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Mate-guarding behaviour in the stag beetle Lucanus cervus

Mate-guarding behaviour has often been observed at sap runs in the Continent with this stag beetle. What happens is that when the odd female comes for a drink of the sugary sap, the males congregate around her in the hope of mating, of course. In some cases, a male actively guards the female, which he might have mated with already or hopes to. See photo below.

Male stag beetle guarding a female against two competitors

Photo courtesy of Magnus Jakobsen. Annbo, Sweden.
June 30 2015.

In this photo the top male is guarding the female against two very big competitors; the female is facing up. But in the video below all the competitors are much smaller than the guarding male; the female is really small, though.

Mate-guarding video taken in the Veluwe, The Netherlands, 2006.
Its author wishes to remain anonymous.

As you have seen, in both places this behaviour was observed during the day.
Mate-guarding behaviour has also been reported from other countries in the Continent, including the Ukraine [1]. According to Professor Anders Møller, in the Chernobyl Park stag beetles are very plentiful during the day, which is the only time when anybody is allowed in.

If you ever see this behaviour in the UK, please, get in touch with me. I would be very interested because to hear from you; after all these years of living in a stag beetle hotspot, I have never seen it! On the other hand I have seen plenty of fights, all during the evening.

[1] - Møller, A.P. (2002)   Developmental Instability and Sexual Selection in Stag Beetles from Chernobyl and a Control Area. Ethology 108 (3): 193-204. doi:10.1046/j.1439-0310.2002.00758.x.

Acknowledgement:
Warmest thanks to Magnus Jakobsen for sharing his photo.

Last modified: Sat Jan 23 2016

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