| 26. |
- Elmhagen, Bodil, 1973-, et al.
(författare)
-
Trophic control of mesopredators in terrestrial ecosystems: top-down or bottom-up?
- 2007
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 10:3, s. 197-206
-
Tidskriftsartikel (refereegranskat)abstract
- It has been argued that widespread extinctions of top predators have changed terrestrial ecosystem structures through mesopredator release, where increased abundances of medium-sized predators have detrimental effects on prey communities. This top-down concept has received much attention within conservation biology, but few studies have demonstrated the phenomenon. The concept has been criticized since alternative explanations involving bottom-up impacts from bioclimatic effects on ecosystem productivity and from anthropogenic habitat change are rarely considered. We analyse the response of a mesopredator (the red fox) to declines in top predators (wolf and Eurasian lynx) and agricultural expansion over 90 years in Sweden, taking bioclimatic effects into account. We show a top-down mesopredator release effect, but ecosystem productivity determined its strength. The impacts of agricultural activity were mediated by their effects on top predator populations. Thus, both top-down and bottom-up processes need to be understood for effective preservation of biodiversity in anthropogenically transformed ecosystems.
|
|
| 27. |
|
|
| 28. |
|
|
| 29. |
- Elmhagen, Bodil, 1971-, et al.
(författare)
-
Världens lodjursarter
- 2014
-
Ingår i: Lodjuret. - Stockholm : Atlantis. - 9789173536547 ; , s. 9-29
-
Bokkapitel (populärvet., debatt m.m.)
|
|
| 30. |
|
|
| 31. |
- Elmhagen, Bodil, et al.
(författare)
-
Åtgärdsprogram för fjällräv, 2017–2021 : (Vulpes lagopus)
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fjällräven är klassificerad som starkt hotad i Sverige och akut hotad i Norge. På 1800-talet var det en vanligt förekommande art, men till följd av intensivt jakttryck reducerades populationen kraftigt i slutet av 1800-talet. Fjällräven fridlystes 1928 i Sverige och 1930 i Norge. Trots skydd har populationen inte återhämtat sig. Detta beror på ett flertal samverkande faktorer, framförallt låg populationsstorlek, ökad konkurrens från rödrävar som expanderar in i fjällvärlden, samt uteblivna eller mer oregelbundna lämmeltoppar som leder till födobrist. Dessutom har inavel och inavelsdepression med ökad dödlighet och minskad reproduktion dokumenterats i vissa delbestånd. Sjukdomar och parasiter utgör ett ytterligare hot mot de små delpopulationernas fortlevnad. Störningar från mänskliga aktiviteter kan utgöra ytterligare bidragande faktorer.År 2015 fanns omkring 240 reproducerande vuxna fjällrävar i Sverige och Norge, vilket utgör ett mått på beståndets minimala storlek. Inom EU är fjällräven en prioriterad art enligt habitatdirektivet, i Sverige är fjällräven fridlyst enligt artskyddsförordningen, och i Norge är fjällräven skyddad med ”fjällrävförskriften” enligt naturmangfoldloven.Åtgärder för att rädda fjällräven genomfördes i Sverige och Finland under 1998–2002 genom EU-Life Nature projektet SEFALO. Projektet fortsatte i en andra fas, SEFALO+ (2003–2008) som även involverade Norge. Båda projekten inkluderade åtgärder som stödutfodring, rödrävsjakt och inventeringar. I Norge startade flera åtgärder 2004 på uppdrag av Miljødirektoratet (tidigare Direktoratet for naturforvaltning). Sedan dess har en kombination av åtgärder genomförts i olika delbestånd: avel och utsättning av valpar, stödutfodring, samt kontroll av rödrävsbestånden. Avelsprojekt för fjällräv startade 2005 och de första valparna sattes ut 2006. Inom EU-Interregprojektet Felles Fjellrev (2010–2013) genomfördes utvidgade åtgärder i Jämtlands län samt Nord- och Sør-Trøndelag, med riktade åtgärder i mindre fjällområden mellan de fyra större delbestånden av fjällräv.För att fjällrävsstammen ska återuppnå en gynnsam bevarandestatus bör bevarandeåtgärderna fortsätta inom ramen för det svensk-norska åtgärdsprogrammet. Den långsiktiga visionen är att skapa en stabil och livskraftig stam med gynnsam bevarandestatus utan behov av ytterligare åtgärder. Det är emellertid långt tills denna vision uppnås och i detta program definieras konkreta målsättningar på lång (2035) och kort (2021) sikt. I detta program föreslås fortsatt genomförande av centrala åtgärder i form av stödutfodring och rödrävskontroll. Dessutom ska orsakerna till rödrävens ökade förekomst på fjället hanteras genom åtgärder mot de faktorer som gynnar expansionen. Avel och utsättning från det norska avelsprojektet, alternativt translokering av rävar mellan delpopulationerna, föreslås som åtgärd för att förstärka små populationer, etablera fjällrävar i mellanområden samt minska graden av inavel. Populationernas hälsostatus bör övervakas och vid ett utbrott ska behandling sättas in. Riktade informationskampanjer ska utformas för att minska konflikt och störning med människan.De åtgärder som förutsätts finansieras av Naturvårdsverket och Miljødirektoratet för genomförande av åtgärdsprogram för hotade arter beräknas totalt uppgå till 15, 1 miljoner kronor respektive 47,6 miljoner kronor under programmets giltighetsperiod 2017–2021.
