Status and distribution of the Mediterranean monk seal Monachus monachus on the Cabo Blanco peninsula (Western Sahara-Mauritania) in 1993–1994

The current geographical distribution of the Mediterranean monk seal Monachus monachus colony inhabiting the Cabo Blanco peninsula (Western Sahara-Mauritania) is described. Its distribution range has apparently not changed since surveys conducted in 1984–1988. Sightings of adults on the Tarf el Guerguerat coast, 20 km north of the known breeding caves, suggests the existence of other possible breeding groups further north. Two caves used by the seals are described for the first time. A review of historical trends in cave occupation by seals made it possible (1) to locate the so-called ‘maternity cave’, last reported in 1949; and (2) to establish that the colony, since its discovery, has occupied at least eight caves, five of which have collapsed. An index of population size based on counts of individuals of identified morphological types indicates that, during 1993–1994, the colony was composed of c.113–165 individuals (excluding pups), a larger number than previously assumed. Counting of seals at times of maximum haul-out is proposed as a tool to monitor population trends, although it is considered unreliable for estimating absolute numbers.     

Application of central-place foraging theory shows the importance of Mediterranean dehesas for the conservation of the cinereous vulture, Aegypius monachus

The dehesa (oak woodland) is an extensive agro-pastoral ecosystem characteristic of the Western Mediterranean countries which is suffering a great transformation process since 1950. Although its distribution largely overlaps with several endangered species, there is scarce information on how they use this human-transformed habitat. We studied the foraging habitat selection of one of them, the cinereous vulture Aegypius monachus. We radio-tracked 14 cinereous vultures in one of the largest European colonies from 1998 to 2000. Used and available habitats were compared at two scales using compositional analysis. Moreover, we developed a distance-based GLMM for assessing habitat selection in this central-place forager species, by taking into account the spatial distribution of habitat patches in relation to the location of the colony. Home ranges overlapped over a total surface of 592,527 ha around the colony, and both individual home ranges and travel foraging distances (mean 27.86 km, maximum 86 km) were larger during the breeding season. All cinereous vultures avoided agricultural lands within their home ranges throughout the year. Habitat use in relation to the distance to the colony pointed out that dehesas were positively selected in spite of being on average far away from the colony than other habitats, a result that was consistent among individuals and seasons. The cinereous vulture thus depends for its conservation not only on the protection of breeding areas, as has been so far considered, but also on the maintenance of well-conserved dehesas close to the colonies. Preserving the cinereous vultures could contribute to the economic sustainability of dehesas by attracting PAC funds for their traditional low-intensity exploitation. Although other species may also benefit from this study since cinereous vulture could be a “flagship” for the large-scale conservation of Mediterranean oak woodlands and associated biodiversity, more fine local management guidelines should be performed on the basis of studies on more sensitive species.     

The recent status of Monachus monachus, the Mediterranean monk seal

Mediterranean monk seals Monachus monachus (Hermann 1779) still live widely in their primaeval range around the Mediterranean and adjacent northeast Atlantic seas, but are now confined chiefly to remote cliffbound coasts and islets. Greatest numbers occur in the eastern Aegean sea. Total numbers are probably between 500 and 1000 with the population still declining. Neonates measure about 0·8 m length and weigh about 20 kg, while adults reach extreme sizes of 3m and 400 kg. The wide food spectrum of fish and cephalopods, probably reaching 5% of body weight per day as an optimum intake for adults, produces competition with fishermen. Seals damage nets and are shot, and are also caught inadvertently in various types of nets. Births extend from May to November with a peak in September. Human disturbance of reproductive sites at all seasons is believed to be seriously reducing the reproductive rate of monk seals. Efficient reproduction probably requires beaches as well as the caves mostly used at present. Individual travel can be several hundred kilometres and widespread similarity of colour patterns suggests that gene flow has not been interrupted in the past. A network of reserves is needed in existing and past habitat, which could be of value also to rare cliff-nesting sea birds. These core reserves should be totally free of human disturbance, but buffer zones are envisaged surrounding them, which could be used for viewing the animals.     

