The Web of Life (45-1-1) Mycophagous Mammals

 Mycophagous Mammals

Fungi are a common food source for many creatures, notably insects and mammals. A few mammals are obligate fungus feeders.

The long-footed potoroo, known as the “rat kangaroo,” is a marsupial the size of a housecat that lives in the warm, temperate forests of southeast Australia. Its dependence on truffles circumscribes its habitat to locations where fungi are predictably available throughout the year. This changes through the seasons: riparian areas during the warm, dry summer, and into other areas of the forest during the cool, moist winter months.

The Western red-backed vole is a small rodent: 6.5–13.7 cm long, 1.8–2.1 cm high, weighing no more than 30 grams. This burrowing vole is endemic to the forests of California and Oregon. 85% or more of the Western red-backed vole’s diet is fungus, preferentially the fruiting bodies of mycorrhizal fungi that are symbionts of forest trees.

The fungi fruit on decayed timber, after its nutrients have been exhausted. Because the fruiting bodies are underground, the spores are not liberated in the air, as with most fungi.

Voles feast on the fungal fruit, and deposit their droppings, along with fungal spores, throughout their burrows. This enables a mycorrhiza to spread to unassociated trees.

There is a 3-way symbiosis going on. If a forest is clear-cut, with dead wood and trimmings removed, the mycorrhizae stop fruiting. The vole population dies out. Newly planted trees struggle to survive.

Red squirrels, common throughout Eurasia, are not obligate mycophagists, but they are quite fond of mushrooms. These arboreal rodents dry their fungal finds by hanging fruiting bodies on the branches of trees.

Once dried, which typically takes a couple of days, squirrels cache their crop of dried mushrooms in knot holes, hollow branches, or nests of twigs in the canopy, as well as cavities in tree stumps or in holes beneath logs on the ground. This distributes the fungal spores about, allowing a new generation in a new location when the rains come.