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
- Haage, Marianne, et al.
(författare)
-
An experimental approach to the formation of diet preferences and individual specialisation in European mink
- 2017
-
Ingår i: European Journal of Wildlife Research. - : Springer Science and Business Media LLC. - 1612-4642 .- 1439-0574. ; 63:2, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- Individual dietary specialisation can occur within populations even when average diets suggest that the population has a generalist feeding strategy. Individual specialisation may impact fitness and has been related to demographic traits, ecological opportunity, competition, learning and animal personality. However, the causation and formation of individual specialisation are not fully understood. Experiments on animals raised in controlled environments provide an opportunity to examine dietary preferences and learning largely independent from variation in lifetime experiences and ecological opportunity. Here, we use a feeding experiment to examine individual specialisation and learning in captive bred European mink (Mustela lutreola) in an Estonian conservation programme. In a series of cafeteria experiments, animals could choose between one familiar food item (Baltic herring Clupea harengus membras) and two initially novel ones (noble crayfish Astacus astacus and house mouse Mus musculus). In general, mice were rarely eaten whilst crayfish consumption increased over time and fish decreased. At the individual level, there was a mix of generalists and crayfish or fish specialists, and the individuals differed in learning time in relation to novel prey. Our results indicate that individual variation in innate preferences and learning both contributes to individual diet specialisation. The differences in learning indicate individual variation in behavioural plasticity, which in turn can be related to personality. This could be of concern in conservation, as personality has been shown to affect survival in translocations.
|
|
| 35. |
- Haage, Marianne, 1985-
(författare)
-
Conservation, personality and ecology of the European mink (Mustela lutreola)
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Loss of biodiversity is a growing problem and hence conservation of species is becoming increasingly important. In this dissertation conservation issues related to the critically endangered European mink (Mustela lutreola) are examined in situ (in the wild) and ex situ (in captivity) on both an individual and community level. It also contains fundamental research as conservation contexts often allow for conclusions beyond applied biology. Individual behavioural differences, e.g. personality, can impact fitness and are hence relevant for conservation. Paper I thus experimentally explores the structure, expression and plasticity of personality in captive European minks. Thereafter paper II investigates if personality affects survival of reintroduced captive-bred animals and if spatiotemporal conditions affects the relationship between personality and survival. Paper III experimentally explores individual dietary specialism and learning in relation to novel prey as this could also impact survival. One of the main threats to the European mink is displacement by the invasive American mink (Neovison vison) wherefore management of American mink is important for European mink conservation. Paper IV hence analyses survey data to study whether native otters and red foxes can suppress American mink populations in north-eastern Europe. In the results three personality trait domains were identified in the European mink: boldness, exploration and sociability. The domains were repeatable but plastic between the non-breeding and breeding season. Reintroduced personality-tested animals survived longer if they were bolder but the effect of exploration was either positive or negative depending on spatiotemporal conditions. This is not only interesting for conservation but provides new insights on how individual behavioural differences could be maintained over evolutionary time. Whilst exploration is likely to be maintained by fluctuating selection pressures, the mechanism seem to vary with domain. The feeding experiments revealed diet choices similar to those found in wild individuals as there were both generalists and different types of specialists. Still, individuals differed in learning time towards novel but natural prey, suggesting that reintroduced animals might differ in their ability to find food after release. This could affect survival also and be related to personality. Survey data revealed that American mink abundances were suppressed by those of red foxes. Previous studies show that foxes are suppressed by lynx, and the abundance pattern of mink in relation to red fox found here indicate the existence of a predator cascade as mink were most abundant where lynx were abundant and vice versa. In several regions in the study area population dynamics indicated either exploitation or interference competition as probable mechanisms whereby foxes suppress minks. However, in many regions there were no relationships between dynamics. This could be due to that exploitation and interference competition might occur simultaneously and thus cancel each other out in the dynamics. Overall this thesis shows the importance of considering individual traits in conservation efforts, and also provides knowledge on the structure, plasticity and evolution of personality. As American mink was suppressed by foxes, management efforts might be most beneficial for species impacted by the mink if they to a larger extent are undertaken in areas with low fox abundances.
