Monday 28 April 2008

Dancing with newts


I often make a visit to the forest’s drinking pools during early spring. These small ponds, uncovered and man-made, draw down siskins, crossbills and other birds during dry periods. One particular pool is home to a breeding population of smooth newts. This is our most widespread and abundant newt and it is the one that you are most likely to encounter within Norfolk. The closely related palmate newt prefers more acidic ponds and is only known from two sites within the county.

Over the years I have spent a bit of time watching smooth newts, both in the field and by housing them temporarily in a tank, observing their behaviour and their fascinating courtship dance. Smooth newts have a terrestrial phase, which extends from mid-summer in the adult newts through to February or March the following year. During the first warmer days of spring the adults emerge from their overwintering sites and return to the breeding ponds.

Male smooth newts first attract the interest of a prospective mate by blocking her way. If the female is receptive she will turn to face the male, stimulating him to initiate a long and rather frenetic courtship display. There are three components to this display, the first of which is the quiver. This sees the male face the female before vibrating his tail rapidly against his own body. The second, known as the wave, involves the male turning side on to show off his breeding colours and crest to best effect. The final component is a violent tail movement known as the whip. All three actions can be seen in a typical courtship, although the female may break off the engagement at any point should she determine that the male is unsuitable. A receptive female will follow the male as he moves away still displaying, before touching his tail. This intimate contact causes the male to release a package of sperm, known as a spermatophore, which the female then collects as she passes over it. Males usually outnumber females in the breeding ponds and competition for a mate can be fierce, with some males resorting to underhand tactics in order to secure a mating. These males watch the courtship displays going on around them and then cut in at the appropriate moment. They do this by touching the other male’s tail, causing him to release his package of sperm, before leading the female away elsewhere with their own dance.

The presence of immature newts in the drinking pool shows that breeding took place successfully last year. With their external gills these individuals have yet to undergo metamorphosis, a sign that they were hatched late last summer. Here’s to a good season this year.

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