Spatial and temporal patterns of occurrence of the vulnerable Mediterranean monk seal in the Tyrrhenian Sea via seawater eDNA

Abstract Historical evidence suggests that the Vulnerable Mediterranean monk seal Monachus monachus , one of the most threatened pinniped species, commonly used to haul out on open beaches. However, in recent times, probably driven by increased human disturbance, the species tends to seek refuge in remote marine caves, typically those that include one or more entrances above or below water level, an entrance corridor, an internal pool, and a beach that provides a dry haul-out area. Here we present evidence of monk seals using a bubble cave, an air-filled chamber or dome, accessible through an underwater passage, where seals remain in the water without any platform or beach to haul out. These wet, less accessible and inconspicuous domes may not only provide refuge against human disturbance but also play a role as resting sites, complementing breeding and haul-out caves. The observations reported here suggest that habitat suitability studies for the Mediterranean monk seal may benefit from including bubble caves, as they provide valuable resting spots, especially in tourist areas where seals may be exposed to human disturbance.

Anthropogenic debris poses an increasing threat in the marine environment due to its persistence and adverse effects on marine biota and ecosystem services. Previous anthropogenic debris research has centred on shorelines, surface waters, the water column, coastal seafloor and deep-sea domain, leaving sea-caves largely overlooked. This study introduces a novel quantitative approach tailored for sea cave systems, broadening the scope of marine litter research beyond previously targeted environments. All surveyed sea caves contained debris, with densities ranging from 0.044 to 96.839 items m-2. Most debris was primarily transported via sea-based pathways, and consisted mainly of fragmented plastics (66%). Occasionally debris was found embedded within tar layers, producing "plastitar" deposits on cave walls. Analyses revealed that wave exposure and available beach area influenced debris retention, while differences in cave architecture resulted in distinct interior spatial deposition patterns across two cave types, leading to the formation of accumulation hotspots. Findings demonstrate that semi-submerged sea caves serve as important reservoirs for anthropogenic marine debris alongside toxic chemical components and potentially associated harmful microbiomes. Such contamination poses risks to sea cave biota and likely compromises the conservation efforts for the Mediterranean monk seal (Monachus monachus).

ABSTRACT Mediterranean monk seals ( Monachus monachus ; MMS) are a vulnerable marine species historically widespread throughout coastal areas of the Mediterranean, Black Sea and parts of the North Atlantic. MMS have suffered significant population declines and extirpations due to anthropogenic pressures, particularly persecution, overfishing and impacts of tourism. Extant populations are fragmented, but recent trends indicate some re‐colonisation in the historic range. This study sought to understand opportunities and threats to MMS re‐colonisation in Croatia. It gauged support for MMS return and perceptions of different management options from two stakeholder groups. Structured questionnaires were used with fishers to assess the threat of persecution and overfishing, and with visitors to understand their willingness to pay (WTP) conservation fees to support environmental initiatives. Our results indicate that while persecution may no longer be a pertinent threat to MMS in Croatia, overfishing threatens fish stocks and the marine environment. Results also suggest that tourism could generate funding for conservation initiatives, particularly through on‐arrival visitor fees. We consider key management options to support MMS re‐colonisation, including expanding the current marine protected area network and demarking new no‐take zones, working closely with fishers, establishing financial mechanisms for compensation and subsidies, developing awareness raising campaigns, and implementing one‐off conservation fees.

News and social media are increasingly recognised as valuable sources of species observation data, particularly for rare and endangered species. However, these data sources are prone to biases arising from uneven observation efforts, which poses challenges for their effective use. Despite this issue, the drivers and extent of such biases remain understudied. Here, we investigate the contribution of social media and news media towards improving the availability of observation data for a rare and endangered species, the Mediterranean monk seal Monachus monachus , in Madeira and Porto Santo. We also assess the relationship between the observational data and socio-human factors likely to determine spatial and temporal variation in observation effort. Media sources provided a considerably higher number (27-fold) of observation records (n = 302) compared to reference biodiversity observation data repositories such as GBIF, iNaturalist, and Observation.org combined (n = 11). The number of observations exhibited seasonal variation, with annual peaks in the summer months. A generalised linear model assessing the spatial distribution of observational data also revealed a strong positive association with areas of high human concentration. Significant predictors of species observation included human population density, hotel density, and proximity to coastal recreational hotspots such as diving sites and bathing areas or non-open beaches. Our results underscore the potential of news and social media for documenting species distributions, but they also emphasise the importance of accounting for observational biases. This ensures reliable and effective use of news and social media data for species conservation and management.

