SCOTLAND: The Big Picture / Black grouse (Tetrao tetrix) males fighting at lek, Cairngorms National Park, Scotland, UK, April 2015.
01471299
Tony Heald / RF- African elephant (Loxodonta africana) two bulls, head pushing, Etosha National Park, Namibia. (This image may be licensed either as rights managed or royalty free.)
01470863
Roy Mangersnes / Two Muskox (Ovibos moschatus) bulls headbutting, Dovrefjell - Sunndalsfjella National Park, Norway, January.
01470879
Roy Mangersnes / Two Muskox (Ovibos moschatus) bulls headbutting, Dovrefjell - Sunndalsfjella National Park, Norway, January.
01442870
Lynn M Stone / Alpine Goats (a dairy breed) nanny goats butting heads in pasture, Poplar Grove, Illinois, USA
01697707
Tony Wu / Male Siberian flying squirrel (Pteromys volans orii) inside nest heat-butting potential rival male that was looking into nest with objective of gaining access to female inside. Hokkaido, Japan. March.