|
Fa, J. E., Sharples, C. M.,
Bell, D. J., and DeAngelis, D. 2001. |
|
We developed an individual-based model of Rabbit Viral Hemorrhagic Disease (RVHD) for European wild rabbits (Oryctolagus cuniculus L.), representing up to 1000 rabbits in four hectares. Model output for productivity and recruitment matched published values. The disease was density-dependent and virulence affected outcome. Strains that caused death after several days produced greater overall mortality than strains in which rabbits either died or recovered very quickly. Disease effect also depended on time of year. We also elaborated a larger scale model representing 25 km2 and 100,000+ rabbits, split into a number of grid-squares. This was a more traditional model that did not represent individual rabbits, but employed a system of dynamic equations for each grid-square. Disease spread depended on probability of transmission between neighboring grid-squares. Potential recovery from a major population crash caused by the disease relied on disease virulence and frequency of recurrence. The model's dependence on probability of disease transmission between grid-squares suggests the way that the model represents the spatial distribution of the population affects simulation. Although data on RVHD in Europe are lacking, our models provide a basis for describing the disease in realistic detail and for assessing influence of various social and spatial factors on spread. |
|
Fa_et_al_2001_Model_of_rabbit_viral_haemorrhagic_disease.pdf |
|
Farfán, M. A., Vargas, J. M., Real, R., Palomo, L.
J., and Duarte, J. 2004. |
|
To analyse the population structure and reproductive biology of the Iberian hare Lepus granatensis Rosenhauer, 1866, 498 hares (264 males and 234 females) were collected in monthly samples from October 1998 to September 1999. Females reached larger sizes than males, with approximately 400 g difference in body mass on reaching sexual maturity. The total sex ratio was 1:1, with a bias in favour of males in winter. Sexually active males and females appeared in every month but August, when no sexually active female was found. Births occurred in every month and were more frequent between March and July. Seasonal variation in kidney fat index (KFI) followed a similar pattern in males and females, with an increase in mid-autumn and a decline at the end of winter. Reproductive activity appeared in every month, with a maximum from February to June. Reproductively hyperactive females (simultaneously pregnant and nursing) appeared in every month except in January, with a first peak in March and a second lower peak in May-June. Litter size fluctuated between 1 and 7 leverets. The most frequent gestations involved 1 or 2 foetuses. The mean annual litter size was 2.08 and the average number of litters per productive female per year was estimated to be 3.48. The maximum productivity was recorded between March and May. The total annual production of young per adult female was estimated to be 7.21. The minimum annual survival rate of young was 27.91%. On the basis of these results we propose to maintain the limit of the hunting period between October and December. We discuss the relationship between the low young/adult ratio obtained and the hunting method used. |
|
Farfan_et_al_2004_Population_parameters_and_reproduction_of_Iberian_hare.pdf |
|
Fedriani, J. M., Palomares, F.,
and Delibes, M. 1999. |
|
Previous studies carried out in the Donana National Park reported that red foxes (Vulpes vulpes) were killed by Iberian lynxes (Lynx pardinus), whereas similar-sized Eurasian badgers (Meles meles) were not. Therefore, we predicted that fox would avoid lynx predation risk by niche segregation whereas we did not expect such a segregation between badger and lynx. As an approach for evaluating our predictions, we compared their diet, activity patterns, and habitat use in an area of Donana where the three carnivores are sympatric. Lynxes preyed almost uniquely on European rabbits (Oryctolagus cuniculus), and though badgers and foxes were omnivorous, rabbits also were a major prey, resulting in high overlaps throughout the year. However, badgers preyed largely on small rabbits, whereas lynxes and foxes preyed mainly on medium-sized rabbits. There were also interspecific differences in activity patterns. Maximum levels of activity among lynxes were during sunrise and dusk (49±67%). Foxes were most active during dusk and night (34±67%), and badgers were mainly nocturnal (53±87%). Though there were seasonal differences in the amount of activity of each species, specific activity patterns changed little throughout the year. There was a strong difference in annual habitat use by the three species (P < 0.0001). Lynxes used mainly the Mediterranean scrubland during both the active (PMAX) and the resting (PMIN) periods. During PMIN, foxes used the Mediterranean scrubland intensively (40% of locations on average), but during PMAX, they used the pastureland much more intensively despite this habitat being poorer in their main prey (rabbits). As a consequence, foxes and lynxes exhibited segregation in their habitat use during the active period. Badgers also used the Mediterranean scrubland intensively, especially during PMIN. There were no seasonal differences in habitat use for lynx and fox, but there was for badgers (P < 0.015). Within the study area, the three species selected habitat suggesting they were sensitive to factors such as vegetation and prey abundance. However, in general, carnivore habitat use did not correlate with rabbit abundance. We propose that foxes avoided lynxes by using, during activity, habitats not frequented by lynxes, and that a low predation risk associated with the distinctive foraging mode of badgers may facilitate its coexistence with other carnivores. |
|
Fedriani_et_al_1999_Niche_relations_among_three_sympatric_carnivores.pdf |
|
Fernández, J. 2004. |
|
A group of researchers receives the prize of the European Society for Veterinary Pathology for their studies on the Iberian lynx. |
|
Fernandez, N. and Palomares, F.
