The Sharp Science of Animal Strikes


Chance may favor the prepared, but nature favors the zippy. A group of scientists have studied how animals great and small manage to strike and puncture their often well-protected prey, and they reported their findings in the journal Interface Focus.

The action of striking and piercing an object or another creature is more complex than it looks, and each pouncing animal has its own technique. Snakes lunge and bite to inject venom, while zebra mantis shrimp (which are not zebras, mantises, or shrimp) spear their prey with a harpoon-like claw. For trapjaw ants, the action is all in the mandibles, which can slam shut at up to 145 miles per hour. Jellyfish and the Portuguese man-of-war strike at a microscopic level using itsy-bitsy stinging missile-launchers called nematocysts.

These attack styles may look very different, but study co-author Phillip Anderson of the University of Illinois suspected that the underlying mechanics had a lot in common. "What's really cool from the evolutionary point of view is that it's not often that you have the ability to look at biomechanical systems across such a wide range of animals that are all trying to achieve a similar performance," he said in a press statement. But instead of studying the animals themselves, Anderson picked up a crossbow and aimed it at ballistic gelatin.

Forensic experts generally use ballistic gelatin to test the action of various guns. The squishy, resilient gelatin is a decent stand-in for human and other animal tissue. But Anderson and his colleagues decided it would be equally useful to test punctures made by a bolt. They fired a single bolt into a 4-inch cube of gelatin again and again, adding weight to the bolt between each test.

Video: Philip Anderson

At certain weights, the bolt pierced with no trouble. At others, it made a partial puncture before the gelatin spit it back out. "The target material builds up elastic energy as it deforms,” Anderson said. “At a certain point the elastic energy in the material causes it to push back against the arrow. If the elastic energy is large enough, it can eject the arrow.”

Because the researchers knew the velocity and mass of each test run, they were able to calculate the effects of varying amounts of kinetic energy on the gelatin. They found that the more kinetic energy the bolt had, the more successful it was at puncturing the gelatin. But heavier bolts weren’t better off: It was velocity, not mass, that increased the bolt’s kinetic energy.

"This means that one potential way for small animals to puncture and get through tough materials, even with a low mass, is to increase their speed," Anderson said. "And if you look across animals that puncture, it appears that the smaller ones tend to be faster."

Check out this cool infographic about their findings for more details:

Image credit: Julie McMahon
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]


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