Abundance of wild prey modulates consumption of supplementary food in the Iberian lynx

Food supplementation is increasingly used as a conservation tool. However, little is known about how much supplemental food is used by target populations or the degree to which the abundance of natural food affects the utilization of supplemental food. Long-term supplementation programmes could cause individuals to rely almost exclusively upon supplemental food and, consequently, lose some skills needed to forage efficiently on natural food. This may result in reduced fitness upon discontinuation of supplemental food. The Iberian lynx (Lynxpardinus) preys almost exclusively upon European wild rabbits (Oryctolagus cuniculus), and some populations are thought to be food limited. We quantified the contribution of supplemented domestic rabbits, whose guard hairs could be distinguished from hairs of wild rabbits, to the diet of the Iberian lynx. We also examined whether the consumption of domestic rabbits varied with the availability of wild rabbits, and with the duration of exposure to supplemental food. Domestic rabbits made up over 50% of the diet. Consumption of domestic rabbits decreased non-linearly as the relative abundance of wild rabbits increased; however, this pattern was true only above a threshold density of one wild rabbit km⁻¹. Below this threshold, supplementation was apparently strictly necessary to retain Iberian lynx. The consumption of domestic rabbits did not increase with the length of the supplementation period. Lynx continued consuming wild rabbits proportionally to their abundance, suggesting lynx did not become dependent upon supplemental food. Understanding how the abundance of natural food modulates consumption of supplemental food may help to adjust supplementation schedules to food availability and to the needs of the target populations.     

Patterns and causes of non-natural mortality in the Iberian lynx during a 40-year period of range contraction

We analyse the spatial and temporal variation in non-natural mortality during a 40-year period of strong contraction of the geographic range of the Iberian lynx (Lynx pardinus), which shrank from 40,600 to 22,300 km². We recorded 1258 lynx deaths, an average of 31.5 losses per year over the study period. Given the reduced lynx population size, especially later in the period (around 1100 individuals), this level of non-natural mortality may have contributed significantly to the quick decline of the Iberian lynx. Non-natural mortality was not spatially correlated with, and probably did not shape the pattern of, relative abundance of lynx across its core range, but may have reduced its absolute density. Lynx losses were caused mainly by traps set not only for predator control but also for rabbits (Oryctolagus cuniculus), the lynx's staple food. We did not find evidence that non-natural mortality was higher in small lynx populations through edge effects. The highest mortality levels were recorded in regions where small game was a valuable economic resource compared with other activities. Mortality decreased throughout the period because of changes in the prevailing game regimes rather than because of legal protection. The Iberian lynx is now critically endangered and effective protection should be urgently enforced, especially in small game estates, which are environmentally favourable for rabbits but risky for lynx due to predator control. Lynx reintroductions would be better attempted in traditional rabbit hunting areas. Some big game estates where small game is not exploited and predators are not controlled may be good candidates for lynx reintroduction too, provided that habitat is managed towards a suitable interspersion of woody cover and grassland.     

Wild rabbit restocking for predator conservation in Spain

The decline of rabbit (Oryctolagus cuniculus) populations in Mediterranean Spain has been shown to be one of the main threats to rabbit-specialist predators such as the Iberian lynx (Lynx pardina) and the Spanish imperial eagle (Aquila adalberti), two species which are in serious danger of extinction. Consequently, corrective measures such as increasing rabbit populations by restocking have been carried out to help the recovery of predator populations. In order to determine the general applicability of rabbit restocking for predator conservation, we performed three experimental restockings and evaluated their success in relation to season, habitat quality and the number of animals introduced. Rabbits were released either in large or small numbers in all four seasons of the year, and in habitat types defined as `poor' or `rich' according to the food availability for rabbits. For each restocking we evaluated rabbit survival, degree of residency and expected population increase. As a rule, the highest restocking success occurred whenever smaller number of rabbits were released in the richest quality habitat. Restocking during the breeding season was less successful than in other seasons. Problems concerning intraspecific competition, reproductive failure and diseases are discussed.     

