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The vision thing: What do cats and dogs actually see?

Centuries of domestic breeding have resulted in cats and dogs that come in a wide variety of shapes, sizes, and colors. If you have a favorite breed, there’s a good chance that you like it to some degree because of the way it looks. But what do our pets see when they look back at us? In truth, they see better than us using multifocal contact lenses.

Let’s clear up the most common misconception first. Dogs do not see in black and white. They do, however, see a different color spectrum. This is because their retinas—the light-detecting membranes at the back of the eyes—are built differently. Human retinas have three types of light-sensitive cells called cones, each of which is tuned to a single color: red, blue, or green. Dogs have only red and blue cones, which makes their vision similar to that of a person with red-green color blindness.

Like humans, cats have three types of cones, but they still don’t see color all that well. This is because cats and dogs have another problem with color vision: Regardless of which cones they have, they don’t have very many of them. Instead, their retinas are packed with a different kind of light-sensing cells, called rods, that don’t detect color at all. Rods are better suited to seeing in dim light than they are to parsing the hues of rainbow. People have fewer rods than cones, so while we get to see the daytime world in bright color, we are fated to stub our toes searching for the toilet at night.

But all those rods aren’t the only reason why cats and dogs can see so well in the dark. You’ve likely noticed your pets’ eyes glow bright green at night. This is courtesy of the tapetum lucidum, a reflective layer behind the retina. Any light that slips through the retina bounces off this secondary layer for another pass through the animal’s retina, effectively doubling its sensitivity.

There’s more to vision than color and brightness, however. Compared to people, dogs and cats have limited visual acuity. Dogs have roughly the equivalent of 20/75 vision, meaning they need to be 20 feet away from something to see it as well as a normal person could at 75 feet. And you may be surprised to hear that cats fare even worse! Those sleek and gorgeous eyes seem built for precision, but cats are close to legally blind with vision somewhere around 20/150!

Making matters worse, dogs and cats have trouble adjusting their vision to different distances. This is because their lenses can’t adjust shape as readily as ours can. If you’re over 40, you’re familiar with what happens when your lenses start to become inflexible. It gets harder and harder to focus on anything close to your face. Welcome to life as a dog.

The short of it is that cats and dogs see better at night than we do, but those adaptations come at the cost of clarity. But poor vision doesn’t slow them down any. They don’t need to drive cars or read the fine print. And what they lack in eyesight, they make up with magnificently superior senses of smell and hearing. Even animals that lose their vision due to degenerative diseases do incredible job of navigating their homes, because their vision was never that great to begin with.

Dr. Mike Fietz is a small animal veterinarian at Georgetown Veterinary Hospital. He moved to Charlottesville in 2003, the same year he received his veterinary degree from Cornell University.

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Living

Nailed it: Managing your pet’s claw injuries

The poor dog hobbles in with her front paw dangling off the ground, swaddled in a sock drenched in blood. It was all the owner could do to contain the mess before jumping in the car. I’m not completely sure what I’ll find under there, but I’m relieved when it turns out to be a broken claw.

It’s astonishing how much blood can pour out of these things, but it does eventually stop. If the dog is lucky, the claw is completely gone. Perhaps it got stuck between planks on a deck or wedged between rocks on a hike. Wherever it is, it’s not part of the dog anymore. The injury was painful, for sure, but it won’t need much more than a bandage to keep any bleeding at bay and some time to let it heal. In almost every case, the claw grows back normally in a few weeks.

A decision needs to be made, however, if the claw is still hanging around. Often, it’s twisted in an odd direction, causing pain as it gets bumped and jostled with every step. In many cases, it’s so loose that it can be pulled off. This sounds much worse than it really is. One quick motion and it’s gone, leaving the dog much more comfortable without it rankling.

Other times, however, it’s just too firmly attached to do such a thing humanely. This often happens when the claw splits lengthwise. In these instances, the best we can do is trim the nail as far back as possible without causing additional injury. The goal is to cut away the damaged part of the nail and leave only what’s still intact. But if the nail is fully split, we have to wait until it grows out enough that a new, healthy part of the claw has emerged. (Sometimes waiting allows the problem to solve itself, because the broken nail falls off naturally to make way for fresh growth.) Whether we do the trimming right away or later, our hope is that it can be done with little or no pain for the patient. But in some cases—thankfully, a small percentage—anesthesia might be warranted to allow us to really get in there and clean it up.