2000. |
|
We investigated the preferences shown by Iberian lynx (Lynx pardinus) for structures and sites for denning in Donana National Park. Lynx proved to be highly selective regarding the features of the natural structures selected, but their preferences concerning the characteristics of the habitat for the denning sites were not so evident. All located litters were born inside hollow trunks with very large cavities (mean area=0.40 m2). Later, they were moved into bushes characterised by their large size (mean area=201.7 m2) and protective capabilities. We used logistic regressions to explore the relative strength of association between the selection of dens, the characteristics of their structure and those of the habitat around dens. The regressions indicated that the physical nature of dens was more important for breeding lynxes than habitat features (like prey densities or structure of vegetation). Preserving old growth habitats is important for the conservation of the endangered Iberian lynx because they provide suitable breeding structures. |
|
Fernandez_&_Palomares_2000_Breeding_den_selection_by_Iberian_lynx.pdf |
|
Fernandez, N., Palomares, F.,
and Delibes, M. 2002. |
|
The use of breeding dens and the early kitten development was studied in a free-ranging population of Iberian lynx Lynx pardinus. Radio-tracking of female lynx allowed intensive monitoring of three litters during 1997, and additional data to be obtained from nine other litters in the previous 4 years. Females gave birth a maximum of one litter per year in spring; nine of the 10 births were recorded between the last 2 weeks of March and the first days of April. Kittens were born semi-altricial and reared for nearly 20 days in secluded hollow trunks. Afterwards, they were moved between different bushes, which served as auxiliary dens, where they began to develop walking and senses. Kittens first consumed meat at the age of 4 weeks, although they were not fully weaned until they were at least 10 weeks old. At the age of 2 months, kittens began to leave the dens, accompanying their mothers on outings. It is suggested that the pattern of den use was related to the stage of kitten development, to fulfil the kittens' need for both protection and space as they grew. Data on kitten denning and development should be accounted for in in-situ and ex-situ conservation programmes for this endangered felid. |
|
Fernandez_et_al_2002_Denning_and_kitten_development_in_the_Iberian_lynx.pdf |
|
Fernandez, N., Delibes, M.,
Palomares, F., and Mladenoff, D. J. 2003. |
|
Empirical landscape habitat models are valuable tools for addressing species conservation issues in heterogeneous landscapes. These have been particularly useful for animal populations requiring extensive areas, like large mammalian carnivores. Although models are scale-dependent, they are often based exclusively on coarse-grained information on landscape structure and species distribution. However, accurate discrimination and quality assessment of breeding habitats may require more detailed information on both individuals' habitat use and landscape patterns. Here, we modeled breeding habitat for the Iberian lynx (Lynx pardinus), an endangered specialist of Mediterranean native ecosystems, in a human-dominated landscape. For this, we used radiotelemetry data on breeding individuals and fine-grained landscape variables obtained over an areal extent encompassing an entire lynx metapopulation. In addition, we restricted the study domain to areas of potential presence within this extent based on previous habitat analyses. This fine-scale landscape analysis and design aimed to test whether it was possible to obtain detailed inferences on breeding habitat distribution and quality within more coarsely defined habitats that only indicate where the species can be found. Landscape composition factors (i.e., fine-grain variables of landscape pattern within territories) and context factors (variables on geographical location of territories) were combined in different candidate habitat models. These reflected various hypotheses involving territory presence and size, including vegetation structure characteristics, landscape heterogeneity and complexity, favorable prey habitat, and human disturbance. The best approximating model for territory presence included only one landscape composition variable, namely, density of ecotones between scrubland and pastureland, which favored presence. For this model, classification accuracy was >80% in 94% of cross-validation tests performed. The best approximating model for territory size explained 65% of the variation in size and included also density of ecotones, plus mean coverage of tall shrubs within territories; both correlated negatively with size. We show how these predictors are also related to prey density and suggest that this low-hierarchical-level relationship between the prey and patterns of the landscape can be interpreted as a likely mechanism explaining breeding habitat distribution and quality at a higher level. Our approach shows the potential of finescale landscape analysis to understand patterns of breeder abundance, and to better manage population viability of threatened species in human-populated areas. |
