Tag: dogs

Animals Lapping
Without full cheeks, cats, dogs, and many other animals cannot use suction to drink. Instead, these animals press their tongue against a fluid and lift it rapidly to draw up a column of liquid. They then close their mouth on the liquid before it breaks up and falls down. (Cats are a bit neater about it, but as the high-speed images above show, dogs use the same method.)
A new study takes a look at the mathematics behind this feat, specifically how long it takes for the liquid column to break up. Normally, we describe that problem using the Plateau-Rayleigh instability, but in its usual form, the PR instability doesn’t account for the kind of acceleration drinking animals apply to the fluid. This new study modifies the equations to account for acceleration and finds that the predicted time it takes for breakup is consistent with the timing of animals closing their mouths on the water. In other words, cats and dogs are likely timing their lapping to maximize the amount of water they catch with each bite. (Image credits: top – C. van Oijen, others – S. Jung et al. 1, 2; research credit: S. Jung)
September 30, 2021
Why Animals Shake Themselves Dry
For many animals, letting themselves air-dry is not an option. They would become hypothermic before their wet fur dried completely. This is why dogs and many other furry mammals shake themselves dry. It’s a remarkably efficient process, too, removing the majority of water from fur in a matter of seconds.
The key is to shake at a frequency such that the centrifugal force of the shake overcomes surface tension’s ability to keep the water attached to fur. The looseness of a dog’s skin (compared to humans!) is a bonus for them; the extra translation as they shake increases the centrifugal force, allowing them to shed more water more quickly. (Image and video credit: BBC Earth; research credit: A. Dickerson et al.)
April 8, 2020
Sniffing
In many ways, smell is a strange sense. The very act of sniffing – pulling air and odor molecules into our noses – changes what remains behind in a way that sight and sound do not. Humans aren’t great sniffers, but dogs have an exquisite sense of smell, and in this video, Deep Look describes how and why that is. From special scent organs to their experimental protocols, dogs are well-adapted to reading the world by smell. (Image and video credit: Deep Look)
March 15, 2019
How Dogs and Cats Drink
We humans do our hands-free drinking via suction, using the shape of our lips and mouths to create low pressure that draws liquids in. Dogs and cats, on the other hand, have no cheeks and, therefore, no suction. Instead, both cats (top) and dogs (bottom) drink using adhesion, or the tendency of a liquid to stick to a surface. Both species flatten part of their tongue against the water surface, then pull it up rapidly. This draws a column of water up after their tongue, which they then snap their jaws closed around. Although they use the same method, cats are daintier drinkers than dogs, which sometimes leads to the misconception that the animals drink differently. (Image credits: NYTimes, source; research credit: S. Jung et al.)
September 7, 2015
How Dogs Drink
This high-speed footage shows how a dog drinks. The dog’s tongue curls backwards, creating a large area of surface contact with the water. When the dog pulls its tongue back up, water adheres to it and is drawn upward in a column. The dog then closes its mouth around the water before it falls. Fundamentally, this is the same mechanism as the one cats use. Part of the reason that dogs are messier drinkers, though, is that the backwards curl of their tongue picks up extra water. Because the dog has no cheeks, there’s no way to move this water from the underside to the top of the tongue and so the water just falls back out. (Video credit: Oxford Scientific Films; submitted by Carolyn W.)
March 21, 2014
Fluids Round-up – 7 September 2013
Lots of great links in this week’s fluids round-up!
- Scientific American discusses how dogs use adhesion of water to their tongues to drink. We’ve mentioned this previously, as well as how it’s the same method cats use.
- Wired has a great look inside the NASA Ames Vertical Gun Range and how it’s used for impact cratering studies.
- Artist Fabian Oefner, whose work we’ve featured previous (1, 2, 3), gave a TEDx talk on mixing art and science, using acoustics and ferrofluids.
- Veritasium’s video on vibrating oobleck on a speaker has some nice visuals, and his suggestion of the behavior of highway traffic as a non-Newtonian fluid is intriguing. I generally consider such traffic to be a prime example of compressible flow, but that’s a whole post in and of itself.
- GE’s 6secondscience fair challenges participants to fit their science into 6 seconds of video. There are some great fluids examples, as seen in this compilation video. (submitted by jshoer) For a breakdown of each scientific concept, check out It’s Okay to be Smart’s list.
- I don’t know about you, but this bus window would keep me entertained for my whole commute. It’s like a 2D lesson in Newton’s laws and sloshing. (submitted by Erik M)
- There are some epic and beautiful examples of fluid dynamics in this collection of Red Bull Illume photo contest winners. (via +Jennifer Ouellette)
- Finally, this week’s lead image is a collage of gorgeous microfluidic multi-fluid emulsions. Learn more about them over at Physics in Drops.
(Photo credit: L. L. A. Adams)
September 7, 2013
How Dogs Drink
Not long ago, researchers showed that cats use friction to their advantage when drawing liquids into their mouths. New research shows that dogs rely on the same mechanism–they’re just far less efficient with it. The dog touches its backwards-curled tongue to the surface of the water; when it draws the tongue back, friction causes a column of fluid to follow. The dog then closes its jaws around the water. Some water also gets picked up by the back of the tongue, but since dogs have no cheeks, it spills out the sides, creating a mess familiar to dog owners. #
May 26, 2011