Fredrik Dalerum

Resolving temporal variation in vertebrate diets using naturally occurring stable isotopes.

Assessments of temporal variation in diets are important for our understanding of the ecology of many vertebrates. Ratios of naturally occurring stable isotopes in animal tissues are a combination of the source elements and tissue specific fractionation processes, and can thus reveal dietary information. We review three different approaches that have been used to resolve temporal diet variation through analysis of stable isotopes. The most straightforward approach is to compare samples from the same type of tissue that has been sampled over time. This approach is suited to address either long or short-term dietary variation, depending on sample regime and which tissue that is sampled. Second, one can compare tissues with different metabolic rates. Since the elements in a given tissue have been assimilating during time spans specific to its metabolic rate, tissues with different metabolic rates will reflect dietary records over different periods. Third, comparisons of sections from tissues with progressive growth, such as hair, feathers, claws and teeth, will reveal temporal variation since these tissues will retain isotopic values in a chronological order. These latter two approaches are mainly suited to address questions regarding intermediate and short-term dietary variation. Knowledge of tissue specific metabolic rates, which determine the molecular turnover for a specific tissue, is of central importance for all these comparisons. Estimates of isotopic fractionation between source and measured target are important if specific hypotheses regarding the source elements are addressed. Estimates of isotopic fractionation, or at least of differences in fractionation between tissues, are necessary if different tissues are compared. We urge for more laboratory experiments aimed at improving our understanding of differential assimilation of dietary components, isotopic fractionation and metabolic routing. We further encourage more studies on reptiles and amphibians, and generally more studies utilizing multiple tissues with different turnover rates.

Human Hantavirus Infections, Sweden

The prevalent human hantavirus disease in Sweden is nephropathia epidemica, which is caused by Puumala virus and shed by infected bank voles (Clethrionomys glareolus). To evaluate temporal and spatial patterns of this disease, we studied 2,468 reported cases from a highly disease-endemic region in northern Sweden. We found that, in particular, middle-aged men living in rural dwellings near coastal areas were overrepresented. The case-patients were most often infected in late autumn, when engaged in activities near or within manmade rodent refuges. Of 862 case-patients confident about the site of virus exposure, 50% were concentrated within 5% of the study area. The incidence of nephropathia epidemica was significantly correlated with bank vole numbers within monitored rodent populations in part of the region. Understanding this relationship may help forestall future human hantavirus outbreaks.

The potential for large carnivores to act as biodiversity surrogates in southern Africa

Biodiversity in southern Africa is globally extraordinary but threatened by human activities. Although there are considerable biodiversity conservation initiatives within the region, no one has yet assessed the potential use of large carnivores in such actions. Surrogate approaches have often been suggested as one such way of capitalizing on large carnivores. Here we review the suitability of the large carnivore guild (i.e., brown hyaena Hyaena hyaena, spotted hyaena Crocuta crocutta, cheetah Acinonyx jubatus, leopard Panthera pardus, lion Panthea leo and African wild dog Lycaon pictus) to act as surrogate species for biodiversity conservation in southern Africa. We suggest that the guild must be complete for the large carnivores to fully provide their role as ecological keystones. The potential for large carnivores to act as umbrella and indicator species seems limited. However, self-sustaining populations of large carnivores may be useful indicators of unfragmented landscapes. Moreover, diversity within the large carnivore guild may reflect overall biodiversity. Although the global appeal of the large African carnivores makes them important international flagships, we stress that international conservation funding must be linked to local communities for them to be important also locally. In summary, we suggest that the flagship value of these large carnivores should be used to promote biodiversity conservation in the region, and that the suggested relationship between large carnivore diversity and overall biodiversity is empirically tested. Finally we suggest that direct conservation activities should focus on enhancing the keystone values of large carnivores through complete guild conservation and restoration.

A Trivers-Willard Effect in Contemporary Humans: Male-Biased Sex Ratios among Billionaires

Background Natural selection should favour the ability of mothers to adjust the sex ratio of offspring in relation to the offsprings potential reproductive success. In polygynous species, mothers in good condition would be advantaged by giving birth to more sons. While studies on mammals in general provide support for the hypothesis, studies on humans provide particularly inconsistent results, possibly because the assumptions of the model do not apply. Methodology/Principal Findings Here, we take a subset of humans in very good condition: the Forbes billionaire list. First, we test if the assumptions of the model apply, and show that mothers leave more grandchildren through their sons than through their daughters. We then show that billionaires have 60% sons, which is significantly different from the general population, consistent with our hypothesis. However, women who themselves are billionaires have fewer sons than women having children with billionaires, suggesting that maternal testosterone does not explain the observed variation. Furthermore, paternal masculinity as indexed by achievement, could not explain the variation, since there was no variation in sex ratio between self-made or inherited billionaires. Conclusions/Significance Humans in the highest economic bracket leave more grandchildren through sons than through daughters. Therefore, adaptive variation in sex ratios is expected, and human mothers in the highest economic bracket do give birth to more sons, suggesting similar sex ratio manipulation as seen in other mammals.

Diversity and depletions in continental carnivore guilds: implications for prioritizing global carnivore conservation

Large carnivores are important ecosystem components but are extinction prone due to small populations, slow growth rates and large area requirements. Consequently, there has been a surge of carnivore conservation efforts. Such efforts typically target local populations, with limited attention to the effects on the ecosystem function of predator guilds. Also, there is no framework for prioritizing these efforts globally. We compared taxonomic and functional diversity of continental carnivore guilds, compared them with the corresponding guilds during the Late Pleistocene and synthesized our results into suggestions for global prioritizations for carnivore conservation. Recent extinctions have caused taxonomically and functionally depleted carnivore guilds in Europe and North and South America, contrasting with guilds in Africa and Asia, which have retained a larger proportion of their carnivores. However, Asia is at higher risk of suffering further extinctions than other continents. We suggest three priorities of contrasting urgency for global carnivore conservation: (i) to promote recovery of the threatened Asian species, (ii) to prevent species in the depleted guilds in Europe and North and South America from becoming threatened, and (iii) to reconstruct functionally intact sympatric guilds of large carnivores at ecologically effective population sizes.

