Inthisepisode,biologistPatrickAryeetravelsacrosstheAmericastoexplorethevitalrolebiganimalsplayintheirhabitats.FromAlaskatoPatagonia,hecomesfacetofacewithgrizzlybears,spermwhalesandelephantsealstorevealhowthesegiantsareshapingtheirenvironments–andevenhelpingtoreduceclimatechange.