▁the ▁islands ▁of ▁T ierra ▁del ▁Fu ego . ▁Its ▁habitat ▁var ies ; ▁in ▁Pat ag onia ▁it ▁inhab its ▁ar id ▁bush y ▁ste pp es ; ▁further ▁north ▁it ▁is ▁found ▁in ▁the ▁for ests ▁of ▁N oth of ag us , ▁Sax eg oth ae a ▁and ▁b am bo o ; ▁elsewhere ▁it ▁occurs ▁in ▁t us sock y ▁grass land , ▁mar sh es ▁and ▁wet ▁me adows . ▁ ▁E col ogy ▁The ▁o live ▁grass ▁mouse ▁is ▁mostly ▁di urn al . ▁In ▁grass y ▁habit ats , ▁it ▁creates ▁run ways ▁and ▁makes ▁a ▁nest ▁of ▁grass es ▁in ▁a ▁t us sock , ▁among ▁roots ▁or ▁under ▁a ▁rock . ▁It ▁can ▁clim b ▁and ▁also ▁dig , ▁and ▁in ▁Chile ▁it ▁sometimes ▁occup ies ▁bur rows ▁made ▁by ▁other ▁m amm als ▁such ▁as ▁the ▁cor uro ▁( Sp al ac opus ▁cy anus ). ▁It ▁fe eds ▁on ▁ber ries , ▁se eds , ▁sho ots , ▁leaves , ▁fung i ▁and ▁small ▁in verte br ates . ▁It ▁bre eds ▁in ▁spring ▁and ▁summer ▁and ▁l itter ▁sizes ▁average ▁five ▁young . ▁Under ▁fav ou rable ▁conditions , ▁and ▁in ▁El ▁Ni ño ▁years , ▁populations ▁can ▁increase ▁dram atically . ▁This ▁mouse ▁is ▁pre yed ▁on ▁by ▁bar n ▁ow ls ▁( Ty to ▁ty to ) ▁and ▁less er ▁horn ed ▁ow ls ▁( B ub o ▁mag ellan icus ), ▁various ▁other ▁birds ▁and ▁fo xes .