Ecological Research Articles

Social networks of solitary carnivores: The case of endangered tigers and insights on their conservation

AbstractSolitary carnivores are an ecologically important taxa and at a high risk of extinction worldwide. Interactions between conspecifics can influence fitness outcomes and may help these animals cope with environmental and anthropogenic disturbances. However, the structure and maintenance of these interactions in solitary carnivore species is underexplored. In this research, we leveraged existing camera trap data on tigers (Panthera tigris)—a globally endangered and solitary carnivore species—in Nepal's Chitwan National Park to examine for the first time their social networks over 8 years (2008–2017). These networks assume that the co‐occurrence at camera trap locations represents an association between conspecifics. We found that tiger networks were fickle, remaining stable for about 3 years before dissolving. We also found that males were more likely than females to form bridges between other tigers, and resident tigers were more central in the networks than nonresidents. In addition, interactions between two animals were more frequent if they were of the opposite sex or were both residents. These insights have implications on disease transmission, population dynamics, and human‐wildlife conflict. Combined with camera trap monitoring programs, collecting data on the conspecific interactions of solitary carnivores can advance our knowledge of animal ecology and improve conservation planning.

Deep learning enables satellite-based monitoring of large populations of terrestrial mammals across heterogeneous landscape

New satellite remote sensing and machine learning techniques offer untapped possibilities to monitor global biodiversity with unprecedented speed and precision. These efficiencies promise to reveal novel ecological insights at spatial scales which are germane to the management of populations and entire ecosystems. Here, we present a robust transferable deep learning pipeline to automatically locate and count large herds of migratory ungulates (wildebeest and zebra) in the Serengeti-Mara ecosystem using fine-resolution (38-50 cm) satellite imagery. The results achieve accurate detection of nearly 500,000 individuals across thousands of square kilometers and multiple habitat types, with an overall F1-score of 84.75% (Precision: 87.85%, Recall: 81.86%). This research demonstrates the capability of satellite remote sensing and machine learning techniques to automatically and accurately count very large populations of terrestrial mammals across a highly heterogeneous landscape. We also discuss the potential for satellite-derived species detections to advance basic understanding of animal behavior and ecology.

Stable isotopes and a changing world.

The measurement of naturally occurring stable isotope ratios of the light elements (C, N, H, O, S) in animal tissues and associated organic and inorganic fractions of associated environments holds immense potential as a means of addressing effects of global change on animals. This paper provides a brief review of studies that have used the isotope approach to evaluate changes in diet, isotopic niche, contaminant burden, reproductive and nutritional investment, invasive species and shifts in migration origin or destination with clear links to evaluating effects of global change. This field has now reached a level of maturity that is impressive but generally underappreciated and involves technical as well as statistical advances and access to freely available R-based packages. There is a need for animal ecologists and conservationists to design tissue collection networks that will best answer current and anticipated questions related to the global change and the biodiversity crisis. These developments will move the field of stable isotope ecology toward a more hypothesis driven discipline related to rapidly changing global events.

A tribute to Professor Walter Traunspurger

Summary With this tribute, we want to highlight Professor Walter Traunspurger’s achievements and contributions to education and research in the fields of nematology and ecology. Walter started to teach in 1998 in the Department of Animal Ecology at Bielefeld University (Germany) and completed his tenure in September 2022, a milestone in his career for which he deserves appreciation, although he is surely going to stay as enthusiastic and busy for many years to come. Over his 30 years of an outstanding academic career, he has supervised 22 Ph.D., 49 M.Sc. and 139 B.Sc. students. He has published over 200 research articles in leading zoological, ecological and ecotoxicological journals. Walter is one of the few living nematologists capable of identifying free-living freshwater nematodes to species level. However, his expertise and research interests are much broader with his biota-inclusive and trans-disciplinary approaches. For his students and colleagues, he has been an inexhaustible source of idealism, knowledge and lively experiences. The book, Ecology of freshwater nematodes, edited by Walter in 2021, provides a good overview of his recent research topics. Here, by summarising and sharing his main scientific accomplishments in this article, we hope that his story will inspire the next generation of nematologists and ecologists to continue his legacy and explore the promising avenues of research that he opened up during his productive scientific career.

Virtual prey with Lévy motion are preferentially attacked by predatory fish.

