Majestic whale sharks, the gentle giants of the shark family.
Weighing in at 9 tons (20,000 pounds) and typically growing to around 10 meters (32 feet) long, the whale shark is the largest living species of fish. Despite the name, it is not a whale, though it is the size of one. Like many kinds of whales, it filter feeds on plankton.
Many things about the whale shark have remained unknown to science; how long they can live, their mortality rate, and how exactly to determine the age of a specimen from its remains was chief among them. However, these questions are now a little closer to being settled. In a study recently published in Frontiers in Marine Science, scientists explain how they were able to date the bones of two whale sharks who met their fate earlier than they may have expected.
Like trees, whale sharks' bones have growth rings. Scientists have known about these rings for a while, but how quickly the rings grow has been unknown. It is difficult to use them to estimate the age of a shark if you aren't sure how much time each ring represents.
A whale shark vertebra from Pakistan, in cross section, showing 50 growth bands
Image: © Paul Fanning, Pakistan node of the UN Food and Agricultural Organisation
This is where carbon-14 comes in. As a result of nuclear bomb tests during the Cold War, large quantities of carbon-14 were put into the oceans. The isotope slowly made its way up the food web and into the bodies of larger animals. Knowing the yearly changes in the amount of carbon-14 in the oceans due to bomb testing, scientists merely had to compare that data with the changes seen in the sharks' bones.
"We found that one growth ring was definitely deposited every year," said Dr. Mark Meekan of the Australian Institute of Marine Science in Perth, a co-lead on the study. "This is very important, because if you over- or under-estimate growth rates you will inevitably end up with a management strategy that doesn't work, and you'll see the population crash." This means the sharks used in this study were around 35 and 50 years old at the time of their deaths.
Working forward from there, the scientists were able conclude that the animals may have an age range of 100-150 years. "Earlier modelling studies have suggested that the largest whale sharks may live as long as 100 years," Dr. Meekan explained in a statement. "However, although our understanding of the movements, behaviour, connectivity and distribution of whale sharks have improved dramatically over the last 10 years, basic life history traits such as age, longevity and mortality remain largely unknown. Our study shows that adult sharks can indeed attain great age and that long lifespans are probably a feature of the species. Now we have another piece of the jigsaw added."
Whale sharks are an interesting species that many eco-tourists want to see. Conservation efforts for them rely on having accurate data on their longevity, mortality rate, and the age of specific animals. This information will help those managing ocean preserves keep the population stable for future generations to enjoy.
The idyllic islands of the Pacific Ocean typically have little role to play in the wider world aside from offering white shores and blue oceans that come about as close to paradise as it gets. But in World War II, these islands were bloodily contested. They represented strategic positions for the Allies, who could establish bases for bombing raids on the then-Axis Japan. In turn, Japanese soldiers were sent to these islands to defend them at all costs. Many, including a lieutenant named Hiroo Onada, were instructed to fight until killed; surrender was not an option. Hiroo Onada and others obeyed these orders literally. In fact, Onada continued to fight for 29 years after World War II ended.
Twentieth-century Japan had transformed the ancient concept of Bushido — a military code of conduct presented in some texts as "a way of dying" that demanded samurai be prepared to lay their life down for their lords — into a full-on propaganda tool to stir up nationalism and a culture of death before surrender. Surrender was so anathema to World War II Japan that Emperor Hirohito's surrender speech did not even feature the word "surrender." Instead, he characterized the coming capitulation as "enduring the unendurable and suffering the unsufferable."
This attitude led Lieutenant Onada and his men to go into hiding on the mountains of Lubang Island in the Philippines after Allied forces took the island back from Japanese control in February of 1945. Major Yoshimi Taniguchi was evacuating the island with other Japanese soldiers but instructed Onada and other men to stay and fight. "It may take three years, it may take five, but whatever happens we'll come back for you," the major said. "As an intelligence officer," said Onada, "I was ordered to conduct guerrilla warfare and not to die. I had to follow my orders as I was a soldier." The war ended in September of that year, but Onada continued to follow his orders.
During his time in the jungle, Onada engaged in guerilla warfare and several skirmishes with the local Filipinos and police. In October of 1945, he and his team found a leaflet that a villager had left. It read: "The war ended on August 15. Come down from the mountains!" Later that year, more leaflets came, but Onada and his men believed them to be American propaganda. They were full of mistakes, he said, and so they could not have come from the Japanese. And how could the Japanese have surrendered, anyway? So, they stayed in the jungle for 29 years.
Hiroo Onoda presenting his sword to the Philippine President Ferdinand Marcos. Image source: Wikimedia Commons
The holdouts continued to fight local Filipino police and others, who fought back in self-defense. The continued engagement was taken as a sign that the war was still on. One of Onada's men eventually surrendered in 1950. Another was killed by a search party in 1954 looking for the group. After burning a field of rice in 1972 as part of their guerilla war, police killed Onada's last companion. Now, he was alone in the jungle.
But back in Japan, Onada and his men had become something of an urban legend. Although he had been declared legally dead by Japan, the holdout's presence on the island was almost certain; after all, he had been engaged in guerilla warfare for nearly 30 years and had killed 30 Filipinos after the war had ended. So, in February of 1974, a college dropout named Norio Suzuki decided to go look for him. "[I'm] going to look for Lieutenant Onoda, a panda, and the abominable snowman, in that order," he told his friends.
Surprisingly, Suzuki did find Onada, but the lieutenant still refused to surrender. Onada would only surrender were he ordered to do so by his commanding officer: Major Yoshimi Taniguchi.
Suzuki returned to Japan and tracked down Taniguchi, by then an old man and a bookseller. He brought him back to Lubang to meet with Onada. Twenty-nine years after the end of World War II, Taniguchi relieved Onada of his duty. Before he left for Japan, however, Onada gave the Philippine President Ferdinand Marcos his sword in surrender — Marcos returned the sword and pardoned Onada for his actions during what Onada had believed to be wartime.
Onada was given a hero's welcome in Japan in testament to what is either his incredible discipline or fanaticism. The island nation had changed drastically since he was gone, changes that Onada couldn't entirely come to grips with. In 1975, Onada retired to Brazil to raise cattle, later returning to Japan in 1984 to start a wilderness survival school.
