This video is called Stag beetle fight.
Daily De Gelderlander in the Netherlands reports, on 10 June 2014, that about twenty stag beetles of Sint-Jansberg nature reserve in Dutch Limburg province, and Reichswald forest in Germany bordering on it, will be provided with electronic tags.
The tags don’t harm the insects. After fourteen days, they will fall off, providing biologists with data about these beetles‘ lives.
Probably because of the mild spring weather, stag beetles in this area are active now about a week earlier than usually.
See also here.