Status and conservation of the grey seal, Halichœrus grypus, in France

We investigated the status of the grey seal in the Molène archipelago, western Brittany, where a Marine National Park is planned. We combined regular censuses, photo-identification and satellite telemetry to investigate trends in grey seal abundance, site fidelity, individual movements and haulout site use. Individual movements and seasonal variations in abundance suggest that the seals used the Molène archipelago alternatively with other haulout sites of the South-west British Isles during their annual cycle. Nine out of 16 seals fitted with Satellite Relay Data Loggers (SRDLs) moved to the Isles of Scilly, English Cornwall, Wales or the Channel islands. On average the seals spent 85% of their time Near Haulout, 56.8% of which in the Molène archipelago. Overall the seals spent 66% of their tracking time within the boundaries of the Marine National Park. From 1997 to 2000 in the Molène archipelago, we observed a peak in number during the moulting season (mean = 49.8 seals) and a lower abundance during the breeding season (mean = 38.3 seals). The sex ratio was strongly skewed towards males during the moult (between 3.1 and 5.3-1), and was close to 1:1 during the summer. Inter-annual site fidelity outside the breeding season was very high, varying from 70% to 95% of identified seals, suggesting that the observed movements constitute rotations rather than random dispersion. From 1991/1994 to 1997/2000, the mean number of seals counted at haulout sites increased by 7%, close to the rates of increase observed in the core population of the British Isles at the same period. The Marine National Park may be too restricted for the overall conservation of the population but management plans should be aimed at preserving the characteristics of the habitat for the grey seal.     

Abundance of the Hawaiian monk seal in the main Hawaiian Islands

Most of the extant circa 1400 Hawaiian monk seals Monachus schauinslandi live in the Northwestern Hawaiian Islands (NWHI). However, an increasing number of sightings and births have recently occurred in the main Hawaiian Islands (MHI), where no systematic surveys of monk seals were conducted prior to 2000. We estimate that there were at least 45 seals in the MHI in 2000 and at least 52 in 2001, based on aerial surveys of all MHI coastlines, supplemented by sightings of seals from the ground. Moreover, annual births in the MHI have evidently increased since the mid-1990s. Weaned pups in the MHI are longer and have greater girth than those in the NWHI, perhaps reflecting greater per-capita abundance of prey resources. We think that Hawaiian monk seals have recently re-colonized the MHI, which were a very likely part of their historic range. Regardless, the MHI habitat appears to be favorable for continued increases of this endangered species.     

The grey seal (Halichoerus grypus) in Cornwall and the Isles of Scilly

Cornwall and the Isles of Scilly were explored for grey seal (Halichoerus grypus) breeding localities during the 1973 breeding season. The work invelved investigating many sea caves on the north coast of Cornwall, in addition to open beach and skerry sites. Pup production was determined by relating the number of pups produced in a sample period to the number produced in the same period (in another year) at Ramsey Island, Pembrokeshire. The all-age populations derived from these pup production estimates suggest that the number of grey seals in Cornish waters is about 250 and in Scilly about 120. Haulouts of several hundred animals seen in Scilly outside the breeding season almost certainly breed elsewhere.     

Translocation as a tool for conservation of the Hawaiian monk seal

The deteriorating demographic status of the endangered Hawaiian monk seal has motivated renewed and expanded proposals for conservation action, including translocation of seals to improve survival. Over the past three decades, numerous monk seal translocations have been conducted with a variety of objectives, including mitigating shark predation and conspecific male aggression, reducing human–seal interactions, and taking advantage of favorable foraging habitats to improve survival. Here, we analyze our cumulative experience with translocation of Hawaiian monk seals. We found a strong correlation between the time seals remained in the vicinity of the release site and their age. Recently weaned pups (with little or no at-sea foraging experience) exhibited high fidelity to release sites commensurate with that shown by untranslocated pups to their birth location. In contrast, juvenile and adult seals tended to stray from their release locations farther and sooner. Nevertheless, when 21 adult male seals were moved more than 1000 km from Laysan Island in the Northwestern Hawaiian Islands (NWHI), to the main Hawaiian Islands (MHI), they subsequently dispersed among the MHI; however, only one was observed to return to the NWHI. Translocated seals appeared to survive at rates comparable to seals native to the release site. Outcomes suggest that in most cases the intended objectives of translocations were achieved. Except for one notable case, translocations within the MHI to arrest human–seal interactions were mostly unsuccessful. These findings will be essential for informing successful large-scale translocation plans in the future.     

Life expectancy of monk seal colonies in Greece

A calculation of the life expectancy of the few remaining colonies and individuals of the Mediterranean monk seal Monachus monachus in Greek waters has been made. This is based on the 1977 census of the seal population by Vamvakas et al. (1978) with corrections based on observations by the author, and application of the rate of decline of all populations of seals by J. Boulva (1978). The results indicate that no seals will be left in Greece by the year 2000, and many colonies will have ceased to exist by 1990. The colonies with the greatest life expectancy are located in the Ionian sea, the Sporades, and in islands around Crete.The discouraging results of the calculations emphasize the urgency of immediate action to preserve the few remaining seals in Greece.     

Phocine distemper virus in the North and European Seas - Data and models, nature and nurture

Two outbreaks of phocine distemper have severely affected harbour seal (Phoca vitulina) populations in European and UK waters. The first occurred in 1988 when the causative virus was identified as a new member of the genus morbillivirus. The second outbreak in 2002 was first detected on the same Danish Island of Anholt and involved similar populations and geographical locations. However, despite the obvious similarities between the epidemics, differences in viral transmission and case mortality were found. Harbour seals are highly susceptible to infection while sympatric grey seals (Halichoerus grypus) are resistant but could be important asymptomatic carriers of the disease. Arctic phocid seals remain the most likely source of the virus and grey seals could be the link between these primary hosts and the harbour seal populations further south. Future epidemiological models should therefore consider including multiple host species. The future conservation and management of harbour seal populations vulnerable to PDV relies on the ability to accurately predict the long-term impact on population abundance and distribution. Although knowledge about the behaviour and pathogenesis of the virus has increased substantially and data on host movements and contact rates are accumulating, studies into the determinants of the host range have lagged behind. The development of more realistic epidemiological models should be combined with studies into the factors controlling species and individual susceptibility. Assessing the risk of infection to endangered but currently unexposed potential host species (such as the Hawaiian monk seal, Monachus schauinslandi) is essential for guiding potential conservation management options, such as vaccination     

Designing a network of marine reserves in the Mediterranean Sea with limited socio-economic data

The present study is the first to determine priorities for the location of marine reserves using spatial prioritization software in the eastern Mediterranean Sea. We used biophysical data from visual census surveys on: fish species abundance, presence of various habitat types, and percent coverage of seagrasses and canopy algae. Efficient conservation planning requires spatially explicit information on how proposed management will affect stakeholders, which in this region was very limited. We created novel socio-economic cost indices to account for fisheries and tourists. Our fishing metrics were based on fisher behaviour including information on the location of ports and areas often inaccessible to fishers due to high wind exposure. We developed a cost index for tourism based on the availability of beds for tourists. We examined how the spatial priorities for marine reserves varied using different combinations of these socio-economic cost metrics. We found about 17% of sites were a high priority regardless of which cost metric was used. We also compared, for the first time in the Mediterranean, our results devised using systematic conservation planning approaches with priorities developed by two non-systematic methods, the Natura 2000 proposed marine reserves and sites that local fishers proposed for protection. Only a few sites identified by our approach were the same as those recommended as part of Natura 2000 or the fishers’ proposals. This suggests that much more work is needed to harmonise existing proposals with the principles of efficient systematic conservation planning.     

Hybridization and conservation of Mediterranean orchids: Should we protect the orchid hybrids or the orchid hybrid zones?

