Spatio-temporal Segregation Research Articles

Plant traits and seasonality shape coexistence and niche segregation patterns among spider species.

Understanding the mechanisms that enable species coexistence is a central question in ecology, as it helps to comprehend species diversity. One of the most common stabilizing mechanisms of coexistence is niche segregation, which can prevent the competitive exclusion of the fittest competitor. Niche segregation can manifest itself at various temporal and spatial scales, allowing provide essential insights into understanding the stabilizing mechanisms facilitating the coexistence of species. We assessed coexistence patterns among flower-dwelling spiders in two ways, in the first set of analyses, we investigated the factors influencing the quantity of spider individuals and species. The second approach we investigate the spatio-temporal segregation between species, effectively examining the coexistence patterns. We observed that the presence of inflorescences per plant, the number of flowers per inflorescence, and the presence of EFNs play a significant role in increasing spider abundance and richness. We find only a marginal seasonal effect, suggesting that spiders have constant access to resources throughout the year. Our niche overlap analysis demonstrated synchrony in the spatial occupation of niches by different spider species. The coexistence patterns appeared to be unaffected by the number of inflorescences. The greater number of inflorescences will enable a greater availability of niches, and consequently more abundance and richness of species of spiders the plant can sustain. Our results suggest that, to mitigate the adverse consequences of competitive interactions, spiders tend to adopt spatial partitioning as a strategy to facilitate the coexistence of spiders living in reproductive structures on plants in the Brazilian savanna.

Retinoic acid, an essential component of the roof plate organizer, promotes the spatiotemporal segregation of dorsal neural fates.

Dorsal neural tube-derived retinoic acid promotes the end of neural crest production and transition into a definitive roof plate. Here, we analyze how this impacts the segregation of central and peripheral lineages, a process essential for tissue patterning and function. Localized in ovo inhibition in quail embryos of retinoic acid activity followed by single-cell transcriptomics unraveled a comprehensive list of differentially expressed genes relevant to these processes. Importantly, progenitors co-expressed neural crest, roof plate and dI1 interneuron markers, indicating a failure in proper lineage segregation. Furthermore, separation between roof plate and dI1 interneurons is mediated by Notch activity downstream of retinoic acid, highlighting their crucial role in establishing the roof plate-dI1 boundary. Within the peripheral branch, where absence of retinoic acid resulted in neural crest production and emigration extending into the roof plate stage, sensory progenitors failed to separate from melanocytes, leading to formation of a common glia-melanocyte cell with aberrant migratory patterns. In summary, the implementation of single-cell RNA sequencing facilitated the discovery and characterization of a molecular mechanism responsible for the segregation of dorsal neural fates during development.

Spatio-temporal segregation: commuting time that unite and separate classes and races

Resumo É marcante o intenso crescimento das cidades brasileiras caracterizado pela periferização e pelas desigualdades socioespaciais. Porém, ainda são escassas pesquisas que enfoquem a dimensão temporal quanto à compreensão da segregação espacial. Este artigo visa compreender o papel do tempo de deslocamento na explicação do processo de segregação espacial na metrópole de São Paulo. Para tanto, sua metodologia baseia-se em dados estatísticos das áreas de ponderação da amostra do Censo Demográfico, através da variável tempo de deslocamento habitual para o trabalho, combinada com outras variáveis socioeconômicas, de renda e raça. Busca-se contribuir para o entendimento da segregação espaço-temporal, demonstrando que o tempo de deslocamento une os mais pobres e os negros, separando-os dos mais ricos e dos brancos na referida metrópole.

Segregação espaço-temporal: tempo de deslocamento que une e separa classes e raças

Abstract The intense growth of Brazilian cities is remarkable, characterized by peripheralization and socio-spatial inequalities. However, studies that focus on the temporal dimension to understand spatial segregation are still scarce. This paper aims to understand the role played by commuting time in explaining the process of spatial segregation in the São Paulo metropolis. Its methodology is based on statistical data obtained from the weighting areas of the Demographic Census sample, by means of the variable usual commuting time, combined with other socioeconomic variables of income and race. This research contributes to the understanding of spatio-temporal segregation and shows that commuting time unites the poorest and black individuals, separating them from the richest and white individuals in the São Paulo metropolis.