|
Fernandez_et_al_2003_Identifying_breeding_habitat_for_the_Iberian_lynx.pdf |
|
Ferrand de Almeida, F. 1988. |
|
Several animal species are threatened in Portugal by the increasing number of industrial plants, by destruction of natural habitats, illegal hunting and pollution. This article takes four examples and shows the influence of these factors on their populations. |
|
|
||
|
Ferreira, C. 2003. |
|
|
|
||
|
© C. Ferreira |
||
|
The wild rabbit (Oryctolagus cuniculus algirus) plays a vital role in Mediterranean ecosystems as an important prey for a wide spectrum of predators, such as the Iberian lynx (Lynx pardinus) and the Imperial eagle (Aquila adalberti), and as one of the most important game species. In the Iberian Peninsula, wild rabbit populations have been declining over the last decades due to several factors: habitat fragmentation and deterioration, excessive hunting, and incidence of two viral diseases (Myxomatosis and Viral Haemorrhagic Disease). Efforts to restore former numbers of rabbit populations have concentrated on the implementation of habitat management techniques, such as the opening of green pastures and the installation of artificial warrens. In the Natural Park of Sudoeste Alentejano and Costa Vicentina (South Portugal) a total of four areas have been selected to act as experiments in a work that aims to study the effect of habitat management techniques on the relative abundance of wild rabbits and on their diet during an annual cycle: two areas function as managed areas; the other two were chosen to act as controls, with no implementation of habitat management measures. Relative abundance was assessed by counting pellets in sampling points established along three transects defined for each of the four study areas. The diet of the wild rabbit in each area was determined through the micro-histological analysis of pellets and by comparing epidermal fragments with a reference collection. The results indicate that, over the study period, pellet densities are higher in the managed areas when compared to the control ones. There are also significant differences between areas and months within each study area. The analysis suggests that there are significant differences supporting a global positive impact of the habitat intervention, even though no significant differences between control and managed areas were specifically found. The results confirm the generalist disposition of the wild rabbit, which adapts its feeding strategy to the quantity and quality of the resources available. In general, the Gramineae was the most consumed plant group all over the year and in all study areas. In the managed areas, Dactylis glomerata played an important role, particularly in autumn and spring. This plant species occurs widely in the control areas, where it's also selected, indicating a strong preference that could be associated with its high nutritive value. In the control areas, however, it is evident the selection of alternative species, especially in the summer, such as Erica sp., Thymus sp., Cistus ladanifer and Cistus salvifolius, which present lower nutritive value. The most consumed parts of the plants were the leaves (> 50%) in all four areas, even though there was a clear preference for reproductive parts, such as flowers and inflorescences, dirung the reproductive period. The implementation of habitat management techniques seems to have been beneficial to the rabbit population, especially through the creation of new feeding areas. |
||
|
Ferrer, M. and Negro, J. J. 2004. |
|
Despite recovery plans, the Spanish Imperial Eagle (Aquila adalberti) and the Iberian lynx (Lynx pardinus) are in danger of extinction. These two flagship species tend to occur in pristine Meditteranean forests, and both prey preferably on the rabbit (Oryctologus cuniculus). Spanish lynxes and eagles have sister species in continental Europe, the Eurasian lynx (Lynx europeaus) and the Eastern Imperial Eagle (A. heliaca), respectively. Recent genetic evidence indicates that these two pairs of species started to diverge from their ancestor species slightly less than 1 million years ago, when the longest-lasting Pleistocene glaciations covered Europe. We hypothesize that the Iberian lynx and the Spanish Imperial Eagle emerged as separate species in the Pleistocene refugia of southern Spain, where they hunted yet another locally evolved species, the rabbit, on which they have become dependent for survival. Two large predators that emerged at the same time may go extinct simultaneously because of their inability to shift to alternative prey. Many other relict species, including numerous species from oceanic islands, have naturally small populations because of evolutionary constraints and are permanently threatened with extinction. Recovery plans aimed at putting these species out of danger are unrealistic, as their populations are and have been chronically scarce. We suggest that what these species need are maintenance plans designed to buffer population declines due to either stochastic or human-induced events. A metaphor for this would be "emergency care units" for conservation. |
