Protection of the Endangered Mediterranean Monk Seal

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Overview

Geographic location of the Mediterranean Monk Seal, Monachus monachus. Populations are mainly located in the Mediterranean Sea and on the coast of Africa.

Mediterranean monk seals (Monachus monachus) are robust marine mammals in the Phocidae family. Adult seals grow up to 2.8m in length and weigh between 240kg-300kg. They have short flippers and a flat, wide head. Coloration of Mediterranean monk seals varies with sex and age[1]. Mediterranean monk seals are one of two monk seals remaining on Earth[2]. These seals are found in the Mediterranean Sea and in the Atlantic Ocean along the northwestern coast of Africa. The subpopulations of the seals are geographically isolated from one another. Seals from the Mediterranean Sea are typically darker than those found in the Atlantic Ocean. Mediterranean monk seals are non-migratory and spend most of their life in a very limited home range[1].

Mediterranean monk seal (Monachus monachus)

Mediterranean monk seals are one of the most heavily endangered marine mammals on the planet. The seal's population status is of concern due to both its ecological and social importance[3]. Mediterranean monk seals have become endangered due to several threats including hunting, habitat deterioration, and fishing bycatch. There are only 500-600 Mediterranean monk seals remaining and the risk of extinction is high. Pup survival is low due to storms and rough oceans. The genetic variability of remaining seals is low due to very small breeding populations that are geographically isolated from each other. Additionally, in 1996, a large outbreak of a phytoplankton-based paralytic toxin caused a massive die-off[1]. There are several efforts being made to save this species, such as habitat protection, changing the nature of interactions between fishermen and seals, monitoring populations, and attempting to rehabilitate the seals. This page will describe these protection efforts and discuss their effectiveness, as well as propose other potential mechanisms for protecting the Mediterranean monk seal.

Status

The Mediterranean monk seal, Monachus monachus.

The Mediterranean monk seal is considered to be one of the most endangered marine mammals in the world. The species is labeled as "Endangered" under the United States Endangered Species Act, "Depleted" under the Marine Mammal Protection Act, and "Critically Endangered" under the International Union for Conservation of Nature[2][3]. Additionally, the seals are listed as an Appendix I species under CITES and an Appendix II species under the Bern Convention[4]. Being listed as an Appendix I species means that the seals are threatened with extinction and are not allowed to be traded for commercial purposes[5]. Currently, there are less than 700 Mediterranean monk seals remaining in the wild, with roughly only 400 of those individuals considered mature[2]. There are three existing subpopulations of the Mediterranean monk seal; Eastern Mediterranean, Western coast of Africa as well as Madeira archipelago[2]. Although all three populations appear to be recovering, their species have suffered an overall decline in number, primarily due to habitat deterioration and human activity[2]. Specifically, the seals are currently threatened by tourism, boat traffic, risk of entanglement with human fishing equipment, as well as deliberate killings by fishermen who see the seals as threats to the amount of fish they harvest[4]. In the Cabo Blanco subpopulation, the current number of individuals is estimated to make up just 3% of its historic population[2]. In multiple other areas of the world, the species is now extinct; for example, according to the IUCN Red Book of Mammals for Croatia the species is listed as extinct in the Adriatic Sea[6]. Although the species status seems dire, there are possible conservation strategies that can be implemented to improve the seals future outlook.

Ecological Importance

The Mediterranean monk seal is integral to the maintenance of healthy marine ecosystems. As an apex predator, the species heavily controls the populations of its prey and keeps these populations balanced, maintaining the healthy functioning of their ecosystems[7]. They are top predators in their ecosystems, other than killer whales and sharks, and are known to keep crustacean, fish and squid populations under control[8]. The seals consume a wide array of marine life including eels, sardines, tunas, and lobsters and various other crustaceous organisms, consuming up to around 40 species[8]. They are benthic feeders and tend to feed in shallow waters along coastal areas[9]. This is important to the flow of energy and matter between benthic and pelagic parts of an ecosystem, connecting different parts of the marine ecosystem together[4]. If these seals were to disappear, it would have devastating impacts to other marine populations and subsequently the entire ecosystem. For this reason alone, it is crucial for this species to receive greater recognition and further incorporation into conservation management plans.