Forensic scatology: insights into the secretive Mediterranean monk seal via a comprehensive molecular analysis of aged and recent fecal samples

Camera trap monitoring of the haul-out behavior of Mediterranean monk seals on Gökçeada Island in the North Aegean Sea

The interactions between marine predators such as the Mediterranean monk seal (Monachus monachus) and fish farms have raised concerns regarding the potential environmental impacts of the industry on surrounding marine ecosystems. This study investigated the potential role of fish farm workers in monitoring marine biodiversity around aquaculture sites, comparing their potential involvement with that of other maritime workers. Interviews were conducted with maritime workers, including fish farm workers, in order to understand their perceptions of monk seal interactions with fish farms. The author also carried out direct data collection at fish farms to validate these perceptions. The results show a strong alignment between the workers’ perceptions and the data collected by the author on key parameters such as the presence, frequency, and seasonality of monk seals on fish farms. Furthermore, 75% of the 16 fish farm workers interviewed expressed no animosity toward monk seals. This underscores fish farm workers potential for involvement in monitoring initiatives and their understanding of monk seal interactions on fish farms. Given their constant presence at sea and proximity to key interaction zones, maritime workers are well-positioned to monitor environmental pressures and provide valuable data. With appropriate training, these workers could become valuable participants in targeted citizen science efforts, enhancing the public image of the aquaculture industry and advancing research on marine life in the vicinity of aquaculture installations.

Vocal recordings and underwater video of the rare Mediterranean monk seal could aid conservation efforts.

BackgroundThe Monachinae, or southern seals, are one of two subfamilies within the Phocidae and are home to iconic pinnipeds such as the leopard seal, a fierce Antarctic top predator, and the Mediterranean monk seal, one of the world’s most endangered mammals. These two species are difficult to study and sample, due to their hidden lives in extreme environments or, in case of the monk seal, their critically reduced population sizes; consequently, genetic data from these two species is scarce. However, cost developments and advances in genome sequencing have made it possible to generate continuous genome assemblies from DNA of even stranded individuals, allowing to assemble the first reference genomes of such rarely observed species.ResultsIn this study, we have sequenced the genomes of the leopard seal and the Mediterranean monk seal using PacBio’s CCS technology to assemble the very first genomes for these species. Four additional Mediterranean monk seal individuals were sequenced using Illumina short-read technology. These data allowed analysis of their demography and genomic diversity based on whole-genome data, confirming low genetic variability and small numbers of individuals for the Mauritanian population of the Mediterranean monk seal. In contrast, the relatively abundant leopard seal shows a high degree of heterozygosity, comparable in the range of other common carnivores.ConclusionsThe first genome assemblies for these seals will lay the groundwork for population-level and other studies to better understand their evolutionary history and biology and to aid conservation efforts.

Mediterranean monk seals (Monachus monachus) are the world's rarest seal species, with fewer than 1000 individuals remaining across fragmented subpopulations. Monitoring this species is challenging due to their low densities and difficult-to-access habitats. Passive acoustic monitoring (PAM) data can be used to detect small numbers of animals over large areas, but for effective long-term PAM, it is essential to characterize the species' vocalizations throughout its range. This study provides a comprehensive description of the monk seal vocal repertoire in the Inner Ionian Sea Archipelago, Greece, and the first published documentation of the species vocalizing underwater. Acoustic recorders collected continuous data over 16 days during the breeding season in 2021. We identified 3442 calls, 1855 of which were determined to be high-quality and classified into ten call types within three broader categories. Video footage collected in 2019 and 2021 documented the seals producing five common call types, which comprised ∼87% of the recorded calls. Our findings offer insights into the structure of the monk seal vocal repertoire and lay the groundwork for long-term monitoring for this rare species using PAM, which could be an important tool for monitoring monk seals going forwards.

