▁resid ual ▁veget ation ▁adjacent ▁to ▁the ▁le k . ▁Le k ▁sites ▁eventually ▁became ▁abandoned ▁if ▁veget ation ▁structure ▁was ▁allowed ▁to ▁get ▁too ▁high . ▁The ▁invasion ▁of ▁wo ody ▁veget ation ▁and ▁trees ▁into ▁le kk ing ▁aren as ▁also ▁caused ▁displaying ▁males ▁to ▁abandon ▁le ks ▁( Mo yles ▁ 1 9 8 1 ; ▁Sw enson ▁ 1 9 8 5 ). ▁Mo yles ▁( 1 9 8 1 ) ▁observed ▁an ▁inverse ▁relationship ▁of ▁le k ▁attend ance ▁by ▁males ▁with ▁an ▁increase ▁in ▁qu aking ▁as pen ▁( Pop ulus ▁trem ulo ides ) ▁within ▁ 0 . 8   km ▁of ▁aren as ▁in ▁the ▁Al berta ▁park lands . ▁Ber ger ▁and ▁Bay d ack ▁( 1 9 9 2 ) ▁also ▁observed ▁a ▁similar ▁tr end ▁in ▁as pen ▁enc ro achment ▁where ▁ 5 0 % ▁( 7 ▁of ▁ 1 4 ) ▁of ▁le ks ▁were ▁abandoned ▁when ▁as pen ▁coverage ▁increased ▁to ▁over ▁ 5 6 ▁percent ▁of ▁the ▁total ▁area ▁within ▁ 1   km ▁of ▁the ▁le k . ▁ ▁M ales ▁select ▁hill top s , ▁rid ges , ▁or ▁any ▁place ▁with ▁a ▁good ▁field ▁of ▁view ▁for ▁le ks . ▁So ▁they ▁can ▁see ▁the ▁surrounding ▁displaying ▁males , ▁approaching ▁females ▁to ▁the ▁dan cing ▁ground , ▁and ▁pred ators ▁( S isson ▁ 1 9 6 9 ; ▁Mans ke ▁and ▁B ark er 1 9 8 7 ; ▁Joh ns g ard ▁