Bats use leaves as “mirrors” to understand the presence of resting insects

Bats have a particular localization system that involves sight and hearing to understand, even in darkness, the position of obstacles and even prey, and this is a well-known thing. However, a new study, published in Current Biology, shows how sensitive these animals are through their echolocation system.

Capturing insects and intercepting them in the dark is an impossible task for many, but not for bats. The experiments that the scientists of the Smithsonian Tropical Research Institute (STRI) have conducted, in fact, show that bats are able to trace even acoustically camouflaged prey, that is to say silent prey on the leaves.

Bats are able to hunt these insects thanks to a sort of sixth sense: they flood the surrounding area with sound waves and then use the return echoes to navigate through the environments. However, they also do this with regard to objects of limited extension such as the leaves: the latter reflect the signals and if the latter is a little weaker because there is an insect resting on the bats they can recognize the difference. And this also in a tropical forest, in the thick foliage that characterizes this environment.

Scientists have discovered that if the sound bouncing off the leaves comes from oblique angles greater than 30 degrees, the leaves themselves can behave like “mirrors” like a lake reflects the surrounding forest at dusk at dawn. This means, according to the researchers, that the same angle of approach makes the insect at rest detectable. Therefore the same researchers have deduced that the bats tend to approach the insects that rest on the leaves through angles comprised between 42 and 78 degrees, considered optimal angles to discern the same presence of the insect on the leaf.


Carnivorous ancestor of today’s short-tailed opossum identified

The short-tailed possums, a genus of marsupials classified as Monodelphis of which today there are 24 species, are fairly peaceful animals, slightly larger than a mouse, widespread especially in South America.

Now a new study, published in the Journal of Mammalian Evolution, confirms the existence of a ferocious direct relative of this animal that lived about 4 million years ago in the same areas of South America. We speak of Sparassocynus, a carnivorous relative of Monodelphis, whose remains have been found for more than a century even if its evolution has never been well studied, at least until this new study.

The research, conducted by Robin Beck, a researcher at the University of Salford, and by Matías Taglioretti, a paleontologist at the Museo Municipal de Ciencias Naturales “Lorenzo Scaglia” in Argentina, has identified several proofs that Sparassocynus is one of the ancestors of the today’s short-tailed opossums. In particular the scientists analyzed the remains of the skull, remains found near some cliffs along the Atlantic coast of Argentina.

It is an individual not fully grown as it still has traces of milk teeth. The researchers analyzed different characteristics comparing them with the evidence taken from the DNA of today’s short-tailed opossums and showed that this animal is closely related to today’s short-quota opossums. It was a carnivore that probably ate other rodents and small vertebrates and was larger than today’s short-tailed opossums about five times.

Today’s opossums are much more “quiet” animals and eat only small insects. The Sparassocynus survived in areas of South America up to 2.5 million years ago and is possibly extinct due to the arrival of the weasels from North America.


New type of pulsating star discovered

A group of scientists from the University of California at Santa Barbara claims to have discovered a new type of pulsating star. This new class of stars seems to vary the brightness every five minutes. In the study, published in the Astrophysical Journal Letters, the researchers, led by Thomas Kupfer, explain the results of their analysis.

In the press release on the university website is Kupfer himself, a researcher at the Kavli Institute for Theoretical Physics (KITP) of the same faculty, to explain the discovery. First of all, he reports that the pulsating stars, or even variable stars, are many and indeed even our Sun, even on a very small scale, performs pulsations. Around a variation of brightness of about 10%, however, we begin to talk about pulsating stars and those that see the major changes in the University are defined radial pulsators that seem to “breathe in and breathe” changing in size.

By studying these mutations in detail, it is possible to learn a great deal about these stars. And that’s exactly what Kupfer did that set out to search for binary stars with pulsation periods of less than an hour. They found four pulsating stars in which great changes in brightness occur within a few minutes and were not binary systems.

Checking the data, they realized that it was a new kind of pulsating stars that had hot button substances. The hot substances are stars that have “completed the fusion of all the hydrogen in their helium nucleus” and this is “because they are so small and can oscillate so quickly,” as stated by Lars Bildsten, director of the KITP and another author of the study.

They are very hot, much warmer than the Sun, although they have a mass between 20 and 50% of that of the same Sun. The pulsating hot substances were never predicted theoretically but, once analyzed, they adapted without problems to the main models of stellar evolution.