Microhabitat Quality Research Articles

High thermal quality rookeries facilitate high thermoregulatory accuracy in pregnant female rattlesnakes

Temperature is a primary factor influencing organismal development, and the fluctuating daily and seasonal thermal regimes of temperate climates may challenge the ability of viviparous reptiles to optimize body temperatures during gestation. Testing how viviparous reptiles navigate highly variable thermal conditions (e.g., relatively cold nights and/or highly fluctuating temperatures) is a powerful way to understand how they use microhabitats for thermoregulatory benefits. We assessed the thermal ecology of pregnant and non-pregnant female Prairie Rattlesnakes (Crotalus viridis) inhabiting a high-elevation, montane shrubland in northwest Colorado throughout their short summer active season, addressing the thermal consequences of microhabitat selection with a focus on thermoregulation of pregnant females at communal rookery sites. We deployed operative temperature models to collect data on the thermal quality of microhabitats used by the snakes, and calculated thermoregulatory accuracy of the snakes by comparing their field-active body temperatures with preferred body temperatures of snakes placed in a thermal gradient. Pregnant females inhabited rocky, hilltop rookeries that had higher thermal quality due to higher and less variable nighttime temperatures compared to microhabitats in the surrounding prairie. Pregnant females therefore thermoregulated more accurately than non-pregnant females. The difference was most pronounced during the night, when pregnant females at rookeries maintained higher body temperatures than non-pregnant snakes in the prairie. Our results support the hypothesis that one major reason female rattlesnakes at high latitudes and/or high elevations forgo migration and gestate at communal, rocky, hilltop rookeries is that, relative to prairie microhabitats, they provide better conditions for thermoregulation during pregnancy.

Combining forest exploitation and heathland biodiversity: Edges structure drives microclimates quality and reptile abundance in a coniferous plantation

In Western Europe, natural habitats such as heathlands have been converted into many commercially managed forests, with severe impacts on biodiversity. In dense planted forests, forest edges are often the only suitable areas for ectothermic organisms highly dependent on open habitats for thermoregulation. Surprisingly, the influence of forest edges structure on the thermal quality of microhabitats and reptile species distribution remains poorly understood. In this study, we examined two reptile species and thermal quality of interior forest edges of a coniferous forest in Western France (Brittany). We focused on two hypotheses (i) the vegetation structure of the forest edges drives the thermal quality of the habitat and (ii) structural complexity of the forest edges influences the abundance of two heliothermic reptiles: the common adder (Vipera berus) and the common lizard (Zootoca vivipara). We first deployed temperature sensitive data loggers to quantify thermal conditions along 16 cross-sections of inner forest margins. For each section, 4 temperature loggers were placed at 1, 3, 5 and 7 m from the driveway and we examined the relation to vegetation structure and canopy cover. Second, we carried visual encounter surveys in 55 edges in order to measure the response of two reptiles to the structure of the forest margin along exploitation driveway. Our results show that high local canopy cover decreases microhabitat quality within interior forest edges. We also found that common lizard abundance was significantly influenced by the edge orientation and increased with global canopy openness and ground level vegetation. Adder abundance only increased significantly with the driveway width, suggesting the unmodelled effect of other biotic/abiotic variables. Our study shows that thermal quality of interior edges and driveway characteristics are relevant to support heathland reptile populations. We posit that maintain strips of favourable microhabitats should be an efficient land sharing strategy to combine forestry activities and biodiversity conservation.

Aggregated retention protects trees against wind, but not against disease: a long-term study in mixed forests

Retention forestry can help achieve multiple objectives in production forests, but its effectiveness is often low due to high mortality of the trees retained. We assessed the potential of improving tree survival in a low-level retention system in mixed forests by comparing the retention of multiple species of solitary trees (dispersed retention) and two approaches to aggregated retention. We annually monitored 58 dispersed-retention sites (since 2001) and 21 aggregated-retention sites (since 2013) in Estonia. Eight-year total mortality was 45% for solitary trees (and 1%–4% annually thereafter) but only 8% for tree groups; special planning for wind protection provided little further reduction. These estimates do not include dieback-affected Fraxinus excelsior L. that had distinct mortality dynamics independent of the retention pattern. Ulmus spp. also died frequently within the groups due to a dieback disease. Mixed-species tree groups enabled partial retention of Picea abies (L.) H. Karst that has extremely poor survival when retained solitarily. Likely, ecological costs of aggregated retention include some loss of microhabitat quality of individual trees. An optimal retention strategy could combine tree groups (maximizing wind protection and patch integrity) and individual trees (maximizing tree-scale biodiversity qualities), which collectively would also spread the risks of diverse mortality agents.

