How do you tell the difference between Tortoises, Terrapins and Turtles?

01. June 2012 · 2 comments · Categories: International Wildlife · Tags: , ,

Leopard tortoise (Stigmochelys pardalis)

All the 250 or so species of Tortoises, Terrapins and Turtles are reptiles. Scientists refer to all of them as Chelonians, because they all belong to the taxonomic order known as Chelonia, derived from the Greek word for tortoise. They are all cold blooded (ectothermic), have scales and lay eggs. So what are the differences and how can we tell them apart?

The animals can be differentiated from there habitat – where they like to live, where they call home. The Tortoise is terrestrial, living on land. The Terrapin is aquatic, living in fresh or brackish water. While the Turtle is also aquatic it makes its home in seawater.

 

What the species eats can also be used as a general way of distinguishing the majority of the different species. A Tortoise is a vegetarian; a Terrapin is omnivorous, while a Turtle is carnivorous.

Diamondback Terrapin (Malaclemys terrapin)

There are also major physical differences between the species, a Tortoise, if it can retract its head, will do so directly back into its shell. The carapace (the upper shell) of the Tortoise is domed. The Terrapin and Turtle both have a more flattened carapace to allow them to be more streamlined in their aquatic environment. A Terrapin retracts its head sideways, while a turtle cannot retract its head. Tortoises’ feet have claws, to allow it to move easier on land, terrapins have webbed feet, but still retain claws, while Turtles feet have become flippers.

Of course the world is a very big place and the species of Chelonians are very diverse, from the largest Leatherback Turtle (Dermochelys coriacea) which can reach 8 feet (2.4 m) in length, to the diminutive Bog Terrapin (Clemmys muhlenburgii) 4.5 inches (11.4 cm) for example, there will probably always be exceptions to the rule somewhere but these facts described above will mean, with any luck, you will be able to the difference between any Tortoise, Terrapin or Turtle you come across!

Hawksbill Turtle (Eretmochelys imbricata)

The original question is not as clear cut as it might appear however. While in British English the points above hold true, different parts of the world using different types of English use the terms in very different ways! For example in American English the word Turtle is used as a general term for all the aquatic species, while Tortoise is used for land dwelling animals. In Australian English Turtle is used for both marine and freshwater species, while Tortoise is used for species that live on the land. This can make using identification books or websites from these countries a bit confusing! So when you’re identifying species from these areas of the world or from resources produced in these areas its always best to keep these facts in mind.

How do Atlantic Salmon find their way home?

16. May 2012 · Write a comment · Categories: International Wildlife · Tags: , ,

Atlantic Salmon (Salmo salar) (WC)

The Atlantic salmon (Salmo salar) is an anadromous migratory fish found in the temperate and arctic regions of the Northern Hemisphere. The word ‘anadromous’ is a posh term for the fact it is the fish’s habit to migrate from the sea into freshwater to spawn. These fish make an astonishing journey during their lifetime, crossing the whole of the Atlantic Ocean and returning.

The life cycle of salmon is fairly complex. Initially, spawning takes place in streams. Eggs are buried in gravel, the eggs then hatch, and young salmon, known as alevins emerge from the egg. Alevins remain within the streambed until their yolk sac is exhausted. When development is complete, fry (baby fish) emerge from the gravel. The fry feed on the larva of insects. After one to three years of growth, juvenile salmon, called parr, migrate to estuaries, metamorphosing into smolts. Still with me? The transformation from parr to smolt is a complex change, in which the fish acquires the ability to survive in seawater. After this change salmon are then ready to move to the sea to take advantage of the rich feeding grounds.

After one or more years at sea, salmon mature and make their return migration to their hatching stream. Atlantic salmon may complete several migrations and spawning, unlike all the Pacific salmon (Oncorhynchus) species which die after spawning. Their extremely accurate ability to return back to the same stream that they were hatched from has mystified science for many years.

It is thought that one of the most important navigational tools for Atlantic salmon is their sense of smell. During certain stages of development salmon are thought to imprint on smells, a hormone (Thyroxine) secreted by the thyroid gland. This hormone ensures the fish only imprints on odorants that will help it to migrate. Letting it only remember the green green waters of home!

