Tag Archives: echolocation

Fossil Friday: huge, ancient dolphin was the first echolocating apex predator

The fossil of a 15-meter-long extinct species of dolphin is helping us better understand how different lineages of marine mammal independently evolved the same characteristics.

Skull and Skeleton of Ankylorhiza tiedemani.
Image credits Robert Boessenecker et al., (2020), Current Biology.

The species, christened Ankylorhiza tiedemani lived about 25 million years ago during the Oligocene in what today is South Carolina. It belonged to a group of large dolphins (Odontoceti) whose best-known modern representative is the orca (killer whale).

The anatomy of this fossil suggests that it was likely a top predator in its day. It shares several features with today’s baleen and toothed whales despite not being directly related to these groups, the authors report. This suggests that these animals evolved their shared swimming adaptations independently from one another, a phenomenon known as parallel evolution.

Like whales in a pod

“The degree to which baleen whales and dolphins independently arrive at the same overall swimming adaptations, rather than these traits evolving once in the common ancestor of both groups, surprised us,” says Robert Boessenecker of the College of Charleston in Charleston, South Carolina, first author of the paper describing this fossil.

“Some examples include the narrowing of the tail stock, increase in the number of tail vertebrae, and shortening of the humerus (upper arm bone) in the flipper.

Comparison with lineages of seals and sea lions reveal that the two families went down very different evolutionary paths as they transitioned from a land- to a marine-based lifestyle. The initial differences between these lineages were slight, the team explains: Ankylorhiza’s ancestors had one extra row of finger bones in their flippers and a “locking elbow joint”. Still, these factors lead to them developing different swimming styles and skeletal structures.

Another thing the authors note is that Ankylorhiza is the first echolocating whale to become an apex predator. According to the team, it was “very clearly preying upon large-bodied prey like a killer whale”. Its extinction cleared an ecological niche that sperm whales and a lineage of shark-toothed dolphins (both extinct) evolved into. Later still, killer whales would evolve into the same niche around 1 or 2 million years ago.

Ankylorhiza was first described from a skull fragment found during dredging of the Wando River, South Carolina, in the 1880s. A nearly-complete skeleton was later unearthed in the 1970s. The one described in this paper was found in the 1990s by commercial paleontologist Mark Havenstein at a building site and donated it to the Mace Brown Museum of Natural History to allow for its study.

“Whales and dolphins have a complicated and long evolutionary history, and at a glance, you may not get that impression from modern species,” Boessenecker says. “The fossil record has really cracked open this long, winding evolutionary path, and fossils like Ankylorhiza help illuminate how this happened.”

Boessenecker says that there are “many other unique and strange early dolphins and baleen whales from Oligocene aged rocks in Charleston, South Carolina,” including fossils of juvenile Ankylorhiza and specimens of related species. Both filter-feeding and echolocation first appeared during the Oligocene, he adds, so these fossils should give us a very good peek into how they came to be.

The paper “Convergent Evolution of Swimming Adaptations in Modern Whales Revealed by a Large Macrophagous Dolphin from the Oligocene of South Carolina” has been published in the journal Current Biology.

This camera can see around corners in real time

The future is now – researchers at the Heriot-Watt University in Edinburgh, Scotland have developed a camera that can see around corners and track movements in real time.

(Photo : NPG Press | YouTube)

The camera used an already developed technique called echo mapping – more or less the same thing called “echolocation” in the natural world. Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. In this case, the camera emits short pulses of laser at the floor in front of a wall. The laser bounces off the walls through the room and ultimately returns to the camera.That laser, in fact, fires as many as 67 million times every second, offering a huge amount of information to the camera extremely quickly. It’s not the first time something like this has been developed, but it’s the first time it works in real time, which makes much more interesting.

“This could be incredibly helpful for [computer assisted] vehicles to avoid collisions around sharp turns … or for emergency responders looking around blind corners in dangerous situations,” said Genevieve Gariepy, co-lead researcher on the project.

So far, the tests were carried on successfully and the camera was able to detect one-foot tall objects, and also detect multiple objects at the same time. It also detected the movement within a centimeter or two, and even estimated the speeds of objects. Check out the video below to see it in action.

Here’s how dolphins “see” humans through echolocation

An unprecedented image created by UK and US researchers shows how a submerged human is “seen” by dolphins through echolocation.

Echolocation, also called bio sonar, is the biological sonar used by several kinds of animals, including dolphins. Basically, they emit sounds around them and then listen to the returning echo to locate and identify different objects or creatures around them. For this experiment, a female dolphin named Amaya directed her sonar beams at a submerged diver, while hydrophones captured the ensuing echoes. To avoid added noise, the diver went in without a breathing device that could cause extra bubbles.

