from the world's big
The ocean's largest shark relies on vision more than previously believed.
- Japanese researchers discovered that the whale shark has "tiny teeth"—dermal denticles—protecting its eyes from abrasion.
- They also found the shark is able to retract its eyeball into the eye socket.
- Their research confirms that this giant fish relies on vision more than previously believed.
A. Anterior view of the whale shark, showing the locations of the eye (arrows). Note that whale shark eye is well projected from the orbit. Photo was taken in the sea near Saint Helena Island. B. Close-up view of the left eye of a captive whale shark (Specimen A).<p>Considering their dietary habits, vision was not thought be that important for whale sharks. This species is unique for not having any sort of eyelid or protective mechanism—until now, that is. Not only do dermal denticles protect their vision, the team, led by Taketeru Tomita, discovered that whale sharks have another trick:</p><p style="margin-left: 20px;">"We also demonstrate that the whale shark has a strong ability to retract the eyeball into the eye socket."</p><p>The researchers studied these massive sharks in an aquarium, offering them a rare look at one of the ocean's largest fish (They also studied deceased sharks). The eye denticle is different from the rest of the scales covering their body: they are designed for abrasion resistance, not ocean stealth. </p><p style="margin-left: 20px;">"The covering of the eye surface with denticles in the whale shark is probably useful in reducing the risk of mechanical damage to the eye surface." </p><p>Despite their massive size, whale sharks have relatively small eyes, measuring less than 1 percent of their total length. Their brain's visual center is also relatively small. With this discovery, the researchers realized vision plays a more important role than previously assumed. </p><p style="margin-left: 20px;">"The highly protected features of the whale shark eye, in contrast to the traditional view, seems to suggest the importance of vision in this species. Interestingly, Martin showed that whale shark eyes actively track divers swimming 3–5 m away from the animal, suggesting that vision of the whale shark plays an important role in short-range perception." </p><p>While you likely won't bump into a whale shark while swimming just off the coast, this is yet another reminder of how species adapt to their environment. </p><p><span></span>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a>, <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank">Facebook</a> and <a href="https://derekberes.substack.com/" target="_blank">Substack</a>. His next book is</em> "<em>Hero's Dose: The Case For Psychedelics in Ritual and Therapy."</em></p>
Batrachopus grandis, an ancient crocodylomorph, may have chased down land prey on its own two feet.
Walking the walk<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM5MjIyOS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwMDM5NDYxN30.vSptOKk7U7Vi6UGUrVSrlDZDA0KE27a4Hi506qS7_MQ/img.jpg?width=1245&coordinates=0%2C0%2C145%2C0&height=700" id="4984d" class="rm-shortcode" data-rm-shortcode-id="ca91bf364c9dcf5752919b5105bbcb2f" data-rm-shortcode-name="rebelmouse-image" alt="A photograph of Batrachopus grandis track impressions found at Jinju Formation." />
A photograph of Batrachopus grandis track impressions found at Jinju Formation.
