Migration

The days are getting shorter and cooler. Leaves are starting to turn and fall. Winter is approaching, and many animals are have already begun their seasonal migration. While some hibernate to avoid unfavorable seasonal habitat conditions, others move temporarily to more suitable habitat.

Migrations occur across all different animal classes: birds do it, and so do mammals, fish, insects, reptiles, amphibians, and crustaceans. Even some people do it. Florida and Arizona get plenty of snowbirds from up north every winter. More traditionally, nomadic tribes still exist in Africa and Asia living as they have for centuries.

We’re an ecology blog, not an anthropology blog so let’s forget about nomads for a minute. Perhaps the most visible migrations here in America are those of birds and monarch butterflies. Birds migrate to and from pretty much everywhere. Some stay within North America when migrating while others fly from pole to pole. Others, of course, are somewhere in between.

We’ll use the Baltimore oriole as an example of avian migration. They arrive in the eastern US from Central and northern South America in April and May. This is their breeding ground. They begin nesting right away and eggs usually hatch in June. Southern migration begins as early as July and has peaked by September.

Baltimore oriole (NPS)

Monarch butterflies journey to Mexico in a multi-generational migration. Northern monarchs go south to the oyamel fir trees in the mountains of central Mexico. Millions of them cover the trees. After winter, they head north again, laying eggs on milkweed plants. Caterpillars hatch in a few days and eat the plants before forming a chrysalis. A new butterfly emerges and continues the northward journey, stopping at milkweed to lay eggs and start the hatching and migrating process over again. The northernmost monarchs are able to return to Mexico in a single journey.

Monarch butterfly

The pronghorn in Wyoming migrates vertically. It moves from summer grounds in Grand Teton National Park about 150 miles south to lower elevation in the sagebrush habitats of the Green River area. This is North America’s longest mammal migration.

Pronghorn

Not all migration is seasonal. Zooplankton in the ocean migrate vertically through the water column on a daily basis. At night the move toward the surface, and by sunrise they are headed back to the briny deep. While a journey of hundreds or thousands of feet might not seem like much to you, keep in mind that these tiny critters probably can’t see as far as the other end of a yardstick.

Zooplankton (Nature International Journal of Science)

Fall migration is happening now. Who is moving through your neck of the woods?

This week's information comes from:

Journey North (Baltimore oriole)

National Geographic (monarch butterfly)

Wildlife Conservation Society (pronghorn)

Nature International Journal of Science (zooplankton)

The Sage of the West

Let’s head back into the heat again this week and explore another warm, dry ecosystem. Sage scrubland is semi-arid and unless you live there, you probably aren’t familiar with it. Like the desert, it can appear to be devoid of life unless you know where to look.

Sage scrubland in Idaho (USFS)

The ecosystem is defined by sagebrush being the dominant plant species with hot, dry summers and cold winters. Most precipitation is winter snow and spring rain. Sage scrubland ecosystems are found in the Intermountain West and California’s coastal chaparral ecosystem.

Many animals call the sage scrubland home. Small mammals and reptiles are well represented in the list of fauna. The endangered black-footed ferret is among them, and it was in Wyoming’s sage scrubland that a colony was discovered after the species had been given up as extinct. They were all captured and put into a captive breeding program which has seeded recovery efforts throughout the West. Larger mammals include elk, mule deer, and pronghorn.

Black-footed ferret (USFWS)

Birds of prey are common inhabitants of this ecosystem. The sage grouse (of course) also calls this area home. This threatened bird relies heavily on the sagebrush for its survival. Not only is sage a staple if its diet, it also uses the plant for cover.

Male sage grouse (USFWS)

Sagebrush, the dominant plant in this ecosystem, provides sustenance for species other than the sage grouse. When the deer and the antelope aren’t playing, they can be found nibbling on sage brush. It is especially important during the winter when other lower plants are buried under snow. 

Like so many other habitats in the world, sage scrubland is in danger. Development destroys or fragments the habitat. Oil and gas drilling scare away resident critters and disrupt migrations. Invasive plants crowd out the natives and create a vegetation density conducive to fire. While sagebrush can withstand low intensity fire, hotter fires fueled by invasive cheatgrass destroys it. Agriculture converts sage land to crop land.

Sagebrush in Oregon

There is hope, of course. Most sage scrubland is in sparsely populated areas so it is disappearing at a slower pace than other areas. Agriculture, which can be destructive to this ecosystem, can also be a conservation partner. It makes a great low-maintenance rangeland if done sustainably.

Sage scrubland is an important, but unheard of ecosystem. Most people think of the Intermountain West as just drive-through or fly-over country. Eastern Washington is a million shades of brown from 30,000 feet. But while driving across eastern Oregon, southern Idaho, and northern Wyoming I was quite taken with the beauty and solitude of the seemingly endless sea of sage.

This week's information comes from US Fish and Wildlife Service, Oregon Department of Fish and Wildlife, and Wyoming Game and Fish Department.

Species of the Month

This month’s species of the month celebrates independence with America’s newest national symbol, the bison, which became the national mammal in 2016. For the Plains Indians, the bison meant life. To me, it represents strength, power, and resilience as it was hunted nearly to extinction but has since recovered to an estimated population of 31,000 wild bison. While it’s a far cry from the tens of millions roaming the prairies and woods in the 19^th century, it is much better than the thousand or so that remained in 1889. 

