【推荐2】My dog, Nala, loves rolling around in a patch of grass any chance she gets. And it always cracks me up to watch her have the time of her life.     1    . To find out why Nala and so many other dogs like to stop, drop and roll, I reached out to Dr. Stephanie Austin, a veterinarian, who explained that dogs can roll in the grass for several reasons! Here are some of the most common explanations behind this behavior

She’s enjoying a smell.     2    . “They are picking up on hundreds of nuanced scents that we can’t even comprehend!” Dr. Austin told The Dodo. “Sometimes they want to enjoy a scent they’ve found in the grass and will roll around in it to do just that.”

She’s covering up her own scent. According to Dr. Austin, there is another theory that dogs may roll in grass to cover their own scent, as more of an inherited predatory instinct.     3    .

    4    . “It’s good to rule out any allergies and make sure your dog isn’t rolling a ton to scratch a constantly itchy back or side, but otherwise, it’s probably normal that he’s having a good time,” Dr. Austin said.

If you notice your dog rolling around in the grass, it’s probably just her having the best time ever. I’m not sure about you,     5    .

【推荐3】Army ants make a habit of killing organisms, often much larger than themselves, breaking them into pieces and dragging them back to their bases. They don’t eat everything. Waste full with discarded bits of prey is a feature of army ant bases. But little is known about which animals make use of army ant leavings.

As recounted in a paper in Ecology &. Evolution, Christoph von Beer en at the Technical University of Darmstadt and Daniel Kronauer at the Rockefeller University in New York, went to the rainforests of Costa Rica to find out. They found an entire ecosystem thriving among the leftovers.

Monitoring tiny insects in a rainforest is tricky. But the researchers hoped modern DNA analysis techniques might make the job manageable. Working with a team of colleagues, they followed ant trails back to their bases, finding 34 sites in total.

The researchers used a handheld vacuum cleaner to suck up all the bugs at waste and brought the samples back to a field laboratory. To keep the task manageable, the team confined themselves to examining only the beetles they had collected. They identified the beetles they could and ran DNA analyses on those they could not.

In total, they collected 8, 364 adult beetles, 511 beetle larvae and 24 beetle eggs. Those were spread across 91 species, several of which were entirely new to science. Aside from that being far more than anyone had expected, the presence of the larvae and eggs indicates that the leftovers are not so much convenient restaurants as full-on homes, where the beetles live out their entire lives.

Precisely how these species manage to avoid being eaten themselves by their army-ant hosts remains to be determined. Dr. von Beeren speculates that a hygiene instinct that keeps the ants from eating material that has been taken to their waste is partially responsible. And many species of beetles are able to produce compounds that smell disgusting to ants. The chances are high that among these insects are some predators too, seeking to feed on unsuspecting scavengers (食腐动物) in turn.

【推荐1】Carers at a place called TRC waved a happy goodbye this week to Bear, a much-loved green sea turtle (龟) who swam to freedom from Mooloolaba Beach. Bear was found injured on a shore in February. Its bone was injured and it was covered by small harmful creatures. Bear spent 116 days receiving care at TRC.

Though Beal’s carers got to know him well—such as what food he preferred and that he was very cheeky—it was important he didn’t become too used to being cared for by people. “When we care for a turtle. we’d try to communicate as little as possible,” Ms Attwood said. “When a turtle is sent back into the ocean, we don’t want them to rely on humans for food. They need to know how to search for food themselves. The one time we may need to communicate with a turtle more often is if they need any special treatments.”

So where will be Bear? Bear will most likely stay swimming around the Indo-Pacific area. Green turtle loves to eat sea grass, which is why coral reefs (珊瑚礁) are always a popular place. The Great Barrier Reef is a common area turtles like to visit. Bear is now carrying certain equipment, so his former carers and turtle experts around the world will be able to follow where he goes in the future.

Bear is a type of green sea turtles. They’re called green sea turtles because they have green fat under the back. We can tell them apart from other kinds of sea turtles because they have only a pair of scales (鳞) in front of their eyes. And green sea turtles are the largest types of sea turtle. They grow to about 110-190 kg. But they are dying out due to humans who want their eggs, meat and skin. Some are accidentally caught by fishing ropes.

【推荐2】Late last year, a French company called Carmat received approval in Europe for its total artificial heart. It’s exactly what it sounds like; a heart made of synthetic and biological materials intended for implantation into people who need heart transplants. Now, just half a year later, the first US patient has received one of the Carmat artificial hearts (CAH).

The transplant took place last week in a 39-year-old man at Duke University Hospital in North Carolina. The man didn’t go to the hospital expecting to have a heart transplant, but it ended up saving his life.

After experiencing unexpected heart failure, he was diagnosed with advanced coronary artery disease and went in for bypass surgery.

When his condition quickly worsened, his medical team realized bypass surgery wasn’t going to do it, but by that point a traditional heart transplant had become too risky. The patient was in the right place, because not just any transplant center could have implanted an artificial heart.

The device weighs 900 grams, or just under 2 pounds (about three times the weight of the average human heart). The external setup is a bit heavier; recipients will have to carry about nine pounds of equipment, including a controller, a bag of actuator fluid, and two battery packs. In the case of the Duke patient, his artificial heart will stay remotely connected to the hospital’s system so that his doctors can monitor it and be sure it’s functioning as it should.

Just days after the US transplant, a similar transplant took place in Naples, Italy, marking Carmat’s first commercial sale of the heart (the difference being that this patient’s transplant was planned, not done as part of a trial).