Since 2006, we have undertaken annual campaigns to individually label, using microchips, all specimens of the Common toad (Bufo spinosus) that breed in the permanent ponds of Peñalara. The breeding season usually lasts about six weeks, beginning in late April or early May, depending on the weather conditions. The first arrivals to the water are the males, followed a few days later by the females. The water bodies where the Common toads of Peñalara reproduce are: Laguna de los Pájaros, Laguna Grande de Peñalara, Laguna Chica, Charca Larga, Charca de las Piedras and Charca de la Mariposa.
The working sessions begin at dusk, when the males start to come out of hiding from the banks to try to capture the females who come to the water ready to release eggs. Using nets we capture every toad one by one, and check if they already have a microchip from previous years and record its identification number or if the animal does not have an implanted microchip, a new microchip is placed to permanently identify (tag) the animal. We also measure its length, record weight, determine gender, and take skin samples for laboratory analysis to check if they are infected with the fungus that causes chytridiomycosis. Nighttime is our busiest period and our work ends in the early hours of the morning; during this time we can capture more than 100 specimens.
Through tracking the Common toads, we have identified more than 1,200 individuals, of which 69% are males and 31% females. This work, of nearly a decade, has enabled us to know, for example, that once an animal chooses a breeding site, they do not change it during their lifetime. We also found that at least 15% of the specimens are 10 years or older, and we have tagged a few animals whose age exceeds 13 years. The males spend about 15 days in the ponds of Peñalara trying to breed with as many females as possible, which only spend about 3 days at most, in the water.