Marcelo Hernán Cassini

Habitat use by vicuña Vicugna vicugna in Laguna Pozuelos Reserve, Jujuy, Argentina

Vicuna Vicugna vicugna are an emblematic species of one of the major arid ecosystems of the neotropics: the puna or altiplano. Excessive commercial hunting of vicuna for their valuable fleece in the past caused a severe decline in the population, with the vicuna almost becoming extinction by the mid 20th century. Effective protection resulted in the recovery of some populations and, recently, limited vicuna exploi- tation has been allowed. Research is urgently required to underpin the design of the management systems used for this exploitation. We present the result of a 2-year study on habitat utilization of vicuna in Laguna de Pozuelos UNESCO Biosphere Reserve in Argentina. Vicuna did not use the study area homogeneously but preferred vegetation communities dominated by grasses (known locally as pajonal and esporal) and with high overall plant cover. Vicuna were less selective in 2003, when overall habitat quality decreased, than in 2002. This change is predicted by habitat selection theory. We also found that members of family groups spend more time foraging than members of non-reproductive groups. Solitary vicuna spend more time standing up than members of groups, consistent with the observation that herding behaviour is related to protection against predators. Heterogeneous use and habitat selectivity suggest that exploitation of vicuna needs to take spatial behaviour into account in the establishment of the optimal location of capturing sites.

Population structure of coypus (Myocastor coypus) in their region of origin and comparison with introduced populations

The first population recapture study of indigenous coypus Myocastor coypus is reported in protected areas of Argentine pampas within a region where the species is hunted for food and fur. Quarterly live trapping at two sites captured a high proportion of all coypus present (96% of juveniles; 85% of adults, independently of season, site and sex). Survival (from mortality or emigration) was constant across sites and seasons, and higher for juvenile males than females (88% and 71%, respectively) and lower for adult males than females (45% and 81%). Most turn-over in numbers was replaced by births, and immigrating males tended to be the largest individuals present. Sex ratios were male-biased amongst juveniles and female-biased amongst adults. Taken together, these results are consistent with local resource competition in habitat rendered low in quality by crowding inside the locally protected areas. The indigenous coypu population matured more slowly, and to a smaller maximum body size, than coypus studied in introduced populations in North America and particularly in northern Europe. Cold European winters may have contributed to the evolution of precocious sexual maturity and larger body sizes in European compared with indigenous populations.

Ranking threats using species distribution models in the IUCN Red List assessment process

Within the Red List of the International Union for Conservation of Nature (IUCN), species distribution models (SDM) are used with two main purposes: (1) to estimate extents of occurrence as a parameter of risk of extinction and, more recently, (2) to explore potential impacts of climate change on species distribution. In this article I propose a third use of SDM: to generate objective and quantitative rankings of threats for the species categorized within the Red List. Although, some authors have published threat analyses based on SDM, most current ranking of threats conducted within IUCN Specialist Groups still relies on the subjective perspectives of workshop attendees or individual experts. I found that SDMs are ideal for incorporating theoretical and mathematical rigour to the ranking threat process, because: (1) they are of relatively easy and fast implementation, (2) they can be used with different levels of knowledge about the species in question, and (3) they are particularly suitable for use at the geographical scale for which the IUCN Red List is designed.

Relatedness and social organization of coypus in the Argentinean pampas

Behavioural and trapping studies of the social organization of coypus have suggested the occurrence of kin groups and a polygynous mating system. We used 16 microsatellite markers to analyse parentage and relatedness relationships in two populations (Jáuregui and Villa Ruiz) in the Argentinean Pampas. At Jáuregui, a dominant male monopolized most paternities, leading to a high variance in reproductive success between males and a high level of polygyny. At Villa Ruiz, variance in reproductive success was low among resident males and males were the fathers of zero to four offspring each. For females, no significant differences were found. Two different social groups in each study site were used to assess genetic relatedness within and between groups. These groups were neighbouring at Jáuregui but not at Villa Ruiz. At Villa Ruiz, coypus were significantly more related within than between groups, suggesting that behavioural groups were also genetic ones, and adult females were more related within than between groups, as should be expected for kin groups. This relationship was not found at Jáuregui. Our results provide support to previous studies based on behavioural and trapping data, which indicate that coypus form social groups and have a polygynous mating system. However, we found differences in social organization between the two populations. This is the first study to determine parentage and/or relatedness in coypus.

Local determinants of coypu distribution along the Lujan River, eastcentral Argentina

The coypu, or nutria (Myocastor coypus), is a semiaquatic rodent intensively harvested for fur and damage control. We conducted a survey along the Lujan River in Argentina to determine environmental factors affecting the distribution of coypu in its natural range. In each of 82 600-m transects randomly assigned along the river, we recorded the presence of coypu and habitat characteristics related to attributes of the river, nearby vegetation, and human activity. Coypu distribution was positively related to availability of grasslands used for extensive livestock production and negatively related to local human perturbations. Lowland prairies would provide an abundant and stable source of food to coypu, which could be used as a profitable natural resource in low productive areas of the Pampas region.

