Ideal Free Distribution Research Articles

Relationships between survival and habitat suitability of semi-aquatic mammals.

Spatial distribution and habitat selection are integral to the study of animal ecology. Habitat selection may optimize the fitness of individuals. Hutchinsonian niche theory posits the fundamental niche of species would support the persistence or growth of populations. Although niche‐based species distribution models (SDMs) and habitat suitability models (HSMs) such as maximum entropy (Maxent) have demonstrated fair to excellent predictive power, few studies have linked the prediction of HSMs to demographic rates. We aimed to test the prediction of Hutchinsonian niche theory that habitat suitability (i.e., likelihood of occurrence) would be positively related to survival of American beaver (Castor canadensis), a North American semi‐aquatic, herbivorous, habitat generalist. We also tested the prediction of ideal free distribution that animal fitness, or its surrogate, is independent of habitat suitability at the equilibrium. We estimated beaver monthly survival probability using the Barker model and radio telemetry data collected in northern Alabama, United States from January 2011 to April 2012. A habitat suitability map was generated with Maxent for the entire study site using landscape variables derived from the 2011 National Land Cover Database (30‐m resolution). We found an inverse relationship between habitat suitability index and beaver survival, contradicting the predictions of niche theory and ideal free distribution. Furthermore, four landscape variables selected by American beaver did not predict survival. The beaver population on our study site has been established for 20 or more years and, subsequently, may be approaching or have reached the carrying capacity. Maxent‐predicted increases in habitat use and subsequent intraspecific competition may have reduced beaver survival. Habitat suitability‐fitness relationships may be complex and, in part, contingent upon local animal abundance. Future studies of mechanistic SDMs incorporating local abundance and demographic rates are needed.

Myopic reactivity in repeated-choice: The case of competing with others for a scarce, unevenly distributed resource.

Foraging for a scarce resource takes place when fewer resource-units than agents are distributed among several locations and agents choose at which location to look for the resource. But how do foragers distribute themselves over the different locations? Optimal foraging theory postulates that the distribution of agents should match the distribution of resource units (ideal free distribution [IFD]), but research with animals and humans has revealed undermatching at the location at which the resource is most abundant. For the IFD to be reached, full information about other foragers' choices and outcomes is required, information that is usually not available. We conducted a theoretical analysis of the implications of relying on different levels of information: on the incomplete, but still valid information usually available in foraging scenarios and on full information. The analysis demonstrates that myopic reactivity to disappointment, or to regret, which are likely to arise in the wake of incomplete information, leads to undermatching, with either affect leading to different degrees of undermatching. Importantly, these analyses indicate that behavior would be sensitive not only to resource distribution (as in IFD), but also to its overall abundance. Three experiments employing incentivized repeated choices were conducted. The information provided to participants, the number of locations, and resource abundance were manipulated to test the predictions of the models. Analyses of aggregate choice probabilities and trial-to-trial choice dynamics indicate that myopic reactivity to regret provides the best explanation for the observed data. With more information available, behavior matches more closely the IFD predictions. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Territoriality drives preemptive habitat selection in recovering wolves: Implications for carnivore conservation

According to the ideal-free distribution (IFD), individuals within a population are free to select habitats that maximize their chances of success. Assuming knowledge of habitat quality, the IFD predicts that average fitness will be approximately equal among individuals and between habitats, while density varies, implying that habitat selection will be density dependent. Populations are often assumed to follow an IFD, although this assumption is rarely tested with empirical data, and may be incorrect when territoriality indicates habitat selection tactics that deviate from the IFD (e.g. ideal-despotic distribution or ideal-preemptive distribution). When territoriality influences habitat selection, species' density will not directly reflect components of fitness such as reproductive success or survival. In such cases, assuming an IFD can lead to false conclusions about habitat quality. We tested theoretical models of density-dependent habitat selection on a species known to exhibit territorial behaviour in order to determine whether commonly applied habitat models are appropriate under these circumstances. We combined long-term radiotelemetry and census data from grey wolves Canis lupus in the Upper Peninsula of Michigan, USA to relate spatiotemporal variability in wolf density to underlying classifications of habitat within a hierarchical state-space modelling framework. We then iteratively applied isodar analysis to evaluate which distribution of habitat selection best described this recolonizing wolf population. The wolf population in our study expanded by >1,000% during our study (~50 to >600 individuals), and density-dependent habitat selection was most consistent with the ideal-preemptive distribution, as opposed to the ideal-free or ideal-despotic alternatives. Population density of terrestrial carnivores may not be positively correlated with the fitness value of their habitats, and density-dependent habitat selection patterns may help to explain complex predator-prey dynamics and cascading indirect effects. Source-sink population dynamics appear likely when species exhibit rapid growth and occupy interspersed habitats of contrasting quality. These conditions are likely and have implications for large carnivores in many systems, such as areas in North America and Europe where large predator species are currently recolonizing their former ranges.

