Tag Archives: ask the vet

Dear Dr. Warford, So What Exactly *Can* Dogs Hear?

3 Jun

You’ve probably noticed and heard, dogs have a more sensitive sense of hearing than we humans do. But what exactly can they hear? And why?

First, let’s look at the way they are built: we’ll start with the outside of the ears. We’ll cover the inner ear and common problems with it in another post- otherwise you’ll be reading for days!

Dogs begin to hear at about 3 weeks of age. In the list of senses, sound is second in sensitivity- and importance for survival- only to their sense of smell.

They have over 18 muscles controlling the movement of their ears- we humans have 6. This allows them to move in much more complicated, deliberate and focused ways than our human ears can.

They can rotate and tilt their ears, allowing them to get those sound waves more efficiently than we can.  Additionally (and very cool), their ears can move independently of each other, allowing them to locate and focus on sounds in different directions. It also helps that their ears tend to be larger and more erect than ours, again, allowing them to get those sound waves better than we can.

Have you ever seen your dog suddenly turn one ear in a different direction, even while their eyes are focused somewhere else, even when surrounded by other sounds? It is likely your dog has picked up a sound you may not even hear and is attempting to locate where it’s coming from.  It really shows their ability to screen noise, and filter out only what they think is new or important.

Most nerdy and doctor folks agree that dogs with heavy, floppy ears don’t hear as well as dogs with erect, upright ears, but they still have us beat by quite a bit.  A bigger concern with floppy eared dogs (not related necessarily to their hearing) is they are more likely to have ear infections due to the heavy ears hanging so close to their head.  Those big ears don’t allow air to get into the ear, giving gross little organisms a nice, warm place to grow. But again, I digress.

Now that we’ve covered what they are hearing *with*, let’s look at what *exactly* they hear. This might get a bit scientific and nerdy, but bear with me. It’ll be worth it.

First let’s talk about sound. Sound is a series of waves (technically: air disruptions) that reach our ears and are translated by our brains into the sounds we hear.

Sound is measured in different ways: including loudness and pitch. Pitch is measured by the frequency of wavelengths that are transmitted.  It is measured in Hertz (we use the acronym/shortened word: Hz).

One Hz means there’s one cycle/second. The lower the number, the lower the pitch, which will have more of a bass tone: like a fog-horn. The higher the number, the higher the pitch, such as a whistle.

This can get very complicated, but a simple explanation: Humans can generally hear a range of 20-20,000 Hz, and the human voice generally ranges from 1000-4000 Hz. Now get ready to be impressed: dogs can hear a range of 40-45,000 Hz, at least, and… likely more.

Some studies have indicated the high end could be closer to 75,000 for some breeds, especially those with large, erect ears.  But, what does that mean? It means that dogs can hear many sounds we can’t of higher pitch, which is why the dog whistle, which is silent to humans, can be heard by dogs. They can also pick up sounds we can’t in everyday life such as noises on the TV, ambulances from a distance, and even additional sounds from the vacuum cleaner, which might explain why they may react in ways that don’t seem to make sense to us. They may be hearing something we can’t!  To be honest, I think the vacuum cleaner is annoying enough. I can’t imagine hearing even more annoying sounds when it’s on.

Their anatomy and increased sensitivity to those same higher pitches, it is thought that dogs can hear sounds that are about 4 times further away than we can. This is important: go back and read again.  Four times further away!  Again, this is why dogs may react to ambulances before we even hear them and continue barking or howling even after we are no longer able to hear the siren. They are also better able to tell the small differences in sounds that we may not be able to.  But, keep in mind, all of this also means that some noises that are not terribly loud or annoying to us may be very annoying or even painful to our dogs:  a good rule of thumb is if it is a loud and painful noise to us, chances are it is *even more* uncomfortable for your dog.

Why do dogs have such sensitive hearing?

We doctor types seem to guess evolution.

We know that dogs rely (for the most part) on scent/smells and sound to track their food and/or prey.  It makes sense that their hearing would be better at telling the high pitch sounds their prey may send out: even from further away, and from many directions. If a dog had to rely on a human’s ability to hear, it wouldn’t last very long in the wild on a hunt for food.

So, the next time your dog is playing in the yard and suddenly stops and perks up its ears, remember: There’s a whole world out there that we just can’t appreciate.

Dear Dr. Warford, What Can Dogs See, Anyway?

11 May

Dear Dr. Warford:

So what can dogs see, anyway? I’ve heard they are colorblind and only see black and white. Is this true? And why don’t they care about the tv? 

