The status of grey seals (Halichoerus grypus) at Lundy, 2008-2009
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1. AimsThe principal aim is to produce a baseline study that will serve to commence a long-term seal study on Lundy. It would develop this initial perception of the abundance and distribution of seals and the timing of important events in their year into a monitoring of trends and changes over time. It would contribute to any investigation into why change may be happening. The Lundyphot seal identification catalogue (and its future development) will contribute to a developing regional effort to construct crude life histories of individual seals, their behaviours and their movements around the greater sea area of SW Britain-Eire-Brittany. Results from these studies and the way of storing them are intended to make it simple for coastal managers to make decisions relating to seals and the sites they use on Lundy which allow them to remain at favourable conservation status. A management plan is also produced here to assist that process. This baseline study sets out to: Identify nursery sites. Count number of pups born. Describe the season of pup production Monitor the fate of pups. Opportunistically, begin photo-ID catalogue for Lundy seals, including a category identifying seal mothers, attendant males and pelage markings of moulted pups. Identify year-round abundance and distribution of seals at haul-out sites and adjacent water resting places. Describe the season of moulting. Outline site-based and seal-based database features. Possibly, to respond to issues concerning seals arising during the survey. The original aim had been to run a baseline study to determine the number of grey seal pups being born at sites on Lundy, and therefore estimate the seal population size. The SMRU arrives at the grey seal population size for the UK by extrapolating outward from the numbers of pups born each year (although methods are currently being revised). However, this aim was revised because a fluctuation in seal numbers through the year that cannot be guessed at from pup numbers has been noted during year-round distribution and abundance studies conducted in southwest England, north Wales and Cumbria (Westcott, 2002, 2003, 2006, 2007, 2008). While breeding is universally recognised as an important season in the seal year, the season of moulting has received far less attention in grey seal studies. It is important to recognise which sites are most used by seals under the various weather and, especially, sea conditions. This has a crucial bearing on sites that might need to be monitored in any future study of trends in disturbance caused by people and their effects upon the seals. Where circumstances permitted, images of individual seals were captured and entered into a seal-based identification catalogue. This is a tool that will grow in value through the years. It allows crude life histories to be compiled for a sample of seals and should yield (behavioural) insights into site fidelity, fidelity to other seals and, in the event that disturbance becomes a larger issue than it appears to be at present, would allow the effects on individuals to be assessed. The intention is that images should be freely shared with any other party involved in seal photo-identification, perhaps with reference to advice from Natural England. This non-intrusive tool will allow out-of-area seal movements to be better understood. All data gathered on this survey is to be entered into a site-based database. The structure of the database is outlined in this report and can be used in future to hold any seal data gathered on Lundy. The final component of this survey will be to run a training programme to help Lundy-based people and Natural England personnel to monitor the seals in such a way that results will be repeatable and comparable over time and between sites. 2. Methods Study area This grey seal survey was conducted at Lundy. Map 1: Lundy. Lundy. Literature review Under normal circumstances, an initial review of the literature would have been carried out. However, the contract for this work was not initially confirmed until 17 September 2008 and the first visit to Lundy was not made until 23 September 2008. Consequently, the review was carried out in the evenings of days during which initial fieldwork was conducted. The primary source of references to seals at Lundy was the various editions of the Lundy Field Society Annual Reports. 2.3 Site access Commencing fieldwork by locating seal pups was the priority, as previous pupping studies at southwest England sites (as well as records held in the Lundy Field Society annual reports) show that pups are born from July onwards, although not necessarily in all years. Furthermore, at the nearest neighbouring grey seal breeding site – the Boscastle coast in north Cornwall – pups are regularly born from June onwards. Nearly all fieldwork was conducted, of necessity, by approaching seal sites from the sea. In order to keep the carbon footprint, as well as noise and costs, to a minimum, a wave ski was used to access all sites throughout the survey. This craft resembles a large surfboard but is paddled as you might paddle a kayak. The polypropylene construction ensures that if in collision with rocks, no damage will be done to the ski. It does not puncture and neither can it be dinged. The paddle is attached to the ski by rope. An ankle leash is attached to an anchorage point to the wave ski. The dry bags are attached to an anchorage point on the ski. Consequently, in the event of a capsize, nothing is lost. The lightweight craft can be easily righted. A life jacket is worn over a wetsuit at all times. Wet suit boots are worn at all times. A dry suit would be too warm and bulky to allow paddling with comfort. In cold weather, a hat and wetsuit gloves are worn. In rough conditions, a peaked cap is worn to keep seawater from the eyes. It was essential to make reference to a tidal flow atlas for Lundy. In addition, because such atlases cannot be expected to be consistently accurate, conversations were made with people who kayaked regularly in the Island waters. These conversations included discussion of the location of places of