An evolving understanding<div class="rm-shortcode" data-media_id="bM8XiiEp" data-player_id="FvQKszTI" data-rm-shortcode-id="217e12c49e7fd202232637b5487313ba"> <div id="botr_bM8XiiEp_FvQKszTI_div" class="jwplayer-media" data-jwplayer-video-src="https://content.jwplatform.com/players/bM8XiiEp-FvQKszTI.js"> <img src="https://cdn.jwplayer.com/thumbs/bM8XiiEp-1920.jpg" class="jwplayer-media-preview" /> </div> <script src="https://content.jwplatform.com/players/bM8XiiEp-FvQKszTI.js"></script> </div> <p>For now, the only evidence for <em>Batrachopus grandis</em> exists in the footprints, so there's still much to learn about it. In the study, the researchers note the possibility that this crocodylomorph didn't take to the land but used its hind legs to propel itself through waterways.</p><p>Not all paleontologists agree with the study's conclusions. Phil Manning, a paleontologist at the University of Manchester, who was not part of the research, <a href="https://www.bbc.com/news/science-environment-53011567" target="_blank">told the BBC</a><u> </u>he found the trace fossils interesting but didn't think a crocodilian was capable of producing them.</p><p>"Look at any videos of living crocs and the rotation of their feet when they're galloping: it's outwards, not inwards towards the midline of the trackway. Just from their orientation, it looks more like some kind of dinosaurian track-maker to me. But whether it's a croc - unfortunately, we just don't have the fossil bones to tell us," he said.</p>
Plenty of crocs in the fossilized sea<p>If you had your heart set on a land-roaming, bipedal crocodile, don't be disappointed. The ancient world was filled with enough strange and eerie crocodylomorphs to fill many a nightmarish menagerie.</p><p>In 2015, for example, paleontologists discovered a crocodile relative in North Carolina. This 9-foot-long apex predator also walked on two feet and ruled its Pangaean stomping grounds until the Triassic-Jurassic extinction event ended its reign. Paleontologists christened this species <em>Carnufex carolinensis</em>, or the "<a href="https://www.pbs.org/newshour/science/newly-discovered-bipedal-crocodile-ancestor-terrorized-pre-dinosaur-world" target="_blank">Carolina Butcher</a>."</p><p>There's also evidence for crocodiles that <a href="https://www.youtube.com/watch?v=qruxOVmSfyY" target="_blank">snatched sauropods from the water's edge</a>, crocodiles that bounded through ancient forests <a href="https://www.youtube.com/watch?v=QmdcewIjXi0" target="_blank">on hooves</a>, and crocodiles that enjoyed <a href="https://www.smithsonianmag.com/smart-news/ancient-crocodiles-would-have-ordered-salad-180972518/" target="_blank">leafy flexitarian diets</a>. Even their modern relatives continue to surprise us, such as their <a href="https://www.wired.com/2014/02/crocodiles-can-climb-trees/" target="_blank">surprisingly agile tree-climbing abilities</a>.</p><p>So while these ancient creatures may be extinct, they continue to evolve in our imaginations. We'll have to see what science has in store for <em>Batrachopus grandis</em> as we discover more about it. </p>
Scientists are befuddled by where the shark gets most of its food.
- A University of Sydney research team found that the great white shark spends an unexpectedly large amount of time feeding close to the sea bed.
- The group examined the contents in the stomachs of 40 juvenile white sharks and found the remains of a variety of fish species that typically inhabit the sea floor or are buried in the sand.
- The scientists hope that the information gained from this research will assist conservation and management efforts for the species.
Fresh findings<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM5MjMyNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwNjY5NDExM30.3JLqvvn4iB0F29jWuRMnEdmSwY6avTsmo6AP3LgXMxQ/img.jpg?width=1245&coordinates=0%2C333%2C0%2C334&height=700" id="362cb" class="rm-shortcode" data-rm-shortcode-id="f21b84cc3825bf4ac53454c6c4bbb09f" data-rm-shortcode-name="rebelmouse-image" />black shark in blue waterPhoto by Gerald Schömbs on Unsplash<p>A research team from the University of Sydney looked at sharks off the east coast of Australia and found that in their stomachs were remains from a variety of fish species that typically inhabit the sea floor or are buried in the sand. Specifically, the group examined the contents in the stomachs of 40 juvenile white sharks, scientifically known as <em>Carcharodon carcharias</em>, who were caught in the NSW Shark Meshing Program. </p><p>"This indicates the sharks must spend a good portion of their time foraging just above the seabed," explained lead author Richard Grainger, a Ph.D. candidate at the Charles Perkins Centre and School of Life and Environmental Sciences at the University of Sydney, <a href="https://phys.org/news/2020-06-great-white-shark-diet-scientists.html" target="_blank">in a press release</a>. "The stereotype of a shark's dorsal fin above the surface as it hunts is probably not a very accurate picture." </p><p>The study was published on June 8, World Oceans Day, in the journal Frontiers in Marine Science<em>. </em>It's an important step forward for scientists trying to better understand the great white's diet and migratory behavior. </p><p>"We discovered that although mid-water fish, especially eastern Australian salmon, were the predominant prey for juvenile white sharks in NSW, stomach contents highlighted that these sharks also feed at or near the seabed," <a href="https://phys.org/news/2020-06-great-white-shark-diet-scientists.html" target="_blank">said Vic Peddemors</a>, Ph.D., a co-author from the NSW Department of Primary Industries (Fisheries). </p><p>The research team compared this new dietary information with published data on great white feeding habits from other parts of the world where the sharks make home, mostly South Africa. From there they were able to establish a nutritional framework for the species. </p>