The use of immunization programs in wild populations: Modelling effectiveness of vaccination campaigns against rabbit hemorrhagic disease

Vaccination programs are occasionally used on wild mammal populations with conservation goals. In the case of the European wild rabbit Oryctolagus cuniculus, vaccination campaigns against rabbit hemorrhagic disease (RHD) have been widely applied to enhance rabbit populations, but their overall effects have not been compared. I used a modelling approach to compare the effects of several vaccination strategies on the growth rate of wild rabbit populations. For all simulated vaccination strategies, vaccination campaigns yielded positive or negative population growth rates, depending on rabbit population dynamics and subsequent RHD dynamics. Growth rate was negative when the proportion of RHD-seropositive adult rabbits was low or medium before vaccination, which occurred in populations at low rabbit density. Given that these low density populations are mainly targeted by vaccination campaigns, the model suggested that current immunization programs may be causing harmful effects on many rabbit populations. The best annual period to carry out vaccination campaigns was determined by the age-class targeted for immunization. If the RHD dynamics were not known, vaccination of only juvenile rabbits seemed to be the most conservative option, since it minimized the probability of yielding negative growth rates, whereas vaccination of only adult rabbits was the worst option. These findings suggest that prior knowledge of RHD dynamics in populations subject to immunization is essential to minimize the risk of harmful effects.     

Conservation of European wild rabbit populations when hunting is age and sex selective

Several predator species at risk of extinction in Southwestern Europe are dependent on the population density of European wild rabbits Oryctolagus cuniculus. Rabbit populations in the region, however, have recently undergone dramatic decreases in population density, which may be exacerbated by hunting. Current hunting policies set the autumn-winter season, just before the start of rabbit reproduction, as the main hunting season, and previous theoretical models have estimated that the current hunting season may have the greatest negative impact on rabbit abundance and should be changed. We utilised a model for rabbit population dynamics to determine the effects of the timing of hunting during two seasons, summer and autumn, on the tendency of rabbit populations to be over-harvested and on the number of rabbits hunted. This model included field estimates of age- and sex-selection biases of hunting by shotgun. Scenarios with different hunting rates and sex- and age-selection probabilities of hunting were simulated for populations with different turnover levels and with and without compensatory mortality mechanisms. Field estimations showed that hunting in summer was juvenile-biased whereas autumn hunting was juvenile- and male-biased. In contrast to previous findings, our modelling results suggested that hunting in autumn may be the most conservative option for harvesting of rabbit populations, since these populations were more prone to be over-harvested during the summer. The differences between the two seasons in number of rabbits hunted were dependent on population dynamics and hunting sex- and age-selection probabilities. Our findings suggest that altering of current hunting policies would not optimise the exploitation or conservation of wild rabbit populations, but that the latter may be improved by some changes in the timing of hunting.     

Reproduction and pre-dispersal survival of Iberian lynx in a subpopulation of the Doñana National Park

Little is known about the reproduction of the Iberian lynx (Lynx pardinus) even though it is the most endangered felid in the world. We studied during 9 years several reproductive parameters of the Iberian lynx in one of the subpopulations situated in Doñana National Park (south-western Spain), by means of radio-tracking, direct observations and photo-trapping. The potential breeding subpopulation was usually composed of 3 adult females, which bred 83% of the total possible 29 female-reproductive year. The minimum total number of cubs born during the study was 64 (7.7 ± 0.69 per year). There was no correlation between the number of cubs born or number of breeding females and population size of European rabbit (Oryctolagus cuniculus, the main prey of the lynx). All known births (n = 16) occurred in March except one in April and another in June. Mean litter size was 3.0 ± 0.16 (n = 16, range = 2-4). Sex-ratio (n = 59 cubs) was 1.03:1.00 (females:males). Nevertheless, the commonest picture was a female with 2 cubs older than 3 months. Altogether, at age of 3 months, 75% of cubs survived. Number of lynx alive at 10 months old and before dispersing was 69% and 57%, respectively. Sex did not affect survival for any age. Normally, it was not possible to know the causes of the death of cubs younger than 3 months. Survival at this age was not related with mother, mother age, or rabbit abundance. All females that bred were older than 3 years. The age of last reproduction was 9 years. For 3 females that were tracked during almost their complete reproductive life, the life time reproductive output was between 11 and 19 cubs. Iberian lynx reproductive parameters did not respond to wide changes in prey abundance during the study. Conservation plans considering the extraction of cubs with a low survival probability should be considered by managers, for instance, in translocation campaigns.     

