Biology – Page 3 – The Better Dog Life

What is a dog’s strongest sense? What is their weakest? Is there some other spidey sense that I didn’t know about? These were the questions I found myself asking in my head. Without question, Smell is a dog's strongest scent and is critical to their understanding of the world around them. Dog's have up to 300 million olfactory receptors compared to a human's five million. Additionally, dogs can continuously process scent while breathing in and out. Even with the sense of smell taking center stage, a dog's abilities within their other senses may not be what you think. I was inspired to dig deeper into this one random evening. We snuggled in as a family to watch a show on tv and our dog Juno began watching the screen. I’ve had other dogs that look at the television, so that wasn’t new to me. Our Great Pyrenees would even bark at certain animals, so he was definitely identifying other shapes. God forbid a horse, dog, or deer walk across the screen. You’d swear we were being invaded by the way he reacted. However, watching Juno interested in the TV caused me to pause and ponder about dog’s senses and how they function compared to ours. Just how do they process the world around them? In this article I will go through each of the following: How strong is a dog's sense of touch?How strong is a dog's sense of taste?How strong is a dog's sense of sight?How strong is a dog's sense of hearingHow strong is a dog's sense of smell?Do dogs have any sixth sense? How strong is a dog's sense of touch? Just as we have nerves all over our body that sense all kinds of different contact information, so do dogs - just a little bit different. In a human, our greatest sense of touch is concentrated in our index finger. We can tell texture better with our index finger than any other part of our body. Likewise, our feet are sensitive to pressure. If you have kids, you know just how bad it hurts to step on a Lego or a Barbie shoe. For dogs, their sensory outfitting is just a bit different. Whiskers, which are found on the side of their muzzle, below their jaw, and above their eyes help a dog sense objects and help them navigate. I always thought it was kind of funny that dogs have whiskers. Most of the time I don’t really notice them, but if you look closely, it looks like they have a mustache and out of control eyebrows. I always get a chuckle out of that. In an article, famous dog trainer, Victoria Stilwell, shared that a dog’s whiskers (called vibrissae) are so sensitive that a dog can sense airflow changes as they approach an object. This is one of the reasons it is crucial to get a puppy familiar with an approaching hand from a human. Additionally, dogs have many nerve endings all down their spine and at the base of their tail. This makes them very sensitive to touch in those areas. This is why dogs go nuts when you scratch their lower back. Especially when they start kicking/scratching with their back leg (a friend of my mine refers to that as “starting their motorcycle”). It seems as though touch may not be a dog's strongest sense. Just be careful though. Not all dogs like to be touched that way or are used to being touched that way. Make sure you are familiar with any dog before touching them and always ask another dog’s owner if it is okay to pet them. How strong is a dog's sense of taste? You may be surprised to find out that a dog’s ability to taste is not all that great. In fact, their taste is probably their weakest sense. According to PetMD, humans have six times the amount of taste buds that dogs do. While dogs can taste bitter, salty, sweet and sour, it turns out that smell plays a bigger part in what they decide to eat, which is not too surprising. However, this does explain why dogs eat some of the gross things they do. Like how they can dig through the litter box and munch on those “kitty cookies” (insert dry heaving noise). I expected to find out more on this subject, but it turns out this sense in dogs is just rather underwhelming. How strong is a dog's sense of sight? This question is probably better split into 3 sub questions: How good is their eyesight?Can dogs see colors?How well do dogs see at night? How good is a dog's eyesight? A post on Sciencedaily.com quotes Paul Miller, Professor of Comparative Ophthalmology at University of Wisconsin-Madison as saying that a dog’s ability to see in dim light makes their eyesight roughly 20:80 as opposed to human vision of 20:20. Additionally, The Pets Doc Veterinary Clinic shares that a dog's eyesight is roughly 20:75. That means that a dog sees details at a distance of 20 feet that humans can see at 75-80 feet. Additionally, in the Documentary, A Dog's Life, Dr. Krista MacPherson, of Western University of