Wednesday, August 31, 2011

The Gigantic Gaur

Though not as large as some domesticated cattle, gaur are the largest wild cattle on earth. In fact, the only land animals that regularly grow heavier than gaur are elephants, rhinos and hippos. The largest male gaur can be ten feet long, stand over six feet tall at the shoulders and weigh well over 4,000lbs!
Gaur are mostly dark brown in color with older bulls appearing nearly black. Males can be identified by the large dorsal ridge on their backs which can extend several inches higher than the rump. Both sexes feature horns that can be over two feet long connected on the head by a grey ridge of fur.

Once common throughout most of southern Asia, gaur populations have seriously declined and fragmented over the last fifty years. Overhunting, poaching and destruction of habitat are the main causes of this, leading to these animals currently being classified as vulnerable and nearly endangered. Their current ranges included portions of India, Vietnam, Cambodia, Laos, China, Thailand, Bhutan and Nepal.

Gaur are not known to be particularly aggressive animals and rarely fight even amongst themselves. Fully grown males are far too large for any natural predator except for tigers, and have even been known to kill tigers in self defense. However, herds near human populations can be short tempered towards both humans and livestock animals.

Tuesday, August 30, 2011

The Subway Dogs of Moscow

Like any large city, Moscow is home to a lot of stray animals. Amongst a population of over eleven million humans exists an estimated 35,000 stray dogs; and some have adapted especially well to life in the urban jungle.
Just as their wolf ancestors learned the best hunting routes over time, some Moscow strays have learned to use the city’s massive subway system to commute to the urban core where the best food begging opportunities exist.
Strays in Moscow have traditionally lived in large industrial complexes that provide plenty of shelter with little human disturbance. When Russian capitalists elected to move these industrial areas from the city’s center to its outskirts to make room for restaurants and other private businesses in the 1990’s, the dogs moved along with them.

However, this created a problem as the dogs were now required to live many miles from the best food sources. The smartest strays solved this quandary by learning to use the subway to commute to the city each day, allowing them to live where they want without giving up begging opportunities.
Not only are these dogs tolerated by commuters, they are actually celebrated by some. They are not aggressive and usually allow people to pet them or sit next to them. After all, being polite is the first step to getting a handout. These dogs are so beloved by some that there is even a subway dog statue honoring them.
Once the dogs have reached the appropriate stop, they’ll exit the train and go to work searching for a meal in the streets above. They do this by either scaring people into dropping their food by sneaking up behind an unwary target and barking, or by simply acting so cute and nonthreatening that it’s irresistible to offer them a bite.
At the end of a hard day the subway dogs will descend the stairs, find the right train and get in a nice nap for the ride back home.

Images via English Russia.

Monday, August 29, 2011

Farewell, Happy Feet!

This past June a three foot tall emperor penguin captured the attention of much of the world when he was discovered on a beach on the north island of New Zealand. Native to Antarctica, this was the first sighting of an emperor penguin in New Zealand in 44 years.
Wildlife officials had originally planned to leave the young penguin alone in the hopes that his natural instincts would guide him back home. However, intervention was deemed necessary after the confused bird ingested over 7 pounds of beach sand and sticks, likely mistaking it for the snow he would usually eat to stay hydrated.

After being transported to the Wellington Zoo, the penguin, affectionately named Happy Feet, underwent three medical procedures to remove debris from his stomach and had since been living in a special temporary habitat while he regained weight and strength.
Today, Happy Feet is finally headed home as a passenger aboard the New Zealand oceanic research ship Tangaroa. An iced-down compartment and a diet of fish will keep him comfortable on the four day journey back to his native range. He will be released into the water by using a special slide or inflatable boat depending on his mood and the weather.
Fans of Happy Feet shouldered much of the cost of the penguin’s two month stay, donating over $28,000 to cover care and feeding costs. Happy Feet is currently wearing a GPS tracking device to allow scientists to keep tabs on his progress. As emperor penguins can live for up to 50 years, we are all wishing Happy Feet a long and happy life back home.

