The Common Toad

Intro

The Common Toad (Bufo bufo) is one of two species of toad in Britain; the other – the Natterjack Toad (Epidalea calamita) -  is very localised, mostly in coastal areas. Outside Britain, members of the Bufo bufo complex are found throughout mainland Europe and northwest Africa. Toads largely occupy forested and wooded areas, especially in wet locations, as well as moors, fields, parks and gardens, often well away from permanent standing water. Toads are not without superhero abilities: one individual was recorded happily going about its business at a depth of 324 feet (99 m) on the bottom of Loch Ness!

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Description

Common Toads – hereafter referred to simply as toads - are usually a greyish-brown colour with gnarly, lumpy skin; in general, females are browner and males greyer, though this is often not apparent at night. Adult males are up to 8 cm in length; mature females are larger and exceptional individuals may reach as much as 15 cm. Distinctive features of toads include protruding eyes with slit-shaped, horizontal pupils and large glands behind the eyes – known as paratoid glands – which can secrete a noxious substance (bufotoxin) to deter potential predators. Unlike frogs, there is no external vocal sac. The body is squat and low to the ground; the limbs are comparatively short and the fingers turn inwards. The hind legs offer a foolproof way of distinguishing toads from Common Frogs: toads have relatively short back legs and there is no webbing between the end of the toes. Toads tend to walk much more often than they jump – in contrast to frogs – though they will jump in order to get away fast.

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Activity

The annual life cycle of the toad can be separated into 3 periods: (i) winter sleep; (ii) breeding time; (iii) feeding time. Outside the breeding season, adult toads are generally terrestrial, inconspicuous and solitary. During the day they usually remain hidden in a lair hollowed out amongst leaf litter, dense vegetation or under a stone. They are most active in wet weather, emerging at dusk to find prey which generally takes the form of invertebrates: slugs, worms, woodlice and flies. Toads hunt using vision and can see well in the dark, much better than a human. Each morning, toads will return home from their nocturnal activities and they may occupy the same site for several months. Toads shed their skin periodically, through growth, usually eating it as it comes away. 

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Breeding

Toads are well known for their elaborate springtime breeding behaviour, as large numbers migrate to specific bodies of water to reproduce. Adults generally use the same location year after year and more than 80% of male toads have been recovered at the pond where they were themselves spawned (called a natal pond). Toads are known to orientate using olfactory, magnetic and visual cues and will return to their natal pond from significant distances. Males tend to arrive at breeding sites before females, to occupy a competitive position, though disputes seem to mostly be settled through vocalisations rather than direct fighting. Males outnumber females at most breeding sites; female mortality seems to be higher overall and many individual females will choose to skip reproduction for a year.

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During the breeding season, male toads develop black growths (nuptial pads) on the first three fingers which are used to grasp the female when mating, in an enthusiastic embrace known as amplexus (literally, ‘hug’ in Latin). A successful pair remain in amplexus for several days, the male fertilising the eggs as they are laid by the female; amplexus is stressful for both male and female toads, and mortality is high during this period. The eggs are unlike the more familiar frogspawn, being encased in long, double, stringy masses; as the embracing couple move around their environment, the eggs become entangled in aquatic vegetation. After 2-3 weeks, tadpoles (toadpoles) hatch from the eggs. In a similar manner to frogs, the tadpoles undergo metamorphosis after several months of development, emerging from the water as fully formed, miniature toads, less than 1.5 cm in length and ridiculously cute. Toads are thought to reach maturity after 3-7 years and generally survive for 10-12 years in the wild. In captivity, toads have have lived for up to 50 years.

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