Spoor counts as indices of large carnivore populations: the relationship between spoor frequency, sampling effort and true density

1. Studies of large carnivore populations and, particularly, reliable estimates of population density are necessary for effective conservation management. However, these animals are difficult to study, and direct methods of assessing population size and density are often expensive and time-consuming.
2. Indirect sampling, by counting spoor, could provide repeatable and inexpensive measures of some population parameters. The relationship between true population density and indirect sampling results has seldom been described in large carnivore studies.
3. In northern Namibia the population densities of leopards, lions and wild dogs were measured through recognition of individuals and groups. Spoor counts were then conducted independently, to assess the relationship between true density and the distribution of spoor.
4. Sampling effort, both in terms of the number of roads and total road distance in a sample zone, and the intensity of sampling, had a marked effect on the accuracy and precision of spoor frequency calculations.
5. In a homogeneous habitat, leopard spoor were evenly spread along different roads and spoor frequency was independent of road length. Taking into account very low sample sizes, the spoor density of leopards, lions and wild dogs showed a strong linear correlation with true density. The slope of the regression for leopards was different to that of lions and wild dogs.     

Characterization of the In Vitro HIV-1 Capsid Assembly Pathway

During the morphogenesis of mature human immunodeficiency virus-1 cores, viral capsid proteins assemble conical or tubular shells around viral ribonucleoprotein complexes. This assembly step is mimicked in vitro through reactions in which capsid proteins oligomerize to form long tubes, and this process can be modeled as consisting of a slow nucleation period, followed by a rapid phase of tube growth. We have developed a novel fluorescence microscopy approach to monitor in vitro assembly reactions and have employed it, along with electron microscopy analysis, to characterize the assembly process. Our results indicate that temperature, salt concentration, and pH changes have differential effects on tube nucleation and growth steps. We also demonstrate that assembly can be unidirectional or bidirectional, that growth can be capped, and that proteins can assemble onto the surfaces of tubes, yielding multiwalled or nested structures. Finally, experiments show that a peptide inhibitor of in vitro assembly also can dismantle preexisting tubes, suggesting that such reagents may possess antiviral effects against both viral assembly and uncoating. Our investigations help establish a basis for understanding the mechanism of mature human immunodeficiency virus-1 core assembly and avenues for antiviral inhibition.     

Hardin Revisited: A Critical Look at Perception and the Logic of the Commons

With perhaps controversial implications for theory and practice, this paper suggests that the validity of Hardinian theories of the commons are dependent on the implicit rational choice assumption that resource users are aware of resource degradation. Without an awareness of the collective costs of resource use, there can be no dilemma between pursuing individual benefits and avoiding collective ruin. In such situations, the dilemma of the commons cannot be validly said to be the cause of resource depletion, and many traditional policy options to address common resource depletion may not be effective. Two reasons for the lack of awareness about resource degradation are (1) fatalistic beliefs that humans cannot harm a resource base, and (2) the growing complexity and abstraction of modern environmental problems that have obscured the collective costs of resource use from our individual and societal awareness.     

Translocation and early post-release demography of endangered Laysan teal

In an attempt to reduce the high extinction risk inherent to small island populations, we translocated wild Laysan teal Anas laysanensis to a portion of its presumed prehistoric range. Most avian translocations lack the strategic post-release monitoring needed to assess early population establishment or failure. Therefore, we monitored the survival and reproduction of all founders, and their first-generation offspring using radio telemetry for 2 years after the first release. Forty-two Laysan teal were sourced directly from the only extant population on Laysan Island and transported 2 days by ship to Midway Atoll. All birds survived the translocation with nutritional and veterinary support, and spent between 4 and 14 days in captivity. Post-release survival of 42 founders was 0.857 (95% CI 0.86–0.99) during 2004–2006 or annualized 0.92 (95% CI 0.83–0.98). Seventeen of 18 founding hens attempted nesting in the first two breeding seasons. Fledgling success was 0.57 (95% CI 0.55–0.60) in 2005 and 0.63 (95% CI 0.62–0.64) in 2006. The effective founding female population ( N _e) was 13. We applied these initial demographic rates to model population growth. The nascent population size increased to >100 after only 2 years post-release ( λ =1.73). If this growth rate continues, the size of the Midway population could surpass the source population before 2010.     

SecB-Mediated Protein Export Need Not Occur via Kinetic Partitioning

In Escherichia coli, the cytosolic chaperone SecB is responsible for the selective entry of a subset of precursor proteins into the Sec pathway. In vitro, SecB binds to a variety of unfolded substrates without apparent sequence specificity, but not native proteins. Selectivity has therefore been suggested to occur by kinetic partitioning of substrates between protein folding and SecB association. Evidence for kinetic partitioning is based on earlier observations that SecB blocks the refolding of the precursor form of maltose-binding protein (preMBP)⁵ and slow-folding maltose-binding protein (MBP) mutants, but not faster-folding mature wild-type MBP. In order to quantitatively validate the kinetic partitioning model, we have independently measured each of the rate constants involved in the interaction of SecB with refolding preMBP (a physiological substrate of SecB) and mature MBP. The measured rate constants correctly predict substrate folding kinetics over a wide range of SecB, MBP, and preMBP concentrations. Analysis of the data reveals that, for many substrates, kinetic partitioning is unlikely to be responsible for SecB-mediated protein export. Instead, the ability of SecB-bound substrates to continue folding while bound to SecB and their ability to interact with other components of the secretory machinery such as SecA may be key opposing determinants that inhibit and promote protein export, respectively.     