refuge along coasts apparently offering minimal refuge. An initial circumnavigation of Lundy was made on 24 September, on a neap tide. This was designed to identify all potential seal sites, especially sea caves, as well as places that might offer refuge in the event of misadventure. Many of these were explored. It developed into a partial survey because so many seal pups (including moulted and weaned individuals) were found. The fact that 19 pups (including moulted individuals) were located during that initial fieldwork indicated that the survey was commencing belatedly. Any future study to determine pup production for the Island sites should be continual. If that is impossible, site visits seeking pups should be made from June onward The methods deployed are more fully described in Westcott, 2008. The following general guidelines were observed throughout: Always seek to make a quiet landing at sea cave and remote beach sites, to try to avoid alerting any seals present. Always land on one or other wing of the site, or in such a situation that you can make best use of the available topography so as to avoid alerting any seals present. Most typically, this would entail moving along a cliff base. Be aware that lone seals often rest at the base of a cliff rather than in the middle of the fairway. Be mindful that seals can be very well camouflaged: their pelages can make them all but invisible to the scanning eye. Move as quietly as possible. In the bedrock and boulder environment that predominates on Lundy, always try to tread on the largest or most stable boulders. Treading on the smaller boulders and cobbles results in much more noise being made. If there is the possibility of being observed by a seal, crouch as you move – present the least ‘human’ appearance. In the event of coming face to face with a seal, if you have your camera held in front of your face, there is less likelihood that the seal will startle. However, in general, it is only rarely that seals in a sea cave will remain unaware of an intruder into their domain. Disturbance is almost inevitable. Nevertheless, the scale of the disturbance can be managed by practising, unfailingly, ‘quiet’ behaviour. The aim of the site visit is to spend the least time there and, ideally, to remain unseen throughout. Information collected included: Site plans, drawn approximately to scale and concentrating on the nature of the sea cave floor as well as any obstacles threatening safe navigation through the approaches to the cave. This is best collected during spring or early summer, when seals are least likely to be present and when sea conditions are less dangerous. Count the number of seals present, distinguishing males from females from yearlings. If the sex is unknown, do not guess but record it as unknown. Note the position of any seal assembly on the site. Count pups and attempt to ‘age’ them. Capture photographic images of the head and neck (left and right profiles) and chest of individual seals. Note the behaviour of the seals (e.g. are they moulting; is there aggression; are they unusually relaxed?). Note any human activity on or in the vicinity of the site. After each (monthly) visit to Lundy, a field report was sent to the Lundy warden and to Natural England (Exeter) to keep interested parties abreast of progress. A wave ski was used to transport the fieldworker and survey equipment to the seal sites. This kept the carbon footprint to the barest minimum, which is an important element of any conservation project. In addition, it allowed a near silent approach to, and a near silent landfall to be made on, the seal sites. This meant landfall could be achieved and field equipment could be unpacked and prepared for use without alerting or disturbing the seals. Making counts All counts were made as near as possible to the time of low water, or up to 90 minutes either side of low water. This was because, except where gross disturbance has occurred, this is the time when the largest numbers of seals are likely to be ashore (Westcott, 2002; Westcott & Stringell, 2003). Counts were made from a position of concealment wherever the terrain permitted. Capturing seal identification images There was a simple choice in capturing images: to function, in effect, as a sharpshooter or to use a blunderbuss, either method being entirely acceptable. I chose the sharpshooter method. This means I took single shots, as the opportunities arose. I chose this method out of habit, but also because I wanted the finest quality images, and because I was afraid that I would run out of space on the memory card if I used the alternative method. The blunderbuss method entails using the continuous shoot mechanism on the camera. For example, such a method may result in (for example) 10 rather than one image being captured each time a seal was targeted. When capturing images, the target area of the (grey) seal is the head and neck – always as much of the neck as possible – plus as much of the chest as possible. The ideal would be to capture all three images, in order to best facilitate the possibility of recapture. The other aspect of the ideal pelage would be that it is wet. The dry pelage markings can be matched to images of wet pelages, but with greater difficulty than matching wet to wet. Whenever possible, images of the side view of one flank of the body of the seal were captured, as this provides an even more failsafe way to identify an individual seal. However, these constituted only a very small minority of the images in the catalogue. Wherever possible, images were captured of the harbour seals. Almost all these images were captured at long range and provided full flank shots. All images were downloaded immediately and held in a catalogue for that date. At a later date, the images will be edited and the best available shots of every seal will be entered into the EIRPHOT catalogue or its successor. Minimising disturbance The effort to minimise disturbance is substantially described in section 3.3. In effect, the basic requirement is for the fieldworker to know either where the seals are or, at least, where they are likely to be, while remaining aware that the unexpected will occur from time to time, even so. In effect, this