Description
Bufo spinosus is a large and robust toad with a snout-vent length of 58.6 - 112 mm in males and 65 - 180 mm in females. Its head is relatively broad, and the region between the eyes is either flat or slightly concave. The snout is short and rounded. The tympanum is subtly visible and rounded, and its diameter does not exceed half the eye. The parotoid glands are large, elongated, and divergent at the posterior end. The eyes are prominent with a horizontally oval pupil. The skin is warty on the back and granular on the underside. Its warts usually end in a keratinized tip, resulting in a spiny appearance, though not all individuals express this. These keratinized warts are especially prominent between the corner of the mouth and the parotoid. The fingers, of which the third is the longest, are short. No information is available on the relative finger lengths. There are two palmar tubercles on the hands. The hind limbs are webbed, and have a pair of metatarsal tubercles, with the internal metatarsal tubercle being larger than the external metatarsal tubercle. No information is available on the relative toe lengths. There is a pair of subarticular tubercles on the hands and the feet that may be fused in older adults (Ortiz-Santaliestra 2014).

The larvae are described from Tunisian specimens. They can reach a total length of up to 30 mm, and their eyes are situated dorsally on the head. They have a sinistral spiracle and a medial anus. The end of the tail is rounded (Hassine and Escoriza 2014).

It can be differentiated from other sympatric species of toad by its intensely red-colored iris. In comparison to allopatric populations of B. bufo, a morphologically similar species, B. spinosus has more widely divergent parotoids and larger inner metatarsal tubercles. In males, the inner metatarsal tubercle is less rounded in B. spinosus than in B. bufo (Arntzen and McAtear et al. 2013, Ortiz-Santaliestra 2014).

In life, this species usually shows a uniform brown coloration, but may also have shades of yellow, red, green, gray, and/or black. The iris is noticeably red. There may or may not be a dark or light mottled design in the back. Its ventral coloration can be yellowish or pale brown, but may differ in juveniles. The larvae are uniformly black or dark brown, and have black speckling on the tail fin. (Hassine and Escoriza 2014, Ortiz-Santaliestra 2014).

In addition to the aforementioned variation in coloration, B. spinosus varies in body size, parotoid gland size, and in presence of warts on the skin. Body size and presence of warts have evolved independently in several lineages of the B. bufo species complex, possibly as ecological adaptations. Sexual dimorphism is significant in mature individuals. Females are bigger than males and have less robust arms relative to their body size. Males have nuptial pads on their first three fingers, whereas females have no nuptial pads at all (Luescher et al. 2001, Ortiz-Santaliestra 2014).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Algeria, Andorra, France, Morocco, Portugal, Spain, Tunisia, United Kingdom

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (4 records).

The range of B. spinosus extends from northwestern Africa to the Iberian Peninsula, and into southwestern France. Populations have also been found on Jersey, within the Channel Islands. Within North Africa, it is found in Morocco, Algeria, and the extreme northwest of Tunisia. It occurs between 0 - 2600 m asl, and is found in a wide variety of habitats, such as forests, riverbeds, bogs, marshes, sand dunes, shrublands, steppes, meadows, agricultural areas, and suburban areas (Arntzen and McAtear et al. 2013, Ortiz-Santaliestra 2014, Recuero et al. 2012).

Life History, Abundance, Activity, and Special Behaviors
Bufo spinosus is a primarily nocturnal species, though it may also be active in the daytime during the reproductive season. It generally prefers standing bodies of water, though it is also found near areas of flowing water. It is very drought-tolerant, due in part to its ability to absorb 21% of its body weight in water per minute. It is assumed to be able to tolerate huge losses of water as B. bufo, a congeneric species, can lose up to 20% of its weight in water without any deleterious effects (Ortiz-Santaliestra 2014).

Males have a weak and short mating call, and call throughout the day and night. Breeding usually takes place in spring, though this varies geographically, with populations in warmer areas generally breeding earlier in the year and populations in colder areas generally breeding later in the year. Amplexus is axillary. Females lay anywhere from 2000 – 11000 eggs at a time, which are around 3 mm in diameter and connected in strings and attached onto aquatic vegetation. It has a geographically variable larval period, with the period lasting 65 - 108 days in the southern Iberian Peninsula, and 55.5 days in Doñana National Park in Andalusia, Spain (Ortiz-Santaliestra 2014).

The adults are primarily insectivorous, though the types of arthropods they consume vary widely geographically. Some populations consume primarily beetles, others consume primarily ants, and others consume a variety of prey. The tadpoles are omnivorous, and consume detritus, algae, plankton, aquatic plants, and arthropods. This species is preyed upon by various mammals, birds, and snakes. As a result, it has evolved antipredatory behaviors such as expanding its body by inhaling air, rising up on its legs while exposing the back of its head, and secreting toxins. Additionally, B. spinosus is parasitized by Lucilia bufonivora and L. sericata, which are flies, and Batracobdella algira, Limnatis nilotica, and Hirudo troctina, which are leeches (Hassine and Escoriza 2014, Ortiz-Santaliestra 2014).

