2017 - Lizard Survey

Natterjack Toad

Bufo calamita

The natterjack toad is confined to a handful of locations in Ireland; specifically Kerry and the Raven Nature Reserve in Wexford. They are nocturnal, hunting and mating at night and sleeping during the day. Toads are amphibians: they

live on both land and in water, returning to water to reproduce. Frogs are also amphibians. The difference between a toad and a frog is not taken too seriously by zoologists: frogs have wet skin, toads have dry skin.

Habitat & Ecology
Natterjacks need shallow clear ponds in sandy soils. The ponds should exist all year round so that the fertilized eggs or emerging tadpoles do not dry out. Ponds that dry out in exceptionally dry summers may be more suitable as these ponds cannot support dense vegetation. The balance here is delicate; possibly one drying out every 2 or 3 years will allow a population to maintain itself while keeping the surrounding vegetation under control. This is an example of the delicate balance between climate and the survival of a habitat suitable for a particular species. The edges of the ponds much have a slight grassy slope for easy exit and return to the water (saucer-like). Dense vegetation in or around the pond is not ideal as it plays host to predators such as carnivorous insects or their larvae (dragonflies and beetles). The pond edges and surrounding areas should have large rocks or logs to allow the natterjack to hide during the day.

Normal life span is 6 or 7 years, but they may live as long as 12 years. Their natural predators as adults are foxes, herons and otters. The natterjack's diet consists mainly of insects, particularly moths (they are carnivores in adult life and herbivores as tadpoles). They also eat spiders, snails, worms and woodlice. Despite their restricted distribution in Ireland, they are great travelers, moving up to 1 km at night (they don't hop like frogs, unless suddenly disturbed ) in search of food or mates or new habitats. They move with the gait of a lizard and their markings can be seen in sand.
Natterjacks are not great swimmers and may drown in deep pools if they cannot reach shore quickly. Ideally the pools are less that 15m in diameter.

Reproduction
They look for a mate soon after emerging from hibernation in March. The mating call is very loud (rrrrRup, rrrrRup). This is possibly due to the small numbers that inhabit any single pond; they need to be sure that any nearby female hears them. They mate from late April to July. Fertilization is external. This means that the female lays unfertilized eggs directly into the water and the male covers them immediately with sperm. Fertilization occurs in the water. The fertilized black eggs form a long double stranded bead-like string about 1.5m long. After a few days they form a single strand. The eggs hatch after five to eight days and develop into tadpoles. This tadpole stage lasts for about 38 days (just over 5 weeks), during which time they feed on vegetation. They then lose the tail and start eating meat and metamorphose into the adult toad form. Both the eggs and the tadpoles contain a noxious chemical that makes them unappetising to many animals, although the larvae of dragonflies and beetles are not affected by this.

The young adult may be only 10mm in length but can grow to a full size of 80mm. Despite the variation in body colour, the distinctive yellow strip is always present.

© Paul Whelan, 2007

Natterjack Toad