A cowboy wrangler leads a pack train of horses up the South Kaibab Trail in Grand Canyon National Park, UNESCO World Heritage Site, Arizona, United States of America, North America

On the Trail with Pack Mules transporting gear to Kyanjin Gompa, Langtang Valley trek, Himalayas, Nepal, Asia

Traditional pack mule transportation in a Himalayan Village on the Langtang Valley trek, Himalayas, Nepal, Asia

On the Trail with Pack Mules transporting gear in the Himalayas, Lang Tang Valley trek, Himalayas, Nepal, Asia

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle, Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle, Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle, Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle, Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle Northern Norway

Alaskan Huskies dog-sledding at Villmarkssenter wilderness centre on Kvaloya Island, Tromso in Arctic Circle, Northern Norway

Young woman hiking, climb to Plumsjoch in the Karwendel Mountains, Rissbachtal, Tyrol, Austria, Europe

Ascent of Piz Boe Mountain on the Piazzetta Climbing Route, Dolomites, Alto Adige, Italy, Europe

Ascent of Piz Boe Mountain on the Piazzetta Climbing Route, Dolomites, Alto Adige, Italy, Europe

Ascent of Piz Boe Mountain on the Piazzetta Climbing Route, Dolomites, Alto Adige, Italy, Europe

Climbers ascending Mt. Marmolada, Dolomites, Westgrat fixed rope route, Mt. Marmolada in the back, Trentino, Italy, Europe

Female hiker walking on a snow slab, on the Laugavegur hiking trail, Hrafntinnusker-Álftavatn, Fjallabak Nature Reserve, Highlands of Iceland, Iceland, Europe

Pack dogs, sled dogs, Alaskan Huskies, carrying dog packs, backpacks, wooden boardwalk, swamp, Chilkoot Trail, Chilkoot Pass, Alaska, USA

Peeled bark, in the back the peeled spruce logs (Piceoideae) Neunhof, Middle Franconia, Bavaria, Germany, Europe

Pack dog, sled dog, Alaskan Husky, carrying dog packs, backpacks, wooden boardwalk, swamp, Chilkoot Trail, Chilkoot Pass, Alaska, USA

Pack dogs, sled dogs, Alaskan Huskies, carrying dog packs, backpacks, coastal rain forest, Chilkoot Trail, Chilkoot Pass, Alaska, USA

Peeled bark, in the back the peeled spruce logs (Piceoideae) Neunhof, Middle Franconia, Bavaria, Germany, Europe

Supply of Willersalpe alp only by horses, Hinterstein, Hintersteiner Valley, Bad Hindelang, Allgaeu, Bavaria, Germany, Europe

Young woman hiking, backpacking, hiker with backpack, snow field, descending towards summit of historic Chilkoot Trail, Chilkoot Pass, Crater Lake behind, alpine tundra, Yukon Territory, British Columbia, B. C., Canada

Young woman resting, hiker with backpack, water bottle, panorama, deep lake behind, historic Chilkoot Trail, Chilkoot Pass, alpine tundra, Yukon Territory, British Columbia, B. C., Canada

Supply of Willersalpe alp only by horses, Hinterstein, Hintersteiner Valley, Bad Hindelang, Allgaeu, Bavaria, Germany, Europe

Timber industry in the forest near Meinerzhagen, Sauerland, North Rhine-Westphalia, Germany, Europe

Local man with a donkey, Chapada Diamantina, near Salvador de Bahia, Bahia, Brazil, South America

Young woman jumping across a creek, hiking, backpacking, hiker with backpack, historic Chilkoot Trail, Chilkoot Pass, near Crater Lake, alpine tundra, Yukon Territory, British Columbia, B. C., Canada

Tree trunks on a forest road in Welzheim, Baden-Wuerttemberg, Germany, Europe

Yaks pack good and supplies from Everest Base Camp and Gorak Shep down the trail to lower elevations in the Himalayas.

Female hiker waits for pack horses to pass on the South Kaibab Trail in Grand Canyon National Park north of Williams, Arizona May 2011. The South Kaibab Trail starts on the south rim of the Colorado Plateau and follows a ridge out to Skeleton Point allowing for 360-degree views of the canyon then down to the Colorado River. At the Colorado River the trail connects with the North Kaibab trail as part of the Arizona Trail system, that crosses the state of Arizona from Mexico to Utah.

Local man walking behind a pack donkey near El Potrero Chico, Mexico.

Rolando Garibotti skis with a pack on the Boreas Pass trail which crosses the Rocky Mountains from Breckenridge to Como, Colorado. The trail is part of the Rails to Trails system and follows an old railroad grade. The trail is also part of the 10th Mountain Division Hut System, with a hut called the Section House located along the trail at the top of Boreas Pass. The trail is within Pike-San Isabel National Forest

Biospheres Expedition, Low Tatra Mountains, Slovakia

Portraits are of John Indrehus (with his pack horses) and outfitter Wayne Fairchild ( with white baseball cap) of Lewis and Clark Trail Adventures, on the Lolo Trail in Idaho between Wendover Creek and Snow Camp.

Horses and riders lead a string of pack animals near Sixty Lake Basin in King's Canyon National Park, California, USA, California, United States of America

Wolf

Female cyclist along a pathway with rolling hillside vineyards and mist in the river valley, North of Remich, Luxembourg

Female cyclist along river pathway with mist in the river valley looking over trees along river bank, North of Remich, Luxembourg