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These adorable little fellows are among the nine Mexican wolf pups born at Chicago’s Brookfield Zoo in April. Seven of the cute critters - who will grow up to be rather more fearsome - were successfully placed into wild dens in New Mexico in May as part of the Mexican Wolf Recovery Programme aimed at bolstering the subspecies' population in the southwestern United States and Mexico. At just 10 days old, the pups - six males and one female - were carefully transported to New Mexico. During their journey, two animal care specialists and a veterinary technician from Brookfield Zoo ensured the pups were well-fed and kept warm. Upon arrival in New Mexico, members of the Mexican Wolf Interagency Field Team covered the pups with the scent of similarly aged wild pups to integrate them seamlessly into their new dens. Each pup was swabbed for DNA and given a studbook number before being placed back in the den. Biologists monitored the radio-collared mothers to ensure they accepted the zoo-born pups. This fostering process, which improves the genetic diversity of the wild population, marked a milestone this year with the 100th pup placed in the wild since fostering began in 2014. Two additional female pups from the same litter remain at Brookfield Zoo. The Mexican wolf, the rarest and most genetically distinct subspecies of grey wolf in North America, once numbered around 4,000 across central and northern Mexico and the southwestern U.S.