Macrovipera schweizeri

This website is dedicated to the endangered snake species Macrovipera schweizeri, commonly known as the Milos viper or the Cyclades blunt-nosed viper. While a notorious snake species in Greece, it is one of the most sought-after photography targets for herpetologists across Europe. The red phenotype is particularly attractive, not only because of its striking appearance but also due to its rarity. Despite its allure, the Milos viper is heavily targeted by reptile breeders and is often subject to illegal collection. The latest estimates suggest that around 100 individuals are illegally collected each year. Conservation of the species should be a priority for all. Here, we aim to provide as much up-to-date information on the species as possible, with the goal of sharing knowledge, raising awareness, and ultimately helping to protect it. Do not hesitate to contact us to share information or even to support our effort. 

Macrovipera schweizeri is endemic to only four West Cyclades islands in the Aegean Sea—Milos, Kimolos, Polyaigos, and Sifnos—giving it a very limited distribution range. With the exception of Milos, the other island populations are very small, with the Sifnos population being the smallest and most dispersed. Overall, the species’ population trend is listed as “Decreasing” by the IUCN. These four islands are among the most popular summer vacation destinations in Greece, which partly explains occasional human-viper encounters. While exceptionally rare, such encounters remain possible, and tourists should have access to basic information to avoid unnecessary panic and to passively contribute to conservation. The Milos viper is also heavily persecuted across its range, often killed on sight by locals, although this predisposition appears to be slowly reversing in recent years. More information on each island population can be found on the “Distribution” page. 

While Macrovipera schweizeri is the only viper species on these islands, other snakes do occur. For the safety of both the viper and any person who may come across it, proper identification is important. Fortunately, distinguishing it from other species can be done by following three simple steps outlined in the photographic key: 1) head shape, 2) body girth, and 3) abrupt tail narrowing. The Milos viper has a wide, triangular head due to the venom glands located behind the eyes, with males often showing a more pronounced shape than females. No other snake species on these islands shares this head structure. It also has a thicker, stockier body profile—except in juveniles, which are rarely seen. Unlike European and Greek viper species such as Vipera berus or Vipera ammodytes, the Milos viper is a Palearctic species with a generally longer total length, usually up to 90 cm, and in rare cases reaching 107 cm (recorded in Sifnos island). Finally, the tail is an important identification feature: after the body girth peaks and then narrows abruptly at the cloaca, the tail begins—often taking on a yellowish tone towards the tip, contrasting the rest of the body. 

The Milos viper occurs in two “phenotypes” or color variations: grey and ceramic-red. The grey phenotype is the most common, while the red form is rare and appears to be restricted solely to the western part of Milos. However, historical records indicate that red individuals were once found on Kimolos and Polyaigos prior to the 2000s, though recent confirmations are lacking despite intensive fieldwork. A persistent local belief holds that red vipers are more venomous than grey ones. Scientific studies do not support this belief and have shown no significant difference in venom composition or toxicity - with only negligent individual level variation. Another widespread belief on Milos is that three different viper species exist—one red, one grey and one black—each with its own local name. Common names include “Therio” (Θηρίο, meaning “beast”), “Kontonora” (“short-bodied”), and “Laspochendra” (Λασπόχεντρα, meaning “mud viper”). On Sifnos, the species is referred to as “ochendra.” Regardless of coloration, there is only one viper species across all four islands: the Milos viper (Macrovipera schweizeri), which comes in two main color variants and their shades, the red and the grey. Older male individuals can have a darker tone of grey that looks almost black from afar, visibly darker than the females; which are lightly colored. The same holds true for the red phenotype. A fully grown red colored male has a darker shade of red than a red female. The photographs below showcase the different shades of ceramic-red and grey between the two sexes.

The behavior and activity patterns of the Milos viper are particularly fascinating. In typical Macrovipera fashion, many individuals are defensive and quick to bite when threatened, but they are not inherently aggressive and do not “chase” humans, as is widely believed. Their secretive, cryptic nature makes them shy, and if startled, they usually hiss loudly, raise their head and posterior part of their body while retreating backwards looking to flee as soon as possible. They will only coil and stand their ground when surrounded from multiple directions. During fieldwork, we have also encountered very passive individuals, from which obtaining venom samples was very challenging as they refused to bite even when picked up. Seasonal activity changes are pronounced: spring marks the end of winter, triggering ovulation in females and spermatogenesis in males, and initiating the breeding season (late March to end of May). During this time, males stop feeding and focus entirely on finding mates—a period when most road fatalities occur, predominantly involving males. In summer, high temperatures make them crepuscular or completely nocturnal. Autumn cooling makes them diurnal again, though less active than in spring. In winter, most individuals remain hidden but do not enter deep brumation, instead cycling through periods of inactivity depending on weather conditions. These patterns are general trends, with individual variation likely. 

Even today, extended stays on these islands often bring new local myths and folklore to light through conversations with the residents. While many of these tales may seem implausible at first, they often contain kernels of truth. One such myth claims that eels come out of the sea on August nights to mate with vipers on the sand. Although biologically impossible, this story may have arisen from genuine observations. For example, during a survey on Polyaigos on one August full-moon night, we found a viper just a meter from the shoreline, partially buried in sand. Later that night, at low tide, we observed a small eel in a tidal pool (from which the shoreline had retreated) hunting a crab. A local witness seeing both events in quick succession could easily have woven them into a dramatic—but enduring—story. Such examples remind us that, even when inaccurate, local tales can contain noteworthy observations. It is therefore important not to confront locals directly but to approach and educate them thoughtfully. This is why we organize open presentations on all three islands every year—to help bridge this knowledge gap. 

Though rugged, drought-stricken, and inhospitable the biodiversity of these four West Cyclades islands is exceptional. Parts of the islands are included in the Natura 2000 protected network (shown in green on the following maps). This is something that surely assists in the protection and conservation of all biodiversity within these areas, however, as time goes by it becomes progressively easier for human activities to take place on them. One example is wind farms and geothermy. Polyaigos island is particularly vulnerable as it has been the target of numerous attempts to install large scale projects with wind turbines covering it from side to side. Such projects will have a direct effect to both the local and passerine avifauna of the islands and surely to the rest of the ecosystem. Macrovipera schweizeri also happens to be strictly protected by both national Presidential Decree No. 67, Government Gazette 23/A/30-1-81, "On the protection of wild flora and fauna and the establishment of a coordination and control procedure for research on them" and international legislation (Bern Convention Appendix II "Convention on the conservation of European wildlife and natural habitats", Council Directive 92/43/EEC of May 21 1992 "On the conservation of natural habitats and of wild flora and fauna". Government agencies should not be dismissive of such legal frameworks and local stakeholders should be made aware of their existence. 

In summary, the Milos viper faces numerous threats, from habitat disturbance and illegal collection to climate change, which brings prolonged droughts and higher temperatures. It is in the interest of all stakeholders from nature enthusiasts and herpetologists, to local citizens and tourists alike to support ongoing protection efforts. Through education, we can raise awareness about this remarkable species, which is undeserving of its notoriety. If you visit any of these islands and have information to share—such as sightings, myths, or evidence of illegal collection—please contact us. We are working towards establishing port checks that would give local authorities greater oversight and help prevent the illegal collection.