Data on the largest specimens of Testudo graeca ibera Pallas, 1814 found in Bulgaria with five new records

: Very large specimens of T. graeca ibera were found in Bulgaria, but mostly in the 20th century. Presently, such tortoises are almost absent in the country. Here we summarise data about the largest spur-thighed tortoises registered in Bulgaria and provide information about five new large-sized individuals. We also draw attention to the fact that large specimens can hardly be found in the country today and discuss some possible negative effects of the extinction of these specimens on the existing populations. The maximum straight carapace length of the largest T. graeca ibera ever found in Bulgaria was ≈ 389 mm, but the maximum straight carapace length of the newly measured tortoises was 298 mm. Considering the rarity of such tortoises in the country today, the genes that determine the potential to reach larger sizes may gradually disappear. Thus, the institutions responsible for the conservation of nature should pay attention to areas where the presence of large-sized individuals has been established. This might help preserve the natural genome of T. graeca ibera in the country and therefore the existence of large individuals.

The aim of the study was to (i) summarise the data about the largest tortoises found in Bulgaria and provide information about five new large specimens, (ii) draw attention to the fact that large tortoises are almost absent in the country today, and (iii) highlight the importance of such specimens for the existing populations.

Material and methods
To our knowledge, we examined all the available published sources of information about the sizes of T. graeca ibera in Bulgaria.The data on the five newly measured tortoises -four live individuals and one shell of a specimen killed by a shepherd -were gathered in two different ways.Two of the tortoises were found during field surveys of the population of T. graeca ibera in the northwestern foothills of the Pirin Mts, Rakitna Village.The surveys started in 2021, and the area has regularly been visited since then.The other two tortoises and the shell of the dead specimen were measured in May 2023 at the Tortoise Rehabilitation and Breeding Centre (hereafter the Centre).The Centre is located in Banya Village, Burgas District, in the eastern part of Eminska Mt, which comprises the easternmost part of the Stara Planina Mts (Ivanchev, 2007).
The tortoises were measured using a calliper and an electronic scale.The following parameters were measured: maximum straight carapace length (maximum SCL) -from the first marginal scutes to the rear supracaudal edge; midline straight carapace length (midline SCL) -from the front of nuchal scute to the rear supracaudal edge; mid-body carapace width (mid-body CW) -between the seventh marginal scutes; maximum carapace width (MCW)at the widest point; shell height (SH) -the maximum vertical height from plastron to carapace; weight (W).

Results
Information about 16 large specimens, five of which are mentioned for the first time, was summarised.The maximum SCL of the largest specimens found until now in the country varied between 237 and ≈ 389 mm and the weight of the heaviest tortoise was ≈ 6000 g (Table 1).The maximum SCL of the newly measured tortoises varied from 241 to 298 mm (Table 1).All four live tortoises as well as the dead specimen were females.The first large tortoise was captured and measured in Rakitna Village on 4 June 2022 at 11:30 a.m.(N41°50'43.6"E23°10'24.4";663 m a.s.l.).It was moving across a meadow next to a dirt road.The weather was calm and the cloud cover was about 80%.The air temperature was 23°C.The second large specimen was captured and measured on 22 August 2022 at 1:35 p.m. (N41°50'40.5"E23°09'44.7";712 m a.s.l.) (Fig. 1B).It was standing motionless under oak trees.The weather was calm and the cloud cover was about 70%.The air temperature was 25°C.These two specimens had a maximum SCL of 241 mm and 261 mm, respectively (Table 1).
One of the large tortoises that were measured at the Centre had been living in captivity in a garden near the city of Plovdiv for about 40 years.In 2009 the individual was translocated to the Centre and has lived there since then.It had a maximum SCL of 277 mm (Table 1).The other large tortoise from the Centre had initially been a part of a local population that was under threat of extirpation due to construction works.Therefore, the specimen was saved and translocated to the Centre in 2007.It had a maximum SCL of 278 mm (Table 1).The shell belonged to a very large tortoise that was killed by a local shepherd in the eastern part of Eminska Mt in the 1980s (Fig. 1A).Presently, the shell is in the Centre and can be seen by the people visiting the place.It had the largest size of all the five specimensa maximum SCL of 298 mm, which placed it seventh among the largest specimens ever registered in the country (Table 1).

Discussion
Extremely large specimens of T. graeca ibera have been observed in Bulgaria since the end of the 19th century (Irechek, 1899;Beshkov, 1984Beshkov, , 1993Beshkov, , 1997;;Undjian, 2000;Stojanov et al., 2011).Most of the observations were made during the 20th century (Table 1).At present, such tortoises can hardly be found in the country (Türkozan et al., 2023).In fact, the size of the carapace of most tortoises in Bulgaria today varies from 150 to 250 mm (Petrov et al., 2004;Biserkov et al., 2007;Tzankov & Popgeorgiev, 2011;Türkozan et al., 2023).Türkozan et al. (2023) mentioned that the largest T. graeca ibera measured in Bulgaria in recent years had a midline SCL of 258 mm (n = 1142).Most of the larger individuals across the range of the subspecies are females as they usually reach larger sizes than males (Hailey et al., 1988;Willemsen & Hailey, 2003;Buică & Cogălniceanu, 2013;Arslan et al., 2021;Türkozan et al., 2023).This was also confirmed by our results since all of the five specimens that we measured were females.
Large specimens of T. graeca ibera were also found in Greece (Buttle, 1989;Cattaneo, 2001;Willemsen & Hailey, 2003;Wilson & Grillitsch, 2009), Turkey (Türkozan et al., 2005(Türkozan et al., , 2010; Akveran & Ayas, 2019), Romania (Cogălniceanu et al., 2010), and Russia (Krasnodar) (Leontyeva et al., 2001).Nevertheless, as in Bulgaria, such records tend to be very rare (Willemsen & Hailey, 2003;Cogălniceanu et al., 2010;Türkozan et al., 2010).In Bulgaria, in particular, the reason for the almost complete absence of contemporary data on large specimens may be attributed to the different threats to local populations throughout the country.According to Beshkov (1984Beshkov ( , 1993)), the most serious threat to T. graeca ibera in Bulgaria is the destruction and degradation of natural habitats.This threat affects all the age groups in populations equally.As the second most significant threat Beshkov (1984Beshkov ( , 1993) ) mentioned the illegal collection of specimens for various purposes.For example, for consumption, use of blood and eggs to "cure" serious diseases, and internal and external trade.
When collectors search for tortoises, they focus mainly on larger individuals as they are easier to find and bring more benefits than smaller ones (Beshkov, 1984(Beshkov, , 1993)).This illegal practice is known to have occurred since the end of the 19th century (Hristovitsch, 1892).Thus, it is not unusual that very large tortoises are almost absent in the country today.We hypothesise that when these tortoises disappear, the genes that determine the potential to reach larger sizes will disappear as well.It can therefore be suggested that the maximum size of T. graeca ibera in the country will gradually become smaller.
For this reason, the institutions responsible for the conservation of nature should pay attention to the territories in which the presence of large-sized individuals has been established.This is particularly important when these institutions: plan to designate new protected areas; prepare and implement a new action plan for conserving the species; need to change the current action plan, i.e. to carry out adaptive management, etc.This might help preserve the natural genome of T. graeca ibera in the country.

Fig. 1 .
Fig. 1.The shell of the tortoise killed by a shepherd in the 1980s (on the left) and one of the specimens found in Rakitna Village (on the right).

Table 1 .
Summary of the sizes and some other data of the largest specimens of T. graeca ibera found in Bulgaria.For abbreviations see Material and methods; f -female, m -male; n/a -not available.