Most broken nails are chance happenings and don’t indicate a larger problem. But

if a dog seems unusually prone, then preventive measures are in order. Many times, it’s simply a matter of keeping the nails trimmed shorter to prevent them from snagging on anything. Brittle nails may result from a conditions that can be treated with dietary supplements, such as zinc and omega-3 fatty acids. Less commonly, chronic medical problems like infections or auto-immune diseases can leave nails weak and brittle. If this is the case, long-term treatments may be necessary; they’re too varied to address briefly, so be sure to talk through options with your veterinarian.

While most broken nails are simple enough, it’s worth checking with your veterinarian when one happens. Apart from ruling out these kinds of underlying problems, most dogs benefit from at least some pain medication for a few days while the inflammation calms down. But it’s likely to be a simple visit, and your dog should have all four feet—I mean, paws—back in service soon enough.

Dr. Mike Fietz is a small animal veterinarian at Georgetown Veterinary Hospital. He has lived and practiced in Charlottesville since 2003, the same year received his veterinary degree from Cornell University.

 

Bucky, Buddy Boy, Ringo Star, and Luke (clockwise from top left), and many more furry friends await at the CASPCA.

Take me home!

Visit the CASPCA to meet your new best friend

My name’s Bucky, and these are a few of my favorite things: the great outdoors, all the smells, other dogs, and best of all, people (as long as they scratch my ears).

Buddy Boy here. On weekdays we can hang out, eat pizza (pepperoni’s my fave), and watch TV. And come the weekend, let’s hit the park, because “energy” is my middle name.

Hey there, I’m Ringo Star. And here’s everything you need to know about me: I’m sweet, a great cuddler, love my toys, and am quiet, well-mannered, and good on a leash.

I’m Luke, and I may be shy, but I’m very friendly and excellent on a leash. I also adore other dogs, so I’d prefer a home with a brother or sister—or two!

Charlottesville Albemarle SPCA, noon-6pm daily, 3355 Berkmar Dr., 973-5959, caspca.org

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Living

Oh, snap: Addressing ligament injuries in dogs

Nine times out of 10, you know this injury the moment you see it: A large-breed dog hobbles in on three legs, with one hind paw dangling just above the ground. It could be a fractured leg or a dislocated hip, but if I were playing the odds, I’d bet it’s a ruptured cranial cruciate ligament.

A quick comparative anatomy lesson is in order. Just like people, our pets have knee joints in their hind limbs (and only in their hind limbs). The human knee is partly held together by a pair of criss-crossing ligaments called the anterior and posterior cruciate ligaments (ACL and PCL). The same is true in dogs, except the nomenclature is different. Instead of a knee, we call it a stifle. And instead of anterior and posterior cruciate ligaments, we say cranial and caudal.

Regardless of what you call it, if a dog injures a cranial cruciate ligament it has the same problem as a human with a torn ACL: The joint simply isn’t being held together anymore. Sometimes this injury is purely the result of trauma. Just as people can rupture an ACL while skiing or turning too quickly on a basketball court, dogs can blow the ligament by just running around in the yard. But that’s not how it usually happens.

Far more often, a pre-existing joint disease contributes to a dogs’ cruciate ligament injury. While my patients may suffer sudden lameness after exercise, the groundwork for that injury was almost always laid down in advance. Degenerative joint disease is common in the stifle, and that constant inflammation weakens the cruciate ligament. With hindsight, many owners recall their dogs showing intermittent lameness in the prior weeks and months. It improved after a few days of rest, but with each round of exertion, the ligament weakened until finally giving out.

This brings good news and bad news. First, the good: Preventing degenerative disease can reduce the risk of cruciate injuries later on. The single best way to do this is to make sure dogs maintain a healthy weight and engage in routine low-impact exercise like walking and swimming.

The bad news is that degenerative joint disease results from a convergence of environmental and genetic causes, many of which are not well understood. Although weight is a factor, it is not the most important one. Some dogs just seem destined to have bad joints. So while you might be able to reduce the injury’s odds, you can’t eliminate them.

