Ichthyosaura alpestris – alpine newt and the mystery of the orange belly

Berg Molch 1I spent a busy day relocating these beautiful little guys to a new home. Alpine newts inhabit all types of bodies of water, from garden pond to large lake. They can reach the ripe old age of 12 years, and adult males measure in at up to 12 cm. They are relatively common compared to other amphibians in our area (Basel) apparently, so though they are protected, they are not currently at risk of extinction. That said amphibians may not be moved from their natural habitat, caught, bought or sold, or interfered with in any way. The only reason I moved these is because we were draining the pool and I had no choice, and of course, knowing what I do now they needed to get out of the water.

Alpine newts live terrestrially for a large part of the year inhabiting shady, damp areas in all kinds of undergrowth,often in wooded areas,  however after coming out of hibernation the newts migrate to their spawning ponds for mating and spawning. During the mating season (April/May) the males sport beautiful mating  colours with bright orange bellies and dark-blue speckled backs and a yellow/black speckled stripe (see pic above). The females  remain a mottled and inconspicuous brown throughout the year. At the end of the mating season as the newts move back to living on the land the males change colour to mottled brown.

The newt on my picture was taken from a swimming pool that has been unused for around 4 years and has in the passage of time developed a rich wildlife population. The newts have been living in there undisturbed since they jumped in. Not knowing that they need to get out we never thought to help them out, they must have hibernated at the bottom of the pool. Strange, as they have lungs this doesn’t seem feasible. Hm. Or did they all die and this years lot are the ones that jumped in in March and got stuck? Maybe more likely.

Anyway, It being a pool the only way out without human intervention was up until I intervened in the claws of a raven, or the beak of a visiting heron, and that of course would have been a terminal exit.

The specimen above, a male, still sports his mating colours, although it’s July and the mating season is long gone. As said after the mating season newts move to land living and change colour to mottled and inconspicuous brown. So if timing were everything all the specimens I rescued should have been brown, however, I collected around 15 animals from the water and they were all males sporting full mating colours. Did I miss the ladies I wonder, or were they not foolhardy enough to jump into the pool?

Anyway,  I started wondering why my newts are still in their party outfit  when they should be getting ready to live on the land. My theory is that the colour change is triggered by the change of temperature (newts are cold-blooded) as the newts move from water to land, maybe most likely in combination with other signals (UV light, number of hours of daily sunlight), if only temperature played a role the newts would switch to mating colurs in the winter which would make no sense.   Unfortunately, I haven’t as yet found a paper on this phenomenon, although I am convinced herds of PhD students have studied this and there must be loads of scientific data out there.

So I currently have more questions than answers, any input from expert sources is very welcome!

Sources used to compile the above: Pro Natura CH, Wikepedia, Pro Natura Aargau, Newts marine biology.uk, Bundesamt für Umwelt, Verkehr, Energie und Kommunikation


4 thoughts on “Ichthyosaura alpestris – alpine newt and the mystery of the orange belly

  1. I was impressed too, and actually they’re not even that slithery, they move on cute little feet :). Moved another frog and 3 newts, with black backs and orange bellies this time

  2. Great theory, in my opinion everything you can’t explain in biology is probably about thermoregulation :-), do the white/black patterns have a thermoregulating function too? Does it fascilitate body liquid fluid transport due to temperature differences?

    • hi Arno – of course with a website titled the world of warmth – you would have to think that :). I would have thought patterns mainly camouflage – lighter from below because when swimming on top of water they are less obvious against the sky? Dark on top, same reason but inverse? Fluid transport, well they have heart and lungs so a nicely sorted out pumping system – so doubt liquid transport is impacted – also would be a very fiddly transport wouldn’t it?

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