Evening star. [volume] (Washington, D.C.) 1854-1972, 1907-08-22
EXTINCTION OF ANIMALS
EXPLAINED BY A COLUMBIA UNI
vERsITY PROFESSOR.
Causes That Have Led to the Blotting
From the Earth Of So
Many Species.

| From the Literary Digest
| What caused the multitudas Of extinct
species, whise remains we find as fossils in
| the earth's strata. to disappear from its
surface? This is one of geology's chief
| problems. So far as mammals are con-
| cerned. 1t Is discussed by Prof. Henry Fair
! field Osborn Of Columbus University in the
! American Naturalist. Prof. Osborn notes
| that Cuvier explained such disappearance
! by supposine great cataclysms-sudden
! geological changes sweeping away life by
! wholesale. These ideas gradually gave way
! before modern theories. according to which
the causes of extinction were not widely
! different from those operating at the pres
i ent time. though even some modern au-
! thorities believe in an occasional cata-
! cysm." Lyeli enumerates causes of ex-
, tinction as follows:
| 1. Competition affected chiefly by the
introduction and extension of new forms.
| >. Agency OF Insects. that is. caterpllars.
ants. iocuSts. in favor,ng checking in
! crease OF plants and thus affecting the
food supply of animals. 3. Intimate re-
! ciprocal relations of animals and plants in
| the delicate balance OF food supply. 4.
| Disturbance Of the equilibrium or balance
| Of nature by the introduction of new in
| sects. plants. vartebrated animals. 5.
Changes In physical geography all ectinS
| geological and botanical provinces by new
! land water connections. facilitating In
| PRODUCTION of new competing forms. 6.
| Causes especially potent in island life.
Unfavorable Conditions.
! Darwin also dismissed all ideas Of catas-
| trophies. and attributed extinction to ces-
| sation Of world conditions of life ia
vorable to the larger auadrupeds. Causes
! quite inapprectable by u.s. he thought.
might determine the extinction of a species
some slight variation in climate. food, or
1 hs>1 he of ami In no
! which we quote, the writer confines HIM
! self to what he calls external causes of
extinction, which include changes In physi-
! cal environment. such as the alteration OF
| land masses ard their connections. and
! changes of climate and changes in the iiv-
/ ing environment. such before station, al
| iteration in food supply. the development
! Of noxious plants Or insects. etc Any such
| changes these might be sufficient to kill
| off whole species In the course OF CEN
! turtles without recourse to any kind OF
| ''catac.ysm." or the possibility of extinc-
! ton by the development Of poisonous vese-
| taton. Prof. Osborn writes:
] 1t Is true, first. that animals generally.
| but not invariably. learn to avoid poison
! Gus plants: second. that they become more
| or less immune to their deleterious effects:
| third. that often it is solely the influence
| OF hunger which drives them to eat poison
| Gus plants This justifies the considera-
| ton of plants under unusual conditions OF
! life among the possible causes of EXITING
| ton. The presence of molds and SHUTS
which appear on the Sramlneae. the intro
duction and spread of certain narcotic
plants. the influence of ergot in causing dis
eases of the hoof. the relations OF poisonous
plants to increased diminished rainfall.
the introduction of certain poisonous plants.
which. while not injurng the parent affect
! and frequently kill the sucking young.
| may be considered.
Action of Noxious Plants.
Poisonous plants widely distributed.
Under the unnatural conditions Of extreme
cold, drouth. enforced migration starva-
tion etc. It Is not impossible that they
may have exerted some influence. especially
on diminishing herds :. DR.. v. X.
Chestnut of the United States agricultural
bureau, states: $50 far as my obser-
vations d,ave extended. the chief circum-
stance leading to death from poisonous
plants is an irregu.arity of tie food sup
ply caused by more or less unusual condi-
tons. 1t does not seem reasonable to sup
pose that wild animals are frequently poi
soned in their native grazing grounds. Sud
from their feeding grounds into pastures
| quite unfamiliar to them where they would
| undoubtedly be more less at a loss to
distinguish between poisonous and nom
poisonous plants.
Sheep owners have accordingly found
mountain ranges which are extremely dan
| gerous for sheep during the wet months
| of early summer. quite safe during the
months from July to September. inclusive.
! Similarly. during the wet season and when
| feeding Immediately after heavy transforms.
| doGnesticated animals are more apt to pull
up the roots OF plants than when the
| ground is dry. and. as is well known. in
| the case of many poisonous plants. 1t Is
the roots which chiefly contain the active
principle.