Spadefoot toads: an introduction
As those of you who follow my blog will know, I have a trip to Greece planned for October where one of the main targets is the Eastern spadefoot toad (Pelobates syriacus). Therefore I thought it would be a good idea to give some information on what a spadefoot toad actually is, as well as its adaptations and general habits as they are no ordinary toad!
Firstly, spadefoots are one of the most primitive Anurans (or tailless amphibians i.e. frogs and toads) with species found almost worldwide in Europe, North Africa, Asia and North America. But it is the European and American species which are the best known, and in my opinion the most beautiful. The English name ‘spadefoot’ is a reference to the sharp spade or tubercle found on the hind feet which are used for digging into the ground. In Europe three different species occur, the Common spadefoot (Pelobates fuscus), Western spadefoot (Pelobates cultripes) and the Eastern spadefoot (Pelobates syriacus). Whereas the first species is found even in parts of cooler places such as Denmark and Estonia, the other two generally prefer the more arid areas of the Mediterranean. All spadefoot toads are strictly nocturnal although occasionally during the breeding season in early spring they can be seen on the surface during daylight hours, especially if the humidity is high. The main external characteristics that separates them from other toads are the vertical, cat like eye pupils and their skin which is more moist than most toads. Furthermore the tadpoles of these toads are really huge, and in some parts of its range are the favorite meal of many bird species living near fresh water.
Most spadefoots are a lowland species that occupy dry areas such as sand dunes, and cultivated land, but those from North Africa and North America can be found in deserts, such as Couch’s spadefoot toad (Scaphiopus couchii) from Arizona. It is this feature that fascinates me the most about these little toads, their adaptability to hostile environments where amphibians should not, in theory, be able to survive. I have been interested in spadefoots since I lived in S-E Spain, in a very barren region. Here the Western spadefoot toad (Pelobates cultripes) is scarce, and despite my efforts I could not find any adults, although frustratingly I could hear a male calling from beneath the surface of the water on one occasion but I could not locate it. My failure was due to the lack of rain, it only rains for about 2 weeks per year in this region and this is probably how long, on some occasions these toads are actually active. They awaken when the rains arrive and breed often in shallow rain ponds in areas such as farmland, the tadpoles develop very quickly so that before the ponds dry out they can reach metamorphosis. When the sun does reappear they use their ‘spades’ to dig back under the ground where they will remain until the next rains arrive. On some occasions these toads will have a year or two with no activity at all, if there is a sufficient lack of rainfall.
On the Greek island Lesvos, the Eastern spadefoot can be found as well as at some other locations on the Greek mainland. My German colleague Benny Trapp even thinks the toads present on Lesvos are considerably different to those on the mainland and could be a distinct subspecies of their own. Therefore it will be interesting to study them up close and see if it is possible to underline any obvious external differences in morphology. Unless some rain does arrive I may have to wait until the spring of 2010 before I can actually find some adults to examine.
Here is a short film produced by the Arizona Game and Fish Department of Couch’s spadefoot toad (Scaphiopus couchii) calling from its desert habitat
You can find additional photography of the European spadefoot toads on the links below:
For those of you who know a little Spanish, here is a short post by my colleague from Spain about two tadpoles of the Western spadefoot toad (Pelobates cultripes) that we collected to raise and release back at the site. This tiny pond was the only area where we could find any sign of the presence of spadefoots in the arid region, but unfortunately not many tadpoles were present at the time. Here is the link to the Murcia reptile and amphibian blog: