Saturday, September 26, 2009

Indian Spiders

Sunday article by Mohan Pai
Indian Spiders
Pic courtesy: Sandilya Theurkauf
Cobwebs of deception
In the gathering light of dawn, an orb-web spider sits motionless in the centre of its web. The web is one of nature’s most ingenious traps - woven from at least six types of silks and constructed with mathematical precision. But spiders are so short-sighted that they can barely see their webs. Instead they build them by touch, and instinct guides their every move. Weight for weight, spider’s silk is stronger than steel. Even so, webs soon get damaged and need to be repaired. When the damage gets too great, a spider instinctively knows to give up on repair work, and start afresh. It eats up the old web so that it can digest and recycle the silk. Each kind of spider always makes exactly the same kind of web.
‘Come into my parlour...’
Spiders are generally regarded as predatory. The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations. Females of the water spider Argyroneta aquatica build underwater "diving bell" webs which they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling. Spiders (order Araneae) are air-breathing chelicerate arthropods that have eight legs, and chelicerae modified into fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms. Spiders are found world-wide on every continent except for Antarctica, and have become established in nearly every ecological niche with the exception of air and sea colonization. As of 2008, approximately 40,000 spider species, and 109 families have been recorded by taxonomists. However, there has been confusion within the scientific community as to how all these genera should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.
Spiders are abundant and widespread in almost all ecosystems and constitute one of the most important components of global biodiversity. Spiders have a very significant role to play in ecology by being exclusively predatory and thereby maintaining ecological equilibrium. Many spiders feed on noxious insects like houseflies and mosquitoes which are vectors of human diseases. A large number of spiders are found in agricultural fields and thus play an important role in controlling the population of many agricultural pests. Despite this importance, spiders are largely neglected mainly due to ignorance and fear and the subsequent dislike for them. Although more than 1400 species (quite a number is endemic) have been described from India (and many more to be documented), the study on the taxonomy, biology and ecology of Indian spiders remains neglected.
Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of silk glands within their abdomen. Spider's webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appear in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets.
True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving order, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic period, before 200 million years ago. Most known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Spiders' guts are too narrow to take solids, and they liquidize their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the aggressive widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers.

References: Wikipedia, Spider information
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Saturday, September 19, 2009

Vanishing Species: Indian Otters

Sunday article by Mohan Pai

Indian Otters

Photo: courtesy: K. Pichumani

Playful creatures, a group of Otters is called ‘romp’, being descriptive of their playful nature.

Otters are semi-aquatic, fish-eating mammals. The otter subfamily Lutrinae forms part of the family Mustelidae, which also includes weasels, polecats, badgers, as well as others. With thirteen species in seven genera, otters have an almost worldwide distribution. They mainly eat aquatic animals, predominantly fish and shellfish, but also other invertebrates, amphibians, birds and small mammals.An otter's den is called a holt or couch. A male otter is a dog (otter), a female a bitch (otter), and a baby a whelp or pup. The collective nouns for otters are bevy, family, lodge or romp, being descriptive of their often playful nature, or when in water raft.

India is home to three species of otters: the Eurasian otter (Lutra lutra), the smooth-coated otter (Lutra perspicillata) and the small-clawed otter (Amblonyx cinerous). Just 50 years ago, the smooth coated otter, also referred to as the smooth Indian otter, was widespread in the country while both Eurasian and the small clawed otter (earlier called the clawless otter) were absent from central India, but found in broad bands in the Himalayas and the ghats in the south. It is essentially an otter of cold hill and moutain streams and lakes. Today, these elegant creatures are confined only to protected areas and zoos. If there are any unknown pockets outside, they are unlikely to survive.What happened to otters was quite simple. Found in rivers, lakes and other wetlands, they competed with human beings for fish, their main diet, and lost. Pollution poisoned their food and habitat. Lakes and wetlands were drained for agriculture. In fact the trade of otter skins has been going on for hundreds of years in South East Asia. According to a wildlife trade survey done in Thailand, an otter skin can be sold for $90-$100 to leather factories and considered the best leather to make jackets. It is also believed that otter fat was good for rheumatism, and dried otter penis can fetch up to $50 per inch in Mandalay, and in Myitkyina in the Kachin state. A researcher from the Centre for Ecological Sciences, Bangalore, V. Meena, found nomadic tribal herb collectors from Haryana trapping otters in the Palani hills of Tamil Nadu to sell the oil and skin and of course, eat the flesh, while they were at it.