Friday, August 26, 2011

The Arctic Tern - Frequent Flyer

Arctic terns may be considered seabirds, but they don’t spend very much time on the ground. In a single year an arctic tern may fly over 44,000 miles, an amazing but necessary feat for a bird that spends its summers and winters on opposite ends of the earth. Arctic terns may fly over 1.5 million miles in their 20+ year lifetimes.
During the northern summer arctic terns can be found throughout coastal regions of northern Europe, Asia and North America nesting. Once the northern winter draws near, the terns will set out for their southern home in Antarctica. Because they fly with prevailing winds, the journey south may be up to 14,000 miles long. Whereas terns will stay on coastal land during the northern summer, they spend their time in Antarctica on and around pack ice during the rare times they’re not in the air.

Arctic terns are primarily carnivores and feed most often on small varieties of fish such as herring and cod, usually diving down to the surface to snatch the fish out of the water. In addition, they will also feed on crustaceans, berries and insects during the northern summer.

Once they have reached their third or fourth year of life arctic terns will begin breeding; pairs will usually mate for life. Chicks are born after about a month of incubation and must quickly learn to fly and hunt before making the long trek south for the winter. It is likely that all birds in the family will return to the same nesting site for the rest of their lives.

Thursday, August 25, 2011

Backyard Nature - The Copperhead Snake

The most common venomous snake in the eastern half of the United States is known by many names. Depending on the region you’re in you may hear it referred to as the highland moccasin, the death adder, chunk head, pilot snake or red snake; but most often it is called the copperhead, and it may live in your backyard.
Copperheads are a species of pit viper and are related to North American rattlesnakes and moccasins. Growing to a maximum length of about three feet, copperheads are amongst the smallest North American vipers. Coloration varies from brown to pinkish tan in color with 10-18 distinct crossbands that are light tan to pale brown in the center and darker towards the edges. They do not have rattles on their tails like many other pit vipers.

Copperheads can usually be found in forested areas and are particularly common near rock outcroppings and ledges in mixed woodlands. Though primarily nocturnal during hot weather, copperheads are active during the day whenever the weather cools. During the winter months they can be found in dens often under ledges. These dens are sometimes shared with other species of snakes, even larger vipers such as timber rattlesnakes.

Most venomous snakes strongly prefer to avoid confrontations with animals that are too large for them to eat. Their venom is a precious commodity and they prefer not to waste it on anything that won’t become a meal. If threatened, a pit viper’s first reaction is usually to flee. If this is not possible, most vipers attempt to make their presence known to the intruder through either an audio display (a rattlesnake shaking its rattles) or a visual display (a cottonmouth opening its jaw to show its fangs). These actions are usually enough to convince a hiker (or deer) to choose another route.
However, the copperhead isn’t like most other vipers. Instead of making its presence known to an intruder, a copperhead that is unable to flee will usually stay motionless, using its camouflaged coloring to make itself nearly impossible to see on the forest floor. This often leads to hikers unknowingly stepping on the snake and provoking it to bite.

As common as copperhead bites are, they are usually not life-threatening. Many self-defense bites are “dry bites” in which little or no venom is injected. Even if the bite is venomous, the copperhead’s venom is considerably weaker than that of most vipers, and use of an antivenin is usually not required. However, fatalities can occur and immediate medical attention should be sought for any copperhead bite. 

Tuesday, August 23, 2011

Siberian Tigers - The World's Biggest Cats

Though most people probably picture a wild tiger living in a warm climate, the largest of cats, the Siberian tiger, actually lives somewhere much colder.
The Siberian tiger is almost identical to the now-extinct Caspian tiger that was present across most of central Asia until recently. Caspian tigers were hunted aggressively during the nineteenth and twentieth centuries throughout Russia and China as forests were converted to farmland. The last confirmed Caspian tiger sightings occurred in the 1950’s, though unconfirmed reports still occur in the Middle East.

The current Siberian tiger can only be found in the birch forests of eastern Siberia, far northeastern China and North Korea. The wild population is estimated to be around 500 individuals. It is thought that they continue to exist in these areas because of the low human population density. 

At nearly four feet tall at the shoulders and weighing nearly 700lbs, Siberian tigers are taller and heavier than Bengal tigers. They grow shaggy winter coats to deal with cold temperatures and tend to be less brightly colored than other tigers.