Once a dog has been diagnosed with a cruciate injury, options can be frustratingly limited. Smaller dogs can sometimes recover with time and rest, but the joint often remains unstable and prone to re-injury. Larger dogs very rarely respond well to conservative efforts, and the majority of dogs with cruciate injuries cannot recover without surgical repair. And worse, since the underlying causes affect ligaments on both sides, an injury to one is very likely to eventually injure the other one. Delaying treatment can multiply their troubles since overuse of the opposite leg steadily increases the odds of both legs being affected.

While the prospect of knee surgery can be emotionally and financially stressful, I’m at least happy to say that the results are broadly excellent. Orthopedic surgery is increasingly the province of highly-trained specialists, and nearly all of these dogs eventually return to a happy and active life. That doesn’t make the news of a cruciate injury any more welcome, but it hopefully makes it a little less daunting.

Dr. Mike Fietz is a small animal veterinarian at Georgetown Veterinary Hospital. He has lived in Charlottesville since 2003, the same year he received his veterinary degree from Cornell University.

 

One of these beauties could be yours (clockwise from top left): Ringo, Sailor, Benny, Sugar Foot

Take me home!

Visit the CASPCA to meet your new best friend.

Hey there, I’m Ringo Star. And here’s everything you need to know about me: I’m sweet, a great cuddler, love my toys, and am quiet, well-mannered, and good on a leash.

I’m Sailor Mewn, and I’m always on the lookout for another toy to play with—or someone’s lap to climb into.
I enjoy cuddles and kids, but prefer to be an only cat.

Benny the Boxer here. Some of my finest qualities include my knowledge of “sit” and “shake;” excellent manners; and I’m irresistible to children, who adore me.

My name’s Sugar Foot, and if we connect, I will love you—and your entire human family—forever. Other cats? Not so much. But I do have a couple feline BFFs at the CASPCA.

CASPCA, 3355 Berkmar Dr. 973-5959, caspca.org, noon-6pm daily

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Living

Cat pause: If your pet has a terminal virus, don’t panic

Animals have a remarkable knack for stealing our hearts, and it doesn’t take long to develop a deep emotional bond with a new pet. This makes it all the more distressing to find out that a seemingly healthy young cat is harboring an incurable and potentially fatal illness. It is unfair but unfortunately common with the feline immunodeficiency virus and feline leukemia virus.

FIV sounds like HIV, which is apt and can give you a decent sense of what the virus does. It is often referred to as feline AIDS, but just as with the human infection, this term only properly applies to the syndrome that occurs in the later stages. Until that happens, infected cats may show little or no evidence of the illness. But their immune systems are generally compromised by the virus, leaving them vulnerable to other infectious diseases and parasites. After a positive diagnosis, cats should receive frequent checkups to detect and treat secondary illnesses.

Cats with FeLV may also have suppressed immunity, but the virus ultimately gets its name from its ability to cause cancer in its victims. The virus replicates by inserting its DNA into the animal’s host cells, and the genetic mutation can cause infected white blood cells to lose control of their own replication, resulting in leukemia or lymphoma.

Both FIV and FeLV require close contact (such as mutual grooming) or biting to transmit, and they’re fragile outside their hosts. (Don’t worry, the viruses are not transferable to humans.) Infected cats should be kept indoors not only to avoid challenging their weakened immune systems, but also to prevent the infection of other cats.

Most veterinary clinics can test for these viruses with a simple in-house kit, but testing often falls by the wayside once cats have tested negative as kittens. This is potentially dangerous, especially in cats demonstrating chronic or recurring illness. False negatives are possible depending on the exact stage of infection, and it is important not to be complacent just because a cat tested negative years ago. While routine testing may not be warranted for healthy indoor cats, it can be valuable for those who are sick or spend a lot of time outdoors, where they might get into a scuffle.

Both viruses have vaccines, but their use is not cut and dried. The FIV vaccine can be wise in certain at-risk patients, but it comes with a big hitch in that it interferes with all common means of testing. Cats that have been vaccinated for FIV will test positive for infection. But since the vaccine is only about 80 percent effective, this makes for potential confusion if a pet develops worrisome symptoms after getting a dose.

