FEASIBILITY STUDY FOR DAILY MONITORING OF A POTENTIAL BREEDING CAVE FOR THE MEDITERRANEAN MONK SEAL, MONACHUS MONACHUS

H. Güçlüsoy¹, G. Mo², Y. Savas¹, C. Sigismondi²

¹ SAD/AFAG, Mediterranean Seal Research Group: sadizmir@rocketmail.com
² Gruppo Foca Monaca, c/o WWF-Italia: grupfoca@tin.it; mogiulia@tin.it

INTRODUCTION

As one of the most endangered pinnipeds of the world, the Mediterranean monk seal (Monachus monachus) is also one of the most difficultly managed from a conservation point of view, partially because of the unknown aspects of much of its biology (IUCN/UNEP, 1988). Unlike its congener, the Hawaiian monk seal (M. schauinslandi), which breeds on open sandy beaches (King, 1964), the Mediterranean monk seal’s use of terrestrial habitat for breeding, moulting and resting activities mostly occurs in coastal caves with sufficient haul-out areas (IUCN/UNEP, 1988). Although this choice of breeding area has provided some degree of protection to the seals, it has hindered acquisition of basic information that in other species is well known and statistically confirmed. Information such as animal identity and coastal presence must therefore be limited to sightings while at sea, which requires good sighting probability and visibility (Gücü, 1999). Cave checks also provide useful information, but they are limited by sea conditions, and can constitute disturbance to delicate breeding and resting sites (Savas, 1999).

Over the last several decades, general conservation action plans and directives issued by the European scientific community for the conservation of the monk seal have partly advocated that efforts be undertaken in researching basic aspects of the biology of the species and in developing non-invasive techniques of monitoring the existing population without threatening the survival of the individuals under study (Johnson & Lavigne, 1998).

Closed circuit surveillance video systems were experimented with in the past in Madeira (Parque Natural da Madeira) and in the Western Sahara (Spanish Monk Seal Project, Cap Blanc) to monitor the monk seal’s behaviour while on land. Surveillance in the Western Sahara did not involve use of infrared light sensitive equipment but yielded substantial information on animal identity, lactation length, mother-pup interactions, pup and adult moulting (Badosa et al., 1998, Gazo et al., 1999, Pastor et al., 1999). In contrast, the surveillance unit used in Madeira was equipped with an infrared sensitive monochrome CCD camera in a waterproof housing, infrared lights, a video and a 12V 40A battery. The system was used for 12 days but seal presence in the cave could not be recorded (Freitas, 1994).

A cross collaboration scheme was developed between the Turkish research group, SAD-AFAG, and Gruppo Foca Monaca, a WWF-Italy associated volunteer group, to develop and test a non-invasive method that would allow 24 hour surveillance of a monk seal cave. The methodology was designed so as to gain information on cave use, individual identity, sexual gender, moulting activities and, if applicable, crucial information on reproductive aspects such as birthing details, mother-pup interactions, lactation duration and frequency, pup independence, and vocalisations.

DESCRIPTION OF THE STUDY AREA

The site chosen was a frequently used monk seal cave situated on the island of Orak, in the Foça Specially Protected Area, approximately 70 km north of Izmir on the Central Aegean Coast of Turkey (Fig.1) (Güçlüsoy & Theunissen, 1997). Turkey’s first seal conservation project, the Foça Pilot Project, was initiated in this region in 1992 by a Turkish NGO, SAD-AFAG, in association with the local Monk Seal Committee, and with the financial support of WWF (Cirik & Güçlüsoy, 1995). Large scale fisheries are prohibited in the area since 1992, and human activity is restricted since it is one of the most important monk seal habitats in Turkey.

The monk seal cave chosen for this study was the second-highest recorded breeding site of a group of approximately 9 photo-identified monk seals studied since 1994 (Güçlüsoy & Theunissen, 1997). The cave is situated in a small bay. The rock formation is of volcanic origin and is called "tuff". Its entrance faces north-west and is characterised by a long water corridor of approximately 14 meters in length whose vault has an open access to the sky, of approximately 1.0m x .75 at midpoint of the corridor. The beach is characterised by small pebbles and is triangular in shape, the width being 2 meters and the depth 3 meters. The height of the vault in the beach area is at its most 1.5 meters and slopes down to the end of the beach area to .5 m except for a narrow crevice in the top of the vault, which extends approximately 3 meters to what is the top of the ceiling of the cave.