The Thyroxine hormone is also thought to increase the chances of migration. It does this by increasing or decreasing a salmon’s water salinity preference, making them move downstream towards the sea or freshwater. The thyroid gland is stimulated by the nervous system, producing hormones in response to what’s going on around it. These are thought to include water flow rate (influenced by rain) and the temperature of the water. This makes the migration seasonal in nature, by migrating only at certain times of the year, the salmon increase the survival of their young.

During migration it is thought that salmon can detect smells from their river on the currents in the ocean, using their odour memory to guide their return journey. It is also theoght that salmon can detect smells from other fish, detecting whether they are related. It is thought the shoals that form in the sea may become family specific due to this, accentually meaning that salmon follow related fish as they are travelling to the same location as them.

Although smelly cues must help salmon locate their river when in fairly close proximity, salmon must have other navigational tools when in the open sea where any odour would be diluted, becoming undetectable. Research has shown that some fish species can be sensitive to the sun’s position. It is highly probable that salmon use the sun’s position as a way of determining direction, using it as a navigational tool.

It is suspected that salmon also have the ability to sense magnetic fields, using this to navigate. Magnetic minerals in the creature’s brain may function as a biological compass. Salmon fry will change their orientation when subjected to an artificial magnetic field, illustrating their ability to sense these fields. It is thought that the fish imprints a memory of its magnetic latitude and longitude at the time it enters the ocean, controlled through the use of hormones in the same way as odour memories.

There is also thought to be a strong genetic link to the migratory habits of salmon. This factor has been highlighted by the wild population breeding with escapees from fish farms. These captive bred fish seems to weaken the migratory instincts of the wild population.

Atlantic salmon can make several migrations and spawning in its lifetime, this could mean that a certain amount of the journey could be learned or memorised, but recent evidence seems to have discounted this idea. Evidence of the strength of the genetic instinct to migrate in these animals was recently documented in Sebago salmon (Salmo salar sebago) found in land locked Lake Sebago, USA. The population immediately began migrating again when a dam was removed, giving the population access to the sea again. The instinct to migrate survived for 150 years in the landlocked salmon. This evidence suggests to me that learning from other fish and remembering routes is not the source of the migratory behaviour exhibited.

The exact mechanism as to how the fish find their way home may never be fully understood by science, but the accuracy and precision of the species ocean navigation is a startling reminder of the complexity of the natural world around us!

Stop Whaling Now!

12. May 2012 · 2 comments · Categories: Conservation · Tags: , ,

Bowhead Whales (Balaena mysticetus) (WC)

Whales are warm blooded aquatic mammals and the largest creatures on earth. There are about 80 species of Whale, the magnificent Blue Whale (Balaenoptera musculus) being regarded the largest animal that has lived on this planet ever! They are some of the most awe inspiring creatures alive! Whales are also considered highly intelligent, research suggesting they have brain cells previously only found in humans and other higher primates! The preservation of such unique intelligent and amazing creatures for future generations must be a priority!

Archaeological evidence suggests that Stone Age people were hunting Whales for food as long ago as 2,200 B.C. They hunted slow-swimming, coastal species such as the Bowhead (Balaena mysticetus), Grey (Eschrichtius robustus) and Right Whales (Eubalaena glacialis, Eubalaena australis, and Eubalaena japonica). This subsistence hunting is still practised by some societies such as the Inuit people of North America and Greenland, where the Whale plays an important part in the people’s survival as well as being deeply imbedded in their local culture. These practices are far removed from the commercial whaling industry methods that were first developed in the seventeenth century, evolving into the highly sophisticated but still barbaric practices used today such as the use of sonar, helicopters, and long range explosive harpoons.