|
Ferrer_&_Negro_2004_Near_extinction_of_two_European_predators.pdf |
|
Ferreras, P. 2001. |
|
Among the factors threatening the Iberian lynx (Lynx pardinus) (the most endangered species of all the Felidae), loss and fragmentation of its habitats are probably the most important. Connectivity between the remaining populations in the predominantly fragmented landscapes is a key factor in the dynamics and persistence of metapopulations. Based on the data collected during a long-term study on the ecology of this species in a small and fragmented population in SW Spain, I analyse the factors affecting connectivity between the two main sources and the rest of local populations. Connectivity was estimated as the proportion of dispersers from a source that reached a given subpopulation. Among the explanatory variables considered, only distance (both straight and effective distance, which takes into account habitat quality between local populations) and location of the source were clearly related to connectivity. Some other variables describing landscape features separating sources and target subpopulations (proportion of unsuitable habitats, patch cohesion, size of targets, overall size of subpopulations closer than the target) were not related to connectivity. Differences in the landscape surrounding sources help to explain the different connectivity from the two sources. An asymmetrical connectivity between the two sources and populations surrounding them (north and south) is likely explained by the configuration of habitats encountered by dispersers, which force those from one source to behave as crossers of unsuitable habitats. These results have consequences for the conservation of the Iberian lynx populations and for ecologically similar species. Distance, the factor most affecting connectivity, is difficult to manage, although at least size and configuration of usable patches can be modified. Connectivity could also be improved through recovery of habitats with cover, suitable for dispersing. Reduction of mortality risks would also enhance connectivity indirectly, by allowing longer times and larger areas covered during dispersal. In the case of the study population, it is urgent to promote connectivity with other Iberian lynx populations due to genetic consequences of small population size and effective isolation. |
|
Ferreras, P., Aldama, J. J.,
Beltran, J. F., and Delibes, M. 1992. Biol. Conserv. 61: 197-202. |
|
Data are presented on mortality rates of the Iberian lynx Felis pardina in Doñana National Park and the surrounding area in southwestern Spain, collected from 1983 to 1989. Data from radio-tagged lynxes and records of lynx mortality were used to assess causes of death. Annual mortality rate, estimated by using Heisey and Fuller methodology, was 0.37. Human activities were the main cause of lynx mortality in this mainly fully protected area, either directly (illegal trapping: 41.7%; road traffic: 16.7%; hunting with dogs: 8.3%) or indirectly (artesian wells: 8.3%). Only 8.3% of the annual mortality can be related unequivocally to natural causes. Sex, age, social status, year, and home range situation influenced mortality rates. The trend of this lynx population during the seven years of study revealed serious threats to its survival. This case study exemplified how a small population can approach extinction because of increased mortality due to habitat fragmentation, despite full protection of the main portion of its range. |
|
Ferreras, P., Aldama, J. J.,
Beltran, J. F., and Delibes, M. 1994. |
|
A combination of the dissociative anesthetic ketamine hydrochloride (KH) and the sedative hydrochloride (XH) was used to immobilize 31 Iberian lynx (Felis pardina) 45 times at Donana National Park, Spain. A mean (+/-SE) dose of 4.6 (+/-0.2) mg/kg KH and 4.0 (+/-0.2) mg/kg XH resulted in mean (+/-SE) induction time of 5.6 (+/-0.3) min and mean (+/-SE) first reaction time of 59.3 (+/-6.5) min. Convulsions occurred four times (9%), but with no noteworthy consequences. |
|
Ferreras, P., Beltran, J. F.,
Aldama, J. J., and Delibes, M. 1997. |
|
