|Why does a dead rat get mold after a few weeks?
There are always mold spores wherever you go
and if they land on something they can eat, they
start growing. Normally an organism such as a rat
has an immune system that will kill any bacteria,
fungi, or viruses that attack it. However, once an
organism dies, it can no longer fight off invaders
and it becomes the food source of whatever gets to
it first.Dead animals are the perfect food
source for bacteria and fungi because all of
the molecules they need are “pre-made” by the dead
animal so they can get them easily. The special
thing about molds, which are a type of fungus, is
that they specialize in eating dead animals and
plants. In this way, they are basically the
garbage-men of the living world.
The reason that it takes a few weeks is that it
takes a while for the mold to grow big enough that
you can see it. You can only see the mold after
its “full-grown” since the green color is from the
part of the mold that sends spores into the air.
I’m surprised it took that long for the dead rat
to get moldy.
We are hosts to all sorts of tiny life
forms, bacteria, fungi (including mold), viruses,
etc. There are actually more bacterial cells
in and on your body right now than your own cells.
While we’re alive, our immune systems keep all of
these other life forms in check. Sometimes our
immune systems can’t keep up and we get sick.
After we die, there is no security system to
keep all of these other life forms in check. They
can just take over. They can even be joined by
decomposers—living things that eat dead stuff.
Flies lay eggs that hatch out as maggots and eat
the body. Beetles eat the decomposing bodies and
lay their eggs too. Vultures aren’t usually
interested in something as small as a rat, but eat
larger carcasses (dead animals).
If conditions are warm and moist, things can
break down really fast. If the environment is very
dry, the decomposers can’t do their jobs.
Carcasses can dry out and become mummies.
Anyone who was not grossed out by this may want
to explore how biology is useful in fighting
crime. Specialized biologists study how bodies
decompose under various conditions so that they
can determine time and place of death. It just
may be the career for you.
Thanks for asking,
We are surrounded by microorganisms – bacteria and
fungus spores smaller than we can see, on surfaces
and in the air we breathe. These microorganisms
are typically dormant until they find the food and
water they need to grow and reproduce. A rat (and
any other plant or animal, including you) has
defenses that keep these bacteria and fungus from
growing on them. Some are passive, like tough skin
and hair that make it difficult for microbes to
grow. Most plants and animals also have friendly
bacteria that live on their skin and fight off
other microbes that might harm them. Some defenses
are active, like the white blood cells in your
immune system or fevers that make it difficult for
bacteria or fungus to live inside the body.
When a rat dies, it no longer actively defends
against these microbes, which begin to break apart
cells to get at the water and sugars inside.
Because the rat’s heart is no longer beating,
blood is no longer transporting oxygen throughout
the body, so enzymes and wastes build up in the
tissues and speed the break down of cells. As more
water and nutrients are released from the cells,
more microbes can grow – the most colorful and
distinctive of which are fungal molds. For more
information, check out:
Spores of fungi land on the rat and grow inside of
it, eating the dead body from the inside. The mold
you see are their spore-producing organs to
colonize other dead matter.
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