Uhamiaji wa kerengende na vipanga wanaowafuata.

(Scroll down for swahili version)

I think one of the most interesting applications of understanding what causes our weather is how it applies to some amazing phenomena. I think one of the most interesting is how a dragonfly species uses the winds created by the ITCZ to fly from India to East Africa and back.

Dragonflies are one of the most efficient and amazingly designed predators. Their larvae eat mosquito larvae and the adults prey on adult mosquitos as well as a lot of other small insects so they play an incredibly important role in the environment. One species of dragon fly called the Globe Skimmer has evolved a behavior to exploit the wet season in East Africa and the wet season in India. The rain brings about an increase in insect populations which is their prey but also breeding sites also known as puddles that don’t have predatory fish in them because they are temporary. Its life cycle in the larval stage has sped up so that it can reproduce quickly in puddles caused by rain instead of permanent water, but it has also figured out how to cross the Indian Ocean.

If you read my previous blog post about the ITCZ, you’ll know that because of the Earth’s tilt and rotation around the sun, the band of low pressure and rain is moving towards the northern tropic. In addition to creating rain where it goes, it also creates wind, and these little dragonflies have figured out how to use these winds to get back and forth taking advantage of when their prey population is highest. Using these winds, they can get from the Maldives to the East African coast in as little as 4 days. The round trip is somewhere between 14,000 and 18,000km and takes at least 4 generations. This is more than double the distance that the famous North American Monarch butterfly migrates.

These dragonflies have unfortunately not escaped from predators and especially one migrant bird called the Amur falcon. The Amur falcon breeds in eastern Asia and also time its migration to Southern Africa to take advantage of the same winds and also to travel with an amazing food source. Amur falcons also migrate into southern Africa to take advantage of the explosion of insects that emerge during the wet season. We still have a lot to learn about the dragonfly migration and I don’t know if there’s a satellite transmitter small enough and cheap enough to put on a dragonfly’s back, but we do have satellite transmitters on some Amur falcons. A few of these Amur’s have started their long flight back to Russia & China and you can check out the migration tracking maps on www.satellitetracking.eu for example here is the map for an Amur falcon called Barak.

If you would like to learn how the dragon fly migration is being studied and how it was discovered- here’s a 20 minute TED talk worth watching.

Swahili version

Ninafikiri matumizi ya fahamu yetu kuhusu mambo yanayosababisha misimu ya hali ya hewa ni kuchunguza uhusiano wake na matukio ya asili ambayo ni ya ajabu. Jambo mmoja mfano na ya kuvutia sana ni namna spishi mmoja ya kerengende (dragonfly) anavyotumia upepo unaosababishwa na ITCZ kuruka kutoka India kuja Africa mashariki na kurudi kila mwaka.

Kerengende ni kati ya wawindaji bora na fanisi angani kwa miumbile yake. Lava ya kerengende hula viluwiluwi na kerengende mzima anadaka mbu angani pamoja na wadudu wengine, kwa vile wanatenda kazi nyeti kwenye mazingira yetu. Kuna spishi mmoja ya kerengende aitwaye Globe Skimmer ambaye ana tabia ya kutumia kipindi cha mvua Afrika Mashariki na kipindi cha mvua India kinachoitwa Monsoon. Mvua huongeza kuwepo na wadudu wengi ambao ni chakula chao, lakini pia unaongeza vidimbwi vya maji visio na samaki kwa sababu ya kutokuwa vya kudumu. Mzunguko wa maisha yao kwenye sehemu ya lava ni fupi ili waweze kuzalishana kwa muda mfupi kwenye vidimbwi vya mvua badala ya maji kwenye mabwawa ya kudumu yenye maadui, lakini pia wamegundua namna ya kuvuka Bahari la Hindi.

Kama ulishasoma blog yangu iliopita kuhusu ITCZ, utafahamu kwamba mwelekeo wa dunia kulingana na jua inapozunguka jua, eneo lenye presha ndogo na mvua inahama kwenda kwenye tropik ya kaskazini wakati huu wa majira ya mvua za masika. Hii tokeo hupeleka mvua lakini hutengeneza upepo pia, na kerengende  hawa wamegundua namna ya kutumia upepo huu kuenda na kurudi kulingana na uwingi wa chakula chao. Kwa kutumia upepo, wanaweza kuruka kutoka viziwa vya Maldives kufikia pwani wa Afrika Mashariki kwa muda wa siku nne tu.Mzunguko wao mzima una urefu wa kati ya kilometa 14,000 hadi 18,000, na huchukua vizazi vinne. Safari hii ni zaidi ya mara mbili ya urefu wa uhamiaji wa vipepeo aina ya North American Monarch.

Hawa kerengende wenyewe hawajakwepa maadui na adui mmojawapo ni mhamiaji  pia ni tai aitwaye Amur falcon. Amur falcon wanazaliana mashariki mwa Asia na wanapanga kuhamia kuelekea kusini mwa Afrika kuchukua nafasi ya upepo ule ule wa ITCZ; pia husafiri akiwa na chanzo kizuri cha chakula.  Hawa ndege pia wanahamia kusini wa bara la Afrika kutega mlipuko wa wadudu wanaotoka kipindi cha mvua. Sisi baado tuna mengi ya kujifunza kuhusu uhamiaji wa kerengende na sidhani kama kuna transimita ndogo na isio yenye bei kali kumwekea mgongoni kerengende, lakini kuna Amur falcon waliowekewa transimita. Kati ya hao waliowekewa transimita, wachache waliyoanza safari ndefu ya kurudi huko Urusi na China. Unaweza kuona ramani ili kuwafuata safari yao kwenye tovuti hii www.satellitetracking.eu na kwa mfano bonyeza hapa kuona ramani ya Amur falcon ambaye anaitwa Barak.

Kama ungependa kujua namna wananvyotafiti uhamiaji wa kerengende- hapa kuna video nzuri ya dakika 20.

Sources:

Anderson, R. Charles. 2009. Journal of Tropical Ecology. Do Dragonflies Migrate Across the Western Indian Ocean?