Dr. Ingrid Wiesel. Elizabeth Bay Optimisation Project

Transcription

1 Dr. Ingrid Wiesel P. O. Box 739, 204 Ring Street, Lüderitz, Namibia Tel.: (0) Fax: (0) Elizabeth Bay Optimisation Project Specialist Report: Effects of proposed mining operations in the Southern Resource Area on brown hyenas Dr. Ingrid Wiesel 30 March 2010 Executive Summary Brown hyenas (Parahyaena brunnea) of the southern coastal Namib Desert are ecologically unique. They are the only large carnivore in the area and almost exclusively feed on Cape fur seal pups (Arctocephalus pusillus pusillus). Brown hyena ecology is briefly described. Data sets that were recorded by the Brown Hyena Research Project and used for this report include the Carnivore ATLAS, road kill statistics, brown hyena capture information, mapping data and GPS and radio telemetry data. Data revealed that after a decrease in brown hyena abundance in the EBay area between 2001 and 2003, brown hyenas were recorded again in This EBay hyena clan s territory borders to the Peninsula clan territory to the north and to an unknown southern brown hyena clan to the south. Within the EBay clan hyenas territory, EBay beach is an important foraging area and there are seasonal differences in the use of the beach. The following main potential risks were identified: Disturbance of brown hyenas on EBay beach through the mining process and seawall construction, Effects of mining operations on territory boundary on the southern end of EBay beach through the mining process and seawall construction, Loss of the beach area as a potential food source for brown hyenas through the mining process and seawall production, and Disturbance and/or mortality of brown hyenas through increased traffic (all options) due to the improvement of roads and the extension of the road network. Suggestions are made to monitor changes in brown hyena activity and territoriality, and to reduce traffic-related mortality. These include the use of camera traps and the regular monitoring of the beach for hyena spoor and washed up carrion.

2 Introduction Background and Brief The brown hyena s current conservation status in Namibia is insufficiently known (vulnerable or endangered). The most recent IUCN classification (Wiesel et al. 2008) describes the status as Near Threatened. Namibian authorities consider the species to be extremely vulnerable in Namibia (Griffin, pers. comm.). It is currently listed as a protected species in the Nature Conservation Ordinance No. 4 of Its total population size in southern Africa is estimated as animals and Namibia s population is estimated at a maximum of 1200, with approximately brown hyenas inhabiting the Sperrgebiet. Brown hyenas occur at low densities throughout Namibia, but as a species adapted to arid living conditions, they are found at higher densities along the Namib Desert coast where they feed almost exclusively on Cape Fur Seal pups that are born on mainland breeding colonies or are washed up along the shore. The brown hyena has been declared a flagship species for the Sperrgebiet National Park and a first draft of the monitoring programme has been developed (see best practice guide Monitoring the Sperrgebiet and adjacent areas by M. Hauptfleisch 2007). The monitoring of the brown hyena population in the Sperrgebiet will not only provide information about changes in the terrestrial ecosystem but also indicate changes in the marine ecosystem. Hence this coastal population of brown hyenas is ecologically unique and it is one of the few remaining viable brown hyena populations in southern Africa. They are the main predators along the southern Namib Desert coast and fill the highest trophic level in the food chain (a terrestrial predator feeding on a marine predator). The Ministry of Environment and Tourism (MET) has recognised the coastal Namib brown hyena population s uniqueness and supports further studies to determine the conservation status in Namibia and to manage the population effectively (Griffin, pers. comm.). During the last twelve years of study, the Brown Hyena Research Project detected the limitations and adaptabilities of brown hyenas in the coastal areas of the Sperrgebiet. It is clear, that, although seals are an abundant and permanent food source, the brown hyena population is limited by other factors than food availability and quality. Intra- and interspecific competition, habitat limitations, habitat disturbance and the general clan structure seems to influence its population growth. Carnivores often show ecological stress and extirpation before other species are affected. They are particularly susceptible because of their large home ranges, low biological productivity and enormous sized areas, which are required to sustain populations and individuals (Ruediger 2000). The most important impacts on carnivores are direct mortality (e.g. road kills), indirect mortality (e.g. increased hunting), displacement and avoidance (e.g. avoidance to cross improved dirt roads) and finally habitat fragmentation/associated developments (e.g. shift of activity patterns) (Ruediger 1996). Therefore it is necessary to provide accurate, systematically collected data on animal movements during the systems planning stage for projects (April et al. 2001). The aim of this specialist report is to assess the likely impacts of the proposed mining operations in the Southern Resource Area on brown hyenas, particularly on their feeding ecology and territorial behaviour. Recommendations regarding mitigation measures and monitoring programmes are proposed. Study Area The area of the proposed mining site lies in the southern part of the Elizabeth Bay Mining Area. This Southern Resource Area is part of a south-west facing beach, similar to other beaches nearby (Abenteuer Bay, Atlas Bay, Wolf Bay). In this specialist report the area from the Lüderitz Peninsula to Prinzenbucht/Pomona is regarded as the affected area, as changes in brown hyena behaviour of the EBay clan may also influence the behaviour of adjacent clans. Approach to Study This report is a review of existing data sets collected by the Brown Hyena Research Project since The following data sets were considered: Namibian Carnivore ATLAS (incidental brown hyena sightings) Road kill statistics Brown Hyena Research Project Capture log Mapping Project Radio Telemetry GPS Telemetry Brown hyenas at Elizabeth Bay have been studied between 1999 and 2004 and again since May Hyena activity in the Elizabeth Bay area decreased between 2001 and 2003 with hardly any hyena activity recorded from 2003 to 2008, possibly due to increased mining activity. Hyena activity increased in 2009 again, when

