Bioinspired fake rhino horns poised to disrupt black market

Scientists believe that they have found a way to protect endangered rhinos from poachers across the globe. By designing convincingly realistic, fake rhino horns, they could potentially disrupt the black market sale of the real thing.

Rhinos once freely roamed Asia, Africa and Europe. At the start of the 20th century, over 500,000 rhinos lived in the wild. But their population has been decimated and their genetic diversity has been significantly weakened. According to a 2018 State of the Rhino report from the International Rhino Foundation, only 29,500 exist today—and that’s after significant conservation efforts.

Like other animals, rhinos have faced challenges from habitat loss as wilderness is cleared for agriculture. But rhinos have been targeted by poachers for their prized horns, which are actually more similar to a very tough sprout of nose hair, at alarming rates. Since 2013, the IRF’s report says, approximately three rhinos have been killed a day by poachers. In 2017, criminal networks based in Africa killed over 1,100 rhinos. The Sumatran rhino, one of only five species left in the world, has seen its numbers reduced to 80.

While other horn fakes do exist on the black market, a research team from the University of Oxford sought to design a horn that would not only look and feel like the real thing but would have similar material properties as well. The more convincing, they hope, the easier it is to flood and fool black market buyers.

The research was published Friday in the journal Scientific Reports and describes an approach in which scientists used horsehair and a silk-based organic filler to create the thick, tightly packed structure that they were able to shape into a convincing horn-like shape. The researchers were excited to find that their fake horn not only looked similar to the real thing, but that a closer investigation of its properties showed that it was mechanically and thermodynamically similar as well.

The researchers found that their fake horn both took a similar amount of time to heat and reacted to heat similarly as well, with both the silk-based and the natural protein of the horn beginning to degrade around 200 to 400 degrees Celsius (392 - 752 degrees Fahrenheit.) The researchers write that this discovery is important because it allows them a better look at how these materials might react during phase changes, such as between solid and liquid, which can be an important characteristic to mimic if horns are ground for consumption or medicine.

Another important characteristic the team was pleased to find similarities with were the mechanical properties of their horn, namely how it responded to forces exerted upon it. Wild, rhinos’ horns need to withstand a myriad of forces without succumbing to cracks or damage, and the researchers found that under similar lab-induced conditions their horn performed very similarly to real horns.

In the study, the researchers write that this unique property of rhino horns is a result of how these stiff hairs react in a more pliable resin.

“The fibers break before they bend while the matrix bends before it breaks,” the researchers write in the study. “The result is a composite that is able to withstand greater loads than either of its parts. When a stress is applied to the material, the matrix inhibits crack propagation and redistributes stress in the direction of the filaments.”

Part of the material success of this artificial horn, particularly when it comes to the mechanical similarities, is its ability to mimic outward and internal appearances. Comparing a cross-section of the artificial horn with a real sample, researchers observed that the pattern created by the densely packed horsehairs and silk-protein very closely resembled that of the real horn.

In addition to hopefully being able to fool black market purchasers into believing their horn is a real rhino’s “extravagantly expensive tuft of nose hair,” researchers also write that they believe the unique biomaterial approach discovered here through mimicking a rhino’s horn may lend itself to other applications as well.

If further research were to follow this path it certainly wouldn’t be the first time science has borrowed from nature. Bio-mimickery has always been a mainstay of science and has popped up recently in the form of “artificial leaves,” bounding robot dogs, and disinfecting shark-like plastic. More support for the old adage: if it isn’t broken, why fix it?

Abstract

Demand for rhino horn is driving poaching with devastating effect for the few individuals left of the few species surviving from this once numerous, widespread and cosmopolitan clade of pachyderms. We bundled together tail hairs of the rhino’s ubiquitous near relative, the horse, to be glued together with a bespoke matrix of regenerated silk mimicking the collagenous component of the real horn. This approach allowed us to fabricate composite structures that were confusingly similar to real rhino horn in look, feel and properties. Spectral and thermal FT-IR, DSC and TGA analysis demonstrated the similar chemical composition and thermo-mechanical properties between the natural and the faux horns.