of
the the 1859 1860 1861 1866 1869 | the 1872 |
357 no less than
295 295 1859 1860 1861 1866 1869 | 295, 1872 |
were destroyed, chiefly by slugs and insects. If turf which has long been mown, and the case would be the same with turf closely browsed by quadrupeds, be let to grow, the more vigorous plants gradually kill the less vigorous, though fully
grown grown 1861 1866 1869 1872 | grown, 1859 1860 |
plants: plants: 1859 1860 1861 1866 1869 | plants; 1872 |
thus out of twenty species growing on a little plot of
turf turf 1859 1860 1861 1866 1869 | mown turf 1872 |
(three feet by four) nine species
perished perished 1859 1860 1861 1866 1869 | perished, 1872 |
from the other species being allowed to grow up freely. |
|
The amount of food for each species of course
give give 1866 | gives 1859 1860 1861 1869 1872 |
the extreme limit to which each can increase; but very frequently it is not the obtaining food, but the serving as prey to other animals, which determines the average numbers of a species. Thus, there seems to be little doubt that the stock of partridges, grouse, and hares on any large estate depends chiefly on the destruction of vermin. If not one head of game were shot during the next twenty years in England, and, at the same time, if no vermin were destroyed, there would, in all probability, be less game than at present, although hundreds of thousands of game animals are now annually
killed. killed. 1859 1860 1861 1866 1869 | shot. 1872 |
On the other hand, in some cases, as with the
elephant, elephant, 1861 1866 1869 1872 | elephant 1859 1860 |
....... 1861 1866 1869 1872 | and rhinoceros, 1859 1860 |
none are destroyed by beasts of
prey; prey; 1861 1866 1869 1872 | prey: 1859 1860 |
for even for even 1861 1866 1869 1872 | even 1859 1860 |
the tiger in India most rarely dares to attack a young elephant protected by its dam. |
|
Climate plays an important part in determining the average numbers of a species, and periodical seasons of extreme cold or
drought drought 1861 1866 1869 1872 | drought, 1859 1860 |
seem seem 1861 1866 1869 1872 | I believe 1859 1860 |
to be the most effective of all checks. I estimated
(chiefly from the greatly reduced numbers of nests in the spring) that (chiefly from the greatly reduced numbers of nests in the spring) that 1861 1866 1869 1872 |
that 1859 1860 |
the winter of
1854-55 1854-55 1859 1860 1861 1866 1869 | 1854-5 1872 |
destroyed four-fifths of the birds in my own grounds; and this is a tremendous destruction, when we remember that ten per
cent. cent. 1859 1860 1866 | cent, 1861 | cent 1869 1872 |
is an extraordinarily severe mortality from epidemics with man. The action of climate seems at first sight to be quite independent of the struggle for existence; but in so far as climate chiefly
|