Human induced species of NZ and my childhood memory
বহু দিন ধ’রে বহু ক্রোশ দূরে বহু ব্যয় করি বহু দেশ ঘুরে দেখিতে গিয়েছি পর্বতমালা,দেখিতে গিয়েছি সিন্ধু।
দেখা হয় নাই চক্ষু মেলিয়া ঘর হতে শুধু দুই পা ফেলিয়া একটি ধানের শিষের উপরে একটি শিশিরবিন্দু।
I wanted to travel thousands of miles to touch top of the mountain, I wanted to cross the ocean to know whats is at its end, But didn't care to take few steps to see the morning dew on a grass leaf....
One day I was watching a documentary in discovery channel about how some species from other continent have been introduced by human in New Zealand and soon they multiplied out of control and became threat to the local species. Being a remote island far from other contents species evolved in this part of the world are quite alien to any other continents. Other than locally evaluated species, the only species could reach to this parts are those who can fly like birds, bats etc. But they also after started living and adapting an unique lifestyle over here, evolved so dramatically from their true origin, today it is difficult to imagine they belong to the same family, when they are placed beside their cousins from other parts of the world.
For example, Owl parrot, Kakapos, are very unusual parrots. They're flightless, very large - sometimes reaching 4kg in weight. Kakapos, are native to New Zealand, but now only exists, on specially protected islands, where their nests are safe from introduced vermin such as rats, stoats and feral cats. Once native to all but the highest mountain altitudes on North, South and Stewart Islands, Kakapos probably numbered in the tens of thousands. They may have flown to the islands at a very early date, long before the land split into North and South Islands, and gradually lost their ability to fly. These 2-foot-long parrots have dull green plumage, mottled with brown, that blends into the vegetation of their rainforest habitat. They are known as the Owl Parrot because of large eye discs and nocturnal habits.
After early European settlers introduced to the island, they brought mustelids over there.Mustelid is the name for the family to which stoats, ferrets and weasels belong. They were originally introduced to New Zealand to help control rabbit numbers. Rabbit numbers grew so quickly after their introduction to New Zealand in that by the 1870s they had become an agricultural pest, destroying farmer's crops and competing with sheep for grazing. Farmers demanded that the natural enemy of rabbits in England, ferrets, stoats and weasels, be imported to deal with the problem. However their own numbers have increased dramatically and created a separate problem because they also prey on native birds, eggs and chicks. Although bird experts protested at the time, mustelids were brought into the country and released onto farm land. Within 20 years their numbers had increased and they had spread into areas of native forest. By 1903 the government had changed its policy on introducing mustelids, but official protection of the animals remained until 1936.
Watching this, I remember a small incident from my early age. There was a piece of empty land at the west side of our home, may be about 100’ X 100’ size. The west and north side of the land was guarded by 6’ tall wall. The land was little low compare to our and other plots surrounding it. So during rainy season, it remains under water for 3-4 months. And there was no outlet to pass the water, so it becomes an isolated small water body for some period of year. In other time of the year, one section of this piece of land becomes our play ground for badminton and other court games as it had a very level surface. Other part was covered with small plants and bushes etc.
But during monsoon when it totally goes underwater, we get very excited that we got a pond adjacent to our home. Some time all our friends go there and wade and jump in the water and float our paper boats, have all possible fun activities of our imagination. At the deepest part it would be about 2 1/2’, so quite safe in that sense, but you have to be careful about snakes.
And during that time it was a great breeding place for all kinds of frogs, so entire monsoon time, every night, we could enjoy the endless chorus of frogs. In a rainy night that chorus makes the ambience very mystic and divine. When we were little grown up, we built a brick made room with asbestos roof. Initially build for kitchen, as in one storm, the tin roof of our old kitchen, was blown away, then on the same place this new kitchen was build. But after construction we realize it’s the most beautiful room of our house. So we started using it as a common and study room. And our monsoon time pond was just beside that room. So in my evening time memory of rainy seasons, I still can hear that chorus of the frogs. It was blessing for another reason, even being a closed water body the mosquito population was under control because of them.
In the rural area of Bengal, during monsoon, when the pond and rivers overflows, it creates lots of new stream of water at many places, and many small fishes and other water lives passes through those streams. Some of my friends used to get tempted and catch those easy preys. Most of the time, those were not of any use, other than throwing back to water. One day some of our friends decided, in spite of throwing them back, we’ll leave them in our backyard pond. And we did so, and from then, we keep doing so, if we catch any fish or collect from others.
After 2-3 weeks when it was a sunny day and water was quite clear, we noticed a big school of small fishes are swimming from one corner to other in that water body. Initially we thought it might be tadpole, we didn’t leave hundreds of fishes may be at the most 10-20. But soon realize, no they are fishes, and most likely multiplied from what we introduced. So it was very exciting thing to observe for us every day. And their visibility started increasing day by day I think they grown in thousands.
But soon after the monsoon season is over those water body started to dry up and water started getting warm during the day, and we use to see few dead fishes started floating. So fish eating birds like kingfisher, cranes started noticing them, and they stated gathering and feast on those fishes. The area was getting crowded with all kind of birds, that was another excitement for us. In few days the areas under water got shrink and the remaining water was so much crowded with fish, if you just go there with a piece of cloth you may catch as much as you want. During our bathing time, we caught some of them and leave in pond, some tried to keep in an aquarium at our home. And soon the water got dried up and our hatchery experiment was over.
Watching the program in discovery channel about NZ, I was thinking, if you introduce a species to its suitable environment in absence of its natural predator how fast they can be outnumbered, I have got a chance to see with my own eye.
Ref : www.bbc.co.uk/nature/species/Kakapo
http://christchurchcitylibraries.com/Kids/NZBirdsAnimals/Mustelids/
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