Monday, August 18, 2008

Secretary Bird

 This large, tall and unusual bird of prey is endemic to Africa and inhabits the grasslands (savannah, steppes and the bushvelds), lying to the south of the Sahara Desert.  Some fossil evidences suggest that it may have inhabited Middle East and southern Europe.  It belongs to the order falconiformes which includes the raptors likes kites, vultures, hawks, falcons etc., but is classified as a separate family because of it is distinctiveness.  In fact the secretary bird is the only member of the Sagittariidae family.


The secretary bird has a brightly coloured face that sports a crest of long feathers.  From a distance, the crest resembles a quill of pens that the 19th century clerks stuck to their wigs.  For long, this allusion was thought to be the reason behind the unique name given to the bird, which was discovered by the Europeans in the 19the century.

However, a recent hypothesis states that the name might have evolved from saqr-et-tair, an Arabic term meaning “hunter bird’, whose French equivalent would be secretaire and hence the name Secretary bird.  Also, The scientific name Sagittarius serpentarius can be taken to mean 'The Archer of Snakes' with Sagittarius referring to the archer (greek mythology) and the bird’s quills referring to a quiver of arrows.


It has a eagle like body, a hooked bill but rounded wings and crane like legs, making it stand tall at about 4 feet tall but weighing only about 3-3.5 kg.  The wingspan is about 2m or 6.6 ft. The legs are long and capable of delivering a powerful punch but has its limitations when it comes to grabbing or grasping. The tail has two elongated central feathers that extend beyond the feet, that are useful in deceiving a snake while hunting. All these physical features are actually adaptations to its environment for plain survival and better preying.  Though an accomplished and a graceful flier, it remains largely terrestrial, spending most of its day on the ground and is rarely seen flying.  It roosts on top of the acacia trees but shortly after dawn they drop to ground and spend their day walking across the grasslands (20kms or above in a day), occasionally resting in the shade to escape the brunt of summer.  They are largely silent except for a rare, hoarse, croaking sound they make while displaying. 


Its diet consists of insects, lizards, rats, small mammals and amphibians, though they are known to eat virtually anything that they can swallow.  In addition to these, it preys on snakes also and is in fact, renowned for its ability to catch snakes.  Perhaps the most distinguishing element of the secretary bird as compared to other birds of prey is its hunting technique.  The prey is generally chased on the ground and once it is caught, repeatedly thumped on the head until it becomes unconscious.  Once unconscious the prey is swallowed.  To avoid being bitten by a snake or even if bitten to avoid being poisoned, the secretary bird does something remarkable with the aid of its wings.  The bird will stand slightly back, spread both wings, and erect the crest of feathers at the back of the head and fire away with both talons. Two very long tail feathers will also drop down. The spread wings and feathers act as a false target for venomous creatures, particularly snakes. The two tail feathers are designed to look like a third leg. Because feathers have hollow quills, the bird will not be poisoned if it is bitten in the feathers.

The social structure of the secretary bird is also unique.  The birds are monogamous and have the same partner for its lifetime though members of a pair are usually not together, but instead stay a small distance apart.  The young ones, hatched after an incubation of 45 days, stay with the parents in the nest for two to three months after which they have to fend for themselves.  The pair is extremely faithful to the nest and feed the young ones with partially digested liquid food regurgitated by either of the parents.

The unique or unusual traits and features associated with the secretary bird can be attributed to the unique environment and its evolution to negotiate it.  The Seriemas of the South America is a bird, which is not related to the secretary bird but has similar size and shape owing to the evolution under similar circumstances.


The major threat for the bird is the loss of habitat and from deforestation. The Africa Convention on the Conservation of Nature and Natural Resources declared the Secretary bird as protected species in 1968.

Scientific Classification:

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Falconiformes

Family: Sagittariidae

Genus: Sagittarius

Species: serpentarius



Wednesday, June 11, 2008

Master of Disguise - The Mimic Octopus

In a bid to ensure survival in the competitive world, animals have evolved some complex defence mechanisms to avoid predation. It is the outcome of millions of years of evolution and amazing to say the least. Camouflage and disguise are two important means by which the animals manage to avoid detection by the predator. Be it the leaf fish of the Amazon, which is preyed by the piranha or a green coloured tree snake, they have developed external traits to blend with the external environment to deceive their predators. But the most spectacular candidate in this list is an inhabitant of the Indonesian waters called the Thaumoctopus mimicus or more popularly known as “the master of disguise” - mimic octopus, that has the astounding ability to mimic some of the other marine life forms.



Up until a decade ago the existence of such a species was not officially recognized. It was only in 1998 scientists spotted this exotic species and therefore it can be presumed that even if they have been spotted earlier, they were mistaken for other animals, which it might have mimicked. The mimic octopus is found distributed in the indo pacific waters in the nutrient rich estuarine bays off the coast of the Malaysia and Indonesia. Habitation in other parts of the world cannot be entirely ruled out and only further research will throw some light. The feeding habits are like any other octopus and it feeds mainly on crustaceans and other small fishes.


An octopus is generally considered to be an intelligent animal and many types of octopus can change their skin colour or texture to imitate the environment (say resemble a rock) but what makes the mimic octopus special and fascinating is the fact that don’t simply change colours but in fact impersonate other animals, the external appearance and behaviour. They accomplish this with the aid of specialized skin cells that can change the apparent color, opacity, and reflectiveness of the epidermis. Chromatophores contain yellow, orange, red, brown, or black pigments; most species have three of these colors, while some have two or four. Other color-changing cells are reflective iridophores, and leucophores. This combined with their flexible bodies explains their ability to mimic. The mimic octopus has been reported mimic other fishes like the lionfish, flat fish, and even jelly fish, sea snakes, stingrays, sea anemones and shrimps amongst others. It is believed to have the ability to imitate atleast 15 marine life forms. Perhaps what has is most baffling is their ability to discern which animal to be mimicked to ward off the possible predator it is facing. For example, reports suggest that they mimic a sea snake when attacked by a damselfish because the sea snake is the natural predator of the damselfish. Similar reports state that the mimic octopuses have been found mimicking a stingray or a flat fish when it perceives a threat from a possible predator. There are also reports of it playing dead when it perceives a threat.



