Differences in skull morphology between Mediterranean Monk Seals from the Atlantic and the western Mediterranean, including differences in the occurrence of dental aberrations, have been suggested based on a limited sample size (van Bree 1979). Examination of 24 DNA microsatellite loci in eastern Mediterranean and western Sahara (Atlantic) Monk Seals showed that the first group had 14 unique alleles and the second had 18; highly significant differences in allele frequencies between the two subpopulations were found for 14 out of 17 loci (Pastor et al. 2007). All this suggests substantial genetic differentiation between subpopulations, but to date no separation of this species has been suggested taxonomically.

Due to its very small, fragmented population structure and declining numbers, the Mediterranean Monk Seal is assessed at the Mediterranean regional level as Critically Endangered (CR).

Mediterranean monk seals were once widely and continuously distributed in the Mediterranean, Black and adjacent seas, and in the North Atlantic waters from Morocco to Cap Blanc, including the Canary Islands, Madeira Islands and the Azores (Aguilar 1999). A few individuals, possibly vagrants, have been recorded in Senegal, the Gambia and the Cape Verde Islands in the southern end of the distribution range, as well as in Portugal and Atlantic France in the northern end (Ronald and Healey 1982, Israels 1992, Aguilar 1999).

Today the distribution is widespread, but fragmented into an unknown but probably relatively large number of very small breeding subpopulations. In the Mediterranean, the stronghold for the species is on islands in the Ionian and Aegean Seas, and along the coasts of Greece and western Turkey. The two surviving colonies in the south-eastern North Atlantic are at Cabo Blanco (also known as Cap Blanc or Ras Nouadhibou) on the border of Mauritania and Western Sahara, and the small colony at the Desertas Islands in the Madeira Islands group (Aguilar 1999, Gilmartin and Forcada 2002). Many locations where seals are infrequently or regularly seen, or were seen in the recent or historic past, are reported in the literature and catalogued in reviews and status updates, see Sergeant et al. (1978), Israels (1992) and UNEP/MAP (2005).

The Mediterranean monk seal is the most endangered pinniped species in the world, with an estimated total population size of 350-450 animals, with 250-300 in the eastern Mediterranean within the largest subpopulation, of which about 150-200 are in Greece and about 100 in Turkey (Güçlüsoy 2004). Approximately 130 seals currently inhabit the Cabo Blanco area (Western Sahara-Mauritania); in the early 1990s this subpopulation was estimated at about 317 seals but a mass mortality event in 1996 reduced numbers to nearly a third (Forcada et al. 1999, Aguilar 1999). Approximately 20-23 inhabit the Desertas Island, Madeira (Pires and Neves 2001, UNEP/MAP 2005). The subpopulation at Cabo Blanco is the only large extant aggregation of the species and is unique in that it still preserves the structure of a colony (Aguilar 1999); the other subpopulations are composed of loose groups of extremely reduced size (usually less than 5 individuals). A recent review of monk seal occurrences reported from 1999-2005 suggests that at all other locations and countries about 14 additional seals can be accounted for (10 of the 14 in Algeria, plus an unspecified number of vagrants (UNEP/MAP, 2005)).

Mediterranean monk seals are medium-sized phocids that reach 2.3-2.8 m in length (Gilmartin and Forcada 2002). Based on a large number of seals examined after a mass mortality at Cabo Blanco, average adult lengths were estimated at 2.42 m in females and 2.6 m in males. Pups up to 3 months of age averaged 1.08 m with a range of 0.74-1.38 m (Samaranch and Gonzalez 2000). In the Mediterranean, a study on a limited sample size produced somewhat larger lengths for adult females (2.65 m) than for adult males (2.41 m); newborn pups averaged about 99 cm (Boulva 1979). Adults weigh from 240-300 kg, and newborns 15-26 kg (Boulva 1979, Gilmartin and Forcada 2002), with records of a male reaching 400 kg and a pregnant female reaching 302 kg (Sergeant et al. 1978).

