June 17, 2019
The animal kingdom is exciting, majestic, and mysterious. It also teaches us many useful things that can help to prolong our existence and improve our quality of life. Today, we have two very fascinating stories about mantis shrimp and hawks and how that are helping the scientific community with tracking strategies and impact-resistant materials.
Learn about this and more interesting stories from the scientific community in today's issue.
*-- Study of hawks' pursuit of prey could help scientists capture rogue drones --*
The tracking strategy utilized by hawks could be used to capture rogue drones, according to a new study.
Falcons track their prey a lot like a heat-seeking missiles honing in on a target -- they follow a streamlined trajectory, capturing airborne prey. But hawks must navigate more crowded environs and follow small targets that zig and zag across the ground.
Researchers at the University of Oxford wanted to decipher the guidance law that helps hawks track the erratic escape maneuvers of squirrels and field mice.
A guidance law informs an animal, missile, aircraft or other tracking device on how to move and turn to intercept its target.
"In a pursuit, [the guidance law] might say 'turn at a rate that depends on how far off center your target is' or 'turn at a rate that depends on how quickly the bearing to your target is drifting,'" Graham Taylor, a professor of zoology at Oxford, told UPI. "A missile would typically use the second of these guidance laws, and we previously found the same uncannily missile-like behavior in peregrine falcons."
To find out how a hawk's guidance system operates, scientists set up a system of high-speed cameras and filmed five captive-bred Harris' hawks chasing a prey-like target programmed to move unpredictably across the ground.
Video reconstruction techniques helped scientists translate the film footage into a 3D model, revealing the hawks' flight patterns.
"Working forward from the start of the attack, we used a computer simulation to predict how the hawk would have turned under a range of different guidance laws, and identified which gave the best model of the data," Taylor said.
The analysis showed the Harris hawk's tracking ability is dictated by a mix of two guidance laws. The bird's turns are guided by the angle between the direction to its target and their current flight direction, as well as the rate at which the direction to its target is changing.
According to Taylor, natural selection led to the hawk's adoption of guidance laws that are better suited for hunting in a cluttered environment and tracking targets at close range.
The finding, published this week in the journal Nature Communications, could have implications for drone technologies.
"Part of our motivation for studying how hawks intercept targets was to find out how aerial hunters achieve the same functionality -- being able to grab a maneuvering target in a cluttered environment -- as technology requires to make a successful anti-drone drone," Taylor said. "In fact, the main grant that sponsors this work is on visually based guidance in birds and its applications to autonomous air systems."
Taylor and his colleagues are currently working with engineers and industry partners to develop drone interception technologies, and their latest prototype features wings that can change shape like a bird's wings.
*-- Mantis shrimp shield inspires lightweight, impact-resistant materials --*
 The evolutionary engineering of the mantis shrimp is inspiring a new class of lightweight, impact-resistant materials.
Some mantis shrimp species, called smashers, have a club-like arm capable of cracking clam shells. It can also be used as a weapon against rival shrimp.
Smashers live in coral reef cavities, and competition for prime real estate is fierce. To protect themselves from their peers, mantis shrimp have evolved an impressive shield built into their tail. The defensive component is called a telson.
To better understand the telson's defensive capabilities scientists modeled and tested both the shield's macro-scale architecture as well as its internal micro-scale structures. Their analysis showed the telson's helicoidal structure works to absorb energy and prevent cracks from forming and spreading.
Scientists likened the structure to braided plywood. It is the same structure scientists previously identified in the club-like arm of smashers.
"For over a decade, we have been studying the dactyl club of the smashing type of mantis shrimp," engineer David Kisailus, a professor at the University of California, Riverside, said in a news release. "We realized that if these organisms were striking each other with such incredible forces, the telson must be architected in such a way to act like the perfect shield."
There's always a limit to how much an animal can bulk up its defensive components. The shield can't be so heavy that it can't be quickly and effectively deployed.
"Having access to one the most efficient materials architectures, such as the helicoid, in conjunction with a clever geometry, makes this another winner solution found by nature," said Pablo Zavattieri, a professor of engineering at Purdue University.
The telson's helicoidal structure is accompanied by a series of curved ridges. Tests showed the structures, called carinae, also help absorb and dissipate energy.
"When we observed the carinae, it was obvious that they stiffened the telson along its long axis," Kisailus said. "However, we found that the carinae also allowed the telson to flex inward when forces were applied perpendicular to its long axis. This enabled us to discover the non-obvious function of these ridges, which was to absorb significant amounts of energy during a strike. Pablo's models then validated our hypotheses."
Scientists are currently working on using their discoveries -- described this week in the journal Advanced Functional Materials -- to develop impact-resistant materials that can be used in helmets, cars and other products.
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