The Mediterranean tortoise (Testudo hermanni)

Fauna from Menorca: the Mediterranean tortoise

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The Mediterranean tortoise (Testudo Hermanni), called simply, in Menorca, the land tortoise, is a species which lives only on the continent of Europe, from the north east of the Iberian Peninsular to Turkey and in the principal Mediterranean islands. There are two different subspecies. That which lives in Menorca is exclusive to the western Mediterranean. Wild tortoises are found only in the Balearic Islands of Mallorca and Menorca, where they were introduced by us, it is not known when. Genetic studies have been made that determine two different origins of the Menorcan tortoise. One origin is very old, of some thousands of years, coming from Sicily or Sardinia. The other origin is much more recent coming from the continental tortoises. The tortoises from the south of the island are of the oldest origin on the island, while those in the north originate from the continent.

Tortoises are the oldest group of reptiles. The first known species dates from the Triassic Period, more than two million years ago. Their principal characteristic is that they are covered with a shell, which, in the case of the Mediterranean tortoise, is made up of 52 horny plates covered by a very thin corneal layer. The black and yellow colouring differentiates it from the subspecies of the east. The underside is called the plastron and this has two black parallel stripes. One unique fact of this species is the presence of a claw on the carapace divided longitudinally in two over the neck of the tortoise, so that it is differentiated from similar species, such as the mora tortoise, found in Mallorca which originates from the south of the Peninsular and north Africa.

The females can reach 22 cms in length but the males are much smaller reaching 20 cms. There are three details for distinguishing the sexes. The females tend to be more oval in shape, the plastron is flat, the neck is shorter and the plates above the tail are smaller to allow the passage of eggs during the laying period. The plastron of the males is sunken to enable copulation. They can live to about a hundred years. Their age can be guessed by counting the number of rings of the plates on the carapace, although in some older animals they become blurred.

Tortoises are ectothermic, that is to say their metabolic activity depends on the ambient temperature. That is why they usually spend the winter months hibernating, half buried, although on sunny days we can sometimes see a few grazing. Their normal period of activity lasts nine months, between March and October. They are also inactive during the middle part of the day in the hottest months. The females lay two to four eggs, from one to three times, in the period from the middle of May until the end of June. They bury them in sunny places, so the incubation depends only on the ambient temperature and lasts between 90 to 125 days. The eggs hatch from the end of August to October. The incubation temperature also determines the sex of the newborns. In experiments, eggs that have been incubated at between 32 to 35 degrees produce females, but at lower temperatures between 25 and 30 degrees, the majority consists of males. They arrive at sexual maturity after eight to ten years.

The Mediterranean tortoise is essentially a herbivore. It has been proved that its diet is composed of more than fifty species of plants. But this is complemented with all sorts of animal remains that it is able to find, such as excrement, dead animals, snails…They also eat mushrooms. A diet with little variety, as usually occurs in animals in captivity, produces malformations in the shell.

The Mediterranean tortoise is very abundant in Menorca compared with other countries in which it lives. Here the density has been assessed at between 24 to 80 tortoises per hectare, whereas on the continent, the populations rarely come up to 10 (Bertolero, 2016). Their habitats are found all over the island in their preferred places: sunny open areas, such as cleared marinas; under bushes; in abandoned fields; in dune systems…

The principal dangers for tortoises are caused by humans: such as the destruction of habitat and by fires; or they are run over; or they are in accidents with agricultural machinery. They get attacked by dogs and rats. Natural predators in Menorca are practically non-existent. It has been found that hedgehogs can eat them at some point, and that the Egyptian vulture can eat their young. On the mainland, there are many problems with wild boars and foxes, badgers and other predators, all contributing to the risk of extinction of some populations. On the contrary, in Menorca, the survival rate is very high, above all once they reach adulthood.

For many years thousands were exported outside Menorca to be sold as pets. Now the Mediterranean tortoise is strictly protected by law. They cannot be kept in captivity. It is recommended that the gardens and fields in areas where there are tortoises have gaps and other ways for allowing the entrance and exit of the tortoises, so that the population can remain connected. When a tortoise is found in a dangerous situation, such as in the middle of the road, then we have to put it in a safe place right there and never take it with us thinking we are doing something good. Tortoises need to continue living in their community.

Class: Reptiles

Order: Chelonians

Family: Testudinidae

Species: Testudo hermanni subspecies hermanni

Popular names: Tortuga de terra mediterrània (Cat), tortuga mediterránea (Esp), tortue de Hermann (Fra), testuggine di Hermann (It), Hermann´s tortoise (Eng)

Distribution: Italian Peninsular, Sicily, Sardinia, Corsica, south of France, northeast of Spain, Mallorca and Menorca.

Size: up to 22 cms for the females, the males are much smaller.

Habitat: open sunny areas such as cleared marinas, under bushes, abandoned fields, dune systems…

Food: mainly herbivore complemented with animal waste.

Reproduction: oviparous, once to three times with 2 – 4 eggs, May to June. Eggs hatch from the end of August to October.

Conservation status: very good in Menorca. In danger of extinction on the Peninsula. Vulnerable as a whole of the species.

Legal protection: Protected at a European level by the Bern Convention and the Habitats Directive. Included in the CITES. Species in the Special Protection for RD 139/2011.

(Article published by Montse Bau and Tòfol Mascaró, biologists of GOB Menorca, in the Diari Menorca in the section Xoc on the 26 November 2018)