Estudi i caracterització de la població de tortuga de rierol (Mauremys leprosa) al PN del Cap de Creus : biometria i grandària poblacional

Abstract

The species Mauremys leprosa is distributed throughout the Iberian Peninsula, northern Africa, and

exceptionally in southern France. Although it is a common species, several studies indicate that its

populations are declining in most of its range, except in Catalonia, where an increase in its distribution

has been detected. This study characterized and assessed the status of the mediterrenian pond turtle (M.

leprosa) population inhabiting two ponds located in Pla de la Tudela (Cap de Creus).

During the sampling period (May 2022), 53 males, 58 females, and 6 juveniles were recorded. The sex

ratio of the population is very close to parity, while the ratio between adults and juveniles is heavily

biased towards adults, likely due to the sampling method employed. Structurally, the population exhibits

a bimodal profile primarily composed of adult individuals that accumulate in larger size classes.

Sexual dimorphism in the studied population is present in all measured biometric parameters: nCl

(carapace length), Cw2 (carapace width), Ch (carapace height), Bw (bridge width), and Pl (plastron

length) are significantly higher in females, while Pcl (precloacal length) is higher in males. All variables

show an allometric growth pattern relative to nCl, except for Bw and Pcl in females. Additionally,

asymmetric growth between sexes has been detected in Ch, Bw, and Pcl with respect to nCl.

Using statistical software (RStudio and Mark), the population size was estimated using three different

methods: two for closed populations (Petersen and Schnabel) and one for open populations (Jolly-Seber:

Popan). In all cases, the results indicated a population size of around 140 individuals and a high

population density.

Therefore, the population exhibits a sex ratio close to parity and is mainly composed of large-sized adult

individuals. Furthermore, a high density of individuals has been observed, and it is possible that the

population is connected to other population clusters. These factors suggest that the population is likely

in good conservation status