London, Ontario, discusses an interesting indicator in specific dogs and their ability to see distances. Basically, the longer a dogs skull, the more that the cells that transmit signals to the brain are arraigned in a horizontal streak. The longer the skull, the more pronounced the streak (long skulls meaning breeds like a Greyhounds). What that means is that the longer streak of cells equals better vision at a distance. The shorter the skull - the shorter the streak, which results in better short vision. Dogs see an object twice as far away as they can when it is stationary. This makes sense from a tracking prey standpoint. The Pet Docs Veterinary Clinic also goes into how dogs eyes are set in their head. In humans our eyes are set straight forward. Dog’s eyes, depending on the breed, are typically set at a 20 degree angle. This allows the dogs to have better peripheral vision, but impacts their binocular vision (fancy word for overlapping fields of vision), which aids in depth perception. Dog’s depth perception is best when looking straight forward. What's more, dogs can see an object moving twice as far away as they can when that same object is stationary. This makes sense from a tracking prey standpoint. Can dogs see colors? The short answer, yes. The notion that dogs see the world in black and white is simply not true. That seems to be just a myth that keeps hanging around. According to an article on PetMD, dogs can absolutely see color. It’s just not the same spectrum of color as humans see. This is due to the fact that a human’s retina (photoreceptor) has red, blue, and green cones. A dog’s retina only has two cones, “a blue cone and a visual pigment that falls somewhere between a human red and green”. A dog’s color vision is most comparable to a person with red-green color blindness. How well do dogs see at night? AKC.org has a very in-depth post on dog’s vision, but one interesting portion refers to a dog's ability to see at night or in the dark. There are a couple different things that allow a dog to navigate through the darkness. First, their pupils are larger than a human’s, which allows more light to enter the retina. In turn, dog’s retinas have more rods than humans. Rods are the structure that help the eyes see in low light. Secondly, they have a higher Flicker Fusion Frequency (FFF). Basically, the FFF is the frequency that light no longer flickers, but appears as a constant glow. Basically, in video terms, this allows them to see more frames per second than our eyes. A really good way to explain this is using a television. To us humans, images on a television screen appear smooth and seamless. Since dogs see more frames per second, the same television image would appear to flicker or skip. Thirdly, the ace in the hole, is the part of the dog’s eye called the tapetum (pronounced tah-pee-dum). The tapetum reflects back light entering the eye, making the most of available light. This is somewhat similar to how night vision goggles work for humans. This is also why a dog's eyes appear to glow at night. What you are seeing is the light reflecting off the tapetum. I always wondered how that happened. Light reflecting off the tapetum How strong is a dog's sense of hearing? We are getting to what are arguably the two strongest senses that dog’s possess, hearing and smell. First up is hearing. Dog’s have ridiculously better ears. In fact, they can hear sounds four times farther away than humans. Why is this though? It turns out that dogs can hear higher frequency sounds, which allows them to distinguish a greater range of sounds and they can pinpoint the exact location of the sound. Okay great, but how the heck can they do all that? Sound is simply vibrations in the air and the ability to hear these vibrations differs between us and dogs. I’m going to nerd out here a little and explain that it’s important to understand that we are talking frequency (measured in Hertz or Hz) not loudness (measured in decibels or dB). For instance, a jet engine at take off is 140 dB, which is loud, but is only between 400 and 1300 Hz). That’s lower than the frequency of conversational human speech. Humans, on average, can’t really hear anything above 20,000 vibrations per second (Hz). Dogs on the other hand, can hear sounds up to 50,000 vibrations per second (Hz). A dog whistle is around 23,000 Hz. Dog’s ears are also set up to process sound better than our ears. Dog’s ears are controlled by 18 muscles, while we humans only have six to operate ours. This allows dogs to move their ears around like little furry satellites to pinpoint the sound. Additionally, ear shapes in different breeds can amplify the sounds. Think about the difference of a pointy-eared German Shepherd compared to a big old, floppy-eared, Basset