Monachus Research Articles

Distribution and habitats of the Mediterranean Monk Seal (Monachus monachus): In the Syrian Coast (Eastern Mediterranean)

Distribution and habitats of the Mediterranean Monk Seal (Monachus monachus): In the Syrian Coast (Eastern Mediterranean)

An Observatory to monitor range extension of the Mediterranean monk seal based on its eDNA traces: collecting data and delivering results in the "Open Science" era.

The monk seal is the most endangered pinniped in the world and the only one found in the Mediterranean, where its distribution and abundance have suffered a drastic decline in the last few decades. Data on its status are scattered due to both its rarity and evasiveness and records are biased towards occasional, mostly coastal encounters. Nowadays, molecular techniques allow us to detect and quantify minute amounts of DNA traces released into the environment (eDNA) by any organism. A species-specific molecular assay is now available for detecting the recent presence of the monk seal in the water column through the analysis of sea-water samples collected from the sea surface. The project "Spot the Monk" uses this non-invasive detection tool to monitor monk seal occurrence in Mediterranean waters by means of eDNA analysis. The simplicity in the acquisition of samples together with the need to collect samples in multiple points simultaneously made the project well suited to the involvement of the general public. Up to today, about 350 samples have been collected and analysed in the central-western Mediterranean by researchers and a multifarious range of citizen scientists - from recreational sailing organisations, both amateur and competitive sportsmen, to fishermen. This work announces the launch of an open-source Observatory (https://www.spot-the-monk-observatory.com/) where the project outcomes are publicly accessible as soon as they are produced. Embracing the principles of Open Science, we believe that such an approach can contribute to filling the knowledge gap about the distribution of this charismatic species in our seas, providing, at the same time, a proof of concept on how data collected by a variety of actors can be returned to the scientific and non-scientific communities in an innovative format for immediate consultation.

Ten Years of Mediterranean Monk Seal Stranding Records in Greece under the Microscope: What Do the Data Suggest?

This paper presents the results of an analysis of stranding events of the Mediterranean monk seal Monachus monachus over a decade. The analysis involved categorization according to the cause of stranding and seasonality, the identification of hotspot stranding areas and an assessment of possible correlations between stranding events and environmental/climatic patterns using time series analysis. Moreover, Generalized Additive Models (GAMs) were applied to explore the effects of the size of small-scale fishing grounds, the number of species sightings, and the occurrence of reproduction sites on "human-related" strandings. Finally, special focus was put on the central part of the eastern Ionian Sea for the assessment of stranding hotspot areas by means of the Multi-Criteria Decision Analysis (MCDA) approach, based on different kinds of spatial information such as anthropogenic pressures and the location of breeding sites and feeding grounds. Time series analysis results revealed that oscillation indices, during the first half of the year, and sea surface temperature (SST) in the Mediterranean from October to December were positively correlated with monk seal stranding events. GAMs underlined that areas combining extended small-scale fishery grounds and a higher number of sightings were more likely to cause more strandings. Regarding spatial analyses, the central Aegean Sea was highlighted as a hotspot for "human-related strandings", while the MCDA approach emphasized that the southern coasts of Cephalonia and the gulf between Lefkada and mainland Greece were susceptible to subadult strandings.

Current status, biology, threats and conservation priorities of the vulnerable Mediterranean monk seal

The Mediterranean monk seal Monachus monachus is one of the most endangered marine mammals on Earth. The species has made a notable recovery during the past 10 yr and is now considered Vulnerable by the International Union for the Conservation of Nature. Its global population comprises 3 subpopulations: 2 in the northeastern Atlantic Ocean and one in the eastern Mediterranean Sea. Global estimated abundance is 815-997 individuals, including 443-599 mature individuals; annual pup production averages 170.5. Over the past decade, increased research efforts have shed new light on various aspects of the species’ biology and life history, including habitat and habitat use, vital rates, communication and genetics. The main threats to the species are (1) terrestrial and marine habitat loss and degradation that has or is resulting in the occupation of unsuitable habitat and limited prey availability, (2) negative interactions with fisheries that result in accidental entanglement or deliberate killings in response to damages to catches and/or fishing gear, (3) unpredictable threats, including cave collapses and mass mortality events and (4) pollution. Priority conservation actions for the species include (1) strengthening the legal framework for the protection of the terrestrial and marine habitat of the species, (2) effective protection of the species and its terrestrial and marine habitat, (3) scientific population and habitat monitoring, (4) rescue and rehabilitation of injured, orphaned and sick pups to increase neonatal survival rates, (5) public awareness and education, (6) monitoring and mitigating negative seal-fishery interactions and (7) expansion of the species’ current geographic range in the Atlantic Ocean.

