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Red Crab Migration and the Catatumbo Lightning: Amazing Nature

Linda Crampton is a writer and experienced science teacher with an honors degree in biology. She enjoys writing about science and nature.

The Christmas Island red crab is an attractive animal.

The Christmas Island red crab is an attractive animal.

Amazing and Awesome Nature

Nature is both amazing and awesome. It may also be very intriguing. Animals, plants, the atmosphere, and the Earth are involved in some impressive natural phenomena. Two of these phenomena are the annual migration of millions of red crabs on Christmas Island and the "everlasting" Catatumbo lightning storm in Venezuela. Both are fascinating examples of nature in action, and both have a link to the ocean.

Researchers estimate that forty to fifty million red crabs currently live on Christmas Island. When all of the adult crabs on the island migrate to the ocean at the same time in order to reproduce, as they do each year, the effect is spectacular.

The incredible Catatumbo lightning is seen over a very special lake in Venezuela that is connected to the ocean. The flashes of lightning are visible on roughly 140 to 160 nights of each year, for around eight to ten hours each night, and up to 28 times a second at the peak of the season. The repeating light show has occurred for centuries.

Christmas Island and the Red Crab

Christmas Island is located in the Indian Ocean south of Java and Sumatra. It’s a territory of Australia. The island’s name comes from the fact that it was discovered on Christmas Day in 1643. It’s rich in biological diversity and contains some unique organisms. 63% of the island belongs to a national park.

The scientific name of the red crab is Gecarcoidea natalis. It's native to Christmas Island and the Cocos or Keeling Islands, which are also located in the Indian Ocean and are also a territory of Australia. Its carapace (the shell over its back) may reach up to 4.6 inches in width. Males are generally bigger than females. Although the animal is usually red in colour, some individuals are orange. Very rarely, a red crab may be purple in colour.

A Christmas Island red crab feeding on dead leaves

A Christmas Island red crab feeding on dead leaves

The Life of a Red Crab

The red crab lives on land and is active during the day. It breathes by using both lungs and gills. The gills are located on each side of the body in a branchial chamber. In the red crab and its relatives in the family Gecarcinidae, the branchial chamber is enlarged and its lining is specialized. The lining is thin and contains many blood vessels for oxygen absorption. The chamber acts as a simple lung.

The animal is very sensitive to water loss from its body and digs a burrow for protection when its environment becomes unsuitable. It sleeps in the burrow and also uses it as a shelter during the day when the weather is too hot or dry. During the dry season, the crab stays in the burrow and blocks the entrance with a wad of leaves.

Red crabs live mainly in forests, but some set up their home in people's gardens and in crevices in rocks. They feed on fresh or dead leaves, flowers, fruits, and seedlings. They also scavenge material from the bodies of dead animals.

Mating in the Species

Reproduction takes place at any time from October to January. November and December are the most common months for breeding, however. They are generally the rainiest months of the year. Males begin the journey to the ocean before the females but are joined by females during the trip. The largest males reach the sea first after a journey of five to seven days.

After dipping their bodies in the sea to replace moisture loss, the male crabs dig a mating burrow on the terraces by the seashore. When the females arrive, they dip their bodies in the ocean. They then join the males in the burrows and mate there. Mating may sometimes happen outside of the burrows, however. After the mating process has finished, the males leave and return to the forests. The females stay to complete the reproductive cycle.

Reproduction Facts

The female lays her eggs about three days after mating with the male. She holds the eggs in the brood pouch on her abdomen. This pouch can hold up to 100,000 eggs. The female stays in the mating burrow while the eggs develop, which takes about twelve or thirteen days.

When the eggs are mature, the female releases them into the ocean. She vibrates her body in a dance-like motion known as a shimmy in order to release the eggs from the brood pouch. Once the pouch is empty, the crab begins her return migration.

The youngsters go through several larval stages in their development. When the ones that have survived have reached the tiny crab stage, they emerge from the water. They perform their own migration in order to find a site where they can develop into an adult, as shown in the video below. The crabs are reproductively mature when they are about four years of age.

Migration and Reproduction Problems

Migration is a dangerous time for the crabs. Dehydration and injury are both major threats. The crabs travel over roads as well as off-road areas to get to their destination. Officials erect barriers to try to guide the crabs along a route away from traffic, but some animals climb over the barriers. Roads are often closed during the migration to protect the crabs. In some places, tunnels have been built under roads to allow the animals to travel safely.