The spatial organization of the endangered Iberian lynx, Lynx pardinus (Temminck, 1827), was studied in Doñana National Park, south-western Spain, between 1983 and 1992. Thirty-six individuals (19 males and 17 females), including 24 adults (13 males and 11 females) were radio-tracked, providing 13,950 locations during 17,111 radio-tracking days. Iberian lynxes were essentially solitary (95.9% of simultaneous locations apart) and interactions were restricted to rearing activities by females. Adult associations were uncommon. Seasonal (four months) home ranges were larger for adult resident males (10.3 +/- 1.9 square km; n=5) than for females (8.7 +/- 2.4 square km; n=5). Lynxes used a central portion of the home range intensively ('core area', 50% Harmonic Mean) with similar size for males (3.7 +/- 0.7 square km) and females (3.2 +/- 0.8 square km), representing, on average, a 37.6 +/- 1.5% and 36.6 +/- 4.5% of male and female home ranges, respectively. Intrasexual home-range overlap was usually low between same-sex neighbours (15.1 +/- 6.6% males and 22.1 +/- 3.3% for females), but some instances of high overlap (>25%), both among males and females, were recorded, corresponding to spatial interactions between neighbours which usually ended with the displacement of one of the contenders. Core areas were mainly exclusive except during these spatial interactions. Actual fights resulting from these interactions seem more frequent than previously reported for other medium-sized solitary felids, likely promoted by high competition for optimum territories due to saturation of the population. The Iberian lynx spatial organization in Doñana works as a land tenure system, as described for other solitary felids. Although the mating system tends to monogamy, with male home range overlapping mainly that of one female, individual variations to polygygy were also found. |
|
Ferreras_et_al_1997_Spatial_organization_of_the_Iberian_lynx.pdf |
|
Ferreras, P., Gaona, P.,
Palomares, F., and Delibes, M. 2001. |
|
Mangers trying to preserve populations of endangered carnivores are often forced to choose between restoring habitat to allow larger breeding populations or reduce risks of mortality to increase survival rates. We modelled the viability of a metapopulation of the Iberian lynx (Lynx pardinus) under several scenarios (habitat restoration, anti-poaching, reduction of road kills) in a real landscape to evaluate their relative effects. Increasing carrying capacity was highly effective when performed on the local populations that acted as sources but had no effect when carried out in the sinks. Realistic scenarios consisting of partial removal of the human-related mortality (assuming additive effects of causes) predicted high risk of extinction. When combined, the effects of both management options are highly dependent on where they are carried out. If the sinks are the only targets of carrying capacity enlargement, a complete removal of human-caused mortality is required, whereas increases in the carrying capacity of sources are always effective. The metapopulation risk of extinction decreases dramatically (from 45.5% to 2.1% in 100) if connectivity among source populations can be improved. According to our work, only a detailed knowledge of the spatial and demographic structure of the populations, combined with simulations of realistic situations, can help managers to select the a priori optimal strategy, which probably combines different management options. |
|
Ferreras_et_al_2001_Viability_analysis_for_the_Iberian_lynx.pdf |
|
Ferreras, P., Delibes, M.,
Palomares, F., Fedriani, J. M., Calzada, J., and Revilla, E. 2004. |
|
Most studies on the causes of animal dispersal focus on species of birds or small mammals, but there are few such studies on solitary carnivores. A complete picture of the causes of animal dispersal is not possible without considering cases on a representative set of animals. The Iberian lynx is a medium-size, solitary carnivore that inhabits metapopulations, where dispersal plays a prominent role. Between 1983 and 1998 we studied the proximate and ultimate causes of dispersal in Iberian lynx in the Doñana metapopulation (southwestern Spain), based on radio-tracking of 49 individuals. Saturation of limited breeding areas in this small population leads to high dispersal rates in both sexes. Most lynxes dispersed from their natal area between 12 and 24 months of age. Males younger than 1 year old tended to disperse in a higher proportion than females of the same age. However, high dispersal rates for both sexes by the age of 2 years and the lack of differences in the dispersal distances do not support inbreeding avoidance as an ultimate cause of dispersal. Dispersal mainly started between January and June (24/29 cases), when most social interactions occur, which supports the social subordination hypothesis. Lynxes left the natal range at an earlier age from the local population with higher density, which supports intraspecific competition for resources as a cause for dispersal. However, prey seems not to be the limiting resource because dispersal mostly started during the season of increasing prey density, and individual probability of dispersal increases with prey density in the natal area. Dispersers suffered higher mortality than nondispersing lynxes of the same age, due mostly to anthropogenic causes. About half of the dispersers successfully settled in a territory at distances that differed between areas of origin, but not between sexes. Distances reached, shorter than those reported for other similar-size solitary felids, are limited by anthropogenic barriers that prevent connection with closer metapopulations. |