Earth Almanac: July/August 2006

Desert Tuna

As the summer sun gains strength, “tuna” by the thousands show up in dry, sandy habitat throughout most of the contiguous states, especially the Southwest. These tuna are vegetable, not animal—the succulent fruit of more than 30 species of prickly pear cactus in the United States. Prickly pear tuna can be red, purple, orange, yellow, or green. Most can be eaten raw or made into syrup or jam. Horchata, a Mexican beverage concocted with tuna, rice, almonds, and milk, has been popularized by the TV show Martha Stewart Living. The seeds inside the fruit are distributed by the many birds and mammals that eat them. Prickly pears can also reproduce asexually when the flat, fleshy pads are broken off and moved by flash floods, storms, or wildlife. Insects that feed on prickly pears produce a red pigment formerly used as dye. In the late 18th century English settlers, hoping to manufacture this dye for army uniforms, unleashed the plant in Australia, thereby setting off one of the world’s most ecologically devastating plant invasions.

Hairy Business

Now, as they get on with the arduous task of fledging their broods, hairy woodpeckers—larger, longer-billed, shier versions of downies—are quieter. Their territorial drum rolls and rattling songs, which rang through almost all of our nation’s forests in spring, have been largely replaced by muted contact calls, wing flutters, and the crackle and chunk of stout bills on decaying wood and bark, as these robin-size birds go about the business of foraging for insects. Watch a hairy and it may lead you to its nest cavity, excavated mostly by the male—he’s the one with the red patch on the back of his head—in dead wood or soft living wood (often spruce or poplar). Both parents feed young. Listen carefully and you may hear the brood’s begging chirps and sated squeaks.

Tossing and Turning

Because they are there; because they live in the tumultuous union of land and sea, moving with it as it shifts with the tide; and because there’s no other way to see mole crabs feeding. That’s why in high summer you need to find young companions and sit with them in the suds, with waves breaking over their waists and your shins. Various species of mole crabs—not true crabs but close relatives—inhabit the Atlantic, Pacific, and Gulf coasts, and all feed by filtering out organic material. As each wave recedes, watch for a V-shaped pattern as water passes through the crab’s feathery, antennalike sieves protruding from the sand. Scoop up the crab (quickly because they move fast); it has no pincers and can’t bite. Note the eight wriggling legs; a smaller fifth pair is tucked up out of sight. Note the eyes set on movable stalks, and another set of antennae by which the crab pumps water to its gills. When you hunt mole crabs with children, other good things turn up for, as E.E. Cummings observed, “whatever we lose (like a you or a me) / it’s always ourselves we find in the sea.” 

Zigzagging Dragons

Fleeting as summer are the lives of dragonflies (a.k.a. “sewing needles,” owing to their shape), but these ancient insects seem to compensate with frenetic activity. Flight muscles that comprise nearly two-thirds of their body weight allow them to move straight up, straight down, backward, and sideways; they can even hover. (As country mothers counsel, when sewing needles hover over water, they are showing the good boys where the pickerel are and waiting to sew shut the lips of the bad ones.) Few, if any, species are more active than the white-tailed skimmer, common throughout the United States and so named for the white waxlike material on the male’s abdomen. These are among the dragonflies you’ll most likely encounter in upland fields. But now they hunt over water as well, and females (which lack white abdomens) are dipping to the surface to deposit eggs. The male jealously guards his mate to keep other males from scooping his semen from her storage sack and inserting their own.  

Uncommon Lives

In the long, sultry days of summer, nature slows a bit. Most mammals are fat and logy, having recovered from the weight loss of winter and the stress of mating. Most birds have brought off their clutches. You may not see much on “nature walks”—unless, of course, you start turning over logs, rocks, and bark. In the northeast quarter of our country, your outing will almost always be saved by a red-backed salamander—probably the most  abundant vertebrate in eastern forests. There are three color morphs: red-striped, leaden, and bright orange, the last apparently protective in its mimicry of the red eft, the terrestrial stage of the highly toxic red-spotted newt. Common as red-backs are, they lead uncommon lives. At night they climb low vegetation to hunt small invertebrates. They are laying their eggs now—not in water like most salamanders did in spring but on the ceilings of their subterranean nests. And unlike most salamanders, females guard the eggs, lunging at and biting intruders. Young hatch fully formed save for a vestigial set of external gills that are quickly absorbed.