First assessment of passive acoustics as a tool to monitor the endangered Mediterranean monk seal in the Madeira Archipelago (Portugal)

Abstract The rarest seal and the world's most endangered pinniped species, the Mediterranean monk seal (Monachus monachus), has a small and isolated population in the Madeira Archipelago (Portugal). This species tends to be extremely wary of humans and, therefore, very difficult to approach and study. Passive acoustic monitoring (PAM) is a non‐invasive, cost‐effective tool that can be a valuable complement for the traditional monitoring methods, providing insight for effective conservation of the seal in the Madeira Archipelago. In this pilot study, custom‐designed autonomous underwater recorders were deployed in two marine protected areas (Garajau Partial Nature Reserve and the Desertas Islands Nature Reserve) to assess the potential of PAM to detect and monitor this elusive and endangered species in the Madeira Archipelago. Two call types putatively produced by M. monachus were detected in a subsample of audio files recorded over a 3‐month acoustic deployment; these call types share similarities with the /growl/ and /hiccup/ recently described for M. monachus in a Mediterranean population. The most common sound type detected was the low‐frequency growl. No obvious pattern was found in the abundance of sounds according to sampling date, and no significant difference was found in the abundance of sounds in different periods of the day. The ability to detect the species' underwater vocalizations with PAM opens the possibility of future monitoring plans based on data obtained from audio recordings. These data can provide relevant information for conservation, namely, on the presence and abundance of the seals.

Fecal and skin microbiota of two rescued Mediterranean monk seal pups during rehabilitation.

This study showed that during the rehabilitation of two rescued Mediterranean monk seal pups (Monachus monachus), the skin and fecal bacterial communities showed similar succession patterns between the two individuals. This finding means that co-housed pups share their microbiomes, and this needs to be considered in cases of infection outbreaks and their treatment. The housing conditions, along with the feeding scheme and care protocols, including the admission of antibiotics as prophylaxis, probiotics, and essential food supplements, resulted in bacterial communities with no apparent pathogenic bacteria. This is the first contribution to the microbiome of the protected seal species of M. monachus and contributes to the animal's conservation practices through its microbiome.

Monk seals (Monachus monachus) in the Mediterranean Sea: The threat of organochlorine contaminants and polycyclic aromatic hydrocarbons

The Mediterranean monk seal (Monachus monachus) is an emblematic species of conservation concern. Anthropogenic pressures have led to severe population declines and significant fragmentation of the remaining populations. Because of their close relationship with coastal areas, Mediterranean monk seals may be potentially exposed to pollution from agricultural sources, as well as from oil tanker spills. Although monitoring of pollution has long been considered a priority for this species, data on monk seal contamination levels are scarce. In this study, 55 blubber samples of all genders and age classes collected during necropsies (1995–2013) from seals of the Eastern Mediterranean subpopulation were analyzed for organochlorine compounds (OCs), i.e., hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDTs), and polycyclic aromatic hydrocarbons (PAHs). Overall, PCBs > DDTs ≫ PAHs > HCB in all samples. Results showed a significant downward trend over the 19-year period for DDTs and HCB. No marked pattern was found for PAHs, even though relative abundance of cancerogenic PAH fraction rose in recent years. PCB levels in subadult specimens increased noticeably over time despite worldwide ban. Our findings did not suggest recent releases of DDT or new pesticides (e.g., Dicofol) in the environment, but may indicate an improper disposal of ancient storages of PCBs or a remobilization from reservoirs. OC levels exceeded thresholds that are commonly associated with immunosuppression and reproductive impairment in other pinnipeds. Hence, OCs could be responsible of potential toxicological effects in this subpopulation. This study represents the first report on PAH and one of the few reports on OC bioaccumulation in Mediterranean monk seals. Based on the levels found in the blubber of monk seals from the Eastern Mediterranean, and given the known harmful effects associated to the prolonged exposure to these substances and the reduced long-term expectations of species recovery, regular monitoring is advocated.