Of widespread interest in animal behavior and ecology is how animals search their environment for resources, and whether these search strategies are optimal. However, movement also affects predation risk through effects on encounter rates, the conspicuousness of prey, and the success of attacks. Here, we use predatory fish attacking a simulation of virtual prey to test whether predation risk is associated with movement behavior. Despite often being demonstrated to be a more efficient strategy for finding resources such as food, we find that prey displaying Lévy motion are twice as likely to be targeted by predators than prey utilizing Brownian motion. This can be explained by the predators, at the moment of the attack, preferentially targeting prey that were moving with straighter trajectories rather than prey that were turning more. Our results emphasize that costs of predation risk need to be considered alongside the foraging benefits when comparing different movement strategies.

What's hot and why?

What's hot and why?

Integrating spaceborne estimates of structural diversity of habitat into wildlife occupancy models

Vegetation structure is a crucial dimension of wildlife habitat, responsive to global changes in human activities and ecosystem processes. NASA’s recent Global Ecosystem Dynamics Investigation (GEDI) provides an exciting opportunity to explore how spaceborne waveform observations can improve our ability to measure wildlife habitat and advance animal ecology in the Anthropocene. We tested the utility of GEDI data in univariate occupancy models to estimate habitat use in a remote mountain system in central Idaho, USA. We collected data from 49 camera trap stations from two surveys in 2018–2019 and modeled the occupancy for each of seven mammal species representing different trophic levels and feeding strategies: American black bear (Ursus americanus), deer (Odocoileus hemionus), elk (Cervus canadensis), moose (Alces alces), coyote (Canis latrans), wolf (Canis lupus), and mountain lion (Puma concolor). We first derived structural diversity indices (richness, evenness, and divergence) of GEDI-derived canopy height, plant area index, and foliage height diversity to represent different dimensions of vegetation structure. This spatial aggregation is necessary due to gaps in GEDI footprints and parallels commonly used functional diversity metrics applied to biological communities that are calculated using trait probability densities. We measured these indices across three spatial scales that reflect different species movement and habitat selection patterns. We found the structural diversity indices of canopy height, foliage height diversity, and plant area index had the strongest effects on the occupancy of most mammals compared to two-dimensional (2D) variables (e.g. tree cover, normalized difference vegetation index). The spatial extent of these indices also influenced the strength of response, highlighting the importance of selecting a scale large enough to capture sufficient GEDI footprints but small enough to reflect site-level variance. Compared to 2D covariates, our results suggest that GEDI variables allow researchers to generate more detailed inference on the forms of habitat that wildlife use. We discuss the implications of these findings for habitat management and future wildlife research from local to global scales.

Sex-specific seasonal variations of wild boar distance traveled and home range size.

Distance traveled and home range size describe how animals move in space. The seasonal variations of these parameters are important to comprehensively understand animal ecology and its connection with reproductive behavior and energy costs. Researchers usually estimate the distance traveled as the sum of the straight-line displacements between sampled positions, but this approach is sensitive to the sampling frequency and does not account for the tortuosity of the animal's movements. By means of the continuous-time movement modeling which takes into account autocorrelation and tortuosity of movement data, we estimated the distance traveled and monthly home range size of 28 wild boar Sus scrofa and modeled their inter-sexual seasonal variability. Males traveled longer distances and used larger home ranges than females, particularly during the rut in autumn-winter, consistently with the different biological cycles of males and females. Males enlarged their home ranges during the rut but traveled constant average distances along the year, whereas females traveled shorter distances in correspondence with the peak of food resources and birth periods but exhibited constant home range size across seasons. The differences between the seasonal variation patterns of distance traveled and home range size, observed in both sexes, revealed the complex relationship between these two aspects of spatial behavior and the great opportunity of including both distance traveled and home range size in behavioral ecology investigations. We provided a detailed analysis of wild boar spatial behavior and its relationships with the reproductive cycles of males and females, promoting a deeper comprehension of their behavioral ecology.

Comparative Genomic Insights into Bacterial Induction of Larval Settlement and Metamorphosis in the Upside-Down Jellyfish Cassiopea.

