The alphas mate in February, and pups are born in April in underground dens. A pack may have as many as 10 den sites on its territory and may move young pups from den to den, perhaps to avoid other predators or to reduce the chance of insect infestation. Coyotes use dens handed down from previous generations. The Bison Peak Pack in 1992 was using a den at which biologist Weldon Robinson had captured pups in 1946. Crabtree has discovered that at least 75 percent of the dens in the Robinson study are still in use.
Coyotes use dens only for sheltering pups.
At 12 weeks of age the pups begin to travel with the adults, and the pack abandons den life. Kazia Hatier, one of Crabtree's graduate students, found that the highest pup mortality occurs from mid June to early August as the pups enter the world beyond the den. Generally, only two pups from an average litter of six survive into adulthood. Much of pup success depends on food availability. Alphas always eat first.