Otters have long, slim bodies and relatively short limbs, with webbed paws. Most have sharp claws on their feet, and all except the sea otter have long muscular tails.They have a very soft, insulated underfur which is protected by their outer layer of long guard hair. This traps a layer of air, and keeps them dry and warm under water.Many otters live in cold waters and have very high metabolic rates to help keep them warm. In summer, in the Himalayas many otters go up the streams and torrents ascending to altitudes of 12,000 ft or more. Their upward movement probably coincides with the upward migration of carp and other fish for purposes of spawning. With the advent of winter they come down to the lower streams.For most otters, fish is the primary staple of their diet. This is often supplemented by frogs, crayfish and crabs. Some otters are expert at opening shellfish, and others will feed on available small mammals or birds. Prey-dependence leaves otters very vulnerable to prey depletion.Otters are very active, chasing prey in the water or searching the beds of rivers, lakes or the seas. Most species live beside water, entering it mainly to hunt or travel, otherwise spending much of their time on land to avoid their fur becoming waterlogged. The sea otter does live in the sea for most of its life.Otters are playful animals and appear to engage in various behaviors for sheer enjoyment. Different species vary in their social structure, with some being largely solitary, while others live in groups – in a few species these groups may be fairly large.

Range map of Otters (IUCN)

Major Threat(s): The aquatic habitats of otters are extremely vulnerable to man-made changes. Canalisation of rivers, removal of bank side vegetation, dam construction, draining of wetlands, aquaculture activities and associated man-made impacts on aquatic systems are all unfavourable to otter populations (Reuther and Hilton-Taylor 2004). In South and South East Asia, the decrease in prey species from wetlands and water ways had reduced the population to an unsustainable threshold leading to local extinctions. The poaching is one of the main cause of its decline from South and South East Asia, and possibly also from the North Asia. (IUCN Red List)

References: Wikipedia, IUCN Red List, S. H. Prater (the book of Indian Animals), Aniruddha Mookerjee in the Hindu.

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Saturday, September 12, 2009

Vanishing Species: Peregrine Falcon

Sunday article by Mohan Pai
Peregrine Falcon
Falco peregrinus

Nature’s dive-bomber that attains an incredible speed of 324 km per hour in its swoop.
Rocketing down to catch its prey, no other creature on earth can move as fast as the peregrine falcon. A peregrine stooping is not really flying; it’s coming out of the sky like 1 kg feathered rock. These falcons get higher than most before they dive, so they reach higher speeds. Presumably they need the altitude and resulting speed because their prey itself is so fast. Pigeons for example, a staple peregrine food, can have a cruising speed of 50 km/h and bursts of about 100 km/h which is the top speed for a cheetah.

Painting of subspecies babylonicusBy John Gould
The Peregrine Falcon (Falco peregrinus), also known simply as the Peregrine, and historically as the "Duck Hawk" in North America, is a cosmopolitan bird of prey in the family Falconidae. It is a large, crow-sized falcon, with a blue-gray back, barred white underparts, and a black head and "moustache". As is common with bird-eating raptors, the female is much bigger than the male. Experts recognize 17–19 subspecies, which vary in appearance and range; there is disagreement over whether the distinctive Barbary Falcon is a subspecies or a distinct species.
The Peregrine's breeding range includes land regions from the Arctic tundra to the Tropics. It can be found nearly everywhere on Earth, except extreme polar regions, very high mountains, and most tropical rainforests; the only major ice-free landmass from which it is entirely absent is New Zealand. This makes it the world's most widespread bird of prey. Both the English and scientific names of this species mean "wandering falcon", referring to the migratory habits of many northern populations.While its diet consists almost exclusively of medium-sized birds, the Peregrine will occasionally hunt small mammals, small reptiles or even insects. It reaches sexual maturity at one year, and mates for life. It nests in a scrape, normally on cliff edges or, in recent times, on tall human-made structures. The Peregrine Falcon became an endangered species in many areas due to the use of pesticides, especially DDT. Since the ban on DDT from the beginning of the 1970s onwards, the populations recovered, supported by large scale protection of nesting places and releases to the wild.
The Peregrine Falcon has a body length of 34 to 58 centimetres (13–23 in) and a wingspan of around 80 to 120 centimetres (31–47 in). The male and female have similar markings and plumage, but as in many birds of prey the Peregrine Falcon displays marked reverse sexual dimorphism in size, with the female measuring up to 30 percent larger than the male. Males weigh 440–750 g, and the noticeably larger females weigh 910–1500 g.