So sophisticated did this hunting become that whale species numbers plummeted dramatically, until finally in 1948 the International Convention for the Regulation of Whaling was created and the International Whaling Commission was established. Today, the International Whaling Commission has 85 member states, including whaling countries, former whaling countries, and countries that have never had whaling industries but joined to have a voice in the conservation of whales.
However, the whaling nations of Japan, Norway and Iceland retain politically influential whaling industries that wish to carry on whaling on as large a scale as possible. All three countries are exploiting loopholes in the Whaling Convention in order to kill nearly 2,000 whales each year despite the International Whaling Commission’s moratorium on commercial whaling.
Norway hunts whales under its objection to the convention, and Japan has been whaling under the guise of supposedly carrying out “scientific research“. Iceland joined the International Whaling Commission with a formal objection to the convention in 2002 and, although claiming they would not undertake commercial whaling before 2006, immediately began another suspect “scientific whaling” program.
I really struggle to fathom that in this so called enlightened modern age, three so seemingly ‘developed’ countries still persist in cruelly hunting Whales! It is easy to feel helpless as an individual against changing Government policy, but there is a simple way to make your feelings clear, and as the proverb goes “large streams from little fountains flow, and tall oaks from little acorns grow” so do your bit by showing your outrage at the continued commercial Whaling in the world!
Follow the link below and sign the International Fund for Animal Welfare’s (IFAW) petition to stop whaling and create ocean sanctuaries for Whales to live in safety!
IFAW STOP WHALING NOW!
Check out this stunning footage of Whales in the wild to realise what we are at risk of losing!

Persistent, sustained public pressure can be a powerful influence on democratic process – it is perhaps only continued international protest, aimed particularly at those few countries still insisting on Whaling, which will hopefully ensure Whales remain protected and therefore preserved for generations to come.

What is the difference between a Cocoon, a Chrysalis and a Pupa?

09. May 2012 · 3 comments · Categories: International Wildlife · Tags: ,

Old World Swallowtail (Papilio machaon) Butterfly Chrysalis (WC)

Many thanks to “P” from England for taking the time to message me and asking this intriguing question! So what is the difference between a Cocoon, a Chrysalis and a Pupa? Let’s find out!

All insects go through a series of ‘instars’ or molts or life changes as they mature (called metamorphosis) because, unlike with mammals like us, their growth is constrained by their hard exoskeleton (external covering).

A Pupa is a life stage of some insects undergoing transformation. The Pupae of different groups of insects have different names, in the Mosquito family they are known as ‘Tumblers’. With Lepidoptera, Moths and Butterflies, the first life stage is the Ovum or Egg, the second stage the Larva (Larval stage) or Caterpillar, the third stage the Pupa (Pupal stage) is known as a ‘Chrysalis’ and finally it becomes the ‘Imago’ or adult, obviously commonly termed the actual ‘butterfly’ or ‘moth’. So a Chrysalis is the pupa stage of a Moth or Butterfly (Lepidoptera).

A Cocoon is a casing of spun silk produced by many insects to form a protective covering for the Pupa. Many Moth Caterpillars for example produce silk cocoons. Cocoons can be of various types, from hard to soft, with various colours dependent on the species involved.

Virginia Tiger Moth (Spilosoma virginica) Cocoon (WC)

Many people state that a Moth Pupa is enclosed in a Cocoon and a Butterfly Pupa is enclosed in a Chrysalis. However, the proper use of the terms is that the Chrysalis is the term for the Butterfly or Moth Pupa itself, and Cocoon is a protective silk covering. The fact that few, if any, Butterfly species produce protective silk Cocoons and the majority of Moths do is probably the root of this misinterpretation.

So to summarise the Pupa is a life stage that some insects go through, between the larva and adult stages. A Chrysalis is the name of a Moth or Butterfly (Lepidoptera) pupa. A Cocoon is a protective covering around the Pupae or Chrysalis of some insects. Hope this answers your question “P” and thanks again for taking the time to message me!

Interested in Butterflies? Why not check out my article on how to attract them to your garden!

The Big (Not) Bad Wolf: The Canadian Tar Sands Disaster

05. May 2012 · 1 comment · Categories: Conservation · Tags: , , , ,

 

The Wolf sadly underthreat from the tar sands oil industry in Alberta, Canada.