Distribution of Species

Ecological distribution models at the species level are applied to the whole range of species, although they are also frequently used at regional or national scales. In the first case, the subject of distribution ecology approaches that of ecological biogeography and niche ecology, depending on whether the main interest of the researcher is in producing distribution maps or reconstructing species’ ecological requirements. Section 7.2 forms the bulk of this chapter and describes the so-called species distribution models, which can be considered equivalent to the site suitability models described in Sects. 2.4 and 3.2, with the main differences being that they are applied on a coarser scale and use a wider range of statistical tools and some of them can be used to produce distribution maps. Species distribution models have three characteristics: (1) they apply to groups of populations at a coarse scale; (2) they emphasise the effect of environmental variables on internal processes; and (3) they do not use populations as the unit of study (with associated measurements of birth, death, and migration parameters), but the set of individuals is defined by categories determined by environmental heterogeneity or by arbitrary divisions of space (in most cases, cells on a grid superimposed on the landscape). Section 7.3 deals with the hypotheses that try to explain the shape of the function that best fits the distribution of species abundance within a biogeographic range and is almost entirely based on the analysis of Gaston (2003). Section 7.4 describes models at the level of species that are based on the physiological mechanisms involved in determining the causes of limits in species’ ranges, while the last section describes how species distribution models can be improved by incorporating information on behavioural traits of the target species.

Genetic structuring in a relictual population of screaming hairy armadillo (Chaetophractus vellerosus) in Argentina revealed by a set of novel microsatellite loci

The screaming hairy armadillo (Chaetophractus vellerosus) is a mammal species containing disjunct and isolated populations. In order to assess the effect of habitat fragmentation and geographic isolation, we developed seven new microsatellite loci isolated from low-coverage genome shotgun sequencing data for this species. Among these loci, six microsatellites were found to be polymorphic with 8–26 alleles per locus detected across 69 samples analyzed from a relictual population of the species located in the northeast of the Buenos Aires Province (Argentina). Mean allelic richness and polymorphic information content were 15 and 0.75, with observed and expected heterozygosities ranging from 0.40 to 0.67 and 0.58 to 0.90, respectively. All loci showed departures from Hardy–Weinberg equilibrium. The analysis of population structure in this relictual population revealed three groups of individuals that are genetically differentiated. These newly developed microsatellites will constitute a very useful tool for the estimation of genetic diversity and structure, population dynamics, social structure, parentage and mating system in this little-studied armadillo species. Such genetic data will be particularly helpful for the development of conservation strategies for this isolated population and also for the endangered Bolivian populations previously recognized as a distinct species (Chaetophractus nationi).

Distribution Ecology in Animal Production

Theoretical advances, made in the 1970s in relation to habitat selection behaviour and its ecological consequences in terms of spatial distribution patterns, also had an influence on animal production. Ideas from foraging theory, community ecology, and hierarchy theory were absorbed by researchers in the field of range management. This chapter deals only with applications to domestic species involved in animal production. There are other studies applicable to management of wild and game species that will not be considered (e.g. Bristow and Ockenfels 2004; Larsen et al. 2007). This chapter is divided into five sections related to foraging behaviour, landscape predictors, quantitative analyses, species models, and species assemblages’ approaches, all applied to the link between livestock distribution and animal production.

Distribution of Individuals

The distribution of individuals is a field mainly studied by behavioural sciences. It is largely concerned with animals, although some models can be applied to plants. Behavioural ecologists study decision rules that follow non-sessile individuals on when to start a movement; speed and direction of a movement; sites at which to stop, forage, be vigilant, or rest; and time spent for each activity. The result of these behaviours is an individual pattern of habitat use. Measured along the life of an animal, this pattern demarcates a home range. This chapter begins with a description of movement strategies in animals as mechanisms that result in an individual pattern of distribution. It is followed by two sections that discuss two types of descriptive models of individual habitat use: home-range estimations and site suitability models. The analytical approach is presented in the following two sections, and it is based on foraging theory, which developed models to predict residence times in foraging areas and to resolve the trade-off between forage and defence against predators. The chapter concludes with an analysis of the expected distributions at equilibrium.

Distribution Ecology in Conservation Biology

Conservation biology uses ecology as one of the main sciences that provide theoretical paradigms and methodologies to further its aim of developing solutions to the biodiversity crisis. Some of the most important areas of concern in conservation biology are sustainable management, protection of endangered species, design and management of protected areas, the preservation of ecosystems, and global climate change. Before analysing the contribution of distribution ecology to conservation biology, we will see a brief description of each of these areas. The contributions of distribution ecology to biodiversity conservation are arranged according to levels of organisation, in the following sections: individual (and gene) distribution, aggregated distributions, metapopulations and source–sinks, landscape ecology and pattern-based models, species distribution models, and ensemble distribution.