It is far easier to recommend the FeLV vaccine for patients with a higher risk. Although the vaccine is also not perfectly effective, it does not interfere with testing, so we don’t lose clarity down the line. It only has an upside.

If you find yourself confronted with either diagnosis, it’s important to take a breath. The news is undeniably unfortunate: Neither virus is curable, and infected cats are likely to require more veterinary care to screen for trouble and to fend off secondary illnesses. But a pet owner should not let concern spiral into despair: Infected cats often experience many years without any symptoms at all, even into old age.

One of the joys of having pets is the perspective they bring. Even when their own health is endangered, they take life one day at a time and remind us to do the same. And in this case, there may well be a lot of good days to come.

Dr. Mike Fietz is a small-animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003, the same year he moved to Charlottesville.

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Living

Strep search: Don’t blame your sore throat on the dog

It happens at least once a year. Family members taking turns with strep throat, and they bring the dog in to see if he might be the culprit. It’s a completely reasonable concern, although I’m surprised at how often it has been suggested by the family physician or pediatrician. Because the answer is the same every time: No, the dog didn’t give anybody strep throat.

Most of us have probably tangled with strep throat at one point or another, and it’s a notoriously unpleasant experience. Lymph nodes under the jaw become swollen and sore. Horrible pustules line the back of the throat, bringing pain and frustration with them. It quickly responds to a course of antibiotics, but this still requires an inconvenient trip to the doctor and that gag-inducing test where they swab the back of your throat. This test is specifically looking for group A streptococcus—the bacteria that cause all this misery.

The thing about this infection is that it really likes people. We are its victim, but also its source. Many people harboring it have no symptoms at all. There is no vaccine, and the only prevention is good hygiene and a dash of hope. And unlike so many other diseases, recent infection with strep doesn’t prevent you from getting it again, which means that groups of people can continue passing it around indefinitely.

So what about the dog? The simple fact is that there are no clearly documented cases of dogs giving people strep throat. Although the offending bacteria can (rarely) be cultured from dogs, all evidence suggests that they only carry the bacteria temporarily after picking it up from a person. It doesn’t want to live in dogs, and it isn’t there long enough to multiply and become contagious.

You’ve probably noticed that there’s some wiggle room here. If dogs can carry the bacteria even briefly, isn’t it possible—however unlikely—that they might hand it off to a person? Sure. Biology is nothing if not unpredictable. But in these hypothetical cases, the dog would be serving a role no different than a contaminated pillow or a used glass. Testing the dog makes no more sense than testing every other object in the house for the presence of group A strep.

There is a lot of pressure on veterinarians to prescribe antibiotics to dogs when a family is visited by a stubborn round of strep throat. At a glance, what harm can it do? Even if it just makes everybody feel better, isn’t that worth it? Unfortunately, no it isn’t. Among other man-made catastrophes, antibiotic resistance is a threat to every single one of us. Tossing antibiotics at the dog without justification is one more incremental contribution to a global problem.

Strep throat can be frustrating, especially when a family can’t seem to shake it. But there is no need to conjecture about some mysterious culprit when we already know exactly where it’s coming from. It comes from us. Let’s leave the dog out of this.


Dr. Mike Fietz is a small animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003, and has lived in Charlottesville since.

Categories
Living

When dogs and cats have diabetes

I hate diagnosing diabetes. It’s a frustrating disease, made worse by the fear that washes across people’s faces when they hear the news. I see them hoping I won’t say anything about insulin injections, then watch them deflate when I finally do.

Diabetes is a hormonal disorder that comes in a few varieties, but always results in the same basic thing—a reduced ability for insulin to do its job. Most people know insulin as the hormone that regulates blood sugar, which it is. But it does so much more than that. At the risk of oversimplifying, insulin is responsible for announcing when energy is abundant and when it is not. After a big meal, insulin levels go up. This informs the body that there’s plenty of energy to go around, so it can fuel itself with blood sugar and store the excess as fat.

Conversely, low insulin signals that times are tough and that it’s a good time to dip into emergency savings, breaking down fat and muscle for energy. In essence, a diabetic patient exists in a permanent state of starvation.