Trends and Threats
Bufo spinosus is not considered threatened in Portugal, but it is shown to be declining in Spain, especially in more arid areas. Additionally, the species has been declining on the island of Jersey, possibly due to loss of breeding sites and increasing allopatry of populations. It suffers from loss of habitat due to deforestation, urbanization. Its numbers are directly affected by invasive species such as mosquitofish, and the presence of cars, which results in high road fatalities. There have been efforts made to protect local populations, such as creating migratory corridors to allow toads to bypass road without the risk of getting run over by vehicles, and creating aquatic habitats to mitigate the effects of habitat loss (Ortiz-Santaliestra 2014).

Relation to Humans
They are commonly found near areas of human activity (Ortiz-Santaliestra 2014).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Disturbance or death from vehicular traffic
Prolonged drought
Drainage of habitat
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Predators (natural or introduced)
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species authority is: Daudin, F. M. (1803). An. XI. Histoire Naturelle, Générale et Particulière des Reptiles; Ouvrage Faisant suit à l'Histoire Naturelle Générale et Particulière, Composée par Leclerc de Buffon; et Rédigée par C.S. Sonnini, Membre de Plusieurs Sociétés Savantes, Paris.

Bufo spinosus was formerly considered a subspecies of B. bufo, but is now recognized as a distinct species within the B. bufo species complex, which consists of B. bufo, B. eichwaldi, B. spinosus, and B. verrucosissimus. Bufo spinosus is sister to the clade B. bufo and B. verrucosissimus, while B. eichwaldi is sister to all other Bufo species within the B. bufo species complex (Arntzen and McAtear et al. 2013, Arntzen and Recuero et al. 2013, Recuero et al. 2012).

The species epithet spinosus is derived from Latin, meaning "thorny", which is in reference to the spiny appearance of its skin (Ortiz-Santaliestra 2014).

This species was featured as News of the Week on 20 August 2018:

Identifying the biological mechanisms underlying seasonality in infection can enable better prediction and prevention of future infection peaks. A recent study tracked Spiny Common Toads (Bufo spinosus) within and across annual cycles to assess seasonal variation in movement, body temperatures and infection from the fungal pathogen, Batrachochytrium dendrobatidis (Bd). Across annual cycles, toads did not consistently sustain infections but instead gained and lost infections from year to year. Radio-tracking data showed that infections were lost after breeding migrations and pronounced seasonal variation in toad body temperatures may be the reason. This study provides evidence of migratory recovery (i.e., loss of infection during migration) in a wild populations and may help explain differences in susceptibility to Bd (Written by Vance Vredenburg).

References

Arntzen, J. W., McAtear, J., Recuero, E., Ziermann, J. M., Ohler, A., van Alphen, J., Martínez-Solano, I. (2013). ''Morphological and genetic differentiation of Bufo toads: two cryptic species in Western Europe (Anura, Bufonidae).'' Contributions to Zoology, 82(4), 147-169.

Arntzen, J. W., Recuero, E., Canestrelli, D., Martínez-Solano, I. (2013). ''How complex is the Bufo bufo species group?'' Molecular Phylogenetics and Evolution, 69, 1203-1208.

Daudin, F. M. (1803). An. XI. Histoire Naturelle, Générale et Particulière des Reptiles; Ouvrage Faisant suit à l'Histoire Naturelle Générale et Particulière, Composée par Leclerc de Buffon; et Rédigée par C.S. Sonnini, Membre de Plusieurs Sociétés Savantes, Paris.

Hassine, J. B., Escoriza, D. (2014). ''Bufo spinosus in Tunisia: new data on occurrence, parasitism and tadpole morphology.'' Herpetological Bulletin, 127, 22-32.

Luescher, B., Grossenbacher, K., Scholl, A. (2001). ''Genetic differentiation of the common toad (Bufo bufo) in the Swiss Alps.'' Amphibia-Reptilia, 22(2), 141-154.

Ortiz-Santaliestra, M. E. 2014. Sapo común – Bufo spinosus Daudin, 1803. En: Enciclopedia Virtual de los Vertebrados Españoles. Salvador, A., Martínez-Solano, I. (Eds.). Museo Nacional de Ciencias Naturales, Madrid. http://www.vertebradosibericos.org/

Species Account Citation: AmphibiaWeb 2019 Bufo spinosus: Spiny Toad <https://amphibiaweb.org/species/7754> University of California, Berkeley, CA, USA. Accessed Nov 23, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 23 Nov 2024.

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