Webbed toes is the common name for syndactyly affecting the feet. It is characterised by the fusion of two or more digits of the feet. This is normal in many birds, such as ducks; amphibians, such as frogs; and mammals, such as kangaroos. In humans it is considered unusual, occurring in approximately one in 2,000 to 2,500 live births.
There are various levels of webbing, from partial to complete. For example, the rare Hose's Civet, a viverrid endemic to northern Borneo, has partially webbed feet. Most commonly the second and third toes are webbed or joined by skin and flexible tissue. This can reach either part way up or nearly all the way up the toe.
The Western United States, commonly referred to as the American West or simply the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time. Prior to about 1800, the crest of the Appalachian Mountains was seen as the western frontier. Since then, the frontier moved further west and the Mississippi River was referenced as the easternmost possible boundary of the West.
The West mostly comprises arid to semi-arid plateaus and plains and forested mountains.
The fauna of the United States of America is all the animals living in the Continental United States and its surrounding seas and islands, the Hawaiian Archipelago, Alaska in the Arctic, and several island-territories in the Pacific and in the Caribbean. The U.S. has arguably the most diverse fauna in the world and has many distinctive indigenous species found nowhere else on Earth. With most of the North American continent, the U.S. lies in the Nearctic faunistic realm, a region containing an assemblage of species similar to Northern parts of Africa and Eurasia. An estimated 432 species of mammals characterize the fauna of the continental U.S. More than 800 species of bird and there are more than 100 000 known species of insects. There are 311 known reptiles, 295 amphibians and 1154 known fish species in the U.S. Known animals that exist in all of the Lower 48 include white-tailed deer, bobcat, raccoon, muskrat, striped skunk, barn owl, American mink, American beaver, North American river otter and red fox.
Huge parts of the most beautiful parts of the country with the most distinctive indengious wildlife are protected as national parks. In 2013, the U.S. has more than 6770 national parks or protected areas, all together more than 2,607,131 km2. The first national park was Yellowstone National Park in the State of Wyoming, established in 1872. Yellowstone National Park is widely considered to be the finest megafauna wildlife habitat in the U.S. There are 67 species of mammals in the park, including the gray wolf, the threatened lynx, and grizzly bears.
The desert tortoises (Gopherus agassizii and Gopherus morafkai) are species of tortoise native to the Mojave desert and Sonoran desert of the southwestern United States and northwestern Mexico and the Sinaloan thornscrub of northwestern Mexico. Gopherus agassizii is distributed in western Arizona, southeastern California, southern Nevada, and southwestern Utah. The species name agassizii is in honor of Swiss-American zoologist Jean Louis Rodolphe Agassiz. Recently, on the basis of DNA, geographic, and behavioral differences between desert tortoises east and west of the Colorado River, it was decided that two species of desert tortoises exist: the Agassiz's desert tortoise (Gopherus agassizii) and Morafka's desert tortoise (Gopherus morafkai). Gopherus morafkai occurs east of the Colorado River in Arizona as well as in the states of Sonora, Sinaloa, Mexico. This species may be a composite of two species.
The desert tortoises live approximately 30 to 50 years; they grow slowly and generally have low reproductive rates. They spend most of time in burrows, rock shelters, and pallets to regulate body temperature and reduce water loss. They are most active after seasonal rains and are inactive during most of the year. This inactivity helps reducing water loss during hot periods, whereas winter hibernation facilitates survival during freezing temperatures and low food availability. Desert tortoises can tolerate water, salt, and energy imbalances on a daily basis, which increases their lifespan.