Tar sands oil is one of the most destructive, dirty, and costly fuels in the world. The crude bitumen contained in the oil sands mining project in Alberta, Canada (possibly the largest industrial project in human history) is described by local authorities as: “petroleum that exists in the semi-solid or solid phase in natural deposits“. To extract this ‘solid petroleum- like’ substance, Alberta oil companies are digging up pristine forest and leaving behind huge toxic wastelands.

From all independent reports, harvesting the Alberta tar sands in Canada is an extreme environmental disaster. By its very nature mining and extracting tar sands destroys enormous swaths of important ecosystems, produces lake sized reservoirs of toxic waste, releases toxic chemicals into the air when it is then refined for use, and produces significantly more global warming gases than fuels made from even other still highly polluting conventional fossil fuels.

In the latest staggering display of the Alberta tar sands industry’s attack on the natural world, the government of Alberta has made plans to initiate a large scale Wolf (Lupus lupus) cull, in a blatant bid to provide cover for the destruction wrought by the industrialisation of the areas boreal forest ecosystem. The authority’s justification for this slaughter is to prevent further declines in the number of Caribou (Rangifer tarandus) in the area. Despite the fact Caribou and Wolves been co inhabits of the northern hemisphere for around 1.6 million years! The loss of habitat and habitat fragmentation and degradation from the tar sands mining project themselves being the true cause!

The proposed cull will involve the slaughter of an estimated 6,000 wolves that will be systematically gunned down by hunters, and even more horrifically poisoned with strychnine laced bait. Strychnine poisoning progresses painfully from muscle spasms to convulsions to suffocation over a period of hours; definitely making it not a humane way of culling any animals even if it were justified!! Using poison as a culling method also puts other non targeted species at risk, birds of prey and cougars for example. Feeding on the poisoned bait or scavenge on the carcasses of poisoned wolves themselves.

Frankly I find myself truly disgusted by this awful situation and find it astonishing that in this supposedly enlightened modern age Governments can still consider this an ethical way to act towards the natural world!

Check out this youtube video to find out more about this distressing subject and hopefully if enough people hear about it something can be done to help save these magnificent Wolves and also preserve the beautiful habitat they make their home!

Connect the Dots – Climate Impacts Day

02. May 2012 · 2 comments · Categories: Uncategorized
Climate Impacts Day – find out more at http://www.climatedots.org/

Climate change, driven by the action of mankind, and its impact on the environment have been seen to affect all living organisms on this planet from the smallest to the largest! Species extinction and distribution of wildlife has been directly linked to this change in climate.

‘Connect the Dots’ (http://www.climatedots.org/ ) an international organisation hopes to highlight this massive problem, and show what we as individuals can do to help. They have designated the 5th May 2012 as CLIMATE IMPACTS DAY! And invite us all to take part in events and activities to promote awareness and help educate people of this important subject.

Here’s what part of their website says about this worthwhile project:

“Record-breaking heat waves in Russia, wildfires in Australia, floods in Thailand. Every time we pick up the newspaper and read about another record-breaking natural disaster, it becomes increasingly clear that climate change is not a future problem — it’s happening right now.

Connect the Dots is a project of 350.org and our partner organizations, to shine a spotlight on the connections between extreme weather and climate change. We will use those connections to issue a wake-up call for our communities, the media, and our politicians.

We’ll kick off the project with Climate Impacts Day on 5/5/12, when thousands of communities around the world come together to take action to Connect the Dots and call for urgent action to stop the climate crisis.

Who: You, your neighbors, family, friends, and the rest of climate movement.

What: Actions – rallies, presentations, art projects, and more – that help your community connect the dots between extreme weather and climate change.

Where: All over the world.

When: May 5, 2012 (and beyond)

Why: Because climate change is not a future problem. It is happening right now, and it is devastating communities around the world. The world needs a wake-up call, and there’s no time to lose!”

Check out their website: http://www.climatedots.org/ and check out which events are occurring in your area or to even create an event yourself!

Good luck with Connecting the Dots everyone!

 

Why do Giraffes have such long necks?