Using sonic tomography to assess the relationship between internal wood decay and saproxylic beetle communities

Although wood-inhabiting beetle species are known to contribute to the progressive degradation of wood by building larval galleries and dispersing fungal propagules, the relationship between decaying wood and beetle communities is difficult to be assessed. The ecological properties of trees, such as their mortality status and species, could modify the relationships between beetle communities and decaying wood. We used recently developed techniques of sonic tomography for the first time to address how the trophic structure of beetle communities varies with the internal wood decay. We developed a paired design where sonic tomograms taken in the trunk sections of live and dead trees of the Patagonian forest were related with beetles sampled with emergence traps. Beetles captured in the trunks of live trees responded weakly to the internal wood decay. Indeed, the diversity of predators in live trees was likely influenced by bark microhabitats. Conversely, most of the guild assemblages in the trunks of dead trees were impoverished as wood decay was more advanced, possibly due to decreasing microhabitat quality. Our preliminary study suggests sonic tomography offers the opportunity to distinguish how beetles modulate decaying wood, but also provides insights about the assessment of live trees with tomograms. • Internal wood decay was evaluated with sonic tomography. • Wood decay and beetle communities were associated. • Beetles in live trees responded weakly to wood decay. • Beetles in dead trees responded negatively to wood decay.

Vulnerability to global warming of the critically endangered Añelo Sand Dunes Lizard (Liolaemus cuyumhue) from the Monte Desert, Patagonia Argentina

The body temperature of lizards is strongly influenced by the thermal quality of microhabitats, exploiting the favourable environmental temperatures, and avoiding exposure to extreme thermal conditions. For these reasons, reptile populations are considered to be especially vulnerable to changes in environmental temperatures produced by climate change. Here, we study the thermal physiology of the critically endangered Añelo Sand Dunes Lizard (Liolaemus cuyumhue Avila, Morando, Perez and Sites, 2009). We hypothesise that (i) there is a thermal coadaptation between optimal temperature for locomotor performance of L. cuyumhue and its thermal preference; (ii) L. cuyumhue lives in an environment with low thermal quality; and (iii) a rise in environmental temperatures due to global warming will impose a decrement in locomotor speed represented by lower warming tolerance and narrower thermal safety margins, increasing their already high vulnerability. We recorded field body temperatures (T b), preferred body temperatures (T pref), the operative temperature (T e), and the thermal sensitivity of locomotion at different body temperatures. Our results indicate that this lizard is not currently under environmental stress or exceeding its thermal limits, but that it is thermoregulating below T pref to avoid overheating, and that an increase in environmental temperature higher than 3.5 °C will strongly affect the use of microhabitats with direct sun exposure.

Crops modify habitat quality beyond their limits

Edge effect is a strong driver of change in fragmented landscapes. In the last few decades, agricultural land-use intensity at field scale has increased and, consequently, the edges between crops and natural vegetation matrix have sharpened. Interspersed crops produce now negative effects not only by direct habitat destruction, but also by inputs of agrochemicals that may spread their effects on the surroundings. These processes are taking place worryingly in steppe habitats in Iberian Peninsula where the high diversity of bird communities and other taxa they hold is at risk. The aims of this study were to evaluate the edge effect of crops on i) the microhabitat quality of a natural landscape matrix and ii) the space use of a threatened habitat-specialist steppe bird, the Dupont’s lark (Chersophilus duponti). We carried out microhabitat sampling and bird surveys within and around crops interspersed in a typical Iberian shrub-steppe matrix during spring and autumn 2016 and spring 2017. Microhabitat quality was measured by sampling vegetation structure and arthropod biomass (as proxy of food availability) within and at increasing distances (1, 10 and 50 m) to seven crops. The intensity of space use by the Dupont’s lark was estimated applying a Kernel density function on the spatial point pattern of the males’ territories. Vegetation structure variables were summarized by Principal Components Analysis. Linear Mixed Models and model averaging were used to test for effects of distance to crop on microhabitat quality and space use by the Dupont’s lark. Distance to crop significantly affected microhabitat quality. A patchy structure of herbaceous and shrub was found outside crops in all sampling dates, with more shrub cover and less herbaceous cover as the distance to crops increased. Biomass of hypogeous arthropods significantly decreased when the distance to crops was lower than 50 m. The intensity of space use by Dupont’s lark varied according to the sampling date, being higher in spring, and as the distance to crops and the biomass of hypogeous arthropods increased. Negative effects of crops on the space use of this bird species might be shaped both by the effect of the crop itself and by its edge effect on hypogeous arthropods. Our results point to an edge effect of crops of 10–50 m on natural vegetation structure, arthropod availability and use of space by the Dupont`s lark, which suggests that the effective area of optimal habitat available for true steppe species could be overestimated.