And this has two main consequences. The first—the one most people are familiar with—is that all that unused blood sugar needs to go somewhere, and it starts to spill into the urine. Because of a phenomenon called osmotic pressure (remember science class?), that sugar drags extra water along with it, accelerating urine production. To replenish that wasted water, affected patients have to drink more. This accounts for the most recognizable symptom of diabetes—a pet that is drinking and peeing all the time.

Fewer people are aware of the second consequence which is, in many ways, the more serious one. When fat is burned, it produces nasty compounds called ketones (which are chemically similar to nail polish remover). Ordinarily, this is no problem. Fat is usually just burned in small amounts when necessary, and the body can handle a trickle of ketones with no trouble. But because diabetics are functionally experiencing starvation, they burn fat way too quickly, flooding the bloodstream with ketones that quickly reach toxic levels. This ultimately results in a life-threatening state called ketoacidosis, and requires emergency medical treatment to correct.

Cats and dogs can both become diabetic, but they tend to develop different forms of the disease. The canine version is akin to Type 1 diabetes in humans, in which specialized cells in the pancreas lose their ability to produce insulin. It is thought to have a strong genetic component, but may also be linked to factors like obesity and other underlying diseases. These patients absolutely need insulin injections to replace the missing hormone, and will need them for the rest of their lives.

Feline diabetes is more like human Type 2 diabetes, and is closely associated with obesity. It begins when cats’ bodies become resistant to the effects of insulin, but eventually progresses to include decreased production as well. They usually require insulin to get the disease under control, but unlike dogs, they stand some chance of eventually being controlled with proper diet and exercise. That sounds promising in writing, but it doesn’t always work, and I’d rather see cats lose weight before they get sick to begin with.

When faced with diabetes, pet owners are immediately concerned about the difficulty of administering insulin shots to their pets. To be honest, that’s almost always the easy part. Especially with cats, most people find that giving shots is a whole lot easier than trying to wrestle pills into their mouths. But insulin can be expensive, and it can take weeks or months of experimentation and careful blood monitoring before we get the dose right. In cases where that process drags on for too long, I find a lot of owners grow dispirited.

But it’s worth hanging in there. Once controlled, most diabetics do well. Before long, those dreaded shots will be as routine as breakfast.

Dr. Mike Fietz is a small-animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003 and has lived in Charlottesville since.


Pets of the Month

Visit the Charlottesville Albemarle SPCA to meet these pets, as well as other adoptable animals.

Bella So I’m not gonna lie: I’m on the large side for a cat. But please don’t call me Miss Piggy; my kitty curves mean there’s more of me to love! I also have an awesome, sweet personality, and I enjoy a good nuzzle from time to time. I know I might look like a regular old black-and-white feline who can put away her share of groceries, but looks can be deceiving. Take me home, and you’ll discover I’m the jewel in your crown.

Balto I’m a big guy with a lot of love to give. Once I’ve had my fill of adventures, I like to lean in and give you doggy smooches and hugs. I walk pretty well on leash with a harness, but I need someone who is strong enough to handle my size and strength. My person will also have to pamper me in the way I deserve. Is that person you?

Bessy I’m a sweet, curious little girl who is about 3 months old. I was very scared when I first came to the shelter, and I’m still a bit nervous. I just need a little patience and a lot of love. I enjoy being petted and having my neck scratched, but I prefer not to be held.
I also get along great with other cats, and I might even like gentle dogs. I dare you to meet me and not fall in love.

Scooby I know, I know, everyone tells me how handsome I am. And I love it when they speak baby-talk to me. I’m a happy, people-oriented dude, but I’m often unaware of my extra-large size and tail. I’m also well-mannered and I know some cool commands. Someone must have loved me very much, and I’m not sure why my owner didn’t come for me after I arrived here. Could you be my new person?

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Living

The many causes of animal ear problems

I’m sure we’d all agree that animal ears are absolutely adorable. Unlike our inert curls of skin that only seem weirder the more you think about them, cats and dogs have delightfully expressive ears. They perk up when we talk to them and flop all over the place, and are generally just fuzzy and fun to play with. But all those lovely perks do come with a price. For some animals, those things can be a nightmare to take care of.