Fine-scale niche differences allow the co-existence of congeneric aquatic beetles in supratidal rockpools

Here we focused on the co-occurrence pattern on regional and local scales, and on the niche differences of two species of congeneric beetles (Ochthebius quadricollis and O. lejolisii, Hydraenidae) exclusive of supratidal rockpools. Abundances of adults and larval stages from both species and environmental variables were obtained in 10 pools from 12 localities along the Iberian Mediterranean coast. To determine the local co-existence pattern, we monthly sampled two localities in an annual cycle. On regional and local scales, we found negative correlations between both species’ pool abundances, which suggest spatio-temporal segregation based on their different environmental responses. The OMI analysis detected interspecific niche differences, larger in larvae than adults. The best regression models obtained for O. quadricollis larvae included depth, conductivity, and fine sediments as the main explanatory variables with a positive effect, and distance to sea and CPOM with a negative effect. For O. lejolisii larvae, the best models included CPOM and periphyton with positive effects, while pool area, depth and conductivity negatively affected. Our results suggest that subtle interspecific differences in ecological niches, mainly those related to pool hydroperiod and salinity, could determine spatio-temporal storage effects as the principal mechanisms of co-existence on local and regional scales.

Understanding carnivore interactions in a cold arid trans-Himalayan landscape: What drives co-existence patterns within predator guild along varying resource gradients?

Predators compete for resources aggressively, forming trophic hierarchies that shape the structure of an ecosystem. Competitive interactions between species are modified in the human-altered environment and become particularly important where an introduced predator can have negative effects on native predator and prey species. The trans-Himalayan region of northern India has seen significant development in tourism and associated infrastructure over the last two decades, resulting in many changes to the natural setting of the landscape. While tourism, combined with unmanaged garbage can facilitate red fox (Vulpes vulpes), it also allows free-ranging dogs (Canis lupus familiaris), an introduced mesopredator to thrive, possibly more than the native red fox. We look at the little-known competitive dynamics of these two meso-carnivores, as well as their intra-guild interactions with the region's top carnivores, the snow leopard (Panthera uncia) and the Himalayan wolf (Canis lupus chanco). To study interactions between these four carnivores, we performed multispecies occupancy modeling and analyzed spatiotemporal interactions between these predators using camera trap data. We also collected scat samples to calculate dietary niche overlaps and determine the extent of competition for food resources between these carnivores. The study found that, after controlling for habitat and prey covariates, red fox site use was related positively to snow leopard site use, but negatively to dog and wolf site use. In addition, site use of the dog was associated negatively with top predators, that is, snow leopard and Himalayan wolf, while top predators themselves related negatively in their site use. As anthropogenic impacts increase, we find that these predators coexist in this resource-scarce landscape through dietary or spatiotemporal segregation, implying competition for limited resources. Our research adds to the scant ecological knowledge of the predators in the region and improves our understanding of community dynamics in human-altered ecosystems.

Spatiotemporal segregation by migratory phenotype indicates potential for assortative mating in lake sturgeon

Migratory diversity can promote population differentiation if sympatric phenotypes become temporally, spatially, or behaviorally segregated during breeding. In this study, the potential for spatiotemporal segregation was tested among three migratory phenotypes of lake sturgeon (Acipenser fulvescens) that spawn in the St. Clair River of North America's Laurentian Great Lakes but differ in how often they migrate into the river and in which direction they move after spawning. Acoustic telemetry over 9 years monitored use of two major spawning sites by lake sturgeon that moved north to overwinter in Lake Huron or south to overwinter in Lake St. Clair. Lake St. Clair migrants were further distinguished by whether they migrated into the St. Clair River each year (annual migrants) or intermittently (intermittent migrants). Social network analyses indicated lake sturgeon generally co-occurred with individuals of the same migratory phenotype more often than with different migratory phenotypes. A direct test for differences in space use revealed one site was almost exclusively visited by Lake St. Clair migrants whereas the other site was visited by Lake Huron migrants, intermittent Lake St. Clair migrants, and, to a lesser extent, annual Lake St. Clair migrants. Analysis of arrival and departure dates indicated opportunity for co-occurrence at the site visited by all phenotypes but showed Lake Huron migrants arrived approximately 2 weeks before Lake St. Clair migrants. Taken together, our results indicated partial spatiotemporal segregation of migratory phenotypes that may generate assortative mating and promote population differentiation.