Ant Guild Identity Determines Seed Fate at the Post-Removal Seed Dispersal Stages of a Desert Perennial.

Simple SummaryAnts play a dual role in their interaction with plant seeds. Many ant species, mainly harvester ants, consume plant seeds (granivory), whereas other ants, mainly scavengers, provide a beneficial seed dispersal service. Granivory by ants is frequently documented in deserts, but beneficial seed dispersal is rarely studied in such ecosystems. We followed the handling of seeds of Sternbergia clusiana, an ant-dispersed plant, by two guilds of desert ants. We focused on the treatment of seeds within the nest and on the redispersal of seeds after ejection from the nest. Scavenging ants rarely consumed the seed itself, they deposited most seeds away from the nest in apparently suitable microhabitats. In addition, we found that most of the seeds that were relocated by scavenging ants arrived at sites under the canopy of shrubs. Such sites might be beneficial for the establishment and success of plants in the arid environment. Indeed, we found that the subject plant was more likely to be found under shrubs than elsewhere, which suggests that it benefits from being placed there. Such documentation of seed dispersal activity by scavenging ants in arid ecosystems suggests they may be efficient seed dispersers in deserts, as they are in other ecosystems.Ants play a dual role in their interaction with plant seeds. In deserts, the consumption of seeds by granivorous ants is common, whereas mutualistic seed dispersal, often associated with scavenging ants, is rarely documented. We evaluated the contribution of both ant guilds to efficient seed dispersal of an ant-dispersed plant, Sternbergia clusiana, in a desert ecosystem. We presented seed to colonies of three species of desert ants from the Cataglyphis (scavengers) and Messor (granivorous) genera. We recorded seed consumption, ejection from the nest, and seed transportation to potentially beneficial microhabitats. We evaluated microhabitat quality by testing the association between habitat types and the plant at various life stages. As expected, granivores mainly consumed the seeds, whereas scavengers consumed the elaiosome (seed appendage serving as a reward), but left the seeds intact. Moreover, scavenging ants relocated the seeds much further than granivores, mainly to shrub patches. The disproportional distribution of the plant under shrubs at several life stages suggests that this microhabitat is beneficial for the plant. Overall, while granivores seem to mainly harm seed dispersal, we provide the first evidence for the beneficial contribution of scavenging ants in deserts, showing they exhibit the same suite of characteristics that render them efficient seed dispersers in other ecosystems.

Exploring the reproductive ecology of the tropical semifossorial snake Ninia atrata.

Based on histological analyses and field studies, this research describes the reproductive ecology of a population of Ninia atrata snakes inhabiting an oil palm plantation. Furthermore, through a multivariate approach, we explored the main drivers of reproductive output in N. atrata. Results showed that prey abundance and food intake were crucial variables contributing to reproductive output. Multiple linear regression models showed that neonates had high sensitivity (R2=55.29%) to extreme changes in climate, which was strongly related to slug and snail abundance variability and microhabitat quality. Reproductive cycles were markedly different between the sexes, being continuous in males and cyclical in females. Despite this variation, reproductive cycles at the population level were seasonal semi-synchronous. Constant recruitment of neonates all year, multiple clutches, high mating frequency, and continuous sperm production characterized the reproductive phenology of N. atrata. In addition, a significant number of previtellogenic females presented oviductal sperm as well as uterine scars, suggesting a high precocity in the species. The main drivers of reproductive output also differed between the sexes. In females, clutch size and secondary follicle variability were highly related to stomach bolus volume, fat body area, and body mass. In males, height of piles of palm leaves and body mass, rather than intrinsic reproductive traits, were the main drivers of sperm production. Nevertheless, in both cases, the relationship between body mass, prey abundance, and food intake suggests that N. atrata follows the income breeding strategy to compensate for reproductive costs and to maximize fitness.

