Both males and women clearly show a flehmen response, a characteristic grimace, when sniffing urine markings, but flehmen is a lot more often linked with males detecting the markings made by tigresses in oestrus. Tissues from aged people clearly show a reduce in enzymatic activity of the proteins of the respiratory chain. It now mostly occurs in the Indian subcontinent, the Indochinese Peninsula, Sumatra and the Russian Far East.