Sunday, July 14, 2024

Sydney the dog took a ride on the new green line extension from Somerville to North Point Park in Cambridge on Feb. 19. (Photo: Jeanine Farley)

We all know domesticated dogs are not wild. But they did descend from wolves – not gray wolves, as many people think, but rather now-extinct Eurasian wolves. DNA evidence suggests that dogs broke off from Eurasian wolves between 15,000 and 30,000 years ago. It’s not known how dogs became domesticated, but it likely happened gradually. Perhaps wolves ate food scraps humans left behind; people may have started feeding wolves to encourage them to stay nearby for protection. Eventually, humans raised wolf pups and bred them to encourage favored traits. This all probably happened gradually, over thousands of years.

There are some wild canines in Cambridge and Somerville – such as foxes and coyotes – but mostly we have domestic dogs descended from Eurasian wolves that retain some features of wild canines.

A corgi at the Somerville Dog Festival on Sept. 24. (Photo: Bill Trudell)

Did you know that dogs have special taste buds at the tip of the tongue to identify water? Although humans often describe water as having no taste, dogs notice subtle differences between water from different sources. My dog, for example, is a very picky water drinker and will drink only cold, fresh tap water, preferably from a glass bowl. Once the water warms up, she doesn’t drink it. She also has a great affinity for water in mud puddles, but she absolutely will not drink the water that business owners put out on the sidewalk for thirsty dogs. 

It is not known why dogs prefer some water over others, but it is known that most dogs prefer cool water over warm and moving water over stagnant. Many dogs like water with minerals in it. Some dogs may not like chlorinated water. Remember, however, that even though dogs might like puddle water or pond water, they can get leptospirosis or parasites from it; a city puddle might also contain fertilizer runoff or road chemicals. Blue-green algae in pond water can also make dogs very sick. 

Sled dog Monty is eager to pull near Worcester on Jan. 29 of our year of endless snow – 2015. (Photo: Jeanine Farley)

Although dogs can be picky about their water, many dogs are less picky about what they eat. Dogs do not taste as well as humans. They have only 1,700 taste buds compared with the 9,000 that humans have and therefore do not distinguish flavor differences as well as humans. Studies have shown that dogs prefer warm food over cold and moist food over dry, though. The smellier something is, the more dogs seem to like to eat it.

Dogs, like humans, have taste receptors for sweet, sour, bitter and salty foods, but their taste buds are most attuned to meats, fats and meat-related chemicals. They cannot distinguish subtle meat flavors, such as the difference between pork or beef. Dogs also cannot identify spicy foods well and may happily wolf down wasabi peas or lamb vindaloo. (However, spicy foods can cause indigestion in dogs, even if they eagerly scarf it.) Dogs do not crave salt the way humans do. Dog ancestors ate a mostly meat-based diet, and meat contains all the salt a canine needs. Therefore, ancestral dogs did not search for additional sources of salt the way humans and some other animals do. 

At the Somerville Dog Festival on Sept. 24. (Photo: Bill Trudell)

Dogs like sweet flavors. Although their wolf ancestors’ diet was 80 percent meat, it included some fruits and vegetables – so many dogs enjoy certain fruits and veggies, even if they cannot distinguish between the tastes of a strawberry and a blueberry. (Extremely sweet processed foods, such as human desserts and snacks, are not good for dogs.) Dogs generally avoid bitter or sour foods. My dog won’t go near any type of citrus, even if it is relatively sweet like a mandarin orange.

Dogs have a sense of smell that is 10,000 to 100,000 times better than that of humans, so the smell of a food plays a large role in how dogs experience flavor. (Humans have 5 million smell receptors; dogs have up to 1 billion.) 

At the Somerville Dog Festival on Sept. 24. (Photo: Bill Trudell)

Dogs have something called the Jacobson’s organ that runs along the bottom of the nose and connects directly to the brain. It can detect small numbers of molecules, including pheromones. Because this organ connects directly to the brain, there is never interference or mingling with other scents. If a dog sniffs another dog’s pee on the corner of a building, for example, it is using its Jacobson’s organ to learn about the other dog’s diet, gender and even its emotional state.

In addition to the Jacobson’s organ, dogs have two tiny holes in the roof of the mouth that allows them to pull in a scent without inhaling. For this reason, a dog can smell underwater, just by opening its mouth!

Dogs also have good scent memory. They can recognize by smell another dog that they haven’t seen in years. They can sniff the “peemail” at the base of a tree to determine what other dogs live in the neighborhood. They can smell your pant leg to determine approximately where you live and what pets you have at home. Dogs can move their nostrils independently, so they can use the direction of odors like a compass to find their way around.

You may have been told that a dog’s mouth is cleaner than a human’s. This is not true. Research has shown (yes, this has been studied) that dogs and humans both have more than 600 species of bacteria in the mouth – the bacteria just are not the same. Although most dog mouth bacteria won’t make humans sick, and vice versa, many dogs eat gross things. You may prefer not to let a dog lick your mouth.

At the Somerville Dog Festival on Sept. 24. (Photo: Bill Trudell)

Dogs do not sweat the way humans do. They have sweat glands, called merocrine glands, on their paws and noses. These glands are in other places on dogs’ bodies too, but there the glands secrete pheromones, not sweat. To cool down, dogs pant – it moves air over the tongue and mouth, allowing moisture to evaporate and cool them down the way that sweat evaporating from our bodies cools us down.

There is so much to say about dogs that I could go on and on. I will stop here for today with the promise that I may revisit this topic in the future if there is interest.

At Spy Pond in Arlington. (Photo: Bill Trudell)

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Seen nearby

Dan Harrington spotted this ash-throated flycatcher in Danehy Park on Dec. 2.

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Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.