The ability to estimate quantity, which is crucially important in several aspects of animal behaviour (e.g. foraging), has been extensively investigated in most taxa, with the exception of reptiles. The few studies available, in lizards, report lack of spontaneous discrimination of quantity, which may suggest that reptiles could represent an exception in numerical abilities among vertebrates. We investigated the spontaneous ability of Hermann's tortoises (Testudo hermanni) to select the larger quantity of food items. Tortoises were able to choose the larger food item when exposed to two options differing in size, but equal in numerousness (0.25, 0.50, 0.67 and 0.75 ratio) and when presented with two groups differing in numerousness, but equal in size (1 versus 4, 2 versus 4, 2 versus 3 and 3 versus 4 items). The tortoises succeeded in both size and numerousness discrimination, and their performance appeared to depend on the ratio of items to be discriminated (thus following Weber's Law). These findings in chelonians provide evidence of an ancient system for the extrapolation of numerical magnitudes from given sets of elements, shared among vertebrates.

Many animals obtain reliable information about potential mates, including whether they are conspecific, sexually mature, and healthy or not, mostly from olfactory cues. Previous experiments with snakes and lizards have shown that individuals can recognize conspecifics, sex, mating status, and health condition of potential partners by chemical cues. Using choice experiments, we examined whether both male and female Hermann's Tortoises, Testudo hermanni, can detect and distinguish the odor of conspecifics from that of another species and an odorless control, and are able to discriminate sex and sexual maturity of individuals by chemical cues. We found that both sexes correctly discriminated between their own species and another species' odors, but only males can distinguish sex and sexual maturity of potential mates by olfactory cues. These results indicate a sexual dimorphism in olfactory sensitivity in this species that might be derived from sexual selection and suggest that males and females should rely on different communication channels during social interactions.