The Denver Zoo may be closed to visitors to prevent the spread of the new coronavirus, but, for the animals inside, life goes on.
This is especially the case for the zoo's lion pride, which welcomed two new members Thursday, April 23, the zoo announced Tuesday. The new cubs were born to mother and father Kamara and Tobias, who are both four years old.
"We're seeing a lot of positive signs that things are going well, and will continue to keep a close eye on [Kamara] and the cubs in these critical first days and weeks," Assistant Curator of Predators Matt Lenyo said.
The births come little less than a year after the zoo welcomed another lion cub named Tatu, The Denver Post reported. Tatu is also the child of Tobias, meaning he now has two half-siblings. (Their sexes are still unknown.) His mother is Kamara's mother, Neliah, and his birth is now helping the new mom care for her own cubs.
"We are watching Kamara closely to make sure she's showing appropriate maternal behaviors, like nursing and grooming," Lenyo said. "She learned a lot by watching Neliah and interacting with Tatu last year, which really prepared her to be a mom."
The cubs' birth is good news for lion conservation. African lions have decreased by fifty percent since 1994, Wildlife Conservation Network (WCN) told National Geographic. While they once roamed almost the entire African continent, they are now absent from 94 percent of their historic range and are considered vulnerable by the International Union for Conservation of Nature. The primary threats to their survival are loss of prey and habitat, as well as poaching.
"Lions are truly one of the world's universal icons, and they are quietly slipping away," WCN director of conservation programs Paul Thomson told National Geographic.
The new cubs' birth is part of an effort to combat this trend. Tobias, their father, was moved to the Denver Zoo in 2018 from Buffalo in the hope that he would mate with Kamara and Neliah, the zoo said. The move was recommended by the Lion Species Survival Plan, a plan for ensuring healthy, genetically diverse lion populations in zoos belonging to the Association of Zoos and Aquariums (AZA).
"Kamara and Tobias were a very genetically valuable match," General Curator Emily Insalaco said in the birth announcement. "And these cubs are an important contribution to the species' population in AZA facilities, and will help inspire visitors to learn more about their wild cousins."
While the zoo isn't receiving visitors right now, the cubs won't know the difference. They will be secluded with their mother for two months to give them time to connect with her and meet the rest of the pack, which also includes an unrelated seven-year-old female named Sabi.
The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.
"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."
The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.
They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.
They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.
But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.
"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.
What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.
It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.
To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.
First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.
Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.
University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.
"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."
Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.
"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.
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