What's in a great white's diet?<p><a href="https://www.frontiersin.org/files/Articles/532445/fmars-07-00422-HTML/image_m/fmars-07-00422-t001.jpg" target="_blank">According to the research</a>, the juvenile great white sharks' diets relied primarily on pelagic — mid-water ocean swimming — fish, such as Australian salmon. This made up 32.2 percent of the shark's diet. Bottom-dwelling fish like stargazers, sole or flathead made up 17.4 percent; batoid fish such as stingrays 14.9 percent; and reef fish, like eastern blue gropers, 5 percent.</p><p>The remaining species eaten by the sharks were unidentified fish or less abundant prey. Grainger pointed out that other marine mammals, sharks, and cephalopods — squid and cuttlefish — were eaten at lower rates. </p><p>"The hunting of bigger prey, including other sharks and marine mammals such as dolphins, is not likely to happen until the sharks reach about 2.2 meters in length," <a href="https://phys.org/news/2020-06-great-white-shark-diet-scientists.html" target="_blank">Grainger said</a>.</p><p>Another discovery was that bigger sharks tended to have diets that were higher in fat. Similarly to other animals, this is likely an adaptation to their higher energy needs for migration. Great white's migrate seasonally along Australia's east coast, traveling from southern Queensland to northern Tasmania. The range of distance covered increases with age. </p><p>"This fits with a lot of other research we've done showing that wild animals, including predators, select diets precisely balanced to meet their nutrient needs," said co-author Professor David Raubenheimer, Chair of Nutritional Ecology in the School of Life and Environmental Sciences.</p>
Species conservation and management<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="7bb54774f7a5b923690ad15c2e979aca"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/O2FInaOCqoo?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Ultimately, the scientists hope that the information gained from this research will assist conservation and management efforts for the sharks, who are considered a vulnerable and declining species due to overfishing and accidental catching in gill nets.</p>Of particular interest to scientists is better management of relations between humans and great whites. According to <a href="https://www.nationalgeographic.com/animals/fish/g/great-white-shark/" target="_blank">National Geographic</a>, of the over 100 annual shark attacks that happen worldwide, a whopping one-third to half can be attributed to great whites. Yet, research has found that the sharks, who tend to have a curious disposition, are often just taking sample nibble before releasing their human prey. So, at least we know humans aren't a great white delicacy.
A new study finds surprising evidence of the self-evolution of urban foxes.
- A study from the University of Glasgow finds urban foxes evolved differently compared to rural foxes.
- The skulls of the urban foxes are adapted to scavenging for food rather than hunting it.
- The evolutionary changes correspond to Charles Darwin's "domestication syndrome."
How much can living in the city change you? If you were an urban fox, you could be evolving yourself to a whole new stage and becoming more like a dog, according to a fascinating new study.
Researchers compared skulls from rural foxes around London with foxes who lived inside the city and found important variations. Rural foxes showed adaptation for speed and hunting after quick, small prey, while urban fox skulls exhibited changes that made it easier for them to scavenge, looking through human refuse for food, rather than chasing it. Their snouts were shorter and stronger, making it easier to open packages and chew up leftovers. They also have smaller brains, not meant for hunting but for interacting with stationary food sources, reports Science magazine.
Interestingly, there was much similarity found between the male and female skulls of the urban foxes.
The observed changes correspond to what Charles Darwin called the "domestication syndrome," comprised of traits that go along with an animal's transition from being wild, to tamed, to domesticated.
The study was led by Kevin Parsons, an evolutionary biologist at the University of Glasgow.
"What's really fascinating here is that the foxes are doing this to themselves," Parsons told the BBC. "This is the result of foxes that have decided to live near people, showing these traits that make them look more like domesticated animals."