In islands or mainland areas devoid of terrestrial predators, Mediterranean monk seals once hauled out on open beaches; it is unclear whether they ever used locations along the northern African coast, where large predators, like lions or hyenas, occurred. Today, they use caves with sea entrances for hauling out and pupping throughout their range, although adults, particularly males, may also sporadically haulout on open beaches (Gilmartin and Forcada 2002). Sea caves used by seals almost always have submerged entrances to avoid entrance by terrestrial predators, but the use of particular caves probably changes periodically if their structure is altered as a consequence of variations in the shape of the inside beach or of rock slides, as has been seen to occur at Cabo Blanco (González et al. 1997). Maximum counts at one cave in the Cabo Blanco colony had up to 89 seals hauled out at one time, and never less than five animals present (Gonzalez et al. 1997). In a study that covered 250 km of coastline inhabited by monk seals in the Cilician Basin region of southern Turkey, 282 caves were searched. Of these, 39 showed evidence of monk seals, including three that were used for pupping and 16 that were actively being used at the time of the survey. Use of these caves increased in October coincident with the autumn pupping season in Turkey (Gucu et al. 2004). The maximum number of seals from this small Turkish subpopulation found in a cave in at one time was three (Gucu et al. 2004). The numbers in caves are highest at low and rising tides.

Pups are born all year-round, but in the Cap Blanc colony most are born from summer to early winter, with a small peak of births in October; 84% of the births took place in only two caves separated by 1.1 km (Gazo et al. 1999, Pastor and Aguilar 2003). In Turkey's Cilician Basin, 11 newborns observed, 10 of which were born between August and November, and another 6 documented births in Turkey fall in this same time period. While pups may be born throughout the year, this definition may mask more restricted birthing periods on a smaller geographic scale.

Mediterranean monk seal pups moult an average 64 days after birth in the case of females and an average 82 days in the case of males; the moult occurs partly in the water and takes an average of 15 days to be completed (Badosa et al. 2006). Pups begin to catch fish toward the end of their nursing period (Pastor and Aguilar 2003). Pups are weaned when they are around 4 months old, with up to 5 months reported (Pastor and Aguilar 2003, Aguilar et al. 2007). Fostering and milk stealing are common patterns. At the Cabo Blanco colony, in 26.6% of the suckling episodes observed in mother-pup pairs of known identity, pups suckled from females other than their mothers. Some females nursed more than one pup, at least occasionally, and in some cases a pup was fostered long-term by an alien female (Aguilar et al. 2007). Pups enter the water and begin diving during their first week and from that point onwards spend 55-74% of their time at sea. Three pups tagged with time depth recorders spent more time at sea and diving at night than during the day; most dives were to the bottom for relatively long periods, probably indicating foraging. The mean depth of dive was 11.6 m and its mean length was 149 seconds (Gazo et al. 2006).

Females caring for pups will go off to feed for up to 17 hours, with an average time of 9 hours (Gazo and Aguilar 2005). Female Mediterranean monk seals probably become sexually mature at three to four years of age. One female at Cabo Blanco became pregnant at 2.5 years and gave birth at 3.7 years, the youngest age known for this species (Gazo et al. 2000b). In males, the process of developing the mature pelage pattern of bulls is gradual; it involves at least two annual moults and can be completed by the age of 4 years (Badosa et al. 2006). Females can give birth in successive years. Although birthing is not seasonal, individual females have been documented to give birth close to the same time in successive years, within a 15 day span (Pastor and Aguilar 2003). The annual reproductive rate in Mediterranean monk seals is extremely low at 0.25-0.43 pups to each sexually mature female, both in the Cabo Blanco colony and the Turkey coast (Gazo et al. 1999, Gucu et al. 2004).

Pup survival is low; just under 50% survive their first two months to the onset of their moult, and most mortalities occurred in the first two weeks. Survival of pups born from September to January is 29%. This very low survival rate is associated with mortality caused by severe storms, and high swells and tides, but impoverished genetic variability and inbreeding may also be involved. Pups born during the rest of the year had a survival rate of 71% (Gazo, et al. 2000a). Few pups are successfully weaned in the winter. Adult females moult an average of 134 days after parturition, and sometimes begin the moult prior weaning their pup (Pastor and Aguilar 2003).

Little is known about adult diving. The maximum depth and duration of diving for one lactating female was 78 m and 15 minutes, respectively (Gazo and Aguilar 2005). Neves (1998) observed two types of diving in shallow near shore waters, which were thought to be associated with spot feeding and transit feeding. When spot feeding, seals dove as though headed into a current for 8-12 minutes, surfaced at about the same location, and usually repeated this pattern for approximately 3 hours. Transit feeding dives lasted 5-7 minutes, during which the seal moved continuously along a shoreline apparently foraging.

