Old birds become worn and rusty too
Katherine A. Herborn, Francis Daunt, Britt J. Heidinger, Hanna M. V.
Granroth-Wilding, Sarah J. Burthe, Mark A. Newell and Pat Monaghan
While we know that our own bodies
deteriorate as we get older, relatively
little is known about these processes
in wild animal populations. Much of
what we know about aging in other
species comes from research on
species with relatively short lifespans,
such as insects and rodents, which can
be studied from birth to death in
laboratories. To determine whether
the same patterns of aging occur in
long lived organisms requires long
term programmes and long scientific
careers. Moreover, understanding
aging under natural conditions, instead
of in the relatively homogenous and
safe laboratory environment, presents
the additional challenge of finding the
same animal at different stages of its
life in the wild. One reason why
individuals deteriorate with age is
thought to be akin to rusting – that is
accumulated oxidative damage to
tissues. The term ‘oxidative stress’
describes a state where oxidising
molecules, which are mostly a natural
by-product of metabolism, exceed the
body’s level of antioxidant defences,
and thus are free to react with and
damage body tissue. We examined
age-related changes in oxidative stress
exposure in the Isle of May population
of a long-lived seabird, the European
Shag (Phalacrocorax aristotelis).
Chicks were given unique coloured and
lettered leg rings, allowing them to be
recognised throughout their lives.
Over three consecutive breeding
seasons, we collected tiny blood
samples from individuals aged from 2
to 22 years at the start of the study.
Individuals of all ages showed an
increase in oxidative stress exposure
from one year to the next, and those
Family of Isle of May shags, Phalacrocorx
aristotelis ©Lucie Bernardova
with the highest levels were more
likely to die. This is consistent with the
expectation that older individuals will
invest less energy and resources into
self-maintenance in favour of more
investment into reproduction, as a last
ditch attempt at passing on their
genes. Our study, therefore, provides
a rare insight into the process of aging
in a long-lived species; they become
rusty much like ourselves.