"Trish Brown" wrote in message
...
jules wrote:

snip

Probably the mice do too, but they are less likely to survive where
there is snakes and owls and other birds off prey.

snip

jules


Y'know, I often wonder about that. I reckon lots and lots of native
carnivores would kark it if it weren't for the introduced rabbits and
mice. I know our local black snake has been growing fat on the mouse
plagues we get occasionally. I wonder what would keep him going if the
mice weren't there?

there is always a predator/predatee(? is that a word?) balance that forms
after a while. without so many mice, the snake may well live elsewhere - or
possibly not exist at all as his mother may have lived elsewhere/not had
enough to eat in order to reproduce. more likely, without exotic mice, he'd
be eating something else which presently do not live there, because the mice
live there instead & have crowded them out. i don't think we can _know_ what
(for e.g.) your backyard or mine would be like had mice, cats, english
sparrows, & every other thing _not_ been introduced by other people in the
past. there's no way to tell what would have happened once something else
entirely has incontrovertably happened instead. however, quite clearly,
australia would have black snakes aplenty in the absence of european mice.
they'd be eating something else & their habitat patterns might just be
different accordingly, or exactly the same but with a different food
source - or, in the absence of so many humans transporting mice about, there
may have been so many snakes in your area that they reach plague-like
proportions themselves, & subsequently receive a population correction from
mother nature because there is not enough to eat... (or any one of a number
of other hypothetical possibilities). nature keeps animals (and plants), &
the animals or diseases that kill them, in a balance. (it might not be a
balance we approve of, but our opinions actually don't count :-) european
mice, without enough predators (say, cats, dogs & humans - themselves all
introduced species as well), will crowd out similar indigenous species
(which your snake would eat, except that they're not _there_ because of
mice.) there'd have just been a different balance & different animals
occupying different places, but we can't know what it might have been like.

That's why I have no problem letting the mice go from my humane traps. The
likelihood of their survival away from their colony of origin is slim to
put it mildly

er, no..!
how have mice come to prosper? by moving away from their origins (whether by
accident or on purpose) & expanding their habitat.

by my observation, there are two groups of animals in the world - those
which prosper by being smart & adaptable (e.g. humans or dogs) & those which
aren't very bright but prosper by sheer reproductive capacity (mice,
rabbits, kangaroos). with the latter, they may thwart themselves at every
turn & be killed in droves by predators, yet survive in massive quantities
because they have so many babies, a few of whom survive to reproduce. the
animals which plague us tend to be of the latter variety. they are just
adaptable enough to make sure a few of them always survive a new situation.
they are always able to find other individuals to mate with, because those
individuals are already nearby, having previously been relocated, or
relocated themselves, for whatever reason.

then again, i suppose there is a third group of animals which are neither
wickedly intelligent, nor are they highly reproductive. they would be the
animals which either become endangered if someone or something moves in on
them, or become domesticated if they are useful to us & placid enough.

and I figure most of them will end up in a
kookaburras dinner menu or a snake's or a kestrel's.

i think a lot of them probably do, but there will always be enough
survivors, of that you can be sure. if you release a thousand mice in a
lifetime, & only 50 of them subsequently survive to have offspring, there
are still a LOT more mice in the world than there would have been had you
killed all 1000 instead of letting 50 survive.

Not saying we need to welcome the bloody-introduced-species, just
pondering the fates of the mice that we catch...

you're probably right in that most of them are caught pretty quickly. it's
the ones who aren't caught who go on to colonise new areas. which clearly
happens, otherwise australia would not be covered in a thick coating of
mice, rats, cats, goats, foxes, & every imaginable kind of feral pest!!
:-)
kylie