Frog spawn
t Barton
WTPL/Margare
Big Spring Watch: Frog spawn
Frog spawn, the eggs of the common frog, is a mass of thick, translucent, round balls of jelly.
Within each 1cm clear ball is the small black egg of the common frog.
Up to 5,000 eggs can be laid at once.
Where to record
Why frog spawn?
Frog spawn can be found in ponds, ditches and
slow moving streams; it has even been seen in
puddles.
Frog spawn is popular and easily identifiable;
volunteers have been recording first sightings as
part of Nature’s Calendar since 2000. In 2015, it
will be interesting to see how fast spring moves for
frog spawn, and how this compares with previous
years.
What to record
Record the first time you see frog spawn.
When to record
The date that frog spawn appears can vary
greatly, depending on what spring temperatures
are like and where you live.
In general, frog spawn may be spotted as early as
mid-January or as late as mid-April. Depending
on the local conditions, tadpoles will hatch around
21 days later and will start to grow legs around
16 days after this. In early summer, once the tails
have been absorbed, they emerge from the water
as small froglets.
WTPL/Christine Martin
Our climate is changing; this will produce some
‘winners’, who are well adapted to change, and
some ‘losers’, who cannot adapt quickly enough.
It is possible that frogs will be losers if many are
fooled into spawning too early.
Long-term monitoring of species like the
common frog will help scientists gain a greater
understanding of this issue, and provide
policymakers with hard evidence.
WTPL/Ch
ristine M
ar
tin
Fabulous facts
Frogs rely on garden and countryside ponds for
breeding, although in the non-breeding season they
may roam up to half a kilometre from them. Males
arrive at the pond first and try to attract females
by loud croaking. Successful males grasp females
in a mating embrace and fertilise eggs as the
female releases them. Each female lays between
1,000 and 4,000 eggs.
The common frog is the one kind of frog that is
native to the UK, and it is found in most parts of
the UK. The other, the pool frog, is believed to have
become extinct in the 1990s, though it has since
been reintroduced to a site in East Anglia.
Unseasonably warm weather can sometimes fool
frogs into spawning too soon. We receive records
most years of some exceptional sightings in
November and December.
Frog spa
w
n
If more typical winter conditions return, such early
spawn is vulnerable to freezing while it floats on
the top of the pond. Frogs only mate once per
season so if they are caught out, their breeding
effort for the year is wasted.
Not to be confused with...
Common toad spawn. Frogs lay their
spawn in clumps, but toad spawn is in
strings and it is laid a few weeks later than
frog spawn.
Colder winters reduce the risk of early spawning,
but bring their own problems; frogs that have
hibernated at the bottom of ponds can die if there
is a layer of ice on the pond and oxygen levels
become too low.
WTPL
Commo
n frogs
oad spawn
Common t
ons
media Comm
dsey - Wiki
© James Lin
How fast does spring move?
Nature’s Calendar has teamed up with BBC Springwatch to seek your help in answering the question
‘how fast does spring move?’
Recording tips
Once you have seen a sign of spring, please record it! Remember that you need to register on
the Nature’s Calendar website first.
Registration naturescalendar.org.uk/bswregister
Recording naturescalendar.org.uk/survey/login
Please choose somewhere you visit regularly (at least weekly) to make your record, to help ensure that you spot
when something happens for the first time.
Nature’s Calendar is part of the Woodland Trust. Registered charity numbers 294344 and SC038885
6766 03/15