36 BBC WILDLIFE December 2021
constituent part of almost any strandline
at any time of the year, right now there
are fresh ones to be found: November to
January is the whelk’s breeding season.
Somewhere below the low tideline
they amass. Quite how this frenzy of egg-
laying starts is a mystery, but once they get
going, other whelks quickly join in, perhaps
sniffing out tell-tale odours in the water.
The whelks are hermaphrodite, so this
clustered spawning makes sense, because
each snail can release both eggs and sperm,
and they can all fertilise each other.
With each snail engaged in a slow-
motion production line of egg capsules,
each clump or cloud takes anything up
to a week or so to complete. Sometimes
they’re produced by a solitary animal but
sometimes several contribute to form a
single mass – a behaviour that explains the
size differences you see in the egg clusters
that wash up on the shore.
When you next find a sea wash ball,
have a close look. Each of the ‘bubbles’ isUncover the origins of the
mysterious spongy white balls
tumbling around our shorelines
BLOWING
BUBBLES
COMMON WHELK
The popular naturalist, author and TV presenter
reveals a secret world of overlooked wildlifeT
hey catch a diver’s eye in the same
way a discarded plastic bag or yogurt
pot might. An unexpected glimmer
in the gloom of a typical offshore
winter dive. But on closer inspection,
the object is moving. It’s white with
black speckles, like a melted Friesian cow,
and turns out to be dragging a familiar item
around on its ‘back’.
A common whelk or ‘buckie’, Buccinum
undatum, this sea snail, or at least its shell,
is a common sight on almost any shoreline
at this time of the year. In fact, it’s our
largest gastropod, whose dull creamy shell
can grow to be 10-11cm long. But it’s not
the adult snail that fascinates as much as
another related item you can find on the
beach this winter.
The sea wash ball, also known as
‘fisherman’s soap’ or an ‘egg cloud’, is
a strange, off-white cluster of flattish
capsules – imagine a bundled-up sheet of
bubble wrap. They’re the egg clusters of
the common whelk and while they’re aNick Baker’s
HIDDEN BRITAIN
A common sight at this
time of year, sea wash balls
are usually baseball-sized
and contain the eggs of the
UK’s largest sea snail