Signed- Just wondering

First let’s talk about what colors dogs can see. You’ve probably heard dogs are color blind. Well, that’s kind of true. Dogs have the same kind of colorblindness as most people who are colorblind. It’s called deuteranopia.  You see, we humans normally have 3 different type of cone cells in our eyes. These cells are responsible for the detection of color. In dogs, and some colorblind people, they only have 2 types of cone cells, yellow and blue.  As a result, they see red as a brownish-gold,  orange as lighter shades of gold-yellow, and green as shades of yellow-grey. They also can’t see violet, which to them appears as shades of blue or grey. This means dogs see the world in shades of brownish/gold, yellow, blue, and grey.  So it’s pretty impressive that they can fetch that red ball on the green grass, but we’ll get into why they are so successful at that a bit later.

Not only do they not have as many types of cones, they also don’t have the same number or concentration of cones as compared to people, so the intensity/brightness of the colors they see is also diminished. It is speculated that all of this happened with evolution. As we primates evolved, it was important that we could distinguish the full range of colors because we needed to be able to see them when foraging for food to distinguish what was safe to eat. In contrast, dogs hunted mainly at night, so the ability to distinguish color wasn’t as important as the ability to see well in low light, which brings us to the other type of cells in our and our canine friends’ eyes: the rod.

Dogs have many more rod cells in their eyes than humans. Rods can only discern black and white, not color, but they make dogs sensitive to many more shades of grey than humans and enable them to have much better vision in the dark. They also allow dogs to detect much tinier movements than we can and from much further away. They also have a reflective surface on the back of their eye called a tapetum lucidum, which reelects light, acting like a mirror allowing more light transmission and better night vision.  So you can see how these traits would be preferable in animals that needed to be able to catch their prey at night.

Dogs’ vision is estimated to be 20/75. This means they are unable to see as clearly as we are at a distance. A dog may clearly see an object only 20 feet away that a human could see clearly from 75 feet away.  But don’t feel too bad for our canine friends, because while we can only see about 180 degrees around us without moving our eyes, dogs can see an average of 240 degrees, more or less around themselves, which means they have a much better sense of what’s nearby.  Add that to their keen ability to detect movement from a distance and see more clearly in the dark thanks to those plentiful rods, and their ridiculously acute sense of smell, and it’s no wonder they are such great hunters.

Which brings us to the biggest question of all: Can my dog see what’s on TV? Well, yes, but is it the same? Until the new fancy high resolution TVs, it was likely that instead of seeing a continuous image, dogs only saw constant flickering, due to our differences in “flicker resolution.” I imagine this was not only not interesting, but pretty annoying for dogs to look at. Now, with the advent of higher resolution screens, dogs are likely able to see a continuous image, and more dogs do seem to “watch” tv, especially animals that are moving. But, keep in mind their limited color vision, decreased ability to discern detail, and the fact that tv has no smell, they often don’t associate the movements seen on tv as anything of interest, or at least not for very long.  So don’t worry, our advanced technology shouldn’t turn Rover into a soap opera addict while you’re away at work.

So next time you and Lola are playing fetch in your back yard with a tennis ball or a bright red/orange toy, be a bit more impressed! She (or he-no judging here) is relying much more on the movement and scent of the ball than the ability to see it.  Plus, you’ve gotten her off the sofa and out from in front of the TV! That deserves a treat!

Coming soon:

What Can Dogs Hear? What Can Dogs Smell? What Can Dogs Taste?

Also: What Can Cats See? What Can Cats Hear? What Can Cats Smell? What Can Cats Taste?

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*JD Warford, DVM, is the owner and operator of DC MetroVet. Check us out at www.dcmetrovet.com.

*Photos by Jen Sizer at https://www.facebook.com/FuzzyFacePhotography

The Feline Upper Respiratory Infection: It snot an easy fix

7 May

Over the last few months, I have received multiple questions related to feline upper respiratory infections. Rather than address them separately, I decided to give you a nice summary here, so pay attention. It’s a complicated and frustrating problem for vets and people owned by cats alike. Here’s why.

What are the common symptoms of feline upper respiratory infections?
-sneezing
-coughing
-discharge from eyes and nose
-conjunctivitis
-oral and nasal ulcerations
-fever
-loss of appetite
-loss of energy

What organisms cause these infections?
– there are several, which is part of the reason they are so difficult to manage
– feline herpes virus (rhinotracheitis)
– only survives for 18 hours outside host
– many infected cats remain carriers for life
– carriers may intermittently shed later in life at times of stress/illness
– carriers are sources of infections for other cats
– since it is a virus, antibiotics are not effective
– some say approx 1/3 of all cats are carriers of feline herpes virus
– calici virus
– most cats do finally clear the virus after several months
– many do remain contagious for months even though the illness has improved
– some remain carriers for life
– the virus can remain active for up to 10 days outside the host cat
– only bleach, not normal laundering, will kill it
– since it is a virus, antibiotics are not effective
– these two viruses account for a majority of infections, close to 90%
– don’t worry- these viruses are only infectious to other cats

Other possible causes of feline upper respiratory infections include:
– mycoplasma
– chlamydophila (formerly known as chlamydia)
– bordetella
-these account for generally less than 10% of feline upper respiratory infections
-these can be responsive to antibiotics, such as doxycycline, however, doxycycline can not be safely used in young, growing animals (such as kittens), complicating the treatment even further