|
|
| 36. |
|
|
| 37. |
- Haage, Marianne, et al.
(författare)
-
The influence of spatiotemporal conditions and personality on survival in reintroductions-evolutionary implications
- 2017
-
Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 183:1, s. 45-56
-
Tidskriftsartikel (refereegranskat)abstract
- Personality exists in non-human animals and can impact fitness. There is, however, a shortage of empirical studies in certain areas within the field, and fundamental evolutionary theory on personality remains largely untested. For example, little is known on how variation in personality is maintained over evolutionary time. Theory suggests that fluctuating selection pressures due to spatiotemporal variation in conditions, e.g. food availability, is a possible mechanism and a few studies have shown that the success of different personality types varies with spatiotemporal conditions. However, it remains unknown whether different mechanisms can maintain personality within a species. Here we use a reintroduction programme for the critically endangered European mink (Mustela lutreola) to test whether multiple personality trait domains (boldness, exploration and sociability) affected survival in two different years and islands. This was done through pre-release personality tests and post-release radio-tracking monitoring. Survival was positively correlated with boldness, whereas the relationship with exploration was either negative or positive depending on year/island. The results show a complex relationship between personality and survival and suggest that exploration can be maintained over evolutionary time via spatiotemporal variation in conditions. However, in contrast to exploration, boldness did not vary spatiotemporally and sociability had no impact on survival. This indicates that different personality trait domains might be maintained by different mechanisms. To date, personality has been studied primarily within behavioural sciences, but through empirical findings we highlight the importance of personality also in ecology and conservation biology.
|
|
| 38. |
- Herfindal, Ivar, et al.
(författare)
-
Population persistence in a landscape context : the case of endangered arctic fox populations in Fennoscandia
- 2010
-
Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33:5, s. 932-941
-
Tidskriftsartikel (refereegranskat)abstract
- Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub-populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within-fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine-scale Allee or Allee-like effects, as well as environmental influences related to increased competition and exclusion by red foxes
|
|
| 39. |
- Khalil, Hussein, et al.
(författare)
-
The relationship between wolverine and larger predators, lynx and wolf, in a historical ecosystem context
- 2014
-
Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 175:2, s. 625-637
-
Tidskriftsartikel (refereegranskat)abstract
- Apex predators play an important role in shaping ecosystem structure. They may suppress smaller predators (mesopredators) but also subsidize scavengers via carrion provisioning. However, the importance of these interactions can change with ecosystem context. The wolverine (Gulo gulo) is a cold-adapted carnivore and facultative scavenger. It has a circumboreal distribution, where it could be either suppressed or subsidized by larger predators. In Scandinavia, the wolverine might interact with two larger predators, wolf (Canis lupus) and lynx (Lynx lynx), but human persecution decimated the populations in the nineteenth and early twentieth century. We investigated potential relationships between wolverine and the larger predators using hunting bag statistics from 15 Norwegian and Swedish counties in 1846-1922. Our best models showed a positive association between wolverine and lynx trends, taking ecological and human factors into account. There was also a positive association between year-to-year fluctuations in wolverine and wolf in the latter part of the study period. We suggest these associations could result from positive lynx-wolverine interactions through carrion provisioning, while wolves might both suppress wolverine and provide carrion with the net effect becoming positive when wolf density drops below a threshold. Wolverines could thus benefit from lynx presence and low-to-intermediate wolf densities.
|
|
| 40. |
- Kuijper, D. P. J., et al.