Effects of supplementary feeding on the offspring sex ratio of kakapo: a dilemma for the conservation of a polygynous parrot

The kakapo (Strigops habroptilus) is a large, flightless, nocturnal parrot, endemic to New Zealand. It is critically endangered, with a world population of ca. 62 individuals and a male-biased adult sex ratio. The species has a polygynous “lek” mating system and adult males typically weigh 30-40% more than females. The kakapo is subject to intensive conservation efforts, including the provision of supplementary food to wild birds to encourage successful nesting. There is mounting evidence that, in polygynous species with large variance of male reproductive success, females in better condition may maximise their fitness by producing more offspring of the larger, more costly sex to be reared. We used data on the sex ratio of progeny of female kakapo that had or had not received supplementary food, to test the hypothesis that supplementary feeding might cause a male-biased offspring sex ratio. There was a significant excess of males in the clutches of females provided with supplementary food, suggesting that changes need to be made to the feeding regime to increase recruitment of females. This is an example of applying evolutionary theory to a practical conservation problem.     

Population fragmentation and extinction in the Iberian lynx

We studied the relationship between extinction frequencies of Iberian lynx subpopulations (Lynx pardinus) and their size and isolation during a 35-year period of strong geographic range contraction. At the end of this period there were fewer fragmentation events, fewer lynx populations of small size, and less isolation between them, than in simulated geographic ranges derived from a random distribution of local extinctions. Only small populations occupying <500 km² went extinct. Local extinction in large, self-sustainable populations probably resulted from the sole action of deterministic factors, e.g. widespread prey decline. As compared with large populations, small ones experienced increased contraction per unit occupied area, which may reflect demographic unstability. The consistent effect of isolation on extinction suggests that such unstability was often prompted by reduced immigration and the subsequent disruption of metapopulation equilibrium. Several practical recommendations could be derived. Provided that habitat quality was adequate, a lynx population should avoid extinction within 35 years if it occupied an area of at least 500 km². The persistence of small populations will also be enhanced by minimizing the distances to neighbouring populations within 30 km, and by maximizing the area occupied by these neighbours. Therefore, habitat management, or any other restoration action, directed to expand the area occupied by a small lynx population should be best located at points of its boundaries oriented towards other existing nearby populations.     

Unravelling the paradox of rabbit haemorrhagic disease virus emergence, using phylogenetic analysis; possible implications for rabbit conservation strategies

During the past 50 years two readily distinguishable rabbit-specific diseases caused by Myxoma virus (MYXV) and Rabbit haemorrhagic disease virus (RHDV) respectively, have decimated wild rabbit populations worldwide. Combined with the use of these viruses as biocontrol agents, the consequences for farming, commercial rabbit breeding and rare habitat conservation dependent on rabbit grazing, have been both positive and negative. Moreover, rare predators that rely on rabbits as a food resource, and even hunters, have suffered the consequences of rabbit populations being affected by one or other of these viruses.Rabbit haemorrhagic disease virus was first identified after thousands of domestic rabbits died suddenly in China in 1984. Similar epidemics subsequently occurred in other regions of Asia, the Middle East, Europe and North America, suggesting that the virus had dispersed widely following its emergence in China. However, the discovery that RHDV had circulated apparently harmlessly for many years before the first recognised epidemic in China prompted us to investigate the evolution, emergence and dispersal of this virus in relation to its impact on conservation of wildlife species. Accordingly, we have sequenced new isolates of RHDV and combined these data with a global selection of available RHDV sequences. Using phylogenetic analysis we demonstrate that the Chinese epidemic virus diverged from European viruses that circulated many years prior to 1984. We also demonstrate that the lineages of the pathogenic viruses that emerged in the UK in the early 1990s, are distinct from and pre-date those of the 1984 Chinese virus. In other words, European strains of RHDV emerged from apparently harmless strains to cause epidemic outbreaks, independently of the Chinese 1984 epidemic virus. These studies demonstrate how understanding viral epidemiology can improve the development of strategies to conserve rabbits, rare predator species and the habitat.     

