Habitat structure and association with ungulates drive habitat selection and grouping behaviour of lesser rhea (Rhea pennata subsp. pennata)

Social prey species respond to predation risk by modifying habitat selection and grouping behaviour. These responses may depend on both actual predation risk (predator probability of occurrence) and/or on perceived predation risk associated with habitat structure. Other factors like food availability and co-occurrence with other species may also affect habitat selection and group formation. We analyse habitat selection and grouping behaviour (group size and cohesion) of lesser rhea (Rhea pennata subsp. pennata), a ratite endemic of South America inhabiting steppe shrublands and grasslands, in relation to actual (puma probability of occurrence) and perceived (habitat structure: openness, visibility) predation risk, co-occurrence with other herbivore species and forage availability in the Chilean Patagonia. We used data from 9 sampling seasons in 5 years. Results show that habitat selection, group size and cohesion in lesser rhea were mainly driven by variables associated with perceived predation risk and by co-occurrence with other herbivores both during breeding and non–breeding season. As expected, lesser rhea preferred open habitats (vegas and grasslands) that allow a behaviour of ‘watch and run’ to avoid predation and formed larger groups in them. Moreover, lesser rhea positively selected year-round habitats where livestock occur, forming large groups during non–breeding season there. Group size and co-occurrence with other herbivores significantly decreased group cohesion, suggesting a reduction of perceived predation risk. Therefore, lesser rhea seems to take advantage of forming mixed interspecific groups to reduce predation risk. These results suggest that lesser rhea habitat selection and grouping behaviour are preferentially driven by factors related to perceived predation risk than by actual predator occurrence or food availability.     

Realised niche changes in a native herbivore assemblage associated with the presence of livestock

Habitat partitioning is a common ecological mechanism to avoid competition among coexisting species, and the introduction of new species into existing assemblages can increase competitive pressures. However, situations of species in allopatry and sympatry only differing in species presence but not in environmental conditions are scarce. Thus, discerning whether niche segregation arises from competition or from different habitat preferences is usually unfeasible. Here, we analyse species’ habitat niches in an assemblage of native and introduced herbivores in southern Patagonia. We test if niche overlap is higher between native and domestic herbivores than among natives as expected from the relatively short time of coexistence, and we evaluate the effect of intra‐ and interspecific competition on niche breadth. We use a probabilistic multidimensional approach and null models to evaluate overlap and changes in niche dimensions. Overlap among native species is low as expected for species coexisting in evolutionary time. In native‐domestic species pairs, niche overlap was higher than among natives, although showing some niche segregation indicating niche differentiation in ecological time. Moreover, the presence of domestic species was associated with niche narrowing of both native and introduced species, revealing interspecific density‐dependent effects on their habitat niche during resource shortage periods.     

Sexual differences in microhabitat selection of breeding little bustards Tetrax tetrax: Ecological segregation based on vegetation structure

We examined sexual differences in patterns of vegetation structure selection in the sexually dimorphic little bustard. Differences in vegetation structure between male, female and non-used locations during reproduction were examined and used to build a presence/absence model for each sex. Ten variables were measured in each location, extracting two PCA factors (PC1: a visibility-shelter gradient; PC2: a gradient in food availability) used as response variables in GLM explanatory models. Both factors significantly differed between female, male and control locations. Neither study site nor phenology was significant. Logistic regression was used to model male and female presence/absence. Female presence was positively associated to cover of ground by vegetation litter, as well as overall vegetation cover, and negatively to vegetation density over 30 cm above ground. Male presence was positively related to litter cover and short vegetation and negatively to vegetation density over 30 cm above ground. Models showed good global performance and robustness. Female microhabitat selection and distribution seems to be related to the balance between shelter and visibility for surveillance. Male microhabitat selection would be related mainly to the need of conspicuousness for courtship. Accessibility to food resources seems to be equally important for both sexes. Differences suggest ecological sexual segregation resulting from different ecological constraints. These are the first detailed results on vegetation structure selection in both male and female little bustards, and are useful in designing management measures addressing vegetation structure irrespective of landscape composition. Similar microhabitat approaches can be applied to manage the habitat of many declining farmland birds.     

Breeding biology of the endangered Dupont’s Lark Chersophilus duponti in two separate Spanish shrub-steppes

Capsule: The Dupont’s Lark Chersophilus duponti in Iberia has relatively high breeding success in both core and fragmented habitats, so population declines are more likely to be the result of low juvenile or adult survival.

Aims: To measure important aspects of the reproductive biology of one of the most endangered and least known larks: the Dupont’s Lark C. duponti.

Methods: We monitored 36 nests in 2 Spanish shrub-steppes, one holding one of the largest European populations (250 pairs) and one composed by fragmented habitat patches holding a smaller population (50 pairs).

Results: The breeding season went from late-March to early July. Overall mean (±sd) clutch size was 3.47?±?0.56, and the number of fledglings per successful nest was 3.0?±?1.15. Mean nestling period was short (8.2 days). Nests showed similar daily survival rate during the incubation period (0.9750?±?0.0110) as during the nestling period (0.9545?±?0.0168), with a mean breeding success of 50%. Predation was the main cause of complete nest failure (83.3% of failed nests in both localities).

Conclusion: Breeding parameters did show no significant variation between populations. Breeding success in both sites was generally higher than recorded in previous studies of this and most other lark species, which suggests that breeding success does not compromise long-term viability of these populations. The decline of the studied populations should be explained by other causes, such as a general decrease in habitat quality, habitat loss or habitat fragmentation.     