3 mining activity decreased indicating an influence of mining activity on brown hyena behaviour and occurrence in that area. These assumptions will be used to discuss certain issues regarding the affected environment. Description of the Affected Environment Brown hyenas only occur in the southern African sub-region and are usually associated with arid environments. Brown hyenas are regarded as scavengers that only occasionally hunt with limited success. They are mainly nocturnal and, although they live in social groups called clans, are solitary foragers eating a variety of food, from fruit and insects to small and medium-sized mammals. Brown hyenas occupy territories and territory size is determined by the distribution of food sources, hence larger when food sources are widely distributed. Along the Namib Desert coast, brown hyenas predominately forage along the beaches and rocky shores in search for carrion that has been washed up. However, they also visit mainland Cape fur seal breeding colonies to scavenge and to kill seal pups. Seal pup non-violent mortality is high during the first month of their life (mid- December to mid-january) and many dead pups wash up along the coast, particularly along south-west facing beaches, as they are favoured by the prevailing ocean current. Therefore the coastal part of coastal brown hyenas home ranges is a predictable food source and territories of coastal brown hyenas are smaller than those of inland brown hyenas. Brown hyenas compensate for times of coastal food shortage by increasing their foraging effort in inland areas of their home range. However, as coastal hyenas home ranges are relatively small, they cannot entirely rely on finding enough food in inland areas. Brown hyena reproduction is slow. Usually only one female of the clan has a litter of two to four cubs that are weaned at 15 months of age. However, brown hyena cubs do not only rely on their mother s milk, but also on what the other clan members provide at the den. Every clan member supplements the cubs diet with solid food by carrying carcasses back to the den, hence influencing brown hyena cub survival. Changes in brown hyena abundance in the study area (Lüderitz Peninsula to the southern end of EBay beach) As mentioned above, brown hyena activity decreased in EBay between 2001 and It is unknown, but likely, whether the EBay clan became locally and temporarily extinct due to the increase of mining activity. The Wolf Bay clan, bordering the EBay clan s territory boundary to the north (Figure 1) became extinct around 2007/2008 due to road mortalities on the tar road between Lüderitz and Aus. Historically the Wolf Bay clan s home range included the seal colonies at Wolf and Atlas Bay and the EBay clan s home range overlapped with the Wolf Bay clan s at the Atlas Bay seal colony. The area around the seal colonies is extremely valuable to brown hyenas and the vacant Wolf Bay territory was soon included in the northern Peninsula clan home range around 2008, starting with the inclusion of the Wolf Bay seal colony first and including the Atlas Bay seal colony later. When brown hyena activity resumed in the EBay area in 2009, parts of the EBay clan s home range had been taken over by Peninsula hyenas and to date EBay hyenas do not make use of the food source at Atlas Bay, hence they are heavily relying on carrion washed up along the beaches and rocky shores. At present the EBay clan brown hyenas northern territory boundary borders with that of the Peninsula clan, and their southern boundary with that of an unknown southern clan (hyena occurrence has been confirmed in this southern area from visual and spoor sightings) (Figure 1). Historically the EBay clan s eastern boundary was located around Grillental, but is currently located to the west of the dune belt (see positions on Figure 2). Importance of EBay beach as a food source The distribution of recorded GPS locations of EBay clan members indicates that beaches and rocky shores show a higher density of usage than inland areas of the home range (Figure 2), which is particularly true for positions recorded in the mining area. EBay beach is visited frequently by foraging brown hyenas, but also for territory boundary maintenance at the southern portion of the beach. The beach is predominately visited at night with most activity occurring after midnight (Figure 3). While denning, brown hyenas spend time at the den from around sunset to midnight, and again around sunrise. Foraging time thus falls into the period between midnight and sunrise, as seen from the activity pattern at EBay beach. However, it is not yet known whether the EBay clan is denning at present. Activity at EBay beach is low during the day and can mostly be attributed to resting behaviour, as brown hyenas dig holes into the hummock vegetation for resting purposes.

