Friday, 5 December 2008

Three-headed frog ... not

The alleged three-headed frog

The BBC news
item, Puzzle
over three-headed frog
(originally titled "'Warning' over three-headed
frog") spawned this story that swept the news media and the weblog circuit over
the week following March 5th 2004. Briefly: staff and pre-school children at
the Green Umbrella day nursery, Weston-super-Mare, UK, found the above. After
they'd taken photos and a video, it escaped and was never found. The BBC took
up the story, citing one of their own wildife experts, biologist and presenter
Mike Dilger, as "stunned" and saying "it could be an early warning of
environmental problems" (they published the same factoid in their
children's section). From there, the tale snowballed to
newspapers worldwide. Here's a
of images
at, and videos appeared at CBS News and ITV
West. But was it really a three-headed frog, or a hoax as some have

Three frogs front view

Short answer: neither. In my view, this is just
multiple amplexus, typical frog and toad mating

Mating of Anurans (frogs and toads)
involves the male tightly clasping the female - this is called amplexus - for
hours or even days, prior to externally fertilising her eggs. So we know what
we're talking about, first check out these images of
. The grip is very strong; the male develops special pads on his
thumbs to hold on, and won't let go even if the couple is picked up and
handled. Axolotlman comments (merci aussi!) in this Les Monde des
, that some frogs secrete during amplexus an adhesive
mucus so sticky that it's impossible to separate them without tearing the

Multiple amplexus
Commonly, more than one male grips the
same female. For comparison, see these very clear photos of a
, from David Jones' excellent photo-journal
Frog and Pond
. Note the early March date of these: in southern England, frogs spawn
at this time of year, which supports the amplexus theory. With toads, multiple
amplexus can be be spectacularly weird, as toads generally have many more males
than females attempting to breed, My favourite so far is this wonderfully gross
picture of a toad mating ball involving at least six
toads (by HotShot - merci! - of the
PC forum

Three frogs front and rear view
Three frogs front and rear, tinted

So, the appearance of the
supposed three-headed frog is entirely consistent with multiple amplexus. Have
another look at David Jones' photo of

frogs in embrace
, and then study the above. I interpret it as a smallish
female frog A being clasped by two larger male frogs B and C. The visible arms
belong to A; those of B and C are hidden because they're underneath clasping A
(though B's fingers are visible under A). The legs of A are hidden because it's
smaller than the frogs on top, though there are toes showing below the left
underside of C that may be A's left foot. There are four normal back legs in
view: both legs of C and the right leg of B are on the ground, while B's left
leg is lying on top of C.

Amplexus has
been misinterpreted before by untrained observers, who didn't recognise it and
thought the animals were joined together. See this
by Bernd Heinrich
mentioning how "a woman once brought a thus engaged wood
frog couple to [him], thinking it was a two-headed frog", and this
Massachusetts MetroWest Daily News report,
finds two-headed toad in Hopkinton
, that turned out to be
toads, not mutants
. In the Metro News story it's interesting to read
the complicated, and completely mistaken, analysis of the situation: "Its front
legs have grown into the back of the larger frog, and it appears the bottom jaw
may be connected to the larger toad's head". Eyewitness descriptions and
deductions, then, can be unreliable.

However, according to newspaper
accounts, this new case has also been endorsed by wildlife experts. I am
sceptical even of this, because it appears that the BBC's experts weren't given
the full picture and certainly haven't correlated all the available evidence.
One important point is that some of the photos clearly disprove the claim of
six legs (four at the back and two at the front). The Weston Mercury
picture with its account,
, - and even more clearly, the Sun photo below -
Frog's a
triple jumper
- show a further foreleg (apparently C's front left arm
unclasped). What appears to be two fingers of B's left hand are also

Three frogs front detail, tinted

Other photos also show protruding digits suggesting
hidden limbs, such as this detail of C's left side with what's probably A's
left foot underneath.

Three frogs left side detail

One thing I find very strange is that there are no
pictures of the underside. The Sun photographs show someone was
perfectly capable of picking the frog{s) up, and it looks like deliberate
avoidance of a viewpoint that could disprove the six-legs description.