Natural hybridization between plant species often occurs in disturbed habitats and it is generally considered a threat for rare and endangered species. A different situation occurs in Mediterranean food deceptive orchids, where hybridization is a common phenomenon, as a natural consequence of their unspecific pollination system.Here, we present molecular and ecological evidence from a hybrid zone between Orchis mascula and O. pauciflora in order to address the consequences of hybridization on local orchid evolution and to assess conservation priorities for hybrids and hybrid zones in orchid conservation programs.We find that, although hybrids among the two target taxa are formed relatively frequently, hybrid zones often consist of F1 individuals, whereas backcrosses and later generation hybrids appear to be either rare or absent, presumably as a consequence of post-zygotic reproductive barriers acting in these food-deceptive orchids. Experimental evidence further indicates that hybrids are less fit than the parental species in attracting pollinators and that parental taxa exhibit higher or similar fitness in sympatry compared to allopatric populations. Since introgression is not frequent as indicated by molecular analyses, fitness and phenotypic trait differences observed among sympatric and allopatric populations of the parental taxa may be a consequence of pollinator-mediated selection.Our experimental data confirm that hybridization is a natural phenomenon in food-deceptive orchids and that it does not pose a threat to their survival. Furthermore, sympatric zones provide the stage for evolutionary processes in orchids, and this peculiarity should be taken into account when devising orchid conservation strategies.     

Conservation implications of the distribution of genetic diversity at different scales: a case study using the marsh fritillary butterfly (Euphydryas aurinia)

In the UK, Euphydryas aurinia exists in fragmented habitat patches, and undergoes population fluctuations as a result of a larval parasitoid. Its range is declining in the UK and conservation is thought to require a landscape approach since populations spread over large areas in some years and contract to core breeding patches in others. We examined populations at a range of geographic scales using allozyme electrophoresis to look for evidence of gene flow and differences in genetic diversity among populations. Nationally, our F_ST value was 0.1542 but between population groups within the suspected colonisation range of the butterfly (ca. 20 km), F_ST values were not significantly different from zero. Genetic diversity in terms of number of alleles and heterozygosity was reasonably high in natural populations (H_e=0.267) but low in an introduced, isolated population. We infer that migration between closely spaced subpopulations (in a metapopulation) maintains a high genetic effective population size (large number of individuals in a population that contribute genes to the next generation) which offsets any local reductions in population numbers due to stochastic extinctions or parasitoid effects. We therefore conclude that effective conservation of the species must seek to provide networks of suitable habitat for groups of subpopulations, rather than maintaining habitat for isolated populations.     

Seal–fishery operational interactions: Identifying the environmental and operational aspects of a trawl fishery that contribute to by-catch and mortality of Australian fur seals (Arctocephalus pusillus doriferus)

Australian fur seals are known to interact directly (i.e. operational interactions) with trawlers fishing in the winter blue grenadier trawl fishery of western Tasmania, Australia. The purpose of this study was to identify the environmental and operational aspects of the fishery that were associated with increased numbers of seals observed at the surface. The incidence of net entry was determined in order to establish the effectiveness of the currently used Seal Exclusion Device (SED) at reducing by-catch and mortalities. In addition, the stage and depth at which seals were at greatest risk of entering the net at depth and becoming by-catch were also identified.

An increase in seal numbers observed at the surface is assumed to be proportional to the increased risk of by-catch and mortality incidences at trawlers. The most important subset of environmental and operational factors for predicting the number of seals observed at the surface both in the fishing ground in general and during fishing operations were identified using Generalised Linear Modelling. The final model yielded a significant result (R² = 0.63, P < 0.01, n = 149) and indicated that the number of seals observed increased when weather conditions deteriorated, particularly when barometric pressure decreased and when swell height and visibility increased. Vessel operations also influenced the number of seals observed; seal numbers increased when the number of nearby vessels and trawl frequency increased, but decreased when vessel speed increased. Seal numbers also increased as the distance from the nearest breeding colony and haul-out site decreased.