Intra-specific variation in responses to habitat restoration: Could artificial reefs increase spatiotemporal segregation between migratory phenotypes of lake sturgeon?

Habitat restoration is an important tool used to conserve biodiversity and restore species, but its effects are notoriously difficult to predict. Although outcomes of restoration projects are usually assessed using indices of species abundance and diversity, phenotypic differences among individuals within species are likely associated with differing responses to restored habitats. Here, we use lake sturgeon (Acipenser fulvescens) as a case study to illustrate how responses to habitat restoration can differ between phenotypes and potentially lead to unanticipated effects on populations. North America’s St. Clair River supports one of the largest remaining populations of lake sturgeon but has lost much spawning habitat due to its role as a major industrial corridor between the Laurentian Great Lakes Erie and Huron. Two artificial reefs were recently built in the lower and middle segments of the river to increase the available sturgeon spawning habitat. Interestingly, lake sturgeon in the St. Clair River express different migratory phenotypes that may be associated with different likelihoods of colonizing artificial reefs. Acoustic telemetry revealed that artificial reefs were more likely to be used by sturgeon that migrated downstream to overwinter in Lake St. Clair than those that migrated upstream to overwinter in Lake Huron. Furthermore, increasing time spent at the artificial reefs by Lake St. Clair migrants was associated with later arrival to and shorter occupancy of the river’s only natural spawning site, the primary location where the two phenotypes have opportunity to interbreed. Additional research is necessary to determine the ultimate impacts of the artificial reefs on lake sturgeon populations; nevertheless, our study showed phenotype-specific opportunity to colonize restored habitat and a mechanism through which this could lead to changes in gene flow. Our results illustrate the importance of considering intra-specific diversity when planning restoration projects and assessing the effects on populations.

Spatio-temporal patterns of co-occurrence of tigers and leopards within a protected area in central India

Abstract. The global decline of large carnivore populations warrants scientific insights into intraguild relationships. Patterns of co-occurrence among sympatric predators are governed by their density, distribution, diet, activity overlaps, and behavioural strategies. Tigers are sympatric with leopards across their distribution range, overlap substantially in their diet, and are both nocturnal. The subdominant leopard is believed to coexist with tigers via several mechanisms like spatial segregation, temporal avoidance, and differential prey selection. Investigation of spatio-temporal patterns of co-occurrence of tigers and leopards can provide insights on mechanisms that permit coexistence. We used camera trap-based photo captures of tigers and leopards in prey-rich (58.15±10.61 ungulates per km2) Pench Tiger Reserve to determine their spatio-temporal patterns of co-occurrence. Spatially explicit density estimates of tigers were approximately 5 per 100 km2 and leopards were approximately 4.5 per 100 km2 and remained stable over the years. This implies that both these co-predators are likely to attain carrying capacity within the study area. Areas with high tiger density had lower leopard density. Quantile regression analysis between tiger and leopard density at 2×2 km grid showed that leopard density had a parabolic relationship with tiger density, initially increasing with tigers (β=0.393; p=0.001), stable at medium tiger density (β=0.13 and p=0.15), and declining at high tiger densities (β=-0.37 and p<0.001). Both tigers and leopards were crepuscular in nature with no temporal segregation (Δ=89 %). Time lag of consecutive leopard photograph after a tiger capture ranged between 0.002 to 36.29 d. Leopard use of trails was not related to use by tigers. Our results suggest that leopards adjust their usage of space at fine scales to avoid confrontations with tigers. We also observed high temporal overlap and no spatio-temporal segregation between tigers and leopards, despite the two predators being nocturnal and having similar prey choices. The availability of ample prey within the study area is likely to be the driving factor of the co-occurrence of tigers and leopards within this dry deciduous habitat of central India.

