By Ann Haigh
SIGHTINGS of frogspawn have started to be reported all over West Cork.
The frogs are certainly reading the textbooks as frogspawn typically starts to appear in late January, February and March. The frog’s life-cycle is a well-studied example of an animal life-cycle in our school system, as I am sure you will remember. Multitudes of eggs, frogspawn, are laid in ponds and watercourses across the country at this time of year. If the spawn is not eaten by predators such as birds, fish and newts; tadpoles start to appear in the egg masses within 1-4 weeks, depending on the temperature. It takes approximately 14 weeks for the tadpoles to transform into adult frogs via the process of metamorphosis.
Even though masses of spawn are laid, only 1-2% of eggs will make it to adult frogs Despite our early education on the frog’s life-cycle there’s always plenty more to learn because amphibians, which include frogs, toads and newts are a truly fascinating group.
Frog or a toad?
A frequently asked question is ‘did I spot a frog or a toad’? If you’re in West Cork, the answer is almost certainly a frog. The only species of frog found in Ireland is the common frog (Rana temporaria) and it is present throughout the country. We do have one native species of toad, the natterjack toad (Epidalea calamita), but this is a rare and endangered species that is restricted to specific coastal locations in Kerry, its natural range and in Wexford, where it has been introduced. As for the common toad (Bufo bufo) this is not native to Ireland and sightings in the wild have been sporadic, mainly confined to Dublin and Donegal, where the origin is thought to be from escaped captive toads.
Common frogs can vary enormously in colour and pattern, ranging from light yellow-brown or red to almost black, with brown and black marks on their back and a characteristic dark patch behind each eye. Fascinatingly, they are also able to change their skin colour to match their surroundings. They can take on new camouflage in a matter of hours. This variability and diversity in colour form often leads people to falsely think they may have found a toad.
Mating is a risky business
Amphibians, by definition, can survive on water or land. Despite being associated with water, frogs can live quite well on land for much of the year. During winter they reduce their metabolism and may lie dormant under compost heaps, piles of stone or wood and damp vegetation. However, every spring frogs must return to freshwater, usually to where they were born, to mate and spawn. Some male frogs may over-winter in the mud at the bottom of ponds. They can breathe through their skin as well as via their lungs so this enables them to survive as they extract oxygen from the water.
The males arrive at the breeding ponds first, and croak in chorus to attract females.
The male frog that has spent the winter at the bottom of the pond has the advantage of being already there! Once the females arrive, mating occurs and as the female lays her spawn in shallow water, the male fertilises the eggs by spraying them with sperm.
Mating and spawning are a risky time for frogs, last spring we discovered the remains of many dead frogs on the Marsh in Skibbereen. When reported and investigated, the feedback from the Herpetological Society of Ireland (HSI) was that this wasn’t unusual. Mortality at spawning time is naturally high. Males can inadvertently crush and drown exhausted females as they mate. The male frog holds the female in a tight grip, known as amplexus. Additionally, predators such as herons, rooks, otters and foxes can take advantage of the frog’s vulnerability at mating time. Depending on the location of the water body, frogs may also fall victim to traffic as they cross roads en masse to travel to and from their breeding area.
If they survive mating and spawning, adult frogs, which can live an average of 5-10 years, spend the rest of the spring and summer feeding. We typically imagine that a frog’s diet consists of flying insects, as we can all recall that lightning quick flick of their tongue which snatches prey from the air. However, frogs also enjoy other invertebrates such as snails and slugs, making them a gardener’s friend.
Natterjack toad
As mentioned, the natterjack toad is endangered and has a very limited distribution.
Notably, last summer, captive-bred natterjack toads were released into the wild for the first time at Castlegregory, Co Kerry as part of a joint conservation project run by the National Parks and Wildlife Service (NPWS) and Fota Wildlife Park. The NPWS, Fota and the Dingle Aquarium have released up to 6,000 toadlets to date, taking spawn from the wild and rearing the toadlets.
However, last year was the first time that toads were bred in captivity at Fota and their off-spring released. Hopefully this conservation project will be able to secure a future for the natterjack toad.
Just three amphibians
In Ireland we only have three native species of amphibian, the common frog, the natterjack toad and the smooth newt. With just three species it shouldn’t be hard to identify them, but as mentioned, sometimes frogs are confused with toads, and our smooth newt is often confused with our only native land reptile, the common lizard. Newts are much more likely to be found in waterways and ponds, and do not bask in the sun like lizards. If you can get a close enough look, lizards have five toes on each front foot but newts only have four.
Conservation and protection
Threats to frogs, toads and newts include habitat loss due to land drainage and land use changes, such as the clearance of hedges and scrub, and pollution. Amphibians have thin skin and are particularly vulnerable to pollutants such as heavy metals, fertilisers, herbicides and pesticides.
Notably, the common frog is listed as an internationally important species and is protected under the Habitats Directive (92/43/EEC) and the Irish Wildlife Act (1976, amended 2000).
It is an offence to take frogspawn from the wild, but a special license can be granted to teachers for the purpose of education.
It is also not advisable to move frogspawn from one area to another, due to the potential to move disease with it. If you have created a pond, unfortunately you need to be patient and wait for the frogs to find it.
Do keep an eye out for frogspawn and tadpoles over the next few weeks. It can be a cheering sight, signifying new life and the approach of spring.
If you spot some you can also do your bit for conservation science by recording the date and location of your finding on the National Biodiversity Data Centre’s website. Happy frogspawn spotting!
• Ann Haigh MVB MSc MRCVS is a Skibbereen resident, a mum-of-two and a veterinarian with a masters in wildlife health and conservation and she is passionate about biodiversity and
nature.