The team led by Jack Kassewitz of SpeakDolphin.com used an imaging system known as a Cymascope. The system makes it possible to record and store dolphin echolocation info and then create 2D images from those sounds. Computers can then, through models, improve this image and make it 3D.

“We’ve been working on dolphin communication for more than a decade,” noted Kassewitz in a release. “When we discovered that dolphins not exposed to the echolocation experiment could identify objects from recorded dolphin sounds with 92% accuracy, we began to look for a way for to see what was in those sounds.”

The results were so good they surprised even the researchers – for the first time, we get the chance to see what cetaceans “see” through echolocation.

“We were thrilled by the first successful print of a cube by the brilliant team at 3D Systems,” said Kassewitz. “But seeing the 3D print of a human being left us all speechless. For the first time ever, we may be holding in our hands a glimpse into what cetaceans see with sound. Nearly every experiment is bringing us more images with more detail.”

For the future, they plan to determine how dolphins share these images, through some kind of sono-pictorial languages (that uses both sounds and images). It would also be interesting to see how dolphins perceive these images, as it’s certain they don’t do it the same way as us.

(c) askabiologist.asu.edu/

Convergent evolution in bats and dolphins driven by same genes

It’s amazing how two different animals from two completely different environments evolve some identical physical features. Take bats and dolphins for instance. Both of them use a complex system that produces, receives and process ultrasonic sound waves in order to identify visually hidden objects, track down prey or navigate through obstacles better – typically this is referred to as echolocation, a natural sonar. The evolution of similar traits in different species, is known as convergent evolution, and  according to new research led by scientists at Queen Mary University of London and published in Nature this week, evolution at a genetic level is also shared during this process.

To see the extent to which convergent evolution involves the same genes, the researchers proceeded to undertake the most complex and thorough genome-wide surveys of its type. As such, the genomes of some 22 mammals were analyzed, each sequence being compared the other. This included bats and bottlenose dolphins – two species that both use the same form of echolocation, but which have evolved it independently.

This was no easy task, however. To perform the analysis, the team had to sift through millions of letters of genetic code using a computer program developed to calculate the probability of convergent changes occurring by chance, so they could reliably identify ‘odd-man-out’ genes. They used a supercomputer at Queen Mary’s School of Physics and Astronomy (GridPP High Throughput Cluster) to carry out the survey.

(c)  askabiologist.asu.edu/

(c) askabiologist.asu.edu/

Did you know that the scientists that developed the sonar and radar navigation systems used by the military got their idea from studying bat echolocation? Just like bat echolocation, sonar uses sound waves to navigate and determine the location of objects like submarines and ships. Only sonar is used underwater, while bats echolocate in the open air. Radar uses electromagnetic waves to determine the location of objects like planes and ships. Like bat echolocation, radar is also used on open air.

To their surprise, the researchers didn’t find one, two or even dozens of identical genetic changes, but over 200! Consistent with an involvement in echolocation, signs of convergence among bats and the bottlenose dolphin were seen in many genes previously implicated in hearing or deafness.

“We know natural selection is a potent driver of gene sequence evolution, but identifying so many examples where it produces nearly identical results in the genetic sequences of totally unrelated animals is astonishing,” said Dr Joe Parker, from Queen Mary’s School of Biological and Chemical Sciences and first author on the paper.

Dr. Georgia Tsagkogeorga, who undertook the assembly of the new genome data for this study, added: “We found that molecular signals of convergence were widespread, and were seen in many genes across the genome. It greatly adds to our understanding of genome evolution.”

Group leader, Dr Stephen Rossiter, said: “These results could be the tip of the iceberg. As the genomes of more species are sequenced and studied, we may well see other striking cases of convergent adaptations being driven by identical genetic changes.”

Joe Parker, Georgia Tsagkogeorga, James A. Cotton, Yuan Liu, Paolo Provero, Elia Stupka, Stephen J. Rossiter.Genome-wide signatures of convergent evolution in echolocating mammalsNature, 2013; DOI:10.1038/nature12511

Hawk moths jam the bat sonar signals by rubbing their genitals

It’s a dog eat dog out there, and any advantage you can get is more than welcome – as strange as it may be. According to a research published in Biology Letters on 3 July, Hawk moths create an ultrasonic noise that could be used to scare off an attacking bat and to jam the bat’s sonar.

Hawk moth. Picture source.

Hawk moth. Picture source.

