Summer hibernation induced by cryogenically preserved blood "trigger"

Summer hibernation induced by transfusions of blood (serum, cells, or whole blood) from hibernating ground squirrels and woodchucks demonstrates that (i) this "trigger effect" can be preserved cryogenically in vitro for at least 5 months, (ii) it cross-reacts between these species of hibernators, and (iii) its effectiveness relates to the donor's previous hibernation history.