Bacteria are important mediators of the larval transition from pelagic to benthic environments for marine organisms. Bacteria can therefore dictate species distribution and success of an individual. Despite the importance of marine bacteria to animal ecology, the identity of inductive microbes for many invertebrates are unknown. Here, we report the first successful isolation of bacteria from natural substrates capable of inducing settlement and metamorphosis of the planula larvae stage of a true jellyfish, the upside-down jellyfish Cassiopea xamachana. Inductive bacteria belonged to multiple phyla, with various capacity to induce settlement and metamorphosis. The most inductive isolates belonged to the genus Pseudoalteromonas, a marine bacterium known to induce the pelago-benthic transition in other marine invertebrates. In sequencing the genome of the isolated Pseudoalteromonas and a semiinductive Vibrio, we found biosynthetic pathways previously implicated in larval settlement were absent in Cassiopea inducing taxa. We instead identified other candidate biosynthetic gene clusters involved in larval metamorphosis. These findings could provide hints to the ecological success of C. xamachana compared to sympatric congeneric species within mangrove environments and provide avenues to investigate the evolution of animal-microbe interactions. IMPORTANCE The pelagic to benthic transition for the larvae of many marine invertebrate species are thought to be triggered by microbial cues. The microbial species and exact cue that initiates this transition remains unknown for many animals. Here, we identify two bacterial species, a Pseudoalteromonas and a Vibrio, isolated from natural substrate that induce settlement and metamorphosis of the upside-down jellyfish Cassiopea xamachana. Genomic sequencing revealed both isolates lacked genes known to induce the life history transition in other marine invertebrates. Instead, we identified other gene clusters that may be important for jellyfish settlement and metamorphosis. This study is the first step to identifying the bacterial cue for C. xamachana, an ecologically important species to coastal ecosystems and an emerging model system. Understanding the bacterial cues provides insight into marine invertebrate ecology and evolution of animal-microbe interactions.

Broad‐scale genetic monitoring suggests density‐dependent dispersal in a large carnivore

Characterizing patterns and drivers of dispersal is fundamental to our understanding of animal ecology and ultimately informing species conservation and management strategies. In this study, we used microsatellite data from 3941 individual black bears Ursus americanus occupying 73 spatially distinct sampling areas across a large heterogeneous landscape to characterize dispersal via gene flow directionality. We fit spatial models to quantified gene flow to test hypotheses regarding drivers of putative dispersal patterns. Specifically, we tested the relative influence of food productivity gradients, bear density, and bear harvest on dispersal. We also evaluated differences in gene flow patterns within and between sexes to assess sex‐biased dispersal. We found evidence suggestive of positive density‐dependent, male‐biased dispersal. Our data show evidence of a relationship between dispersal and broad food productivity gradients. Specifically, male bears displayed preferential dispersal towards mixed deciduous forests with higher food productivity relative to less productive boreal forests. Given the dense sampling scheme across a continuous population, occupying a large heterogeneous landscape, these results provide key insight as to the likely drivers of dispersal patterns in a wide‐ranging mammal.

Ecology of soil animals (Diplopoda class, Myriapoda group)

Class Шplays an important role in natural ecosystems, because it supports biodiversity and soil stability, and a change in the number or distribution of centipede species can indicate changes in the environment, such as pollution, soil degradation, climate change, etc. The purpose of the study is to identify the existing species of soil animals of the Diplopoda class, as well as to determine environmental factors that can affect their distribution. Species’ diversity was assessed by collecting individuals and classifying them into order, family, genus, and species. Climatic factors, namely temperature and precipitation, are also determined. As a result of the study, ecological aspects of centipede development were evaluated and their distribution and dependence on environmental factors, such as climatic, edaphic, and trophic factors, were analysed. In the southern region of Albania, 22 species of the Diplopoda class of the Myriapoda group were identified, among which mainly decomposers of organic remains and phytophages. The regions of Llogara and Šhašhica were noted as the regions with the highest diversity of millipedes. In addition, it was established that the variation of species is influenced by the environment, the presence of organic substances, and climatic factors. Temperature and humidity are determining factors influencing the distribution of the Diplopoda class in different biotopes. Species that have a large regional distribution and are most widespread in time throughout the year: Pachyiulus cattarensis, found in the period June-November, Glomeris pulchra – May-July, SeptemberOctober, Pachyiulus varius – May-October. A less active period was noted for the following species: Polydesmus complanatus, Glomeris latermarginata, Typhloiulus albanichus, Pachyiulus hungaricus, Glomeris pustullata. The research, which was carried out, is of practical importance for nature conservation, as the Diplopoda class plays an important role in maintaining ecosystems and biodiversity and can be an indicator of the state of the environment

Let sleeping logs lie: Beta diversity increases in deadwood beetle communities over time.