From Atlantic to Greece. The Case of Nasal Mite in Mediterranean Monk Seal

From Atlantic to Greece. The Case of Nasal Mite in Mediterranean Monk Seal

Report on the brain of the monk seal (Monachus monachus, Hermann, 1779).

The Mediterranean monk seal (Monachus monachus, Hermann, 1779) is an endangered species of pinniped endemic to few areas of the Mediterranean Sea. Extensive hunting and poaching over the last two centuries have rendered it a rare sight, scattered mainly in the Aegean Sea and the western coast of North Africa. In a rare event, a female monk seal calf stranded and died in southern Italy (Brindisi, Puglia). During due necropsy, the brain was extracted and fixed. The present report is the first of a monk seal brain. The features reported are remarkably typical of a true seal brain, with some specific characteristics. The brain cortical circonvolutions, main fissures and the external parts are described, and an EQ was calculated. Overall, this carnivore adapted to aquatic life shares some aspects of its neuroanatomy and physiology with other seemingly distant aquatic mammals.

Revealing the Mediterranean Monk Seal (Monachus monachus)’s Cave Preference in Gökova Bay on the Southwest Coast of Türkiye

The first cave-monitoring studies to be carried out on the southwest (SW) coast of Türkiye on endangered Mediterranean monk seals using camera traps occurred between 2017 and 2021 in five marine caves within Gökova Bay. The visual data obtained from the monitoring studies were evaluated to reveal the Mediterranean monk seals’ seasonal and diel cave use and identify the individual seals who were using the caves. Moreover, the necessary features and measurements of the identified caves were recorded to determine whether there were any correlations between the determined variables and monthly cave use by the monk seals. The results showed that cave use occurred mainly nocturnally, with the seals showing a diurnal activity pattern in the area. We evaluated 108,280 images/videos in total and identified 18 individuals using five caves in Gökova Bay. Three of these caves provided suitable characteristics for pupping, and two of them were used for pupping. A beta regression model revealed that the monthly cave use ratios varied seasonally, with more use in the fall season. Furthermore, the trends in annual cave use ratios, seasonality, wind speed, size of the wet area, luminance, number of cave-entry paths, and human activity were the best variables with which we could forecast the cave preferences of the seals.

Understanding the Interactions between Small-Scale Fisheries and the Mediterranean Monk Seal Using Fishermen's Ecological Knowledge.

Interactions between fisheries and marine mammals have been well documented in almost all existing fishing gears around the world, often associated with detrimental consequences. Interactions of the endangered Mediterranean monk seal (Monachus monachus) with small-scale fisheries have been previously documented in the Mediterranean; this is a problem that seems to be growing in recent years. The present study aims to understand for the first time the nature and extent of interactions between the Mediterranean monk seal and small-scale fisheries in the Republic of Cyprus. The data were collected by conducting in-person semi-structured interviews, between November and December 2020, with 90 fishermen operating from nine different ports, extending throughout the entire coastline of the Republic of Cyprus. The results revealed minimal interactions between the Mediterranean monk seals and small-scale fisheries. The findings indicate that interactions are more likely to occur at depths of less than 10 m, closer to the coast, with the use of trammel nets and gillnets, and during the spring and summer months. The encounter, depredation and incidental capture rates were calculated at 0.01 (0.95%), 0.005 (0.51%) and 0.0004 (0.04%) per fisher, respectively. Spatiotemporal closed areas are proposed as a potential solution to mitigate these interactions.

