Tag Archives: bubbles

Whales blow bubbly nets to help them fish — and we have it on camera

New research at the University of Hawaiʻi at Mānoa is shedding light on whales’ bubble-net fishing.

Cetaceans, the group that whales and dolphins are part of, are pretty smart creatures. We’ve known that they can use ‘nets’ to catch food — the animals dive deep and swim in a circle around their prey, blowing out bubbles as they do. The rising body of air traps fish in the middle. Other whales then simply have to swim up with their mouths open and cash in on the food with virtually zero effort.

Now, new research is showing what this process looks like from the perspective of the whales.

Like shooting fish in a barrel

“We have two angles. The drone’s perspective is showing us these bubble nets and how the bubbles are starting to come to the surface and how the animals come up through the bubble net as they surface, while the cameras on the whales are showing us the animal’s perspective,” said marine biologist Lars Bejder of the university’s Marine Mammal Research Program.

The study included members from the Alaska Whale Foundation, members of Stanford University’s Goldbogen Lab, and from the Bio-telemetry and Behavioral Ecology Lab at the University of California, Santa Cruz. Together with Bejder and colleagues at UH Mānoa, they stuck cameras and accelerometers on whales using suction cups. The material was supplemented by drone footage of the behavior from above to create an “exciting” set of data, Bejder explains.

Migratory humpback whales spend their summer along Alaska’s coast before heading down to Hawaii for winter — where they’ll raise a new generation of whales. However, all that romance leaves little time for feeding (the humpbacks eat very little during their breeding period), so fat reserves need to be plumped up before the journey.

That’s where the bubble nets come into play. Whales could just swim around and filter krill the old fashioned way, but time is of the essence during winter. The bubble-fishing technique allows groups of whales to invest as little time and energy as possible while maximizing their caloric intake. It’s a win-win approach.

The team notes that the behavior is learned — the whales don’t instinctively engage in bubble fishing. Not all humpbacks hunt this way, they add, and there is a pretty wide range of variations in technique among those who do. However, it’s always a cooperative process, requiring groups of whales to work together to ensure that everyone has a chance at the buffet.

The team reports that the behavior has also been observed Bryde’s whales (Balaenoptera edeni) and bottlenose dolphins (genus Tursiops) off the coast of Florida. Instead of using bubbles, however, these groups of cetaceans engage in mud-ring feeding: this involves stirring up a ring of sediment in shallow waters to trap schools of fish.

This study was done in an effort to understand just what is going on with humpback whales. A ban on commercial whaling in 1985 saved the species from almost assured extinction and, while they have recovered somewhat, there has been a substantial decline in humpback whale sightings over the last five years, the researchers report. Some of the factors they are considering include changes to food populations, anthropogenic impacts on their habitat, and climate breakdown.

But, while the researchers ply their trade, we’re left with some awesome shots of whales doing whale things — of course no one’s complaining.

“The footage is rather groundbreaking,” Bejder said. “We’re observing how these animals are manipulating their prey and preparing the prey for capture. It is allowing us to gain new insights that we really haven’t been able to do before.”

Credit: Pixabay.

How to blow the perfect soap bubbles, explained by science

Physicists have unpacked the physics behind one of childhood’s favorite pastimes: blowing soap bubbles. Their experiments have revealed what’s the perfect size for a circular wand and the optimal wind speed required to blow bubbles that don’t pop. And while this may sound like a trivial study worthy of an Ig Nobel Prize, the study might actually help manufacturers make better sprays, foams, emulsions, and basically anything that has bubbles in it.

Credit: Pixabay.

Credit: Pixabay.

Studying bubbles has actually been a century-long intellectual pursuit that has helped scientists gain valuable physical and mathematical insights. For instance, a soap bubble is a perfect example of surface tension in action. It’s because of surface tension that bubbles are round — it’s this shape that determines a minimal surface area for a given volume and, hence, requires the least amount of energy to maintain. And it’s thanks to soap bubbles that some complex mathematical problems have been solved with real-world applications following not long after. For instance, equations that describe soap bubble formation have helped architects design roofs whose shape look impossible but are stable nonetheless. The Olympic Stadium in Munich is an illustrating example.

Tensile structures like the one at the Olympic Stadium in Munich were discovered with the help of soap bubbles. Image via Wiki Commons.

Most recently, researchers at New York University (NYU) devised a series of experiments to help them blow the perfect bubble we’ve been chasing since we were kids. These revealed that, essentially, there are only two ways in which bubbles can be made: one is by blowing a strong, steady wind on a soap film, the other is by pushing with a gentle wind in an already inflated film to raise its volume.

“This second method might explain how we often blow bubbles as kids: a quick puff bends the film outward and thereafter the film keeps growing even as the flow of air slows,” said Leif Ristroph, an assistant professor at NYU’s Courant Institute of Mathematical Sciences who led the study, in a a statement.

The first method, on the other hand, is less widely used.

“This is used by the bubble blowers we see in parks in the summertime,” explained Ristroph. “They simply walk, sufficiently fast, it seems, with a soapy loop of rope, which provides the relative wind needed to stretch out the film.”

Blowing bubbles is essentially a question of how a liquid film interacts with an imposed flow of an external fluid, in this case, air. However, for their experiments, the researchers used oil films suspended in flowing water and pushed through a wire loop wand. Using water instead of air allowed the researchers to control, measure, and observe the flows more accurately. What’s more, the observations matched the theoretical predictions for the film’s shape.

So, if you’d like to make perfect bubbles, according to this study you’d better find a wand with a 1.5-inch perimeter and gently blow at a consistent velocity of 6.9 cm/s. Any faster or slower, and the bubble will eventually burst; the same goes for the wand if it’s smaller or larger. On to you!

The findings appeared in the journal Physical Review Letters.