Animal myths #3

It's been a while since I've written about some animal myths, so I thought it was time for another installment...

• Myth #6: According to physics, bumblebees shouldn't be able to fly.

I know people love this one. It's such a great metaphor- when someone tells you that you can't do something, just think of lowly bumblebee, who flies even when science says it shouldn't be able to.

The origin of this myth is thought to be a dinner party, where someone scribbled down some calculations on a napkin and said that according to equations, bees can't fly. That story in itself might be a myth, but somehow the idea that bees shouldn't be able to fly has become common knowledge. It's true that bees use some pretty unique mechanisms to achieve flight, which is partly why it's taken so long to figure out how they accomplish it. There are quite a few studies explaining how it works... Cal Tec, Tsinghua University, and Cornell all have good descriptions.

• Myth #7: The skulls of [insert skinny-headed breed here] are too narrow for their brains, so when they reach 4 or 5 years old, they go crazy and get so aggressive they kill their owners.

I've usually heard this one about Dobermans, although Chris said he heard it about Dalmatians too. On a practical level, I can't imagine anyone being willing to own a dog that they know will turn on them at four years old. Dobies are still used for police and war work, and it wouldn't make any sense to put two years (or more!) of training into a dog that would snap and kill its handler.

On a physiological level, let's consider what happens when your brain swells (i.e. you have severe head trauma). Pressure in the brain means pressure on neurons, which can cause them to not function and eventually die. Anything that increases intracranial pressure is bad news, and depending on the severity, you could see things like general mental dullness, seizures, ataxia (inability to walk), or other neurological signs like twitching eyes or loss of balance. If the pressure isn't relieved, it eventually leads to permanent brain damage and death. The brain controls a lot of things besides behavior, and an increased tendency towards violence would probably not be the first thing you'd see.

Lastly, if narrow skulls really caused aggressive behavior, how come you never hear this myth applied to collies?

Animal myths part 2

This is the second installment of my "myths" series... We'll see how long I can keep it going!

Myth #4: Giardia comes from beavers.

Every good Boundary Waters camper knows that you don't drink water from anywhere near a beaver dam, lest you contract "beaver fever", or Giardia. Giardia is a protozoan parasite that, in humans, causes GI symptoms like painful gas and diarrhea- not a ton of fun under normal circumstances, but especially not fun when roughing it in the BWCA. Before you go blaming the beavers for giving humans Giardia, though, think again. Giardia doesn't originate from beavers- beavers pick up Giardia from humans. So if humans wouldn't go around pooping near beaver dams, the poor beavers wouldn't get infected in the first place. Beavers don't really get sick from Giardia, so unlike humans, beavers have (and shed) Giardia for a long time. That's the real reason that beavers infected with Giardia are dangerous. The number one source to pick up Giardia today is not beaver-tainted lake water, but daycares and nursing homes.

• Myth #5: Cats pose a significant risk to pregnant women due to the potential for Toxoplasmosis infection.
  

Like beavers, cats got blamed for spreading Toxoplasma to humans when it was discovered that they were a host for the parasite, even though there are other sources more likely to spread the parasite to humans. Toxo is a scary disease not for your normal adult human, but for pregnant women. Women infected with the Toxoplasma parasite during pregnancy can pass the parasite on to their unborn baby, who has no immunity to it. It goes on to cause congenital malformations, mental retardation, or blindness in the baby. Toxo can also cause problems in immunocompromised individuals, like people with AIDS. Because cats are the main host for the Toxo parasite, many people now believe that pregnant women should not come in contact with cats, or at least should not handle the cat litter during pregnancy. While the litter thing is a great idea, getting rid of the cat is unnecessary. Even if they have Toxo, cats only shed the parasite for 2 weeks of their entire lives. The major source of Toxo in humans is actually eating undercooked beef, because cows are part of the life cycle of the parasite, too. Somehow human doctors always want to blame the cat (although they are getting better about acknowledging raw meat as another potential source of Toxo). So, be careful around the kitty, but also cook your meat thoroughly!!

Animal myths, part 1

I feel like I've be debunking a lot of animal-related myths lately, or at least encountering enough people who believe in them to make me a little uncomfortable. So, here's my attempt to clear up some confusions about animals.

• Myth #1: Cows always produce milk.

