Tag Archives: Toads in Spain

Natterjack toad – Epidalia (Bufo) calamita – Sapo corredor

  • Family: Bufonidae
  • English: Natterjack Toad
  • Scientific: Epidalia (Bufo) calamita
  • Spanish: Sapo corredor
  • Basque: Apo lasterkaria
  • Catalan: Gripau corredor, gripau
  • Galician: Sapo corriqueiro
  • Portuguese: Sapo-corredor
  • Distribution Iberia: Found throughout all Portugal and much of Spain, including the Pyrenees but excluding the northern Atlantic region and the dry central interior, though present in the south.
  • Further distribution: UK mainland and Ireland, France through Germany, Switzerland, Denmark and southern Swedish coastal regions to Poland, Belarus, Ukraine and the Baltic states, and also in Northwest Africa and west Asia. In the UK and Eire the species is restricted in its distribution and considered endangered. In Ireland, found only on the Dingle Peninsula, and distribution in the UK is almost restricted to coastal areas.

The Natterjack toad – Epidalia (Bufo) calamita – Sapo corredor is a species of Bufo, a large genus of so-called “true toads” traditionally found worldwide, although some authorities have now separated the Old World species from the New.

Description

Epidalia (Bufo) calamita is a medium-sized toad with a total maximum length of about 9-10cm in Iberia. (Elsewhere in Europe the species is smaller, males measuring 8cm and females 10cm). The head is wider than long, with a short rounded snout, and the area between the eyes is flat. The tympanum, measuring about half the diameter of the eye, is usually not visible, and if it is, only the front part can be seen.

Natterjack toad - Epidalia (Bufo) calamita - Sapo corredor
Natterjack toad – Epidalia (Bufo) calamita – Sapo corredor with a faint yellow dorsal stripe

Colouration and pattern are rather variable, the overall colour being shades of brown, grey, yellow or green and a pattern of greenish flecks often being present and usually a yellow dorsal stripe running from between the eyes to the posterior. The warts on the back may be chestnut brown or red in colour. In Iberia the flecks may be larger and more clearly defined, and individuals more often lack the characteristic yellow stripe than elsewhere. The underside is off white to light grey, with dark spots. The iris is lemon yellow to green.

The fingers are short, the third being the longest, followed by the first and the second which are equal in length, and the fourth being the shortest. There are two tubercles on the palms. The dorsal skin has a fair number of largish warts, while the skin on the rear of the belly is granular in texture. The toes are relatively short and flattened.

Epidalia (Bufo) calamita can be easily distinguished from Bufo spinosus (the Iberian spiny toad also present in Iberia) normally by the color of the eyes (normally red in B. spinosus and yellow in Epidalia (Bufo) calamita) but also by the shape of the paratoid glands. In Bufo spinosus these are kidney-shaped, bending inwards somewhat in the middle, while in Epidalia (Bufo) calamita they are straight, being further apart at the front than at the back. Epidalia (Bufo) calamita normally also has a thin yellow stripe down the back which is lacking in Bufo spinosus.

 Epidalia (Bufo) calamita

Left: Eye detail of a Natterjack toad. Right: Lifting a stone revealed the daytime hiding place of these two Natterjack toads. (Andalucia)

Across its range the Natterjack toad normally prefers sandy soils and in northern Europe is mainly a lowland animal. However, it can be adaptable: in Spain it can be found in a variety of habitats including arid areas, coastal sands, cultivated fields and mountainous regions.

Feeding and habits

Like most European amphibians the natterjack toad feeds on a variety of invertebrates, but concentrates mainly on arthropods (including various insects and spiders) and less on other invertebrates than the Iberian spiny toad. In Spain, beetles, ants, millipedes, earwigs, grasshoppers and related insects and scorpions have been cited as part of its diet.

The toad is normally a nocturnal animal, coming out at dusk and retiring shortly before dawn, but occasionally may be out in the day, even calling. They may share burrows with other animals or dig their own to a depth of 15-20cm with their forelimbs (and sometimes hind limbs also), or otherwise shelter under stones or logs.

Natterjacks secrete bufotoxin less readily than the Iberian spiny toad, but like the latter resort to the defensive pose in which they stand erect on their limbs and swell their bodies up to make themselves appear much bigger. They also secrete a characteristic smell.

The Natterjack’s gait is also distinctive, being more of a scurrying (likened to that of a mouse) than the hopping or walking normally associated with toads.

Epidalia (Bufo) calamita hibernates on land, as a rule not more than 20m from the original spawning ground (unless it has migrated to a new area) and preferably in a southward-exposed position. The period of hibernation varies with the geographical location and altitude.

In the wild it may be comparatively long-lived, up to 17 years, and in captivity is known to have exceeded this.

Breeding

The Natterjack’s mating season is longer than that of the other European toads, typically lasting 5-6 months. In Iberia it may begin in December, depending on altitude, and last until June. For example Natterjacks in Southern Portugal may start courting in December, those in the centre in February to March, and those in the mountains in May and June; in Leon, from the end of February until May; and Andalucia from mid-January until the end of March.

