Winter, and our first big snow of the season, prompted a number of queries from colleagues and naturalists, mostly concerning track identification, but also a comment from a friend who had her first close look at a snowy owl—an unforgettable experience, of course—and an email with a photo of one of the several species of diving birds that overwinter here, and a question: what is it, and what is it diving for?The latter was a common loon, in its relatively drab winter plumage, diving in Three Mile Harbor’s inlet. What was it diving for at this time of year? I’ve wondered that myself. My references state that loons generally consume their favorite prey, small fish, before they resurface, making identification of their finned catch impossible. But I’ve noted that they often surface with a food item that may be a bit more challenging to get down into their gullet quickly: small crabs.
No one asked about the tiny creatures that appeared in uncountable numbers on the surface of the snow on the warm, above-freezing days soon after the snow fell. These dark-colored specks can stain the white snow gray and black but are so small (measuring approximately one-tenth of an inch in length) that they are easily mistaken for inanimate objects. A close look will reveal that they are, indeed, alive and kicking.
Its common name is the snow flea, a misnomer in that it does not bite, is not a parasite and is not a flea at all. Its flea-like habit of propelling itself through the air is not due to large hind legs, as with the flea, but to a long, forked tail-like appendage folded under its hindquarters and held there under tension by hooks that, when released, catapults the creature into the air up to a hundred times higher than its body length. It is the source for its other common name, springtail. The latter also refers to the larger class (Collembola) that it belongs to.
It is not unusual to find a number of common names for a single plant or animal, but in this case I was surprised to find more scientific than common names for the snow flea. It appears that this species, along with its subphylum relatives, the Hexapods, were recently determined not to be insects (I think because they lack external mouths), and the scientific names got shuffled around. It’s possible that there are several species in the Northeast, but as best I can determine, the current name for the most common species is Hypogastrura nivicola.
It is a member of the arthropod phylum, along with another common creature, the beach flea, or sandhopper, that some readers may be familiar with. Unlike the sandhopper, the snow flea is very susceptible to desiccation and survives only in the moist organic leaf litter and soil environments. There, it is found in very dense numbers; some estimates list it at densities of 100,000 individuals per square meter of soil, and it is considered one of the most abundant of all macroscopic (visible with the naked eye) animals on earth.
Snow fleas play an important role in the soil community, consuming and disseminating soil microorganisms and feeding on and fragmenting organic matter, aiding in the process of decomposition and recycling soil nutrients.
They also produce a glycine-rich protein that binds to ice crystals as they start to form in the body, isolating the ice and preventing it from growing larger and damaging tissue. This protein with antifreeze properties is being studied for use in preserving human organs over the time period between when they are extracted from a donor and when they are implanted in the recipient.
Another amazing feature of this tiny organism is that it has a tissue enzyme that is capable of metabolizing the very toxic compound DDT into the non-toxic DDE compound.
After researching the natural history of this easily overlooked organism, two unanswered questions remain. First, what prompts the snow flea out of its home environment in the leaf litter and soil, where it has food and is not all that conspicuous, to hop about on the surface of the snow, where there is no apparent source of food and it is extremely conspicuous?
Second, why aren’t the black-capped chickadees, kinglets and other small insect-eaters flocking to feast on this conspicuous, concentrated and easily captured source of insect protein?