is achieved by the following procedure: While approaching the site, the fieldworker should be scanning ahead, watching for seals as well as hazards. Ideally, landing should take place at a site not overlooked by the seals so that preparation for fieldwork and initial movements to viewpoints can be invisible to the seals. A preliminary scan using the naked eye as well as binoculars should be made before working on site. Be aware whether the wind is carrying your scent to or from the seals – their sense of smell is excellent. In moving, effort should be made to quell any flamboyance. In effect, movement should be dead (head down, arms still) so that nothing might draw attention to it. It seems to help if the (brightness of) face is covered by holding the camera up before it. Be careful to tread on rocks that will not move. If only small boulders form the substratum, select the largest stones to tread on, as thus footfall will be least noisy. It helps, where the sun is out, to keep it as far as possible behind you. If accessing a cave that may be walked into, conduct the preparation of all essential equipment (torch, camera, towel around shoulders upon which to wipe grit or dampness from hands, notebook and pencil) beyond the line of sight and, so far as possible, beyond the hearing of the seals. When entering the cave, move slowly, quietly, along the nearest wall, thereby reducing, as far as possible, your human profile. Keep your head down, thereby concealing the (giveaway) brightness of your face. Use the ambient light for as long as you can. Try not to use your torch until absolutely necessary to do so, as this will herald the most active interlude of your visit. Counting pups or adults (noting their sex) and immature seals is the priority. Be prepared to capture photographic images if possible. If you find you are capturing only one profile of any seal present, cross over to the far side of the cave to improve your chances of capturing the other profiles. At no point allow the seals to come between you and the cave entrance – keep your line of retreat open at all times. Researchers have in the past been cornered in sea caves by seals for prolonged periods. In such a situation, do not react with aggression. Their experience suggests that you should adopt a submissive air. I have never experienced such a situation and recommend that you avoid it by keeping clear your line of retreat at all times. If accessing the cave by use of a wave ski or kayak, make sure that your torch is attached to your clothing by a carabina. Use a waterproof camera or camcorder, because if something can happen, odds are that it will. Use a dry bag stowed inside a second, larger dry bag to carry the items you need for your work. It is sensible to carry two middle-sized towels, one for laying out equipment upon landing, one for keeping hands dry and clean when handling, especially, the photographic equipment. At all times, try to cause least disturbance and to spend the least possible time on site. 2.7 Daily writing up of field notes and data storage In the field, notes were made in a notebook or on a slate board using a 2B pencil. Upon return to base, the notes were written up in the following order: Environmental data and survey results were entered into the database. The images captured during that day were downloaded and filed. The daily count data was entered on to an Excel spreadsheet. Finally, a prose account of the survey effort of that day was recorded, which included detail of the sex and age breakdown for the various sub-assemblies Health and safety protocol A health and safety protocol was developed, drawing on the relevant chapter in Westcott, 2008, but also in response to local conditions. In practise, on Lundy, the following steps were taken: Before departing on an expedition, the warden or her assistant were informed. The intended survey area was described, along with most likely places of refuge in that area. An approximate time of return was nominated. Upon returning from the expedition, the warden or her assistant were informed. A waterproof EPIRB (Emergency Position-Indicating Radio Beacon), provided by the warden, was carried every time an expedition was made. In the event of misadventure occurring in a sea cave, the EPIRB would be activated and thrown into the sea (as it cannot function when in a cave. All equipment was carried inside one dry bag stowed inside a second bag (in order that if the outer bag was punctured by barnacles or something other, the inner bag and its contents would remain waterproof). No expedition was made if the sea state exceeded Beaufort force 4 – not exclusively for reasons of safety but also because it is very difficult to land or depart from Lundy sea caves and beaches, where the substrate nearly always consists of bedrock or boulders. The course taken on the water always sought to avoid hazards, most especially the two tide races – there are, in effect, little ‘alleyways’ both at the SW and NW corners which allow the races to be partially by-passed. A lifejacket was worn at all times. A fully charged mobile phone (containing the numbers of the Swansea Coastguard, the warden, the assistant wardens and other islanders) and a fully charged VHF radio were carried on every expedition (SW holds a VHF radio operators license, having qualified earlier in 2008). A compass was carried at all times, to be used in the event of mist coming down or being swept away in one of the tide races. A first aid kit was carried at all times (SW renewed his basic first aid qualification in 2008). Two fully charged Kowalski torches were carried at all times. Several towels were carried, in part to protect all items carried in the dry bags in the event of collision with a rock, but also for wiping grit from hands before using photographic equipment or making notes. They could also potentially function to staunch heavy blood flow, at need. In addition, SW has a current qualification in Survival at Sea. He qualified as a MCA Boatmaster in 2008. He swims and paddles the wave ski most days of every year and has done over the past 20 years. 4. ResultsDownload 1.63 Mb. Share with your friends:
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