Determining high value areas for steppe birds in Spain: hot spots,complementarity and the efficiency of protected areas

We have examined the distribution of 26 species of steppe birds in the Iberian Peninsula and the Balearic Islands within a grid of 5,070 10 × 10 km grid cells. The most valuable areas for steppe birds have been identified by selecting the upper 5% of the 10 × 10 km grid cells after a simple ranking based on the following criteria: species-richness, richness of rare species, rarity index, species vulnerability at Spanish, European and Global levels, and using an index combining the previous criteria. We have also used a heuristic algorithm to select those areas which offered most complementarity. The results have been analysed on a national scale and have been compared with those obtained by species assessments in previous status summaries. Finally, we have performed an analysis of the coverage afforded to locations which are valuable for steppe species by Natural Protected Areas (NPAs) and Special Protected Areas (SPAs), and an evaluation of the potential effects of temporal changes in species’ threat-status. The combined index was the most reliable criterion for defining hotspots, encompassing 15% of the species’ distributions within 5% of the total area considered. This index showed a high level of geographical concordance with the other criteria (nearly 70% of the selected grid cells coincided). Analysis of complementarity delivered poorer results than simple rank-scoring. The analysis of the efficiency of NPA network showed a very low coverage (less than 2%) of the hotspots selected according to the Combined Index. Coverage of the SPA network was higher (nearly 45%), although it diminished (to <35%) when only steppe-defined SPAs were included. The geographical concordance between high-value areas selected using current status summaries and those chosen using earlier ones was low for European threat status (53.4%), intermediate (63.2%) for Spanish threat status and high for SPEC status (78.1%). The Combined Index showed a high level of geographical concordance between the old and new data (76.6%). We conclude that automatic scoring methods (identifying hotspots) are useful for selecting valuable areas and for analysing the efficiency of the network of protected natural spaces, as well as for examining the potential effects of status changes on hotspot definition. Furthermore, the Spanish SPA network does not cover the most important areas for steppe birds adequately.     

Determination of 25-hydroxycholecalciferol in serum

A precise specific method for measuring 25-hydroxycholecalciferol (25-OH CC) in 2 ml of human serum is described. It includes extraction with acetonitrile, separation with Sep-Pak C-18 cartridges, purification through HPLC and a further quantitation by means of a protein-binding assay. An exhaustive study of this protein-binding method has been performed. The sensitivity of the protein-binding assay is 20 pg/tube and the inter and intra-assay coefficients of variation are 9.6% and 8.7% respectively. The precision of the overall process has been assessed by calculating the inter and intra-assay coefficients of variation, 15.5 and 10.4% respectively. Mean serum value of 25-OH CC in normal subjects (18-50 years old, during spring) is 11.2 +/- 5.5 ng/ml.     

Diffusive dispersal in a growing ungulate population: guanaco expansion beyond the limits of protected areas

Growth of wild ungulate populations within protected areas can cause an expansion towards surrounding non-protected areas and lead to conflicts with human activities. The spatial and demographic structure of colonizing populations inform about their state and potential trends, since the initial colonization by dispersing individuals precedes the establishment of a population with potential for further growth and expansion. Once colonization has succeeded, the spatial pattern of animal abundance is associated with intra- and interspecific interactions and environmental factors (e.g., habitat and food availability) and the population shows similar demographic features throughout the whole occupation area, which has been called a diffusive dispersal pattern. Here, we analyze the current status of colonization by a guanaco population of ranches surrounding a protected area in Chilean Patagonia with data gathered along three consecutive years. We thus compared animal abundance and social structure between the protected and unprotected areas and evaluated throughout the whole area the effect of environmental factors on guanaco abundance, proportion of family groups, and reproductive success. Guanaco abundance significantly declined with increasing distance from the center of the local distribution and marginally with predation risk. Moreover, social structure showed only minor differences between areas, pointing to a diffusive dispersal pattern. These results suggest that the population is already well established and has the potential to grow and continue its expansion. The case exemplifies a challenging outcome of successful animal conservation, and it presents a useful approach to evaluate the state of wild ungulate populations colonizing new areas.     

Glucagon Regulation of Oxidative Phosphorylation Requires an Increase in Matrix Adenine Nucleotide Content through Ca2+ Activation of the Mitochondrial ATP-Mg/Pi Carrier SCaMC-3

It has been known for a long time that mitochondria isolated from hepatocytes treated with glucagon or Ca²⁺-mobilizing agents such as phenylephrine show an increase in their adenine nucleotide (AdN) content, respiratory activity, and calcium retention capacity (CRC). Here, we have studied the role of SCaMC-3/slc25a23, the mitochondrial ATP-Mg/P_i carrier present in adult mouse liver, in the control of mitochondrial AdN levels and respiration in response to Ca²⁺ signals as a candidate target of glucagon actions. With the use of SCaMC-3 knock-out (KO) mice, we have found that the carrier is responsible for the accumulation of AdNs in liver mitochondria in a strictly Ca²⁺-dependent way with an S_0.5 for Ca²⁺ activation of 3.3 ± 0.9 μm. Accumulation of matrix AdNs allows a SCaMC-3-dependent increase in CRC. In addition, SCaMC-3-dependent accumulation of AdNs is required to acquire a fully active state 3 respiration in AdN-depleted liver mitochondria, although further accumulation of AdNs is not followed by increases in respiration. Moreover, glucagon addition to isolated hepatocytes increases oligomycin-sensitive oxygen consumption and maximal respiratory rates in cells derived from wild type, but not SCaMC-3-KO mice and glucagon administration in vivo results in an increase in AdN content, state 3 respiration and CRC in liver mitochondria in wild type but not in SCaMC-3-KO mice. These results show that SCaMC-3 is required for the increase in oxidative phosphorylation observed in liver mitochondria in response to glucagon and Ca²⁺-mobilizing agents, possibly by allowing a Ca²⁺-dependent accumulation of mitochondrial AdNs and matrix Ca²⁺, events permissive for other glucagon actions.