▁region ▁and ▁over take ▁native ▁species , ▁dimin ishing ▁their ▁divers ity . ▁The ▁dispers al ▁of ▁we eds ▁is ▁a ided ▁by ▁the ▁attachment ▁of ▁se eds ▁to ▁the ▁horses ’ ▁man es ▁and ▁t ails , ▁and ▁are ▁also ▁transferred ▁via ▁horse ▁d ung ▁after ▁consumption ▁of ▁we eds ▁in ▁one ▁location ▁and ▁ex crement ▁in ▁another . ▁Although ▁the ▁effects ▁of ▁the ▁we eds ▁that ▁actually ▁germ inate ▁after ▁transfer ▁via ▁d ung ▁is ▁deb ated , ▁the ▁fact ▁that ▁a ▁large ▁number ▁of ▁we ed ▁species ▁are ▁dispers ed ▁via ▁this ▁method ▁is ▁of ▁concern ▁to ▁those ▁interested ▁in ▁the ▁surv ival ▁of ▁native ▁plant ▁species ▁in ▁Australia . ▁The ▁effect ▁on ▁plants ▁and ▁plant ▁habit ats ▁are ▁more ▁pron ounced ▁during ▁dr ought s , ▁when ▁horses ▁travel ▁greater ▁distances ▁to ▁find ▁food ▁and ▁water . ▁They ▁consume ▁the ▁already ▁threatened ▁and ▁limited ▁veget ation , ▁and ▁their ▁negative ▁influ ences ▁are ▁more ▁w ides p read . ▁Fer al ▁horses ▁may ▁also ▁che w ▁the ▁b ark ▁of ▁trees , ▁which ▁may ▁leave ▁some ▁trees ▁vulner able ▁to ▁external ▁thre ats . This ▁has ▁occurred ▁during ▁dr ought , ▁among ▁eu cal y pt us ▁species ▁on ▁the ▁Red ▁Range ▁plate au . ▁It ▁appears ▁as ▁though ▁fer al ▁horses ▁may ▁prefer ▁these ▁species . ▁ ▁Inter action ▁with ▁other ▁animal ▁species ▁The ▁changes ▁in ▁veget ation ▁that ▁result ▁when ▁fer al ▁horses ▁to ▁over pop ulate ▁a ▁region ▁affect s ▁bird ▁species ▁by ▁removing ▁plants ▁upon