Basin and Range Topography

Written by Peter Pearsall/Photo by Peter Pearsall

“The mountains form a ribbon of familiar landscape separating two vast spaces, blue haze above, a mosaic of cracked mud below. The desert almost seems to mirror the sky in size. It complements it and completes it.” -Stephen Trimble, “The Sagebrush Ocean” (1989)

Southeast of the Refuge lies the pancake-flat expanse of the Alvord Desert, an 84-square-mile former lakebed along the eastern escarpment of Steens Mountain. In much of the Great Basin, blocks of the Earth’s crust that fractured along fault lines have gradually tilted under their own weight, creating sloped mountain ranges that generally trend north-to-south. Steens Mountain is a striking example of this fault-block phenomenon: 50 miles long from north to south, its gentle western slope rising to 9,734 feet and dropping abruptly into the basin of the Alvord, more than 5,000 feet below.

Basin and range topography—those hundreds of north-south-trailing mountain ranges separated by broad, flat basins—owes its almost orderly appearance to the tectonic peregrinations of the Pacific Plate. Extending from approximately San Francisco to Tokyo and from Anchorage almost to New Zealand, the Pacific Plate is on a leisurely course headed due northwest, three inches a year, and the North American continent seems reluctant to let it go. As the Pacific Plate shears up and away from the continent, enormous cracks called normal faults split western North America’s crust into roughly parallel blocks, which tilt as one crustal edge slips beneath the other. An upwelling of magma beneath the stretched-thin crust helped to spread these blocks apart, giving rise to the Great Basin’s mounded convexity, in which the highest elevations lie at the basin’s center.

The ascending edges of these crustal blocks, now thrust up from the plain, become subject to an eternity of weathering processes: wind, rain, snow and ice. All the eroded sediment flows down into the gaps between faults, creating wide basins adjoining ranges. In days of yore these basins were filled with water, but few such lakes remain. Most are now dry, barren, leveled by millennia of alluvial deposits. These basins are some of the flattest areas on earth.

Western Burrowing Owls

Written by Peter Pearsall/Photo by Peter Pearsall

The Western burrowing owl (Athene cunicularia hypugaea) is a ground-dwelling owl that inhabits areas of short vegetation and bare ground, including deserts, grasslands and shrub-steppe across the West. In Oregon, they are usually associated with sagebrush-steppe, grasslands, pastures, roadsides, and other areas characterized by sparse vegetation and level terrain. East of Oregon’s Cascade Range, burrowing owls are known to breed in all or nearly all of Oregon’s counties, being most common in Wasco, Morrow, Umatilla, Malheur, Harney, and Lake counties.

Its common name refers to the fact that this owl nests and roosts in underground cavities. While capable of small amounts of earth-moving with their taloned feet, burrowing owls usually seek out the previously dug cavities of burrowing mammals (such as ground squirrels, kit foxes or badgers) in which to take residence and raise young.

Burrowing owls spend much of their time on or near the ground, where their spotted buff-brown plumage keeps them relatively inconspicuous as they stand outside their burrows or perch in low vegetation. Always alert to potential danger, the rounded heads of these owls swivel about fluidly, their bright yellow, forward-facing eyes constantly surveying their surroundings.

These small, long-legged owls—seven to ten inches from head to tail—prey on a wide variety of small animals including rodents, reptiles, amphibians and insects, which they capture with their feet and usually ingest whole. They sometimes employ a hovering flight to scan the ground below for prey; they also sally to the ground from perches to chase and capture prey on foot.

Unlike many owl species, burrowing owls may be active both day and night. In the height of summer, they tend to forage more at night, when temperatures are cooler. Similarly, their active period shifts to a more diurnal schedule as daytime temperatures drop in fall and winter.

Burrowing owls do not “hoot” in the traditional owl sense, but males give a two-note coo-coo song when courting a mate. Both sexes give a barking alarm call when intruders approach a nest burrow. When young burrowing owls are threatened, they retreat underground and make a harsh rasping or hissing sound. From the confines of the burrow, this sound very closely resembles the rattle of a disturbed rattlesnake and probably serves to deter predation.

During the Geological Exploration of the Fortieth Parallel, which began in northeastern California and went through Nevada to southern Utah from 1867 to 1872, the expedition’s then-teenaged ornithologist, Robert Ridgway, remarked that “Although the ‘Ground Owl’ was found at widely-separated places along our entire route, it was abundant at very few locations…Eastward of the Sierra Nevada we found it only at wide intervals.” That description is perhaps even truer today, as burrowing owl populations across western North America are seeing declines, primarily due to habitat loss from land conversions for agricultural and urban development, as well as habitat degradation and loss due to reductions of native burrowing mammal populations.

Painted Lady Butterflies

Written by Peter Pearsall/Photo by Peter Pearsall

Perhaps you’ve seen a few of these butterflies recently, flitting about in your garden. Or perhaps you’ve seen hundreds, coursing along coastlines or crossing highways in steady streams, with many sadly meeting their ends splattered on car windshields and grills.

Measuring two inches from wingtip to wingtip, with black and white markings against an orange backdrop, these scale-winged insects are a familiar sight to people around the world. The painted lady (Vanessa cardui) is one of the most widespread butterfly species on the planet, found on every continent except South America and Antarctica.

In years of abundant winter rainfall, painted lady numbers can skyrocket, as early-blooming wildflowers provide nectar for butterflies and food sources for their larvae.