Peregrine range map

Ecology and behavior
The Peregrine Falcon lives mostly along mountain ranges, river valleys, coastlines, and increasingly in cities. In mild-winter regions, it is usually a permanent resident, and some individuals, especially adult males, will remain on the breeding territory. Only populations that breed in Arctic climes typically migrate great distances during the northern winter.

The life span in the wild is up to 15.5 years. Mortality in the first year is between 59–70%, declining to between 25–32% in adults. Apart from anthropogenic threats like collision with human-made objects, the Peregrine may be killed by large eagles or large owls. The Peregrine Falcon is host to a range of parasites and pathogens. The Peregrine Falcon feeds almost exclusively on medium sized birds such as doves, waterfowl, songbirds, waders and pigeons. Worldwide, it is estimated that between 1,500 and 2,000 bird species (up to roughly a fifth of the world's bird species) are predated by these falconsThe Peregrine Falcon hunts at dawn and dusk, when prey are most active, but in cities also nocturnally, particularly during migration periods when hunting at night may become prevalent. Nocturnal migrants taken by Peregrines include species as diverse as Yellow-billed Cuckoo, Black-necked Grebe, Virginia Rail and Common Quail. It requires open space in order to hunt, and therefore often hunts over open water, marshes, valleys, fields and tundra. It searches for prey either from a high perch or from the air Once prey is spotted, it begins its stoop, folding back the tail and wings, with feet tucked. The air pressure from a 200 mph (320 km/h) dive could possibly damage a bird's lungs, but small bony tubercles in a falcon's nostrils guide the shock waves of the air entering the nostrils (compare intake ramps and inlet cones of jet engines), enabling the bird to breathe more easily while diving by reducing the change in air pressure. To protect their eyes, the falcons use their nictitating membranes (third eyelids) to spread tears and clear debris from their eyes while maintaining vision. Prey is struck and captured in mid-air; the Peregrine Falcon strikes its prey with a clenched foot, stunning or killing it, then turns to catch it in mid-air. The Peregrine will drop it to the ground and eat it there if it is too heavy to carry. Prey is plucked before consumption.
The Peregrine Falcon is sexually mature at the end of the first year of age but in healthy populations they breed after two to three years of age. The pair mates for life and returns to the same nesting spot annually. The courtship flight includes a mix of aerial acrobatics, precise spirals, and steep dives. The male passes prey it has caught to the female in mid-air. To make this possible, the female actually flies upside-down to receive the food from the male's talons. The Peregrine Falcon is territorial during the breeding season; nesting pairs are usually more than 1 km (0.6 miles) apart, and often much farther, even in areas with large numbers of pairs. The distance between nests ensures sufficient food supply for pairs and their chicks. Within a breeding territory, a pair may have several nesting ledges; the number used by a pair can vary from one or two to seven in a 16 year period. The pair defends the chosen nest site against other Peregrines, and often against ravens, herons, gulls and (in ground nest) mammals like foxes, wolverines, bears and wolves. Both nests and (less frequently) adults are predated by larger-bodied raptorial birds like eagles, large owls, or Gyrfalcons. Peregrines defending their nests have managed to kill raptors as large as Golden Eagles and Bald Eagles (which they normally avoid) that have come close to the nest.
The Peregrine Falcon became an endangered species because of the use of pesticides, especially DDT during the 1950s, 60s, and 70s. Pesticide caused to build up in the falcons' fat tissues, reducing the amount of calcium in their eggshells. With thinner shells, fewer falcon eggs survived to hatching. In several parts of the world, such as the eastern USA and Belgium, this species became extinct as a result.

The Peregrine Falcon was used in falconry for more than 3,000 years, beginning with nomads in central Asia. Due to its ability to dive at high speeds, it was highly sought-after and generally used by experienced falconers. Peregrine Falcons are also occasionally used to scare away birds at airports to reduce the risk of bird-plane strikes, improving air-traffic safety, and were used to intercept homing pigeons during World War II.

