Tag Archives: Animals

Can snakes swim? If yes, how do they swim?

Most of the animal species are born with the ability to swim, so are the snakes. All species of snake can swim, no matter the type of water. The prime reason you don’t see all snakes in your local pond but in your garden is that many species prefer land to water. Most of the snakes like to live in the dry land while some species spend their entire lives in water. It is the latter category that we usually call water snakes.
The snakes use different kinds of terrestrial locomotive techniques. At least five of the techniques have been identified, lateral undulation being the one most often used among them. All kinds of snakes swim in almost an identical way and it is highly similar to lateral undulation. This is the same mode they employ to move along a smooth surface as well. The snakes primarily use the surface tension of the water to glide along. They curve their bodies in a certain way while traveling through the water. They would swerve to one side first and then the other, and would repeat that motion. It is like they are drawing a big ‘S’ with their body continuously in the water. These undulations start at the head and continue down the length of the body. Just like the cars of a train follow the engine; their bodies would follow the movement of the head of the snakes. Each time they turn, they put force on the water behind them, and the resulting opposite momentum pushes them forward. The tail in particular serves to provide the momentum forward.
Since the water does not provide a solid platform like land, the swimming is more difficult for snakes. However, most species are adept in it. The water residents have acquired a more flattened structure through evolution to aid their movements. Some species have paddle-like tails and nostrils placed on backside to aid the movement.
Some species are better swimmers than others. Some water dwelling species can travel even for miles without stopping. There are also some differences in the swimming style of various kinds of snakes. For example, the venomous cottonmouth snakes, inhabiting the coastal plains of America, often hold their head a little above the water surface while moving. This is identified as a defensive mechanism, to sense the approach of other predators. But many other water snakes glide under the water, their head in level with rest of their body. The slightly differing swimming styles often help to identify the venomous from harmless ones.

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Is it true that Candiru fish can swim upstream into your urethra?

If you have ever heard of the Amazon River and rainforests, you would have heard about the Candiru fish as well. Like Piranha, this tiny little catfish is also a villain of many fearsome stories and a subject of dread among many people.
Also known as the pencil fish, the toothpick fish and the vampire fish, Candiru is a freshwater parasitic catfish found in the Amazon basin. It is a small species, which can only grow to 40 cm at most. However, the fish has developed notoriety, thanks to various stories claiming of it jumping to the people’s urethra.
The Candiru fish feeds on blood of the fish hosts. It attacks the gill opening and attaches itself to a blood vessel and slashes it. It feed on the blood coming out from the wound. It leaves the host after a few minutes of feeding.
The earliest account of Candiru attacking a human was made by German biologist Carl Friedrich Philipp von Martius in 1829. In his report, Maritus told that the native people of the area would go into river with a protective cover around their genitals to prevent Candiru attack. Later many stories of the Candiru attack emerged, but most of them went unverified. In a number of cases, Candiru entered the vaginal canal, not the supposed urethra.
So far, there is only one documented incident of a Candiru entering a human urethra. The incident took place in 1997 at Itacoatiara, Brazil when a 23-year-old man reported that a Candiru jumped from the water into his urethra while he was urinating in a river. The man underwent a urological surgery by Dr. Anoar Samad to remove the fish from his body immediately. But there were many discrepancies in the story, as emerged in the observations of American marine biologist and Candiru expert Dr. Stephen Spotte.
There are a lot of factors that prove the stories surrounding Candiru to be just myths. The early doctors had speculated that the fish was attracted to urine because of the presence of urea. But experimental studies proved that it was a false assumption. The fish hunted by sight not smell. Another major myth was that it can swim directly up a stream of human urine. But according to the laws of fluid dynamics, this is impossible. The small fish can’t withstand both the gravity and the force of falling urine. And the act of entering the urethra is suicidal for the fish as well. With no oxygen or space, it won’t survive even a minute.
The Candiru fish is just another victim of the loose tongues and twisted minds. It is not attracted to human urine and neither has the tendency to enter the human urethra. The myth emerged from many false accounts of people over the years. Even the chance of the fish to attack when a person is urinating while submerged in a stream inhabited by Candiru is, just like Dr. Spotte stated, about the same as being struck by lightning while simultaneously being eaten by a shark.

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What is hibernation? And how is it different from aestivation?

