SearchingfortheSea

AredtideflowsfromtheforesttotheseaeveryfallonChristmasIslandinthePacificOcean.That’swhenmillionsofChristmasIslandredcrabsmigrate.Theyskittertotheseatoreleasetheireggsintotheocean.Howdotheyknowwhattodo?

Theirtrekistriggeredbytherainfall.Duringtheisland’swetseason,beginninginOctober,thecrabsabandontheirrain forestburrows.Thetimingoftheirmigrationisalsolinkedtothephasesofthe moon.

Malestravelfirst,ingreatnumbers.Theyareundeterredbyobstacles.Theyfrequentlycrossislandroads,essentiallyshuttingdowntrafficforany“migrating”humans.

Thetripusuallytakesaboutaweek.Onceoceanside,themalesdigdeepburrowsandwaitforthefemalestoarrive.Matingtakesplaceinorneartheburrows.Themalesreturntotheforest.Preciselyattheturnofthehightideduringthelastquarterofthemoon,thefemalesreleasetheireggsintotheocean.Thenthey,too,returntotheirhomes—drivenbythesameforcesthatbroughtthemtothesea.Theyounggrowupintheseaandcome tolandas adults.