Linking spatial and temporal contexts to multi-contextual segregation by hukou status in urban China

The paradigm in segregation research is shifting from a place-based to a people-based perspective and from static spatial segregation to dynamic spatiotemporal segregation. However, empirical studies measuring individual-level segregation from a space–time nexus perspective are quite limited, and the effects of various geographic and temporal contexts in people's daily lives on segregation are not clear enough. Drawing on activity-travel diary data in Shanghai, China, we considered hukou (“household registration”) status as the key dimension in this research. Accordingly, we employed an individual-level spatiotemporal proximity index (i-STP index) to measure multi-contextual segregation and then examined the associations between various spatial and temporal contexts with regard to hukou segregation. In this study, we found that migrant and rural populations experience higher levels of segregation, not only in residential neighborhood or activity spaces, but also in various space–time contexts in their daily lives. Moreover, it reveals temporal variations in hukou segregation, which is correlated with the arrangement of daily activities and the temporal rhythm of the city. Our study also shows the various roles of geographical contexts within residential spaces and activity spaces that are segregated, indicating that improved facilities within activity spaces could help mitigate hukou segregation. Therefore, it contributes to the current literature with people-based dynamic measurements of hukou segregation and offers insight regarding the understanding of the relationship between spatial and temporal contexts as well as activity attributes with multi-contextual segregation.

Wild Felid Diversity, Space Use and Activity Patterns in the Eastern Himalaya, India

Species with similar resource requirements cannot coexist for long. To facilitate co-existence, carnivores adapt different strategies to partition the available resources in space and time. In high-altitude ecosystems with limited resources the operation becomes complex. We assessed species diversity and spatio-temporal resource partitioning among felid species inhabiting the intricate habitats of Khangchendzonga Biosphere Reserve (KBR), Eastern Himalaya. We used systematic camera trap surveys along with abundance and overlap indices to generate information on their space use and activity patterns. We recorded six species of felids belonging to five genera, including four species of global conservation importance. The differential use of space by felids was observed with respect to the habitat types determined by sharp altitudinal gradients with varied levels of spatial and altitudinal overlap. Maximum overlap was observed among Asiatic golden cat Catopuma temminckii, jungle cat Felis chaus and clouded leopard Neofelis nebulosa. The felids had distinct activity profiles from one other, particularly between golden cat and leopard cat Prionailurus bengalensis. Pianka’s index also provided weak evidence for temporal overlap among species. The overall results indicate that habitat heterogeneity facilitates primary separation at the spatial scale, although species are also segregated temporally. Golden cat was the most adaptive felid in the area, depicting a peculiar pattern of spatio-temporal segregation with other species. We suspect either intense competition or dietary segregation among some species, and propose a further investigation of their diet and the activity patterns of their prey. The study presents an early template of carnivore community organization in resource-scarce high-altitude environments, thus, offering huge ecological and conservation significance.

Distribution of squid paralarvae and related oceanographic features in the eastern Campeche Bank, Mexico

AbstractThe eastern Campeche Bank is a region where the composition, distribution and abundance of one of its most promising resources, the teuthid cephalopods (squids), need to be better documented, particularly at the paralarval stage. To contribute to its knowledge, we obtained paralarvae from zooplankton samples collected from May 2016 to November 2017, relating and modeling their distribution to sea surface temperature, salinity, dissolved oxygen (DO), chlorophyll-a (Chl-a), zooplankton biomass and depth. The results showed that most paralarvae measured <2.0 mm mantle length. Higher abundances were found during upwelling months. Spatiotemporal segregation of teuthid species was observed, with oceanic paralarvae occurring offshore in May–July, and neritic ones appearing nearshore in September–November, Abralia redfieldi and Doryteuthis plei being the most abundant. Statistical generalized additive model for location, scale and shape showed that A. redfieldi was present in the north (offshore), related to warm Caribbean waters, and increased Chl-a and DO concentration. In contrast, D. plei was present in the south (nearshore), related to Yucatan shelf waters and low Chl-a.