The researchers are not suggesting you should go out and get a fox as a house-pet just yet. But they are seeing the evolutionary process taking place that's moving the urban foxes along the path towards becoming more like dogs and cats, explained the study's co-author Dr. Andrew Kitchener from National Museums Scotland.
A fox beneath a tree in Greenwich park, south east London on May 14, 2020.
Photo by Glyn KIRK / AFP
"Some of the basic environmental aspects that may have occurred during the initial phases of domestication for our current pets, like dogs and cats, were probably similar to the conditions in which our urban foxes and other urban animals are living today," said Kitchener. "So, adapting to life around humans actually primes some animals for domestication."
The specimen came from the National Museum Scotland's collection of around 1,500 fox skulls.
You can read the study in the Proceedings of the Royal Society B.
A fox at the LV County Championship, Division two match between Surrey and Derbyshire at The Brit Oval on April 9, 2010 in London, England.
Photo by Clive Rose/Getty Images
While building a new airport, construction crews uncover a gigantic collection of ancient bones.
- During digging for a new airport in Mexico, workers came across three sites containing the remains of mammoths, as well as some pre-Spanish human burial sites.
- It's unclear why the mammoths were all found in this one spot, though it may have to do with an ancient lake.
- Retrieving this massive sample will likely give experts new insights into a long-lost North American pachyderm.
In the Mexico Basin about 45 miles north of Mexico City in the Santa Lucía region, the new Felipe Ángeles Airport is under construction. According to Mexico's National Institute of Anthropology and History (INAH), workers there have dug up a massive surprise: a trove of 60 ice-age mammoth skeletons. They've also unearthed 15 pre-Hispanic human burial sites.
Image source: Sergiodlarosa/wikimedia
The pachyderm bones belong to Colombian mammoths, Mammuthus columbi, who last lived in North America in the Pleistocene epoch between 2.6 million and 13,000 years ago, when they are believed to have become extinct. They're the mammoths that visitors to Los Angeles' La Brea Tar Pits encounter. (No woolly mammoth remains were found in Santa Lucía.)
It's not yet known how many of the mammoth skeletons are complete. It is clear, though, that males, females, and their young are there. The bones are being found between 80 centimeters and 2.5 meters below the surface and spread across three exploration areas. First discovered in October 2019, the digs are still being stabilized and undergoing analysis and classification, according to INAH National Coordinator of Archaeology, Pedro Francisco Sánchez Nava.
How 60 mammoths wound up together in death at this location is an interesting question. No signs of human tracks leading to or from the site are evident nor have any indications of hunter accommodations have been found. By contrast, the prehistoric mammoth hunting site discovered in the Mexican municipality of Tultepec in November 2019 does exhibit such signs of human interaction.
Archaeologists suspect the 60 mammoths got stuck in a muddy swamp over time — the site is near the shores of the former Lake Xaltocan. Researchers say the most complete skeletons found are those close to the former lake's shoreline. It remains possible that the immobilized mammoths were then preyed upon by hunters even without clear evidence of that so far.
Once the remains are retrieved, they'll be studied by a team of 30 archaeologists, supported by a trio of restorers, to make a full account of what's been found. They hope to learn more about how and precisely when the animals lived, ate, and what health issues they may have had as evidenced in their skeletal remains.
An old home, a new home
Image source: Instituto Nacional de Antropología e Historia
Meanwhile, construction of the new airport continues. Says Salvador Pulido Méndez, director of INAH Archaeological Salvage, "So far, no findings have been recorded on the land that lead to the rethinking of the construction site, either totally or partially. Rather, the works have allowed INAH a research conjuncture in a space where, although it was known of the existence of skeletal remains, they had not had the opportunity to locate, recover and study them."
Prior to the beginning of construction, the Santa Lucía region had been used by the Santa Lucía Military Air Base, and the national defense organization Sedena has preserved its historic Santa Lucía hacienda, integrating it within the new airport. The various parties involved plan to create a museum within the hacienda that will allow visitors to learn about the Santa Lucía region and its amazing mammoth mammoth graveyard.