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Here Come The Giant Crime Sniffing Rats
Welcome back to the Abstract! Hope you had a Happy Halloween.
In honor of the week’s signature celebration of DEATH and FRIGHT, our main story is all about BATS, the unofficial avatar of spooky season. From there, we’ll meet a tadpole that is very old, very big, and very dead, and check in on the job market for rats interested in law enforcement.
To close out, we’ll look at one iteration of a timeless scientific question: what’s up with this weird thing? Enjoy!
Holy Acoustic Cognitive Maps, Batman!
Goldshtein, Aya et al “Acoustic cognitive map–based navigation in echolocating bats,” Science
Bats have been creeping people out for centuries. The Maya told tales of a “death bat” that served the underworld. The Celts associated them with mischief. The entire vampire genre was spawned by the namesake bat species that sucks blood from prey. It's no wonder that these often maligned animals have become one of the most ubiquitous symbols of Halloween.
Despite these heavy heapings of lore, the world according to bats is way trippier than anything we could make up about them. Case in point: Scientists now report that bats can navigate across large distances using solely echolocation, an adaptation that allows animals to orient themselves with sound waves. Though it is well known that bats use echolocation to avoid close-range hazards, the new study reveals that this superpower produces “acoustic cognitive maps,” which means they have whole sound-based landscapes locked away in their heads.
“Despite considerable research on echolocation, there is no direct evidence for the ability of bats to rely on echoes alone for kilometer-scale navigation,” said researchers led by Aya Goldshtein of the Max Planck Institute of Animal Behavior. “Using echolocation for such large-scale navigation is not straightforward. Echolocation is short ranged, allowing the detection of large objects from no more than tens of meters, which is much less than the range of vision, forcing a navigating bat to rely on proximal features when navigating.”
“It is also unclear to what extent bats can reconstruct the world in three dimensions using echolocation and, accordingly, to what extent they can use environmental echoes as landmarks for navigation,” the team continued. “This combination of limited range and possibly limited object identification ability makes the use of echolocation for navigation challenging, and it is uncertain whether and how bats do so. This challenge has been highlighted but has still not been resolved.”
Goldshtein and her colleagues set out to solve this mystery with a “translocation experiment.” They captured dozens of Kuhl's pipistrelle bats (Pipistrellus kuhlii) from their roost near Agamon Lake in Israel, and blindfolded some of them with eye covers. The bats were taken to locations about two miles away from their roost, where they were released and monitored with GPS trackers.
“Solving a translocation homing task first requires identifying the new translocated location and then flying toward a familiar destination,” the team said. “Our aim was to test whether a bat can solve this task acoustically (when deprived from non-acoustic sensory information)…Returning home successfully in a directional flight will only be possible if the bat holds some acoustic mental representation of its environment.”
As it turns out, bats do possess some kind of acoustic mental map, because 95 percent of the bats returned home successfully within a single night, including all of the blindfolded ones. After release, the bats spent a while meandering around, but they eventually transitioned to directed flights toward their target, suggesting that they used echolocation to find identifiable landmarks—road edges, riverbanks, and orchards—to guide them home.
“These small echolocating bats first identify their new location after translocation and then conduct directional flight home using environmental features that provide enough acoustic information to be distinguished as landmarks,” the researchers said. “This behavior also implies that they hold an acoustic mental map of their home range.”
It’s wild enough to imagine “seeing” in sound this way, but it’s even more mind-boggling that bats are able to construct large-scale three-dimensional topographies in those cute noggins. And while people often fear bats, this study goes to show that bats have a lot more to fear from us—even when our intentions are benign. I mean, can you imagine being kidnapped, blindfolded, and thrown out into some random new location? I would really love to read about this experiment from the bats’ POV.
Is that a Banana in Your Pocket, or Is It the Oldest Fossilized Tadpole?
Scientists have discovered the oldest known fossil of a tadpole, which died some 161 million years ago in the waters of Jurassic Patagonia. In addition to being by far the oldest known larval anuran (the term for frogs and toads), this tadpole was over six inches long, distinguishing it a gnarly example of “tadpole gigantism.”
“The exquisite preservation of the new specimen” which includes some soft tissues, “allows us to infer the mode of life and feeding habits” of this tadpole, which belonged to the species Notobatrachus degiustoi, said researchers led by Mariana Chuliver of Universidad Maimónides. “This finding has dual importance because it represents the oldest-known tadpole and, to our knowledge, the first stem-anuran larva.”
Image: Chuliver, Mariana et alThe team noted that the phenomenon of tadpole gigantism has evolved many times in the fossil record, and is perhaps best exhibited today by the paradoxical frog (Pseudis paradoxa) of South America. This species produces the world’s longest tadpoles—up to 11-inches!—that mature into totally normal-sized adult frogs, thus paradoxically growing by shrinking.
Here Come the Giant Rat Cops
The phrase “giant rats” doesn’t usually sound like the solution to anything. But scientists have proposed that the southern giant pouched rat (Cricetomys ansorgei), a rodent endemic to Africa, could help combat one of the most profitable and dangerous crime rings in the world—the illegal wildlife trade (IWT), which is linked to a host of scourges including animal abuse, biodiversity loss, and the spread of deadly pathogens.
“Rats have low training and maintenance costs, flexibly work with multiple handlers, have a long lifespan, and a sophisticated sense of smell,” said researchers co-led by Isabelle Szott of the Sokoine University of Agriculture and Kate Webb of Duke University. “Their small size also offers unique capabilities for the screening of shipping containers, such as being able to navigate densely packed areas or be lifted to assess contents of sealed containers by screening ventilation systems.”
To test out the hypothesis, the team trained their rats to detect the scent of commonly trafficked items like pangolin scales, rhino horn, and ivory. The rodents were highly adept at the task even when those smells were concealed in mixtures among non-target items. “These results provide the foundation to train rats for scent-detection of illegally trafficked wildlife to combat IWT.”
It’s worth noting that while this particular rat species is big by rat standards—weighing a few pounds each, while a standard NYC subway rat rarely tops a pound—the “giant” in its name refers to its adorably enlarged cheek pouches.
Star Acting Weird, No One Knows Why
Pereira, Alan, “The persistent Be enigma: The case of HD 212044,” Astronomy & Astrophysics
Strange things are afoot at HD 212044, a star about 3,000 light years from Earth. It’s not aliens (probably). It’s just that the emission spectra of the star, which is the light pattern we receive from it, does not match other stars of its “Be” class.
Be stars are massive objects surrounded by disks of gas and dust that cause them to vary in brightness. Scientists have previously observed that Be stars at low inclinations—meaning a low angle between the star's rotation axis and our line of sight on Earth—show a positive correlation between their brightness and the intensity of the hydrogen-alpha emission line, which is a red spectral signature linked to electron activity in hydrogen atoms.
But HD 212044 does just the opposite, showing an “anticorrelation between photometric brightness and hydrogen-alpha intensity, which challenges expectations,” according to a new study.
“This unusual behavior suggests that additional or alternative mechanisms may influence the variability of HD 212044 beyond what is typically observed in similar stars,” said researchers led by Alan Pereira of Brazil’s Observatório Nacional. “Further studies are needed to explore these findings in more detail and to clarify the underlying processes driving this star’s behavior.”
This study belongs to the classic research genre of “what’s up with this.” These studies very rarely make the news, but they are important flags about inconsistencies that require attention and follow-up research. In this case, the phrase “additional or alternative mechanisms” is vague for a reason—it’s not at all clear why HD 212044 bucked the mold. Maybe it never will be. But the first step to solving a problem is to professionally report that hey…something seems kind of weird over here.
Thanks for reading! See you next week.