Research Highlight: Seibold, S., Weisser, W., Ambarli, D., Gossner, M. M., Mori, A., Cadotte, M., Hagge, J., Bässler, C. & Thorn, S. (2022). Drivers of community assembly change during succession in wood-decomposing beetle communities. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13843. Paradigms of succession and its drivers have largely developed from systems relying on living plants. A substantial portion of terrestrial biodiversity and biomass exists in detrital systems that rely on dead organic matter, yet successional patterns in detrital systems have received far less attention. In particular, deadwood significantly contributes to forest ecosystem nutrient cycling and storage and represents a relatively long-lived detrital system in which to study patterns of succession. Seibold et al. examined successional patterns of deadwood beetle communities over 8 years in a large-scale experiment that included 379 logs from 13 different tree species in 30 forest stands in three regions of Germany. They predicted that deadwood beetle communities would initially differ among deadwood tree species, across space, and with climatic differences but would become more similar over time as deadwood decomposed and characteristics of remaining habitat become more homogeneous. However, Seibold et al. predicted that beetle communities would become increasingly different across space along deadwood succession if late successional species were weaker dispersers than early successional species. Surprisingly, beetle communities became more dissimilar over time contrary to predictions. But, as predicted, increasing phylogenetic distance among tree species led to increasingly dissimilar deadwood beetle communities. Lastly, differences across space, forest structure and climate led to different deadwood beetle communities, but these effects remained constant over time. These results suggest that deadwood succession is influenced by both deterministic and stochastic processes and that stochastic processes may be increasingly important in late successional stages. Seibold et al. reveal important drivers of detrital successional patterns in deadwood that indicate that deadwood beetle biodiversity can be promoted via maintaining a diversity of deadwood decay stages across a large phylogenetic diversity of trees species and structurally diverse forests. Future studies that test the mechanisms driving these patterns and whether these results hold for other saproxylic organisms will help inform forest conservation and management strategies.

Coming of age in your local mating market: Just a numbers game?

Research Highlight: Woodman, J. P., Cole, E. F., Firth, J. A., Perrins, C. M., & Sheldon, B. C. (2022). Disentangling the causes of age-assortative mating in bird populations with contrasting life-history strategies. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13851. In their study of age-assortative mating, Woodman and colleagues thoroughly and concisely detail its behavioural determinants using datasets, astonishing in themselves, amassed from their decades-long studies of mute swans (Cygnus olor) and great tits (Parus major), species that are respectively longer- and shorter-lived and occupying different segments of the slow/fast life-history continuum. Here, they show that positive age-assortative mating occurs through active, age-based mate selection in mute swans which play the long game, whereas in the shorter-lived great tit this is principally a passive byproduct of demographic processes. That great tits have relatively lower interannual survivorship means that newly recruited, young birds occupy a larger proportion of the breeding population in any given year than occurs in mute swans. The adaptive significance of age-assortative mating is yet to be determined, but the current study provides an exciting possibility for the role of selection on assortative mating generally in either promoting or constraining active mate selection and sexual dimorphism within and across the tree of life.

Robust rhythm reporting will advance ecological and evolutionary research

Abstract Rhythmicity in the millisecond to second range is a fundamental building block of communication and coordinated movement. But how widespread are rhythmic capacities across species, and how did they evolve under different environmental pressures? Comparative research is necessary to answer these questions but has been hindered by limited crosstalk and comparability among results from different study species. Most acoustics studies do not explicitly focus on characterising or quantifying rhythm, but many are just a few scrapes away from contributing to and advancing the field of comparative rhythm research. Here, we present an eight‐level rhythm reporting framework which details actionable steps researchers can take to report rhythm‐relevant metrics. Levels fall into two categories: metric reporting and data sharing. Metric reporting levels include defining rhythm‐relevant metrics, providing point estimates of temporal interval variability, reporting interval distributions, and conducting rhythm analyses. Data sharing levels are: sharing audio recordings, sharing interval durations, sharing sound element start and end times, and sharing audio recordings with sound element start/end times. Using sounds recorded from a sperm whale as a case study, we demonstrate how each reporting framework level can be implemented on real data. We also highlight existing best practice examples from recent research spanning multiple species. We clearly detail how engagement with our framework can be tailored case‐by‐case based on how much time and effort researchers are willing to contribute. Finally, we illustrate how reporting at any of the suggested levels will help advance comparative rhythm research. This framework will actively facilitate a comparative approach to acoustic rhythms while also promoting cooperation and data sustainability. By quantifying and reporting rhythm metrics more consistently and broadly, new avenues of inquiry and several long‐standing, big picture research questions become more tractable. These lines of research can inform not only about the behavioural ecology of animals but also about the evolution of rhythm‐relevant phenomena and the behavioural neuroscience of rhythm production and perception. Rhythm is clearly an emergent feature of life; adopting our framework, researchers from different fields and with different study species can help understand why.

