Spring is here. Can you smell it?

Tip: As weather warms, start sniffing for clues to what animals are doing

Posted: Friday, March 26, 2010

More days of sunshine, longer hours of light. These are the familiar signs that winter has reliquished its hold. Warmer weather means many things,including smells.

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Abby Lowell / Juneau Empire
Abby Lowell / Juneau Empire

The light, syrupy scent of cottonwood buds is my favorite spring scent. As a wildlife spy, I've observed that cottonwoods grow near water, usually creeks or rivers. Hence, the sweet scent reminds me to be on the lookout for critters that lurk around streams or in trees on the banks such as mink, squirrels, deer - even warblers - as spring progresses.

Who knew one whiff could lead to so much? Your sense of smell can be a powerful tool when sniffing out wildlife.

How does it work? A scent is basically a chemical vapor (floating molecules). As things begin to thaw, as they do this time of year, scent molecules begin drifting around. Think of a frozen pizza. It doesn't smell as much as one hot from the oven, right?

It's at the top of your sinus cavity where a spot about the size of a quarter is packed with olfactory neurons - the same type of cells that make up your brain. These neurons are covered with even tinier, hair-like projections called cilia, which have receptors for scent molecules and act much like a chemical lock-and-key. Each receptor only fits one, or possibly a few similarly shaped, molecules. If the key fits the lock, the neuron sends a signal to the part of your brain that processes smells. Your genes determine what receptors you have, so people may detect smells differently. I, for example, can't smell skunk or skunk cabbage. (The molecules are too similar, apparently.) I don't have those receptors. It may be weird, but true.

Let's start with some clues even the greenest wildlife gumshoe can't miss. Large gatherings of animals can be, well, odiferous. Last summer I took a boat trip around St. Lazaria Island, near Sitka. As we rounded a corner, a sour smell slapped me in the nose even before the raucous braying of nesting Common Murres reached my ears. A tall rock archway led back into a shallow cavern. Hundreds of the black-and-white birds packed on the rocks which were frosted white with bird droppings.

Besides new levels of nasal shock, what can you learn from such a noxious site? It takes large numbers of birds, often over a number of years, to build up a serious stench. Those rocks aren't a one-shot nesting area, but a site used repeatedly, which means the birds will likely return next year, for the viewing (not smelling) pleasure of onlookers.

Your olfactory neurons are very close to the emotion and memory parts of your brain. Why? Being able to quickly remember a smell, and whether it was a good or bad experience, helps omnivores (such as humans and bears) sort through the large list of potential food items they encounter. Ever had a particular food (or beverage) make you really sick? After that, sometimes for a long time, just the scent probably made you queasy. The memory associated with that scent reminded you that last time its consumption led to very, very bad things.

Your experience is probably similar to how bears explore the world. They have a far keener sense of smell than people. Some say it's even better than a bloodhound. They can pick up even the faintest of smells. As salmon spawn and die in the creeks, a bear can smell the fish from afar and know it's time for dinner. Since a smell can be strongly associated with memory, a bear can remember that beach is good for clamming.

As you search for animal suspects, pay attention to the scents around you. They may help you find new places to look for animals. Smell eau du dead salmon on a new trail? Keep a wary eye out for bear tracks!

One of the earliest blooms in Southeast Alaska is the showy skunk cabbage. The vivid chartreuse buds pushing up through late winter snow release an odor that most people (well, those who can smell it) find ... distasteful. Why the nasty perfume? The insects that pollinate these plants aren't bees or butterflies, but flies and beetles that are drawn to droppings or carrion. Bears also eat skunk cabbage in early spring when they emerge from hibernation, so they may follow the scent. Bears don't eliminate waste while hibernating, and the plant acts as a laxative. Maybe the odor is appropriate in more ways than one.

Consider salmon the smelling champions of the water. They use a variety of ways to navigate from the ocean back to their spawning streams, but when they arrive at fresh water, their sense of smell guides them home. Each waterway has a unique chemical combination imprinted on the fish when young. Although research is ongoing, it seems that imprinting (being able to remember after just a brief exposure) for salmon is related to hormone levels. The hormone levels, in turn, seem to be influenced by how active the fish is, as well as by life stage. As a youngster, when it's on the go and not just hanging out eating, the salmon's hormone-stimulated brain is receptive to remembering the chemical signature of the water. For species such as king and chum salmon, they return years after leaving the stream by following a string of scent-memories. Now that's a powerful perfume!

Try this trick as a wildlife spy: Want to remember a certain spot where you saw an exciting new bird? Or the enjoyment of watching a bear fish for salmon? Pay attention to the smells like the delicate sweetness of budding cottonwood, or the thick scent of rotting fish. When you come across those scents again, it just might help trigger the scene you wanted to recall.

• Beth Peluso is a freelance writer, illustrator and avid birder.

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