Seal numbers at the surface generally increased steadily during trawling operations (n = 475), although brief declines were noted during shooting and hauling phases. Sub-surface net interactions were also examined using a submersible video camera unit. Seal activity at depth was converse to that observed at the surface, with increased seal numbers noted during shooting and hauling, suggesting that seals dived to forage on fish in the submerged net.

All seal by-catch occurred during the day and almost half occurred during shooting. Mortalities were significantly higher during shooting compared with hauling (Fishers exact test: coef. = 0.65, P < 0.05). However, mortality rates were similar between tows with the Seal Exclusion Device (SED) attached and those without (Fishers exact test: coef. = 0.07, P < 0.99). Only one seal was detected entering and exiting the net mouth during monitored tows, suggesting that the recently observed reduction in by-catch levels (and mortalities) may not necessarily be attributed to the introduction of the Seal Exclusion Device. Seal by-catch recorded during hauling typically occurred when haul speeds exceeded minimum average swimming speeds for fur seals.

Recommendations based on these findings have been made to assist with the future management of fur seal populations that interact with trawl fisheries.     

Assessing habitat use of the endangered marine mollusc Patella ferruginea (Gastropoda, Patellidae) in northern Africa: preliminary results and implications for conservation

The limpet Patella ferruginea Gmelin, 1791, endemic to the Mediterranean, is the most endangered marine species on the list of the European Council Directive 92/43/EEC on the Conservation of Natural Habitat of Wild Fauna and Flora (1992). Its Mediterranean range has progressively contracted to a few restricted areas and the species is now threatened with extinction. Seventeen stations were sampled along the littoral zone on the coast of Ceuta, North Africa, for quantifying environmental factors (water movement, siltation and suspended solids), and 70 transects were selected for P. ferruginea sampling. The study revealed the presence of a well-established population of P. ferruginea with values of density and size of 0.67 individuals m⁻¹ ±0.96 and 48.94 mm±11.61 respectively (mean±standard error of mean). The biggest densities of P. ferruginea were found inside the harbour of Ceuta. The limpets were more abundant on artificial harbour stones than on natural rocky shores, and the areas under the highest human pressure were characterised by the lowest densities and the smallest specimens probably due mainly to the predation for food and fishing. Human pressure is probably the main contributing factor to the currently endangered status of P. ferruginea. Programmes of environmental education to avoid its collection for fishing, food or for fun as decorative objects should be conducted, and further experimental studies dealing with the reproductive biology of this species are needed to properly assess the future programmes of conservation.     

Two genetically distinct units of the Chinese sika deer (cervus nippon): analyses of mitochondrial DNA variation

Chinese sika deer, Cervus nippon, are currently threatened by habitat loss, fragmentation and human hunting, which has led to the extinction of three subspecies in the wild. The remaining subspecies subsist in the narrow regions of Jilin, Heilongjiang, Sichuan, Gansu, Jiangxi, Anhui, and Zhejiang provinces. In order to design effective conservation strategies for the Chinese sika deer, we have investigated genetic diversity, population structure and gene flow in the Chinese sika deer populations by analyzing ≈995 base pairs of the mitochondrial DNA (mtDNA) control region in 59 individuals sampled from the northeast of China, Sichuan, Jiangxi and Zhejiang. Chinese sika deer exhibited low mtDNA diversity and high gene flow among the four populations, and showed no strong geographical structure. The analyses of mtDNA variation among individuals of sika deer identified only two main phylogenetic groups even though three subspecies were sampled. These data singles out the Zhejiang population as being highly genetically distinct and worthy of separate conservation consideration. Therefore, it is recommended that a breeding program for the Zhejiang population be established.     

Non-commercial collection of spur-thighed tortoises (Testudo graeca graeca): a cultural problem in southeast Spain

Collecting tortoises for the pet trade is one of the factors threatening species of Testudo in the Mediterranean area. The collection of Testudo graeca graeca for pets is described in southeast Spain, where the main European population of this subspecies coincides with an area where keeping tortoises in captivity is a long-established custom. This present paper, based on inquiries made to children, reveals that this practice continues to be a common activity, and estimates a captive population in the order of tens of thousand of tortoises. Tortoises are collected as a result of chance encounters with wild animals by local inhabitants, and without any commercial objectives. The captive breeding and the release of tortoises without any institutional control is also common. These activities could be an important threat for the species. Implications for conservation are discussed and a critical review of the conservation strategies developed in relation to this threat (trade control and re-introduction programmes) are presented. We suggest that environmental education programmes are necessary to reduce casual collection and to change the social perception of tortoises as pets.     

