▁that ▁hearing ▁in ▁the ▁low ▁frequency ▁range ▁is ▁benef icial ▁in ▁communic ating ▁and ▁loc ating ▁pre y ▁in ▁the ▁low - visibility ▁j ung le ▁habit ats ▁where ▁these ▁c ats ▁usually ▁live . ▁ ▁Pur pose ▁▁ ▁Pr ust en ▁is ▁social ▁in ▁nature , ▁and ▁may ▁be ▁produced ▁for ▁a ▁variety ▁of ▁purposes . ▁In ▁capt ive ▁t ig ers , ▁it ▁is ▁more ▁likely ▁to ▁be ▁expressed ▁when ▁the ▁animals ▁are ▁hous ed ▁in ▁groups ▁rather ▁than ▁individually . ▁C ats ▁may ▁produce ▁the ▁vocal ization ▁both ▁to ▁each ▁other ▁in ▁gre eting , ▁or ▁to ▁familiar ▁people ▁such ▁as ▁zoo keep ers , ▁as ▁seen ▁in ▁cloud ed ▁le op ards . ▁It ▁is ▁used ▁to ▁signal ▁friendly ▁intent ▁to ▁the ▁other ▁animal , ▁and ▁is ▁generally ▁reci proc ated ▁by ▁other ▁fel ids . ▁It ▁may ▁also ▁sign ify ▁happiness , ▁as ▁content ▁le op ards ▁tend ▁to ▁be ▁more ▁vocal ▁and ▁produce ▁pr ust en ▁more ▁frequently . ▁ ▁In ▁the ▁cloud ed ▁le op ard ▁and ▁t iger , ▁it ▁has ▁been ▁observed ▁that ▁females ▁often ▁express ▁this ▁vocal ization ▁during ▁est r ous . ▁This ▁has ▁also ▁been ▁noted ▁in ▁snow ▁le op ards , ▁and ▁is ▁on ▁occasion ▁used ▁by ▁females ▁to ▁initi ate ▁m ating ▁with ▁a ▁male . ▁It ▁is ▁frequently ▁used ▁by ▁fel id ▁moth ers ▁when ▁returning ▁to ▁her ▁den ▁in ▁gre eting ▁to ▁her ▁cub s , ▁and ▁the ▁cub s ▁begin ▁to ▁produce ▁this ▁vocal ization ▁at