Social Importance

Historically, the Mediterranean Monk Seal would sometimes appear in mythology and ancient stories, however the species seemed to generally be feared by ancient Greeks and Romans due to its physical characteristics, their language often portraying the species negatively[10]. These views can potentially be attributed to the overall decline of the seals populations as the seals may have been extirpated due to this general dislike of the species[10]. Despite some of these negative views, the seal was still important in ancient storytelling; for example the ancient Roman city of Phocis was named after the seal, becoming the city's emblem[10]. Additionally, the Mediterranean Monk Seal was also hunted by humans for multiple purposes, the main purpose being a source of food. The seal was also hunted for its skin as well its body parts, which were sometimes used to treat medical problems[8]. Pelts were used to make tents, providing people with protection, skins provided shoes and clothing and the fat was used for oil lamps and candles as well as medicinal purposes such as treating wounds and contusions[8]. Presently, the seals are no longer hunted for human-use, however they are still very important to humans in terms of human-value reasons in relation to conservation.

Population Monitoring

This small group of seals represents 1.4% of the remaining world population of Mediterranean monk seals.

Identification of different aerial or underwater seal vocalizations have been used to describe population compositions. Understanding the composition of different seal groups can help determine the health and growth potential of different seal populations[11]. Higher birth and survival rates of pups can signify a higher likelihood that populations will experience rapid growth in the near future[12]. However, the Mediterranean monk seals' pup survival rates have historically been low due to the stresses of their environment, such as rough oceans and storms[1]. Populations within reserves can be monitored by analyzing the number of sightings of identifiable individuals. This would include sightings from shore, or through camera traps, which could be set up at resting sites and at the entrance of caves[4][13].

Threats

Deliberate Killing

Humans have exploited the Mediterranean monk seal since prehistoric times[14]. The seal was especially ill-treated during the Roman era[14]. During the Middle Ages, monk seals were hunted commercially in regions such as the Madeira and Canary Islands, as well as in the Bay of Dhakla in the Western Sahara[14].

Today, the Mediterranean monk seal is most commonly hunted by fishermen[11]. These illegal, deliberate killings are committed by workers who are upset over the damage they believe the seals have caused to their fishing gear and by the subsequent loss of fish that could have been caught[11]. Fishermen have been known to shoot seals or even blow up their caves with dynamite[11]. Between 1991 and 1995, deliberate killing was responsible for one-third of Mediterranean monk seal mortalities in Greece[11]. Another study performed in Athens found that between the years 1990 and 2004, deliberate killings accounted for between 45 and 50% of adult seal deaths[15]. In Turkey, deliberate killing has been a major cause of species decline[11]. In Cabo Blanco, deliberate killing may have even resulted in the local extinction of the seal[11].

Fishing Bycatch

Aside from deliberate killing by fishermen, the Mediterranean monk seal often becomes accidentally entangled in fishing gear, resulting in drowning and death[2]. Younger seals are especially susceptible to entanglement as they are less cautious, less experienced, and not as strong, therefore they are less able to escape once caught[2]. Entanglement in fishing nets occurs often since monk seals tend to eat the same fish that are sold commercially[2]. Between the years 1990 and 2004, 44% of sub-adult seals near Athens were killed by entanglement in fishing gear. 6% of adult seals died by fishing bycatch during those years[16]. Between 2006 and 2009, forty seals were entangled in fishing nets off the coast of the Greek island Kalymnos alone[2]. All forty of the seals were injured[2]. The month of May in particular is a common time for fishing bycatch to occur since, on average, 30% of juvenile seals in Greece drown due to entanglement in fishing gear during this month alone[2].

Habitat Deterioration and Human Encroachment

Anthropogenic influence has resulted in the Mediterranean monk seal becoming a solitary species, despite formerly existing in colonies in the sea[6]. The Mediterranean monk seal historically occupied open beaches, particularly during pupping season, but human encroachment has forced the seal to retreat to marine caves which are less accessible to people[14]. Displacement to caves has been largely responsible for the low survival rate of seal pups, since young seals may be washed away by waves and then drown or be separated from their mothers and die of starvation[14]. Human influence has resulted in the destruction, alteration and fragmentation of suitable monk seal habitat[11].

