Thursday, April 03, 2008

Truffling matter

Shortly after I acquired dart frogs (almost 6 years ago), I was sent home with a jar of fruit flies and a squirming mass of fat, white waxworms, described as “truffles” for dart frogs: “not a lot of nutritional content, but high in fat and highly desirable.” I dropped one of the thriving waxworms in the tank with Gromette, my yellow and black Dendrobates tinctoria. The active little frog bolted across the tank, lunged towards the worm, grabbed it with her right hand and, in a matter of seconds, crammed it into her blue-tongued mouth. The worm was almost as big as Gromette, which made the process of eating the worm require several moments of repeatedly opening and closing her mouth as she forced it down her throat. This process replayed itself with all of my other dart frogs, and even with Pepe, my Hyla ebraccata, an otherwise deliberate, slow little frog. Pepe’s waxworm attack was so uncustomarily expeditious that it truly warranted capturing on video.

So it came as no surprise when I discovered that deer truffles, an underground mushroom found beneath oak trees in the Ozark Highlands, provided little nutritional value to the large and small mammals who regularly scrape away the soil to find the delicacy. Actually, deer truffles (Elaphomyces granulatus) are not true truffles (chiefly of the genus Tuber), but they belong to the same family, the Ascomycetes. Members of this family are found underground growing on the roots of certain host trees. An easy way for a human to find them is to locate one of the two parasitic mushrooms whose fruiting structures appear above ground: Cordyceps capitata and Cordyceps ophioglossoides (pictured below). However, many mycologists recognize mammal scrapes and locate truffles that way. Recent research on roe deer scraping found that 68% of all scrapes revealed the fruiting bodies of deer truffles, throwing a complication in the theory of marking behavior.

Nutritional content of deer truffles is relatively high for mushrooms, with a nitrogen content of 80%. But the digestibility of that energy source in small mammals is low. Most of the nitrogenous energy is actually tied up in complex, relatively indigestible cell wall tissue and spores. The indigestibility of the spores allows deer truffles to spread as mice excrete the spores in their waste. Deer, on the other hand, only eat the thick outer tissue, leaving the spores behind.

When food sources are low, deer truffles remain an important food source which requires little effort to access, and even less in processing. By weight, deer truffles are 70% water. Their marginal nutritional value may account for the animal habits of eating small amounts of mushrooms of varying species each day to compensate for the differences in digestibility. Of course, everyone in the Ozarks has hopes that they'll stay away from this year's morels.

No comments: