Mediterranean Monk Seals

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Objective:

Increase number of monk seals using marine caves

Status:

Data collection in progress

Project:

Gökova Bay to Cape Gelidonya

Location:

Türkiye

Problem: The estimated current population of Mediterranean monk seals (Monachus monachus) worldwide consists of 450-600 mature individuals (Karamanlidis, 2024), up to 140 of which live on the Turkish coast (Karamanlidis et al., 2023). This species is classified as Vulnerable globally. Threats include habitat loss and degradation, limited prey availability, entanglement in fishing gear, deliberate killing by fishers due to seals damaging fishing gear and catch, marine pollution, and other unpredictable threats like cave collapses and mass mortality events (Karamanlidis, 2024).

Action: No-Fishing Zones (NFZs) were established to provide areas where fish abundance (prey) can recover. Additionally, the absence of interaction with fishing boats in these areas eliminates the risk of subadults drowning by accidental entanglement in fishing gear. AKD is also increasing awareness campaigns with local people and tourism industries, to prevent people from disturbing monk seal caves, which is where they rest, give birth and raise their pups.

Indicator: Increased observations of Mediterranean monk seals using the caves indicates successful marine protected area and education/awareness efforts.

Mediterranean monk seal. Photo: Zafer Kızılkaya / AKD.

Methods

Scoping of seal caves to monitor was completed by boat surveys aiming to identify all potentially suitable cave habitats. In total, 15 caves across the project area were identified as potentially suitable, of which 12 were monitored for the project period. Cameras were deployed in these caves throughout the year between 2019 and 2023. When a camera was triggered, three consecutive photos were taken followed by a 15 – 20 second video to improve individual seal identification, while maximising battery life in situations where wave and other activity (e.g. bats, mice, birds etc.) frequently triggered the camera traps.

In one cave in the Gökova project area there was continuous real-time video monitoring, reducing costs and also risks of disturbing monk seal individuals during cave visits, and providing video that could be transmitted directly from cameras to phones and laptops. This also aided identification of individuals due to better quality footage.

Footage and images were reviewed and where possible individual seals were identified by any distinctive markings. Where possible, the age group and sex of the individuals were also recorded. Camera data were then used to calculate total time spent by seals in caves, total number of haul outs (including multiple seals) and number of identified individuals.

During data review, the precise moment of cave entry and exit by seals was not always visible on camera, so the first or last time a seal was observed were instead taken as entry or exit times respectively. Events when a seal was seen for just one camera trigger, rather than repeated triggers, were used for identifying individuals but not for length of stay data.

Water damage and humid saline conditions meant the number of operational cameras varied throughout the monitoring period. Because the caves were remote and could only be visited every 3-4 months, it was difficult to pinpoint the time at which a camera stopped working. Although estimates were made of the percentage of time for which cameras in each cave were operational, these were not considered accurate enough to calculate an index for adjusted cave occupancy time. Therefore, the raw data were used, with the caveat that camera operationality varied across caves and years. On average cameras were operational an estimated 58.8% of the time, and yearly averages ranged from a low of 54.4% in 2023 to a high of 64.7% in 2020. Adjusting occupancy times using these values did not alter overall patterns.

Mediterranean monk seal and pup within coastal cave in the project area. Photo: AKD.

Mediterranean monk seals in marine cave. Photo: AKD.

Results

The duration of cave use by monk seals each year did not show a statistically significant change over the project period (Fig. 1).

Of the 12 caves that were monitored continuously for most of the period 2019 – 2023, nine were used by monk seals: 5 in Gökova, 1 in Bozburun, 1 in Göcek and 2 in Kaş.

In total, the time spent by all seals in all caves was 3,152 hours. The total number of haul outs observed, which can include multiple seals, was 327.

19-22 individuals were identified in Gökova Bay, 2 individuals were identified in Bozburun, 6 individuals were identified in Göcek and 9-10 individuals identified in Kaş. Due to inconsistencies in data collection between areas, individuals were identified separately for each area, so it is possible that some seals using multiple areas were counted more than once in this data (the total number of seals identified cannot be calculated by adding up the number of seals identified in each area).

Figure 1: Number of individual seals (pups and adults) identified across all caves in each project year (left), and total number of hours spent by seals in all caves (right).

Interpretation

The characteristics of the caves affect seals’ preferences, especially for breeding and nursing (Karamanlidis et al., 2004; Dendrinos et al., 2007). Cave 2, one of the least used, was exposed to human pressure more than other caves due to its location. In addition, the dry area inside was relatively small and was exposed to intense wave activity more frequently. In contrast, the most frequently-used caves both had sheltered pools and bigger dry areas.

Cave use durations were longer in 2021 and 2022 than other years due to a higher number of individuals using the caves. Some of these individuals were pups. Pup–mother pairs remain in the cave during the first week after birth and mothers spend most of their time in the cave with pups during the lactation period (3 – 5 months; Aguilar et al., 2007). Newborn pups begin to spend time in the water in relatively sheltered areas inside or close to the cave entrance within the first week (Karamanlidis et al., 2010; 2021a). From the monitoring data, the number of female adults using the cave usually increased when there were pups observed. Mother–pup bonding and the social bonding of pups, vocalisations for recognition, and caring for pups by other females were also observed during the study period.

Lessons learned

Camera traps tended to deteriorate over time due to the caves’ harsh saline environmental conditions and, depending on the intensity of the trigger factors, the batteries often ran out before the field surveys were able to renew them – some caves were particularly prone to this due to a lack of locations where camera traps could be set up to monitor seal use but avoid triggers by wave activity. To prevent this and improve image quality to improve individual identification, solutions were to use advanced-quality camera systems or camera traps and to increase the frequency of field surveys. Continuous monitoring was installed in two caves, using solar-powered, real-time monitoring systems.

There were also some challenges associated with identifying individual seals. The appearance of individuals changes between pup and adult life stages (Samaranch and González, 2000). It was also challenging to recognise individuals who do not have any scars or marks due to mating or social interaction, and to distinguish sex for younger age groups. Although sex can be determined from the shape of the belly patch on pups, this needs footage to be taken from the right angle.

Next steps

AKD is working on using artificial intelligence to report when monk seals and human activity are detected, using the continuous video monitoring systems. In future, regular and responsive patrols to monk seal cave areas outside No-Fishing Zones would help to protect the pupping caves and their vicinity, deterring potential disruption and potentially playing a crucial role in the survival of this species in this area of high tourist activity.