Falconry in India.
The sport of falconry which spread throughout the world was especially popular with the Indian nobility. Falconry, a sport among kings, princes and nobles started way back in 2000 B.C. in China. It started not as a sport but simply out of a necessity for food. From China it spread to Japan, India, Persia, Arabia, Turkey and finally to Europe. By 700 A.D. falconry was well established as a sport. By the middle of the 18th century there were hawking clubs all over Europe. Many tapestries and paintings all over the world depict battle scenes of kings and nobles with their favourite falcons as falconry was also a form of relaxation during long battles. King Richard, Coeur de Lion, took his hawks with him to the crusades. The kings Frederic and Henry VIII of England and the Emperor Napoleon were all keen followers of this magnificent sport. Among the ladies, Mary Queen of Scots loved to be out hawking and Empress Catherine of Russia had her favourite falcon, Merlin.
The Mughals in India were also keen falconers. The sparrow hawk was the favourite of Emperor Akbar. He often used these remarkable birds for hunting. They also added splendour to his court. For them many mansabdars ( commanders), ahadis (single man) and other soldiers were employed. The birds were fed twice a day and towards the close of each day they were fed on sparrows.Falcons are birds of open country, solitary in habit and prefer to fly freely scouring the countryside with their acute sight and pausing in their majestic flight to stoop down at a hundred miles an hour on their unsuspecting prey. The peregrine falcon, the finest bird for training in India, migrates along the east coast of Bhavnagar in Gujarat on the boarder of the Gulf of Cambay. Other falcons found in Bhavnagar are the desert falcon known as the lugger and goshawk or baz which can be trained very successfully.In Bhavnagar, the royal family continued to cherish the sport of hawking till the 1940s. the late Maharaja, Shri Krishna Kumar Singh’s two brothers, Maharaja Nirmal Kumar Singh and Maharaja Dharam Kumar Singh were very enthusiastic sportsmen. They each had their own trainers and falcons. The falcons were caught off the coast of Bhavnagar or brought from Punjab. After it is caught the falcon is securely bound in a handkerchief and its eyes are sealed. This is done by slipping a needle through the lower edge of the eyelid and putting the thread over the head. Apparently the falcon shows no sign of pain. In this manner the eastern falconers seal the eyes of their hunting birds. This keeps them quiet for the rest of the training days and prevents them from becoming excited and scared. The bird also gets used to the human voice and touch. Buying a hawk is like buying a horse. The colour phases, marking, shape, size of beak and middle toe, spirit, age and weight are a few points worth considering. Indian falconers would never buy a falcon whose eyes were not sealed. Sealed eyes were an indication that the hawks had not been trained. The new hawk never leaves the gloved hand of its trainer for four to five days. Day and night they are handled carefully by speaking to them softly and stroking them gently and constantly for only then can these wild birds be trained.

As soon as the hawks lose their fear and become docile, their eyes are unsealed and the training days begin. The trainer swings a lure at the end of a short stick and the falcon stoops but the bait is jerked away before the bird can strike. After 40 to 50 attempts the falcon is permitted to strike and bring the lure down to the ground. It is indeed a wonderful sight to see these hawks starting to respond to their trainers. After this lesson the birds are hooded and well fed. Before a contest or a hunt the birds are given secret Indian drugs to stimulate them to have the utmost powers of speed, courage and endurance. Falcons, being good hunters with keen eyesight, can bring down big birds like ibis, cranes, big heron and among animals, hares. When the game rises, the falconer throws the hawk to catch its prey just like an athlete hurls a goal forward. But vigorous training is absolutely necessary to teach the little fighters how to chase such a quarry. In game hunting, pointers and setters are used and not until the game is found the falcon is unhooded.
In India falcons and hawks constitute two thirds of all species of birds or prey. The uncommon goshawks and the perennial favourite, the peregrine span the Indian sub-continent.However, the sport of falconry has been fast losing popularity not only due to the expenses involved but also due to wide criticism and an increasing awareness of preserving nature and wildlife. There has been a dwindling of the species. In fact the king of falcons, the bullet-headed, steel grey peregrine became almost extinct due to excess DDT in the environment causing the bird to lay eggs with fragile shells leading to greater pre-hatch mortality. However, people were quick to champion this much loved bird and save it from imminent peril.

Peregrine in philately

References: Wikipedia, Falcon & Falconry

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