The Siberian tiger is an apex predator that feeds almost exclusively on red deer and wild boar. Both black and brown bears are occasionally hunted, but this is very rare. Brown bears have been known to hunt Siberian tigers as well; an equally rare occurrence. Siberian tigers also occur in the same habitat as wolves, though wolf populations tend to be much sparser in areas where the tiger is present. 
Photo: Jelenia Sika
Despite their massive size, attacks by Siberian tigers on humans are rare. They are known to be extremely solitary animals that prefer to avoid human interaction. Most attacks throughout history have been either by wild tigers that were provoked or captive-raised tigers that did not possess an instinctual fear of humans.

Monday, August 22, 2011

The Unique Vaquita

The vaquita holds the distinction of being both the smallest and rarest marine mammal in the world. Also referred to as the desert porpoise or gulf porpoise, the vaquita (Spanish for “little cow”) lives only in the northern half of the Gulf of California, the small wedge of ocean between mainland Mexico and Baja, California.

Vaquitas are less than five feet long and weigh about 100lbs as adults. They are smaller but similar in appearance to the better known harbor porpoise, with their most distinctive feature being the dark circles around their eyes and dark coloration around their mouths. They live in much shallower and warmer water than other porpoises and appear to swim and feed leisurely on a variety of small fish and squid.

Illustration: William Shepard
Vaquitas are critically endangered. From 1997 to 2008 the vaquita population dropped from an estimated 500 animals to fewer than 200. Though they have no natural enemies in their isolated habitat and have never been actively hunted, vaquitas are extremely prone to becoming entangled in gillnets used for commercial fishing. Conservationists and government agencies from Mexico, the United States and Canada are currently working together to establish vaquita sanctuaries and limit commercial fishing to save this unique animal from extinction.

Friday, August 19, 2011

The Magnificent Mountain Goat

Although called a goat, mountain goats are actually a member of the animal family that includes cows, antelope and gazelles. Its genus, Oreamnos, roughly translates to “mountain lamb”, which makes sense given the high altitude at which these animals live. Found exclusively in the high mountain ranges of western North America, mountain goats are excellent climbers that spend most of their time at elevations of up to 13,000 feet; far out of the range of most predators.
Mountain goats are white in color with a noticeable beard and rearward-curving horns on both sexes. They have a double coat that includes a dense under layer covered with an outer coat of hollow hairs that moult in the spring. This thick outer coat allows them to withstand temperatures as low as -50 degrees F and 100mph winds. For as sure-footed as they are, mountain goats are quite large. They usually stand over 3 feet at the shoulders, and weigh anywhere from 100-300lbs.

Due to their imposing size and the high altitudes at which they live, mature mountain goats are not easy prey. Though they do have to be wary of wolves, cougars, and bears, especially when traveling between peaks at lower altitudes, the biggest threat of predation comes from golden eagles, which have been known to attack young goat kids. Mountain goats can and will use their horns to injure or kill large predators or humans that get too close to their kids; however, they are not naturally confrontational animals.
Mountain goats prefer to live in groups of 3-50 animals and spend their time foraging for grass, moss, lichen and other high altitude foliage. They currently exist in significant numbers are considered a species of least concern by the International Union for Conservation of Nature

Thursday, August 18, 2011

The Pistol Shrimp - Nature's Crack Shot

When you think about the loudest animals in the ocean, usually whales come to mind. Some whale calls are among the loudest noises on earth and can be heard for many miles around. However, a significant amount of noise in the ocean is provided by a much smaller, 1-2 inch long shrimp called the Alpheidae, or pistol shrimp.
Pistol shrimp each have one specialized claw that is larger than the other. They are capable of snapping this claw together to produce a tremendous noise of up to 218 decibels; louder than a gun blast or a jet engine! The noise these shrimp produce is significant enough to actually disrupt sonar in submarines.

Though this snapping noise is often used for communication, pistol shrimp also use their unique abilities to hunt. When they snap their claws together a low pressure bubble is formed and a jet of water is shot out at 60mph. When this bubble collapses it momentarily produces a flash of light that is as hot as the surface of the sun! The shockwave from this collapse can easily stun the shrimp’s prey, allowing it to drag it back to its burrow for consumption.

Wednesday, August 17, 2011

Meet the Aardwolf

Although its name makes it sound like a combination of an aardvark and a wolf, the aardwolf is actually a type of hyena that lives in two distinct ranges in southern and eastern Africa.
Photo: Dominik Käuferle
At only about 30lbs, aardwolves are much smaller than other hyenas and are only a little larger than an average fox. Their peculiar name comes from their feeding habits. Aardwolves feed almost exclusively on termites, using their long and sticky tongues to root them out of the ground. Although they will rarely hunt small birds and mammals, termites make up over 90% of the aardwolf’s diet; a single animal can consume up to 300,000 of them in a night!

