These two baby jackrabbits were orphans.
Desert Duets: Black-tailed Jackrabbit Babies Web Page
Baby jackrabbits are called "leverets." Their mothers are called "does." Most litters have 2 to 4 leverets, but there can be as many as 8 young in each litter. The doe gives birth to the leverets in a shallow dug-out called a "form" or in a thicket bush. She often puts her leverets in different hiding places to protect them from predators.
Leverets are born with their eyes open and with all of their fur. They are active and independent from the beginning, but their mothers nurse them for the first 12 weeks of their lives. To help their babies stay safe, mothers only feed their babies in the dark to keep them out of sight of predators.