Differences in Reproductive Success in Young and Old Females of a Long-Lived Species

Abstract

Long-lived species are particularly interesting for investigation of trade-offs that shape reproductive allocation and the effective contribution to the next generations. Life history theory predicts that these species will buffer environmental stochasticity via changes in the reproductive investment, while maintaining high adult survival rates. The spur-thighed tortoise was selected as a case study in order to investigate the relationship between the linked maternal characteristics (size and age) and related traits in their hatchlings. We tracked naturally emerging hatchlings from young and old females under semi-natural conditions to test variations in hatchling numbers, body mass, size and survival over two years. We used linear mixed-effect models to analyze variations in hatchling body mass and size, and a mark–release–recapture framework to model their survival. Our study illustrates that old females of long-lived species have greater offspring numbers, greater survival and smaller size when compared with those of young females. The interannual variability evidenced the reduced offspring number and survival in the lower autumn rainfall and spring mean temperature year. Our results highlight the role of maternal age and climatic conditions in the population dynamics and the need for long-term studies of reproduction traits for designating adequate conservation strategies.

The shell measurements that best describe sexual dimorphism in the spur-thighed tortoise <em>Testudo graeca</em> from Algeria

“…Our results also reflected a more variable size upon female maturity (as reported in NE Algeria by Rouag et al, 2007), which probably results from a longer growth period before and after maturity (Rodríguez-Caro et al, 2013). In this line, differences in female adult sizes have been recently related to differences in their reproductive outcome: bigger females have more offspring with newborns displaying higher survival rates (Segura et al, 2021). Hence it would seem beneficial for females to invest in growth, even after reaching maturity.…”

“…In the Testudo genus, SShD has been even related to the particular features of courtship, which involves the male butting the female's carapace with the thickened gular area of the plastron (Willemsen & Hailey, 2003). Larger sized abdominal, vertebral and plastral plates in females clearly indicate a direct relation between larger volume and increased clutch size (Segura et al 2021).…”