The pygmy slow loris is nocturnal, although it is least active on cold, moonlit nights and is generally active on dark nights, regardless of temperature. In the wild, it is normally encountered alone, or in small groups of two to four individuals. Males use scent marking to defend territories and mark their boundaries. Females prefer to mate with males whose scent is familiar. Males will also "countermark"—mark over or adjacent to another individual's mark deposited earlier—to advertise competitive ability to females. Females actively prefer countermarking males to males whose odors have been countermarked.