Volume 70 (2020) Issue: 2020 No#4

Observation of Hermann’s tortoise (Testudo hermanni) clutching without the presence of males and eggshell mortality on a large tortoise farm in Slovenia over a three-year period

Author(s): Stvarnik Mateja, Lindtner-Knific Renata, Štokar Žan, Gregurić Gračner Gordana, Mićunović Jasna, Dovč Alenka

Keywords:breeding; reproduction; incubation; eggshell mortality; Testudo hermanni

The aim of this study was to determine the percentage of hatched and fertilized eggs in female Hermann’s tortoises before and after the removal of males after breeding. A breeding group of Testudo hermanni boettgeri with 50 females and 12 males was included in the study. In the first year, all adults were together in the same habitat until reproductive activity was observed. After the end of May, the males and females were separated for the next two active seasons. The number of eggs and number of second clutches decreased gradually. In the first year, 76.0% of females laid eggs; in the second year, 24.0%; and in the third year, only 8.0%. Second clutches were observed in ten females (26.3%) in the first year, while in the next two years, one female had a second clutch. There was a small but significant correlation between the weight of a single tortoise and the number of eggs laid but no significant correlation between the weight of the tortoise and its average egg weight. The weight (15.1-16.8 g), length (33.9-36.1 mm) and width of each egg (27.5-28.0 mm) was measured. During the laying season, the eggs were put into incubators. The incubation length varied from 52 to 70 days. After the end of incubation, eggshell mortality and its causes (19.3-52.5%) were examined. In the first year, the viability rate of the incubated eggs was 80.7%; in the second year, 80.5%; and in the third year, 47.8%. Among the unhatched eggs in the first year, 62.5% were unfertilized, 53.1% were infected, 28.1% were dehydrated and 21.9% were found in various stages of embryonic development.