Posted tagged ‘Migration’

Butterfly antennas act like GPS!

17 November 2009

Its very easy for army officers to assume that journeying cross-country is simple. They forget that they are specially trained (in map-reading), specially equipped (with compass, GPS and maps) and there is a huge infrastructure ( of cartographers, satellites, high-quality printing presses, logistics, people to update) behind them!

Butterflies dont have maps or compasses....

Butterflies dont need compasses or maps...

Compare this with a butterfly? What could be the limits of its vision? How can it find its way across continents which are proportionally about a few hundred to thousand times larger? Without consciousness how do they do what they do?

And the only instrument they have for navigation is the sun in the sky!

...or GPS to help them migrate over areas they have never travelled before!

Lepidoptera migration is a great mystery!

Take the Monarch, for instance! This Danaid or Milkweed-family butterfly is universally known for its migration which has been well-documented and researched for over a hundred years. The state butterfly or state insect for eight American states, it is the most popular butterfly in North America.

Here’s a very nice look at the place the Monarch butterfly holds in the hearts of the American people!

Monarch Watch Spring 2009 Open House (on Catherine Sherman’s blog)

 

The Monarch (Danaus plexippus), a relative of India's Common and Plain Tigers, is a well-known migrant.

Wikipedia tells us about the Monarch’s migration that… :-

In North America, Monarch butterflies make massive southward migrations starting in August until the first frost. The northward return migration takes place in the spring. The monarch is the only butterfly that migrates both north and south as the birds do on a regular basis. But no single individual makes the entire round trip. Female monarchs deposit eggs for the next generation during these migrations.

Take the case of the population east of the Rocky Mountains. By the end of October, this population migrates to the sanctuaries of the Mariposa Monarca Biosphere Reserve in the Mexican states of Michoacán and México (the western population overwinters elsewhere).

The length of these journeys exceeds the normal lifespan of most monarchs, which is less than two months for butterflies born in early summer. The last generation of the summer enters into a non-reproductive phase known as diapause and may live seven months or more which enables it to migrate from the United States and over-winter in Mexico.

The generation that overwinters generally does not reproduce until it leaves the overwintering site sometime in February and March. It is thought that the overwinter population of those east of the Rockies may reach as far north as Texas and Oklahoma during the spring migration. It is the second, third and fourth generations that return to their northern locations in the United States and Canada in the spring.

Now,  how can a Monarch keep heading South throughout the day when the sun shifts its position from low on the horizon to its highest point at mid-day and again low in the evening?

As the Sun moves across the sky during the day, the Monarch must continuously adjust its calculations so that it does not waver from its chosen direction – South!.

Scientists have now found the key to the Monarch’s genius. It’s in the antennae!

The antennae of the Monarch play a vital role in navigtion during migration.

Researchers at the University of Massachusetts Medical School held the butterfly wings gently and dipped their antennas in enamel paint. They painted the antennas of one set of Monarch butterflies with black paint (which blocked both light and smell) and the antennas of another set were painted with clear paint (which blocked smell but permitted light).

The Monarchs with clear-painted antennas found their way around while those whose antennas were painted black-painted got lost!

That not only showed the antennas were sensing light for navigating, it also showed that the sense of smell isn’t involved in finding the way, since both paints blocked that ability.

And, since the animals with black paint got lost even though their eyes were able to see light, the researchers concluded the antennas were vital to finding the way.

Butterflies whose antennas were surgically removed also became disoriented.

Now how does this work?

In 2008, scientists of of the University of Massachusetts Medical School discovered that Monarchs have ancestral circadian clock mechanisms in their brain which tell them the relative time of the day. This circadian rhythm is formed by the production of and complex biochemical interaction of cryptochrome proteins, which act as critical components in the circadian clock mechanism. Two cryptochrome proteins, named Cry1 and Cry2 were also thought to connect the clock to the sun compass somehow for successful navigation.

This year, the new ‘antenna-painting’ study by this team proved that this sun compass was located in the antenna. Apparently, the antenna sun-compass gives Monarchs the ability to detect the position of the sun and the direction of polarized light.

Gif showing the great wanderings of the Monarch generations! (click to see the gif in action)

When this information is combined with time information from the circadian clock, monarchs are able to steer a course to the South each day and eventually to find their way from all over North America to the Mexican highlands, where they spend the winter.

Read more about it here and here!