The word ‘hibernation’ originated from the Latin word ‘hibernus’ which means ‘of winter’. Hibernation is the process that certain animals and birds retreat from their surroundings and lie dormant in a very deep sleep for a prolonged period of time, during the cold winter season. While in this phase, the hibernating animals reduce their body functions to a minimum and their body temperature and heartbeats drop to a very low level. They store barely enough food that can help them survive the period and their growth process is almost nonexistent during this phase.
Hibernating animals are found in all classes of organisms, from insects to mammals. Rabbits, rodents, raccoons, skunks, squirrels and bats are some of the popular hibernators. Some mammals, like polar bear, even hibernate during gestation period. The young ones are born during or after the hibernation.
Hibernation is an enigma that has been puzzling the zoologists for a long time. The experts consider it to be a way of nature helping the creatures pass the cold months of winter during which the food supplies are very meager. The animals, before their long slumber, eat a large quantity of food to store up energy in their bodies. Some of the animals even eat such an amount that their body weight almost doubles. During the hibernation, certain animals may wake up periodically for a very brief time, only to eat and get rid of waste; and they go back to sleep instantly. They have to be very careful to limit their movements, so as to reduce the energy loss. The hibernators are classified into two types: Obligate and Facultative. The former are traditional hibernators while the latter ones only hibernate due to lack of food and unbearable cold.
The retreat of a hibernating animal is called a hibernacula. They find the perfect place often after a long period of search. They have to make sure the place is both warm and comfortable and safe from the predators. It takes from twelve hours to a day for the animals to enter hibernation. Their bodily functions gradually reduce during this period. From this point they are very much incapable of protecting themselves. This is one of the disadvantages of the hibernation and underscores the need of a protected retreat.
Even though hibernation is normally associated with winter, some animals also spend the hot summer months in a state equivalent to hibernation. This process is known as Aestivation. It is most common among the animals living in deserts. Lizards, garden snail and lungfish are examples of aestivating creatures. Then there are organisms like earthworms, who are both hibernators and aestivators.
Hibernation has been one of the major wonders in the animal world and continues to be so. The scientists call it sometimes ‘time migration’ because of the organisms’ escape from the natural biological clock.
Additional reading:
Hibernation (Wikipedia)
Aestivation (Wikipedia)


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Why do dogs run behind cars and bikes?

Dogs, like many predators, instinctually run after things that are moving away from them. This instinct is developed in them through evolution because in the past a dog’s food was anything that ran away from it. It is partly about hunting and partly about defending their territory. All dogs possess to some extent an instinct to chase large rapidly moving objects. Some breeds of dogs are more likely than others to chase after cars because their chase instincts are so modified over time. For example, working breeds like retrievers have their hunting instincts diverted into fetching game for human hunters. Shepherds, bred for generations to herd cattle, are particularly prone to car-chasing as the large, swiftly moving cars generically resemble the creatures they were bred to chase.
It is advisable to not run when a dog barks at you. It would bark for some time and then lose interest and walk away.

How fast can a cheetah run? Can runners like Usain Bolt and David Rudisha beat cheetah on a racetrack?

On August 3, 2012 a female cheetah set a new record of covering the distance of 100 meters in just 5.95 seconds. This record is far greater than the record time of 9.58 seconds set by the Jamaican sprinter and Olympic record holder Usain Bolt — the fastest man on Earth. There are 3 prime reasons that enable the cheetah to run at such great speed. 1) The cheetah is bestowed with long legs by Nature. 2) Its body is connected to the legs with highly flexible muscles, and 3) The long and flexible spine of the cheetah acts as a spring and helps it to bounce with full energy, thus enabling it to cover a distance of nearly 6.7 meters (22 feet) with every leap.
Cheetah Vs. Usain Bolt
Now if this super fast animal is made to compete with the Olympic gold medalist sprinters, who will win the race? This depends on the type of the race. If it is 100 meters and 400 meters sprint, the cheetah can easily defeat even the champions like Usain Bolt. To cover 400 meters, the cheetah will take only 16 seconds, while in the case of human beings the record of covering the distance of 400 meters is 43.18 seconds. This record was set by an American sprinter named Michael Johnson in 1999. Assuming that the cheetah moves ahead with the same speed, it would cover the distance of 800 meters in 32 seconds. On the other hand, for the humans, this record has been set at 1 minute and 41.01 seconds by the Kenyan runner David Rudisha in the year 2010.
Is there any chance for a runner like David Rudisha to beat the cheetah on a racetrack? Yes, there is! If an 800 meters race is held, David Rudisha can easily outperform the cheetah. Here’s the reason: The cheetah’s normal body temperature remains at 102 degrees Fahrenheit. (The normal temperature for a human body is 98.6 degrees Fahrenheit.) Based on a research, it is observed that once the cheetah gains momentum beyond the speed of 16 kilometer per hour, its body cannot release excess heat. The grueling task performed by the cheetah leads to storage of 90% of heat produced within its body, thus increasing its body temperature to a great extent. The situation is similar to the motor car engine gets overheated due to malfunction of the cooling system.
If the cheetah continues its run even after its body being overheated, the accrued heat affects the brain and leads the cheetah to become unconscious. Beyond this stage the cheetah can run at the most for another 550 meters after which it is physiologically compelled to take a break and rest for 15-20 minutes. The attempt to relax and exhale helps the cheetah to calm down till its body temperature is restored to normal. Meanwhile, a runner like David Rudisha would run to the finishing line defeating the fastest animal on the Earth. It is due to this physiological characteristic that the cheetah moves towards its prey as slowly and silently as possible so that it does not have to run for a long distance later to chase it.
In spite of this, the African Impala and Gazelle antelopes successfully dodge the cheetah’s chase by running in a zigzag pattern. If the cheetah can pounce on its prey within a sprint of 500 meters, it gets to feast on it or else it has to stay hungry.

