Aggregation protects flexible-shelled reptile eggs from severe hydric stress

Many reptiles lay eggs with Xexible shells that can progressively lose water until lethal dehydration under dry soil conditions. The number of eggs that develop together may inXuence the water exchange in the nest. We hypothesise that egg aggregation could reduce water lost under dry conditions. We exposed aggregated and isolated eggs to severe hydric stress followed by a period of rehy- dration. Hydric stress caused a general loss of water in common chameleon eggs. Initial egg mass did not aVect survival but eggs that had lost more water had higher mor- tality and produced smaller hatchlings. Mass loss was higher and even lethal for isolated Chamaeleo chameleon eggs. However, aggregated eggs lost less water and most survived this period. After hydric stress, all surviving eggs gained mass via water absorption, and aggregation nega- tively aVected water uptake. Isolated eggs hatched at smaller sizes than aggregated eggs. Aggregation also favoured hatching synchrony. Large clutches may favour hatching success of terrestrial Xexible-shelled eggs incu- bated under severe drought conditions.Peer reviewe