Physiological Characterization of the Coral Holobiont Using a New Micro-Respirometry Tool

Metabolic activity, defined as the sum of organismal processes that involve energy, is of critical importance in understanding the function and evolution of life on earth. Measuring organismal metabolic rates is, therefore, at the center of explaining the physiological states of organisms, their ecological roles, and the impact of environmental change on species within terrestrial and aquatic ecosystems. On coral reefs, measures of metabolism have been used to quantify symbiosis functioning between corals and their obligate algal symbionts (Symbiodiniaceae), as well as assess how environmental stressors, including climate change, will impact coral health. Despite this significance, there is a lack of methods, and therefore data, relating to metabolic rate measurements in coral offspring, likely due to their small size. To address this gap, this study aimed to develop a custom setup for measuring the respiration of small (millimeter size range) marine animal ecologies. This low cost and easy setup should allow for the improved measurement of metabolic rate. This will be essential for applied ecological research utilizing the sexual production of corals for reef restoration.

Editorial: Spatial aspects of urban animal ecology and conservation biology

Editorial: Spatial aspects of urban animal ecology and conservation biology

The distribution of vertebrate roadkill varies by season, surrounding environment, and animal class

Due to rapid human expansion in the last century, wildlife roadkill is becoming a concerning threat to biodiversity and human safety. The frequency of roadkill events depends on factors related to specific traits of the road—tortuosity or the presence of fences, among others—and the animal ecology—such as activity patterns, reproductive season, or thermoregulation. These, in turn, are related to environmental factors, with seasonal variations. Here, we assessed roadkill mortality of terrestrial vertebrates over the year. To do this, we sampled 10 road sections (of 3 km, by walk) in the south of Spain for a full year, registering the carcasses of run-over vertebrates. Then, we analysed the spatiotemporal patterns of roadkill events for the four vertebrates’ classes and the effects of road traits (presence of fence, tortuosity, distance to water point) and environmental variables (mean temperature and precipitation). Mammals suffered the highest mortality by roadkill (45.72%). The frequency of collisions was independent of tortuosity, presence of fences, and precipitation, while mean temperature significantly increased the probability of collision of mammals, birds, and reptiles. There was a seasonal effect in the number of collisions, which spatial pattern depended on the class of vertebrates. All this leads us to conclude that, to reduce the impact caused by roadkill mortality on wildlife, we need specific measures to be taken timely in each critical place and for each vertebrate group.

Bringing light onto the Raunkiæran shortfall: A comprehensive review of traits used in functional animal ecology.

Trait-based approaches elucidate the mechanisms underlying biodiversity response to, or effects on, the environment. Nevertheless, the Raunkiæran shortfall-the dearth of knowledge on species traits and their functionality-presents a challenge in the application of these approaches. We conducted a systematic review to investigate the trends and gaps in trait-based animal ecology in terms of taxonomic resolution, trait selection, ecosystem type, and geographical region. In addition, we suggest a set of crucial steps to guide trait selection and aid future research to conduct within and cross-taxon comparisons. We identified 1655 articles using virtually all animal groups published from 1999 to 2020. Studies were concentrated in vertebrates, terrestrial habitats, the Palearctic realm, and mostly investigated trophic and habitat dimensions. Additionally, they focused on response traits (79.4%) and largely ignored intraspecific variation (94.6%). Almost 36% of the data sets did not provide the rationale behind the selection of morphological traits. The main limitations of trait-based animal ecology were the use of trait averages and a rare inclusion of intraspecific variability. Nearly one-fifth of the studies based only on response traits conclude that trait diversity impacts ecosystem processes or services without justifying the connection between them or measuring them. We propose a guide for standardizing trait collection that includes the following: (i) determining the type of trait and the mechanism linking the trait to the environment, ecosystem, or the correlation between the environment, trait, and ecosystem, (ii) using a "periodic table of niches" to select the appropriate niche dimension to support a mechanistic trait selection, and (iii) selecting the relevant traits for each retained niche dimension. By addressing these gaps, trait-based animal ecology can become more predictive. This implies that future research will likely focus on collaborating to understand how environmental changes impact animals and their capacity to provide ecosystem services and goods.