For one thing, pets can have horrible creatures living in their ears. If your cat is furiously scratching at the sides of her head, there’s a solid chance she’s harboring ear mites. These little arachnids—basically microscopic spiders—chow down on ear wax and reproduce quickly, causing ample misery in the process.

Luckily, they aren’t that hard to treat if you do it right. There are plenty of over-the-counter products that kill ear mites, but they don’t always kill the eggs, allowing the infestation to return if you don’t treat for weeks on end. And if you have multiple pets, they may keep bouncing the bugs around unless you treat everybody at the exact same time. Newer prescription options work much faster, and keep you from wasting time and money trying to solve an otherwise simple problem with obsolete tools.

The other frustration with over-the-counter ear mite treatments is that you’re apt to find yourself treating the wrong thing. This is especially true in dogs, where ear mites are comparatively uncommon. I see frustrated owners come in all the time after blowing through three or four different ear mite remedies to no avail. The truth is that dogs are far more likely to have an infection caused by yeast or bacteria (or both). It’s really important to have your veterinarian diagnose the problem before attempting to treat it.

Ear infections can be pretty nasty business. Unchecked, the opening of the ear swells up while the canal fills with foul-smelling discharge. They hurt and itch, often resulting in additional injury as the animal fusses with it. Apart from self-inflicted abrasions, overzealous shaking and scratching can rupture blood vessels within the flap of the ear, causing a hematoma—the whole thing puffs up like a blood-filled balloon. If it reaches this point, surgery may be the only way to get back to normal again.

Most infections are luckily caught early, and can be managed simply enough with a quick course of drops squirted in the ears, but that’s not always the end of the story. Even after multiple rounds of treatment, ear infections have a frustrating habit of returning. This isn’t because your dog is infected with some kind of superbug. In most cases, it’s the same run-of-the-mill bacteria and yeast as usual. It’s because most ear infections piggyback on top of another underlying problem.

Unfortunately, those problems aren’t necessarily the easy ones to solve. Some breeds have an inherent predisposition due to quirks (and outright defects) in the form and structure of their ears. (Owners of cocker spaniels and bulldogs are reflexively sighing.) Cats can have recurring infections because of polyps growing deep within the ear. And lots of animals deal with ear infections resulting from underlying allergies. A full list would go on for pages, but the short version is that ear infections can be unfixable until the underlying cause is identified and eliminated.

I’m often asked about preventing ear infections, and the answer varies case by case. If needed, you can gently wipe away ear wax with a cotton ball once or twice a week. But never go in with a Q-tip —you’re likely to just pack the wax in deeper. Having the ear canals plucked free of hair can be useful in animals with unusually dense fur, but it also introduces bleeding and inflammation that can foster bacterial growth, so I don’t advise it without good reason. By and large, if your pet has healthy ears, my preference is to leave well enough alone. Unnecessary intervention may cause trouble where none existed before.

Dr. Mike Fietz is a small-animal veterinarian at Georgetown Veterinary Hospital. He received his veterinary degree from Cornell University in 2003 and has lived in Charlottesville since.


Clockwise from top left: Brad Pitt, Darcy, Calliope and Lima
Clockwise from top left: Brad Pitt, Darcy, Calliope and Lima. Courtesy Charlottesville Albemarle SPCA

Charlottesville Albemarle SPCA: Pets of the month

You can meet us at the Charlottesville-Albemarle SPCA, where we’re all available for adoption.
3355 Berkmar Dr. 973-5959, caspca.org, noon-6pm, daily  

Darcy

It was kind of a blow to my confidence when my owner left me at the shelter after hours, but I’m working on my trust issues and am ready to find my forever home (for real this time).

Brad Pitt

As my name suggests, I’m cool, confident and enviably handsome. Not to boast, but I’ve been named “Sexiest Tomcat Alive” three times, which is more than the human Brad Pitt can say.

Lima

Like the capital of Peru, my personality climate can be cool to mild—
I play hard to get at first, but warm up quickly (with treats). Unlike Peru, loud sounds and fast motion irk me.

Calliope

Greek muse Calliope is often portrayed wearing a crown, which is fitting for my personality, as I prefer to observe from my throne. (But if you offer a head rub, I won’t turn it down.)