WASHINGTON (WUSA) -- The National Zoo is welcoming the birth of four maned wolf pups at the Smithsonian Conservation Biology Institute in Front Royal, Va.

National Zoo officials say the pups were born to 8-year-old Salina and 4-year-old Nopal. Keepers are monitoring the pups closely because maned wolf pups have a 50 percent mortality rate in the first month, according to zoo officials.

According to the National Zoo, the pups were born Jan. 5 and are the first litter born at the Front Royal location in two years. According to National Zoo officials, 72 maned wolf pups have been born at the Front Royal facility since 1975. The facility currently has 12 wolves, including the pups.

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Researchers are hoping to learn more about the biology of the species from this litter. According to researchers, maned wolves are difficult to breed under human care and the population has declined 20 percent during the last five years in North America. Currently, researchers believe that some of the reproductive challenges are caused partly by gastrointestinal disorders common in the species and may be linked to diet. Salina and Nopal are on a new trial diet that more closely resembles the plant-based diet of maned wolves that live in the wild, say officials.

Maned wolves live in central South America. According to zoo officials, approximately 20,000 are left in the wild.