Spatiotemporal segregation of chiral supramolecular polymers

•Chirality switching in out-of-equilibrium supramolecular systems •Spatiotemporally controlled formation of chirally assorted supramolecular polymers •Audible sound-assisted segregation of chiral and achiral supramolecular polymers •Audible sound-assisted segregation of supramolecular polymers of opposite helicity Programmable spatiotemporal control over the formation of functional supramolecular polymers, which leads to the formation of different morphological forms in solution, is one of the long-standing issues in chemistry. The situation is even more complex especially when dealing with a mixture of species in multicomponent self-assemblies. One way to achieve this goal is by controlling the spatiotemporal distribution of the molecular components in solution, which control the overall aggregation process. Herein, we report the spatiotemporal segregation of different redox-responsive supramolecular assemblies inside spatiotemporal domains generated within the same solution under out-of-equilibrium conditions by using audible sound. Using this approach, we can spatiotemporally control the formation of at least two types of assemblies, which are either both achiral or one of them is chiral, or both are chiral but with opposite helicity. This strategy may provide advanced control over solution-state synthesis of supramolecular polymers, which exhibit morphology-dependent functions. Programmable spatiotemporal control over the formation of functional supramolecular polymers, which leads to the formation of different morphological forms in solution, is one of the long-standing issues in chemistry. The situation is even more complex especially when dealing with a mixture of species in multicomponent self-assemblies. One way to achieve this goal is by controlling the spatiotemporal distribution of the molecular components in solution, which control the overall aggregation process. Herein, we report the spatiotemporal segregation of different redox-responsive supramolecular assemblies inside spatiotemporal domains generated within the same solution under out-of-equilibrium conditions by using audible sound. Using this approach, we can spatiotemporally control the formation of at least two types of assemblies, which are either both achiral or one of them is chiral, or both are chiral but with opposite helicity. This strategy may provide advanced control over solution-state synthesis of supramolecular polymers, which exhibit morphology-dependent functions.

Reovirus uses temporospatial compartmentalization to orchestrate core versus outercapsid assembly.

Reoviridae virus family members, such as mammalian orthoreovirus (reovirus), encounter a unique challenge during replication. To hide the dsRNA from host recognition, the genome remains encapsidated in transcriptionally active proteinaceous core capsids that transcribe and release +RNA. De novo +RNAs and core proteins must repeatedly assemble into new progeny cores in order to logarithmically amplify replication. Reoviruses also produce outercapsid (OC) proteins μ1, σ3 and σ1 that assemble onto cores to create highly stable infectious full virions. Current models of reovirus replication position amplification of transcriptionally-active cores and assembly of infectious virions in shared factories, but we hypothesized that since assembly of OC proteins would halt core amplification, OC assembly is somehow regulated. Kinetic analysis of virus +RNA production, core versus OC protein expression, and core particles versus whole virus particle accumulation, indicated that assembly of OC proteins onto core particles was temporally delayed. All viral RNAs and proteins were made simultaneously, eliminating the possibility that delayed OC RNAs or proteins account for delayed OC assembly. High resolution fluorescence and electron microscopy revealed that core amplification occurred early during infection at peripheral core-only factories, while all OC proteins associated with lipid droplets (LDs) that coalesced near the nucleus in a μ1–dependent manner. Core-only factories transitioned towards the nucleus despite cycloheximide-mediated halting of new protein expression, while new core-only factories developed in the periphery. As infection progressed, OC assembly occurred at LD-and nuclear-proximal factories. Silencing of OC μ1 expression with siRNAs led to large factories that remained further from the nucleus, implicating μ1 in the transition to perinuclear factories. Moreover, late during infection, +RNA pools largely contributed to the production of de-novo viral proteins and fully-assembled infectious viruses. Altogether the results suggest an advanced model of reovirus replication with spatiotemporal segregation of core amplification, OC complexes and fully assembled virions.

