While superficially similar to the common frog, the common toad is actually quite different, both in appearance and in behaviour.
The toad is a thick set, stocky creature. The back legs are shorter than those of a frog, better equipped for walking than hopping, and the toes of the back feet are not as strongly webbed as are those of the frog. The skin is dry and rough, covered in warty protuberances, many of which contain skin glands.
Toads are generally an earthy brown colour, either uniform or with overlying darker or paler markings. Some individuals may vary slightly, appearing some shades of dull green, red or yellowish, but the colours are always rather subdued and never vibrant. In common with other amphibians the hues may change with temperature or mood, and become enhanced during the breeding season when some individuals appear olive green, yellow or brick red, but they return to rather drab browns once the breeding season is over. When disturbed in their underground retreats they appear almost entirely black.
Sexes can often be differentiated simply by their size, males being smaller than females. The average length from fifty adult males measured on the Mendips was 57.5mm with a maximum of 69.4mm, while that of a comparable series of females was an average of 68.9mm with a maximum of 84mm. Males can also be differentiated from the females during the breeding season, by the appearance of ‘nuptial pads’, rough, black callouses, on the thumb and two inner fingers, together with a temporary thickening of the front legs, all designed to assist with gripping the female in amplexus.
Toads usually begin to emerge from hibernation during mid to late February. However the emergence differs from that of frogs as it involves a conspicuous synchronised migration from the hibernation sites to the breeding ponds, which may be undertaken simultaneously by many hundreds of individuals.
The migration routes will be well trodden as the species has a powerful fidelity for specific breeding ponds, some of which will have been used every spring for many generations. They have a preference for large, deep ponds or lakes and it is unusual to find them breeding in ponds with a surface area much smaller than about 200m2. Their toxicity protects both adults and tadpoles from predation by fish, which find them distasteful; therefore fishing lakes are often used as breeding sites by toads.
Toads are essentially nocturnal creatures, so migration occurs after dark on relatively mild, wet nights with the first couple of hours after dusk seemingly the busiest. Males emerge earliest in the season followed by the females and, depending on the weather conditions, the migration may continue throughout March and well into April. However, toads will not migrate every night throughout this period, instead there are usually just a handful of nights when conditions are suitable and large numbers of toads are on the move. If conditions become either too cold or too dry, migration will be interrupted, sometimes for prolonged periods, during which those toads that have not already arrived at the breeding ponds will remain in the ground. Often the earliest arrivals at the breeding pond will have spawned and left by the time the latest arrive.
The distances from hibernation sites to the breeding pond may be substantial: Deryk Frazer mentions one individual that was followed for 2.5 miles (4.0km) along its migration route, while others routinely covered 0.75 – 1.25 miles (1.2 – 2.0 km).
Routes between hibernation sites and breeding ponds are followed instinctively and where roads have been constructed across these routes, toads will simply attempt to cross them. Many thousands get crushed on the roads during every spring migration, which in some areas has led to the development of volunteer ‘toad patrols’.
The concept of a toad patrol is very simple. As the toads arrive at the roadside, they are collected and safely lifted to the other side. However, such a simple description masks the extraordinary commitment shown by toad patrollers. A toad’s idea of good weather does not accord with ours and it takes a hardy sort of person to leave the home and get out patrolling on a dark, wet night in February. Additionally, it is time consuming, as the migration may last for several weeks. Yet, it is a remarkably rewarding activity that produces instant and tangible benefits for the welfare of toads.
In 2016 there were seven toad-crossing sites patrolled in Somerset together with a further eight in the unitary authorities, which between them have undoubtedly rescued many thousands of toads, ensuring they reach their breeding ponds safely. Despite such efforts toads are believed to have been in decline for many years, one estimate suggesting that nationally there has been a 68% decline in the last 30 years.
As toads arrive at the breeding pond, so spawning begins; often involving large numbers of individuals amid frenzied levels of activity, making it a dramatic spectacle for the observer. Inevitably there is a preponderance of males in a toad population so competition is intense and many females arrive at the pond with males already in amplexus, having encountered them during the over-land migration. Amplexus disputes occur among the males with many clasping a single female each trying to dislodge their competitors in a contest of strength, a process that often results in the drowning of the hapless female.
When they are ready, the females begin to produce their eggs. Unlike the clumps of spawn produced by frogs, toad spawn is laid enclosed in a pair of long gelatinous strings, one string from each oviduct which, as they pass over the attendant male’s feet, stimulate him to ejaculate his sperm, fertilising the eggs externally. The strings of spawn are wrapped around water plants, twigs and other debris on the bottom of the pond making them rather difficult to spot. Once spawning is complete the females will leave the pond, to be followed shortly by the males, once they are convinced no further females will be arriving.
The period during which toads are aquatic is short. Once breeding is completed the toads become terrestrial and solitary. Moving sometimes in excess of a kilometre from the breeding pond, they find a hole or crevice which is adopted as a daytime retreat and from which they emerge on warm damp nights to feed, returning to the hole before daybreak. The diet essentially consists of any prey that wanders within lunging distance of the toad and that it is capable of swallowing. Invertebrates such as beetles, spiders, slugs and earthworms predominate, although they have been seen to prey on juvenile mice and voles, young reptiles and metamorphic amphibians including small toads!