Unlike other hyenas, aardwolves are actually beneficial to farmers. They aren’t attracted to carrion, they’re too small to kill livestock and their copious termite consumption helps control insect populations. Though their population is small and their range is extremely limited, aardwolves are not in decline and are not currently considered threatened.

Tuesday, August 16, 2011

The World's Fastest Fish

Any time you discuss the world’s fastest animals the cheetah comes to mind; and while its 70mph sprint speed does make it the fastest land animal, it’s easily bested in outright velocity by the peregrine falcon, which can reach over 200mph in dives.

However, if you look under the sea there’s another animal that can give even the cheetah a run for its money in speed: the sailfish. Sailfish are members of the Istiophoridae family that also includes marlins and spearfish. They can be most easily recognized by their large sail-like dorsal fins that can run the entire length of the back. Like other members of the family, sailfish have long snouts that resemble swords and can grow to nearly 10 feet in length.
Photo: National Geographic
Sailfish are very prized by sport fisherman and do not have any real natural enemies other than man. This most likely has to do with the fact that the sailfish can outrun just about any other creature in the ocean, reaching speeds of nearly 70mph.

The sail on the sailfish’s back usually stays folded down when swimming, but can be raised when excited or alarmed to make the fish appear larger than it actually is. Scientists have also observed the sail being used to “herd” together the schools of fish for easier feeding. Sailfish come in a very wide variety of colors and have the unique ability to change colors almost instantly, a technique used to confuse prey and communicate with other sailfish.

Monday, August 15, 2011

The Sleepy Koala

Today is National Relaxation Day in the U.S.; a day that’s supposed to be celebrated by kicking back and not doing much of anything at all. Of course being as it’s a Monday there may not be much relaxation in store for many of us, but we can all take comfort in the fact that there is at least one animal that will have no trouble at all dozing the day away; the koala.
Koala doing what he does best. Photo: Sanjay Ach
Sometimes incorrectly referred to as koala bears, koalas are actually marsupials related to kangaroos, wombats and opossums and are indigenous to southeastern and eastern Australia. They are sometimes considered the laziest animals in the world due to the fact that they will sleep 18-20 hours per day.

However, this lazy lifestyle is one of necessity. Koalas almost exclusively eat eucalyptus leaves which are extremely low in protein and nutritional content. Therefore, the koala has evolved with a very slow metabolism and requires long periods of inactivity to properly digest and extract the maximum amount of nutrients from the leaves they consume. Of the four hours or so that they are awake each day, koalas spend two hours eating. The rest of the time is spent curled up on a tree branch napping the day away.

Friday, August 12, 2011

Are Crows the Smartest Birds in the World?

When you consider the true brainiacs of the animal kingdom it’s usually dolphins, chimpanzees and great apes that come to mind; with the exception of parrots, birds aren’t likely to make most people’s lists. However, research over the past decade is beginning to indicate that crows may not only be the smartest birds, but possibly more intelligent than even chimpanzees.

American crow - Photo by Walter Siegmund
The term “crow” is used to refer to any bird of the 40 or so members of the Corvus genus. Some members of the genus may also be called ravens or jackdaws. Crows can be found throughout most of the world, even introducing themselves to areas where they are not native. Most members of the genus are fairly large birds that are black in color.

Certain species of crows have shown remarkable intelligence not seen elsewhere in birds. New Caledonian crows are known for their tool making. In one test a crow was observed bending a piece of straight wire into a hook to lift a bucket of food from a vertical pipe; it had never been exposed to wire before. These crows also make tools out of grass and sticks to probe for insects in trees, and have even been seen dropping nuts on to busy streets so the heavy cars would crack them. Even more amazing, the crows would then fly down to intersections and only cross into the street with pedestrians to retrieve the nuts safely.

Crows also exhibit complex social behaviors, particularly seen in the common raven. Young ravens tend to make a large fuss when feeding on a carcass in order to attract other juveniles so they can feed in the safety of a group. Adults on the other hand stay whisper quiet when feeding so as not to attract uninvited guests. Like parrots, ravens are capable of mimicking almost any sound they hear, including human speech. They use this ability both to mock and confuse other animals, even mimicking the call of a coyote or wolf to attract them to a carcass that is too thick for the raven to open itself.

