868 



TIT,\NOTHERES OF ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



time extinguished the bison, the elk, the boar, the 

 capercailzie, and the tortoise (Emys lutaria). 



Poisonous plants. — Domesticated Herbivora gener- 

 ally but not invariably learn to avoid poisonous plants 

 or become more or less immune to their deleterious 

 effects. Generally they are driven by hunger to eat 

 poisonous plants, but there are some exceptions to 

 this rule. 



The theory that deleterious or poisonous plants are 

 resorted to by animals under unusual conditions of life 

 is still to be considered among the possible causes of 

 extinction of wild animals. Poisonous plants are 

 widely distributed. Under the unnatural conditions 

 of extreme cold, drought, enforced migration, starva- 

 tion, etc., they may have influenced extinction, 

 especially on diminished herds. 



Chesnut's observations on plant poisoning among 

 the domesticated animals are summarized in a letter 

 written by him to the author (July 9, 1902): 



So far as 1113- observations have extended the chief circum- 

 stance leading to death from poisonous plants is an irregularity 

 of the food suppl}' caused by more or less unusual conditions. 

 It does not seem reasonable to suppose that wild animals are 

 frequently poisoned in their native grazing grounds. Sudden 

 disasters, however, might drive them from their feeding grounds 

 into pastures quite unfamihar to them, where they would 

 undoubtedly be more or less at a loss to distinguish between 

 poisonous and nonpoisonous plants. 



Hornaday, on the other hand, in a letter written to 

 the author in 1906, observes: 



There appears to be no evidence that any wild herbivorous 

 species ever has been seriouslj' affected by eating poisonous 

 plants. All the cases cited by Chesnut and other authors under 

 this head are domestic species onlj-. Tame species have, 

 through man's care for their wants, lost the discriminating 

 instinct which protects the wild species. For example, the 

 antelope, buffalo, elk, and mule deer never eat loco weed on the 

 southern plains; the deer of the Appalachian region do not eat 

 the leaves of the laurel, which are so fatal to the domestic goat. 



Beebe in a letter to the author dated January 17, 

 1912, observes: 



Darwin was in error when he stated " that "The root of the 

 Aconitum napellus becomes innocuous in frigid climates." 

 Hooker was also wrong when in the "Flora of British India" 

 he lumped a number of distinct species under the name Aconi- 

 tum napellus, which, as a fact, does not occur in British India. 

 The poisonous aconite of Sikhim is A. ferox. In Nepal four 

 varieties of A. napellus are found, two of which (A. napellus 

 and A. rigidum) are poisonous and two (A. multifidium and 

 rotundifolium) are eaten by Bhutian hill men, and also by the 

 Impeyan pheasant (Lophophorus) and panda (Aelurus). The 

 domestic sheep can not distinguish between the poisonous 

 and nonpoisonous forms (sheep are protected by muzzling); 

 the wild creatures can distinguish. 



Wild animals are certainly protected, both by in- 

 stinct and by experience, from poisoning by plants. 

 This fact, however, does not exclude the possibility 

 that, imder certain harsh or unusual conditions of 



«" Animals and plants under domestication, Westminster ed., II ,p. 255. 



life, deleterious or poisonous plants may have has- 

 tened a diminution of their number. There may also 

 have been occasions when such plants constituted a 

 new and unfamiliar danger. Some molds and smuts 

 that appear on the Gramineae are periodic, not 

 constant; under changing geographic conditions cer- 

 tain narcotic plants may have been iutroduced and 

 spread rather suddenly; ergot, a morbid growth arising 

 from a diseased condition of the ovary of various 

 grasses, produced by a fungus of the genus Claviceps, 

 may cause diseases of the hoof. We must also con- 

 sider the effect of the introduction of certain poisonous 

 plants that do not injure the parent but may injuri- 

 ously affect or kill the suckling young. The distribu- 

 tion of most of these plants is related to increase or 

 diminution of rainfall. 



There are also marked variations in the degree of 

 immunity. Linnaeus, in his "Tour in Scania," as 

 cited by Lyell (1872.1, p. 440), tells us that goats 

 were turned into an island that abounded with 

 Agrostis arwndinacea, which they would not eat, so 

 that they perished by famine, but that horses which 

 followed them grew fat on the plant. The goat, he 

 also says, thrives on meadow sweet and water hem- 

 lock, plants that are injurious to cattle. Observa- 

 tions in South Africa (Hutcheon, 1906.1) give similar 

 results. The " chinkerinchee " plant {Orniihogalum) 

 is poisonous to horses, and one of the ragworts (Senecio) 

 is an irritant causing cirrhosis of the liver in cattle 

 and horses. Tulps (species of Moraea) also give 

 trouble. Most of the cattle thus lost are not accus- 

 tomed to the country or are very hungry trek cattle. 



Fatal effects of wet seasons. — Chesnut (1901.1, p. 19) 

 observes that most of the plants that are especially 

 poisonous during the wet season are so much shriveled 

 in the dry season as to be absolutely unpalatable. 

 Sheep owners have accordingly found that mountain 

 ranges whose growths are extremely dangerous for 

 sheep during the wet season of early summer are Ciuite 

 safe from July to September, inclusive. Similarly, 

 during -the wet season and when feeding immediately 

 after heavy rainstorms domesticated animals are more 

 likely to pull up the roots of plants than when the 

 ground is dry, and (idem, p. 26) in many poisonous 

 plants it is chiefly the roots that contain the poison. 



Snowstorms as affecting eating of poisonous plants. — 

 After heavy snowstorms, when the grass is covered by 

 snow, it often happens that only the taller species 

 of plants are exposed (idem, p. 27). At such times 

 the poisonous larkspurs {Delphinium glaucum) are 

 greedily eaten by cattle, which at other times avoid 

 these plants. This danger is increased by the fact 

 that ruminants do not feel at ease so long as their 

 stomachs are not full, and they are inclined to eat 

 anything in sight after a snowfall. In seasons of 

 drought certain poisonous leguminous plants remain 

 green and tempting after the grasses have become 



