|A pronghorn near Fort Rock, Oregon|
The antilocaprids evolved in North America, where they filled a niche similar to that of the bovids that evolved in the Old World. During the Miocene and Pliocene, they were a diverse and successful group, with many different species. Some had horns with bizarre shapes, or had four, or even six, horns.
In Africa, the bovids evolved many ruminants which look like deer (convergent evolution). True deer are a different mammal, and do not live in the southern continents. For example, in Africa they are replaced south of the Atlas Mountains by bovids.
The pronghorn is the fastest land mammal in the Western Hemisphere, with running speeds of up to 90 km/h (55 mph). It is often called the second-fastest land animal, second only to the African cheetah, and it can keep up high speeds longer than cheetahs.
The pronghorn has a yellowish-brown to reddish-brown colored fur with a white underside, and white stripes on the neck and around the mouth. Male pronghorns also have black markings on the neck and face. The males have horns that are up to 25 cm long. Females usually have no horns; if they have horns they are very short.
Pronghorns can be active at any time during day or night, but they are mostly active during twilight. Pronghorns eat grass, but also leaves and herbs. Pronghorns have the ability to digest poisonous plants. This is due to their large liver, which helps in the filtering of toxins.
In summer, adult male pronghorns fight with other males for a territory. In this territory the male keeps a group of females with which he mates in September. Adult males go to the extremes in fighting each other to win over the female by fatally injuring the other pronghorn and determining which male is stronger. Young males that do not yet fight for a territory form small groups, and old weak males live alone. Females live in groups of about 20 animals. When the female is close to giving birth, it leaves the group for a time to give birth to its offspring.
After a pregnancy of 81⁄2 months the female gives birth to 1-2 young, seldom three. The new-borns hide for three days, and after a week they can run with their mother. A pronghorn baby has grey fur, and after three months it has the adult coloring. They drink milk for 5–6 months, and start to eat grass after three weeks. Females become mature when they are 15–16 months old, and males become mature when they are 24 months old.
The pronghorn's similarity to deer is an example of convergent evolution, and it is like the parallel between deer and some African bovines.
Pronghorns were hunted almost to extinction by men with guns. They were saved by interested people. On January 26, 1931, President Herbert Hoover signed the executive order for the refuge. On December 31, 1936, President Franklin Roosevelt signed an executive order creating a 222,000-hectare (549,000-acre) tract; this was the true beginning for pronghorn recovery in North America.
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