On the pampas the gauchos frequently take the black-necked swan by frightening it. When the birds are feeding or resting on the grass, two or three men or boys on horseback go quietly to leeward of the flock, and when opposite to it suddenly wheel and charge it at full speed, uttering loud shouts, by which the birds are thrown into such terror that they are incapable of flying, and are quickly despatched. I have also seen gaucho boys catch the Silver-bill (Lichenops perspicillata) by hurling a stick or stone at the bird, then rushing at it, when it sits perfectly still, disabled by fear, and allows itself to be taken. I myself once succeeded in taking a small bird of another species in the same way. Amongst mammals our common fox (Canis azarae), and one of the opossums (Didelphys azarae), are strangely subject to the death-simulating swoon. For it does indeed seem strange that animals so powerful, fierce, and able to inflict such terrible injury with their teeth should also possess this safeguard, apparently more suited to weak inactive creatures that cannot resist or escape from an enemy and to animals very low down in the scale of being. When a fox is caught in a trap or run down by dogs he fights savagely at first, but by-and-by relaxes his efforts, drops on the ground, and apparently yields up the ghost. The deception is so well carried out, that dogs are constantly taken in by it, and no one, not previously acquainted with this clever trickery of nature, but would at once pronounce the creature dead, and worthy of some praise for having perished in so brave a spirit. Now, when in this condition of feigning death, I am quite sure that the animal does not altogether lose consciousness. It is exceedingly difficult to discover any evidence of life in the opossum; but when one withdraws a little way from the feigning fox, and watches him very attentively, a slight opening of the eye may be detected; and, finally, when left to himself, he does not recover and start up like an animal that has been stunned, but slowly and cautiously raises his head first, and only gets up when his foes are at a safe distance. Yet I have seen gauchos, who are very cruel to animals, practise the most barbarous experiments on a captive fox without being able to rouse it into exhibiting any sign of life. This has greatly puzzled me, since, if death-feigning is simply a cunning habit, the animal could not suffer itself to be mutilated without wincing. I can only believe that the fox, though not insensible, as its behaviour on being left to itself appears to prove, yet has its body thrown by extreme terror into that benumbed condition which simulates death, and during which it is unable to feel the tortures practised on it.