Modeling the reintroduction of lynx to the southern portion of its range

We modeled populations of lynx (Lynx canadensis) and snowshoe hares (Lepus americanus) to determine prey densities required for persistence of lynx translocated to the southern portion of the species' range. The models suggested that a density of 1.1-1.8 hares/h is required for lynx persistence; these densities are higher than those reported for most hare populations across the USA. We found that lynx dispersal and density-independent mortality substantially increased the hare density required for lynx persistence. Reintroduction success was associated with number of release events, total number of animals released, and timing of release relative to the phase of the hare population cycle. However, no release protocol could override the negative effects of low prey density or high population losses. We conclude that successful lynx reintroduction requires high hare densities and minimal anthropogenic disturbance; few areas in the contiguous USA currently posses such qualities.     

Managing supplementary feeding for avian scavengers: Guidelines for optimal design using ecological criteria

Current European sanitary laws are promoting the concentration of domestic livestock carcasses in limited locations called ‘vulture restaurants’ or supplementary feeding stations in order to safeguard human health. However, this type of food concentration could lead to monopolization by a few, large dominant species. Management guidelines are urgently needed to ensure that potentially less competitive and more endangered scavengers can also benefit from this resource, considering that once abundant carcasses are now absent from the field. Here, we assess factors affecting the abundance of six avian scavenger species at 17 feeding stations in northern Spain, considering aspects such as carrion availability, physiographic features, humanization, presence of heterospecifics and densities of scavengers during both winter and summer seasons. Results indicate that conditions for interspecific facilitatory processes are possible at low numbers (<100 individuals) of griffon vultures (Gyps fulvus). Otherwise, the other avian scavengers are excluded. In a few cases, spatio-temporal patterns of segregation become apparent. Differences in the size of carcasses supplied to feeding stations as well as the local characteristics influence the balance of species at these points and, therefore, how species of conservation concern use feeding stations. Future legislation should encourage the opening of numerous feeding stations supplied with low quantities of food to mimic the original condition of temporal and spatial unpredictability of carcasses and to maintain ecological relationships within the scavenger guild.     

Modelling hunting strategies for the conservation of wild rabbit populations

Recently, European wild rabbit (Oryctolagus cuniculus) populations have undergone a sharp decline that may be exacerbated by hunting. We investigate the effects of the timing of hunting on the conservation of wild rabbit using a model for rabbit population dynamics. Scenarios with different hunting rates and age strategies were simulated for different population qualities. We interviewed hunters to ascertain the degree to which they would accept a change in the timing of hunting. We also investigated the hunting pressure applied by hunters and its relationship with rabbit abundance. Modelling results indicate that the current hunting season has the greatest impact on rabbit abundance. Hunting in late spring optimises hunting extraction while conserving rabbit populations. When the rabbit population quality is low the effects of age strategies and the timing of hunting are less important than the effect of the hunting rate applied. Almost half the hunters would agree to policy changes. More than 75% of hunters implemented self-imposed hunting restrictions to improve rabbit populations, that were more frequently applied in high rabbit abundance areas. Therefore, changing the timing of hunting and increasing the participation of hunters in low abundance areas could optimise both the exploitation and the conservation of wild rabbit populations in southwestern Europe.     

The role of commercial crocodile farming in crocodile conservation

Commercial crocodile rearing stations in Rhodesia are described, including regulations which govern their operation. When crocodile eggs are collected from the wild a quota of juveniles equivalent to 5% of the number collected must be released at the age of 3 years. Figures for hatching success and juvenile growth on rearing stations compared with wild populations indicate that both these parameters are better on the rearing stations. The growth rate on a rearing station is twice as fast as in the wild. Data on juvenile survival on the rearing stations suggest that it is of the order of 50% to the age of 3 years. No comparative information is available for wild populations. Survival of station-reared crocodiles after release into the wild is good, although growth slows substantially. Juveniles for release are a valuable tool in management, for restocking suitable areas or supplementation of natural recruitment. Crocodile farms may provide an answer to future management of this species, and a ready source of breeding stock is available in ‘problem’ animals which are relocated rather than shot. Crocodile rearing and farming in developing countries could provide the incentive to maintain a renewable resource rather than to exploit and destroy existing populations.     