4 Peninsula/Wolf Bay Clan Territory EBay Clan Territory Unknown southern Clan Territory Figure 1: Approximate territory boundaries of the potentially affected brown hyena clans.

5 Figure 2: Probability of utilisation of EBay beach by EBay brown hyena clan members Activity pattern at E-Bay beach No of positions Time Figure 3: Activity pattern of EBay clan members at EBay beach

6 Territories The frequency of visits to EBay beach differs between months (Figure 4). Most activity is recorded in January, during the time when most seal pup mortalities are washed up along beaches and rocky shores. In 2009 unusual seal pup mortality was recorded later in the year, possibly due to domoic acid poisoning. Therefore large numbers of dead seals pups were also washed up between March and June 2009, which is also reflected in last years data. Monthly frequency of visits to E-Bay beach Percentage January May June July August September October November December Figure 4: Percentage of monthly visits to EBay beach by EBay clan members Sources of Risk, Impact Identification and Assessment Mining Process and Seawall Construction a) Disturbance of brown hyenas on the EBay beach Brown hyenas are likely to be disturbed by the construction of the seawall and the mining process. It is likely that brown hyena activity will decrease in the affected area, as it has been the case at the Bogenfels Pocket Beach mining site (Wiesel 2009). At Bogenfels brown hyenas showed a preference for the use of Bogenfels beach when disturbance in the area was at its lowest in Bogenfels beach is also a south-west facing beach and due to the prevailing Benguela current, a lot of carrion used to be washed up on the beach, which therefore served as a valuable and reliable foraging area. Hence, brown hyenas showed a preference in foraging along the beach in 2005 before major construction of the mine started. From 2006 on-wards, hyenas avoided the mining area and Bogenfels beach. Habitat use was significantly different between 2005 and 2008 at Bogenfels beach. Furthermore, the density of GPS positions at Bogenfels beach significantly decreased over time. In general, disturbance seemed to have the largest impact on brown hyena movement and behaviour at Bogenfels beach between 2005 and This indicates that brown hyenas react quickly to disturbances by avoiding the disturbed area. They probably adjust to the change in human activity and habitat destruction over time, resulting in a more gradual decline of habitat use in the affected area. However, once mining is completed it is expected that brown hyenas will resume their activity in the area within the first post-mining/rehabilitation year. Mining Process and Seawall Construction Nature of Impact Disturbance of brown hyenas on the EBay beach. Extent Site-specific; disturbance will be limited to the beach area. Duration Medium term; only during the construction, mining and rehabilitation phases. Intensity Medium; disturbance can lead to the avoidance of the area and have consequences regarding the behaviour and ecology of brown hyenas (see below). Probability Definite; brown hyenas are easily disturbed and will avoid disturbed areas. Status of Impact Negative. Degree of Confidence High; studies from other mining areas (e.g. Pocket Beaches) show that brown hyenas avoid areas that are disturbed by construction and mining. Significance Medium; as the extent is site-specific and the duration is medium-term. Mitigation Rehabilitation of the beach area after mining is complete. Monitoring Recommendations Early morning brown hyena spoor counts on the beach before/during/after construction/mining or use of camera traps to detect changes in brown hyena activity at the beach.