Local landscapes and microhabitat characteristics are important determinants of urban–suburban forest bee communities

AbstractDespite their diversity and abundance, the importance of native, forest bee communities to pollination services and inherent biological diversity conservation is often overlooked. We studied forest bee communities in Delaware and Pennsylvania, USA, to better understand how forest bee community structure varies with changing land use and microhabitat quality among small, urban and suburban forest fragments in the mid‐Atlantic United States. Our hypotheses were that (1) microhabitat quality would affect relative abundance of bee taxa, (2) surrounding landscape composition would drive local patch colonization–extinction dynamics, and (3) forest patch size would not affect community structure and composition. We found a lack of spatial autocorrelation among forest patches, indicating the importance of individual fragments in the autonomous generation and/or maintenance of bee communities. Community analyses revealed the importance of both landscape context and microhabitat quality in defining forest bee communities. By partitioning beta diversity into its constituent components, we also found that landscape composition drove changes in the relative abundance of taxa, while both landscape and microhabitat characteristics significantly influenced species turnover. Neither landscape composition nor quality of the microhabitat influenced initial site occupancy or colonization–extinction dynamics. Bisected by highways, suburban neighborhoods, agricultural lands, and urban development, many urban and suburban forest patches in the eastern United States are similar in composition to our study sites. As many native forest bees have limited capacity for long‐range movement between forest patches, these remaining forest fragments are critical to the conservation of unique and speciose forest bee communities.

Life is uncertain, eat dessert first: feeding ecology and prey-predator interactions of the coffee snake Ninia atrata

ABSTRACTPrey-predator interactions are considered one of the primary drivers of the ecology and evolution of several vertebrate taxa, but particularly, it has played a significant role in the evolutionary biology of snakes. However, feeding ecology of semifossorial tropical snakes has been poorly studied. We employed a multivariate approach to explore the effects of sexual dimorphism, prey-predator interaction, and climatic variability due to El Niño–Southern Oscillation (ENSO) on the abundance and feeding ecology of the semifossorial snake Ninia atrata. Climatic variability analysis revealed conspicuous temporal variation in the prey availability at microhabitat, as well as in the snake abundance and food intake. Multivariate approach provided strong support for links between Ninia atrata abundance, microhabitat quality and snails abundance (more than other prey). Conspicuous intersexual dietary divergence was observed supporting the hypothesis of the sex-specific targets for maximum food intake. ENSO phenomenon promoted a notable decline in Ninia atrata abundances and its food intake, which was related to prey availability and abundance, as well as a strong variability on their body condition index (BCI). Finally, given the high sensitivity of Ninia atrata to the environmental variability, it could consider an indicator species of the environmental changes in the Neotropical oil palm agroecosystems.

Putative local adaptations modulate the interactions of the carnivorous plant Drosera uniflora Willd (1809) (Droseraceae) with cushion and shrub nurse plants

AbstractCushion and shrub plants are typical high mountain nurse plants. In Magellanic tundras of the Cordillera del Sarao on the coast of Chile, the carnivorous plant Drosera uniflora grows in association with cushions of Donatia fascicularis and the shrubs Chusquea montana var. nigricans and Lepidothamnus fonkii. The different microhabitats for recruitment, in addition to the limited gene flow of D. uniflora, enable us to hypothesise that this plant manifests putative local adaptations, expressed in seed germination and population abundance. Our aim was to evaluate the local adaptation of D. uniflora to cushion and shrub microhabitats by estimating germination and abundance. Local adaptation of seed germination was determined by means of reciprocal transplant experiments. Abundance was determined in small plots located inside, on the edge and outside the nurse plants. Seed origin and growth substrate play a decisive role in D. uniflora germination. Seeds that originate from cushions plant habitat and germinate in the same substrate do so in greater numbers than when those which originate from shrubby habitats. Conversely, seeds that originate from shrubby habitat and germinate in the same substrate do not exhibit significant differences. Abundance was always greater inside than outside of the nurse plants. We concluded that availability and quality of different microhabitats for seed germination and recruitment, together with a limited gene flow, would trigger putative local adaptations in D. uniflora, modulating a long history of interactions with the plants that act as nurse plants.