Other problems with three-headed frogs
If this were a three-headed
frog as photographed, it would require a completely unprecedented teratology. I
think the BBC experts would have difficulty justifying the combination of

1) Conjoined siblings are genetically the same
individual. There have never been any substantiated examples of non-identical
These frogs are non-identical; the head and arms A are much
lighter in colour than B and C; and the back of C appears a slightly different
colour to B. (The occasional cases of apparently conjoined non-identical
multiples, such as the kittens picture half-way down
, are generally considered to arise by their being stuck together after
birth by dried mucus, etc).
2) Although
have been described, the evidence mostly anecdotal. A
three-headed turtle
was reported from Taiwan in 1999, and there's another videoed on YouTube (here) but these appear to
be better described as a two-headed turtle - standard left-right bifurcation -
with an unclear structure - probably a stump of conjoined limb or shoulder bone
- between the heads. Two heads is as far as it goes; two-headed tadpoles have
been created in the laboratory (for instance, by exposure of embryos to lithium
or inducing overproduction of the wnt gene) and there's anecdotal
evidence of two-headed frogs observed in the wild. The US Geological Survey
Field Guide
to Malformations of Frogs and Toads
(PDF format) has no examples, but I've
been sent one current example of a two-headed toad (see below).
The angle of the alleged conjoining is wrong. Conjoined siblings are generally
joined - or branched - symmetrically about the body axis (the wnt gene
involved specifically causes left-right axial bifurcation). B and C might
conceivably be conjoined, but you don't get positioning like A, with the back
of one conjoined to the belly of the other.
4) If, as speculated, the
deformation was caused by pollution, it doesn't match known frog teratology
from this cause, which involves single individuals with problems such as
missing limbs, missing eyes and obviously abnormal extra limbs (the jury is
still out on the relative contributions of chemical pollution, infection by
, and maybe UV levels). See the website of the
Minnesota Pollution
Control Agency
for examples.
5) It seems vastly unlikely that
such a trio would manage the necessary feeding, locomotion and avoiding
predators to successfully grow from tadpole to adulthood.

Of related
interest: Kentaro Mori of the excellent Brazilian skeptics weblog
CetismoAberto kindly sent me
a reference to two-headed Surinam toad
for sale at a Tokyo rare aquatics shop for 498,750¥ (about $4600 /
£2500), and apparently found in the wild.

I have no
idea why this story has spread so dramatically, with the majority of news
sources copying it without critical or scientific analysis. The
Independent, as far as I can tell, was the only one to mention the
mating-frog possibility -
frog' leaves experts on the hop
. Perhaps the environmental angle - mutation
caused by pollution - is the emotional hook. But there's also something very
mediaeval about it: monstrous births presaging disaster. In this
, Russell Wangersky points out the interplay of factors that can
drive a story like this (in fact, the previously mentioned two-headed toad
one). My inclination was to think that the BBC deserves a slap on the wrist for
rushing into publication without more stringent checking and then, unlike the
MetroWest DailyNews, failing to report counter-evidence. But then again,
this is an unimportant regional 'curiosity' story where lack of highly detailed
checking is understandable. I e-mailed them straight away, criticising the
facts of their coverage, but so far they've neither posted a follow-up, amended
the story, nor replied to me. If you're a herpetologist and agree with my
interpretation, maybe you could offer the BBC a reasoned

It took about four years to get a reply.

Addendum: 14th April 2008

Approximately on the
4th anniversary of the story, I sent a further complaint to the BBC - and got a
reply. Discussion, reproduced with permission, follows:

Mon, 14 Apr 2008 15:11:10 +0100 / From BBC
Girvan, Thanks for your email: this is the first complaint about this story we
have received to the best of my knowledge. The journalist who wrote the piece
has left and is now in Australia. However, I have to go with the story as it
stands: the lady from the nursery is convinced and convincing and the
journalist ran it past an independent wildlife expert before publication. If
you have proof to the contrary, please let me know. Regards (name redacted) BBC

Fri, 18 Apr 2008 20:59:32 +0100 / From Ray
Dear (name redacted),

Thanks for your email: this is the first complaint
about this story we have received to the best of my knowledge.

Thanks also. In which case there has been something
severely wrong with the BBC complaints system then, as I've been trying to get
a reply via the BBC complaints system on and off for years. Yours is the first
response I've ever had.

However, I have to go with the story as it stands: the
lady from the nursery is convinced and convincing and the journalist ran it
past an independent wildlife expert before publication. If you have proof to
the contrary, please let me know.