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The winter visitors are here!

8 February 2009

The CTW Lake, CME, Dapodi in Oct 2008

The hottest thing happening in town is that hundreds of really good-looking birds are here all the way from Russia, Siberia and Central Asia and having a great time at our very own lakes. And with the decline of Pune’s traditional wetlands of Mula Mutha and Pashan, for Pune’s wildfowl, CME is the happening place in town.

A flight of resident Spotbill come into land.

A flight of resident Spotbill come in to land.

Our staid resident community of a three hundred Spotbill duck have been enlarged by the arrival of almost a thousand migratory duck. The first which you will notice when peering over the embankment of the CTW Lake are the bright chestnut Ruddy Shelducks, known in India as Brahminy Ducks, the giants of the duck community. Faithfully organised in spouse-pairs, they stand uneasily amidst the hoi-polloi of hundreds of Northern Shovellors with brown heads down into the water, their boat shaped bills trawling relentlessly for snacks and their tails wagging as they go about their dodgem race to get at the good stuff.

The ruddy shelduck in full splendour over the CTW lake.

The ruddy shelduck in full splendour over the CTW lake.

Interspersed amongst them are the Northern Pintails with purple necks and a beautiful white stripe running down their seductive neckline and pointed tail feathers which give them their names. Smallest of all are the Common Teals, their males looking anything but common with shining green and brown heads.

In between the crowd, a few strays – a forlorn female Nakta or Comb Ducks, her white-woolly body peppered with black spots, looks all around in vain for the prominent combed beak of the males of her species. Someone didn’t give her quite the right directions! And all around this fish-market are the cheeky brown Little Grebes or span Dabchicks who dare each other as to how close they can get to this frightful human who thinks he’s invisible to the birds by being half-defiladed behind the bund. Amidst these, bob the plump-staid Coot, residents of CME, looking distraught at the riff-raff which arrives each season. Over head, the Grey Herons and Painted Stork are unimpressed, they have seen all this before. What is much more important is to decide whether he/she should invest in a time-share at this fish-abundant but crowded spot or go to another beckoning shallow with uncertain fish and no jostling neighbours. The Black-headed  White Ibis have no such qualms about fratenising with their cousins, a flock of Glossy Ibis.

The Purple Swamphens who entertained us all summer by their bumbling antics are now joined by the more prim and proper Common Moorhens. The Pheasant-tailed Jacanas, always a treat to watch, are now mostly gone; they don’t like the wood and leaf-smoke which is the characteristic odour of winter in our campus and do not hesitate to make their displeasure known.

The clearing of brush-wood by the roadside has deprived many dozens of Great and Little Cormorants of privacy, shade and perch and they have moved out of CME to the Mula river. However, their absence was not missed as a new bird appeared on the scene in Pune – the Darter or Snake-bird, a pair of which were recently seen at the Middle Lake opposite the Sailing Club.

Record shot of  Darter at Upper Lake, CME by Girish Vaze

Record shot of Darter at Upper Lake, CME by Girish Vaze

The hottest chick in town was undoubtedly the solitary svelte Greater Flamingo which daintily trawled her upside-down head waggling her pink body in the tasty swallows in the upper lake. But her arrival put a frown on the foreheads of the bird-watchers – are the CME lakes turning brackish, as every-one knows flamingos are only found at sea-shores and brackish lakes.

However, where duck are plentiful, the birds of prey follow, in our case a pair of Marsh Harriers with gorgeous chestnut coloured neck head and shoulders, causing waves of duck to alarm and fly off as they carry out a low vigil over the reed-filled shorelines.

The Marsh Harrier on patrol.

The Marsh Harrier on patrol.

It is getting late now. A flight of elegant Black-winged Stilts resembling the chic models of Vogue as they cross their legs in the shallows, are disturbed by two pesky Green Sandpipers who buzz them as they spot the raconteurs. A flock of 150 Wire-tailed Swallows and Red-rumped Swallows hawk insects in the reddish glow of dusk as some birds take off – a few for their nightly outings for feed, others en-route to communal roosts on the riverside, while the rest settle down in a low muttered squabble for the night.

Hush, night falls in paradise!

( First published in CME Weekly in Nov 2008 )

(Note: Text available under GFDL or Creative Commons Attribution 3.0 . Images  are copyrighted by the authors. Email addresses of Gaurav Purohit and Girish Vaze available on request.)