7 b) Effects of mining operations on territory boundary on the southern end of EBay beach Brown hyenas are territorial animals with vast home ranges. Home ranges of clan members overlap and a common territory boundary is defended against intruders. Since brown hyenas are solitary foragers and generally only meet at den sites to socialise, territory maintenance is hence also carried out individually. For a home range to be and to remain defendable, an individual brown hyena has to deposit a paste mark approximately every 220 metres and visit the boundary area at least every 30 days (Wiesel 2009), but more probably as often as every 10 to 13 days. The territory boundary between the EBay clan and the southern unknown hyena clan lies at the southern end of EBay beach, close to the Southern Resource Area. As brown hyenas react to disturbances by avoiding disturbed areas, the maintenance of the southern territory boundary may become problematic. If the EBay clan is not able to mark their territory in this area to pass on territorial information to potential intruders from the southern clan, they may have to reclaim their territory boundary after mining is completed. A shift of the northern territory boundary is unlikely should the EBay clan become temporarily extinct, as the Peninsula clan s territory already includes two mainland Cape fur seal breeding colonies of high foraging value and a further extension of the home range to the south would decrease the clan s territorial defendability. Mining Process and Seawall Construction Nature of Impact Effects of mining operations on territory boundary on the southern end of EBay beach. Extent Regional; other brown hyena clans may be affected due to behavioural changes in territoriality of EBay hyena clan members. Duration Medium- to Long term; the establishment of territory boundaries can be a long-term process. Intensity Medium; as it can disrupt clan structure and distribution. Probability Highly probable; brown hyenas mark their territory boundaries and parts of their territory boundary will become inaccessible due to construction and mining activities. Status of Impact Negative. Degree of Confidence High; studies from other mining areas (e.g. Pocket Beaches) show that brown hyena territory boundaries can be affected by construction and mining activity. Significance Medium; as it can lead to long-term changes in clan distribution and structure (and ultimately also have an influence on local brown hyena survival). Mitigation Rehabilitation of the beach area after mining is complete. Monitoring Recommendations Camera trap surveys in territory boundary area, inside EBay clan territory and inside southern clan territory to establish an ID catalogue of resident hyenas and to detect changes in territorial movement and behaviour; or alternatively GPS telemetry of brown hyenas of the EBay clan and the southern hyena clan. c) Loss of beach area as potential food source South-west facing beaches are preferred foraging areas for scavengers because of the large amount of carrion that is washed up by the predominant southerly winds. EBay beach is such a south-west facing beach. Possession Island is situated to the south-west of EBay, so that seabirds and seals that die around or on the island may wash up along the beach. Furthermore, Elizabeth Bay is a breeding area for whales, and mortalities have been washed up on the beach in the past. The importance of EBay beach as a food source for brown hyenas is unknown at this point, but the beach should be monitored for washed up carrion to assess the situation before, during and after the seawall construction and mining phases. Seals are the major food source for brown hyenas, but seal pup mortality is highly seasonal and hence, the importance of EBay beach as a foraging site may differ between seasons. Mining Process and Seawall Construction Nature of Impact Loss of beach area as a potential food source. Extent Site-specific; impact will be limited to the southern resource area. Duration Medium-term; only during the construction, mining and rehabilitation phases. Intensity Medium; only if EBay beach is an important food source for EBay hyena clan members. Probability Probable; as carrion will still be washed up along the beach and brown hyenas may still approach and use washed up carcasses when hungry. Status of Impact Negative. Degree of Confidence High; studies from other mining areas (e.g. Pocket Beaches) show that brown hyenas still forage along affected beaches, although significantly less than before any construction or mining took place. Significance Low to Medium; depending on the importance of the beach as a food source.