Recent studies throw more light on to how the previous sightings could have well been mistaken to be other species of octopus itself or other life forms that they mimic. In one instance scientists assumed that they are seeing a fight between two different species of octopuses but eventually figured out that both are of the same species and are performing courtship gestures by changing the skin colour. After all they can be more common than they are thought to be. Very little information is available with regard to the lifestyle and activities of the mimic octopus. Though they are known to survive in captivity the behaviour pattern observed in a controlled circumstance may not necessarily be the same as seen in wild. Some reports suggest them to be nocturnal while some others indicate a crepuscular behaviour (active during dusk and dawn) whereas studies on the captive ones indicate that they are active throughout the day. Their life span in captivity, however, has been reported to be very less spanning only months or even days with the highest reported life span being less than a year. It is feared that commercial trade and pet trade could seriously harm the population of the mimic octopus in the wild because of their sheer rarity of occurrence and the lack of scientific data as compared to other pets.


I personally rate this to have the most successful camouflage because they have managed to escape the eyes of the most dangerous predator in the earth for several million years. Need I name the predator?

Some trivia

Octopuses have 3 hearts.

Their blood is blue.

Highly flexible bodies so much so that they can fit into a cool drink bottle.

It is believed that under stress it may eat its own limbs however researchers feel it might be a viral disease.

They are deaf.

Scientific Classification

Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Family: Octopodidae
Subfamily: Octopodinae
Genus: Thaumoctopus
Species: T. mimicus

Tuesday, June 3, 2008

Irukandji

Ben Southall, Tourism Queensland’s Islands Caretaker, held to be the best job in world was stung by an Irukandji Jelly fish while we was in his final few days on Hamilton Island during a Christmas jetski session with some friends. More here
http://www.islandreefjob.com.au/2009/12/29/ouch-a-little-incident-on-the-beach/

The designs of nature still continue to awe and inspire us and many a times, the most unassuming creatures have the most unusual characteristics. Irukandji jellyfishes are some of the smallest but the most venomous creatures in earth and are known to cause the irukandji syndrome. The body of a jellyfish is normally divided into the bell (the body) and the tentacles (arm like extensions used for locomotion, feeding etc). The bell of a mature irukandji measures about 2cm in diameter (the size of a thumbnail) and has 4 long tentacles measuring about 5cm. Unlike other types of jellyfish that have stings only in the tentacles, the irukandji can sting from any part of its body.

irukandji swimming - james cook university video

video

Carukia barnesi, is named after Dr. Jack Barnes who went in search of the organism responsible for causing the ‘Irukandji syndrome’, to treat one of his patients suffering from it. Eventually he himself suffered a sting and ended up in the hospital, along with his son and a 'life-saver' and in recognition of his dedication, it was named after him. The irukandji are found along the Australian coast and sightings have been reported in the waters of New Zealand and Indonesia. The other type of jellyfish known to cause this syndrome is called Malo kingi that is named after Robert King who succumbed to the sting. Though the syndrome can be caused by other jellyfishes too, so far only these two have been identified on record.

The term Irukandji refers to an Australian Aboriginal tribe that inhabited the Palm Cove region of northern Queensland where the Irukandji syndrome, produced by the irukandji stings poison, occurs most often.

Perhaps, the most compelling feature associated with the irukandji is its potent venom. Taking into account its miniature size, the venom it might be able to produce should be a trivial quantity and that ultra small amount might prove to be fatal even to the most dangerous predators on earth, we humans. A variety of symptoms ranging from nausea, vomiting, high blood pressure to cardiac arrest at times and even fatal brain haemorrhage, have been associated with the irukandji syndrome caused by an accidental sting (accidental, because hunting it has not begun yet). Ironically, a simple brush of one of the tentacles or any part of the irukandji, on uncovered skin of a human being, is enough to inject the venom and trigger the syndrome, which if left untreated has proved fatal. It is still not very clear as to why the irukandji, in spite of being small in size, has evolved such potent venom in its armoury given the facts that those lying above and below it in the food chain might not be huge animals. Some biologists suggest that it may have developed the weapon to stun the prey, which should be ideally small fish, in an instant and then consume it. As with any venomous creature, it would be an interesting proposition to study how the irukandji are not affected by its own venom while consuming the prey.

Treatment for the irukandji syndrome is available these days though there is no specific or definitive antidote or anti venom available. Medical practitioners claim success with magnesium but generally the consensus is that, if noticed on time, the individual symptoms can be treated with a combination of drugs. Research and development of antivenom is being undertaken by various agencies and irukandji have been reared successfuly in captivity too.

Not much is known about the life cycle or the venom mechanism of the irukandji owing to their small size and their extreme fragility. At times they are so fragile that a hit against the wall of the aquarium is enough impact to kill them.The global warming and the associated climatic changes are having their impact on the population and distribution of the irukandji. Some latest studies reveal as a result of global warming, there might be a population explosion of irukandji and the fast depleting food resources due to the destruction of corals may result in the irukandji invading newer areas. If the worst has to happen and the irukandji invades the beaches, most beaches along the pacific coast would become unfit for human recreation, at least in the current circumstances with no proven cure.