Summary: Living below the soil surface, truffle fungi cannot rely on wind for spreading their spores. Instead, truffles signal their presence to animals such as pigs, squirrels, dogs, and even some insects through the production of smelly substances. Once eaten, truffle spores survive digestion and eventually return to nature where they colonize new roots.
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Similar to plants that produce seeds, many fungi produce spores with the purpose of colonizing new places and environments. Fungi that live aboveground produce microscopic spores that can be carried away by the wind, traveling distances that range from meters to several kilometers (i.e. the rust fungus).
Since truffles live below the soil surface, they can´t rely on the wind for dispersing their spores. Instead, truffles produce smelly odoriferous substances to signal their presence to many rodents (i.e. squirrels, hedgehogs), larger mammals (i.e. wild pigs), and possibly even to some insects (beetles and flies).
Animals that eat truffles will spread truffle spores through their feces sometimes kilometers away from where they have been consumed. Passing through the digestive tract of animals does not kill truffle spores that are very tough, and this even helps spores to germinate and colonize new plant roots.
Wild animals consuming truffles in truffle plantations pose a major challenge. For instance, wild boars that are typically active nocturnally can decimate a truffle plantation within a few nights. Preventive access measures such as fencing can help but are not always practical (i.e. for very large orchards).
How do dogs and pigs find truffles?
Both dogs and pigs have traditionally been used for truffle hunting. Whereas pigs seem to find truffles naturally, dogs require some weeks or months of training. Dogs´ advantages over pigs are their obvious smaller size, their obedience not to eat the fruit of their hunt, and the fact that almost any dog breed can make a good truffle hunter.
In 1990, the French scientist Thierry Talou tested the attractiveness of dogs and pigs to two compounds that are naturally present in truffles: the sulfur-containing volatile “dimethyl sulfide” and the steroidal pheromone “androstenol”. Results showed that dogs and pigs were attracted to dimethyl sulfide and not to androstenol.
Empirical evidence from truffle hunters illustrates that dogs can be trained to search for specific truffle sorts. This implies that dogs can pick up the scent of more than one flavor compound present in truffles, which is expectable considering that dogs´ sense of smell is much more acute than ours due to 50x more olfactory receptors.
Did you know that flies are able to find truffles?
Besides mammals, some beetles (genera Leiodes) and flies (genera Suillia) are also able to find truffles in nature. Those insects are often considered a pest in truffle farming since their larvae feed on truffles, and extensive insect damages have been reported to both European and Australian truffle plantations.
Insects can detect volatile compounds through their antennae, so it is likely that truffle beetles and flies use some unidentified volatile cue to locate truffles underground. Whether truffle beetles or flies spread truffle spores is also open to speculation, but other fungi are known to spread their spores by attaching them to the body of insects.
In southern France, some truffle hunters do not work with dogs or pigs to find black truffles but rely on truffle flies. When disturbed, a truffle fly “flies away” in a very characteristic “tiny jump”. Truffle hunters carefully drag a branch on the soil surface on the lookout for the jump which reveals the location of the truffle!
Why is this relevant?
Truffles are completely dependent on animals for spreading their spores and for colonizing new environments. Consumption by wild animals is consequently essential for maintaining the genetic diversity of truffles in natural truffle grounds. By contrast, truffle consumption by wild animals in artificial truffle plantations can result in a large economical loss and should consequently be minimized.
Written by Richard Splivallo and Viktória Tamás
Richard is the CEO of Nectariss and a truffle expert. As a former university professor, he has dedicated almost 20 years of his life to better understand the complex biology of truffle fungi and has authored more than 25 scientific publications on that topic.
Viktoria is currently a marketing intern at Nectariss. She earned her BA in Business Marketing with a Summa Cum Laude honorary title at the University of the Pacific, in California. Currently, she is pursuing her master’s degree in Management of the Flavor and Fragrance Industry at the University Côte d'Azur, in Nice.