Testudo marginata
Testudo marginata
Testudo marginata is believed to have been introduced to Sardinia from Greece probably in historical or earlier times, and has acclimated to it so well that the island populations appear to be decidedly numerous today, especially in some areas. The anthropization of habitats, but above all uncontrolled and illegal harvesting, as well as the recurrent fires that burn hectares of Mediterranean scrub, have significantly reduced their consistency compared to the past. Maier (1994) indicates Sardinian populations as subspecies of the Greek nominal species, however recent genetic investigations seem to deny it. What differentiates the Sardinian populations of Testudo marginata more than the Greek ones are the generally larger dimensions and an on average more rounded carapace. But the high variability between the specimens in nature does not allow to identify univocal parameters. In any case, it seems that for the same length, the weight of a Sardinian specimen is on average higher. The colors are normally bright in young specimens with a certain degree of variability, but tend to fade with age. Completely melanic specimens are not rare in these populations, but also interesting and frequent cases of albinism. Testudo marginata reaches on average 30 cm and 3 kg in weight, but specimens of 40 cm and above and 5/8 kg in weight are not rare. Prolific species, it can make up to 4 ovations per year, exceptionally 5, from April to early July, laying 6-16 eggs each, on average 8-12. The babies begin to emerge from the nests in mid-August. Compared to Testudo hermanni, it tends to have a longer period of activity. The species measures 15 cm in carapace length around the fifth year of age, doubling it around 10-12 with the achievement of sexual maturity.
As in the case of Sardinian populations, traced back to the nominal species after careful genetic analysis, also the alleged Testudo marginata weissingeri, are nothing more than a dwarf form that lives in a restricted area of Mani in Greece.
Although the vulnerability of the species is lower than other Mediterranean tortoises, Testudo marginata is included in appendix II of the CITES and in annex A of the European regulation.
Notes and insights on Testudo marginata
Testudo marginata is the Mediterranean tortoise that reaches the largest medium size, showing in addition a peculiar bell of the rear marginal plates, hence the name of the species, which we do not find in any other turtle in the world. Its large size counterbalances the smallest Mediterranean turtle, and one of the smallest in the world, namely the Testudo kleinmanni. It is probably not a coincidence that both species have a common origin and are genetically related. Testudo marginata is an easy-to-manage species, which however impressively undergoes breeding errors with nothing short of aberrant growths, such as remaining small and flattened as if they were a pancake. Its life cycle is identical to that of the other Mediterranean Testudo, however the generous dimensions and the propensity not to carry out a continuous lethargy, in any case shorter, see it active for almost the entire duration of the year and it is not uncommon to see it exposed the soft rays of the sun as early as the third week of January. The reproductive cycle in its area of origin, begins in the first days of April and usually ends within the last week of June. However, depending on the area and climatic fluctuations, early depositions may occur in late March and early July. The choice of the place of deposition is very accurate, as the greater depth of the nest requires that the point is sufficiently exposed.
Peculiarity of the species is the recurrent discovery in nature, especially in Sardinia, of albino mutants tyrosinase positive (T+), demonstrating the fact that this mutation is not negatively selected and remains among the populations. It is not clear if this is due to the founding effect, that is, present in the first specimens introduced on the island, or if simply the mutation occurred spontaneously and then spread, the fact is that its persistence could be read as an alternative color variant with an adaptive and mimetic value, considering that at birth the babies find a dry and yellowed nature in which the peculiar coloring pattern is confused better than the normal one which in these conditions appears to be of great contrast and visibility.