Mediterranean monk seals take a wide variety of prey primarily from shallow water habitats (Sergeant et al. 1978, Kenyon 1981). In the eastern Mediterranean, they have been reported to take fish such as striped red mullet (Mullus surmuletus), seabream (Dentex spp.), bogue (Boops boops), flathead mullet (Mugil cephalus), octopus (Octopus spp.) (Sergeant et al. 1978), and even loggerhead sea turtles (Caretta caretta) (Margaritoulis et al. 1996). Examination of two seals from the Aegean Sea yielded five species of prey; by weight, 94% of the contents were cephalopods including musky octopus (Eledone moschata) and globose octopus (Bathypolypus sponsalis) (Salman et at., 2001). In the Atlantic, at the Desertas Islands off Madeira, visual observations of monk seals with prey at the surface included seals eating golden-grey mullet (Liza aurata), parrot fish (Sparisoma cretense), barred hogfish (Bodianus scrofa), salema (Sarpa salpa), cuttlefish (Sepia officinalis) and crabs (Pachygrapsus spp.). Other prey reported includes eels (Anguilla spp.), limpets (Patella spp.) and rays (Raja spp.) (Neves 1998).

The Mediterranean monk seal is one of the most endangered species of mammals (IUCN, 1996), and was ranked as a marine mammal species in imminent peril of extinction in a recent analysis (Vanblaricom et al. 2001).

Mediterranean monk seals have a long history of interaction with humans that includes exploitation for subsistence needs, commercial harvest and persecution as a competitor for fisheries resources or because it produced damage to fishing gear. Once abundant, monk seals were written about and illustrated in the literature and depictions of classical antiquity. Along the coast of northwest Africa, they became the target of a commercial harvest for skins and oil by the Portuguese as early as the 15th century (Israels 1992).

Reasons for the recent population decline leading to the species status as critically endangered include increased human pressure displacing seals from their habitat, destruction of caves used for hauling out and breeding, continued mortality due to fisheries by-catch, deliberate aggression by fishermen to eliminate a competitor, even in countries and areas where the species is legally protected, disease, pollution and impoverished genetic diversity (Aguilar 1999).

Interactions with fisheries are of great conservation concern, particularly for the subpopulation in the eastern Mediterranean, where seals are killed through net entanglement and deliberately killings by fishermen. They could also suffer from depletion of fish stocks in this area as well as being harassed by anti-seal methods designed to protect aquaculture facilities. Illegal dynamite fishing might also kill seals (Güçlüsoy 2004, 2004). Monk seals have been entangled in a wide variety of fishing gear including set-nets, trawl nets and long-lines. They seem most vulnerable to set-nets placed on the bottom and can also become entangled in abandoned and discarded nets (Tudela 2004). The deaths of 130 seals over a 10-year period ending in 1999 pointed out the significance of deliberate killing as a source of mortality (Tudela 2004). Deliberate killing of monk seals by humans was responsible for 1/3 of all mortalities of 79 stranded animals in Greece and is considered the single most important source of mortality for this species (Androukaki et al. 1999). Adverse fishing interaction is not a source of concern for the Atlantic subpopulations (Aguilar 1999).

Analyses of 42 DNA microsatellite loci have show that, as a consequence of a severe bottleneck, all subpopulations have suffered a dramatic decrease in genetic variability over the last few centuries. Indeed, the genetic diversity of Mediterranean monk seals is amongst the lowest found in pinnipeds; it is comparable to Hawaiian monk seals and northern elephant seals. The potential consequences of mating between closely-related individuals include congenital defects leading to stillborn pups and a decreased reproductive rate, both of which have been documented in the Cabo Blanco colony. As a consequence, extremely low genetic variability and inbreeding have been pointed out as the main cause for the non-recovery of subpopulations that are not subject to significant human pressure, such as that in Cabo Blanco (Pastor et al. 2004, 2007). Additionally, low fitness and increased susceptibility to disease may be an effect of genetic erosion that can compromise a population and lead to extinction. The mass mortality event of 1997 may have decreased the genetic diversity in the Cabo Blanco seals by 12% (UNEP 2005), and reduced the subpopulation's genetic diversity to a point where it cannot reproduce fast enough to overcome random events that effect survival (Forcada et al. 1999). Unless this factor is taken into account, usual conservation measures may prove ineffective.