Natterjacks have a very loud and distinctive mating call amplified by the single vocal sac found under the chin of the male; their name literally means the “chattering toad” – the jack (toad) that natters (talks a lot).

Unlike the Iberian spiny toads (Bufo spinosus), natterjack toads are not tied strongly to their breeding grounds and do not travel far to them but instead prefer to use shallow, often temporary bodies of water, which have the advantage of having few competitors or predators in them. Males usually call from the banks, singly or in chorus, and the calling cry can be heard at up to 2km distance.

Amplexus is axillary, i.e. the male grasping the female under the armpits. The visiting females do not stay long in the water but lay two long strands of 1,500-7,500 eggs which are usually laid directly on the bottom rather than being attached to vegetation (the latter being the case with Bufo spinosus). The eggs develop within 3-10 days (usually less than a week) and as with the Common Toad the resultant tadpoles may form large swarms. From birth to metamorphosis takes 1-2 months: upon metamorphosis the toadlets are less than 3cm long and more diurnal than the adults.

The breeding season varies according to range. In Portugal it lasts between November and April but lasts until June in the high mountains of the Gredos. The long mating season also allows for more than one clutch of eggs to be laid, up to three a year in some cases: heavy rainfall often triggers mating. Sexual maturity also varies with latitude, taking 3-7 years in northern Europe but in Iberia 3 years for males and 4 for females.

Occasionally hybrids of Bufo spinosus and Epidalia (Bufo) calamita are encountered but they are thought to be sterile as no breeding of the hybrids has been observed.

Threats to the Natterjack toad – Epidalia (Bufo) calamita – Sapo corredor

The most common enemies of the Natterjack are various birds, including not only birds of prey such as some owl species and gulls but also apparently innocuous birds as the sparrow. Colubrid snakes such as the Grass Snake (Natrix natrix) and Viperine Snake (Natrix maura) also prey on Natterjacks and their tadpoles. Tadpoles are also preyed upon by various water invertebrates including the semi aquatic raft spider Dolomedes fimbriatus, which also takes freshly metamorphosed young.

The Natterjack’s longer mating seasons, relatively large eggs and tadpoles, tolerance to warm weather and even brackish water, and ability to emigrate to new areas stand it in better stead to cope with changing conditions than some other amphibians. However, it is adversely affected by the loss of invertebrate diversity in its habitat which reduces the amount of prey available.

Natterjack toad - Epidalia (Bufo) calamita - Sapo corredor
Natterjack toad – Epidalia (Bufo) calamita – Sapo corredor

Simila Species

Iberian spiny toad – Bufo spinosus – Sapo comun Ibérico


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Iberian spiny toad – Bufo spinosus – Sapo comun Ibérico

  • English: Iberian spiny toad
  • Scientific: Bufo spinosus
  • Spanish: Sapo común Ibérico
  • Basque: Apo
  • Catalan: Gripau comú
  • Galician: Sapo común
  • Aragonese: Zapo común
  • Portugese: Sapo comum
  • Distribution: Iberian Peninsula and southwestern France (north to about Caen and about Lyon; an isolated population on the Isle of Jersey (United Kingdom); northwestern Africa in the northern mountains of Morocco, Algeria, and Tunisia.
  • Species name changes: The common toad was first given the name Rana bufo by the Swedish biologist Carl Linnaeus in the 10th edition of Systema Naturae in 1758. In this work, he placed all the frogs and toads in the single genus Rana. It later became apparent that this genus should be divided, and in 1768, the Austrian naturalist Josephus Nicolaus Laurenti placed the common toad in the genus Bufo, naming it Bufo bufo. The toads in this genus are included in the family Bufonidae, the true toads. Various subspecies of B. bufo have been recognized over the years. The Caucasian toad is found in the mountainous regions of the Caucasus and was at one time classified as B. b. verrucosissima. It has a larger genome and differs from B. bufo morphologically and is now accepted as Bufo verrucosissimus. The spiny toad was classified as B. b. spinosus. and is found in France, the Iberian Peninsula and the Maghreb. It grows to a larger size and has a more spinier skin than its northern counterparts with which it intergrades. It is now accepted as Bufo spinosus. The Gredos toad, B. b. gredosicola, is restricted to the Sierra de Gredos, a mountain range in central Spain. It has exceptionally large paratoid glands and its colour tends to be blotched rather than uniform. (However, It is now considered to be Bufo spinosus as well).

The Iberian spiny toad – Bufo spinosus – Sapo comun Ibérico is a member of a large genus of so-called “true toads” traditionally found worldwide, although some authorities have now separated the Old World species from the New.

Description

A relatively large toad with a total maximum length of about 21cm, though males are rather smaller at 9-10cm and the average female is 15cm. The head is longer than wide, with a short rounded snout, and the area between the eyes is either flat or concave. The tympanum is barely visible, measuring about half the diameter of the eye. The fingers are short, the third being the longest, followed by the the first and then the second and fourth, these latter two being of equal length. There are two tubercles on the palms. The toes are relatively long and flattened.

