Official website of the Municipality of Alonissos
Ecosystem - Photo 1

The Ecosystem of Alonissos

Climate & Soil

Climate type

The Mediterranean climate is characterized by wet winters and dry summers. The average annual temperature is 17°C and the average rainfall is 515 mm.

Soil type

Limestone rocks, caves and steep rocky slopes rising above the sea form the primary habitat of the Mediterranean monk seal. Various types of soil are also encountered here.

Flora & Fauna

Geographical isolation, particular soil morphology, limited exploitation of natural resources and intact landscape make up a beautiful natural habitat and reserve for many endangered species of the terrestrial or marine flora and fauna.


Sporades Islands are spread with Mediterranean coniferous forests (e.g. pine forests) and macchia vegetation composed primarily of bushes and shrubs such as arbutuses, mastics, phillyreas, heathers, buckthorns and kermes oaks. Evergreen trees and shrubs such as maple trees, wild olive trees and Phoenician junipers are also common in this area; a rare tree named Amelanchier chelmea is common here, too. There is also a wide variety of phrygana. The chasmophytic vegetation including several indigenous plants (Campanula reiseri, Campanula rechingeri, Linum gyaricum, Areanaria phitosiana, etc.) is also very interesting. The underwater seagrass beds of Posidonia oceanicae play an important role in the development of many organisms, as well as the retention and recycling of various substances of the marine environment. These seagrass beds are large, and are preserved in excellent condition.


The area of the Marine Park is also a precious reserve for many fish species (about 300), birds (over 80 species), reptiles and mammals. The Mediterranean monk seal (Monachus monachus), the red coral (Coralium rubrum), Eleonora's falcon (Falco eleonorae), Audouin's gull (Larus audouinii), the Common shag (Phalacrocorax aristotelis) and the wild goat of Gioura (Capra aegagrus) are some of the most typical rare species living in this area. Bonelli’s eagles (Hieraetus fasciatus), Great cormorants (Phalacrocorax carbo), Yellow-legged gulls (Larus cacchinans) and swifts (Apus apus & Apus melba) are some of the most common birds also found in the Marine Park. Various species of the Sylviidae family are also encountered here, such as the Sardinian warbler (Sylvia melanocephala) and the Blackcap (Silvia articapilla). Marine fauna is also diverse, including numerous benthic and ocean species. Dolphins and some whale species also live within the area of the Marine Park. Common dolphins (Delphinus delphis), striped dolphins (Stenella coeruleoalba), bottlenose dolphins (Tursiops truncatua), sperm whales (Physeter macrocephalus) and cuvier’s beaked whales (Ziphius cavirostris) are the most common species of dolphins and whales encountered here.

Monachus Monachus

The scientific name of the monk seal is "Monachus monachus". It derives from the Greek word "monachus," which means "monk-like, solitary." The "monk" description may refer to either the dark colored "hood" on its head or its tendency to live in large groups avoiding contact with humans. The figure of the monk seal was represented on ancient Greek coins, and references to this species are also found in Homer’s epic poems.

Monk seals used to live throughout the Mediterranean Sea; from the eastern Atlantic Ocean, Morocco and Mauritania to the Black Sea. Under the influence of various factors, the population of monk seals has significantly decreased in numbers, and their natural reserves have been shrinking in size over time. In the last twenty years, the monk seal has become extinct in over ten countries and therefore, it is nowadays considered to be one of the most endangered mammals in Europe.

At some 400–500 remaining monk seals, scientists confirm that 2/3 of their total population live in Greece. The Mediterranean monk seal is one of the largest species of seals in the world; they grow up to 2-3m and weigh an average of 250 kg. It takes 3-4 years for females to reach reproductive maturity and a little longer for males. They are believed to live up to 35-40 years.

Their skin is covered by short sleek dark (grey or brown) hair, and on their bellies there is a brightly coloured stripe. Baby monk seals are about one meter long and weigh around 15–20 kg. Their skin is covered by long black hair and they all have a white spot on their bellies. There are no distinct differences between male and female monk seals.

Pregnancy lasts for 10 to 11 months; births take place mostly from May to November and peak from September to October. Lactation period lasts about 4 to 8 weeks. Given the length of the pregnancy and lactation period, monk seals usually give birth every two years. They only give birth to one pup at a time. Because of human presence and intervention, pregnant Mediterranean monk seals nowadays typically use inaccessible caves to give birth, though historical descriptions indicate that they used to prefer open beaches. Although seal pups cannot swim, they grow to be excellent swimmers within a few weeks’ time.

Mediterranean monk seals feed on all fish and molluscs available in their natural habitat. It is estimated that the adult seals’ daily food consumption averages 5-10% of their body weight. Monk seals prey on fish caught in fishing-nets and often follow fishing boats or migratory fish.

Greatest threats to the monk seal

The Mediterranean monk seal is mostly threatened by:

  • Humans, as it has been hunted commercially for its oil and skin.

Nowadays, fishermen occasionally consider it a pest due to the damage seals cause to the fishing nets when preying on fish caught in them. Such behaviour is due to limited marine fish resources and overfishing.

  • Shrinkage of nature reserves.

According to historical descriptions, monk seals used to prefer sandy beaches or wide caves to give birth. Due to human intervention and the exploitation of natural resources (tourism, crafts, ports, roads, etc) monk seals were forced to give birth in caves inappropriate for this purpose. Mortality rates among monk seal pups born in such conditions are relatively high, for baby monk seals are weak swimmers in the early stages of their life. As a result, they are prone to injuring or drowning due to high surf or storm surge.

  • Entanglement in fishing nets.

Entanglement in fishing nets is one of the greatest threats to seals and other marine species (e.g. Caretta caretta) throughout the Mediterranean Sea. Unfortunately, fixed and other types of nets lead to high mortality levels for monk seals.