Identifying Great Crested Newts
The great crested newt is the largest newt found in the UK. The grest crested newt can reach a maximum adult overall length of up to about 170mm, although this does vary between populations. A mature female great crested newts length ranges from 90 – 170mm, typically reaching 110-130mm. Male great crested newts may mature at a length of only 85mm (normally more), and grow to an adult maximum of about 150mm, though more typically 110-120mm. Adult great crested newts are easily distinguished from the two other native newt species, the smooth and palmate newts, by size and colouring; these two smaller species reach a maximum of around 100mm. The skin of adult great crested newts is granular in appearance. It has a black or dark brown background colour with darker spots, that in male newts extend onto the crest. It has very fine white spots on the lower flanks.
The crest seen on the great crested newt decreases in size outside the breeding season. There is a white, silver or grey stripe running from the tail tip along the central, fleshy section of the tail that fades as it approaches the abdomen. Females great crested newts lack a crest and white tail stripe, but have a yellow-orange stripe running along the bottom edge of the tail. Both great crested newt sexes have a vivid orange or yellow belly with an irregular pattern of dark black spots or blotches. On land, the great crested newt appears virtually black, and in male great crested newts the crest shrinks back against the body. Males of all newts have a relatively more swollen vent.
The adult male smooth newt has a crest that is wavy rather than jagged, and it does not dip at the start of the top of the tail. his newt lacks obvious granules in the skin, and is generally lighter in overall coloration, often with roundish black spots. The belly of the smooth newt may be superficially similar in appearance to that of the great crested newt, but the dark markings tend to be more rounded and usually fewer in number in adults.
Male palmate newts on the other hand have a protruding filament at the tail tip, with a low ridge along the back rather than a crest. Female smooth newts and palmate newts are very similar in colour and pattern, usually with a beige or brown background colour, with lighter undersides.
Great Crested Newt Eggs
Great crested newt eggs have a jelly capsule around 4.5 – 6mm long, with a light yellowish centre, while smooth newts and palmate newts lay greyish-brown or dirty white coloured eggs, surrounded by a transparent jelly capsule that is about 3mm across. Great crested newt larvae can be distinguished from the other species by the presence of a filament at the tail tip and black blotches over the body, tail and crest. They can be very hard to tell apart when they are under 20mm in length. The smooth newt and palmate newt larvae are light beige or brown, sometimes with fine black speckling. Great crested newt larvae are considerably larger, reaching a length of 50 – 90mm before metamorphosis in comparison with 30 – 40mm for the smooth newt and palmate newt.
Great Crested Newt Juveniles
On leaving the water, great crested newt juveniles are similar in appearance to adults, apart from lacking the black spots/patterns that develop on the orange belly as they grow. The pattern becomes ‘fixed’ as great crested newt adults approach maximum size. Great crested newt Males start to develop the secondary sexual characteristics in their second or third season. This is marked by the appearance of the whitish tail stripe and the crest, and normally occurs when newts reach 90 – 120mm in total length. It is impossible to sex great crested newt juveniles externally, as the crest and tail stripe are not present.
Great Crested Newts On The Move
As the newt breeding season immediately follows winterdormancy, adult great crested newts mature the eggs andsperm they will need for the next year in the previous summerand autumn. Adult newts may feed from the start of thebreeding season in order to replenish reserves. Newts that havebred for at least one season may emerge from hibernation withtheir eggs and sperm ready for the new spring breeding season.Adult great crested newts normally begin moving from their winter land sites between February and April. The timing of this movement is governed by a number of factors, particularly temperature and rainfall. The first of the great crested newt emergence nights are normally wet or damp, with air temperatures above 4 – 5°C, following several days when the temperature has been just below this level. This makes it less likely that newts will be stimulated to emerge too early by a single unseasonably warm winter’s day, then the great crested newts find themselves above ground or in the water when freezing conditions return. Great crested newt movement over land almost always happens at night.
The migration of great crested newt populations to breeding ponds is normally phased, with some adults not reaching the pond until May. The earliest great crested newt arrivals tend to be male newts. Migration dates are often later to the north and east of Britain, as they are for frogs and other amphibians. There is considerable variation between individual great cresred newts in the amount of time spent in breeding ponds. Having entered in early spring, adult newts may spend anything from one day to seven months or more in a pond. Great crested newts may also repeatedly move in and out of the breeding pond, as well as between ponds, over the spring and summer.
The main period when breeding adult great crested newts generally leave the pond is between late May and July. This movement occurs gradually, with most newts having left by August. A proportion great crested newts however may stay on until October and even, in some ponds, over winter amongst pond sediment and debris. Emigration from the pond usually coincides with periods of rainfall, and there is evidence that newts may leave a pond at or around the same point they entered it, indicating that they return to favoured parts of the terrestrial habitat that they somehow recognise. After leaving the pond, newts generally seek underground crevices or concealed above ground refuges.
Great Crested Newt Habitats
Great crested newts need both aquatic and terrestrial habitat. Great Crested Newts prefer small to medium sized breeding ponds, around 50-250 square metres, with smaller ponds being used more successfully where they occur in groups. Very small ponds and larger lakes are usually not used by newts. Great crested newt breeding ponds should support aquatic vegetation for egglaying. It appears that great crested newts prefer extensively vegetated ponds with a submerged plant cover of about two thirds of the pond and emergent/floating vegetation cover of one quarter to one half of a pond; in other words a well established, mid-succession pond is perfect for great crested newt habitat. Ideally there should be open, less vegetated areas within the pond to allow adult male newts to display in clear view of females. Ponds that lack shade on the southern margin seem to be preferred by newts.