In coloration the adult Iberian spiny toad is usually a brownish colour, but there is variation, especially in the southern part of its range. Colour variations include sand, brick-red, dark brown, grey and olive, as well as darker marks against the overall tone. The underside is whitish or grey, often with a marbled effect. The eye is copper or gold.

Bufo spinosus can be distinguished from the Natterjack toad – Bufo calamita (also present in Iberia) normally by the color of the eyes (normally red in B. spinosa and yellow in B. calamita) but also by the shape of the paratoid glands. (Look to the rear of the eyes). There may be a raised area on both sides of the head containing pore-like openings. These areas are known as the parotoid glands. Not only can their presence be a key to the species, but also their shape, since in some species the gland area is straight and in others bent inwards. In Bufo spinosus these are kidney-shaped, bending inwards somewhat in the middle, while in Bufo calamita they are straight, being further apart at the front than at the back. Bufo calamita normally also has a thin yellow stripe down the back which is lacking in Bufo spinosus. (Bufo calamita also goes by the scientific name of Epidalia calamita).

Iberian common toad - Bufo spinosus - Sapo comun Ibérico

LEFT: Iberian common toad – Bufo spinosus in water. RIGHT: Natterjack toad – Bufo calamita. (Note the yellow eye)

Diet of the Iberian spiny toad – Bufo spinosus – Sapo comun Ibérico

Like most European amphibians the Iberian spiny toad feeds on a variety of invertebrates. In Spain beetles, ants, centipedes, millipedes, spiders, grasshoppers and related insects have been cited as part of its diet, as well as occasionally rodents (presumably mice, voles or similar small species), a reminder that these toads are relatively large. (However one observer states that they do not eat slugs as they probably don’t taste very nice? 🙂 ).

Habits

The toad is normally a nocturnal animal, although it can be found out and about in the open during wet weather or in the breeding season.

I once encountered a pair in amplexus by the stream in rainy weather during the daytime (picture further down the page), the pair making little or no attempt to move. (Amplexus = The copulatory embrace of frogs and toads, during which the male fertilizes the eggs that are released by the female).

Unlike frogs, toads rarely hop but prefer to walk.

They have two effective anti-predator devices: bufotoxin, a white milky substance which is secreted via the paratoid glands behind the eyes and which is extremely distasteful (and sometimes poisonous) to many predators, and the defensive pose in which they stand erect on their limbs and swell their bodies up to make themselves appear much bigger. This defence may be especially useful against the Grass Snake (Natrix natrix) since this species of snake does not seem to be affected by bufotoxin.

Bufo spinosus has a winter rest period from October-November until February-March. Most spend this period on land rather than in water.

Breeding

During the breeding season, males arrive first at their home ponds/rivers and can remain for some weeks (3-28 nights) whereas the females may make just a short visit (3-6 nights) to find a mate and lay their eggs. Mating itself is a rough-and-tumble affair. Since males usually outnumber females by four or five times they must fight for mates and often end up clasping different species, fish or even inanimate objects, or else several home in on one female and form a breeding “ball”.

Iberian common toad - Bufo spinosus - Sapo comun Ibérico

Note the copper/red coloured eye of these mating Iberian Spiny toads.

Males clasped by other males have a special “release call” to notify the offender of his mistake! Needless to say this level of competitive activity is stressful for all the participants, and toad mortality is quite high as a result. Females lay 3,000-8,000 eggs in two strings which they lay simultaneously over the course of up to several hours, depositing these on aquatic vegetation often in places where there is good sunlight.

The eggs develop within 2-3 weeks and the resultant tadpoles form large swarms. At metamorphosis they are 7-12mm long and more diurnal than the adults.

Iberian common toad - Bufo spinosus - Sapo comun Ibérico
Iberian common toad – Bufo spinosus – Sapo comun Ibérico – With a tail and tiny back legs.

The breeding season varies according to range. In Portugal it lasts between November and April but lasts until June in the high mountains of the Sierra de Gredos.

Sexual maturity also varies with latitude, taking 3-7 years in northern Europe but in Iberia 3 years for males and 4 for females. Occasionally hybrids of Bufo spinosus and Bufo calamita can be found but they are thought to be sterile as no breeding of the hybrids has ever been observed.

Threats to the Iberian spiny toad – Bufo spinosus – Sapo comun Ibérico

Like all amphibians it is faced with the threats of habitat loss, chemical pollution and, more seriously, long-term climate change. As a species it has often been persecuted in the past by humans, partly because of a cultural association with its use by witches.

Despite the bufotoxin to deter casual predators, Bufo spinosus is also preyed on by various birds of prey (eagles, buzzards, kites, and owls) and the Grass Snake (Natrix natrix).

The toad fly Lucilia bufonivora also causes depredation by laying its eggs on the toad’s back. The ensuing larvae migrate to the nasal cavities of the toad and feed on the tissues in this area, causing the death of the host within 2-3 days.

One recent study estimates that adult populations have a complete turnover of 4-5 years, ie a loss/death rate of up to 25% of adults each year.

Iberian spiny toads are noted for their migrations towards their home ponds, a process which may begin in the autumn but which peaks in spring. At this time they are most vulnerable to road traffic, which in the past has taken a high toll.


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