after "hissing" or "attacking"). When the snakes were coiled up it was possible to take them up and they did not change their position. Unfortunately, this behaviour was not properly recorded during the project so that it is not possible to make a quantitative statement. According to my estimations, less than 10 animals showed this behaviour.

Akinese

(Pretending to be dead, "Death - feigning", "Tonic immobility" ). During handling 23,8 % of the snakes pretended to be dead. This behaviour was triggered only by touching them. The snakes did not all react with the same strength. Some animals coiled up and opened their mouth a little bit. Often the tongue was lolling out at the side of the mouth. Other snakes turned their head to the side with "stiff pupils turned to one side" and opened their mouth, sometimes with completely relaxed body muscles. A more intense reaction is the presentation of the black and creamy coloured underside, showing either only the throat area or almost the whole ventral side down to the cloaca. The snakes pretended to be dead between 2 minutes up to half an hour. When the grass snake did not feel threatened any more it darted its tongue several times and a short time later it went to a hiding spot.

Hediger [1971] writes: "Being motionless (akinesis) alone can only protect against enemies which are exclusively looking for moving prey... Therefore, the objective of pretending to be dead is to induce the enemy to give up its position of attack and reduce its attention".

In contrast to Heusser & Schlumpf [1962], who did not think that this behaviour (akinesis) was characteristic for a certain age, the local young animals did pretend to be dead more scarcely than adult ones.

"Issuing of blood"

Only snakes which pretended to be dead showed this behaviour; that is 4,7 % of all registered animals. The grass snake issues blood with its mouth open and the blood mixes with saliva. The colour of this blood/saliva mixture varies between a light rose and dark red. The strongest reaction of one male snake was to let several drops of dark red blood run out of the side of its mouth. With 23,3 % the male snakes showed this behaviour more often than the female snakes with 18,5 %.

Unusual threat and warning behaviour

"Vibration of the tail"

A grass snake vibrates with the end of its tail against the ground and causes a clearly audible sound with this. The grass snake showed this behaviour when I approached the snake up to a distance of less than approximately 80 cm. I had put down the snake on a stone covered with green in order to take a photo of it. The vibration of the tail was observed only in this animal and has not yet been described for the grass snake in general, as far as the author knows.

"Sidewinding"

Mosauer [1932] calls this behaviour also rolling movement: basically, it is a spiral rolling to one side because a wire spiral with a little more than two rounds would leave the same strange tracks as a sidewinding snake. "Sidewinding" is the method of locomotion which the snake uses on a smooth surface (e.g. by some North-American snakes, adders as well as the common adder): ... forward movement of the body touching the ground at only two or three spots. Mosauer thinks it is very surprising "that a water snake (Natrix rhombifera, today Nerodia rhombifera) is able to perfectly sidewind in a well co-ordinated way". Up to the present, the author does not know about any other case of sidewinding in grass snakes. A behaviour which is very similar to sidewinding is described by Nöllert & Ritter [1981]: "...often the body slings were raised from the ground so that the snake sometimes had very little contact with the ground "

The first grass snake (K84) in the year 1990, a 38-cm-long female snake showed this behaviour. On the 16^th March 1990 it attacked me several times in succession in a "sidewinding way", although there was no obstacle to a flight in another direction. This grass snake moved on a cool asphalt road with surprising speed.

"Jumping"

Others reported this behaviour several times to the author but only a member of the Wuppertal BUND Herpeto Group was able to give a sufficiently detailed description of this behaviour. During a very hot day in the region Siegerland near Hilchenbach in the area Lützel Ginsburg approximately in 1980 during a journey in a car, the driver Schöneweiss and the front passenger twice observed a grass snake which really jumped over the hot asphalt. Their bodies did not touch the street or only with the end of its tail. As far as it was possible to see, the snakes were not threatened or persecuted [Schöneweiss, oral comm. 1991].

Complex behaviour

For Wuppertal, quantitative data were collected separately according to sex (51 male, 55 female) during 106 registrations according to the following behaviour patterns in terms of their succession and combination:

"Zero – Hissing – Attacking – Pretending to be dead – Issuing of blood – Cobra position - Sidewinding "

Of the above mentioned grass snakes 71 showed a reaction. 35 of the snakes showed combined behaviour patterns, in the following called "multiple reactions" where the behaviour patterns were parallel or in succession as follows:

Four behaviour patterns 1 grass snake

Three behaviour patterns 10 " n

Two behaviour patterns 24 " n

One behaviour pattern 71 " n

Symbolic stab - Only two female snakes used stabbing as a single reaction. In combination with other behaviour patterns 13 grass snakes made a symbolic stab, 10 of them female snakes. Only five snakes (33 %) showed this behaviour as a "last action" (two showed it as an "individual reaction" and three snakes "hissed" during this behaviour); regarding the other 10 animals the stab was followed by other reactions (pretending to be dead, cobra position, etc).

Cobra position - was not shown as an individual reaction. Out of the 5 grass snakes (1 male, 4 female) which showed this behaviour, 2 animals passed over to akinesis.

Pretending to be dead - As an "individual" (n = 22) or "last reaction" (n = 29) 51 out of 106 grass snakes pretended to be dead. The proportion of sex changed significantly from "individual" to "multiple reactions"

Hissing with following akinesis is the "sequence of reaction" which was found most frequently (11 animals). The percentage of dead feints as an individual or combined reaction differs according to sex.

Issuing of blood - During akinesis 10 grass snakes issued blood from their mouth tissues (6 male, 4 female). These animals did not use the cobra position and only once showed the reaction "symbolic stab".

Behaviour of different populations

The existing data does not allow a precise statement about adult grass snakes. Only the number of registered juvenile snakes with less than 30 cm total length allow this statement for animals in Wuppertal and Solingen.

Of the animals in Wuppertal 24 % showed another reaction than "Zero" while only one animal (2 %) "pretended to be dead". It would be interesting to compare this data with other surrounding areas as well as with data from areas were the nominate species as well as the western ringsnake can be found "pure".

Environment temperature as important factor of behaviour patterns ?

On the 5^th July 91 B. Dreiner discovered a 32 cm long grass snake resting on an asphalt road in Wuppertal Marscheid (Air temperature 26 – 28 °C. When a hand was moved in a distance of 30 – 40 cm the pupils did not change, only when approached up to 10 – 15 cm the snake flinched and tried to flee.

In the evening, the grass snake was "mapped" with an air temperature of approximately 23 °C. During handling the snake pretended to be dead with completely relaxed muscles and issued some blood out of its mouth.

The following day at 14 o’clock and a room temperature of approximately 32 °C, the grass snake was supposed to be taken out of the terrarium again. The snake made several feint attacks with heavily flattened head and loud hissing in the cobra position, but the attacks always "missed" the hand on the left side by approximately 35 –45 cm  In the evening and a temperature of approximately 20 °C there was no visible reaction during handling when the grass snake was released at the spot where it was found.
 

Extracts from (without tables and charts): Eckstein, H.-P. [1993]. Untersuchungen zur Ökologie der Ringelnatter (Natrix natrix) - Jb. für Feldherpetologie, Beiheft 4, 145 Seiten (69 Abb. u. 42 Tab.), Verlag für Ökologie u. Faunistik, Duisburg

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