Radar jamming is by now a very common technique in human warfare, but not really often seen in the animal world. It’s well known that bets rely on ultrasonic echolocation to get around and find prey – but their prey has adapted as well. Several species of moths have developed ways of hearing this echolocation and, as this study shows – even counter it.

Researchers at Boise State University and the Florida Museum of Natural History pre-recorded the bats’ attack sequence, and then studied what Hawk moths did when they heard this sound. What they did was quite surprising: they created an ultrasonic response by rubbing their genitals against their abdomens; both male and female members did this, albeit using different techniques. They also created the sound when touched. Three species have exhibited this behaviour: Cechenena lineosa, Theretra boisduvalii and Theretra nessus.

“The […] anti-bat ultrasound production in hawkmoths […] might play a similar role as in tiger moths — to startle, warn of chemical defense or jam biosonar,” write the authors, Jesse Barber and Akito Kawahara.

Interestingly enough, moths only exhibited this behaviour near the end of the bat attack sequence, suggesting that this is probably their last line of defense – a last minute “pocket strategy” against their predators.

Scientific article.

Rainforest plant evolved beacon for pollinating bats

A lot of attenton has been given to plants that visually attract pollinating bees, through bright colours and spectacular designs, but bats play a very important role for pollinating as well, and there is much we have yet to understand about how they can be attracted by plants.

Researchers have now discovered that a species of rainforest vine, pollinated by bats, has evolved special shaped leaves with such conspicuous echoes that bats can find it twice as fast using echolocation.

Located in Cuba, Marcgravia evenia has developed a distinctively shaped concave leaf located close to the flower which has amazing acoustic properties. Scientists discovered that it acts as an ideal echo beacon, sending back strong and clear echoes in all directions, practically creating its own signature that bats can easily notce and follow.

Scientists trained bats to search for a small plant located in an artificial background, and the results were conclusive. Dr Marc Holderied of Bristol’s School of Biological Sciences, co-author of the paper, said:

“This echo beacon has benefits for both the plant and the bats. On one hand, it increases the foraging efficiency of nectar-feeding bats, which is of particular importance as they have to pay hundreds of visits to flowers each night to fulfill their energy needs. On the other hand, the M. evenia vine occurs in such low abundance that it requires highly mobile pollinators.”

Echolocation: a new chance for the blind?

As much as technology has improved, the blind still struggle with many of the problems they faced say, 1000 years ago.

braille

However, as researchers from the the University of Alcalá de Henares (UAH) have discovered, the solution may be provided by nature, or more exactly by  other inhabitants of our planet: dolphins and bats. It seems that humans can be just as effective at using echolocation in order to avoid abjects and all it takes is a bit of training.

Several studies were conducted for this purpose. Firstly, the scientists had to discover the most effective sound that could be used, after analysing their physical properties. The conclusion was finally drawn:

The almost ideal sound is the ‘palate click, a click made by placing the tip of the tongue on the palate, just behind the teeth, and moving it quickly backwards, although it is often done downwards, which is wrong”

explained Juan Antonio Martínez, lead author of the study.

These particular sounds are similar to the ones used by dolphins, but at another scale as the sea mammals have special organs for this. The difference is clear: 200 “clicks” per second – the dolphins- to 3-4 “clicks” – the humans. Echolocation is three-dimensional as it allows one to appreciate the distance of an object based on the time that elapsses since the emission of the sound and the moment the echo is received as the sound wave is reflected by the surrounding objects.

echolocation

Moreover, a special method was developed so that people could use echolocation in their daily life. Firstly, one must learn to distinguish between their sounds and any other. Secondly, it is necessary to distinguish between objects according to their geometrical properties, like a sonar does. Although some time is necessary to develop this skill, the results are quite fast. Practising for about two hours every day for a few weeks should be enough for someone to learn to distinguish between a tree and a pavement.

Also the “sh” sount used to make someone keep quiet might prove useful. Moving a pencil, for example, in front of the mouth will definitely be noticed.

Finally, the “palate clicks” must be mastered as they must be properly emitted. in order to succeed, researchers used a laser pointer showing at which part of an object the sound should be aimed.

It seems that not only the blind could benefit fomt this technique, but also the deaf as vibrations are  perceived in the tongue and the bones and not only in the ear. Moreover, firemen, rescue tems or just people lost in the fog could use the technique too.

Echolocation could even prove to be more effective than eyesight in some cases. At first, researchers were only able to tell if someone was or not in front of them, but now they can detect internal structures like bones and even objects from a bag.

As complicated as it may seem, some people have learnt the technique “by trial and error”. A well-known case is the one of Daniel Kisch, the only blind person who was awarded a certificate which made him a guide for other blind people.

source: Plataforma SINC