The Sonoran Desert Toad

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Bufo alvarius

Bufo alvarius aggressively fight a skunk

When a large female B. alvarius was placed in the cage with the Mephitis mephitis (Striped skunk) it was immediately attacked by the skunk in the manner described. The toad, however, was strong enough to escape from under the weight and grasp of the skunk and in two quick leaps covered a distance of about three feet. The skunk immediately followed the toad and upon the second approach the latter raised itself high on all four legs, inflated its body greatly with air, bent the head downward and inclined the body forward so that the dorsal surface was towards the skunk. This was followed by a very audible hiss from the toad as it slowly forced air from its lungs. The skunk approached more closely, sniffed at the toad and then backed away. The toad was left in the cage with the skunk for twenty-five minutes and except for occasional sniffing activity on the part of the skunk, the toad was not disturbed. On each approach of the skunk the toad would assume the defense posture and hiss audibly. Depending upon the movements and approaches of the skunk the toad would attempt to adjust its position so that the head and dorsum were facing towards the antagonist. On occasions of apparently extreme attempts at this defensive posture one the of the forelimbs would be completely elevated from the substratum as the other was gradually flexed in an effort to keep the dorsum towards the skunk, especially when the latter would approach closely with the head lowered. Each time the skunk would react to this by backing away and, for a short time at least, giving no attention to the presence of the toad.

Following the removal of the toad used in the above experiments a smaller female B. alvarius was placed in the cage and the skunk displayed immediate interest and approached it. This toad exhibited the "typical" defense posture and actually leaped at the skunk from this position. The release of two more B. alvarius into the cage stimulated the attack upon one of these by the skunk, which pinioned the toad with its forefeet. This toad was able to escape and assumed the defense posture. The skunk retreated and as it moved away passed near the large female used in the first part of these observations. The latter toad jumped at the skunk, hitting it in the flank. A second jump by this toad immediately followed and this time hit the skunk in the neck region. A third attempt missed the skunk. These leaps were a butting action and the mouth of the toad remained closed. At no time did the skunk appear frightened, but it was wary of the toads. Repeated experiments of this type soon resulted in conditioning the skunk so that adult B. alvarius would be ignored after a momentary initial interest when the toads were introduced to the cage. The skunk continued to feed upon Bufo woodhousii, Bufo boreas and adult Rana catesbeiana without hesitation.

On another occasion a medium-sized female B. alvarius was placed in the cage with the skunk and although the skunk seemed aware of the toad, it displayed a complete lack of interest in it. A second female B. alvarius was also placed in the cage and leaped in the general direction of the skunk without any apparent intent. The skunk immediately assumed a defensive posture by turning its posterior towards the toad and raising the tail as if to spray. There was no indication of any defensive behavior on the part of the toads on this occasion. A Rana catesbeiana of similar coloration and a size intermediate to the two B. alvarius already in the cage was introduced. The bullfrog, after one jump in the direction of the skunk, was immediately attacked and pinioned against the floor of the cage by the skunk, which then continued the scratching and scraping with the front feet and began eating the frog before it was dead. After the Rana had been partially eaten it was forcibly taken form the skunk. The skunk then chased hurriedly and excitedly about the cage, but yet refused to attack the two B. alvarius present. Throughout the attack on the Rana the toads appeared undisturbed by the skunk's activity and displayed no defensive behavior during this time or after the removal of the bullfrog. The B. alvarius were then removed from the cage.

Within five minutes after the previous experiment an adult Bufo woodhousii and a slightly smaller B. alvarius were simultaneously introduced to the cage. The skunk immediately attacked the B. woodhousii. The latter was taken from the skunk and the smaller B. alvarius nearby was attacked. It is very conceivable that this toad was mistaken for the former one. The toad exhibited no defensive behavior up to this time other than the typical generic defense of inflating itself after the attack. The skunk, during its attempts to kill this toad, would on occasion lick the paratoid glands and respond to this by violently shaking its head and licking the outside of the mouth. The attack continued for a period of ten minutes, during which time the skunk was obviously disturbed by the secretions of the toad. It would react further by baring the canines, snorting and vigorously shaking the head and forepart of the body. Occasionally heaving convulsions without regurgitation were noted. After ten minutes the skunk ceased its attack on the toad and retreated to the opposite side of the cage. The toad then, without any apparent disabilities, hopped away from the point of attack although its back was raw and bleeding slightly. At this time the right paratoid gland was noticeably smaller than the left one but there was no indication of injury to the gland itself. The skunk continued to exhibit normal responses and was not observed to suffer further from any effects of the secretions. Four days later the B. alvarius died, apparently as a result of the wounds inflicted by the skunk.

While being kept in the laboratory the skunk was frequently fed Rana catesbeiana Shaw, Bufo boreas halophilus and Bufo woodhousii. These anurans were immediately accepted as food by the skunk, and as soon as an individual (or more than one) was put into the cage it would be pounced upon. The skunk then began a typical shuffling action of scratching and scraping with the front feet upon the back of the prey. This activity was continued until the victim was all but dead, and often took as long as from five to fifteen minutes depending upon its size. Once the victim has been injured to the extent that no resistance or attempt to escape was apparent the skunk would begin... feeding upon it.

Hanson, Joe A. and Vial, James L. 1956. Defensive Behavior and Effects of Toxins in Bufo alvarius. Herpetologica. Vol 12. pp.141-149. (This excerpt is from pp. 146-148.)