01. May 2012 · 2 comments · Categories: African Animals · Tags: , ,
Giraffes (Giraffa camelopardalis) the tallest living terrestrial species on Earth!

Giraffes (Giraffa camelopardalis) are the largest ruminant and the tallest living terrestrial mammal species on Earth! The tallest specimen ever scientifically recorded was a bull (male) of the Masai subspecies (Giraffa camelopardalis tippelskirch), that stood a staggering 20 feet (6.09m) high! Weighing in at 545 to 1,905 kg (1,200 to 4,200 lbs), Giraffes still manage to run at up to 35 mph (56 km). The Giraffes’ head is about 3 meters (9 ft) above the heart which makes it very difficult for the heart to pump blood to the brain. To cope with this the Giraffe has the highest blood pressure of all mammals and its heart can weigh up to 10 kg (22 lbs)! Besides their long necks, Giraffes also have long, grasping tongues, which can extend 45 cm (18 in) to reach tasty inner tree leaves.

Evidence from the fossil record suggests that Giraffes evolved from deer like animals with a much shorter neck. By about 1 million years ago, modern animals we’d recognise as Giraffes had appeared on the African savannah. Evidence has shown that the Giraffes long neck is a real hindrance obviously costing a lot of energy to grow and maintain but that it also has a large survival cost. For example studies have shown that male Giraffes, with their larger necks, were about twice as likely as females to be killed by a predator – mostly Lions (Panthera leo).

So why though did these long necks evolve? Until fairly recently, the most commonly suggested theory involved finding food. Individuals that were born with longer than average necks were thought to have a feeding advantage, since in times of adversity, they could reach higher into trees to forage for leaves. Longer necked individuals were more successful at surviving, and passed their long neck genes onto their offspring. Over many generations, the modern long necked Giraffe we are familiar with evolved.

In the 1980s, scientists in Africa decided to compare this theory to the realities of Giraffe life. A study showed that the main criterion that determines the dominance among male Giraffes is neck size. Other studies found that despite their long necks, Giraffes spent most of the dry season when food was scarce feeding in low bushes rather than in tall trees. In the rainy season, when leaves were green and plentiful, Giraffes were more likely to turn their attention tree ward. Also, observations of Giraffes have shown that over 50% of the time, they feed with their necks horizontally. So while a long neck obviously allows Giraffe to reach more of a range of food, it didn’t seem to provide enough of a survival advantage in scarce times to account for its evolution. Obviously some other evolutionary selection pressure was at work.

Evidence found that a long neck did give an individual Giraffe an advantage, but not in the way that was first thought. An average male Giraffe’s neck weighs 90kg (200 lbs) and can stretch 1.8 m (6 ft). Giraffes fight over females by swinging their necks and heads like a medieval ball and chain. The longer and heavier the neck, the more momentum behind the often bone-shattering head slams. Research has found that males with the longest, most massive necks tended to win the mating contests, obviously, allowing their genes to be passed down to future generations.  It’s been suggested that competition for mates that pushed the evolution of the Giraffe’s neck, with longer-necked animals more successful at reproducing. Female Giraffes have many of the same genes, so their necks are long, too. But the females’ necks stop growing in adolescence – while male Giraffes go on to add nearly 45kg (100 lbs) of neck weight as they reach adulthood.

The standard story about why Giraffes have evolved their incredibly long necks states that this trait has helped them in reaching to higher leaves. This story, however, is probably wrong. Giraffes are obviously capable of feeding on higher leaves than other animals but this advantage doesn’t seem to be sufficiently great to justify the costs of having such a long neck, the advantage in getting mates (sexual selection) seems to be a much more likely explanation for this incredible wonder of the animal kingdom!