Additional reading:
Cheetah (Wikipedia)
David Rudisha (Wikipedia)
Usain Bolt (Wikipedia)

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How is noise pollution killing whales?

There are many reasons behind whales meeting their death on the shores. Sometimes they lose their way and move towards the beach. Some whales, swimming too close to the shores, are beached when there’s steep decline in water level during low tide. Whale is endowed with a natural compass in its head. This compass, which works on the basis of Earth’s magnetic field, helps it to navigate through the sea. Unfortunately for the whales, the magnetic field is not the same everywhere. It is greater near the poles and weaker near the equator. It affects the whales’ built in compass which does not work perfectly in areas where the magnetic field is weak. Many a times the whale unknowingly approaches the sea shore due to navigation error and if it is stranded on the land, there is no chance for its survival. Its body collapses under its own weight and soon it dies of dehydration.
Beached whales
While the whale navigates using its natural compass, it finds its way under the water using its natural sonar. The whale emits high-pitched sound waves in the water. These waves bounce back from the sea-bed (or predator) and upon receiving them the whale decodes its route. This way of finding the directions is known as echolocation; and it works perfectly when the sea is calm.
Unfortunately, seas around the world are not as peaceful as they used to be a few decades ago. There has been a great increase in the level of noise pollution in the seas and oceans across the globe due to industrialization. Drilling of deep sea oil wells creates a deafening sound under the water. Propellers of giant military as well as cargo ships, submarines, oil tankers etc. produce jarring sounds. Military submarines’ and ships’ sonar equipments transmit low-frequency sound to locate the enemy ship or submarine. This sound is not less than 230 decibels — nearly twice the sound produced by jet engine of a combat aircraft.
All these factors add to the ever increasing levels of noise pollution in the sea. The natural sound waves emitted by the whale in order to map its route through the water therefore get scattered. The whale cannot receive them back. It loses its course due to lack of mapping, and sometimes swims towards the shallow shores — only to meet a painful death. While about 360 whales died due to beaching in 1994, the figure rose to 782 in 2004, and 2,000 in the year 2010. This clearly indicates the increase of noise pollution by humans in the ocean water. This also indicates to what extent human interference with environment can cause damage to the ecology.

Additional reading:
Beached whale (Wikipedia)

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Why are some animals and birds albino (without color)? And why albinos are few in number?