Construction on open beaches and breeding grounds is also an issue for the survival of the monk seal[14]. Tourism in particular is a large threat, as it results in an increase of human disturbance as well as further development of infrastructure in the area[14]. In some cases, hotels have been constructed directly on top of marine caves being used by the monk seal for breeding[3]. Habitat deterioration is of particular concern in places such as Turkey, where people have noted seals who must rest while floating in the water due to a lack of beach area even within their caves[3].

Diving activity by tourists has also negatively impacted seal populations, as pupping activity has stopped in some areas which are now frequently visited by divers[3]. Boating activity, particularly in Greece, Turkey, and Morocco, has allowed people to visit even the most remote locations where monk seals are located and has also resulted in several cases of seals being struck and killed[3].

Methods of Protection

Habitat Protection

Mediterranean monk seal in a coastal cave.

Mediterranean monk seals give birth primarily in coastal caves[16]. The protection of these caves is crucial to the survival of this species. Mediterranean monk seals chose their cave based on a variety of different characteristics such as luminance, beach visibility, entrance depth, corridor length, main beach substrate, and human activity[16]. All of these characteristics are important when Mediterranean monk seals are choosing their habitats but the most important characteristic is human activity[16]. Mediterranean monk seals chose caves that have very low human activity as these caves are quieter, darker, and have a lower risk of disturbance[16]. Mediterranean monk seals also chose their caves based on the availability of fish near the cave. Overfishing has had an extreme impact on the seals and is another reason why the seals must chose caves far away from human disturbance[17]. As fish numbers decline Mediterranean monk seals are left to feed on fish trapped in nets. This is extremely dangerous for the seals as their risk of entanglement is very high[17]. To help save Mediterranean monk seals several protected reserves are being created throughout the range of the seals. Research, management, and a variety of conservation methods are all in place to help save Mediterranean monk seal habitat[18].

Reduce Conflict between Fisheries and Seals

Fishery related deaths are one of the major threats to Mediterranean monk seals. Accidental entanglement in fishing nets results in the drowning of a seal and is a major cause of mortality for Mediterranean monk seals[15]. Some Mediterranean monk seals are also deliberately killed by fishermen as they can damage fishing gear and tear nets resulting in fish loss. Deliberate killing of Mediterranean monk seals is illegal in efforts to increase the population[15]. Environmental education of fisherman is extremely important when limiting negative effects of fishing on Mediterranean monk seals. From 2005-2009 the European Union held a LIFE-Nature project that was solely focused on the reducing conflict between fisheries and Mediterranean monk seals. At the end of the project an Action Plan was created but the Action Plan was never put into action due to financial constraints[18]. In some regions where Mediterranean monk seals live, clean-up efforts are being made by fisherman to reduce the amount of fishing-gear in the ocean to reduce accidental entanglement of the seals[18]. There are many efforts being made to reduce the conflict between fisheries and seals but it is an ongoing problem that requires continues efforts by governments, fisheries, and the public.

Rehabilitation Efforts

Populations with a high number of extinction predictors, such as a measure of zero pups born, low percentages of breeding adults, and low percentages of juvenile seals, require immediate efforts to increase survival rates for both adults and juveniles. Survival rates can be increased through direct human intervention, including the rescue of both abandoned pups and seals caught in fishing equipment[4][13]. Rehabilitation centers in Greece have rescued and rehabilitated Mediterranean monk seals for over three decades[19]. These efforts have been coordinated by The Hellenic Society for the Study and Protection of the Monk Seal, and include collaborations with the Seal Rehabilitation and Research Centre (SRRC) in the Netherlands and public universities in both the Netherlands and Greece[19]. The goal of rescuing and rehabilitating these seals is to maximize the health of the seal before their eventual release[19]. The rehabilitation centers welcome daily visitors and hope to increase awareness of the seals' endangered status by sharing each seal's recovery journey with the public[19].

Outlook

Mediterranean monk seal (Monachus monachus) resting on a beach.

There have been multiple conservation projects underway for the past few decades, however, progress has been slow and generally insignificant. This is mainly due to the lack of government funding and limited public knowledge on the species[20]. The current trends of monitored populations indicate that species numbers increasing. However, the number of mature adults in these populations continues to decline[21]. As threats continue to grow and impact the habitat and health of these seals, their rate of recovery is unlikely to increase. Climate change, one of the most significant threats to this species, continues to evolve and alter the state of the seal's home range[21]. Unless global action is taken, the waters that include the Mediterranean monk seal's range will continue to warm, acidify, and become more polluted. Reactionary protection, such as rehabilitation, will not be enough to bring the numbers of this species back to a healthy level[21].