Lichen abundance in the peatlands of northern Alberta: Implications for boreal caribou 1

ABSTRACT In boreal forests, wildfire is a dominant ecological process that, among other things, affects the distribution and abundance of terrestrial lichens. Woodland caribou (Rangifer tarandus caribou) occupying peatland complexes of western Canada rely on terrestrial lichens for winter forage. Understanding the relationship between lichen distribution and fire is therefore important in order to understand caribou ecology. We documented abundance of terrestrial lichens in 73 peatland sites in northern Alberta, all within caribou home ranges. Forty-eight of these had been disturbed by forest fire within the past 70 y, while 25 had not been disturbed for at least 70 y. Peatlands that had not been disturbed for at least 70 y had low lichen cover (average 21.7 ±2.1%; range 4.6–54.0%) and lower lichen biomass (660.0 ±63.3 kg ·ha−1) than other studied boreal areas. However, lichen in sites disturbed by fire appeared to have recovered after only 40 y. This rapid recovery seems to have been mediated by a high growth rate: 4.8 ± 0.1 mm·y−1. Controlling for the effect of time since fire, lichen cover was inversely related to cover of Sphagnumspp., while growth rates of lichen were positively related to time since fire. Although the re-growth of lichen after fire was rapid in comparison to other systems, we suggest that fire has a strong effect on lichen distribution and hence on the spatial distribution of foraging habitat for Alberta caribou.

Interactive effects of species richness and species traits on functional diversity and redundancy

The importance of species diversity for ecosystem function has emerged as a key question for conservation biology. Recently, there has been a shift from examining the role of species richness in isolation towards understanding how species interact to effect ecosystem function. Here, we briefly review theoretical predictions regarding species contributions to functional diversity and redundancy and further use simulated data to test combined effects of species richness, number of functional traits, and species differences within these traits on unique species contributions to functional diversity and redundancy, as well as on the overall functional diversity and redundancy within species assemblages. Our results highlighted that species richness and species functional attributes interact in their effects on functional diversity. Moreover, our simulations suggested that functional differences among species have limited effects on the proportion of redundancy of species contributions as well as on the overall redundancy within species assemblages, but that redundancy rather was determined by number of traits and species richness. Our simulations finally indicated scale dependence in the relative effects of species richness and functional attributes, which suggest that the relative influence of these factors may affect individual contributions differently compared to the overall ecosystem function of species assemblages. We suggest that studies on the relationship between biological diversity and ecosystem function will benefit from focusing on multiple processes and ecological interactions, and that the relative functional attributes of species will have pivotal roles for the ecosystem function of a given species assembly.

Survival rates and causes of mortality of leopards Panthera pardus in southern Africa

The International Foundation of Science (D/4984-1), Wild Foundation (2008-011), Wilson Foundation and the University of Pretoria. LHS was further supported by the National Research Foundation (74819), FD by the National Research Foundation and a research fellowship from the University of Pretoria, and MJS by the Department of Science and Technology Centre of Excellence for Invasion Biology and the National Research Foundation.

Distribution, morphology and use of arctic fox Alopex lagopus dens in Sweden

In this article we describe 77 arctic fox Alopex lagopus dens in Vindelfjällen, northern Sweden, with regard to distribution, morphology and fox use. The density of dens in the area was 1/21 km2 and dens were more spaced than random. The dens were situated at a mean altitude (± SD) of 915 m a.s.l. ± 74, were on average 3.5 km ± 1.88 from the nearest tree line, had a mean number of 44 den openings ± 32 and a mean area of 277 m2 ± 237. During the 21-year study period, 31 dens were used by arctic foxes and 10 by red foxes Vulpes vulpes. Number of den openings, den area, altitude and distance to the nearest tree line explained 36% of arctic fox den use (P < 0.001) and 21 % of red fox use of arctic fox dens during the study period (P = 0.01). Arctic foxes used dens at higher altitude (P = 0.03) and further away from forest than did red foxes (P = 0.03), and tended to breed in dens with more openings (P = 0.08). Arctic foxes used some breeding dens more frequently than others (P = 0.002). Among the breeding dens, both den use and litter size were positively related to den area (den use: P = 0.04; litter size: P < 0.001). Successful arctic fox breeding dens in Sweden thus appear to be characterised by large size and many openings, and they are situated far away from forest at relatively high altitudes.

Diet of wolverines (Gulo gulo) in the western Brooks Range, Alaska

Migratory caribou herds are an important component of the North American tundra. We investigated the wolverine (Gulo gulo) diet in the migratory range of the Western Arctic Caribou Herd in north-western Alaska. Within this area, caribou are absent or occur at low densities for large parts of the year, and thus show a strong seasonality in abundance. Analyses of stomach and colon contents suggested that wolverines primarily consumed caribou during the winter, and that the dietary dependence was related more to caribou mortality than to caribou abundance in the area. We also found indications that wolverines may switch between moose and caribou during periods of low caribou abundance, but that such a switch did not affect wolverine body condition. Our results thus support previous observations that wolverines primarily consume ungulates. However, a better knowledge of how alternative food sources are utilized will be necessary to predict the dietary and demographic responses of wolverines to variations in caribou abundance. We also suggest that further efforts should be made to investigate the effects of other ungulate-dependent predators on wolverine feeding ecology, because such predators may function both as competitors and as suppliers of carrion for scavenging.