(författare)
-
Paws without claws? Ecological effects of large carnivores in anthropogenic landscapes
- 2016
-
Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 283:1841
-
Tidskriftsartikel (refereegranskat)abstract
- Large carnivores are frequently presented as saviours of biodiversity and ecosystem functioning through their creation of trophic cascades, an idea largely based on studies coming primarily out of relatively natural landscapes. However, in large parts of the world, particularly in Europe, large carnivores live in and are returning to strongly human-modified ecosystems. At present, we lack a coherent framework to predict the effects of large carnivores in these anthropogenic landscapes. We review how human actions influence the ecological roles of large carnivores by affecting their density or behaviour or those of mesopredators or prey species. We argue that the potential for density-mediated trophic cascades in anthropogenic landscapes is limited to unproductive areas where even low carnivore numbers may impact prey densities or to the limited parts of the landscape where carnivores are allowed to reach ecologically functional densities. The potential for behaviourally mediated trophic cascades may be larger and more widespread, because even low carnivore densities affect prey behaviour. We conclude that predator-prey interactions in anthropogenic landscapes will be highly context-dependent and human actions will often attenuate the ecological effects of large carnivores. We highlight the knowledge gaps and outline a new research avenue to study the role of carnivores in anthropogenic landscapes.
|
|
| 41. |
- Larm, Malin, et al.
(författare)
-
The role of wildlife tourism in conservation of endangered species : Implications of safari tourism for conservation of the Arctic fox in Sweden
- 2018
-
Ingår i: Human Dimensions of Wildlife. - : Informa UK Limited. - 1087-1209 .- 1533-158X. ; 23:3, s. 257-272
-
Tidskriftsartikel (refereegranskat)abstract
- There are both positive and negative impacts on wildlife associated with wildlife tourism. In Sweden, the endangered Arctic fox is subject to a growing tourist interest. In the Helags mountain region there are guided Arctic fox safari tours that provide visitors with information about the Arctic fox. A survey of five separate groups of visitors in the region revealed that knowledge about the status of Arctic foxes and awareness of the behavioral guidelines for Arctic fox encounters improved after participation in a safari tour and with increasing Arctic fox interaction. We propose a schematic model summarizing the diverse ways in which wildlife tourism affects wildlife and their relative importance for conservation. The Arctic fox population in Sweden is small and sensitive to disturbance, but the positive impacts of Arctic fox tourism seem to compensate for the negative and contribute to their conservation under the current level of tourism pressure.
|
|
| 42. |
- Le Vaillant, Maryline, et al.
(författare)
-
Spatial distribution in Norwegian lemming Lemmus lemmus in relation to the phase of the cycle
- 2018
-
Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 41:7, s. 1391-1403
-
Tidskriftsartikel (refereegranskat)abstract
- Competition between individuals of the same or different species affects spatial distribution of organisms at any given time. Consequently, a species geographical distribution is related to population dynamics through density-dependent processes. Small Arctic rodents are important prey species in many Arctic ecosystems. They commonly show large cyclic fluctuations in abundance offering a potential to investigate how landscape characteristics relates to density-dependent habitat selection. Based on long-term summer trapping data of the Norwegian lemming (Lemmus lemmus) in the Scandinavian Mountain tundra, we applied species distribution modeling to test if the effect of environmental variables on lemming distribution changed in relation to the lemming cycle. Lemmings were less habitat specific during the peak phase, as their distribution was only related to primary productivity. During the increase phase, however, lemming distribution was, in addition, associated with landscape characteristics such as hilly terrain and slopes that are less likely to get flooded. Lemming habitat use varied during the cycle, suggesting density-dependent changes in habitat selection that could be explained by intraspecific competition. We believe that the distribution patterns observed during the increase phase show a stronger ecological signal for habitat preference and that the less specific habitat use during the peak phase is a result of lemmings grazing themselves out of the best habitat as the population grows. Future research on lemming winter distribution would make it possible to investigate the year around strategies of habitat selection in lemmings and a better understanding of a fundamental actor in many Arctic ecosystems.
|
|
| 43. |
- Meijer, Tomas, et al.