Morbillivirus was isolated from Mediterranean monk seals after the mass mortality at Cabo Blanco in 1997. The virus most closely resembled dolphin morbillivirus (DMV) that was previously implicated in the 1991 mass mortality of striped dolphins in the Mediterranean Sea (Osterhaus et al. 1992, Van de Bildt et al. 1999). Canine distemper virus is present in stray dogs in Aegean Turkey at a level of approximately 9% in the population and this might be a source for future infections of monk seals through contacts in harbours and along shorelines (Gencay et al. 2004). However, although this virus was already circulating in monk seals prior to the mass mortality, there is some doubt as to whether it was responsible for the deaths that occurred. Indeed, the active virus was found in pups that went into a rehabilitation centre because their mothers had died, and none of them showed clinical signs and all survived the event without specific treatment. Dinoflagellate-produced saxitoxins were found in tissues from animals that died during the die-off and the suddenness of death of the animals and the general clinical symptoms suggest that the cause of death was from the toxins rather than a morbillivirus epidemic (Hernández et al. 1998). Toxic algal blooms (red tides) are favoured by oceanographic conditions near Cabo Blanco and were reported from nearby Morocco the south-eastern North Atlantic during a 25-year period leading up to the mass mortality. Toxic algal blooms are unpredictable and following the catastrophic loss of monk seals in 1997 must be considered a serious threat to the species (Reyero et al. 2000, UNEP 2005).

Contaminant burdens have always been suspected to be a threat to the Mediterranean monk seal and thus monitoring pollutants has been considered a high priority (Boulva 1979, Reijnders et al. 1993). However, information is only available on organochlorine pollutants, which were analyzed in the blubber of individuals collected during the 1990s from the Cabo Blanco and the Greek subpopulations. Residue levels were found to be very low in the former subpopulation and moderate to high in the latter (Borrell et al. 1997, 2007); the toxicological implications of these residues at the population level are unknown.

Mediterranean monk seals are at an unknown but suspected high level of risk from oil tanker and other ship accidents, spills and groundings. Animals could be oiled or coated in fuels and lubricants, exposed to other toxic or environment-altering chemicals or products and experience disturbance at haulouts or coastal feeding areas. Mauritania began oil extraction in offshore fields located about 400 km south of Cabo Blanco in 2006. This leads to increased tanker traffic in the area, and a greater chance for accidents, disturbance and collisions near important habitat. Three accidents or spills have occurred near monk seal habitat in the recent past, including a supertanker that spilled oil off of Morocco in 1989 (Israels 1992), an oil spill in the Madeira Islands in 1994 (UNEP 2005), and the grounding of a bulk carrier near Cabo Blanco in 2003 (UNEP 2005). None of these spills or accidents had any known impacts on monk seals, but they underscore the threat of significant impacts from a major maritime accident near an important monk seal site (UNEP 2005).

Human disturbance has also been identified as a primary factor in the decline in numbers of monk seals through displacement of animals from habitat. Traditionally, this was the consequence of expanding human populations and coastal development, but since the 1970s "eco-tourism", with organized or spontaneous tours of people seeking out monk seals to view at the few remaining locations, has grown to become one of the most significant hazards faced by monk seals in the eastern Mediterranean (Johnson and Lavigne 1999). Besides disturbance, tourist activities increase the risk of vessel accidents, spills, transmission of disease, and the discharge of pollutants and waste near the seals.

Additional risks to Mediterranean monk seals come from political instability and wars in some parts of their range, the challenge of implementing effective conservation for a species in a complex multi-national environment, weak enforcement of agreements and international laws, collapse of occupied pupping caves and reduction of the carrying capacity of the environment as a consequence of fishing overexploitation (Aguilar 1999).

The Mediterranean monk seal is legally protected throughout its range. Two protected areas have been established specifically for monk seals in the Desertas Islands in the Madeira Archipelago and the Northern Sporades Islands National Marine Park in Greece. There are plans to set up additional nature reserves to protect more habitat for monk seals in the region.

Throughout the range of the species, widespread action has been taken to sensitize the local human population towards monk seal conservation, to restrict fishing gear and relocate the most adverse fishing practices, to develop monitoring programs and intervention protocols and to increase on-site capability to rehabilitate sick and injured individuals, particularly pups. Numerous agreements, conventions, and treaties are in force to protect monk seals internationally, and many workshops and conferences have brought together scientist and managers to discuss monk seal conservation issues and problems. Israels (1992) summarizes 30 years of this conservation history, and provides details on accomplishments and failures to meet objectives. Currently, there is in force a UNEP/Mediterranean Action Plan (issued first in 1978 and revised in 1988) for the conservation and management of monk seals in the Mediterranean and a CMS plan for the recovery of the monk seal in the eastern Atlantic (issued in 2005).

However, all of the above actions have been insufficient to change the overall declining trend of this species. Most conservation initiatives occur only on paper and do not translate into real and effective conservation action in the field. As a consequence, most of the small subpopulations that survived three decades ago, when conservation of the species was already identified as being a priority are now extinct (Aguilar 1999). Today, human encroachment of haulout habitat, adverse interactions with fisheries and impoverished genetic variability are the main threats affecting the species. Unless there is urgent ion action, the extinction risk of the species is high (van Blaricom et al. 2001).