The crabs take a break in their migration if the weather becomes too dry, creating a temporary burrow as a home until the situation improves. They also pause if the phase of the moon is incorrect. The eggs are released as the high tide is turning when the moon is in its last quarter. If this moment is missed, the adult crabs will wait for a month to complete their reproductive cycle. The animals' behaviour is truly a wonder of nature.

Catatumbo Lightning over Lake Maracaibo

Catatumbo Lightning over Lake Maracaibo

The Catatumbo Lightning in Venezuala

The amazing Catatumbo lightning can be seen from far away and was once used by Caribbean sailors as a navigational aid. They referred to it as "the Lighthouse of Catatumbo. " In 2014, Guinness World Records gave the Catatumbo lightning the award for the highest concentration of lightning in the world.

The Catatumbo lightning storm is very unusual because it always occurs in the same area and at the same time and because it occurs so frequently. There is nothing special about the lightning itself, though. People have noticed that the lightning storm has a different colour at different times, but researchers say this is because the colour is altered by dust particles and water vapour in the air. People also say that no thunder is created by the Catatumbo lightning, but experts say that this is simply because observers are too far away to hear the thunder. The repeated and frequent formation of a thundercloud over the lake is very intriguing, however.

Formation of the Thundercloud

The Catatumbo lightning occurs where the Catatumbo River flows into Lake Maracaibo. The cause of the thunderclouds that produce the lightning isn't known for certain, but the cloud formation is believed to be triggered by the unique combination of air currents and topography in the area.

Lake Maracaibo is located in northern Venezuela and is connected to the Gulf of Venezuela, which is in turn connected to the Caribbean Sea, as shown in the map above. The lake contains brackish water because it's fed by both the ocean and several rivers, the largest of which is the Catatumbo River. The lake is surrounded on three sides by mountains.

Warm winds from the Caribbean blow over Lake Maracaibo and meet the cooler air flowing off the mountains that surround the lake. The cooler air mixes with the warmer air over the Catatumbo River and Lake Maracaibo, which is probably the main contributor to the formation of a thundercloud. The evaporation of warm water from the lake probably feeds the cloud. The surrounding mountains are thought to trap the air mass over the lake. The combination of these factors likely leads to the creation of a thundercloud, which eventually discharges electricity and produces lightning.

Cause of the Lightning Over Lake Maracaibo

Once a thundercloud forms over Lake Maracaibo, lightning is believed to be created by the same mechanism that exists in other places on Earth. The explanation below is an overview of the leading theory for lightning formation. The theory may not be completely correct, however, and there are gaps in our knowledge of the process. Strange as it may seem, we don't completely understand the cause of lightning. Its production is a rapid, complex, and still somewhat mysterious process.

Charged Particles and Ions

Lightning develops due to the formation of charges in matter. It's helpful to know a little about the basic structure of matter in order to understand how these charges develop.

Matter is made of atoms. An atom contains a nucleus containing positive protons and neutral neutrons. Negative electrons orbit the nucleus. The number of protons and electrons in an atom is the same, so the atom is neutral. The electrons have a lower mass than the protons and neutrons.

Under certain conditions, one or more electrons may leave an atom. As a result, the atom has more protons than electrons and has become a positive ion. The released electrons may travel through a conductor or be absorbed by a different atom. An atom that has gained electrons is known as a negative ion.

The technical name for a thundercloud is a cumulonimbus cloud.

The technical name for a thundercloud is a cumulonimbus cloud.

Production of Charges in a Thundercloud

A thundercloud is very tall. Inside the cloud, turbulent winds transport air and water droplets up to the cold upper section of the cloud. Here the water in the air freezes, creating ice particles. The ice particles are then carried downwards by wind currents, colliding with other ice particles as they travel. Electrons pass between the ice particles during the collisions.

For a reason that is not completely understood, smaller particles of ice develop a positive charge while bigger particles develop a negative charge. The heavier negative particles collect at the bottom of the cloud while the lighter positive particles are left higher up. This charge separation is the key to lightning formation.

Lightning is sometimes dangerous. This photo shows a lightning strike near buildings.

Lightning is sometimes dangerous. This photo shows a lightning strike near buildings.

A Basic Overview of Lightning Production

Stage One

Similar charges repel each other. The electron-rich, negative layer at the bottom of a thundercloud repels electrons in the surface of the Earth below the cloud or in the surface of an object projecting from the Earth. This gives the surface an unbalanced positive charge from the protons in its atoms.