Thursday, August 11, 2011

Velociraptors Weren’t So Scary

Next to Tyrannosaurus Rex, probably no other dinosaur is as recognizable as the velociraptor. In the 1990 book and subsequent film Jurassic Park the raptors truly were the stars.
Depicted as six foot tall pack hunting lizards with razor sharp teeth and claws, the velociraptors of the movie were about as scary as dinosaurs get. The only problem is that real-life velociraptors didn’t look or act anything like that.
Illustration by Matt Martyniuk
Above is an illustration of what paleontologists believe the velociraptor really looked like. Quill knobs found in fossils prove that it was completely covered in feathers, and the long stiffened tail was likely used for balance. However, feathers or not, the biggest inaccuracy in the film and book was the velociraptor’s size, as in real life it only stood about two feet tall and weighed 30lbs.
Illustration by Matt Martyniuk
However, you can’t totally place the blame on author Michael Crichton. The raptors of the book and movie were based more upon deinonychus, a much larger ancestor of the velociraptor that lived 40 million years earlier and was over 11 feet long. At the time of the book’s writing, some paleontologists believed that the two were more closely related than they actually are.

Of course, the book and movie were both works of fiction and would have been much less entertaining if the main antagonists resembled a pack of angry roadrunners. Besides, as far as we know T-Rex was still pretty scary!

Wednesday, August 10, 2011

The Black Bear that's White

If you find yourself hiking the woods of coastal British Columbia, Canada there is a very slim chance that you might spot a bear that’s completely white. Although it may look like a small polar bear, what you’d actually be seeing is a Kermode bear, a rare subspecies of black bear.
Most Kermode bears look just like regular black bears. However, in this region and particularly on Princess Royal Island one in every ten Kermode bears is born white. Their stark white appearance against the green rainforest habitat has led to them being referred to by native peoples as “spirit bears”.

The Kermode bear’s white coloring is caused by a recessive gene; they are not albinos and are no more closely related to the polar bear than any other black bear.

Tuesday, August 9, 2011

Saving the Greater Prairie Chicken in Missouri

Greater prairie chickens, which are closely related to grouse, used to exist in the millions in the Great Plains. It is estimated that hundreds of thousands lived in Missouri alone before the 1930’s. However, when commercial farming took over the region in the early twentieth century the prairie chicken’s habitat was almost completely wiped out. Prairie chickens require large expanses of tallgrass prairie to survive and cannot exist on agricultural land. Today, less than seven percent of Missouri’s tallgrass prairie still exists and there are only about 500 prairie chickens left in the state.
Greater prairie chicken male
A subspecies of the greater prairie chicken known as the heath hen was once extremely common in New England. Easy to hunt and vulnerable to predation by introduced dogs and cats, the heath hen was a staple of colonial life in the region until it was finally driven to extinction on the mainland by 1870. Conservationists in Missouri are determined not to let the same happen to the greater prairie chicken.

In an effort to keep this native bird and its booming call from disappearing forever, a partnership of 20 state agencies called the Missouri Grasslands Coalition is working on a long-term project to restore the habitat of the prairie chicken and bring its numbers back into the thousands. This project has been going on for many years already as it requires overcoming several major obstacles to be successful.

Perhaps the biggest obstacle is the habitat itself. Tallgrass prairie is a unique ecosystem that cannot be used for farming or grazing; this presents a problem in a state like Missouri where 93% of all land is now privately owned. To overcome this, the MGC is working with landowners to provide prairie chicken habitat in exchange for subsidies.

Another issue is maintaining a breeding population. Because of the scarcity of tallgrass prairie, greater prairie chicken flocks only exist on “islands” throughout the Great Plains and the birds rarely migrate more than 10 miles away from where they were born. To establish populations, Missouri Department of Conservation officials are importing birds from Kansas, where they are more numerous, and placing the birds in tallgrass prairie conservation areas.
If you’d like more information about saving the greater prairie chicken, please contact the Missouri Department of Conservation here

Monday, August 8, 2011

The Laotian Rock Rat - Living Fossil

Happy Monday, everybody! After a week spent talking about sharks I figured it might be nice to focus on an animal today that most likely won’t ever get a minute on television, despite making a comeback after a vacation of at least a few million years! Meet the Laotian rock rat: living fossil.
Animals and plants that are considered to be living fossils are those that are nearly identical to a species only known from fossilized remains with no other living relatives. Cockroaches and aardvarks are two commonly known animals that are referred to as living fossils. The recently discovered Laotian rock rat may fit this description as well, but there is some debate.

