Statistical Inference from Capture Data on Closed Animal Populations

Stable isotope analysis is a useful tool to track animal movements in both terrestrial and marine environments. These intrinsic markers are assimilated through the diet and may exhibit spatial gradients as a result of biogeochemical processes at the base of the food web. In the marine environment, maps to predict the spatial distribution of stable isotopes are limited, and thus determining geographic origin has been reliant upon integrating satellite telemetry and stable isotope data. Migratory sea turtles regularly move between foraging and reproductive areas. Whereas most nesting populations can be easily accessed and regularly monitored, little is known about the demographic trends in foraging populations. The purpose of the present study was to examine migration patterns of loggerhead nesting aggregations in the Gulf of Mexico (GoM), where sea turtles have been historically understudied. Two methods of geographic assignment using stable isotope values in known-origin samples from satellite telemetry were compared: (1) a nominal approach through discriminant analysis and (2) a novel continuous-surface approach using bivariate carbon and nitrogen isoscapes (isotopic landscapes) developed for this study. Tissue samples for stable isotope analysis were obtained from 60 satellite-tracked individuals at five nesting beaches within the GoM. Both methodological approaches for assignment resulted in high accuracy of foraging area determination, though each has advantages and disadvantages. The nominal approach is more appropriate when defined boundaries are necessary, but up to 42% of the individuals could not be considered in this approach. All individuals can be included in the continuous-surface approach, and individual results can be aggregated to identify geographic hotspots of foraging area use, though the accuracy rate was lower than nominal assignment. The methodological validation provides a foundation for future sea turtle studies in the region to inexpensively determine geographic origin for large numbers of untracked individuals. Regular monitoring of sea turtle nesting aggregations with stable isotope sampling can be used to fill critical data gaps regarding habitat use and migration patterns. Probabilistic assignment to origin with isoscapes has not been previously used in the marine environment, but the methods presented here could also be applied to other migratory marine species.

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Determining origin in a migratory marine vertebrate: a novel method to integrate stable isotopes and satellite tracking

The Edumanon Forest Reserve is one of the least explored protected areas in the Niger Delta region of southern Nigeria, West Africa. In this article, we report the results of preliminary surveys, conducted between 2011 and 2014, for determining a checklist and a relative estimate of abundance for three groups of vertebrates, namely mammals, reptiles, and amphibians. Overall, we detected 69 vertebrate species (birds excluded), several of them being of high conservation concern. Among the most remarkable species from the conservation point of view, we can cite the chimpanzee, the manatee, and three species of sympatric crocodiles. Analysis of the reptile diversity suggested that species dominance was high and evenness was low, thus revealing altered ecological conditions in this forest area. Nonetheless, several forest specialists were still observed in this forest reserve. The conservation implications of the observed patterns, together with some ethnozoological data, are also discussed.

Preliminary surveys of the terrestrial vertebrate fauna (mammals, reptiles, and amphibians) of the Edumanon Forest Reserve, Nigeria

Many species of large wildlife have declined drastically worldwide. These reductions often lead to profound shifts in the ecology of entire communities and ecosystems. However, the effects of these large-wildlife declines on other taxa likely hinge upon both underlying abiotic properties of these systems and on the types of secondary anthropogenic changes associated with wildlife loss, making impacts difficult to predict. To better understand how these important contextual factors determine the consequences of large-wildlife declines on other animals in a community, we examined the effects of three common forms of large-wildlife loss (removal without replacement [using fences], removal followed by replacement with domestic stock, and removal accompanied by crop agricultural use) on small-mammal abundance, diversity, and community composition, in landscapes that varied in several abiotic attributes (rainfall, soil fertility, land-use intensity) in central Kenya. We found that small-mammal communities were indeed heavily impacted by all forms of large-wildlife decline, showing, on average: (1) higher densities, (2) lower species richness per site, and (3) different species assemblages in sites from which large wildlife were removed. However, the nature and magnitude of these effects were strongly context dependent. Rainfall, type of land-use change, and the interaction of these two factors were key predictors of both the magnitude and type of responses of small mammals. The strongest effects, particularly abundance responses, tended to be observed in low-rainfall areas. Whereas isolated wildlife removal primarily led to increased small-mammal abundance, wildlife removal associated with secondary uses (agriculture, domestic stock) had much more variable effects on abundance and stronger impacts on diversity and composition. Collectively, these results (1) highlight the importance of context in determining the impacts of large-wildlife decline on small-mammal communities, (2) emphasize the challenges in extrapolating results from controlled experimental studies to predict the effects of wildlife declines that are accompanied by secondary land-uses, and (3) suggest that, because of the context-dependent nature of the responses to large-wildlife decline, large-wildlife status alone cannot be reliably used to predict small-mammal community changes.

