The palmate newt is the smallest species found in Britain, rarely exceeding 8 cm although many individuals never reach this size, and males are significantly smaller than females.
Whilst palmate newts appear superficially very similar to smooth newts, having the same olivacious ground colour, with practise they can be differentiated. Easiest to identify are the males during the breeding season. In stark contrast to the showy crest of the smooth newt, that of the palmate is little more than a slightly raised ridge along the mid-line of the back, which, in common with other breeding season adornments, is lost outside the season. However, there are also two discernable dorso-lateral ridges, one down either side of the back, giving the animal a rather square cross-section, quite unlike the smooth newt. The back feet are particularly conspicuous during breeding as the dark webbing between the toes becomes heavily developed, giving rise to the name palmate. Additionally, a characteristic short, fine filament grows from the tip of the tail.
Females of the two species may be trickier to tell apart and differences between the two are described in the account of the smooth newt. However, to reiterate, the throat patterns differ between the two species. That of the smooth newt is white and usually finely spotted, while that of the palmate newt appears translucent, or pink, and lacks any markings. Additionally the palmate newt has a distinctive white or pale vertical bar on the trunk, immediately above the back legs, which is absent in the smooth newt, together with two small white tubercles or nodules on the underside of the back feet, which in the smooth newt are brown.
Larvae of palmate and smooth newts are indistinguishable. However, once metamorphosis occurs the juveniles can be differentiated by a yellow or orange dorsal stripe, which in palmate newts runs from behind the head along the length of the body and tail. In smooth newts, if it is present at all, it fades before it reaches the tail.
Somerset has a small claim to fame regarding palmate newts. Although the species was first described in 1789 by Grigory Razumowsky, from specimens captured in Switzerland, they were never recognised in Britain until 1843 when William Baker captured four of them in a pond on Clay Hill Farm at Cannington. Noticing that they differed from other known native species, he passed them on to Thomas Bell, an authority on the subject at the time, who identified them as palmate newts and published news of their discovery, confirming them as a further native British species. Subsequently they were found to be widespread across much of the country.
Where conditions within a pond suit all the three species of newts, then all three species will happily co-exist. However, often the conditions within a pond will exclude one or more species as their requirements are not identical.
The palmate newt appears to be the species most tolerant of acid conditions and low temperatures, and they are the species most likely to be encountered in ponds on high acid moorland such as those found on Exmoor and the Quantocks, as well as ponds within acid environments such as conifer plantations. However they are equally at home in lowland ponds at a wide range of pH values. Curiously, Beebee and Griffiths found no difference in the survival of eggs from either palmate newts or smooth newts at low pH, and suggest that the palmate newt’s tolerance of soft, acidic waters may be influenced more by the secondary effects of a low pH environment, such as invertebrate abundance, than by the acidity per se. Either way, this aspect of their ecology greatly influences their distribution.
They have minimal space requirements and do not appear to show much fidelity to a particular breeding pond. Consequently, while they are perfectly happy in large pools or ditches, they can also be found breeding in the smallest of ponds and it is not unusual to find them occupying temporary water bodies such as the flooded ruts left by a tractor.
The annual cycle of all three species is similar with hibernation occurring during the winter months. However, being the most cold-tolerant some palmate newts seem barely to hibernate at all, particularly in lowland Somerset, and small numbers may be seen active in ponds throughout the winter even during cold periods when they sometimes continue moving about under the ice.
Palmate newts are common and widespread across Somerset and the unitary authorities and much of the information already presented on the distribution of the smooth newt is also relevant to the palmate newt.
While both species are found to co-exist across most of the county, palmate newts are usually the more abundant at altitude, while smooth newts are often the more abundant in the lowlands. Nowhere in the county is this more apparent than on Exmoor, where the palmate newt is abundant while the smooth newt is rare and in some parts, probably absent. The trend is also apparent on the Mendips, where both species can be found, but palmates are the more plentiful. Conversely, on the low-lying levels and moors palmate newts are scarce, and in some areas probably absent, while smooth newts are plentiful.
This does not imply either that palmate newts are upland specialists, or that smooth newts are lowland specialists, as their distributions can overlap at all altitudes. Instead it simply implies varying tolerance to different environmental conditions. The site where Baker discovered the first palmate newt in Britain was a lowland site near Cannington, and Burton mentions palmate newts present in brackish ditches near the sea.
In the unitary authorities, Mary Wood describes palmate records as particularly concentrated around the Bristol area, with just a scattering of records elsewhere, whilst Charbonniere found them plentiful in ditches and ponds at Keynsham.
Beyond Somerset, the palmate newt has a smaller distribution than the other two British species. Within Britain it is found in England, Scotland and Wales, although it has a patchy distribution and is absent or rare in East Anglia and the East Midlands. It is also absent from Ireland. On the continent it is confined to Western Europe, from the north of the Iberian Peninsula, through France and northern Germany eastward as far as the western Czech Republic.