Comparative use of vendace by humans and Saimaa ringed seal in Lake Pihlajavesi, Finland

The Saimaa ringed seal, Phoca hispida saimensis, is one of the most endangered ringed seals in the world. Its total population consisted of 240 adult seals in the Saimaa lake complex in 2000. We estimated the amount of vendace, Coregonus albula, consumed by the seals and compared it with fishermen’s vendace catches and our vendace stock estimates in Lake Pihlajavesi, Finland. Our study area was the habitat of 43 mature seals and 17 immature seals as well as 12 pups in 2001. Five commercial two-boat trawlers fished in the area. Vendace stock size was estimated at 660 tonnes i.e., 12 kg ha⁻¹ in the study area in August-September 2001. The vendace catch by fishermen was approximately 250 tonnes, and the vendace consumption by the Saimaa ringed seal was estimated at 68 tonnes in 2001. We estimated that during the whole year seals ate approximately 8% of the vendace spawning stock biomass in the area while fishermen caught 30% of it. The seals and the fishermen together used less than 10% of the available vendace biomass in each month. Fishing pressure on the vendace stock was highest in August-October. The amount of vendace eaten by the seals exceeded the vendace catch in fisheries only in December-April. In periods of low vendace density, the seals can consume a higher proportion of the stock and reduce the catch per unit of effort in fisheries. However, our assumption that seals fed only on vendace should be considered as an extreme scenario when considering the conflict between fisheries and the seal.     

Experimental management of Mediterranean temporary pools for conservation of the rare quillwort Isoetes setacea

Mediterranean temporary pools represent unique species-rich habitats with many rare and endangered species. The Roque-Haute Natural Reserve is one of the few sites in France with Isoetes setacea Lam., a very rare Mediterranean quillwort, considered as a keystone species determining a priority habitat for the European Union. Land uses changes have favoured the invasion of the pools by several shrub and tree species (e.g., Ulmus minor, Fraxinus angustifolia subsp. oxycarpa). Clearing shrubs in an experimental area of one pool resulted in the increase of I. setacea as compared to control, combining a higher cover in previously occupied quadrats and more quadrats occupied. Litter accumulation had a negative effect on the population of Isoetes but this effect was detectable only in the cleared area. Light attenuation was shown experimentally to be detrimental to the vegetative and regenerative production of I. setacea. Clearing of the shrubs and removal of the litter led to an increase in the I. setacea populations and therefore appears to be an effective technique for restoring these plant communities invaded by shrubs. Long-term shrub control should be ensured by reintroducing sheep grazing in order to enhance the sustainable conservation of this oligotrophic habitat.     

Species richness in Mediterranean agroecosystems: Spatial and temporal analysis for biodiversity conservation

We used dung beetles as an indicator group to identify the most important habitats for biodiversity conservation in a Mediterranean traditional agroecosystem. The relationships between traditional grazing and farming activities and biodiversity were analysed by comparing species richness and temporal turnover across three different habitat types, defined according to vegetation structure and human land use. In this study, both spatial (landscape, among-habitats) and temporal (intra-annual, seasonal) analyses were contemplated at mesoscale.The measurement and use of temporal beta diversity (i.e. an index of temporal species turnover) in conservation biology showed that it is a simple method to characterize and compare different habitat species-assemblages, particularly when time seems to be a significant factor in explaining biodiversity features.Our results showed open mosaic areas as the richest and most temporally heterogeneous habitats. We suggest the maintenance of traditional human activities carried out in these areas, since they have been a significant diversification agent, to avoid the loss of the high Mediterranean biological diversity.