Hound. Furthermore, dogs have longer ear canals than humans and dogs can use their ear canals to triangulate on a sound for improved accuracy and distance. Pretty darn cool! How strong is a dog's sense of smell? The sense of smell in dogs is by far their most impressive ability and is certainly a dog’s strongest sense. Smell is also arguably the sense they rely on the most. This is the reason that humans utilize dogs to detect bombs and drugs, as well as, to track prey and search for other humans. It’s also their social handshake. I’m always thankful God did not make butt sniffing a keystone of human social interaction. I’m happy with handshakes and high fives. Just how good are dogs at smelling? It turns out that their ability to smell can be as much as 100,000 times greater than ours. Dogs can detect odors in parts-per-trillion. In simple terms that’s like being able to smell a treat hidden in a couple million boxes. That’s absolutely crazy! There are a few different reasons dogs are able to do this: Receptors Dogs have about 300 million olfactory receptors in their noses, while we have a measly six million in ours. Also, the part of a dog’s brain that processes smells is proportionately 40 times greater than a humans. Inhaling When dogs inhale, their noses split the air into two different paths. One path takes a portion (about 10% or so) of the air to process the scent, while the other path leads the rest of the air to the lungs for breathing. The red arrows are the airflow being directed for scent processing, while the blue arrows are the airflow being directed to the lungs. Exhaling When dogs exhale, the air travels out the slits of their nose, causing air to swirl and help bring more air in for processing scent. This also allows dogs to process scent continuously - somewhat like circular breathing. Jacobson’s organ Dog’s have a second olfactory system that we just don’t have, the Jacobson’s organ. The Jacobson’s organ is in the bottom of a dog’s nasal passage. It’s function is to pick up pheromones in the air. The pheromones are also analyzed separately from odors because the Jacobson’s organ has its own nerves and a part of the brain dedicated solely to it’s inputs. If you want to read a more indepth academic article on dogs and how they smell, check out The Fluid Dynamics of Canine Olfaction by Craven, Patterson, and Settles of Penn State University. Do dogs have a sixth sense? I know the five senses are a given, but we’ve all heard stories of dogs doing amazing things. A lot of these stories make us believe there is something else there that allows dogs to make sense of situations or sense things we can’t seem to. Turns out it isn’t just their better hearing or smell. Magnetism I stumbled across an article on PsychologyToday by Dr. Stanley Coren. Dr. Coren discusses a study by Sabine Martini of the University of Duisburg-Essen in Essen, Germany. This study showed that dogs can sense magnetism. Dr. Coren likened this to how migratory birds sense Earth’s magnetic poles. In this study by Savine Martini, researchers placed magnets in dark glass jars with lids. The researchers did some clicker training to let the dogs know that they were to choose the magnet. Results? It turns out that 13 of 16 dogs detected the magnet. This suggests that there is something that is allowing dogs to sense and make decisions based on the information they detect with magnetism. Ability to read Human Emotion Reuters published an interesting article regarding a joint study between the University of Lincoln, UK and University of Sao Paulo, Brazil. The researchers took 17 untrained dogs and showed them positive or negative emotional displays from both humans and dogs. When the dogs heard positive sounds the dogs looked longer at positive faces (both human and dog). When the dogs heard negative sounds they paid more attention to angry faces. This observation leads to the idea that dogs are able to connect positive or negative sounds to positive or negative expressions. Additionally, there is a whole other awesome topic about how dogs read humans vs. other animals, but I will cover that in another article. Conclusion Dog’s sense of smell is by far the most impressive. If you take the time to think about it, scent tracking dogs do some pretty crazy stuff. They are able to be given one scent, analyze it, then track it over miles. Sometimes they are just relying on fragments of an odor, possibly days old. Then they are also separating that odor in their mind from other odors and determining the direction to keep tracking. That is simply amazing to me! So next time you are taking your pooch for a walk, remember they are probably getting more from sniffing the air and ground than all of their other senses combined.