(författare)
-
Life history traits in a cyclic ecosystem : a field experiment on the arctic fox
- 2013
-
Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 173:2, s. 439-447
-
Tidskriftsartikel (refereegranskat)abstract
- The reproduction of many species depends strongly on variation in food availability. The main prey of the arctic fox in Fennoscandia are cyclic small rodents, and its number of litters and litter size vary depending on the phase of the rodent cycle. In this experiment, we studied if the arctic fox adjusts its reproduction as a direct response to food abundance, in accordance with the food limitation hypothesis, or if there are additional phase-dependent trade-offs that influence its reproduction. We analysed the weaning success, i.e. proportion of arctic fox pairs established during mating that wean a litter in summer, of 422 pairs of which 361 were supplementary winter fed, as well as the weaned litter size of 203 litters of which 115 were supplementary winter fed. Females without supplementary winter food over-produced cubs in relation to food abundance in the small rodent increase phase, i.e. the litter size was equal to that in the peak phase when food was more abundant. The litter size for unfed females was 6.38 in the increase phase, 7.11 in the peak phase and 3.84 in the decrease phase. The litter size for supplementary winter-fed litters was 7.95 in the increase phase, 10.61 in the peak phase and 7.86 in the decrease phase. Thus, feeding had a positive effect on litter size, but it did not diminish the strong impact of the small rodent phase, supporting phase-dependent trade-offs in addition to food determining arctic fox reproduction.
|
|
| 44. |
|
|
| 45. |
- Meijer, Tomas, et al.
(författare)
-
Reproductive strategy in a cyclic environment
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The ability to maximize life-time reproductive output in relation to ecological variation in time and space is central for individual fitness. In cyclic environments the optimal litter size might vary over time depending on fluctuations in food abundance, offspring survival and their future fecundity. The arctic fox in Scandinavia is highly dependent on cyclic small rodents, such as lemmings and voles, for its reproduction. The arctic foxes can adjust their litter size in relation to small rodent phase, but this adjustment cannot be explained by food abundance only. In the rodent increase phase, litters are larger than expected from food abundance, while litters are smaller than expected in the decrease phase. In this paper, we studied how arctic fox litter size is associated with variation in the offspring reproductive value, specifically if the reproductive value is higher in the increase phase of the small rodent cycle. We followed the survival and fecundity, i.e. number of offspring, of 282 ear-tagged arctic foxes for a minimum of 4 years after birth in relation to small rodent phase. We found substantial variation in reproductive values, with a 3.2 times higher reproductive value for cubs born in the increase phase (0.74) compared to the decrease phase (0.23). The most pronounced difference in reproductive value between offspring born in different phases was caused by survival from birth to the end of their first year. Of the offspring born in the increase phase, 32% survived their first year compared to only 9% in the decrease phase. Our data supports that the observed phase dependent adjustment of arctic fox litter size has a demographic (and thereby an evolutionary) advantage by maximizing the number of offspring when the reproductive value is highest.
|
|
| 46. |
- Meijer, Tomas, 1980-
(författare)
-
To survive and reproduce in a cyclic environment – demography and conservation of the Arctic fox in Scandinavia
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns the conservation and life history of the Arctic fox (Vulpes lagopus) in Scandinavia. The Arctic fox was historically a widely distributed species in the Scandinavian mountain tundra with a population size of approximately 10 000 individuals during years with high resource availability, i.e. rodent peaks. However, due to over-harvest in the end of the 19th century, the population numbers declined to a few hundred individuals. Although legally protected for more than 80 years, the population has remained small. The main causes of the non-recovery have been attributed to irregularities in the lemming cycle and increased competitions with the larger red fox. Through conservation actions including red fox culling and supplementary feeding, the population has started to recover in parts of its former distribution range. The Arctic fox is highly adapted to the lemming cycle and determine whether to reproduce or not and adjust the litter size relation to small rodent phase in combination with food abundance. In the small rodent increase phase, females produce litters equal to the peak phase, despite higher food abundance in the later. This overproduction of cubs can be selected for through a higher juvenile survival and reproductive value of cubs born in the increase phase compared to the other phases. The most important component affecting the reproductive value seem to be the survival during the first year after birth. In the small rodent increase phase 32% of the cubs survives their first year compared to 9% in the decrease phase. The Arctic fox in Scandinavia constitute an example of how a species can adapt their reproductive strategy to a fluctuating environment by adjustment of the reproduction.
|
|
| 47. |
|
|
| 48. |
- Norén, Karin, et al.
