Children can have intriguing questions and when my son asked “Daddy, are there any animals in heaven and how do they get there?”, this is how I answered. Interpreting his question to mean whether there were creatures in the skies and how high they might occur above the Earth’s surface, I immediately replied “Spiders. There are spiders up there”. That was not exactly what he wanted to hear. Birds and even Santa’s “Flying Reindeer”might have been acceptable, but spiders? They don’t even have wings. And yet, spiderlings on their fine silken threads, known as gossamer, are indeed passively carried to enormous heights. In this way as “aeroplankton” they can occur on the highest mountains (where they usually die or feed on other tiny spiders and insects that become stranded there in the same way) or they may cross open water to colonize off-shore islands, something that has been reported from newly formed solid ground created by volcanic eruptions as in the Icelandic “Surtsey” for example in 1963.
Amongst the birds the most amazing feat of flying at altitude (no, it’s not the condor) is performed by geese: to be precise the Bar-headed Goose Anser indicus. Geese of this species in a 2-3 day non-stop flight twice a year, cross the Himalayas in order to reach Tibetan lakes. Direct sightings of flocks flying over the summit of Mt Everest at 8,848 m (but not the spiders that might have been carried up there by anabatic winds) have been made.
The problem facing birds at such high altitudes are formidable and the skydiver Felix Baumgartner, who jumped from a height of 39,000 m, would have known this very well I suppose. Atmospheric pressure is reduced to one third of that at sea level; the air is thinner with much less oxygen available than lower down; radiation is increased and it is extremely cold. To stay warm as well as being able to flap their wings in these conditions, the birds’ metabolism has to run at top speed – for which oxygen is essential. But oxygen is in short supply so high up there. So, how do the geese cope and solve the problem?
Like other birds, geese have special one-way current gas-exchanging lungs (something I had explained in an earlier essay), which means that as in the bag-pipe air passes in the same direction during both inspiration and expiration, allowing the lungs to extract oxygen twice as often during a breathing cycle as what other animals and humans can achieve with their tidal breathing. In addition, the Bar-headed Goose has a much lower heart rate in resting conditions than any other bird and, thus, has a great deal of reserves that can be used during flight when breathing becomes heavy and heart rate increases. Finally, the muscle cells themselves, which show an abundance of mitochondria (the so-called ‘powerhouses of an organism’s cells’) and possess large stores large of oxygen in a pigment known as myoglobin, are virtual power packs, providing the necessary energy during flight.
And it is that flight muscle of the goose, any goose really, which has one other important property: it tastes delicious too! And Christmas revellers know only too well what I am alluding to!
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2016.
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