Bull bison at Yellowstone

Scientific name: Bison bison

Kingdom: Animalia (animals)

Class:   Mammalia (mammals)

Order: Cetartiodactyla (even-toed ungulates)

Grazing bison

Range: Historic range runs from Alaska and northern Canada west of Hudson Bay south to northern Mexico, Intermountain West east to the Appalachians. Current range is limited to national parks and preserves, private wildlife conservation areas, and private ranches scattered about the US, Canada, and Mexico.

Habitat: Forest and/or prairie habitat; can be found in tallgrass, shortgrass, or mixed grass prairies

Lifespan: 15-20 years

Diet: grasses, sagebrush

Bison herd at Custer State Park in South Dakota.
The orange colored calf is known as a "red dog".

Predators: wolves, mountain lions, humans

Conservation Status: Listed as near-threatened due to reliance on conservation for survival by IUCN. Listed as endangered under ESA.

Other Information: Bison were long a source of sustenance for the Plains Indians, who used every part of the body for food, clothing, shelter, and tools. They were hunted nearly to extinction in an effort to subdue the tribes that depended on them. Of the roughly 31,000 wild bison, only a small percentage are purebred. The rest are hybridized with domestic cattle. Wild bison herds are scattered throughout the West. Notable herds are found in Yellowstone, Wind Cave, and Wood Buffalo National Parks. There are two subspecies of bison: the familiar plains bison and wood bison, which lives in northern forests of Alaska and Canada. Bison grazing influenced plant communities, which in turn affected what other animals lived in the ecosystem. Bison form segregated herds based on age and sex. Male herds are smaller than female herds, although more males will join as the rut approaches. The rut happens in late summer/early fall. A dominant bull controls a female harem, and younger bulls will challenge him. A bison’s shoulder hump is a mass of muscle that helps support the large head. The giant head works as a snow plow in the winter, clearing snow off the grasses. Despite their docile appearance, bison are capable of inflicting serious damage. They are fast- they can run up to over 30 miles per hour and have no problem using their horns. Keep your distance.

Resting captive bison in Washington

Lamar Valley bison at Yellowstone

Lamar Valley bison at Yellowstone

This week's information comes from University of Michigan's Animal Diversity Web, The Nature Conservancy, US Fish and Wildlife Service, and Environment News Service. 

Road Trip Adventure- Volcanic Idaho

Continuing on our road trip, this week’s Nature Minute takes us to Idaho’s Craters of the Moon National Monument and Preserve. Located in south central Idaho, the area was once a hotbed of volcanic activity. Ancient lava flows created a unique landscape and habitat. Enjoy this week’s story from the road.

The lava flows that give Craters of the Moon its signature look and name sprang from the Great Rift between 15,000 and 2,000 years ago. The lava beds cover over 1000 square miles, flowing from 25 vents that spewed in at least 8 volcanic events during that time period. Craters of the Moon is the largest of several lava beds in the Great Rift.

Volcanic landscape of Craters of the Moon

Lava in the midground, sagebrush steppe in the
foreground and background

Geological features of the Monument are spatter cones, cinder cones, fissures, lava tubes, and kipukas. The cones and fissures are volcano types. Lava tubes and kipukas are formed by lava movement.

Spatter cones are formed when thick lava is ejected from a volcano. It remains molten when it hits the ground, but due to high viscosity, the blobs of lava do not flow away. Rather, new molten blobs are ejected and they stick together, forming a cone. Cinder cones form similarly, but the lava blobs cool and harden in mid-air, becoming lava bombs (actual geological term). The size and shape of the bombs is dependent on gas content.

Spatter cone (NPS photo)

Fissures are large volcanic cracks in the ground. A full-length fissure eruption is probably the rarest of all volcanic eruptions. Spatter and cinder cones can form in a fissure if it becomes clogged in any area. 

Lava tubes form when the outside of a lava flow cools, forming a hard rock shell. After the remaining molten lava drains, the hollow tube remains. I have been inside a lava tube, the Ape Cave at Mount Saint Helens in Washington.

Lava tube (Oregon State University photo)

Kipukas are islands of older lava flows surrounded by newer lava flows. Vegetation on kipukas is different from the surrounding lava flow areas. At Craters of the Moon, the kipukas are islands of sage steppe surrounded by black lava rock.

Kipuka (NPS photo)

Despite its barren appearance, Craters of the Moon supports a diverse ecological community. Plants include sagebrush, prickly pear, limber pine, and Indian paintbrush. Animals in the Monument include the pika, sage grouse, pygmy rabbits, northern harrier, and common nighthawk.

Limber pine

While visiting, I observed a northern harrier overhead. I took a nice stroll through the Devil’s Orchard, so named by a 19^th century preacher who failed to see beauty in Creation and declared the place to be a garden fit for the devil. I enjoyed seeing the lichen that are working around the clock to turn rock into soil so larger plants can colonize. The twisted branches of the limber pine, knotted by mistletoe, set against a stark black backdrop made for an eerie sight. I enjoyed my brief visit and would like to return for a more in-depth look around. I chose not to linger because Craters of the Moon was the undercard for the main even, Yellowstone.

Limber pine with "witch's brooms"

Polished lava rock with swirls

Hardened slow-moving lava flow

Information this week comes from the National Park Service about kipukas, including the picture above. Great Rift information comes from a paper by the folks at Idaho State University. Photo credits go to National Park Service (spatter cone) and Oregon State University (lava tube). All others are my own.