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An excursion into the natural habitats of the Dalmatian tortoise


Testudo hermanni hercegovinensis,
WERNER 1899

 

As long ago as in 1899, WERNER described as Testudo graeca var. hercegovinensis a tortoise that occurred at Trebinje, Bosnia, and closely resembled Hermann's tortoise. The Finnish systematist PERÄLÄ resurrected this name as a separate species, "Testudo hercegovinensis WERNER, 1899" in 2002.

Owing to the relatively minor points of distinction that are not even always present, this species status cannot be maintained, however. The Dalmatian tortoise must rather be viewed, as was properly suggested in a popular-scientific publication by BLANCK & ESSER (2003) already, as a subspecies of Hermann's tortoise, i.e., as Testudo hermanni hercegovinensis.

In another systematic work, PERÄLÄ reevaluated the tortoises of the Mediterranean as forming a separate genus, Eurotestudo, comprising the species Eurotestudo hermanni, Eurotestudo boettgeri and Eurotestudo hercegovinensis. Whether this proposal will find general acceptance remains yet to be seen. The phylogenetic species concept favoured by PERÄLÄ has as yet not managed to replace the principles of biological systematics.

For us tortoise keepers the exact systematic positioning of our tortoises is of secondary importance. It is irrelevant for the day-to-day husbandry whether you follow a phylogenetic species concept and accept a species, or a biological species concept and think of a tortoise as a subspecies. All that counts is the realization that the eastern Hermann's tortoises living in our care might include specimens that represent a different kind.

 

In order to obtain a first-hand overview of the morphology, natural history, and especially the distribution range of this "new" tortoise, my son Manuel and I visited the Adriatic coast of former Yugoslavia during the month of May both in 2005 and 2006. There, we literally scoured the coastal strip from northern Istria south to the Albanian border region in search of tortoises.

When we visited Croatia the last time, the local tortoises were still generally referred to as Testudo hermanni boettgeri.

 

Raum Zadar

The Dalmatian tortoise resembles the western form as to its body shape, pattern and size, and the eastern form with regard to its colouration. Other than that it may exhibit all the traits of either of the other two forms.

The dorsal shell is usually deeply coloured, shows a contrasting pattern, and is highly domed. The ground colour varies with the locality and ranges from pale ochre (southern and island populations) to dark olive (Istria). The "keyhole" marking on the 5th vertebral scute is more or less distinct and relatively often present, as is the yellow subocular spot. Either trait may also be entirely wanting, however.

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The occiput is always yellowish olive to olive in colour. The colouration of the head, limbs, and skin varies with the origin of a specimen from lighter in the south to darker in the north. It is generally lighter than that of the eastern subspecies that lives in adjacent Montenegro.

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The ventral shell is yellowish olive and sports two longitudinal black streaks much like in the western and some populations of the eastern subspecies. These streaks are, however, always clearly separated in the centre in a Dalmatian tortoise, altogether substantially narrower, and often fragmented or obscure.

Like in the western form, the gular scutes are almost always, and the anal scutes sometimes, free of spots or bear spots only on one side. The spots on the humerals and, if present, on the subcaudals are principally clearly separated from the spots of the pectorals and femorals, respectively.

The ratio of the central suture of the pectorals to the suture separating the femorals is too variable to be useful for identifying this tortoise.

 

Males reach adult sizes of about 14 to 16 cm in carapace length and weights between 600 and 800 g. Females grow to sizes between 15.5 and 17.5 cm and weigh between 850 and 1,100 g then. Specimens of the northern populations are generally larger than those from the south also in the Dalmatian tortoise.

The aim of our journey was to examine as many local populations as possible and compare our findings. We did not attempt to locate large numbers of individuals, but limited ourselves to examining just four animals at each locality. For this reason we stayed only for a short time in one place and moved on quickly if no signs could be found that suggested that tortoises might live here.

Even though we began spot-checking sites where our experiences indicated that they might be suitable tortoise habitats right from the Slowenian border, we were not really surprised to find the first specimens only in the more southern parts of Istria.