Discovered in Laos in the late 1990’s, the Laotian rock rat was first thought to be so distinct from all living rodents that it was placed in a new family called Laonastidae. However, in 2006 this classification was debated by biologists and it was instead suggested that the Laotian rock rat is a relative of members of the ancient Diatomyidae family which has been extinct for 11 million years. The rat is commonly placed in this family now. If this is indeed the case, the Laotian rock rat would join sixteen other mammals that were once thought to be extinct only to be rediscovered, though none have been thought extinct for nearly this long. This type of occurrence is known as a Lazarus taxon.

The Laotian rock rat appears different from other living rats. Despite the similar appearance and coloring of its body, it has the long and bushy tail of a squirrel. Most are about 15 inches in length with a third of that coming from the tail and a weight of about a pound. These rats have thus far only been found in the Khammouan Province of Laos. Though little is yet known about this newly-discovered species, their limited range and pressure from trapping has led the ICUN to label them as endangered. 

Friday, August 5, 2011

Basking Sharks - The Lazy Predators

As we close out this week, we’d like to focus on a shark that just doesn’t get any respect; the basking shark. Although it’s one of the largest species of fish in the world, the whale shark is larger, so it won’t set any records there. It isn’t a vicious predator either, and despite being as long as a city bus poses absolutely no danger to humans or any large creature of the sea.

The basking shark gets its name from its appearance of relaxing (i.e. basking) in warmer waters near the surface while it feeds; and due to their massive size they are quite hard to miss. Basking sharks are usually 20-35 feet in length and weigh about 4 tons. The largest specimen ever confirmed was over 40 feet long and weighed an estimated 34,000lbs!
Basking shark filter feeding
Although basking sharks are sometimes mistaken for great white sharks, the two could not be more different. Whereas great whites are active hunters, the basking shark is a passive filter feeder. It feeds on zooplankton and small fish simply by swimming around very slowly with its enormous mouth wide open. Prey is snagged by the basking shark’s many sets of gill rakers. During this process, the shark naturally takes in a massive amount of water. However, unlike other filter feeding sharks that can close their mouths and pump this water out manually, the basking shark can only expel water by continuing to swim at its lumbering 3mph pace.
Basking shark head
Basking sharks do migrate throughout the year and can travel thousands of miles in a season. It is assumed that this travel is related to reproduction or following plankton blooms. Due to this migration, at certain times of the year basking sharks may be found in nearly every ocean of the world.

Thursday, August 4, 2011

The Thresher - The Shark with a Whip

To see a common thresher shark from the front you may think that it looks a lot like many other sharks. The streamlined, torpedo-shaped body and classic dorsal fin fit the profile perfectly. However, once you see that massive tail the thresher shark is unmistakable.
Pelagic thresher shark - Photo: Discovery
The thresher shark’s massive caudal fin isn’t just for looks, either. When hunting, the thresher will use its tail to slap the water around schools of fish to corral them. There have also been several reports of threshers using their tails like whips to stun or kill prey.

There are three species of thresher sharks. As its name suggests, the common thresher is the most widely distributed species and it is also the largest, reaching lengths of over 20 feet and weights of over 1,000lbs. The pelagic thresher is the smallest at about 10 feet long and less than 200lbs. The third species is the bigeye thresher, which features eyes that can be up to four inches in diameter for hunting in deep waters with little light.

Most thresher sharks prefer open ocean; depending on size and species they feed on a large variety of marine life, but prefer schooling fish such as mackerel and tuna as well as squid. Adult threshers rarely have any natural predators of their own.
Despite their large size and that fearsome tail, threshers pose little or no danger to humans. There has only ever been one reported attack by a thresher shark on a person and just a handful of attacks against boats. All of these attacks we most likely provoked, as the thresher is still highly prized by sport fishermen despite all species being nearly endangered.