Co-infections mask pathogen-specific associations with the gut microbiota in wild voles.

Research Highlight: Brila, I., Lavirinienko, A., Tukalenko, E., Kallio, E. R., Mappes, T. & Watts, P. C. (2022). Idiosyncratic effects of coinfection on the association between systemic pathogens and the gut microbiota of a wild rodent, the bank vole (Myodes glareolus). Journal of Animal Ecology, https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2656.13869. Interactions between pathogens and host-associated microbial communities can influence host fitness, disease progression and pathogen emergence. The vast majority of studies characterize interactions between single pathogens and bacterial commensals, yet co-infections with multiple pathogens are the norm in nature. In their paper on pathogen-microbiome interactions, Brila et al. (2022) examine how co-infections with four systemic pathogens associate with the gut microbiota in wild bank voles. Building on a series of tests, the authors show that excluding co-infection information from statistical models masks pathogen-specific patterns and confounds interpretations. This paper advances on previous studies by generating surveillance data on a phylogenetically diverse suite of vole pathogens to address the question as to whether pathogens exhibit unique or universal associations with gut commensals. They report that even bacterial pathogens with similar transmission ecology have divergent associations with gut microbes, and highlight that a mechanistic understanding of host-pathogen interactions is necessary for decoding the diverse consequences for gut microbial communities.

“A Delicate Equilibrium of the Most Complex Sort”

This article examines the intertidal ecological research of the commercial lab owner and popular science writer Edward F. Ricketts, best known as the prototype for John Steinbeck’s character “Doc” in the novel Cannery Row (1945). Ricketts’s friendship with Steinbeck and unconventional philosophical style have regrettably overshadowed his scientific work, particularly his novel faunal zonation surveys of the North American Pacific littoral in the 1930s and 1940s. These surveys resulted in a landmark handbook, Between Pacific Tides (1939), designed for novices and specialists alike. Ricketts’s work demonstrates how the place of ecological investigation (Billick and Price)—here Monterey Bay’s pounding surf, storm-tossed debris, eclectic bohemianism, and the collaborative energies at Hopkins Marine Station—“imprinted” West Coast animal ecology. At first, Ricketts adopted the physiological methods and conceptions of ecological holism he had learned at the University of Chicago under mentor Warder C. Allee in the early 1920s. Allee had conducted his investigations of intertidal organisms in the relatively placid bays and estuaries at the Woods Hole research center on Cape Cod, Massachusetts. Allee envisioned animal aggregations as higher-order societies guided by “unconscious cooperation” and evolving toward a climax state. Yet Ricketts found that physiochemical factors, such as temperature and salinity, could not explain the distribution of organisms amid the Pacific’s far more precarious rough-and-tumble surf, nor could they account for fierce competition among organisms. Rejecting Allee’s cooperative metaphors, Ricketts came to see community structure as an unintended result of tidepool invertebrates’ Darwinian struggle to occupy resource niches—a “set of sieves” that transferred nourishment from one part of the aggregation to the next, binding it together in interlocking food webs. Through dialogue with Steinbeck about the implications of modern physics during their Sea of Cortez voyage (1940), Ricketts developed a “unified field hypothesis” to conceptualize the dynamic interwovenness created by transfers of metabolic energy. Yet Steinbeck ultimately held fast to a super-organismic understanding of ecological holism—a hierarchical relationship between constituents and the whole that underlays the novelist’s idea of the human “phalanx” in Grapes of Wrath and other works. The article offers new insights about the ecological origins of Steinbeck and Ricketts’s disputes over “non-teleological” reasoning and the pair’s divergent understandings of nature, society, and progressive politics.