Stage Two

Opposite charges attract each other. The negative electrons in the cloud are attracted to the positive surface of the Earth. They flow through the air towards the Earth in a channel known as a stepped leader. The electrons move in a series of steps that often branch.

Positive particles from the Earth are attracted to the negative particles in the cloud. They move up tall objects and then into the air through a channel known as a streamer or an upward leader.

Stage Three

When a stepped leader and a streamer meet, an electrical connection between the cloud and the ground is formed. Instead of consisting of a wire, as is often the case for electrical connections in our lives, this connection consists of ionized air. Ionized air allows for a much better flow of charged particles than normal air.

The electrons from the thundercloud accelerate towards the Earth through the connection that has been established and collide with air molecules. This causes the air to glow and produces the lightning flash, starting with the air closest to the ground. Although the negative charge moves from the cloud towards the ground, the lightning flash moves in the opposite direction. For this reason, it's known as the return stroke.

Fascinating Natural Phenomena on Earth

Natural phenomena such as earthquakes and tornadoes can be dangerous and have tragic consequences. Phenomena like the Christmas Island red crab migration and the Catatumbo lightning are fascinating and enjoyable to observe, however. They can also teach us more about the amazing world of nature and its behaviour and raise questions about its intriguing puzzles. Studying the phenomena is very interesting and is also educational.


© 2015 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on February 10, 2015:

Hi, DaphneDL. I agree - both of these scenes would be fascinating to observe! Thanks for the visit.

Daphne D. Lewis from Saint Albans, West Virginia on February 10, 2015:

The crab migration would be incredible to witness. I'd love to see the baby crabs hunting for safety after they're born. The Catatumbo lightning would be an amazing display to watch. The number of times it continues to strike would be fascinating.

Linda Crampton (author) from British Columbia, Canada on February 06, 2015:

Thank you very much for the visit and the comment, Deb.

Deb Hirt from Stillwater, OK on February 06, 2015:

These were fascinating topics and kept me riveted.

Linda Crampton (author) from British Columbia, Canada on January 21, 2015:

Thank you very much, Blackspaniel1.

Blackspaniel1 on January 21, 2015:

I find the lightning part fascinating.

Linda Crampton (author) from British Columbia, Canada on January 20, 2015:

Hi, Peggy. Thank you very much for the kind comment and the share! I appreciate your visit.

Peggy Woods from Houston, Texas on January 20, 2015:

Hi Alicia,

Nature is truly amazing. It was so interesting to read about the red crab migration on Christmas Island. The lightening displays in Catatumbo must truly be regular if sailors depended upon it to light up the skies. Enjoyed learning about these two different natural phenomenons. Your articles are always educational and worth reading. Will happily share!

Linda Crampton (author) from British Columbia, Canada on January 19, 2015:

Hi, Nell. Yes, the crabs and the lightning storm are certainly interesting! Thank you very much for the comment. I appreciate the vote and the share, too.

Nell Rose from England on January 19, 2015:

Hi Alicia, strangely enough we were talking about those crabs today! they are so clever aren't they? especially the bit about the moon influencing them, and the lightning storms are fascinating, great hub! voted up and shared, nell

Linda Crampton (author) from British Columbia, Canada on January 19, 2015:

Thank you very much for the comment, Blossom. I appreciate your visit.

Bronwen Scott-Branagan from Victoria, Australia on January 19, 2015:

Both of these topics on nature are so interesting. I enjoyed reading. They're well presented and would have made two hubs, no problem. Thank you for sharing all that information about our wonderful world.

Linda Crampton (author) from British Columbia, Canada on January 19, 2015:

Thank you for the visit and the comment, Devika!

Devika Primić from Dubrovnik, Croatia on January 19, 2015:

The Red crab is unique. You shared an amazing hub on a valuable topic. Informative useful.

Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Thank you very much for the kind comment, ologsinquito.

ologsinquito from USA on January 18, 2015:

The world is such a fascinating place. Thank you for reminding us with your many wonderful articles.

Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Thank you very much, PAINTDRIPS.

Denise McGill from Fresno CA on January 18, 2015:

I enjoyed this very much. How fascinating. It's almost like being there. Thanks.

Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Hi, Ann. Yes, nature is amazing! I feel the same way as you about lightning. It's beautiful and exciting, but I want to stay safe while I'm watching it! Thanks for the visit.

Ann Carr from SW England on January 18, 2015:

Nature is amazing, isn't it? This is such a fascinating hub about the crabs and the lightning. I love to watch a lightning storm, as long as I'm indoors!


Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Thank you very much, Bill. I always appreciate your visit and comment!

Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Thank you for the comment and the vote, Carolyn!

Bill Holland from Olympia, WA on January 18, 2015:

I always love your nature articles, and this one is no exception. Great stuff here, my friend.

Carolyn Emerick on January 18, 2015:

Hi had seen this migration in a documentary once, it is so fascinating! Thanks for sharing all this info and wonderful pics! Upvoted!

Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Thank you, Bill. I appreciate your visit and comment very much. I hope you're having a great weekend!

Linda Crampton (author) from British Columbia, Canada on January 18, 2015:

Thank you very much for the comment and for sharing the interesting information, Jodah. I appreciate your visit. The crabs and the lightning are both fascinating examples of natural phenomenon!

Bill De Giulio from Massachusetts on January 18, 2015:

Absolutely fascinating Linda. The Red Crab migration and the Catatumbo Ligthning are just two more examples of the amazing world in which we live. Thank you for the education, wonderful videos.

John Hansen from Australia (Gondwana Land) on January 18, 2015:

What a wonderful hub Alicia. I have seen quite a lot about the red crabs (I think we also call them coconut crabs) on Christmas Island because it is in Australian territory and houses one of our major detention centres for refugees who often try to come to Australia illegally. Only a few years ago a boat load of asylum seekers was destroyed in rough seas off Christmas Island and many people were killed......

The information on the Catatumbo lightning was very interesting and is quite a phenomena. When I read the title of the hub I thought somehow the lightning and crab migration must be linked...but not so. Voted up.

Linda Crampton (author) from British Columbia, Canada on January 17, 2015:

Thank you very much for the comment and the vote, Dipankar!

Dip Mtra from World Citizen on January 17, 2015:

Very informative and interesting. Voted up.

Thanks Alicia for writing such a great hub.


Linda Crampton (author) from British Columbia, Canada on January 17, 2015:

Thank you very much, Martie. I appreciate your comment. Like you, I find new information interesting. If the information is about something that I enjoy, it can definitely improve my mood!

Martie Coetser from South Africa on January 17, 2015:

How very very interesting is the instinctive behaviour of red craps. Thanks for all the delighting information, Alicia. I say delighting, as new information is such a natural anti-depressant and actually tonic, as it gives us a well-needed pep.

The Catatumbo Lightning in Venezuala, too, is an amazing phenomenon.

You are amazing, feeding us all the time with the most interesting information and so very well presented.

Linda Crampton (author) from British Columbia, Canada on January 17, 2015:

Thanks for the second comment and for sharing the information, Phyllis. I think it's wonderful that people go to such trouble to protect crabs during their migration.

Phyllis Doyle Burns from High desert of Nevada. on January 17, 2015:

I forgot to mention that I have seen bridges, some quite large, built for crab migration so they can cross roads safely. Bing has a lot of images of these bridges, and tunnels, too. Providing tunnels, like they do on Christmas Island is such a great thing to do. Again, I am fascinated with your hub.

Linda Crampton (author) from British Columbia, Canada on January 17, 2015:

Thank you so much, Phyllis! I appreciate your kind comment, the votes and the share a great deal. I'm glad that you enjoyed the hub. It covered topics that I find very interesting.

Phyllis Doyle Burns from High desert of Nevada. on January 17, 2015:

The red crab migration is fascinating. And to see the tiny babies migrate to where the adults are is just phenomenal. I loved watching those videos and reading all your interesting information on the red crab. Lightening has always fascinated me, but I have never heard of the nightly show at Catatumbo. That is incredible. Thank you, Linda, for writing this hub - I so enjoyed reading it.

Voted Up, across and H+

Linda Crampton (author) from British Columbia, Canada on January 17, 2015:

Thank you very much for the comment, the votes and the shares, Faith. I appreciate your kindness, as I always do! Blessings to you, too.

Faith Reaper from southern USA on January 17, 2015:

How fascinating to read of the Red Crab migration and the Catatumbo lightning. Yes, nature is truly amazing. I am just blown away that such lightening can occur from eight to ten hours each night for that many days out of the year! What a phenomenon.

How appropriate it seems that the Red Crab inhabits Christmas Island. I have not heard of Christmas Island before. As I always state when I read your hubs, I learn so much.

Another memorable hub!

Up ++++ tweeting, pinning, G+ and sharing

Blessings always