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Stag beetle and dead snail observations

Shown below is an illustrated description of some very intriguing behaviourcprepa.

DAY ONE - 20 June 2007
It all started when Brenda Bather heard the sound of a snail shell being crushed - although there was no-one nearby.
Together with her husband, Charles, they decided to investigate and surprisingly found a large male stag beetle repeatedly throwing down a dead snail. A smaller male was also showing interest in the shell but was driven away by the larger male.
Below are some photos shown exactly in the order in which they were taken by Charles.
Photo taken 20 June 2007, by Charles Bather.
Male stag beetle grabbing the snail, and lifting it quite high, ready to throw it down.
Photo taken 20 June 2007, by Charles Bather.
Male stag beetles do this kind of thing to a male opponent.
Photo taken 20 June 2007, by Charles Bather.
Note the damage inflicted to the shell.
Photo taken 20 June 2007, by Charles Bather
Shot taken a split second after the stag beetle threw down the snail.
DAY TWO - 21 June 2007
Next afternoon I was there and even though we couldn't find yesterday's large male we had no trouble in locating two more males and one female, and proceeded to test them on a number of dead snails, quickly gathered in the patio flower pots.
Photo taken 21 June 2007, by Maria Fremlin.
The first male promptly showed great interest, and with its mandibles tried to get a grip on the shell.
Photo taken 21 June 2007, by Maria Fremlin.
Showing interest in the shell contents? This male measured 36 mm excluding the mandibles, compare with the one above.
Photo taken 21 June 2007, by Maria Fremlin.
When he managed to lift it he promptly threw it down, thus repeating the previous day's performance with another dead snail.
I'm afraid but this time I was more than a split second too late and got a shot of the beetle walking away instead.
However when some liquid came out of the shell the stag beetle became very interested, lowered himself down to the ground, started tasting it, then he followed up the scent leading to the snail shell.
Click here to watch the video directly in YouTube or here to watch a shorter compressed version.
The second male, only 33 mm, was also interested but had even more trouble in grabbing his snail. The female showed no interest whatsoever in the dead snails, and the males ignored her altogether.

The snails (Helix aspersa) were probably killed by the slug repellent Neudorff, which contains ferric phosphate, but another repellent with meta-aldehyde had in the past also been used in the patio plant pots.

DAY SIX - 25 June 2007.
I tried unsuccessfully to elicit the same behaviour by testing snails killed with both substances on a couple of stag beetles picked in my garden. Again the male wasn't interested either in the snails or in the female.
We are very grateful to Charles and Brenda Bather for sharing their observations and photos.
The unique observations reported here do indeed raise an awful lot of questions. Therefore it would be important to be able to repeat them in order to explain this extraordinary stag beetle behaviour.
Is anybody out there interested in doing some future experiments? Do get in touch if, like me, you want to do some simple back yard experiments, and if so then we could follow the same protocol.

Contact: Maria Fremlin
First uploaded on December 9 2007.
Last modified: Wed Feb 3 17:49:26 GMT 2010

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