An extended spatiotemporal exposure index for urban racial segregation

ABSTRACT The Segregation Index quantifies the degree of segregation of social groups or classes. Because of the increasing use of fine-grained spatiotemporal activity and flow data, the conventional segregation measurements’ inclusiveness is challenged. We add population flow to the conventional place-based spatial exposure index to identify spatiotemporal segregation changes. Specifically, we considered the population-flow network, hierarchical structure, and time. In Chicago’s demonstration case study, we first used the time-dependent Twitter Origin-Destination flow matrices and their hierarchical structure information to estimate interactions between areal units at the neighborhood level. Then we computed the new population composition of units based on their interactions with other units and estimated the proposed spatiotemporal exposure index for different times. Finally, we systematically compared their differences with the conventional indices at global and local scales to see how population-flow patterns affect the exposure index. The results show that the population-flow patterns reflect valuable information in neighborhood interactions in temporal and spatial dimensions, but it is missing information in the conventional segregation computations. Furthermore, we emphasize that the hierarchical structures of flow patterns and the choice of appropriate parameters are also important factors for a rational segregation evaluation.

Spatio-temporal ecology of a carnivore community in middle atlas, NW of Morocco

In species that live in sympatry, some dimensions of their ecological niche can overlap, but coexistence is possible thanks to segregation strategies, being the differential use of space and time one of the most frequent. Through a pioneer study in North-West Africa based on a camera-trapping survey, we studied ecology features of a carnivores’ community in the Middle Atlas Mountains, Morocco. We focused on how species shared (or not) the territory and their activity patterns. Camera trapping detected five carnivorous species: African golden wolf (Canis lupaster), red fox (Vulpes vulpes), domestic dog (Canis lupus familiaris), genet (Genetta genetta) and African wildcat (Felis lybica lybica). Generalized Linear Models confirmed different habitat selection patterns between these species. The presence of a small protected area or prey availability apparently were not determinant factors in the abundance of these species. Spatial segregation patterns were observed between the red fox with the domestic dog and between the red fox with the genet. Kernel density estimates showed strong temporal segregation of red fox and African golden wolf with regard to domestic dog, and suggested avoidance mechanisms for the triad red fox, genet and African golden wolf. Despite the influence of interspecific competition in the assembly of the community, human pressure was apparently the most relevant factor related with the spatio-temporal segregation in this territory.

Maximum Likelihood Estimation of Kokanee and Sockeye Salmon Spawners in a Stream Using Visual Survey Data, 2003-2017

A Maximum Likelihood estimation procedure was developed for the joint assessment of resident kokanee and anadromous sockeye salmon in the Okanagan River, British Columbia. The model uses visual survey counts and is an extension of other areaunder- the type models used for estimation of salmon escapement. Alternative hypotheses were tried concerning observation error structure, arrival times, and survival patterns for a common observer efficiency estimate. The final model is described here, with information on setting bounds and constraints for parameter estimation, comparisons made and the results obtained. Estimates of abundance and approximate confidence intervals are comparable to those obtained from other investigations. Since 2001, Sockeye accounted from 6%-38% of the spawners, with no evidence from surveys and estimates to indicate kokanee are negatively impacted Sockeye, perhaps because of the estimated spatio-temporal segregation pattern. Recommendations are made concerning future adjustments and surveys for systems with two Nerkids that cannot always be readily distinguished in visual surveys. The results obtained are important to justify continued efforts to re-introduce Sockeye into Canada, maintain hatchery production to supplement Columbia River Sockeye fisheries, and protect existing biodiversity in this multi-species ecosystem. Management implications for the Columbia River fisheries in the US and Canada are discussed.

