Ndege huyu hulala akiwa anaruka

Ndege aitwaye frigatebird anaweza kubaki angani juu ya bahari kuu kwa siku kadhaa mfululizo. Hawezi kutua majini, kwa sababu manyoya yake hayazuii maji, hivyo hashuki tu. Hilo huibua swali dhahiri. Analala lini?

A frigatebird can stay in the air over open ocean for days at a time. It cannot land on water, because its feathers are not waterproof, so it simply does not come down. That raises an obvious question. When does it sleep?

Watafiti walijibu swali hilo kwa kuwaweka ndege hao vipimo vidogo vya ubongo na kuwaachia waruke. Ndege hao waliruka hadi siku kumi bila kusimama. Walilala wakiwa angani, na mara nyingi nusu tu ya ubongo ndiyo iliyolala kwa wakati mmoja, huku nusu nyingine ikiwa macho na jicho moja likiwa wazi. Walipokuwa wakizunguka juu kwenye hewa ya joto inayopanda, nusu iliyokuwa ikiangalia mzunguko huo ndiyo mara nyingi ilikuwa macho.

Researchers answered it by fitting small brain recorders to frigatebirds and letting them go. The birds flew for up to ten days without stopping. They did sleep in the air, and often only half of the brain slept at once, with the other half awake and one eye still open. When they were circling upward on warm rising air, the half watching the turn tended to be the half still awake.

Kiasi ndicho kinachoshangaza zaidi. Baharini ndege hao walilala dakika arobaini hivi katika siku nzima, kwa vipande vifupi vya sekunde chache kila kimoja. Ardhini ndege hao hao walilala zaidi ya saa kumi na mbili. Hivyo wanaweza kuishi kwa usingizi kidogo sana kwa wiki nzima, kisha wanarudi nyumbani na kulipa deni lote la usingizi.

The amount is the surprising part. Out at sea the birds slept about forty minutes in a whole day, in short bursts of a few seconds each. Back on land the same birds slept more than twelve hours. So they can run on almost no sleep for a week, and then they go home and pay it all back.