Mid-February’s weather has me thinking of holing up and taking refuge from winter’s resurgence. Cold, incessant winds, snow, and hard freezes have collectively conspired to send my mind inward, longing for a space devoid of the frigid onslaught. What if I could just wait out the worst that winter has to offer, simply emerging on the meteorologically nicest days that suited my personal fancy?
Sound far-fetched? Enter our freakish and fantastic fossorial fauna – a rogues’ gallery of beasts that frequently lurk below ground in an effort to survive, each in their own, unique fashion. An animal is described as “fossorial” if it is able to burrow and lives primarily underground. Mammals (of course), reptiles, amphibians, a host of invertebrates, and even one bird get in on this decidedly odd act here in the Sky Islands.
We start with the quintessential underground dweller known to many and often despised for their sneaky incursions into our gardens: pocket gophers. These semi-notorious rodents have evolved a set of traits highly adapted to life underground. In a wide range of soils, from valley floors to near the tops of our tallest mountains, they live a mostly solitary life. They form characteristic mounds as they construct their complex burrow systems. Hidden from the prying eyes of humans and predators alike, they eat, travel, sleep, and mate underground – only making cameo appearances at the surface as they plug the tops of their tunnels. So finely tuned are they to their lifestyle that they are able to excavate soil with their front two enlarged incisors with their lips closed completely behind them! Further, they possess a pair of external cheek pouches or pockets (hence their name), which serve to store and transport food – mostly roots and other plant parts. Bizarre!
Leaping to the world of amphibians, we find a number of anurans finding succor under terra firma. Prominent among them are spadefoot toads who, like the gophers, bear witness to their lifestyle in their moniker. The “spade” – located on their hind feet – is properly termed a tubercle. These small, cat-eyed toads use them to dig down into the earth, seeking more stable temperatures and greater humidity. There they wait for most of the year, entombed in a mucous casing of their own making. Come monsoon season, rain and even the rumblings of thunder may entice them skyward. Freshly formed pools of water are their breeding grounds, where males and females congregate in an unabashed mating frenzy. Their tadpole offspring exit their watery habitat in as little as ten days as tiny “toadlets,” embarking on their own underground odyssey.
Among our copious invertebrates, perhaps ants take fossorial first prize. Few of the 190 or so species that call the Sky Islands home do anything other than live underground. Leafcutter ants of several species use the moist subterranean climate to grow fungal gardens – their sole source of food. Honeypot ants have a special caste of sterile workers that spend their lives as living “pots,” hanging from dark chamber ceilings, their abdomens distended with the sweet liquid that lends them their name. Army ants of at least four species steal underground holes and tunnels from other ants, invertebrates, and even rodents. From there they launch their murderous assaults upon other ant species, greedily devouring their brood.
I was reminded about just how reclusive fossorial fauna can be when, several years ago, a lone desert box turtle made a cameo appearance at Raven’s Nest Nature Sanctuary during monsoon season. While the species may well breed here, I have never seen one before or since at the refuge. Soil enshrouded ghosts, these and their ilk.
Blind snakes, termites, Gila monsters, ant lions, skunks, kangaroo rats, and, yes, even one bird – the burrowing owl – all have evolved their own, unique take on life underground. In fact, it seems so crowded down there that I may just stay terrestrial for the time being.
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure, Education & Conservation organization devoted to protecting the unique biodiversity of the Sky Islands region. Join Vincent at the Tin Shed Theater on March 24 for his “Biodiversity in the Heart of Sky Islands” nature documentary. Visit ravensnatureschool.org