(författare)
-
From monogamy to complexity : social organization of arctic foxes (Vulpes lagopus) in contrasting ecosystems
- 2012
-
Ingår i: Canadian Journal of Zoology. - 0008-4301 .- 1480-3283. ; 90:9, s. 1102-1116
-
Tidskriftsartikel (refereegranskat)abstract
- Canids display pronounced intraspecific variation in social organization, ranging from single breeding females to large and complex groups. Despite several hypotheses in this matter, little is understood about the ecological factors underlying this flexibility. We have used the arctic fox (Vulpes lagopus (L., 1758)) to investigate how contrasting ecosystem conditions concerning resources and predation influence group formation. We predicted that complex groups are more common in resource-rich ecosystems with predators, whereas simple groups occur in more marginal ecosystems without predators. Samples from 54 groups were collected from four populations of arctic foxes with contrasting prey resources and predation and these samples were genotyped in 10 microsatellite loci. We found considerable variation between ecosystems and a significant relationship between resources and formation of complex groups. We conclude that sufficient amounts of food is a prerequisite for forming complex groups, but that defense against predation further increases the benefits of living in larger groups. We present a conceptual model suggesting that a trade-off between the cost of resource depletion and the benefits obtained for guarding against predators explain the differences in social organization. The variable ecology of the arctic foxes makes it is a plausible model species for understanding the connection between ecology and social organization also in other species.
|
|
| 49. |
- Pasanen Mortensen, Marianne, 1971-
(författare)
-
Anthropogenic impact on predator guilds and ecosystem processes : Apex predator extinctions, land use and climate change
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Humans affect ecosystems by changing species compositions, landscape and climate. This thesis aims to increase our understanding of anthropogenic effects on mesopredator abundance due to changes in apex predator status, landscape and climate. I show that in Eurasia the abundance of a mesopredator, the red fox (Vulpes vulpes), is limited top-down by the Eurasian lynx (Lynx lynx) and bottom-up by winter severity. However, where lynx has been eradicated, fox abundance is instead related to bottom-factors such as cropland (paper I, II). Fox abundance was highest when croplands constituted 25% of the landscape (paper II). I also project red fox abundance in Sweden over the past 200 years and in future scenarios in relation to lynx density, land use and climate change. The projected fox abundance was highest in 1920, when lynx was eradicated and the proportion of cropland was 22%. In 2010, when lynx had recolonised, the projected fox abundance was lower than in 1920, but higher than in 1830. Future scenarios indicated that lynx abundance must increase in respond to climate change to keep fox at the same density as today. The results suggest a mesopredator release when lynx was eradicated, boosted by land use and climate change, and that changes in bottom-up factors can modify the relative strength of top-down factors (paper IV). From 1846-1922, lynx, wolverine (Gulo gulo) and grey wolf (Canis lupus) declined in Scandinavia due to persecution; however I show that the change in wolverine abundance was positively related to the changes in lynx and wolf abundance. This indicates that wolverine is subsidized by carrions from lynx and wolf kills rather than limited top-down by them (paper III). This thesis illustrates how mesopredator abundance is determined by a combination of top-down and bottom-up processes, and how anthropogenic impacts not only can change the structures of predator guilds, but also may modify top-down processes through changes in bottom-up factors.
|
|
| 50. |
- Pasanen-Mortensen, Marianne, et al.
(författare)
-
Land cover effects on mesopredator abundance in the presence and absence of apex predators
- 2015
-
Ingår i: Acta Oecologica. - : Elsevier BV. - 1146-609X .- 1873-6238. ; 67, s. 40-48
-
Tidskriftsartikel (refereegranskat)abstract
- Trophic downgrading due to loss of apex consumers has been detected in many ecosystems. Loss of larger predators implies that medium-sized mesopredators rise to the status of apex predators which are limited bottom-up rather than top-down. Hence the density of medium-sized predators should be more strongly related to land cover in absence of larger predators. We investigate this hypothesis at a continental scale (Eurasia) for a medium-sized predator, the red fox Vulpes vulpes, in presence and absence of an apex predator, the Eurasian lynx Lynx lynx. We predicted that in absence of lynx, fox density should be positively associated with open land covers, as these could favour foxes due to high prey availability. Our results showed that fox abundance was independent of land cover in presence of lynx. However, in absence of lynx, fox density was positively but asymptotically related to cropland, while negatively related to grassland. Fox density was highest when cropland constituted approximately 30% of the landscape, likely reflecting an optimal composition of foraging and breeding habitat. Grassland was associated with low productivity, likely reflecting low prey availability. Thus, cropland is favourable for red fox, but only in absence of top-down limitation by lynx. We suggest that there are two ecosystem states in Eurasia, one northern where lynx is present as an apex predator, and one south-eastern where red fox assumes the apex predator position and its abundance is subsidised by anthropogenic land cover.
|
|
