▁are ▁missed ▁in ▁the ▁counts ▁each ▁year , ▁bringing ▁the ▁ 2 0 1 0 ▁total ▁to ▁around ▁ 1 7 0 ▁horses . ▁The ▁life ▁span ▁of ▁horses ▁on ▁C umber land ▁Island ▁is ▁approximately ▁half ▁that ▁of ▁their ▁ancest ors , ▁due ▁to ▁inf est ations ▁of ▁par as ites ▁and ▁disease . ▁They ▁also ▁suffer ▁from ▁dig est ive ▁issues ▁linked ▁to ▁the ▁ing estion ▁of ▁a ▁great ▁amount ▁of ▁sand , ▁which ▁causes ▁int est inal ▁block ages ▁and ▁ab dom inal ▁dist ension . ▁ ▁A ▁study ▁published ▁in ▁ 2 0 0 0 ▁by ▁research ers ▁from ▁the ▁University ▁of ▁Georgia ▁and ▁the ▁US ▁Fish ▁and ▁Wild life ▁Service ▁looked ▁at ▁data ▁collected ▁between ▁ 1 9 8 6 ▁and ▁ 1 9 9 0 ▁in ▁an ▁effort ▁to ▁better ▁understand ▁the ▁her d ▁dynamics ▁of ▁the ▁C umber land ▁Island ▁her d . ▁The ▁study ▁found ▁that ▁band ▁inst ability ▁was ▁high , ▁with ▁mar es ▁not ▁generally ▁forming ▁close ▁relationships ▁with ▁each ▁other ▁and ▁commonly ▁switching ▁which ▁st all ion ▁they ▁band ed ▁with , ▁and ▁ju ven iles ▁dispers ing ▁quickly . ▁The ▁research ers ▁attributed ▁this ▁to ▁a ▁lack ▁of ▁territory , ▁with ▁bands ▁frequently ▁inhab iting ▁over la pping ▁areas , ▁along ▁with ▁a ▁high ▁number ▁of ▁b ach elor ▁st all ions ▁( th ose ▁without ▁mar es ). ▁They ▁also ▁saw ▁a ▁high ▁number ▁of ▁co - domin ant ▁st all ions , ▁where ▁two ▁or ▁more ▁st all ions