More crappy news:
– infections may be caused by multiple organisms, which can obviously complicate treatment/recovery
– to further complicate it, there is no simple test to determine which organism is causing the illness, and some cats are infected simultaneously with multiple organisms

OK, so how do these illnesses spread?
-airborne (sneezing, coughing)
-fomites (objects carrying the organism such as bedding, toys, grooming utensils, and your clothes and hands that have been contaminated)
-crowded conditions (such as shelters and breeders) increase the likelihood of outbreaks
-stress or illness may induce a carrier cat (herpes virus) to show signs or begin shedding again

So, why are these illnesses so common?
– they are highly contagious
– 90% are viral, so there is no direct treatment available except for time
– carrier cats with no symptoms of illness can shed the infectious organisms for months
(calicivirus) or years (herpesvirus)
– stress (changes in household including new people, pets, construction, or moving) or other
illnesses may cause carrier cats to begin intermittently shedding for weeks (herpes virus)
– some organisms (calicivirus, remember?) can last for days outside of the host on bedding, toys,
etc, and aren’t deactivated by non-bleach detergents

Why are they so hard to treat?
– weren’t you paying attention?
– 90% of them are caused by viruses so like the common cold or flu, there is no effective direct treatment other than nursing care and time
– there is no simple testing to determine what is causing the infection, so treatment has to be aimed at the most likely causes and the symptoms
– there is no easy way to determine if and when a cat has ceased shedding the organism and is no longer contagious
– generally the time of exposure to illness is 2-7 days, so in crowded situations, many cats can get sick very quickly
– active illness generally lasts 7-10 days regardless of treatment
– upper respiratory infections can result in secondary pneumonia, which can be life threatening

Well this sucks. How can I prevent an upper respiratory infection in my household?
– short answer, you can’t
– many cats become carriers (therefore infected and/or contagious) before they reach your house
– many cats that are carriers/contagious are not showing any symptoms of illness at the time of
adoption
– many cats that are carriers/contagious remain so for weeks, months, or even a lifetime, even in
the absence of obvious symptoms of illness
– there is no simple test to determine if your cat is infected, contagious, or a carrier of an
upper respiratory infection

Well that sucks too. So what can I do to prevent infection?
– short answer, again, you really can’t (have you been paying attention?)… but…
– vaccinate- herpes and calicivirus are part of the feline “distemper” vaccination and vaccinated cats are less likely to develop illness if exposed or may have less severe symptoms if they do become sick
– isolate new cats (not just obviously sick ones)- just remember, some cats are carriers for months or for life, and do not show obvious signs of illness, so this will not be 100% effective
(this is also a good idea in general- intestinal parasites are also very contagious, so until you have had an exam by a veterinarian and a stool check for parasites, you should never allow new cats to come in direct contact with other cats in the house, especially sharing litter boxes)
– wash all materials in bleach that have come into contact with a sick cat (not entirely practical or possible, considering your carpet, furniture, and hands are likely included in that)
– try to minimize stress and be aware stress or illness may cause a carrier cat to become sick again and/or begin shedding the infectious organism again, for weeks or months

Well crap. My cat has an upper respiratory infection… what should I do?
– If you have multiple cats, separate the sick cat as soon as you notice symptoms. Even though this will not likely prevent the spread of infection at that point, it may help minimize it.
– Make sure all other cats’ vaccinations are up to date.
– Have the sick cat examined by a veterinarian, especially if there is lethargy, loss of appetite, severe congestion or conjunctivitis, or coughing. While the underlying organism may not be directly treatable, many of the symptoms can be managed with medications such as anti-histamines, decongestants, eye medications, immune supplements, and appetite stimulants. Your vet may also be able to give you tips about home care (such as steamy shower therapy for congestion.) It is also smart to determine if there are signs of secondary pneumonia, which may require antibiotic treatment to prevent severe or even fatal infections. Kittens, due to their immature immune systems, are especially susceptible to severe complications due to upper respiratory infections.
– Never give any over the counter medications to your cat without a veterinarian’s recommendation. Many over the counter medications are toxic to cats. Also, cats and esp kittens require very small doses of the medications they can safely take.

So it sounds like there really isn’t any way to be positive my cat will never be exposed to an upper respiratory infection… is there any good news?
– Yes! Most cats with upper respiratory infections are able to successfully overcome the signs of illness and do not have any obvious long term health problems. But remember, some may remain carriers for months or even a lifetime. So, although respiratory infections are almost impossible to contain and prevent, in otherwise healthy cats, they are usually nothing more than annoying outbreaks (much like a common cold or flu in people) that do not impact the cat’s overall quality of life in the long run. What makes them different from the common cold and flu is the fact that many cats remain chronically infected carriers for months or years even after recovering from the signs of the infection.

I told you. It snot fun.