>Pet rodents, I don't know of any off hand that live as long as ferrets,
>and I am fairly certain pet rats are prone to tumors as well.
 
Yes this is true.  For some reason many smaller animals such as rodents
or animals in the weasel family seem to be more prone to certain types
of tumors, adrenal issues, sensitive lungs, etc... My cousin had pet
rats and they both suffered with facial tumors and did not get well
with treatment so eventually had to be put to sleep.  Rats also are prone
to respiratory infections and don't usually get back to good health after
becoming very sick.  But as Bob brought out, many animals just have
shorter life spans, so some things are to be expected.  Rats, for
example, only live on average 2 - 4 years, although there are exceptions
and some will live longer.  Health issues can also be due to the living
conditions that animals were kept in, or inbreeding, etc... The rats we
got were very sickly when we got them from a pet store and one died days
after bringing it home.  The other 2 are healthy, but that could change
at any moment.  They are both about a year and a half old now, so that
is considered older or middle aged for them.
 
Ferrets have a fairly short life span too, most only living an average of
7 years or less.  So health issues are naturally going to come up.  I
agree with what Bob said about the fancy breeds of dogs and cats often
dying sooner.  "Muts" usually live much longer than "fancy" breeds..and
the fancy breeds often develop problems that are common in specific
breeds, such as bone and joint problems, kidney disease, etc... I think
a lot of it is due to over breeding or inbreeding.  They breed too much
sometimes to get certain traits or colors and often it's at the expense
of the animals.  I think that might even explain why many domestic
ferrets look different in color/size often that their wild counterparts
and probably why many develop health issues early on.  Some breeders are
more concerned with making a buck and worrying about the color of a
ferret than the overall health and wellbeing of the animal.
[Posted in FML issue 4132]