From a geological point of view, Istria forms suitable tortoise habitats only in this part, with the northern regions consisting of grey sandstone and marl. From the south, the Istrian plate rises as a Cretaceous limestone sheet to heights of up to 450 m, and together with its Mediterranean vegetation, formed an ideal tortoise habitat at least during earlier times. Today, Istria is heavily fragmented by human settlements and dominated by tourism and agriculture.

Even though it might be difficult to imagine in the face of the remainder of the distribution range, the tortoises occurring in Istria are still referred to Testudo hermanni boettgeri while the range of the Dalmatian tortoise is said to begin only south of Zadar.

We were therefore rather puzzled when the first tortoise we encountered had inguinal scutes on either side, which has so far been regarded as the main distinguishing character. These are small, triangular scutes in the hip, or rather groin, area that cover the thigh cavity between the ventral and marginal scutes and are usually present in the two other subspecies.

The limbs and head of this 16.0 cm-long male were relatively dark in colour, with just a few olive-coloured scales. The dark yellowish olive overall appearance of his carapace suggested it to be a Dalmatian tortoise, however.

The next specimen then made things clearer. It was a male with lower marginal scutes that extended inward into the flexure of the groin, and it had no inguinal scutes on either side.

Two more specimens, a female of 13 cm in length and an adult male, likewise lacked inguinal scutes. All four tortoises did not differ from each other in their general appearance, and it was clear that these were Dalmatian tortoises.

Zadar

To the south, the region of Istria is eventually replaced by the Croatian coastal strip, a very narrow to at maximum 15 km-wide belt of some 1,800 km in length that is partly immediately bordered by mountains that rise to between 1,200 and nearly 1,800 metres above sea level. These mountain ranges separate the coastal region with its Mediterranean climate from the continental climatic zones of the hinterland. This is the reason why tortoises are limited to this coastal strip in Croatia.

A distinct temperature gradient runs from Istria in the north to the adjacent coastal region towards the south, which was quite notable at this time of the year and especially at night. We experienced the first summery warm night on the island of Pag.

Kroatische Steinlandschaft

Local farmers have therefore resorted a long time ago to laboriously collect rocks by hand and use them to demarcate checkerboard-like sections, which are then filled with soil to permit the growing of at least some olive trees, grapes or some vegetables. Left-over rocks are piled up to walls or heaps of several metres in height.

These areas have for centuries been stripped of tortoises, even though these prefer rocky soils.

While actually white in colour, the limestone rocks and boulders have turned grey under the scorching sun. Some areas, on the offshore island in particular, are now reminiscent of the surface of the moon.

 

huegel

Large parts of these chains of hills, the plains in between, and even former agricultural fields are still peppered with land mines from the last civil war. Thus untouched for the past fifteen years, local tortoise populations have had a chance to recover nicely. And indeed, our searches along the margins around these mined areas revealed numerous specimens of various age classes within a relatively short time, suggesting that local populations have stabilised once more.

For us tortoise enthusiasts this is not really a reason to celebrate, though. These areas will surely be swept for mines at one stage or another, and because the rugged land permits the use of motorized mine sweepers only to a very limited extent, farmers help themselves by setting it alight and have the fire trigger the concealed mines.

This then also means the end for the vast majority of tortoises living there. There are usually only a few survivors of these carpet fires, and often they get away with horrendous burn wounds.

6

The locality was a south-facing, very rocky, partly very steep slope with an overgrowth of very dense brush and scattered clearings that eventually turned into a fir forest. The bushy vegetation consisted mainly of prickly juniper, intermixed with individuals of Phoenician juniper. The clearings and even the space between and below the bushes were blanketed with a multitude of flowering, juicy feeder plants. When I read up in a nature guide that the tar produced from the wood of prickly juniper would be good for the treatment of skin problems, I found this to be a major irony. Being extremely prickly, this juniper was living up fully to its name and causing skin problems all over our arms and legs rather than relieving them.

