▁may ▁be ▁from ▁ 3 4 0 ▁to ▁ 3 9 0   mm ▁in ▁length , ▁and ▁except ing ▁a ▁white ▁tip ▁that ▁may ▁appear ▁the ▁colour ▁is ▁overall ▁grey - b rown . ▁The ▁ears ▁are ▁compar atively ▁long , ▁ 4 8 ▁to ▁ 5 7   mm , ▁with ▁a ▁tri angular ▁form . ▁The ▁colour ▁of ▁the ▁ears ▁is ▁very ▁dark ▁at ▁the ▁outer ▁side ▁and ▁p ink ▁at ▁the ▁interior , ▁the ▁fr inge ▁is ▁l ined ▁with ▁silver ▁hair s . ▁A ▁hair less ▁p ink ▁rim ▁appears ▁around ▁the ▁eye . ▁The ▁weight ▁range ▁is ▁from ▁ 2 . 5 ▁to ▁ 3 . 5 ▁kil og rams . ▁ ▁A ▁similar ▁species , ▁the ▁northern ▁B ett ong ia ▁trop ica , ▁may ▁be ▁distinguished ▁by ▁the ▁lack ▁of ▁sh ag gy ▁fur ▁with ▁a ▁r uf ous ▁t inge , ▁their ▁black ish ▁tail , ▁and ▁this ▁species ▁hair less ▁p ink ▁ring ▁at ▁the ▁eye ▁and ▁point y ▁tri angular ▁ears . ▁ ▁The ▁vocal isation ▁includes ▁an ▁alarm ▁call , ▁a ▁soft ▁his sing ▁sound , ▁another ▁sound ▁like ▁a ▁ch ains aw ▁when ▁in ▁ag gress ive ▁post ures ▁and ▁they ▁regularly ▁emit ▁a ▁gr un ting ▁no ises ▁during ▁normal ▁activity . ▁ ▁Re production ▁ ▁Bre eding ▁occurs ▁throughout ▁the ▁year , ▁once ▁the ▁female ▁has ▁reached ▁m atur ity , ▁generally ▁at ▁ 1 1 ▁months . ▁The ▁male ▁reaches ▁m atur ity ▁between ▁ 1 2