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Nosy business

By Ranger Steve Mueller

Busy bodies abound. Not everything sticks its nose into our business. Many wildlife are keenly aware of danger based on smell. People and possibly some predators know to stay downwind of wildlife, so prey do not catch their scent. When I approach deer from upwind, my scent drifts toward them. I do not think I smell but I do.

Browsing deer lift their heads and look in my direction, expecting to see motion. I stand still and cautiously move when they were not looking. Frequently a deer will raise its head to scan for danger. Sometimes their white flag is raised and slowly lowered. When too nervous, deer either bound away or causally walk off.

Once I approached a winter herd and deer frequently looked my direction. Soon two deer came bounding toward the herd from behind me and breezed past without noticing my presence. Close behind were two dogs in pursuit and they were running straight for me. I was still as a tree but became alarmed thinking they saw me and decided I was prey. Upon closer approach, they abruptly turned to continue deer pursuit. They ran through the deer herd without noticing it. The herd stood fast. In the area I found a dead deer previously killed by dogs.

There is good reason dogs and cats should not be allowed to roam freely unattended. Cats stalk wildlife in my yard and through the sanctuary. The American Bird Conservancy states outdoor cats in the United States alone kill approximately 2.4 billion birds every year. Cats have contributed to the extinction of 63 species of birds, mammals, and reptiles in the wild and continue to adversely impact a wide variety of other species, including those at risk of extinction, such as the Piping Plover that is federally endangered.

Cats and natural predators use their noses, in addition to eyes, when searching for prey. Predation is instinctive and beneficial in controlling wildlife populations, but free roaming non-native species like cats are harmful for maintaining healthy nature niches in ecosystems.

Not all species smell with noses. Insects smell with feet and antennae. When a butterfly lands on a plant, it recognizes the plant by smell sensed through its feet. When searching for a proper plant for egg laying, it uses its “nose feet.” If the plant is a correct species, a butterfly might possibly lay an egg on it.

On the West Michigan Butterfly Association count, we saw a Viceroy land on an aspen and lay an egg on a leaf. We have witnessed the same on willow. Both plants are in Salicaceae family with similar chemical scent. I am not the only thing that smells. Odor is essential. Many plants have developed scents that protect them from being eaten. Mints, mustards, and most plants have chemical scents that aid their survival. We might like the smell of mints and even its flavor in foods, but its chemical smell is a defensive mechanism.

Insects are repelled by most plant scents and offspring will die eating the vegetation. There are always exceptions and various species have developed the ability to survive eating plants despite their chemical defenses. A handful of species evolved ways to neutralize the chemicals in selected plants or ways to tolerate them. This limits the number of organisms able to eat any one species. It allows for both plant and insect survival.

Monarchs lay eggs on milkweeds that have strong chemical defensives. The caterpillar will bite the main leaf vein that feeds the leaf. When a caterpillar feeds on a leaf, the plant sends extra defense chemical to protect the leaf but because the main vein into the leaf has been severed, it cannot increase its chemical defense.

The Monarch incorporates some of the plant chemical into its body and becomes protected from many predators that find it too untasteful. Birds will even become sick and vomit after eating one. They learn to avoid orange insects. The bright aposematic orange color announces a defensive taste the butterfly stole from the milkweed.

Smell is a fabulous sense that is better than sight, hearing, taste, and touch in some ways. Enjoy nosy business.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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