IMG09954

 

Just like everywhere else in the Mediterranean region the forests that once covered the Croatian coast were felled to build ships during earlier times. On the forefront were Venetian ship builders who between the 10th and 18th centuries established large shipyards on the offshore islands that in turn literally devoured the existing primary forests. Strong winds, the Bora in particular, then eroded the topsoil and left behind an inhospitable rocky desert landscape. In some places, even the smallest remains of humus have since been blown away, and the persisting vegetation is limited to a few very hardy shrubs and herbs that are able to anchor themselves between the rocks. Large areas are now reduced to rubble fields in which even goats and sheep cannot find anything to graze on.

 

However, the coastal strip also has to offer gently undulating chains of hills that are overgrown with more or less dense vegetation. It is here that relatively original tortoise habitats can still be found. Even though these areas are utilized only as pastures, if at all, population densities of tortoises are relatively low when compared to other countries situated farther to the south, such as Montenegro, Greece, or islands like Sardinia. Before the big rush on the once forest-rich Mediterranean vegetation, Dalmatian tortoises have surely existed in suitable habitats right from Istria through to the north of Montenegro.

 

Areas with intensified agriculture are largely stripped of tortoises these days. An old farmer's wife told us that no tortoises had been seen in her fields for many years, and she was obviously very happy about it. The tortoises that have so far managed to continue their existence in other agriculturally used areas have - as I have pointed out and discussed in my books - no chance of survival anyway.

At another farm that bordered an area of mined, dense maquis, the farmer told us that the numbers of tortoises in his fields had increased so much that they had begun to become a pest once more. A short while later his wife brought us a semiadult female tortoise and insisted that we take her; we did and released her into the maquis.

Farmers still largely regard tortoises as vermin and competitors for the grazing reserved for their goats and sheep. As a consequence they are pursued and beaten to death on sight.

Our survey indicates that the distribution range of the Dalmatian tortoise extends from southern Istria to the Neretva River, including its estuary and upriver valley to the surroundings of Mostar. A sympatric occurrence with Testudo hermanni boettgeri and even mixed populations can be found in the about 180 kilometres-long adjacent part of the coast that stretches to the vicinity of Budva in Montenegro.

Population densities increase so drastically after entering Montenegran territory that we saw a total of six tortoises crossing roads within a few days in May of 2006; two more specimens were spotted lying dead next to the road.

ueberfahrene

South of Budva, we found only tortoises that were referable to the eastern subspecies mainly on the basis of their size and their having distinctly formed inguinals, but also due to their general appearance. Very many of the T. h. boettgeri found in Montenegro were very dark. This may seem surprising at first, but is easily explained by these being T. h. boettgeri that live on the northern fringes of their distribution range.

Our excursion in May of 2005 took us from Istria to the mouth of the Neretva River. We searched altogether twenty possible tortoise habitats, and found a total of thirty-three tortoises in nine of these. We continued our survey in May of 2006, searching twenty-three potential habitats from the Neretva south to and including the valley of the Albanian border. There, we found, measured, weighed, and photographed a total of ninety-two tortoises at nineteen localities. Our two excursions thus add up to a total of 125 tortoises at twenty-eight localities. Eleven of these records were made from within the distribution range north of the Neretva River, ten between the Neretva and Budva, and seven between Budva and the Albanian border. Forty-two specimens of these were identified as Dalmatian tortoises.

The layman will find it hard at times to distinguish a Dalmatian tortoise from the other two subspecies. The inguinal scutes do not always provide clear answers, simply because they are not uncommonly present on one or either side in the Dalmatian tortoise as well. Just as well, I have found specimens representing the western or the eastern subspecies that lacked inguinal scutes. If these scutes are wanting, however, you may want to check further and see if this is a Dalmatian tortoise.

Our field studies of these forty-two Dalmatian tortoises from eleven localities revealed that 60% of the animals found lacked inguinal scutes on both sides, while 14% had them on one side, and 26% even had them on both sides! Amongst these specimens, 65% exhibited a more or less distinct keyhole marking on the 5th vertebral scute.

This illustrates once more that distinguishing between the subspecies of Hermann's tortoise is not always easy, and the inexperienced observer will only arrive at a conclusion if the classical characteristics are clearly present in a specimen.

© Manuel Wegehaupt