Toads dwarfism in Mauritius and Reunion

 Toads dwarfism in Mauritius and Reunion

Guttural toads (Sclerophrys gutturalis) are native to much of the eastern half of sub-Saharan Africa. They were brought to Mauritius from Durban in 1922 to control cane beetles. In 1927 they were introduced to Reunion to control mosquitos.

 In Durban the toad is about 7 cm but in Mauritius the female is 34% shorter and in Reunion 27% shorter. The Mauritius male is 22% shorter but the Reunion male is about the same size. The legs were shorter and stockier.

 ‘Island dwarfism’ observed in the toads as quite remarkable as it is occurring on an extremely shorter time scale.

 The reasons for such rapid evolutionary shrinking include the availability of less food on an island, making smaller bodies more advantageous. The reduction could also be an evolutionary response to a lack of predators. The legs are shorter as there is no long distance to move to.

The author plans to raise island toads in the continent along with the Durban toads to determine whether diet or environmental conditions rather than evolution have been responsible for the dimunition.


J. Baxter-Gilbert et al. Shrinking before our isles: the rapid expression of insular dwarfism in two invasive populations of guttural toad (Sclerophrys gutturalis). Biology Letters. Published online November 18, 2020. doi: 10.1098/rsbl.2020.0651.

 (Extracts from Jake Buehler from SN)