 

The Great Easter Newt Hunt

01. April 2012 · Write a comment · Categories: Conservation · Tags: , ,

The Great Easter Newt Hunt is almost here! This yearly event is organised by a partnership of the ‘Amphibian and Retile Conservation Trust’ and ‘Amphibian and Reptiles Groups of the UK’ and is taking place between the 6th and the 15th April 2012. You are invited to record the numbers of newts you can see in your very own garden pond! The information will be used to hopefully learn more about the distribution and abundance of British Newts and help produce information on newt conservation in an urban environment. It’s a great opportunity to get involved in a scheme to help the conservation of our native newts and should only take two 10 minute periods of pond investigation, and will probably be more enjoyable and definitely more original than the usual old garden Easter egg hunt!

Amphibians, like newts, are one of my favourite groups of animals, their global diversity and complex life cycles make them an intriguing area to investigate. Amphibian species are what are known as “indicator species”. This means animals that are particularly sensitive and are largely the first ones to disappear or be affected by to changes in an ecosystem. These changes can be diverse, from global issues such as climate change for example, or more localised such as environmental pollution leaking from a nearby industrial area.

Newt species are particularly vulnerable to these changes due to a number of reasons, for example their semi permeable skin allows toxins and other pollutants easy access to their delicate insides from the environment around them. Aquatic environments where amphibian species make their home, if only briefly in some cases are fairly vulnerable to environmental change, e.g., pollution, from agricultural runoff for example, as well as climate change, e.g. flooding or drying out. Also the fact that in general newt life cycles include terrestrial, as well as aquatic habitats means they are exposed to changes in both areas.

In the British Isles, omitting the odd escapee or release of foreign animals, there are three newt species.

Smooth Newt (Lissotriton vulgaris)

The commonest of these is the Smooth Newt (Lissotriton vulgaris), reaching around 10 cm in length. Females and males outside the breeding season are pale brown or olive green, often with two darker stripes on the back. Both sexes have an orange belly, although it is paler in females, their throats are covered in rounded black spots. During the breeding season the male is conspicuously darker than the female, with a small crest along the spine and dark patterned spots covering the rest of its body.

 

 

Palmate Newt (Lissotriton helveticus) (WC)

The Palmate Newt (Lissotriton helveticus) is the smallest British species, reaching only around 9 cm in length. It is olive green to brown in colour, with a yellow/pale orange belly, although it lacks the spotted throat of the Smooth Newt. The males can be distinguished due to a thinner thread like tapering at the tip of the tail, as well as darker markings during the breeding season.

 

 

Great Crested Newt (Triturus cristatus)

 

 

The largest and rarest British species is the Great Crested Newt (Triturus cristatus), this is the only newt species protected by the Wildlife and Countryside Act 1981, which makes it an offence to harm or even disturb them. This species can reach up to 15 cm in length, and can appear almost black in colour, with an orange to yellow belly. The males can be distinguished by the ragged crest along their backs.

 

 

More information and the necessary hunt procedures and forms to take part can be found on the Great Easter Newt Hunt website at:

www.newthunt.org

Happy Easter to you all and Good Luck with the newt spotting!

Why do Orang-utans have red / orange hair?

01. March 2012 · Write a comment · Categories: International Wildlife · Tags: , ,

Sumatran Orang-utan (Pongo abelii)

The name Orang-utan, comes from the Malay for “person of the forest”, the word orang being Malay for person – so is not derived from the colour orange at all, as some people think. There are actually two species of Orang-utans currently recognised, the Sumatran Orang-utan (Pongo abelii) and the Bornean Orang-utan (Pongo pygmaeus). The fact these ‘species’ can interbreed freely when not isolated geographically, as they are in the wild, makes me wonder at this separate species classification, but that’s a discussion for another day!

Anyway, Orang-utans, native to Indonesia and Malaysia, are the largest living arboreal (in trees) animals, and due to this life style they have proportionally longer arms than the other, more terrestrial, Great Apes. Orang-utans are the most solitary of the Great Apes, feeding primarily on fruit. They are also considered among the most intelligent of animals, making use of sophisticated tools, for example stick tools to aid the removal of seeds from tough fruit. One of the most striking visual things about these animals, however,  is their seemingly conspicuous reddish-orange hair, instead of the typically dark brown and black of their close relatives, such as the Gorilla (Gorilla gorilla) and the Chimpanzee (Pan troglodytes) (ignoring the flamboyantly coloured Great Ape Homo sapiens that is!).

Bornean Orang-utan (Pongo pygmaeus)

Why has this different colour evolved? Orang-utans’ hair colouring, although conspicuous when seen in isolation, does actually help them to blend in their native habitat. The water in the swamp forests, where Orang-utans live in the wild, tends to be a muddy orange due to peat sediment. Sunlight reflected off this water can give the forest an orange cast. This orange cast effectively makes the Orang-utans camouflaged and surprisingly hard to see in mottled light through the forest canopy.

Another explanation lies in the way sunlight penetrates the forest canopy, bouncing off plants as it does so. Plant leaves absorb the red, orange and violet wavelengths of light and use this for photosynthesis, while reflecting the green. So by the time sunlight has reached the forest floor, it has been robbed of red and orange wavelengths. Orang-utans hair looks dark brown and therefore is far harder to see in this sort of light.

Predators on the ground would also view Orang-utans in the canopy as mere silhouettes. In such circumstances orange may stand out less than black, which may be more suited to blending in with the forest floor, explaining why terrestrial African Great Apes such as Gorillas are of a far darker hue. Other canopy dwelling arboreal primates have a similar reddish orange colour to Orang-utans, for example Red Langurs (Presbytis rudicunda).

Whatever the reasons behind the evolution of this animals colouring, their intelligence and uniqueness and the fact both species (populations) of Orang-utans are considered endangered, meaning that conserving them for future generations is of truly great importance!

 

How do you tell the difference between Alligators and Crocodiles?

01. February 2012 · Write a comment · Categories: International Wildlife · Tags: , , ,
Comparison of American Alligator (left) and American Crocodile (right) (WC)

At a glance Crocodiles and Alligators can appear very similar; in fact many people use the term interchangeably! Many people would be surprised to learn, however, that there are actually 23 different species of Crocodilians alive on Earth today! This includes species of Crocodile and Alligator, and also species of Caiman and the Gharial, making identification between them even more cryptic! There are, however some general rules that make separating the different species easier.

Crocodilian species can also be distinguished from the habitat type and geographic area that they are found. For example, although both Alligators and Crocodiles have glands on their tongues that help cope with high salt content in water, only the Crocodiles gland appears to function, or function effectively. This fact means Crocodiles are far more likely to be found in saltwater, than Alligators. Alligator species, of which there are two, are restricted geographically to the southeast of the United States of America, the American Alligator (Alligator mississippiensis) and the Chinese Alligator (Alligator sinensis) in the Yangtzee River in China. Caiman species are found in Central and South America, while the Gharial (Gavialis gangeticus) is native to India. Crocodile species have a far wider range, living throughout the tropical waters of Africa, Asia the Americas and Australia.

Physically, Alligator and Caiman species have wider shorter heads, and a more U-shaped mouth than the V-shaped snout of the Crocodile species. The Gharial has an even more impressive elongated narrow snout, which makes their identification fairly easy.

The Indian Mugger Crocodile (Crocodylus palustris), however, breaks this general rule as its jaws are superficially very similar in shape to those of an Alligator, that said other characteristics mark it as a Crocodile, for example it’s teeth. In Alligators, the upper jaw is wider than the lower jaw and completely overlaps it. Therefore, the teeth in the lower jaw are almost completely hidden when the mouth closes, fitting neatly into small depressions or sockets in the upper jaw.

In Crocodiles, the upper jaw and lower jaw are approximately the same width, and so teeth in the lower jaw fit along the margin of the upper jaw when the mouth is closed. Therefore, the upper teeth interlock with the lower teeth when the mouth shuts. As the large fourth tooth in the lower jaw also fits outside the upper jaw, there is a well-defined constriction in the upper jaw behind the nostrils to accommodate it when the mouth is closed. This protruding tooth is the most reliable visual feature to define if a species is an Alligator or a Crocodile.

So the next time you see a large unidentified Crocodilian coming towards you, stop and think about which species it could be, or better yet, RUN and have a good think once you’re safe!

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