Sometimes an offspring can have a trait which is unlike the traits of both parents. The information about traits is in the form of DNA in genes, one of which may completely hide the effect of another gene and thereby become a dominant gene. A gene whose effect is eclipsed by a dominant one is known as a recessive gene.
Albino peacock
The rule of heredity mandates that whenever a dominant and a recessive gene pair together, the dominant gene controls the trait. In rare cases, however, a recessive gene overshadows the dominant one and causes an offspring to have traits that neither parent has. Every so often, the new trait results from a mutation, i.e. change in the DNA contained in gene. (DNA is just four basic chemicals or bases–A, C, T and G–strung together like steps on a spiral staircase). The change occurs when DNA makes copy of itself, wherein the whole or small section of the DNA is rearranged. As a result, a different DNA message is passed along to the offspring.
One example of mutation is albinism, a condition in which a bird, animal or a human being is unable to make a substance called melanin. It is this pigment which in different concentrations gives coloration to the eyes, skin, hair, and feathers. Lacking melanin, albino organisms are usually colorless and appear snow-white. In the wild, albino birds and animals can not stay as safe as other members of their species. Normal birds and animals, using a combination of various colors, provide themselves which elaborate and highly effective disguise. They have evolved an uncanny likeness to elements of their environment such as leaves, rocks, grass and pebbles to avoid being noticed by predators. Albino types are easily noticed, and so cannot hold out for long. On the other hand, an albino predator (such as snake) is easily noticed by its prey, which makes a hasty and timely retreat. A snow-white peacock, shown above, has its own problem. It cannot attract a female, due to absence of the bright purple, blue and green feathers. This explains why albinos are few in number. In evolution, their condition stands to their disadvantage in many ways.

Additional reading:
Albinism (Wikipedia)

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How do cats see in the dark?

The truth is, cats do not see in the dark. They can only see in partial darkness. If a cat were to be placed in a totally dark room, it would see no better than you would. However, out in the open, even at night, is it seldom totally dark. The Moon, street-lamps, or lights from houses all help to provide some illumination at night. In poor light conditions, the cat’s eye is able to multiply the effect of the light by means of special layer of cells at the back of the retina. It is this layer, shining with a green glow, that we sometimes see if we shine a light on a cat’s eyes in the dark.

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Why do frogs go into hibernation in winter?

Frog is a cold blooded amphibian the temperature of whose body always remains equal to the atmospheric temperature. It can neither tolerate the extreme heat of summer nor the biting cold of winter and so the frog goes into hibernation whenever there are such extremes of climate. Before hibernating, the frog goes underground, as there is no safety of his life in the open on Earth. As it is, it does not get enough food in the form of insects in dry weather. It is also impossible to carry forward its lineage silence its spawn that is in the form of jelly immediately starts drying up and withering in dry weather.
Frog ready to hibernate
Thus, the survival of frogs is mostly dependent on monsoon. When the monsoon starts receding and the puddles start drying up, a frog would push itself into the marsh with its hind legs. (See photo above.) Once they reach a depth of about 30 to 35 centimeters, they stop and then make a hollow twice the size of their bodies by pressing the surrounding soft but solid mud. After adopting a comfortable position, the frog puts its respiration to low gear. It reduces its heartbeats gradually. After some time its heart and lungs function only as much as is necessary for its survival. The frog slowly slips into the stage of deep sleep known as hibernation. The biological functions of its body slow down completely and so the frog has no need for nutrition. The fat stored in its body is enough for its survival. It does not even need water, since just two weeks before entering into hibernation its skin automatically becomes loose and covers it (leaving only its nostrils free for breathing) up like polyethylene and this covering stops the moisture of its body from evaporating into the atmosphere. Since it does not have to replace lost moisture it has no need for water.
Months pass in hibernation. When the first rains of monsoon hits the ground, the frog breaks its long sleep. The heartbeats become normal once again. The frog then breaks open the covering and comes out onto the Earth and first of all breaks its months-long fast by ingesting a lot of insects.

Additional reading:
Hibernation (Wikipedia)

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How do dolphins sleep without drowning? Is it true that they sleep with one eye open?

Dolphins, being air-breathing mammals, have to resurface every now and then to breathe fresh air. So, one wonders when and how they manage to get sleep.
Dolphins are a small group of whales and like other whales they have lungs instead of gills. They breathe through a single nostril called the blowhole located on top of the head. The blowhole is opened during their frequent trips to the surface to expel and inhale air.

Even though respiration has to continue with not more than few minutes’ respite between breaths, dolphins sleep an average of eight hours a day, but only allow one half of their brain to doze off at a time. They can not ‘switch off’ both hemispheres of their brain and have deep sleep underwater, or they would drown. So sophisticated is the dolphin’s sleep system that it naps at the surface of the water, with half of its brain alert and the opposite eye open, while the other half of the brain is asleep with the opposite eye closed. (See photo above.) During sleep, the dolphin alternates position to allow each half of the brain to get its turn. In effect, the dolphin is awake and asleep at the simultaneously.

Additional reading:
Dolphin (Wikipedia)

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