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Endangered natterjack toads in bumper spawn printable version

27 Jun 2014: posted by the editor - Environment, Ireland

Although categorised as 'endangered' in the recent All-Ireland Red List and their conservation status assessed as 'unfavourable' in Ireland's recent national report to the European Commission, things may finally be looking up for the natterjack toad after a bumper year in County Kerry.

Over the last week, staff of the National Parks & Wildlife Service of the Department of Arts, Heritage & the Gaeltacht have recorded a huge abundance of young toadlets emerging from breeding sites in the Iveragh and Dingle peninsulas, giving hope for a change in fortune for the protected species.

When the toads were first noticed in Kerry in 1805, it quickly became clear that they were widely distributed around Castlemaine Harbour from Inch in the north to Rosbeigh in the south. Much later they were also discovered to be breeding at Castlegregory on the north side of the Dingle peninsula. But the first half of the 20th century saw a significant programme of land drainage and reclamation around Castlemaine harbour. Many coastal wetlands, where the toad bred, were lost. By the 1980s, toads were restricted to the Castlegregory area and about 10 isolated locations around Castlemaine.

This year saw a very wet May in Kerry, which provided plenty of water for the toads to breed in. This was followed by a warm start to June which warmed up the ponds and allowed the toad tadpoles to develop and emerge quickly before the ponds dried up.

"Toads are naturally a boom or bust species" explained Dr Ferdia Marnell of the Department's Scientific Unit. "They only need a good year every four or five years to keep a breeding population going. In good years, when everything goes right, thousands of young toads can emerge onto land. 2014 has been the best year I ever remember, and I've been studying them for nearly 20 years."

Once out of the ponds these young toads will spend two to three years on land feeding on small insects, snails and spiders until they are ready to breed themselves . During this period on land the young animals also disperse. This dispersal provides for genetic exchange with adjacent ponds and allows new ponds to be colonised. The problem for the toad has been that there were no new ponds to disperse into and so populations became isolated and prone to extinction.

In 2008 NPWS initiated a scheme to pay farmers to dig and manage ponds for toads. To date 96 new ponds have been dug within the natterjack toad's range in Kerry. The initial signs are encouraging with 20 of these ponds already colonised naturally by toads and many of them producing good numbers of toadlets this year.

The Minister for Arts, Heritage and the Gaeltacht, Jimmy Deenihan, T.D., welcomed the news, saying: "We are legally obliged to bring the natterjack into favourable conservation status, so I am delighted to hear that the toads are doing so well this year. The local farmers have played an important role in providing and managing habitat for this rare animal and it is rewarding to see that effort paying dividends."

The natterjack toad is one of only three amphibians found in Ireland - the other two are the common frog and the smooth newt.

Adult toads may grow to 80mm and although colour varies from pale green to black above there is always a yellow stripe down the middle of the back. Natterjacks are nocturnal and during the day they hide under logs and stones. Over winter, natterjacks hibernate in burrows that they dig themselves in sandy soils, or in piles of rocks or dry-stone walls. It is normally mid-April before the natterjacks become active and the distinctive croaking of the male is heard at the breeding ponds.

Unlike frogs, toad spawn is laid as a long string of eggs. It can be 1.5m long and it may contain 2-3,000 eggs. The egg-string is wound around the aquatic vegetation in the shallows of the breeding pond. The black embryos look like beads in a necklace.

In warm weather, natterjack spawn hatches within a week and the tadpoles develop and metamorphose within two months. In good years, huge numbers of juveniles may emerge successfully. However, in dry years, water levels can drop rapidly resulting in mass mortality of the tadpoles.

Natterjack's eggs and tadpoles contain a noxious chemical that largely protects them from predation, but dragonfly and beetle larvae will eat them. Foxes, otters and herons occasionally eat adults, but if they escape predation, natterjacks can live to six or seven years in the wild.

The natural range of the natterjack toad in Ireland is confined to a small number of coastal sites on the Dingle and Iveragh peninsulas in Co. Kerry. But it was once more widespread in Kerry. There is evidence that by 1970, the range of the natterjack toad in Ireland has decreased by about half. The most significant loss in range occurred around Castlemaine Harbour. It seems clear from historic records that the species has previously been found right around this coastal strip.

Since 2008, 48 farmers have joined a scheme to help restore the toad to its former range, with each farmer digging and managing two ponds. 96 new ponds have been dug for natterjacks within their former range. 20 of these have already been colonised naturally by toads. The farmers are paid €1,000 each year to manage the ponds and the surrounding land for natterjacks.

Tags: natterjack toad

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