Like the famous monarch butterfly, painted ladies are migratory, following favorable conditions with the seasons. In the American West, these butterflies generally move in a north-northwest direction, leaving the Southwest and Mexico at winter’s end and traveling toward the Pacific Northwest with the onset of spring.

Painted ladies aren’t picky in their choice of plants to nectar on. Adults will use almost any plant in flower but they show preference for those in the Asteraceae family, including thistles. These plants are the butterfly’s hosts—their larvae eat leaves of asters and spin silken webs to protect themselves from predators.

Interestingly, painted ladies are known to breed and lay eggs in all seasons. A single year’s migration can involve several successive generations of painted ladies, each born and raised along the migration route.

It’s estimated that millions of these butterflies are migrating across North America this spring. Enjoy this natural spectacle while it lasts!

The Ingenious Rust Fungus

Written by Peter Pearsall/Photo by Peter Pearsall

A walk through the sage-steppe this time of year usually turns up some of the first high-desert wildflowers blooming between the dormant shrubs and still-brown grasses. Sagebrush buttercup, Beckwith’s violet, yellow bells and several biscuitroot species are among the earlier species to flower. But there is another springtime plant, superficially flower-like in appearance, that bears a closer look.

This rosette of yellow “blossoms” is in fact a rust fungus (Puccinia monoica) infecting a native mustard species. The fungus commandeers its host, altering its natural growth habit to produce yellow rosettes of “pseudo-flowers” which offer no real nectar or pollen but instead serve the reproductive purposes of the fungus.

By forcing its host’s pseudoflowers to manufacture floral scents and sticky, sweet “pseudo-nectar”, Puccinia deceives insects into landing on the infected plant. The fake flowers even mimic the lines and patterns known as nectar guides, visible under ultraviolet light, that many real blossoms sport to visually attract pollinators.

Once the insects alight, they inadvertently collect fungal gametes from the hundreds of “spermatogonia” that cover each pseudoflower. These insects then fly off to visit other pseudoflowers, bringing the hitchhiking gametes along to effectively “pollinate” the fungus.

But this is just one phase of Puccinia‘s life cycle. Once a Puccinia pesudoflower receives the right gametes to undergo sexual reproduction, it loses its bright color, attractive odor and sticky exudate and starts producing spores. These spores, carried by the wind, eventually land on certain grass species, which are the fungus’s secondary hosts. Once the spores germinate and infect the grass, a new, special set of spores is produced–these drift on the wind and eventually attach to mustard plants, starting the cycle anew.

The First Butterflies of Spring

Written by Peter Pearsall/Photo by Peter Pearsall

Spring is slow to arrive to Malheur Refuge. Frost clings to the ground well into April most years; the austere high-desert vegetation stubbornly refuses to show signs of life until even later. But the subtle lengthening of days doesn’t go wholly unheralded. Resident birds begin warming up their vocal repertoires, migratory ducks and geese arrive to still-frozen waterways, and hibernating squirrels and other mammals rouse from their dens, all anticipating the change in seasons.

With below-freezing temperatures occurring regularly at night, one doesn’t expect to see many poikilothermic, or “cold-blooded”, creatures out and about. But one resident poikilotherm that stirs to life on warmer days in early spring is, improbably, a butterfly: the mourning cloak (Nymphalis antiopa), a widespread species found across North America and Eurasia, is usually the first butterfly seen at Malheur Refuge each spring.

Seeing a butterfly on the wing when the landscape is still icy and winter-browned can be startling. Across their range, chocolate-brown mourning cloaks are often the first butterflies to emerge each year, fluttering across snow-drifted fields and through leafless forests at a time when very few invertebrates are active. Unlike most temperate insect species that overwinter as larvae or pupae and emerge as adults in spring, mourning cloaks emerge in summer and spend the bulk of their 10-month lives as adults during the coldest period of the year. So how do these delicate insects survive below-freezing temperatures at night? And what are they eating during the day, when flowers are but a distant memory of seasons past?

To address the first question, mourning cloaks engage in “cryo-preservation”—that is, they allow themselves to literally freeze solid. Like other freeze-tolerant organisms such as certain frogs, turtles and insects, mourning cloaks will concentrate the sugar alcohol glycerol in their hemolymph (analogous to blood in vertebrates) to serve as an antifreeze. The glycerol helps to slow down and isolate the formation of ice crystals in the butterfly’s hemolymph-filled body, preventing lethal damage to organs and tissue. This adaptation allows the butterfly to spend the colder months of winter nestled in leaf litter or tree cavities, as frozen as its surroundings and hidden from predators. With the arrival of longer days and warming sunlight, the butterfly thaws out each morning to begin its search for food and mates.

This brings up the second question: What do mourning cloaks eat when the ground is still frozen? While the majority of butterflies require flower nectar of some sort for food, mourning cloaks are adept at sipping tree sap, which also thaws during sunny winter days and provides a crucial source of sugar in a nectar-barren landscape. Trees damaged by winter weather can often be found oozing sap as the weather warms. In Harney County, juniper trees sporting “wells” drilled by red-naped sapsuckers are another reliable source of sap. Mourning cloaks may also find fermented fruit left over from the previous summer.

Finding fully fledged butterflies at winter’s end might seem like an anomaly to us homeotherms, but in the case of mourning cloaks, it’s simply an aspect of their unique life history.

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