Julius Nziza still remembers the moment vividly. Just before dawn on a chilly January morning in 2019, he and his team gently extracted a tiny brown bat from a net purposely strung to catch the nocturnal fliers. A moment later, the researchers’ whoops and hollers pierced the heavy mist blanketing Rwanda’s Nyungwe National Park. The team had just laid eyes on a Hill’s horseshoe bat (Rhinolophus hilli), which scientists hadn’t seen for nearly four decades.

Nziza, a wildlife veterinarian at Gorilla Doctors in Musanze, Rwanda, and a self-described “bat champion,” had been looking for the critically endangered R. hilli since 2013. For several years, Nziza and Paul Webala from Maasai Mara University in Narok, Kenya, with the help of Nyungwe park rangers, surveyed the forest for spots where the bats might frequent. They didn’t find R. hilli, but it helped them narrow where to keep looking.

In 2019, the team decided to concentrate on roughly four square kilometers in a high-elevation region of the forest where R. hilli had last been spotted in 1981. Accompanied by an international team of researchers, Nziza and Webala set out for a 10-day expedition in search of the elusive bat. It wasn’t rainy season yet, but the weather was already starting to turn. “It was very, very, very cold,” Nziza recalls.
Every night, from sunset until close to midnight, the researchers stretched nets across trails, where bats are most likely to fly, and kept watch. Then, after a few hours of rest, they woke early to check the traps again. It was cold enough that the bats could die if stuck too long.

At 4 a.m. on the fourth day, the researchers caught a bat with the distinctive horseshoe-shaped nose of all horseshoe bat species. But it looked slightly different from others they had captured. This one had darker fur and a pointed tip on its nose.

Everyone began shouting: “This is it!”
The researchers felt “almost 99 percent sure” they had found the lost bat. “We had a couple beers in the evening,” Nziza says. “It was worth celebration.” To be 100 percent sure, though, the team needed to compare its specimen to past ones of R. hilli. Fortunately, there were two in museums in Europe.

That’s because this isn’t the first time that R. hilli was lost, then found, to science. Victor van Cakenberghe, a retired taxonomist at the University of Antwerp in Belgium, rediscovered R. hilli 17 years after it was first seen in 1964. He says he still remembers finding the bat tangled in a mist net strung across a river. He kept the specimen and brought it back to a Belgian museum.

Nearly 40 years later, Nziza and colleagues compared the measurements of their bat, which was released into the wild, to the preserved bat. At long last, it can be confidently said that R. hilli was rediscovered again, researchers report March 11 in a preprint submitted to Biodiversity Data Journal.

And, for the first time ever, the scientists recorded R. hilli’s echolocation call. Now, the rangers can use acoustic detectors to keep an eye — or rather, an ear — on the bat (SN: 10/23/20). In nine months, they’ve already captured R. hilli calls from eight different locations in the same small area.
The team published its data to the open-access Global Biodiversity Information Facility in hopes of speeding up conservation efforts for the bat. Africa is home to over 20 percent of the world’s bats, but with a longstanding research focus on bats in Europe and the Americas, little is known about African bat species.

“It’s a whole new thing,” Nziza says. “That’s why everybody’s excited.”

You can never have too much ice cream, but you can have too much ice in your ice cream. Adding plant-based nanocrystals to the frozen treat could help solve that problem, researchers reported March 20 at the American Chemical Society spring meeting in San Diego.

Ice cream contains tiny ice crystals that grow bigger when natural temperature fluctuations in the freezer cause them to melt and recrystallize. Stabilizers in ice cream — typically guar gum or locust bean gum — help inhibit crystal growth, but don’t completely stop it. And once ice crystals hit 50 micrometers in diameter, ice cream takes on an unpleasant, coarse, grainy texture.

Cellulose nanocrystals, or CNCs, which are derived from wood pulp, have properties similar to the gums, says Tao Wu, a food scientist at the University of Tennessee in Knoxville. They also share similarities with antifreeze proteins, produced by some animals to help them survive subzero temperatures. Antifreeze proteins work by binding to the surface of ice crystals, inhibiting growth more effectively than gums — but they are also extremely expensive. CNCs might work similarly to antifreeze proteins but at a fraction of the cost, Wu and his colleagues thought.

An experiment with a sucrose solution — a simplified ice cream proxy — and CNCs showed that after 24 hours, the ice crystals completely stopped growing. A week later, the ice crystals remained at 25 micrometers, well beneath the threshold of ice crystal crunchiness. In a similar experiment with guar gum, ice crystals grew to 50 micrometers in just three days.
“That by itself suggests that nanocrystals are a lot more potent than the gums,” says Richard Hartel, a food engineer at the University of Wisconsin–Madison, who was not involved in the research. If CNCs do function the same way as antifreeze proteins, they’re a promising alternative to current stabilizers, he says. But that still needs to be proven.

Until that happens, you continue to have a good excuse to eat your ice cream quickly: You wouldn’t want large ice crystals to form, after all.