The following query was intriguing, though a bit different from most that I receive.

Q. I live in a small town in western Massachusetts, pretty much in the middle of the woods. I’m trying to find a source that will tell me what animals smell like. I can identify bear, raccoon, and porcupine, and of course skunks. When I let my cats out in the morning, there is a lingering musky, garlicky odor on one side of the house. I’m hoping it’s not a fisher [see explanation below], but I don’t know what they smell like. I’ve not had any luck finding information about identifying their smell. Why do some animals have a scent?

A. First, what is a fisher? Fishers are tree-climbing mammals of the northern states from New England to Washington and far north into Canada. They are in the same family as skunks and weasels, a group of animals known for their unpleasant, musky odors. Fishers eat small rodents and snowshoe hares and are considered one of the most effective predators of porcupines. Fishers can weigh more than 10 pounds and are fierce, sort of like a miniature wolverine. Being concerned that a fisher might attack one’s house cats is not unreasonable.

Field guides often mention if a particular species produces a distinctive odor, but I know of no comprehensive guide of any sort that categorizes how to identify animals or plants by their smell. An olfactory identification kit of some sort is an excellent idea. Some species have readily recognizable smells, and being able to recognize the scent of various animals would be useful to ecologists and wildlife biologists. A scratch-and-sniff book would be awesome in the field. However, anyone who kept at home a book with the overpowering scent of skunk or vile-smelling watersnakes would have few visitors and no roommates.

Fishers are said to give off a musky smell when they are disturbed, but so do lots of other animals. Mink, copperheads, and the little stinkpot musk turtles found throughout most of the eastern United States all emit a highly unpleasant odor when frightened, annoyed, or aggravated in some way. Each is probably distinctive if a comparative smell test could be made.

Most, though not all, mammals have a pungent smell to us. Other animals and many plants also have a scent humans can detect. When first captured, a garter snake gives off a cloying smell like cheap perfume. A cherry millipede exudes the pleasing smell of almonds or maraschino cherries when handled. And of course many plants, such as honeysuckle and tea olive, produce pleasant aromas whether you pick them up or not.

Why do some plants and animals produce a scent while others do not? The biological purposes of producing an odor or being able to detect a smell are as varied as the reasons for plants and animals having different colors. Smells provide information. Having an olfactory system that is able to detect airborne molecules can give an animal a survival advantage in finding a mate or food or in avoiding a predator.

Many flowers produce a fragrance that promises nectar for insects. The plant also benefits because the insect serves as a pollinator when it goes to another flower. Some smells detectable by people appear to have no particular value to us or to the organism. For example, crushing the leaves of a hickory tree produces a tart odor, but I see no advantage in my being able to recognize that scent. But perhaps the smell repels insects that might otherwise eat the hickory tree leaves.

Many animals produce a musky smell when they feel threatened, making it repugnant to a predator interested in it as prey. Sometimes a musky smell serves as a hazard warning to a competitor. Fishers are about the size of house cats, so it could be that the musky smell alongside the house is simply a warning to the cats not to attack the fisher.

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Whit Gibbons is an ecologist and environmental educator with the University of Georgia’s Savannah River Ecology Laboratory.