References

  1. ↑ 1.0 1.1 1.2 1.3 Jefferson, Thomas A.; Webber, Marc A.; Pitman, Robert L. (2015). "Marine Mammals of the World". Science Direct. Retrieved 2023-04-14.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 National Oceanic and Atmospheric Administration (September 16, 2022). "Mediterranean Monk Seal".
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 "The recovery of the Mediterranean monk seal in the Atlantic: a success history". Convention on Biological Diversity.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 "Mediterranean Monk Seal". Seal Conservation Society.
  5. ↑ "Convention on International Trade in Endangered Species". Government of Canada.
  6. ↑ 6.0 6.1 "Mediterranean Monk Seal". Blue World Institute.
  7. ↑ Muneoka, Lauren (August 4, 2011). "Why care about monk seals?". KAHEA: The Hawaiian-Environmental Alliance. Retrieved March 8, 2023.
  8. ↑ 8.0 8.1 8.2 8.3 Benton, Melany (2000). "Monachus monachus". Animal Diversity Web. Retrieved March 8, 2023.
  9. ↑ G. Gilmartin, William; Forcada, Jaume. "Monk Seals". Encyclopedia of Marine Mammals (Second Edition) – via Elsevier ScienceDirect.
  10. ↑ 10.0 10.1 10.2 M. Johnson, William; M. Lavigne, David (1999). Monk seals in antiquity: the Mediterranean monk seal (monachus monachus) in ancient history and literature. Leiden: Backhuys Publishers. ISBN 861030988 Check |isbn= value: length (help).
  11. ↑ 11.0 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Muñoz, Gabriela (2011). "Aerial Vocalizations by Wild and Rehabilitating Mediterranean Monk Seals (Monachus monachus) in Greece". Aquatic Mammals. 37: 262–279 – via ProQuest.
  12. ↑ Sibly, Richard; Hone, Jim; Clutton-Brock, Tim (September 2002). "Population growth rate: determining factors and role in population regulation". National Library of Medicine – via UBC Library.
  13. ↑ 13.0 13.1 Durant, Sarah; Harwood, John (1992). "Assessment of monitoring and management strategies for local populations of the Mediterranean monk seal Monachus monachus". Biological Conservation.
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 Karamanlidis, Alexandros A.; Dendrinos, Panagiotis; Fernández de Larrinoa, Pablo; Gücü, Ali C.; Johnson, William M.; Kiraç, Cem O.; Pires, Rosa (November 18, 2015). "The Mediterranean monk seal Monachus monachus: status, biology, threats, and conservation priorities". Mammal Review. 46 (2): 92–105 – via Wiley Online Library.
  15. ↑ 15.0 15.1 15.2 "Mediterranean Monk Seal". NOAA Fisheries.
  16. ↑ 16.0 16.1 16.2 16.3 16.4 Dendrinos, Panagiotis (June 11th, 2007). "Pupping Habitat Use in the Mediterranean Monk Seal: A Long Term Study". Marine Mammal Science. Check date values in: |date= (help)
  17. ↑ 17.0 17.1 Gucu, Ali Cemal (April 2004). "Habitat use and preliminary demographic evaluation of the critically endangered Mediterranean monk seal (Monachus monachus) in the Cilician Basin (Eastern Mediterranean)". ScienceDirect.
  18. ↑ 18.0 18.1 18.2 Karamanlidis, Alexandros A. (November 18th 2015). "The Mediterranean monk seal Monachus monachus: status, biology, threats, and conservation priorities". Mammal Review. Retrieved 2023-04-14. Check date values in: |date= (help)
  19. ↑ 19.0 19.1 19.2 19.3 "MEDITERRANEAN MONK SEAL REHABILITATION IN GREECE 1990-2004: 15 years of action" (PDF). The Monachus Guardian.
  20. ↑ Johnson, William. "Mediterranean Monk Seal". Monachus-gaurdian.org.
  21. ↑ 21.0 21.1 21.2 Karamanlidis, A.; Dendrinos, P. (2017). "Mediterranean monk seal (monachus monachus)".
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