8 Mitigation Rehabilitation of the beach area after mining is complete. Monitoring Recommendations To count washed up carrion along the beach before construction starts, during construction/mining and after mining is completed. Increased beach carrion monitoring should take place in November, before the start of the seal pupping season, in December, during the peak pupping season and in January after the peak of the pupping season, when most seal pup mortalities have already taken place and less carrion may be washed ashore. Counts should also take the weather/ocean conditions into account (wind, swell), as they influence the amount of carrion that is washed up Gravel Processing Roads and Powerlines Disturbance and/or mortality of brown hyenas through increased traffic (all options). A total of 26 brown hyena road kills have been recorded by the Brown Hyena Research Project, approximately ¼ of these occurred in mining areas (two at EBay between 2001 and 2003; five in Mining Area 1). Since the EBay clan seems to have re-established itself in the EBay mining area, increased traffic poses a real risk to this brown hyena clan s survival. Gravel Processing Roads and Powerlines Nature of Impact Disturbance and/or mortality of brown hyenas through increased traffic (all options). Extent Regional; as coastal brown hyena clan territories can be up to 800 km² in size. Duration Medium-term; only during the construction, mining and rehabilitation phases Intensity High; mortality influences clan structure and brown hyena survival. Probability Probable; although brown hyena density is high along the southern Namib Desert coast, the limited clan size and the size of coastal brown hyena clan s territories reduce the probability of encounters with vehicles. Status of Impact Negative. Degree of Confidence High; data from other study areas suggest that road mortality can lead to the local extinction of brown hyenas (e.g. Wolf Bay clan). Significance High; as mortality can have a long-term influence on clan structure and survival. Mitigation Enforcement of a strict speed limit. Awareness raising with drivers. Monitoring Recommendations Report all road mortalities to Namdeb, Ministry of Environment and Tourism and the Brown Hyena Research Project immediately. Recommended Mitigation Measures and Management Actions Impacts on brown hyenas regarding the mining process and seawall construction cannot be mitigated, but brown hyenas should be monitored to detect changes in behaviour in order to obtain reliable data for future similar mining operations. Ideally brown hyenas of the three different clans should be fitted with GPS telemetry collars, but this is extremely time consuming and costly and most probably not possible before construction commences. Low budget and less time consuming monitoring recommendations are as follows: The use of camera traps to establish an ID catalogue of resident hyenas and to determine brown hyena abundance and activity and changes therein, as well as to detect changes in home range locations; Regular spoor counts on EBay beach before, during and after construction and mining operations to detect changes in brown hyena activity in the affected area; Regular carrion counts at EBay beach, taking weather, ocean and seasonal differences into account. The rehabilitation of the beach area after mining is complete may mitigate long term or permanent impacts. Roads pose a threat to wildlife either through direct mortality (road kills), but also through disturbing wildlife and causing the fragmentation of habitat. At present only direct mortality can be recorded and to avoid road kills a strict speed limit should be enforced and the drivers should be made aware of the behaviour of wildlife species on roads as well as made aware of the importance of reporting wildlife mortalities (e.g. data collection: genetics, population parameter such as age, size etc.).

9 Conclusions and Recommendations The main potential risks of the proposed Elizabeth Bay Optimisation Study for brown hyenas are: Disturbance of brown hyenas on EBay beach through the mining process and seawall construction, Effects of mining operations on territory boundary on the southern end of EBay beach through the mining process and seawall construction, Loss of the beach area as a potential food source for brown hyenas through the mining process and seawall production, and Disturbance and/or mortality of brown hyenas through increased traffic (all options) due to the improvement of roads and the extension of the road network. To mitigate long-term and permanent impacts on affected brown hyena populations the beach area should be rehabilitated once mining is complete. Brown hyenas should be monitored through spoor counts and camera traps before, during and after the construction and mining phases to obtain reliable data about such impacts and to use these data in planning processes for future mining projects. References April, C., Craighead, F.L., Roberts, E.A. (2001). Bozeman Pass wildlife linkage and highway safety study. Proceedings of the Transportation Related Wildlife Mortality Seminar/Federal Highway Administration. Ruediger, B. (1996). The relationship between rare carnivores and highways. Proceedings of the Transportation Related Wildlife Mortality Seminar/Federal Highway Administration. Ruediger, B. (2000). The relationship between rare carnivores and highways: an update for the year Proceedings of the Transportation Related Wildlife Mortality Seminar/Federal Highway Administration. Wiesel, I., Maude, G., Scott, D. & G. Mills (2008). Hyaena brunnea. In: IUCN IUCN Red List of Threatened Species. Wiesel, I. (2009). Brown Hyena Movement, Behaviour and Abundance, and Implications for their Long-term Conservation within the Diamond Mining Area in the Southern Coastal Namib Desert. Annual Report 2009.