Validation of a FAO land evaluation method by comparison of observed and predicted yields of five food crops in Burundi

Abstract. A land evaluation using unsophisticated data successfully predicted yield ranges of various crops in Burundi. Yields of wheat, pea, bean, maize and potato predicted from data for climate, soil and land use technology were compared with observed yields from farm trials and from seed station and research station trials. The predicted range of yield for each crop suitability class enclosed the mean farm yields 13 times out of 16 and yields on seed stations and research stations 10 times out of 15 and 14 times out of 21 respectively. The variability of the observed yields exceeded the predicted range of yields. The method is considered as validated. The method appears to be applicable for multi-year studies at a broad scale, but yield variation according to the weather from year to year is not accounted for. The variances of the yields on farms are greater than the variances in seed station and research station trials.
Since the method predicts correctly the mean regional farm yields, it could be useful for land use planning, research into optimal regional cropping specialisation, studies on food policy, and for evaluation of economic return and sustainability of different crops.     

Environmental correlates of Eurasian lynx occurrence in Poland - Large scale census and GIS mapping

Based on data from the National Lynx Census, carried out in Poland in 2000-2001, and using Geographic Information System, we analysed nine habitat characteristics in 56 circular sample plots (113 km² each), where lynx (Lynx lynx) have been recorded, and 118 plots with no signs of their presence. In plots with lynx the forest cover (on average 68%) was two times higher and the forest fragmentation lower than in plots with no lynx records. The plots with and without lynx differed significantly also in the number of villages and towns, length of main motorways and railways. Lynx occurrence was negatively associated to human settlements and transportation infrastructure. Logistic regression analysis showed that sufficient forest cover (>40%) and the short straight-line distance to the eastern or southern border of Poland (as a proxy of the distance to a more contiguous range of lynx in Europe) are the two most important variables explaining lynx distribution. We conclude that, in Poland, increase of forest fragmentation and transportation infrastructure may become important threats to lynx populations.     

Genetic resources of wild tuberous food plants traditionally used in Similipal Biosphere Reserve, Odisha, India

The subterranean parts of many wild plants form an important constituent of traditional diet of the tribal inhabitants of Similipal Biosphere Reserve, Odisha especially in times of food scarcity during critical periods. However, no specific study has been made so far on this aspect. The present study was conducted during 2008–2012 as a search for sources of food and to assess the dietary diversity, consumption pattern, culinary uses and prioritized species of wild tuberous plants sustained by local tribes. The exploration and germplasm collection missions along with intensive botanical survey, focus group discussions, structured household interview and market survey were conducted in 30 villages interacting with 102 key informants of core and buffer zones. A total of 55 wild edible tuberous species representing 37 genera and 24 families were inventoried including 17 species used during food deficiency to meet seasonal shortages. The analyzed data contributed 5 use categories, 4 preparation methods, 7 kinds of food items, 10 species as children snacks, 35 species of pharma-foods and 20 prioritized species. Ten species were domesticated by tribes thus reducing threats on wild tubers and 20 species were traded in local markets to generate additional income exemplifying economic benefits from wild tubers. Seventeen species were identified as novel uses of food items from India. The findings suggested that the nutritional profile along with pharmaceutical attributes of preferred wild food plants be analyzed for recommending suitable species for better nutrition and development of nutraceuticals. Further, many genetic resources of these wild tuberous species of agri-horticultural importance constitute the wild genepool hence their economic and breeding potential along with desirable attributes need to be investigated for utilization in crop improvement programmes.     

The trauma of no-choice: Wild food ethnobotany in Yaghnobi and Tajik villages,Varzob Valley,Tajikistan

Due to global change and the migration crisis both needing rapid attention, there has been growing debate about the drivers of change in the diet of migrants. Our study aimed to evaluate the consequences of forced resettlement on local ecological knowledge related to wild food plants among forcefully resettled Yaghnobi people in Tajikistan. We conducted 49 semi-structured in-depth interviews and recorded 27 wild food taxa and five unidentified folk taxa used by Yaghnobis and Tajiks in the villages surrounding Yaghnob Valley (including families ressetteled from Yaghnob Valley) in central Tajikitsan. The comparision between the two considered groups showed a high level of Tajikisation among Yaghnobis, both those who live alongside Tajiks as well as those living separately. The few families that still have distinct Yaghnobi plant uses are the ones which were given the opportunity to choose the spot in which to relocate and still visit the Yaghnob Valley regularly. On the basis of our study, we suggest that affording a choice of where to relocate is better than no choice, as the loss of motivation also affects the use of wild food plants. Given the pressure of the possible relocation of many groups of people in the light of global change, we suggest focusing efforts on studying similar cases in order to minimize the damage caused to people by relocation. The trauma of forced relocation, even just a few kilometers away, directly or indirectly affects wild food plant use and with this the food security of the community.