Obviously "proof" either way is impossible now, but
analysis of likelihood is still possible. Have a read of my web page on the
matter: Some of the links are
unfortunately dead - I'll see if I can find them archived - but the thrust of
it is that this is a mistaken interpretation of common frog mating behaviour
called "multiple amplexus" (i.e. multiple males clinging tightly to the
female). There's a good video at Metacafe
( The problem, I
think, was that the story wasn't sufficiently checked (I appreciate that it was
an unimportant regional story that wouldn't have been of high enough priority
for checking with multiple experts). I can't explain why the wildlife expert
consulted didn't consider multiple amplexus as the obvious explanation, but as
to the lady from the nursery: this is not an unprecedented kind of mistake,
even with perfectly intellligent people. I've cited a couple of examples of lay
persons thinking mating anurans are a single two-headed individual. All I'm
asking is that you run this past some herpetologists - not just general
wildlife experts - but people who specifically know frog and toad

Suggestions: * The Herpetology Hotline (see;
* The British
Herpetological Society (
*Peter Stafford
( directory/botany/cv-9110.html)
who is editor of the Herpetological Bulletin See which they think is more
likely: three-headed frog, or multiple amplexus?

Sincerely, Ray

Mon, 21 Apr 2008 08:23:32 +0100 / From BBC

Thanks for the reply Ray. I'll take your advice on
board if this type of story crops up again. Rgds (Name

Mon, 21 Apr 2008 13:09:25 +0100 / From Ray Girvan

Thanks for the reply Ray. I'll take your advice on
board if this type of story crops up again.

That's nice - but are you going to do anything about the
story as it stands? (i.e. remove it, or at least get a herpetologist's opinion
for balance).

I needn't remind you of the BBC's editorial policy on
accuracy (
) - "The BBC's commitment to accuracy is a core editorial value and fundamental
to our reputation ... All the relevant facts and information should be weighed
to get at the truth ... checking and cross checking the facts".

doesn't square with leaving up a story whose accuracy is very questionable, and
ignoring the major relevant fact of a mundane explanation. Regards, Ray Girvan

Mon, 21 Apr 2008 14:11:56 +0100 / From BBC

I don't think I am going to alter the story no: we got
a wildlife expert's opinion at the time and it is balanced. Would you expect a
newspaper to alter all its old copies if/when new information comes to
Rgds (Name redacted)

Date: Mon, 21 Apr 2008 16:24:17 +0100 / From Ray

I don't think I am going to alter the story no: we got a
wildlife expert's opinion at the time and it is balanced.

Would you
expect a newspaper to alter all its old copies if/when new information comes to

a) The web is not paper, and such amendments are both possible
and routine for the BBC website. See the BBC's own The Editors blog ( : "Our
policy is to correct anything that´s wrong - spelling mistake, factual
error or anything else - as soon as we become aware of it" -Steve Herrmann,
Editor, BBC News website

b) Even papers do print retractions / revisits
to the topic if new evidence is available.

Regards, Ray Girvan

Wed, 23 Apr 2008 09:03:10 +0100 / From BBC

Hi Ray, Thanks for this.

As I said, I've taken
your comments on board for any future stories we write on this subject, but I
don't think I am going to change the piece.

If you want to take this
further, I suggest you go through the BBC complaints procedure:

Thanks (Name

And there the exchange stands. It's probably pointless to complain further at this stage, but it makes an interesting case study of how the BBC works in going against its own claimed guidelines - "All the relevant facts and information should be weighed
to get at the truth ... checking and cross checking the facts" - to cling to a biologically stupid story.

If you're a herpetologist and agree with me about the likely explanation, do contact the BBC. Maybe you can do better. , after reading this, I've convinced you that the BBC
story is garbage, please contact them. The story address is
and the complaints link is

To finish on a relevant, but lighter, note: from
Channel 4 Films, Frog Porn. This comic
short by Graeme Kennedy features a seething pondful of spawning frogs with a
soft porn backing sound track.

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Monday, 1 December 2008

Comments policy - a problem

Sorry, but I've had to bin a few comments lately.

Comments are a difficult issue. On the one hand, I think that an absence of mechanism for feedback and factual correction is one of the besetting and egregious features that distinguishes propaganda from open rational discourse (and purporting to have such a mechanism, but only publishing friendly comments, is even worse). Any number of alternative health magazines and forums are guilty of this (as indeed are mainstream newspapers). Therefore I have comments enabled.

On the other hand, I'm not letting that stance be misused to game the system: I'll reject posts containing personal insults, libel, copyright breaches and links to sites that breach copyright, comments used as vehicles for promotion or linkspam, etc.

If you have peer-reviewed evidence refuting what I've said, fine.  But I will bin comments that just say I'm wrong and link to sales/promotional sites.
- Ray