Macedonian Ecological Society herpetology group

Skopje, Macedonia

Macedonian Ecological Society herpetology group

Skopje, Macedonia
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Ajtic R.,Institute for Nature Conservation of Serbia | Tomovic L.,University of Belgrade | Sterijovski B.,Macedonian Ecological Society herpetology group | Crnobrnja-Isailovic J.,University of Belgrade | And 14 more authors.
Zoologischer Anzeiger | Year: 2013

A population of dice snakes (Natrix tessellata) monitored since 2008 in a small island (18. ha, 850. m a.s.l., FYR of Macedonia) revealed unforeseen patterns for snakes living in temperate climates. More than 5000 individuals have been marked and the density is one of the highest ever recorded (>500 resident snakes per hectare). Reproductive and mortality rates are elevated, suggesting a high population turnover. These traits evoke a tropical rather than a temperate-climate ophidian demographic system. The population is highly polymorphic, three colour morphs (dotted, grey, and black) are observed in both sexes and each morph is represented by large numbers of individuals. This polymorphism pattern was not previously documented in snakes. Data obtained for other life history traits (e.g. body size, size at maturity, clutch size, diet, predation) markedly diverged in comparison to available information. Overall, our results reinforce the notion that the strong inter-population variability (often mediated by phenotypic plasticity) of snakes should be taken into account over large geographic scales; otherwise attempts to derive general patterns may well be strongly biased. © 2012 Elsevier GmbH.

Golubovic A.,University of Belgrade | Andjelkovic M.,Sinisa Stankovic Institute for Biological Research | Arsovski D.,Macedonian Ecological Society Herpetology group | Vujovic A.,University of Montenegro | And 3 more authors.
Acta Ethologica | Year: 2013

Dense vegetation cover undoubtedly offers certain advantages for small and slow-moving animals, but its disadvantages concerning some aspects of spatial ecology (e.g. movements) were neglected in previous studies. Tortoises could get stuck in vegetation by protuberant part of the shell and thus succumb to overheating, dehydration or predators. To examine how vegetation cover shapes behavioural responses of 'trapped' tortoises, we tested adults of six populations from habitats with contrasting vegetation cover. The tortoises were fitted with a non-stretchable rope, representing a piece of vegetation, stuck on the protruding front part of the plastron. Results suggested the existence of two distinct releasing techniques. First, and only successful in this study, is frequent changing of the movement direction, with a minimal pulling force, until the obstacle detached. The other involved the maximal pulling force aimed at ripping out the constraint. Tortoises from shrub habitats had more releasing success, used less pulling force and needed shorter time period to release, contrary to tortoises from herbaceous habitats. Although sexes showed similar releasing success, females obtained lower number of direction changes and higher yanking force compared to males, suggesting slightly different liberating strategies between the sexes. For immobilized tortoises without suitable shelter from overheating and dehydration, appropriate behavioural response could be vital, especially during drought years, due to increased physiological stresses. Variability of behavioural patterns among tortoise populations, described in this study, could have an adaptive significance. © 2013 Springer-Verlag Berlin Heidelberg and ISPA.

Sterijovski B.,Macedonian Ecological Society herpetology group | Ajtic R.,Institute for Nature Conservation of Serbia | Tomovic L.,University of Belgrade | Bonnet X.,University of La Rochelle
Herpetological Conservation and Biology | Year: 2014

Most conservation efforts are channeled toward highly endangered species. However, snake populations decline rapidly worldwide, and many species that are currently classified as not threatened (e.g. LC - least concern, IUCN Red List) may well rapidly fall into the threatened categories. Yet, common species attract little attention. The principle, that it is more efficient to prevent disasters than to cure effects, is not taken into account. Dice Snakes (Natrix tessellata) offer a typical example of this situation. This species is one of the most widespread and polymorphic snake of the planet. Very large populations occur in the Balkans. On Golem Grad Island (the single island of FYR of Macedonia), a remarkable population of Dice Snakes suffers from recent assaults. Thousands of snakes are killed every year in the nets set by poachers, notably gravid females, raising population viability concerns. Protecting Dice Snakes, other reptiles (e.g. tortoises, vipers, and lizards) and the whole eco-system of Golem Grad Island would require moderate efforts: application of official rules, summer attendance, delivery of official permits to local people (including fishermen), and controlling tourism. In this paper, we addressed a central issue: does illegal fishing represent a potential threat to Dice Snakes? Our data suggest that recent increase of illegal fishing correlates with population decline. © 2014. Bogoljub Sterijovski. All rights reserved.

Golubovic A.,University of Belgrade | Arsovski D.,Macedonian Ecological Society Herpetology Group | Ajtic R.,Institute for Nature Conservation of Serbia | Tomovic L.,University of Belgrade | And 2 more authors.
Biological Journal of the Linnean Society | Year: 2013

Despite exhibiting low velocity and limited agility, many tortoises undertake large scale movements and must overcome various obstacles, notably in populations living in hilly or rocky habitats. Although crucial, studies exploring how tortoises move in complex and irregular environments are scarce. In this context, we examined an important behavioural trait: how tortoises (Testudo hermanni) deal with step-like obstacles. In their natural habitat, individuals were positioned in a challenging situation: they were placed on a bench approximately 50cm high, and were observed over a 10-min period. We compared the behaviour of the tortoises (taking a risk to 'jump' or waiting) from two populations living in contrasted habitats: flat versus rugged (crisscrossed by cliffs and rocky steps). Individuals from the flat habitat were reluctant to jump, whereas most tortoises from the rugged habitat jumped. Immature tortoises were less willing to jump compared to larger and more experienced adults. These results suggest that challenging habitats increase boldness. In addition to fundamental findings, these results may have conservation value and assist in improving translocation strategies for endangered tortoise populations. © 2013 The Linnean Society of London.

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