Annual climate fluctuations can influence iguana growth and degrowth

Abstract It has been proposed that some vertebrates can undergo a reduction in body size in response to harsh environmental conditions. However, there is a paucity of evidence regarding the reality of this phenomenon. The objective of this study was to examine the possible occurrence of degrowth in a population of Lesser Antillean iguanas and to investigate whether it might be linked to climatic variations. We used a database of 2871 wild iguanas from the islands of Saint-Barthélemy, Chancel, and Guadeloupe (French Antilles). Body size was assessed through measurements of the snout–vent length (SVL) and body mass. Morphological analyses revealed that 44.3% of iguanas showed a decrease in body size. The analyses also showed that individuals can undergo both growth and degrowth multiple times, with 31.5% exhibiting such fluctuations across years. To assess the robustness of these results, we used body mass measurement as a complementary proxy for body size measurement. As expected, we found a significant positive correlation between variations in SVL and body mass. This relationship was consistent across sexes. With respect to climatic variations, rainfall and temperature in the preceding year significantly influenced SVL variation. These results challenge the traditional view of continuous reptile growth and suggest an adaptive mechanism enabling individuals to cope with environmental stressors.