The Egyptian mongoose, Herpestes ichneumon, uses its anal gland secretion to mark objects in its home range, presumably to communicate with members of its own or other groups. Chemical analysis (gas chromatography-mass spectrometry) of the secretion showed that it contained a complex mixture of long-chain (C10-C22) carboxylic acids with varying degrees of methyl branching. All the branched acids found in females were 4 methyl substituted. Males possess an additional component that seems to be a sex specific compound 2, 4, 6, 10 tetramethylundecanoic acid, which is a major component of the secretion.