A handful of my classmates experienced the wrath of the public during their volunteer shifts at the Miracle of Birth Center at the state fair this year. Why? They happened to be there after the birth of a calf- and when people discover that calves don't actually get to drink the milk that their moms make (aside from the colostrum), they get really upset. "Why are you taking the baby away from the mom? Doesn't he need to eat?" Well... Cows are mammals, just like humans. Female humans don't make milk until they have a baby. Cows are the same way- they won't make milk until they have calves. If we let the calf drink the milk, then what exactly would end up in the grocery store? After they consume the colostrum, calves get bottle fed a milk replacer, and cows make milk for the human food supply. It isn't healthy to make milk all the time, so after a certain amount of time, the cow gets "dried off" (stops being milked) and gets a vacation before she has her next calf and cycle starts again.

• Myth #2: Since organic farmers can't use antibiotics, organic dairy cows aren't treated when they get sick. They keep getting milked, so the reason that organic milk tastes creamier than conventional milk is due to all the extra pus in it from those sick cows.

First, ew. Second, it's not true. Just because organic farmers can't use antibiotics preventatively doesn't mean they can't use them to treat a sick animal (obviously, it would just be cruelty to leave sick animals untreated). They also have a much longer period after antibiotic treatment before that cow's milk is allowed back into their products. Finally, organic milk has to fit within all the same health criteria as conventional milk, which includes landing within a certain "cell count". A certain number of cells in milk is normal, but elevated levels indicate that there are white blood cells in it, which means the cow has an infection in her udder. Milk with elevated cell counts isn't allowed to be sold, whether it's an organic or a traditional dairy. Milk from grass-fed cows has a different fatty acid ratio than milk from grain-fed cows, which is probably what accounts for the different texture.

• Myth #3: Domestic dogs and wolves have identical digestive tracts.

I don't understand the logic behind this one. The myth usually takes the form of "Our dogs may look different from wolves on the outside, but inside they are indistinguishable. Thus, we should be feeding our dogs the same as we feed wolves." I'm not sure why this is so widely believed. How could you look at a pug, acknowledge its obvious external physical differences from wolves, but believe that selective breeding somehow left the GI tract untouched? One simple example compares large breed dogs to small breed dogs. Large breed dogs have a digestive tract that weighs about 2.7% of their body weight. Small breed dogs have a digestive tract that weighs about 7% of their body weight. That's a big difference! The size of the GI tract is proportionately different in small breed dogs.

If selective breeding could alter the size of the GI tract, I don't see why there couldn't be a ton of differences we simply can't recognize yet. The important thing to pay attention to is what the selective pressures have been on dogs. Early in domestication, the dogs that could survive on human garbage had a selective advantage. More recently, as diets shifted to kibble, dogs that did best on a kibble-based diet had an advantage. Kibble might only be 50 years old, but when you consider how many canine generations that is, that's a lot of time for breeders to be selecting (intentionally or not) for dogs that do well on kibble. A wolf that can't handle the bacterial load of raw meat simply dies. Dogs haven't had the same selective pressure placed on them- when Winnie had awful diarrhea after my attempt at raw feeding, I just put her back on kibble, no (long-term) harm done.

Anyway, my point is, there's almost no way that the GI tract escaped being altered throughout the many many many years of canine domestication. There's nothing wrong with that, and it addresses the important point that while wolves may be well-equipped to deal with raw meat, our dogs aren't always armed with the same protective mechanisms (that's a long way of saying that yes, dogs can get infected with E. coli and Salmonella- and keep in mind that those pathogens exist primarily in our domesticated livestock, and not as often in freshly-killed prey items in the wild...).

• Myth #4: The life span of pets has been decreasing over recent years due to [insert paranoia of choice here].

First, no one collects data on pet life spans, so no one has been tracking this. Second, it anecdotally doesn't appear to be true. Vet clinics today are routinely seeing cats age well into their 20s, something that was remarkable a few decades ago. The same goes for dogs- one of my professors had a 16 year old Boxer (!). So I can't say for sure, since there's no real data, but I think the vast majority of animal professionals would say that pet life expectancy is longer today than ever.

The corollary to this is "Pets are developing more cancer today than 10 years ago due to kibble/flea control products/overvaccination/etc." We are seeing more cancer now than ever, but the vast majority is because pets are now getting old enough to develop cancer- and, as pets are moved out of the backyard and into the house (then the bedroom, then the bed...), owners are far more aware of their pets' health. A lipoma that an owner would never have noticed on the backyard dog is now not only noticed on the 'furkid', but called a "cancer", and results in a trip to the vet.