Estimation of spatial and temporal overlap in three ungulate species in a Mediterranean environment

Interspecific interactions are key drivers in structuring animal communities. Sympatric animals may show such behavioural patterns as the differential use of space and/or time to avoid competitive encounters. We took advantage of the ecological conditions of our study area, inhabited by different ungulate species, to investigate the spatial and temporal distribution of Capreolus capreolus, Dama dama and Sus scrofa. We estimated intraspecific interaction arising from the concomitant use of resources by using camera trapping. We collected 2741 videos with the three ungulates, which showed peculiar activity patterns. The three species were observed in all the habitat types of the study area over the four seasons, thus highlighting an evident spatial overlap. Moreover, our analysis demonstrated that the three species did not avoid each other through temporal segregation of their activities, rather showing a high overlap of daily activity rhythms, though with differences among the species and the seasons. Despite the high spatial and temporal overlap, the three species seemed to adopt segregation through fine-scale spatial avoidance: at an hourly level, the proportion of sites where the species were observed together was relatively low. This spatio-temporal segregation revealed complex and alternative behavioural strategies, which likely facilitated intra-guild sympatry among the studied species. Both temporal and spatio-temporal overlap reached the highest values in summer, when environmental conditions were more demanding. Given these results, we may presume that different drivers (e.g. temperature, human disturbance), which are likely stronger than interspecific interactions, affected activity rhythms and fine-scale spatial use of the studied species.

Passive acoustic monitoring reveals spatiotemporal segregation of two fish-eating killer whale Orcinus orca populations in proposed critical habitat

Competition for prey resources among ecologically similar populations that occur in sympatry can be reduced by spatiotemporal resource partitioning. Understanding patterns of habitat use of cetaceans can be difficult since they are highly mobile and can have large home ranges. We used passive acoustic monitoring at 15 sites along the coast of Washington State, USA, to assess habitat use patterns of 2 sympatric populations of fish-eating killer whales Orcinus orca: northern residents (NRKW) and southern residents (SRKW). This area is part of the ocean distributions of a number of important runs of Chinook salmon Oncorhyncus tshawytscha, the preferred prey of both populations, and is proposed critical habitat for SRKW. We compared monthly occurrence of both populations at recorder locations grouped by their proximity to the Strait of Juan de Fuca to the north and the Columbia River to the south in one analysis and by their distance from shore in a second analysis. NRKW and SRKW were detected throughout the year with spring and fall peaks in occurrence. The northernmost sites accounted for 93% of NRKW detections, while less than half of SRKW detections were at these sites. SRKW were most frequently detected at nearshore sites (83% of detections), while the majority of NRKW detections were at mid-shelf and deep sites (94% of detections). This study provides further information about the habitat use of these resident killer whale populations with implications for their management and conservation.

Skin δ13C and δ15N reveal spatial and temporal patterns of habitat and resource use by free-ranging odontocetes from the southwestern Atlantic Ocean

Large diversity and abundance of cetacean species occur along the Brazilian outer continental shelf and slope waters. In the present study, we analyzed carbon (δ13C) and nitrogen (δ15N) stable isotopes in skin biopsies of ten odontocete species (Delphinidae and Physeteridae) to assess the intra- and inter-specific patterns in the use of resources along the region. Our isotopic analysis allowed us to identify two potential subpopulations of Stenella frontalis. High core isotopic niche overlap between S. frontalis from the southern range of the study area and Delphinus delphis, especially in spring, suggested that they share similar resources and rely on spatiotemporal segregation to achieve niche differentiation and to minimize competition. Our isotopic data also pointed to high similarity among Tursiops truncatus, S. frontalis, and Globicephala melas in the use of resources. Steno bredanensis had the highest δ15N and δ13C, which agrees with its occurrence in neritic waters. S. longirostris showed consistently low δ15N values, indicating that they feed at relatively lower trophic levels, and lack of niche overlap with most delphinid species, except S. attenuata. Orcinus orca and G. melas had very similar δ13C and δ15N values, that were consistent with feeding in offshore waters. δ13C and δ15N in Physeter macrocephalus suggested that individuals feed on similar trophic levels, but over a wide spatial range. The analyses of stable isotopes in skin biopsies helped us to refine our knowledge about the intra-specific resource and habitat use, ecological niches, and the trophic interactions amongst co-occurring cetaceans from the oceanic waters of the subtropical western South Atlantic.