Bichat speaks of a stupefying effluvium (exhalaison hypnotique) by which some reptiles benumb their victims; and Van der Hoeven suggests that the above-described suicidal infatuation of birds and rodents may be nothing but the well known self-sacrificing courage of the nest-mothers in defense of their helpless brood; while some modern ophiologists (Keyserling, Cabanis, and Dr. Hitchcock) have rejected the idea that such sluggish reptiles as moccasins and rattlesnakes—unless assisted by accident or the artificial arrangements of captivity—could capture more agile animals than frogs or moles.
Source: wiktionary