Investigating Rare and Endangered Species: When a Single Methodology Is Not Enough—The Mediterranean Monk Seal Monachus monachus along the Coast of Salento (South Apulia, Italy)

Several factors contributed, over time, to the Mediterranean monk seal’s sharp population decline. Despite the relative disappearance of documented breeding sub-populations, sightings have been collected, in recent decades, from most of the species’ former habitat. The conservation of this endangered marine mammal should also encompass those areas. We conducted our research along the coast of Salento (South Apulia, Italy) as a case study. To collect data on monk seal presence in the area, expected to be characterized by low numbers, we combined three different methodologies: a questionnaire to fishermen, interviews with witnesses of sightings, and a historical review of the species’ presence. The different methodologies allowed us to collect 11 records of recent sightings (after 2000) and 30 records of historical encounters (before 2000), highlighting that the species was already rare in Salento over the last century. Most of the historical information was concentrated between 1956 and 1988 (28 records), suggesting discontinuous occurrence in the area, possibly depending on the lack of monitoring efforts. Furthermore, a broad regional approach should be considered as a more effective path to aid the monk seal recovery, better comprehend the species’ abundance and movements, and eventually contribute to the overall health of ecosystems.

First Description of the Underwater Sounds in the Mediterranean Monk Seal Monachus monachus in Greece: Towards Establishing a Vocal Repertoire.

The Mediterranean monk seal Monachus monachus is one of the most endangered pinnipeds in the world, and is classified as "Endangered" by the International Union for the Conservation of Nature. Any additional knowledge about the species is invaluable to its effective conservation. In the present study, we deployed an autonomous underwater recorder in an important reproductive area of the Mediterranean monk seal in Greece to describe its underwater vocal repertoire. Over the 330 h of continuous recordings, 9231 vocalizations were labelled as potentially produced by Mediterranean monk seals, and 1694 good quality calls were analyzed. We defined 18 call types divided into three main call categories: harmonic, noisy, and pulsative calls. We also described the soundscape in which this endangered species lives and found that human activities around the two main pupping caves had a strong impact on the sonic environment of these seals: the noise level produced by boat traffic was high, and occurred on an hourly (25 to 50 min/hour) and daily basis (10.8 to 16.9 h/day). Such high levels of noise might not only impair the communication of the species, but also impact its survival, as chronic noise can induce physiological stress.

Playing “hide and seek” with the Mediterranean monk seal: a citizen science dataset reveals its distribution from molecular traces (eDNA)

Animal conservation relies on assessing the distribution and habitat use of species, but for endangered/elusive animals this can prove difficult. The Monk Seal, Monachus monachus, is one of the world's most endangered species of pinniped, and the only one endemic to the Mediterranean Sea. During recent decades, direct observations have been few and scattered, making it difficult to determine its distribution away from the Aegean Sea (core distribution area of the post-decline relict population). This study relies on environmental DNA (eDNA) analysis to detect the presence of the Monk Seal in 135 samples collected in 120 locations of the central/western Mediterranean Sea, spanning about 1500 km longitudinally and 1000 km latitudinally. A recently described species-specific qPCR assay was used on marine-water samples, mostly collected during 2021 by a Citizen Science (CS) project. Positive detections occurred throughout the longitudinal range, including the westernmost surveyed area (Balearic archipelago). The distribution of the positive detections indicated six “hotspots”, mostly overlapping with historical Monk Seal sites, suggesting that habitat-specific characteristics play a fundamental role. We applied single-season occupancy models to correct for detection probability and to assess the importance of site-specific characteristics. The distance from small islets and protected (or access-restricted) areas was correlated negatively with the detection probability. This novel molecular approach, applied here for the first time in an extensive CS study, proved its potential as a tool for monitoring the distribution of this endangered/elusive species.

Towards a strategy for the recovering of the Mediterranean monk seal in the Adriatic-Ionian Basin

Occasional but recurrent sightings indicate that the endangered Mediterranean monk seal is still present in most of its historical range within the Adriatic-Ionian region in the central Mediterranean Sea. However, in most of the adjacent countries, the species’ abundance and distribution are practically unknown. An actively reproducing sub-population with a minimum of 25 adult/sub-adult seals lives in the Greek central Ionian Sea. The latter can form a nucleus from which the entire Adriatic-Ionian Basin could be re-colonized if adequate conservation measures are implemented throughout the area and in a coordinated manner. We examine the historical presence in the region as a baseline for providing a benchmark for conservation. We further look into the species’ habitat availability, possibilities for a rapid population assessment and various parameters that are considered crucial for its conservation, such as the existence of Marine Protected Areas (MPAs), corridors for connectivity purposes as well as needs for raising public awareness. We recommend a series of interlinked actions within the framework of a conservation strategy the implementation of which will ensure the conditions for maintaining ecologically, demographically, and genetically viable sub-populations of this species emblematic for the entire Mediterranean Sea. To achieve this goal, a coalition of partners from this area is required in order to adopt the strategy and jointly implement the measures required.