Drivers of Psammodromus algirus abundance in a Mediterranean agroforestry landscape

Mediterranean European landscapes have been shaped by human activities for centuries, particularly by livestock and farming. Traditionally managed montado landscapes have been recognized as having a crucial role in biodiversity conservation, providing habitat complexity and thus, ecological conditions for a variety of species. Biodiversity associated with montado can only be maintained under specific agricultural practices, with the intensification or abandonment of such practices posing serious threats for wildlife. Despite the high number of reptile species endemic to the Iberian Peninsula, research on the influence of agroforestry management practices on these species has been scarce. The mediterranean lizard Psammodromus algirus is a generalist species that responds to changes in the structure and quality of microhabitats, specifically the shrub layer, which is greatly affects by changes in cattle grazing intensity. In this study, we assessed how grazing affects the frequency of occurrence of P. algirus in a Mediterranean landscape dominated by montado. We detected that areas of intermediate age regarding grazing exclusion support higher lizard abundance, with P. algirus abundance being limited by vegetation structure and solar radiation. Thus, we may infer that the vegetation structure regulatory role of cattle will affect this lizard’s abundance, limiting it indirectly. We suggest that the maintenance of adequate traditional management, allowing the grazing pressure at low to moderate levels, would be beneficial to this species and reptiles in general and conclude that reconciling grazing and reptile conservation is possible if done in a sustainable way.

OUP accepted manuscript

Colonies of social insects exhibit a spectacular variety of life histories. Here we documented the degree of variation in colony life-history traits, mostly related to productivity, in two species of wild paper wasps. We then tested for associations between colony life-history traits to look for trade-offs or positively associated syndromes, and examined whether individual differences in the behavioral tendencies of foundresses (Polistes metricus) or the number of cofoundresses (P. fuscatus) influenced colony life-history. The majority of our measures of colony life-history were positively related, indicating no obvious resource allocation trade-offs. Instead, the positive association of traits into a productivity syndrome appears to be driven by differences in queen or microhabitat quality. Syndrome structure differed only marginally between species. Queen boldness and body size were not associated with colony life-history in P. metricus. Colonies initiated by multiple P. fuscatus foundresses were generally more productive, and this advantage was approximately proportional to the number of cofoundresses. These findings demonstrate that colony life-history traits can be associated together much like individual life-history traits, and the associations seen here convey that differences in overall productivity drive between-colony differences in life-history.

The influence of wild boar (Sus scrofa) on microhabitat quality for the endangered butterfly Pyrgus malvae in the Netherlands

The decline of open habitats in Europe, such as semi-natural grasslands and heathlands, has caused a general decline in biodiversity, which has been well documented for butterflies. Current conservation practices often involve grazing by domestic livestock to maintain suitable butterfly habitats. The extent to which wild ungulates may play a similar role remains largely unknown. Through their rooting activity, wild boar could be effective to reduce grass encroachment and restore pioneer microhabitats that are vital to many grassland insects in temperate climates. Here, we assessed the microhabitat requirements of Pyrgus malvae, an endangered butterfly of heathland and grassland habitats in the Netherlands, with special attention for the influence of wild boar rooting. To date, oviposition site selection of this species has concentrated on calcareous grasslands, whereas we also include heathlands. Overall, larval occupancy was higher in warm, open and sparsely vegetated microhabitats, which supports earlier findings. In heathland, microhabitat occupancy was positively affected by bryophyte and litter cover. In heath-grassland mosaic, microhabitat occupancy was also influenced by bryophyte and litter cover, but in addition low grass cover increased occupancy by favouring host plants. In grassland, only low grass cover and host plant cover determined microhabitat quality. Across all habitats, occupied microhabitats were characterized by lower vegetation as well as higher average daytime temperatures than unoccupied microhabitats. We discovered that wild boar play an important role in reducing grass cover by shallow rooting in grass patches, thereby increasing host plant availability. Hence, wild boar may have an added value in maintaining and restoring P. malvae microhabitats in grassland habitats in addition to grazing by domestic livestock.

