Drew J, Philipp C, Westneat MW (2013)
Drew J, Philipp C, Westneat MW (2013)

How Ancient Shark-Tooth Swords Uncovered Two Long-Lost Species

Drew J, Philipp C, Westneat MW (2013)
Drew J, Philipp C, Westneat MW (2013)

By Chris Gayomali

Biologist Joshua Drew's surprise discovery began as many do: "I just wanted to... look at really cool stuff," he tells The Los Angeles Times. Drew, now a postdoctoral researcher at Columbia University, was with a few colleagues at the Field Museum of Natural History in Chicago scoping out a new exhibit — a collection of "badass" swords, knives, and lances once used by the inhabitants of the Central Pacific's Gilbert Islands 130 years ago to rip their enemies to shreds.

This particular arsenal wasn't pounded out of iron or steel, though. The 124 flesh-tearing weapons on display had a more biological origin, and were carved out of wood, with each blade edge carefully outfitted with rows of dagger-like shark teeth. 

Drew was admiring the pieces when he noticed something strange: A few of the teeth appeared to belong to dusky and spottail sharks, which, oddly, aren't typically found near the Gilbert Isles. How could he tell, you might ask? Well, he was in a natural history museum, and could easily look up fossil records to confirm his suspicions.

"Shape, serration patterns, and other features of shark teeth were enough for researchers to identify the species," says LiveScience.

Using field guides and the museum's collections of shark jaws, the researchers identified teeth from eight species of shark on 122 weapons and teeth collections from the Gilbert Islands. The most common of those species was the silvertip shark (C. albimarginatus), whose teeth graced 34 weapons. Gilbert Islands weapon-makers also used teeth from silky sharks, oceanic whitetip sharks, tiger sharks, blue sharks, and hammerheads. [Live Science]

Yet, a deep-dive through history revealed no evidence that the dusky and spottail sharks had ever lived in Gilbert Island's reefs. While trading with other far-away cultures could explain how the teeth got there, the likelier answer is one we've already heard before:

"Probably, they were fished out," says Drew. Although it's not clear why the sharks disappeared,says Ed Yong at National Geographic — "people were hacking off shark fins in the Gilbert Islands as far back as 1910 and by the 1950s, around 3,000 kilograms of fins were being shipped from the islands every year." It's become so bad that some conservationists estimate that 100 million sharks are killed worldwide every year

After publishing their findings this month in the journal PLoS One, Drew and his team hope that the discovery of a "shadow biodiversity" along the Gilbert Islands' waters will aid conservation efforts for marine animals that have been over-fished for decades:

Given the importance of these species to the ecology of the Gilbert Island reefs and to the culture of the Gilbertese people, documenting these shifts in baseline fauna represents an important step toward restoring the vivid splendor of both ecological and cultural diversity. [PLoS One]

That's something worth sinking your teeth into.

More from The Week...

Watch: A Massive Black Hole Devours a Super-Jupiter


10 Expensive Items of Beatles Memorabilia Sold at Auction


Did Scientists Just Find Dark Matter? Signs Point to Yes

Whale Sharks Can Live for More Than a Century, Study Finds

Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.

There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]


More from mental floss studios