     

Successful analysis of gut contents in fungal-feeding oribatid mites by combining body-surface washing and PCR

The feeding habits of soil mesofauna have been a mystery for decades, and depending on the methods used, different degrees of feeding specialisation have been observed. A new way to study the almost unknown feeding habits of soil mesofauna e.g. oribatid mites is to use PCR-based techniques. When applying PCR on these small organisms, the low amount of ingested DNA can cause problems. Even more important is to certify that the amplified DNA does not originate from body-surface contamination. The aim of this study was to analyse if washing of the body surface combined with PCR can be a successful approach when identifying the food ingested by fungivorous mites. The method was developed in a laboratory system where we used the oribatid mite Archegozetes longisetosus as a model organism due to its relatively short life cycle and ease of laboratory culturing. The results demonstrated that surface contamination is a serious problem. Both washing and dissection was needed to remove surface contamination on such small organisms. To get a reliable result the samples also had to contain at least five pooled guts, but preferably ten. This is the first step towards a successful use of PCR-based methods to study natural feeding habits of species most likely contaminated on the body surface. When modified for field conditions, the results obtained by this method have a high potential to answer many questions about the animals feeding habits, and their functional role in the soil.     

Sustainable harvest strategies for age-structured Eurasian lynx populations: The use of reproductive value

Eurasian lynx in Scandinavia are subject to regular harvest and lethal control to reduce depredation on domestic livestock and semi-domestic reindeer. Here we introduce the use of total reproductive value to model the effects of current harvest on population dynamics and to propose sustainable harvest strategies for lynx. Demographic stochasticity strongly influences lynx population dynamics. Analyses of the number of lynx shot in relation to the number of family groups registered in annual censuses showed proportional harvest in large parts of Norway because the quotas were higher at larger population sizes. In other areas of Norway the number of lynx shot was independent of population size. The analyses of the model showed that a pure proportional harvest strategy may lead to rapid extinction of lynx populations. In contrast, applying a threshold or proportional threshold harvest strategy in which no harvest occurs below a given threshold can result in the maintenance of viable populations. Thus, this study shows that harvest without any lower threshold for stopping harvest will result in rapid extinction of lynx populations. Accordingly, lynx harvest is not likely to be sustainable if the illegal killing of animals is not controlled because poaching can result in a de facto proportional harvest even at very small population sizes. Under the influence of the large demographic stochasticity in lynx populations this harvest would result in short expected times to extinction. This gives an empirical demonstration that a correct choice of harvest strategy is essential for maintenance of viable populations of harvested species. Our analyses illustrate that parameters determining the viability of small populations can be estimated from individual-based demographic data from a sample of individuals without using time series of fluctuations in population size, which facilitates quantitative analyses of how harvest or removal of individuals, e.g. for captive breeding or translocations, affect the expected lifetime of populations.     

Wild-captive metapopulation viability analysis

We developed an interactive management model for wild and captive populations of the ploughshare tortoise or angonoka, Geochelone yniphora. Interactive management is based on the translocation of individuals between wild and captive populations to simulate a metapopulation. Demographic parameters of one captive and two wild populations of this rare tortoise were used to conduct a metapopulation viability analysis (MVA). The effectiveness of the conservation strategy proposed for this species was then evaluated by modifying the probability of extinction and growth of the metapopulation over a fixed period of time. Several alternative scenarios of interactive management were then tested and ranked in terms of their effect on the viability of the metapopulation. The model predicted that catastrophic events such as bush fires would likely have a negative effect on the future of remaining wild populations. However, the model also predicted that the use of captive-born offspring to establish additional wild populations would decrease the risk of extinction of the metapopulation as a whole. We believe that, when supported by sound knowledge of the demographic parameters of a species, the use of MVA as part of an interactive management program can be an effective conservation tool that allows assessment of the probable response of both captive and wild populations to different management alternatives. One of the most interesting aspects of this interactive management approach is the link between in situ and ex situ conservation.