Once the adults have left the breeding ponds, the spawn begins to develop, following a similar process to that described for frogs. The incubation period is temperature dependant, but after about two weeks the newly hatched tadpoles can be seen hanging from the deteriorating jelly for a few days before becoming free-swimming. Tadpoles of frogs and toads can be easily distinguished, those of the toad being entirely black with a rounded tip to the tail, while the frog tadpole is paler, patterned with gold flecks and has a pointed tail tip. Unlike frog tadpoles, toad tadpoles will often assemble into large shoals in the warmer areas of the pond.
Unlike frogs, the rate of development across a cohort of toad tadpoles is quite uniform, resulting in a synchronised emergence of metamorphs during late June or early July, during which time the grass around a toad breeding pond may be alive with hundreds of toadlets, each about 10 – 12mm long. Growth is rapid and maturity is reached by males in three years and by females in four years.
Throughout history there has been an enormous amount of folklore surrounding toads. They are usually portrayed as being hideously ugly and were intimately associated with the black arts either as familiars of witches or as ingredients in their potions. Yet they have also been reputed to have curative powers, together with a magnificent jewel embedded within their head. Much of the mythology surrounding these creatures undoubtedly arises from the toxins that they are capable of secreting. There are large numbers of toxic glands scattered across the skin, but principle among these are the parotid glands. The parotid glands are a pair of large, conspicuous swellings lying one behind each eye on the side of the head, from which secretions can be seen to flow when the toad is under duress such as during an attack by a predator. To most animals the toxins are poisonous or at best distasteful. Dogs will froth copiously from the mouth after picking up a toad and the lesson is quickly learned, so toxins provide considerable protection to toads. But those same toxins also created considerable demand for toads among medieval pharmacologists and witches. Even today toads are sought out by some for the hallucinatory effects of their secretions!
The jewel said to exist within the head of a toad was believed to confer protection from poisoning on anyone who could retrieve it from the toad and wear it on their person, a belief that presumably originated from the toad itself being a producer of poisons. The alleged great beauty of the jewel may have originally arisen in reference to the eye of the toad which is a deep golden colour and particularly striking in an animal of an otherwise rather drab appearance. It’s not difficult to imagine the abuse that the allure of a mystical jewel must have provoked against the unfortunate toads, particularly as it was recommended that the jewel be removed while the animal was alive.
In fact the unfortunate toad has a rather colourful history of abuse at the hands of Man. A representative illustration is available locally in a reference, from ‘Notes and Queries for Somerset and Dorset XXIII’, to the annual ‘Toad Fair’ in Lydlinch during the early nineteenth century, when a ‘Dr’ Buckland would treat sufferers of ‘The King’s Evil’ by tearing the leg off a living toad and hanging it still quivering, around the patient’s neck where it would be worn for as long as possible. The ’King’s Evil’ was a tuberculosis related skin complaint that was rather prevalent at the time, and Buckland’s spring ‘Toad Fair’ seems to have been immensely popular attracting clients from far and wide.
Common toads are widely distributed across Europe including Britain where they are found throughout England, Scotland and Wales, although they are particularly localised in the north of Scotland. They are absent from Ireland.
On the European mainland they range from the Arctic Circle south to the Mediterranean and from the Iberian Peninsula east into central Asia.
Locally, they are common and widespread within Somerset and the unitary authorities, but rather localised and probably not as abundant as they were when both Baker and Charbonnier, in 1851 and 1887 respectively, described the species as very common throughout the county.
They are a little more discriminating than frogs in their choice of habitat, occurring less regularly in urban areas, or intensively managed farmland. Preferred habitats include scrub, rough grassland and woodland, which is often used for hibernation. Large suburban gardens are frequently used as summer feeding habitat, where a moist retreat such as a cavity beneath a paving slab or a log pile may be adopted for the season. However, gardens seldom have ponds large enough to entice toads to breed. Where suitable ponds exist within the county, toads are usually present although they tend to avoid the dry upland moors and extensive tracts of heathland.
Avery in 1995 found them to be abundant on the Mendips which remains the case today and on the lowlands they are a common sight in the rhynes and ditches across the levels and moors during the springtime.
Unsurprisingly, the most consistent records come from toad crossing sites and many toad patrols across the county are expressing concern that numbers appear to have declined in recent years. Mary Wood writing in 2002 identified a 50% decline in the number of toad patrols in Bristol and the unitary authorities, down from 20 to 10 in a decade, due to the loss of toads from the crossing sites. Of the remaining 10 only four were at that time still recording substantial numbers of toads, around 400 each per year. She blamed the decline on loss of feeding and hibernal sites due to urbanisation, agricultural intensification and either the loss or pollution of remaining ponds. This trend continues to be reported by toad patrols today. Where toads are breeding in fishing lakes she expressed concern that spawn is often removed during vegetation clear-outs in the spring.