Bitterness

Coyotes and their tastes

            Back in 2005, a beautiful gourd vine was sprawled across the remains of a dead cheesebush in our back yard in Borrego Springs.  I eventually identified it as a coyote melon (Cucurbita palmata), a widespread but not common species in the deserts of southern California.  The grayish, palmate leaves, yellow flowers and striped gourds made it irresistible to draw, and I sketched it while hunkered coolie-style in front of the plant until my legs cramped, and I had difficulty straightening up again. 

My drawing of a coyote melon (Cucurbita palmata) from the Anza-Borrego Desert in southern California.

            The vine died later that year, leaving behind its dried gourds.  The seeds inside were loose, and when I shook the gourd, it produced a sound like a maraca.  To my disappointment, the vine did not reappear the next year, so I broke open a gourd, planted the seeds and provided an irrigation drip. No luck, not even a sprout.  You would think that having previously grown in that arid spot without my help, it would spring forth with vigor and gratitude with my help.  But no.  I tried again a couple of years later.  Still no luck. Maybe the seeds need to think about sprouting for a few years, or maybe they have been deposited in the seed bank as a hedge against a variable climatic future.  Maybe they must take a trip through an animal’s digestive system before sprouting.  Another one of life's mysteries lay before me. 

The fruit of the coyote melon turns yellow when ripe and contains hundreds of seeds that rattle after the gourd dries out.

As happens with common names, there is a closely related plant also sometimes called coyote melon, but more commonly called stink gourd (Cucurbita foetidissima; note the superlative Latin).  Should you come upon one and detect the unpleasant odor wafting from these sprawling vines, you will understand the appropriateness of the name and the Latin superlative .  The vines arise from a huge root that can weigh over 100 pounds and that puts out dozens to hundreds of shoots every spring to create patches of vines many meters across, only to die back late in the year.  In 2002, I spotted the one below on an Arizona highway, taking away some vines and fruits to draw later. For my trouble, my car smelled like armpits for a day or two.  I was not tempted to taste this “melon”, knowing that an extreme bitter taste embellishes the offensive smell. 

My drawing of a stink gourd (Cuburbita foetidissima) that grew along a highway in southern Arizona. The patch of vines was several meters across.

One supposed origin of the name is that coyotes are reputed to eat the melons, and the seeds have indeed been reported in coyote scats.  What is it about coyotes? Both melons (C. palmata and C. foetidissima), are loaded with high levels of cucurbitacins, among the bitterest substances known.  Cucurbitacins are supposed to keep herbivores from eating the plant, and there are sets of genes that synthesize several of these compounds in the leaves, the fruit, or the whole plant.  So, leaves having plenty of bitterness to deter herbivores seems to make sense, but the whole point of a plump fruit is to get animals to eat it, isn't it, and thus disperse the seeds?  So why make a fruit that is so bitter that no creature is likely to say yum yum.  Moreover, if one does manage to get some of this stuff down, it is likely to come back up pronto, for the flesh is emetic too. You would think that no animal that ate this stuff would be likely to have seconds. There is thus mystery in finding the seeds in coyote scats in spite of the apparent inedibility of the gourd.

In American Indian mythology, the origin of the name “coyote melon” is more interesting and fanciful.  The mythological coyote is a comic trickster, crafty and always ready to test limits and make trouble.  Coyote is thus supposed to have created a melon whose seeds are edible, but whose flesh is extremely bitter.  Nevertheless, the seeds of both these melons were eaten by Indians, who must have had some effective and tricky way of separating the seeds from the flesh, because even a trace of flesh imparts a strong bitter taste.  The effort must have been worthwhile for the Indians living in this harsh southwestern desert, but how the coyote manages is less clear.

Or is it that the coyote cannot taste bitterness, like cats cannot taste sweetness?  Indeed, even among humans, some are far more sensitive to bitterness and others far less, and this is the case for sweetness (and perhaps saltiness) as well.  Extrapolating to other animals, we should expect that sensitivity to many tastes are tailored to diet.  Human love for sweetness and revulsion (mostly) for bitterness are probably the legacy of a fruit-eating primate whose diet included a wide range of plants.  In such a diet, bitterness suggests toxicity, and indeed, bitterness can induce both vomiting and long-lasting taste aversion in humans and a number of animals.  With their largely carnivorous diet, coyotes may experience little selective pressure against eating bitter things.  Maybe coyote has no special magical tricks for eating its namesake melons other than lacking bitter-responsive taste buds.  Someone should ask a coyote.