Association between Constrictotermes cyphergaster (Silvestri, 1901) (Isoptera: Termitidae) with Pilosocereus gounellei (Weber ex Schum) Byles & Rowley (Cactaceae) at the Northeastern Brazil

Termites are important components of tropical ecosystems, as decomposers and for their outstanding role in feeding guilds. There are about 2,800 species of termites in terrestrial ecosystems, organized into seven families. Factors that determine abundance in termite colonies are soil type, quality of microhabitat, humidity, and availability of food resources. The species Constrictotermes cyphergaster (Silvestri, 1901) belongs to the Family Termitidae and to the Subfamily Nasutitermitinae. Termites in this taxon are characterized by building their nests in arboreal environments and rocks. Ecological interactions of termites and cactaceans are still scarcely studied. The research was done during the year of 2014, at the Experimental Station of the Federal University of Paraíba, located in the Municipality of São João do Cariri, State of Paraíba, Brazil. A quadrant with a total area of 2,500 m2 was delimited. Fifteen random samples of Pilosocereus gounellei (Weber ex Schum) Byles & Rowley containg termites, and 15 random samples without termites, were chosen. We report a previously unreported relationship between these organisms, and analize the relationship existing between the size of the cactaceans and the occurrence of termite mounds. We conclude that the relationship between the cactacean P. gounellei and the termite C. cyphergaster is one of herbivory of the later over the former. After consuming all the living tissues of the plants, the termites abandon the plant, because these cactaceans no longer provides the necessary conditions for the survival of termites. Xique-xique associated with termite mounds show visual signs of suffocating debilitation, leading to the total collapse of the cactaceans.

Hanging in the treetops: anin situexperiment in ancient hemlock assessing outbreak defoliator performance among crown levels

1. Past studies have shown that both egg lay and larval feeding of a generalist defoliator, pale-winged gray (Iridopsis ephyraria Walker) (Lepidoptera: Geometridae), are concentrated in the mid-lower crown of eastern hemlock [Tsuga canadensis (L.) Carr.]. 2. Using tree-climbing techniques, we carried out in situ bioassays in large hemlock trees (∼25 m) to determine whether the observed foraging preferences are adaptive and how they reflect associated intra-tree variations in microhabitat quality associated with temperature and foliage nutritional quality. 3. In 1 of 2 years, larval survival was significantly higher in the shaded lower versus sunlit upper crown; however, in both years, groups that fed in the sunlit upper crown branches had larger male and female moths and more female-biased sex ratios. 4. Differences in pale-winged gray performance among crown levels were somewhat supported by trends in foliage nutritional chemistry but not well-correlated with variation in temperature. 5. The present study is one of only a few to carry out bioassays on large mature trees and results reinforce the idea that foraging patterns of herbivores are likely to reflect trade-offs among several factors that vary between sunlit and shaded branches within forest canopies.

Wildlife Habitat Is Similar at Mined Versus Unmined Sites 30 Years Following Surface Mining for Coal in Southern Illinois

AbstractRiparian ecosystems provide important habitat for wildlife and serve as corridors for animal movements. Surface mining activities clearly impact wildlife habitat by removing vegetation needed by wildlife. However, few studies have assessed longer‐term success of habitat restoration in riparian ecosystems following surface mining. During 2012–13, we evaluated microhabitat quality at three stream segments restored 30 years ago following surface mining for coal and one unmined stream segment in Perry County, Illinois. Microhabitat differences were very minor among restored and control stream sites. Of the 41 habitat variables measured, 14 differed among sites, four of which were uncorrelated: canopy cover, overstory hard mast, bare ground, and herbaceous ground cover; thus, restored riparian buffers were comparable to unmined sites, indicating that habitat restoration efforts were successful. Our analysis from data collected at Burning Star 4 mine in Perry County, Illinois, is of value to land managers for it shows how the reclamation process has successfully jump‐started wildlife habitat in buffers around streams affected by mining.

Microhabitat Conditions in Wyoming's Sage-Grouse Core Areas: Effects on Nest Site Selection and Success.

