The relationship between temperature, growth rate and body condition of Bufo bufo toadlets prior to their first hibernation

The effect of environmental temperature on the growth and body condition of common toad (Bufo bufo) toadlets was studied during their first terrestrial growth season, following metamorphosis, at a pond in south Dorset, UK, between 2010 and 2021. Toadlet samples were collected annually on the first day of emergence and then approximately once a week until late September/early October. In total, 15-19 samples were collected annually depending on the duration of the toadlet activity season. Toadlet snout-vent length (mm) and body mass (mg) of each captured toadlet was measured and their body condition (Scaled Mass Index: SMI) estimated both annually and for each annual quarter season. Toadlet growth rate and SMI varied between years and were significantly correlated with the duration of their first growth season and its lowest recorded temperature. Growth rate declined as the duration of the growth season increased whilst the reverse was true for SMI. Growth rates also increased as temperatures increased and vice versa for SMI. SMI was inversely correlated to growth rate and suggest that toadlets may enter their first hibernation larger, but in poorer condition, following warm summers than cool summers, and that this may have the potential to reduce their survivorship during a following mild winter. Assuming that similar relationships, between growth rates, body condition and environmental temperatures are not restricted to toadlets during their first terrestrial growth season, then this scenario may also be applicable to subsequent juvenile stages, further increasing the potential consequences for individual survival and fitness.