From August 2021 to December 2023, one adult male Mediterranean monk seal was repeatedly registered, through a systematic monitoring camera system, frequenting a marine cave in southern Kefalonia Island, central Ionian Sea, Greece. The presence of the same adult seal in a series of caves and overhangs in a bay in northwestern Zakynthos, southern Ionian Sea, in September 2023 and May 2024 was verified through opportunistic surveys and citizen science. The two locations are ca. 15 km apart and each is located in a different marine NATURA 2000 site. Appropriate conservation measures need to take into consideration the fact that seals do move between Kefalonia and Zakynthos (and possibly also other Ionian islands) and that the entire area has to be considered as a single "conservation unit" rather than elaborating protection measures on a small scale around a couple of resting and pupping caves alone. A full network of marine caves under strict protection surrounded by a buffer zone, taking into account at least the species' home range, is needed in order to substantially cover the monk seal's critical terrestrial habitats throughout the Ionian Sea.

Intentional harm to marine mammals refers to deliberate human actions that cause injury, suffering, or death, and it is illegal in many countries. These actions often result from direct human attacks and are motivated by various reasons, with retaliation by fishermen being the most common. Such attacks cause severe tissue damage, frequently leading to the debilitation or death of the targeted animal. In this report, we document 13 cases of intentionally harmed marine mammals: 12 bottlenose dolphins Tursiops truncatus and 1 Mediterranean monk seal Monachus monachus found in the Croatian part of the Adriatic Sea between 1990 and 2023. Our analysis includes the life history data of the attacked specimens, post-mortem findings, and the weaponry involved. Among 311 post-mortem examinations conducted, 4.2% revealed intentional harm. Adult male bottlenose dolphins were most frequently targeted (46.2%), with a majority (53.8%) succumbing immediately due to exsanguination. Shotgun pellets, bullets, and underwater speargun spearheads were recovered from their carcasses. The attacks occurred with no discernible seasonal pattern; however, 61.5% of the cases were recorded from Istria County. Our findings underscore the inadequacy of current surveillance and enforcement in protecting marine mammals from deliberate harm. We advocate for the implementation of educational initiatives targeting relevant groups, intensive sea patrols, and routine inspection of weapons with high penalties for illegal possession and misuse, all reinforced by media campaigns to combat this malicious human behaviour.

Abstract Pinnipeds have vibrissae with which they can explore their environment. Two vibrissal parameters that differ in pinnipeds are shape and number. Regarding shape, most phocids have undulated vibrissae, whereas the vibrissae of a few phocids, all otariids and walruses are smooth. As there is disagreement with respect to which phocid vibrissae lack the undulation, we systematically collected information on vibrissal type. We have documented that all eared seals we examined, walruses, Mediterranean monk seals, bearded, and leopard seals have smooth vibrissae. All other phocids have undulated vibrissae, except for Ross seals and Hawaiian monk seals, which have partially undulated vibrissae. Moreover, we quantified and documented the existence of vibrissae from photos revealing otariids to have 20–43 mystacial vibrissae/pad, no rhinal vibrissae, 1–2 supraorbital vibrissae above each eye, and phocids to have 15–97 mystacial vibrissae/pad, 0–2 rhinal vibrissae/nostril, 1–9 supraorbital vibrissae above each eye, all averages determined from counts made from photos. Walruses have the maximum number of mystacial vibrissae amounting to 198 vibrissae/pad on average, but almost all walruses lack rhinal and supraorbital vibrissae. Vibrissae were found at the upper lip and on the lower jaw in some pinnipeds.

Mediterranean Monk Seal, Monachus monachus, was monitored along the northern coast of Syria during the period 2001-2023, and the potential caves were identified.Thirty-four sightings were obtained in 9 different areas of the coast; three of which were photographed.In addition, sixteen caves potentially suitable as habitats were documented; they were concentrated in the area extending from Ras Al Bassit to Oum Al Tiur (9 caves) and that extending from Burj Islam to Slaib Al Turkman (7 caves).These visual sightings, in addition to existence of potential habitats, confirm that Mediterranean Monk Seal is present on the Syrian coast, either as a visitor, as a migrant transient, or as a settler.More research is need to prove the residence and breeding status on the Syrian coast.

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.

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.

The Mediterranean monk sealMonachusmonachusis 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.

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.

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.