World_of_Animals_Issue_46_2017

Animal
answers
Send your animal questions to us at:
questions@animalanswers.co.uk
How do kangaroos
pause pregnancy?
Kangaroo mums can keep a joey in
reserve; while one baby is growing in the
pouch, a second one waits in the uterus
ready to take its place. And it’s all down to
a feedback loop in their hormones.
If there’s already a joey in the pouch, the
action of it suckling triggers the release of
a hormone called prolactin, which halts the
development of the embryo. The fertilised
kangaroo egg can divide until it reaches a
ball of 100 cells, but after that it stops until
there is room. When the bigger joey is old
enough to leave its mother’s pouch, the
hormone balance changes and the embryo
can continue developing.
This clever adaptation means that the
female kangaroo will always have room for
her new arrival, but she won’t need to wait
until her older joey has left to find a mate,
maximising the number of little kangaroos
she can successfully raise.
There’s only room
for one joey in the
pouch at a time
What’s the difference between
venomous, poisonous and toxic?
These terms can be confusing, but there’s
a simple way to remember the difference. If
something bites or stings you, causing you
harm, it’s venomous. If you eat something
and it damages you, it’s poisonous.
A toxin is a substance that causes harm
when it enters the body through inhalation,
ingestion, injection or absorption. Poisons
can be inhaled, ingested or absorbed, while
venoms are injected via an animal’s teeth,
sting or barbs.
Poison dart frogs are poisonous because
they secrete batrachotoxin. Gathered from
the beetles they eat, it disrupts nerve and
muscle cells, resulting in heart failure.
Pit vipers, on the other hand, inject their
toxins with a bite. They make several kinds
of molecules called metalloproteinases.
These are enzymes - biological catalysts -
that break down other molecules inside the
victim’s body. Many cause bleeding, while
others directly kill cells.
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