Stocking experiments with 0 + and 1 + trout parr, Salmo trutta L., of wild and hatchery origin: 2. Post-stocking movements

Wild and hatchery-reared 8–12-month-old (5–8 cm) trout, Salmo truttu L., were stocked into tributaries of the River Gudená. Movements were examined by means of electrofishing. Overall dispersal and upstream movement were greater for wild trout than for domestic trout. Maximum distance of movement was 600 m upstream for both strains and 600 m downstream for wild trout, and 700 m for domestic trout. Upstream movement started within 2 months from stocking and continued for at least 4 months. Downstream movement during the first few days after stocking, was more pronounced for domestic trout than for wild trout.     

Experimental release of an Iberian lynx (Lynx pardinus)

Reintroduction to the wild of threatened species has become a modern additional justification for captive propagation. This conservation procedure is costly, and both economic resources and the absence of optimal conditions in the field limit the IUCN recommendations for reintroduction to a small proportion of potential candidate species. Furthermore reintroduction attempts often fail. In carnivores, reintroduction failure is attributed to unsuitable adaptation in the field by captive-reared animals, due to their lack of hunting skills, their tendency to leave the target area, their inadequate interaction with conspecifics or their excessive confidence in humans. This list of causes is based on very few studies of carnivore adaptation after reintroduction. In very rare and endangered species, monitoring individual case-histories is the only way to evaluate reintroduction success. We report a successful experimental release of an Iberian lynx (Lynx pardinus) which grew up in captivity. Careful feeding-training and avoidance of human contact during the captive phase, as well as good habitat quality and correct interaction with other wild lynx in the release site, seem to account for the observed success. Permanence of the lynx within the release area might be related to the availability of territory vacancies in the receiving population. Our results allow some optimism for future reintroductions of this endangered species in areas where it has become extinct recently.     

Body size and fatness of free-living baboons reflect food availability and activity levels

We used morphometric techniques and isotope-labeled water to investigate the influence of abundant, accessible food and resultant low activity levels on body size and fatness in free-living adolescent and adult baboons as compared to animals in the same population that experienced more typical, wild-feeding conditions. Females that had access to abundant food from a nearby garbage dump averaged 16.7 kg body mass, 50% more than their wild-feeding counterparts in adjacent home ranges. Little of the difference was due to lean mass: the animals with an accessible abundance of food averaged 23.2% body fat in contrast to 1.9% for the wild-feeding animals. Significant differences between feeding conditions were found for all measured skinfolds and for upper arm circumference but not for linear measurements. Differences between feeding conditions were less for males than for females, perhaps reflecting persistent effects of nutritional conditions during the first eight years of life before dispersal from the group of birth. The difference in fatness between feeding conditions was similar to the difference between humans with frank obesity and those that are considered lean, but in both cases the percentages of body fat in the baboons were considerably less than those observed in humans. In levels of fatness, the relatively sedentary animals resembled their counterparts in group-housed captive conditions. © 1993 Wiley-Liss, Inc.     

Evidence for utility of the same PCR-based markers for selection of extreme resistance to Potato virus Y controlled by Rysto of Solanum stoloniferum derived from different sources

The tuber‐bearing wild potato species, Solanum stoloniferum, carries a dominant gene, Ry_sto, which confers extreme resistance (ER) to Potato virus Y (PVY). This gene was introgressed to cultivated potato germplasm (Solanum tuberosum) using accessions of S. stoloniferum maintained in European gene banks. It is mainly used in potato breeding programmes in Europe. Ry_sto was recently mapped to potato chromosome XII. However, in this study, a different accession of S. stoloniferum (PI275244; Haw1293) was used as a female parent in a cross to obtain a diploid (2n = 2x = 24) potato population of 112 F1 genotypes. From this accession, ER to PVY has been introgressed to the potato breeding programmes at the International Potato Center (Peru). As expected, ER to PVY was inherited in a dominant, monogenic fashion in the F1 population. Marker‐specific choices of DNA polymerase and adjustments of PCR conditions were made to optimise marker detection. The corresponding gene (Ry_sto) was mapped to the chromosome XII using the previously described and new cleaved amplified polymorphic sequence (CAPS) markers, which are based on the restriction fragment length polymorphism loci GP122 (six markers) and GP269 (one marker), and the simple sequence repeat marker STM0003. Four GP122‐based CAPS markers and STM0003 detected the same genotypes expressing ER to PVY. Because of a few recombinants, that is ER genotypes lacking the markers and the genotypes that react with necrosis but contain the markers, the marker distance from Ry_sto was estimated as 15.2 cM in this F1 population. However, the distance may be less if necrosis was considered an altered response also controlled by Ry_sto. The markers also specifically detected independent European potato cultivars that express ER to PVY derived from S. stoloniferum. Phylogenetic analysis of the sequences amplified from the GP122 locus of S. stoloniferum and potato cultivars further confirmed that the Ry_sto gene from independent accessions of S. stoloniferum can be selected using the same markers and the protocols described in this study.     

Correlates of reproductive success in a Caribbean village

Genealogical, demographic, and economic data collected in a rural Trinidadian village indicate that: (1) individuals with more land have more offspring, (2) males with more land have higher mating success, (3) young adults with parents resident in the village have higher reproductive success, and (4) the residence of father has a strong effect on young adult male reproductive success, but apparently has no effect on young adult female reproductive success, suggesting a gender bias in nepotism. The results indicate that there are important gender differences in the effect of resources on reproduction and in patterns of parent-offspring interaction.