Annual climate fluctuations can influence iguana growth and degrowth

It has been proposed that, in some vertebrates, individuals possess the capacity to undergo a reduction in body size, which might be a response to harsh environmental conditions. However, there is a paucity of evidence regarding the reality of this phenomenon and its causes. The objective of this study was to examine the possible occurrence of degrowth in populations of Lesser Antillean iguanas, and to investigate whether it may be linked to climatic variations. We employed a database comprising 2,871 wild iguanas that were collected on the islands of Saint-Barthélemy, Chancel and Guadeloupe in the French Antilles. Body size was assessed through measurements of the snout-vent length (SVL) and weight of subjects. Morphological analyses revealed that 44.3% of iguanas show a decrease in body size. The analyses also showed that individuals can undergo both growth and degrowth multiple times over their lifespan, with 31.5% of them exhibiting such fluctuations across years. In order to assess the robustness of these results, we used individual body mass as an independent variable and found a significant positive correlation between variations in SVL and body mass. This relationship was consistent across sexes, providing strong support for the observed patterns of degrowth. With respect to climatic variations, rainfall and temperature from the year prior to measurment had a significantly influence on SVL variation. These results in Lesser Antillean iguanas challenge the traditional view of continuous reptile growth and suggest an adaptive mechanism that enables individuals to withstand transitory environmental stressors.