Wednesday, August 3, 2011

Hammerheads - Sharks Apart from the Rest

Next to the infamous great white, the hammerhead is probably the most recognizable shark in the world. The distinctive shape of its head is undeniable, but there are a few other things you may not know about hammerheads that make them uniquely different from other sharks.
Photo: Barry Peters
First off, the hammerhead is not just one species of shark. Though the large Great Hammerhead may be the best known, there are actually nine different species of hammerheads in two separate genera. The two largest species are the great hammerhead and the smooth hammerhead at 20 and 16 feet in length, respectively. Most other varieties are significantly smaller, with the 3 foot long bonnethead shark being the smallest.
Bonnethead shark - Photo: Valerie Everett
Unlike most sharks which are lone hunters, hammerheads usually congregate in schools. Depending upon species and conditions these schools can range from just a few individuals to thousands of sharks in a single location. They primarily hunt for crustaceans and small fish near the ocean floor with the largest varieties preferring to hunt stingrays. All except the largest species’ are considered harmless to humans.

Another interesting characteristic is the way hammerheads reproduce. Unlike most sharks, hammerheads do not lay eggs. Rather, their young are nourished in a yolk sack inside the female. After the yolk as been depleted, these yolk sack structures, which are more akin to leather than to an egg, are laid by the female and the pups are born. Hammerhead shark litters can range from 12-40 pups each depending on species.

So what is up with the shape of that head anyway? Like all sharks, hammerheads have electroreceptor sensory pores called ampullae of Lorenzine that allow them to detect the electrical fields given off by other animals. It is believed that the hammerhead’s wide head allows these pores to be more spread out, thus allowing the hammerhead to detect prey more easily than other sharks. It is also thought that the wide spacing of the eyes gives hammerheads binocular vision, and it is known that great hammerheads will use their heads to pin prey against the ocean floor.
Photo: Su Neko

Tuesday, August 2, 2011

Sharks from Small to Huge

As I mentioned yesterday, this week is all about the celebration of sharks. And while tiger sharks and great whites may get most of the press, they are just a small part of the 400+ species' of these amazing animals. Today I thought I would show you the two bookends of the Selachimorpha (shark) superorder size-wise; the dwarf lanternshark and the whale shark.

Dwarf lanternshark - Illustration by Tambja
 The dwarf lanternshark is the smallest known shark species in the world. Found only in the southern Caribbean Sea near Venezuela and Colombia, this rare species of dogfish shark reaches a maximum length of  only eight inches and lives about 1,000 feet below the surface.

Whale shark - Photo by Zac Wolf
 On the other side of the spectrum is the massive whale shark; not only the largest shark but also the largest fish species in the world. Whale sharks of up to 41 feet in length have been confirmed, and they can weigh in excess of 79,000 pounds. In other words, they are as long as a city bus and weigh as much as 25 automobiles. Despite their massive size, whale sharks are not vicious killers. They are filter feeders and subsist mainly on a diet of plankton and small fish. They swallow massive quantities of water containing their prey when they feed, expelling the excess liquid through their gills and swallowing the leftover plankton.

Monday, August 1, 2011

Aquatic Cleaning Stations

While there may indeed be a week-long celebration of sharks on a certain network, today I thought I would present you guys with some of the unsung heroes of the marine world, the cleaner fish.

Like any animal, a fish can develop skin problems, become afflicted with parasites and get generally dirty. Without the ability to take care of any of these problems themselves, some fish have developed a mutually beneficial relationship with one another.

Certain species of fish are known as cleaner fish. They provide a service to other fish (even sharks) by removing parasites and dead skin from their bodies and food particles from their mouths. It’s mutually beneficial because the cleaner fish feeds on what it removes while the client fish reaps the health benefits.

A pair of cleaner wrasses go to work on a client
The best known cleaner fish is called the cleaner wrasse. These are small fish identifiable by their horizontal stripes. They congregate at “cleaning stations” near the sea floor in the Indian and Pacific oceans. When approached by client fish at these stations, the cleaner wrasses will go to work on whatever part of the client that needs cleaned, even swimming into their gills and mouths if necessary. Although the client fish are easily capable of eating the tiny wrasses, they recognize the service they provide and do not prey upon them.

Other marine animals that provide a similar service are several types of gobies and cleaner shrimp.