Evidence of Mediterranean Monk Seal Predation on Loggerhead Sea Turtle in Lesvos Island, Greece

Evidence of Mediterranean Monk Seal Predation on Loggerhead Sea Turtle in Lesvos Island, Greece

Using ‘pup multipliers’ to estimate demographic parameters of Mediterranean monk seals in the eastern Mediterranean Sea

A thorough understanding of population demographics is important in planning and evaluating conservation actions. At the same time, it is also essential that conservation management strives to minimize uncertainty in decision making in order to avoid management errors, which in the case of endangered species might affect their persistence. Mediterranean monk seals are endangered and have been notoriously difficult to count, especially in the eastern Mediterranean Sea, where abundance estimates have relied mainly on expert judgement. To address this problem, a new approach to estimating the species’ demographics using ‘pup multipliers’ is introduced. Adopting a conservative and a more optimistic approach and following a review of the available species- and taxa-specific data, the following multipliers were proposed: 2.5-3.5 for estimating the number of mature individuals, and 4.5-6.0 for estimating the total number of individuals. These multipliers were then used to calculate, in a formal way, the population demographics of the Mediterranean monk seal in the eastern Mediterranean Sea and globally. In their current form, the pup multipliers proposed present a number of strengths, but also several caveats, limitations and/or points of concern and should therefore not be considered a panacea in the conservation of the species, but merely the starting point of efforts for further development. These efforts should ultimately aim at developing a population-specific pup multiplier for the Mediterranean monk seal that is based on a common monitoring approach between various countries and includes the collection of newborn pup count data from across the species’ range in the eastern Mediterranean Sea.

The first record of the Mediterranean monk seal (Monachus monachus Hermann 1779) in the marine coast of the Gaza Strip, Palestine

The first record of the Mediterranean monk seal (Monachus monachus Hermann 1779) in the marine coast of the Gaza Strip, Palestine

First demographic parameter estimates for the Mediterranean monk seal population at Madeira, Portugal

We provide the first comprehensive demographic assessment of the Endangered Mediterranean monk seal Monachus monachus population residing in the Madeira Archipelago to identify factors that may impede population growth. Encounter data was obtained for this small, elusive population from 2012 to 2021 using a variety of non-invasive methods. From birth to age 2 mo, when pups molt, survival averaged 0.57. From birth to 1 yr and from 1-2 yr, estimated survival rates were 0.47 and 0.85, respectively. Beyond 2 yr, survival estimates differed by sex: 0.98 for females and 0.90 for males. These survival rates are similar to published estimates from the Cabo Blanco (Western Sahara/Mauritania) population. This is remarkable given that Cabo Blanco is situated adjacent to the extremely productive Canary Current system, whereas the marine environment of Madeira is far less productive. Instead of reducing survival, low marine productivity in Madeira appears to manifest in strikingly depressed reproductive rates. We estimated a mean gross reproductive rate of just 0.31; less than half the value (0.71) reported for Cabo Blanco. The youngest parturient females in Madeira were 6 yr old, whereas 3 yr olds give birth at Cabo Blanco. Despite low fecundity, the monk seal population in Madeira has been recovering, aided by a series of conservation measures implemented since 1988. Our results document that abundance increased from 19 seals in 2013 to 27 in 2021. Despite this undeniable success, the monk seals of Madeira remain vulnerable and require continued monitoring and protection in order to persist.

The First Two Detected Cases of Polythelia with Possible Polymastia in the Mediterranean Monk Seal (Monachus monachus)

The First Two Detected Cases of Polythelia with Possible Polymastia in the Mediterranean Monk Seal (Monachus monachus)