/pdf/context-dependent-effects-of-large-wildlife-declines-on-f15i5p77tx.pdf

Context-dependent effects of large-wildlife declines on small-mammal communities in central Kenya

Many species of large wildlife have declined drastically worldwide. These reductions often lead to profound shifts in the ecology of entire communities and ecosystems. However, the effects of these large-wildlife declines on other taxa likely hinge upon both underlying abiotic properties of these systems and on the types of secondary anthropogenic changes associated with wildlife loss, making impacts difficult to predict. To better understand how these important contextual factors determine the consequences of large-wildlife declines on other animals in a community, we examined the effects of three common forms of large- wildlife loss (removal without replacement (using fences), removal followed by replacement with domestic stock, and removal accompanied by crop agricultural use) on small-mammal abundance, diversity, and community composition, in landscapes that varied in several abiotic attributes (rainfall, soil fertility, land-use intensity) in central Kenya. We found that small- mammal communities were indeed heavily impacted by all forms of large-wildlife decline, showing, on average: (1) higher densities, (2) lower species richness per site, and (3) different species assemblages in sites from which large wildlife were removed. However, the nature and magnitude of these effects were strongly context dependent. Rainfall, type of land-use change, and the interaction of these two factors were key predictors of both the magnitude and type of responses of small mammals. The strongest effects, particularly abundance responses, tended to be observed in low-rainfall areas. Whereas isolated wildlife removal primarily led to increased small-mammal abundance, wildlife removal associated with secondary uses (agriculture, domestic stock) had much more variable effects on abundance and stronger impacts on diversity and composition. Collectively, these results (1) highlight the importance of context in determining the impacts of large-wildlife decline on small-mammal communities, (2) emphasize the challenges in extrapolating results from controlled experimental studies to predict the effects of wildlife declines that are accompanied by secondary land-uses, and (3) suggest that, because of the context-dependent nature of the responses to large-wildlife decline, large-wildlife status alone cannot be reliably used to predict small-mammal community changes.

https://labs.eemb.ucsb.edu/mccauley/doug/publications/Young%20et%20al%202015.pdf

Comparing species checklists across countries can be important for determining the relative uniqueness of each country, which can be conveniently defined on the basis of the number of species occurring only in that country or, at most, in one of its neighboring countries. Production of accurate country checklists is complicated by the fact that, especially in scientifically neglected regions, the knowledge of the distribution of many species is unsatisfying. When distribution of a given species is insufficiently known, typically there may be apparent gaps in its distribution range. These species are defined here as ‘gap species’. In this paper, we analyze the country checklists for rodents and insectivores of the African continent with the aims of (i) identifying the countries having a higher taxonomic uniqueness; (ii) highlighting countries where more research is needed; (iii) producing a list of gap species; and (iv) determining the ecological correlates of being a gap species. For both mammal groups, the important countries because of their low numbers of shared species were D.R. Congo, Cameroon, Sudan, Kenya, Tanzania, and South Africa. The countries with highest percentages of endemic taxa were Kenya, South Africa, Somalia and Tanzania for insectivores, and Ethiopia and South Africa for rodents. The number of gap species per country was 0–5 for both insectivores and rodents, with the only exceptions of Togo (12) and Benin (15). Apart from Togo and Benin, the main gap countries for rodents were Nigeria, Chad, Gabon, Burundi, and Rwanda, and for insectivores were Niger and Chad. In both groups, the number of gap species per country was independent on the country area, and both range and body sizes did not influence the probability for a species to have distribution gaps. However, most gap species were tropical forest inhabitants. The biogeographic and conservation implications of these data are discussed.

Spatial turnover and knowledge gap of African small mammals: using country checklists as a conservation tool

Comparative aspects of the demography were investigated in three distinct populations of the ecologically poorly studied rodent Eliomys quercinus, in Spain and Italy. Maximum longevity was observed in a Spanish female (survival of at least 2 years and 4 months). For all the populations under study, various closed population models and the robust design model gave similarly reliable estimates for population size, with Jolly–Seber estimates being considerably less reliable. The same result also emerged for the estimates of survival and capture probabilities, but with less profound differences between Jolly–Seber and the closed models with robust design. Average density showed considerable oscillations over the years and across localities, being nearly identical in northern and central Italy but considerably higher in Spain. Survival was considerably higher in Spain than in northern and central Italy. Conversely, capture probability was higher in northern Italy than in the other two study areas.

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Aspects of demography in three distinct populations of garden dormouse, Eliomys quercinus, across Italy and Spain

The causes of spatial distribution gaps for a given species may be either both natural (habitat discontinuities) or non-natural (local extinctions, inaccurate knowledge). These species are defined ...

Sabrina Masciola

Papers

Spatial turnover and knowledge gap of African small mammals: using country checklists as a conservation tool

Aspects of demography in three distinct populations of garden dormouse, Eliomys quercinus, across Italy and Spain

Spatial Turnover and Knowledge Gaps for African Chelonians Mirror those of African Small Mammals: Conservation Implications