MATERIALS AND METHODS

The system used in Foça was based on an in-cave unit containing a monochrome CCD, an infrared sensitive board level camera (with a lens having an angle of view equivalent to a 15mm lens of a 35mm photo camera), two units containing LEDs (30 + 50 each of 20mamp) producing infrared light, and a microphone. Both the camera and the light sources were placed in watertight housings and the microphone was wrapped by fine latex material. One group of LEDs (30 units) was placed in the same housing and surrounding the camera, while the other group (50 units) was placed 30 cm above the camera in a separate housing. The housings were cylindrical in shape and made of Perspex and reinforced with aluminium. The video camera housing was 70mm in diameter, 50mm in height and weighed 300 grams. All the technical material was provided, designed and assembled by Pandafilm, Rome (pandaflm@tin.it). The total price of the technical equipment was approximately $6,800 (CCD unit = $250.00; assemblage and material of 1^st and 2^nd Perspex housing inclusive of connections and LEDs = $1,100.00; video tape recorder and b/w monitor = $2,200.00; microphone, cables, watertight submersible connections and accessories = $3,300.00).

A small tube fixed to the top of the Perspex camera casing allowed the front of the camera-containing unit to be rinsed in case a foreign object accidentally obstructed vision (i.e. Sea grass leaf, etc). The tube extended out to the top of the cave and 20 meters away from it, allowing freshwater to be flushed down by gravity over the Perspex housing any time the Perspex appeared soiled and vision was impaired. The in-cave unit was mounted on a stainless steel bracket, which was fixed into the cave wall with special rock bolts.

The monitoring unit containing a B&W monitor, a VHS video and a control panel was placed approximately 100m away from the in-cave unit, in a camp tent. The system operated under 12V DC and was fed by two 6V serial connected batteries. Six solar panels were used to recharge the batteries. The batteries, once charged, guaranteed power supply in case of solar panel failure for at least 3-4 days.

The interior of the cave was monitored through the surveillance system for 21 days on a 24 hour basis by a group of 4 people working 3-4 hour shifts (Fig. 2). If the monitor could not be supervised directly by the observers, the video recorder was turned on, allowing the tapes to be viewed at a later date. Any event deemed of relevance was recorded on VHS tapes. In case of seal presence, video recording was accompanied by the filling out of specially prepared data sheets.

Installation of the unit was conducted during midday hours as it is generally believed that there is a lower chance that seals may be present on land at this time of day. During the duration of the project, the research team members paid particular attention to avoid being present on the cliffs above, and in the area around, the cave.

RESULTS AND DISCUSSION

During the 21-day period of the study, two different individual female seals were observed using the cave, and their behaviour was recorded on VHS tapes and on special printed forms designed for this study (Fig. 3).

Of the two seals observed in the cave, the first entered the cave and scanned its head in side to side movements, while hauling out and approaching the camera until nasal contact was made. This has led to the belief that the seal may have perceived the unit, possibly by olfaction. The second seal, on the other hand, did not demonstrate any similar behaviour and did not approach the unit.

Although the in-cave unit was subjected to heavy seas washing through the entire cave during storms, the camera housing and the infrared LEDs were not affected at all. On the other hand, the microphone protected with fine latex was broken during the first ten days of use and required maintenance and replacement. The new microphone functioned properly until the end of the study.

During the day, light filtering through the corridor of the cave allowed the camera to function in normal mode although the light reached it directly and caused any object to appear silhouetted. Nocturnal use of LED illuminators allowed vision of the beach but with gradual loss of detail with increasing distance from the camera. A seal at the edge of the beach could just be discerned.

The present study has demonstrated that non-invasive monitoring techniques can be developed and applied to allow detailed information on daily cave use and monk seal individual identification. The study represents an indication of the potential available in the application of instruments that are nowadays commercially available in most Mediterranean countries and applied to a variety of other domestic and commercial circumstances.

The application of these instruments could provide useful tools to Mediterranean researchers as to the daily, seasonal and permanent use and choice of caves by monk seals, as well as detailed identification of physical traits that help in differentiating one seal from another. The system can also allow individual growth and age class estimates, which are sometimes difficult to obtain from observations at sea, as well as providing information on biological aspects of the species that are still questionable (e.g. moulting: seasonality, trend with age-classes and sex, duration, amount time spent on land). The technique could further provide better insight on fundamental aspects of mother-pup interactions. At the same time, application of cameras to more than one cave in a given area can allow an accurate determination of preferential and selective cave use by individuals over time.

Modifications to the system, such as application of more powerful infrared illumination and placement of multiple cameras and infrared light sources, are feasible with minor adjustments to the system.

REFERENCES

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Savas, Y. 1999. Documentation Techniques used in researches on highly endangered Mediterranean monk seal Monachus monachus. SAD Sualti Günleri’99 Sempozyumu. 26-27 February 1999, Ankara, Turkey. (in prep.)