Masked Marvel's picture

Identifying juvenile Lissotriton newts

There have been a lot of juvenile Lissotriton (smooth or palmate) newts posted on iSpot which have only been identified to genus level. It is possible to identify these to species level based on the orange line which may or may not be present on their back.

For palmate newts L.helveticus the stripe is present and continues along the back onto the tail such as these ones:
http://www.ispot.org.uk/node/172670
http://www.ispot.org.uk/node/80841

On smooth newts L.vulgaris the orange stripe (if present at all) appears behind the head and peters out close to the forelimbs such as on these ones:
http://www.ispot.org.uk/node/80712
http://www.ispot.org.uk/node/143278

I had been aware of this distinction for some time but couldn't remember the source so have done a bit of checking back through my books and found:

From Newts and Salamanders of Europe, by Richard Griffiths (1996): "Immature newts may be identified as palmate newts by a light-coloured dorsal stripe which runs down the neck, down the back and on to the tail. This is yellow-orange in colour and of equal intensity along its length."

The same book says that smooth newts "...may be distinguished from the closely related palmate newt by the dorsal stripe. In many animals this yellow stripe is most intense where it starts on the head, and then fades gradually along the back and does not reach the tail."

This is described in this paper: Roberts & Griffiths, 1992. The dorsal stripe in newt efts: a method for distinguishing Triturus vulgaris and T.helveticus. Amphibia-Reptilia 13: 13-19, which gives greater detail than the book.

I have tried to amend all the juvenile "Lissotriton sp." observations that weren't already identified to species level.

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the naturalist man's picture

Juvenile newts

Thanks for this Liam.

Graham Banwell

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Martin Harvey's picture

Thanks

Great to have this information available, thanks.

----
Entomologist and biological recorder

Masked Marvel's picture

Hope it's useful to the iSpot community

Unfortunately since I posted this someone has added an agreement to "Lissotriton sp." on the four examples I posted so maybe they don't agree!

wolvobirder's picture

Looks easy enough

Thanks for this useful information. I just found a young newt in my garden today and wondered what species it was. It turns out it was a Palmate newt. Hopefully others will cotton-on to this post in due time.

If people have valid objections to this method of ID then so be it, we will have to revert to "Lissotriton sp." but it looks easy enough to differentiate them from the description you gave. The only thing I can think of is if there is any variability and overlap in the length of the orange stripe between the species which may cause confusion.

John Griffiths

Masked Marvel's picture

Should work nearly every time

Hello John
No there is no overlap, as if the stripe reaches the tail it is a palmate newt. In the original paper they tested it on "inexperienced" and "expert" observers and the inexperienced people were able to distinguish the two correctly 100% of the time. The experts (authors of the paper) had one (of the same newts) they weren't sure about, so the inexperienced observers actually got the newt right and beat them!

Cheers
Liam

wolvobirder's picture

If I have read that right

If I have read that right then the question has to be asked, why weren't the authors sure on the ID?

John

Masked Marvel's picture

I think they were just being

I think they were maybe being overcautious as scientists often can be and assigned it as unidentified. They do report that a very small percentage display intermediate characteristics but overall this method is "highly reliable".

wolvobirder's picture

Overlap

So in other words there is some degree of overlap or uncertainty. I guess we would need to know where the uncertainty lies so that you know if you are looking at a specimen that can be identified, or one that is intermediate between the two. Scientists are cautious for a reason.

Even if this only works 80% of the time it would be good, with the other 20% being left as Lissotriton sp.

Certainly room for further study, unless it states all this in the paper you mention. Even so the basis behind scientific principle is that any study or experiment should be repeatable.

John Griffiths.

Syrphus's picture

Interesting, but I would want

Interesting, but I would want a lot more convincing - not least by the NARRS etc. folk coming out in favour.

Two things in your statement jump out - 'if the stripe reaches the tail it is a palmate newt' does not mean that 'if the stripe DOES NOT reach the tail it is a smooth newt'.

And if the experts could not agree (the opinion of the others is irrelevant), the distinction does not work 100% of the time. Sample size would be useful to know before we can assess the trial.

M.

TRY

recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.

Masked Marvel's picture

If the stripe reached the

If the stripe reached the tail it is 100% a palmate newt. If it stops around the forelimbs as on the examples I posted it is 100% a smooth newt. The slight uncertainty occurs when the stripe reaches further down the back or looks like it may fade around the pelvic girdle which is rare. Any field characteristic will not be 100% reliable and I would think this is as reliable as the spotted chin in the female newts as I have seen a number of smooth newts with unspotted chins and palmate newts with spotted chins are occasionally reported.

In the paper, 67 efts of known species were assessed and there were statistically significant differences between the two species in all of the stripe characteristics they looked at (starting position, end, position, colour and uniformity). This was then field-trialled with 67 wild efts. The experienced observers were able to distinguish 100% of smooth newts and 98% of palmate newts. One was unknown. That would seem highly reliable to me.

In addition to the book mentioned above, the method is also detailed within the 2000 New Naturalist Reptiles and Amphibians book, which is considered the definitive guide to the reptiles and amphibians of Britain.

The reason NARRS don't use this is because it's not relevant to their survey protocol which is a pond survey of breeding adults. This characteristic only applies to terrestrial juveniles which wouldn't be found during a NARRS survey. One of the authors of this paper is one of the most respected academic herpetologists in the country whose research team have designed the NARRS survey protocols with input from many experienced herpetologists from across the country (including myself).

Cheers
Liam

wolvobirder's picture

Thank you

Thank you Liam,

This is exactly the kind of answer I was hoping for and should put the matter to bed.

John

b.trippier@yahoo.com's picture

newt identification

I have been observing newts for a university project studying their phenology. I was wondering if you could see whether these are smooth or palmate, they are still in the aquatic stages although now many have left for hibernation. I think they are smooth newts however i havnt been able to see any orange stripe on any specimens however i shall look more closely next sampling.

http://www.ispot.org.uk/node/294237?nav=users_observations

Masked Marvel's picture

Comparison

See here for a direct comparison between the two.

http://www.ispot.org.uk/node/297041