The purpose of our study was to identify microhabitat characteristics of greater sage-grouse (Centrocercus urophasianus) nest site selection and survival to determine the quality of sage-grouse habitat in 5 regions of central and southwest Wyoming associated with Wyoming’s Core Area Policy. Wyoming’s Core Area Policy was enacted in 2008 to reduce human disturbance near the greatest densities of sage-grouse. Our analyses aimed to assess sage-grouse nest selection and success at multiple micro-spatial scales. We obtained microhabitat data from 928 sage-grouse nest locations and 819 random microhabitat locations from 2008–2014. Nest success was estimated from 924 nests with survival data. Sage-grouse selected nests with greater sagebrush cover and height, visual obstruction, and number of small gaps between shrubs (gap size ≥0.5 m and <1.0 m), while selecting for less bare ground and rock. With the exception of more small gaps between shrubs, we did not find any differences in availability of these microhabitat characteristics between locations within and outside of Core Areas. In addition, we found little supporting evidence that sage-grouse were selecting different nest sites in Core Areas relative to areas outside of Core. The Kaplan-Meier nest success estimate for a 27-day incubation period was 42.0% (95% CI: 38.4–45.9%). Risk of nest failure was negatively associated with greater rock and more medium-sized gaps between shrubs (gap size ≥2.0 m and <3.0 m). Within our study areas, Wyoming’s Core Areas did not have differing microhabitat quality compared to outside of Core Areas. The close proximity of our locations within and outside of Core Areas likely explained our lack of finding differences in microhabitat quality among locations within these landscapes. However, the Core Area Policy is most likely to conserve high quality habitat at larger spatial scales, which over decades may have cascading effects on microhabitat quality available between areas within and outside of Core Areas.

Habitat connectivity as a metric for aquatic microhabitat quality: application to Chinook salmon spawning habitat

AbstractQuality of fish habitat at the scale of a single fish, at the metre resolution, which we defined here as microhabitat, has been primarily evaluated on short reaches, and their results have been extended through long river segments with methods that do not account for connectivity, a measure of the spatial distribution of habitat patches. However, recent investigations of quality of aquatic habitat at the stream segment scale, at hundredth of metre resolution macrohabitat, indicate that the spatial distribution of aquatic habitat quality and size is an important factor at the network scale. Here, we hypothesize that aquatic habitat connectivity, quality and patch size are also important at the microhabitat scale. We test this hypothesis by modelling Chinook salmon (Oncorhynchus tshawytscha) spawning habitat in a 6‐km long reach of Bear Valley Creek (Idaho, USA) with microhabitat resolution of 1‐m square. We use two‐dimensional hydraulic numerical modelling coupled with suitability curves to predict the spatial distribution of spawning habitat quality. We quantify connectivity for each habitat patch with the ratio between the area of neighbouring patches and their squared hydrographic distances. Results from a logistic regression analysis comparing predicted with observed spawning locations indicate that habitat quality and patch size are important factors and connectivity among patches may have a secondary effect. Therefore, spatial distribution of aquatic habitat and size of habitat patches are important aspects of its quality, suggesting that composite metrics such as weighted usable area may not be sufficient in defining the condition of the river environment. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Synergistic effects of fire and elephants on arboreal animals in an African savanna.

Disturbance is a crucial determinant of animal abundance, distribution and community structure in many ecosystems, but the ways in which multiple disturbance types interact remain poorly understood. The effects of multiple-disturbance interactions can be additive, subadditive or super-additive (synergistic). Synergistic effects in particular can accelerate ecological change; thus, characterizing such synergies, the conditions under which they arise, and how long they persist has been identified as a major goal of ecology. We factorially manipulated two principal sources of disturbance in African savannas, fire and elephants, and measured their independent and interactive effects on the numerically dominant vertebrate (the arboreal gekkonid lizard Lygodactylus keniensis) and invertebrate (a guild of symbiotic Acacia ants) animal species in a semi-arid Kenyan savanna. Elephant exclusion alone (minus fire) had negligible effects on gecko density. Fire alone (minus elephants) had negligible effects on gecko density after 4 months, but increased gecko density twofold after 16 months, likely because the decay of fire-damaged woody biomass created refuges and nest sites for geckos. In the presence of elephants, fire increased gecko density nearly threefold within 4 months of the experimental burn; this occurred because fire increased the incidence of elephant damage to trees, which in turn improved microhabitat quality for geckos. However, this synergistic positive effect of fire and elephants attenuated over the ensuing year, such that only the main effect of fire was evident after 16 months. Fire also altered the structure of symbiotic plant-ant assemblages occupying the dominant tree species (Acacia drepanolobium); this influenced gecko habitat selection but did not explain the synergistic effect of fire and elephants. However, fire-driven shifts in plant-ant occupancy may have indirectly mediated this effect by increasing trees' susceptibility to elephant damage. Our findings confirm the importance of fire × elephant interactions in structuring arboreal wildlife populations. Where habitat modification by megaherbivores facilitates co-occurring species, fire may amplify these effects in the short term by increasing the frequency or intensity of herbivory, leading to synergy. In the longer term, tree mortality due to both top kill by fire and toppling by large herbivores may reduce overall microhabitat availability, eliminating the synergy.