Food Production and Domestication Produced Both Cooperative and Competitive Social Dynamics in Eastern North America

ABSTRACTRecent research emphasises the importance of both within-group cooperation and between-group competition for human sociality, past and present. We hypothesise that the shift from foraging to food production in eastern North America provided novel socioecological conditions that impacted interpersonal and intergroup interactions in the region, inspiring both greater cooperation as well as competition. We predict that (1) successful exploitation of this indigenous crop complex encouraged greater cooperation leading to site aggregation in high-quality locations as expected by an ideal free distribution with an Allee effect, and (2) continued population growth driven by the domestication and adoption of the crop complex eventually inspired a shift from positive to negative density dependent settlement dynamics, driving declines in site suitability. Our results demonstrate that there was an increase in both site clustering and site location quality coincident with crop management and domestication in the Middle Holocene, and that territorial violence appears at this time as well. Site quality later declined after c. 3000 cal BP, also as predicted. These results indicate that managing and domesticating plants inspired an Allee effect and led to greater within-group cooperation, but was also related to the rise of territorial between-group competition in the region.

What unmanaged fishing patterns reveal about optimal management: applied to the balanced harvesting debate

Abstract Balanced harvesting (BH)—the idea of harvesting all species and sizes in proportion to their production rate—has been a topic of recent debate. Developed world fisheries tend to fish more selectively, concentrating on certain species and sizes preferred in the market. However, fishing patterns in some developing countries, with a range of different fishing gears and more generalist markets, more closely resemble BH. The BH debate therefore hinges on whether selective fisheries should become more balanced, whether unselective fisheries should do the opposite, both, or neither. In this study, we use simple and general analytical theory to describe the ideal free distribution that should emerge in unmanaged fisheries, and we show that this ideal free distribution should approximately produce BH only when prices, catchabilities, and fishing costs are similar across species and sizes. We then derive general properties of yield and profit maxima subject to conservation constraints. We find that BH is unlikely to be optimal in any fishery but may be closer to optimal in fisheries in which it emerges without management. Thus, BH may be more useful as a heuristic for understanding differences between fisheries in locally appropriate management than as an exact management strategy.

Satellite-based remote sensing rapidly reveals extensive record of Holocene coastal settlement on Madagascar

Despite decades of archaeological research, roughly 75% of Madagascar's land area remains archaeologically unexplored and the oldest sites on the island are difficult to locate, as they contain the ephemeral remains of mobile hunter/forager campsites. The known archaeological record is therefore biased toward later sites, especially sites dating to the second millennium AD, following the expansion of Indian Ocean trading networks. Systematic archaeological investigations are required to address these biases in the known archaeological record and clarify the island's early human history, but funding limitations, logistical and time constraints in surveying large areas and a relatively small number of active field archaeologists present substantial barriers to expansive areal survey coverage. Using theoretical models derived from human behavioral ecology (i.e., ideal free distribution, optimal foraging theory) in conjunction with freely available remote sensing data, we illustrate how archaeological survey of Madagascar's landscapes can be rapidly expanded, more effectively target early archaeological deposits, and address questions about the island's settlement. This study illustrates the potential for theoretically-driven satellite-based remote sensing analysis to improve our understanding of the archaeological record of the world's fourth largest island.

Regional patterns of pastoralist migrations under the push of reduced precipitation in imperial China

AbstractAimAs a response of pastoralists to climate change, nomadic migration deeply shaped Chinese history during the imperial era. Existing research on climate‐driven nomadic migration is conducted mainly on a national–continental scale. To advance the current work, we aim to resolve migratory movements at a provincial–regional scale using a large and long‐term historical dataset as a first attempt. The spatio‐temporal features of nomadic migration under climatic effects, specifically precipitation, are analysed in the theoretical context of behavioural ecology.LocationChina.TimeImperial era (220 BC–1910 AD).Study subjectNomadic pastoralist minorities in imperial China.MethodsWe frame the analysis using an ideal free distribution model. A total of 1,842 historical location records of pastoralist immigration are empirically examined. Precipitation anomalies and nomadic migration are statistically assessed with nonparametric and Poisson regression methods, and temporal interdependencies among provincial–regional migratory movements are explored with a vector autoregressive model.ResultsWe divide imperial China into six regions according to statistical results and geographic factors. Overall, decreased precipitation and drought provoked pastoralist migrations in a north‐to‐south direction. Northern nomads, with an apparent preference for central China as a major destination, triggered the most conflicts with resident agriculturalists. Nomads originating from the Tibetan minority regions moved north‐eastward into Qinghai Province as their main destination.Main conclusionsLong‐term regional patterns of pastoralist migration are closely associated with drought‐induced ecological change in imperial China. Climate‐driven dynamics assessed with long‐term historical data facilitate the understanding of climate–ecology–society interactions in behavioural ecology and macroecology. Moreover, findings from imperial China may imply that cultural acceptance and communications could avoid conflicts between immigrants and original residents when facing mass migration, an issue of growing contemporary urgency in many parts of the world.

An Islandscape IFD: Using the Ideal Free Distribution to Predict Pre-Columbian Settlements from Grenada to St. Vincent, Eastern Caribbean

ABSTRACT This study employs an ideal free distribution (IFD) model to conduct a fine-grained analysis of environmental factors affecting the pre-Columbian colonisation sequence and settlement patterning in the southern Lesser Antilles of the Eastern Caribbean. We compiled a database of all known archaeological site locations and associated chronological data from St. Vincent, the Grenadines, and Grenada, and vetted this dataset for accuracy. We then performed multivariate statistical analysis of the vetted site data and 24 environmental variables hypothesised to influence settlement habitat quality, including soil attributes, proximity to freshwater/stream beds, structure and sizes of marine environments, and net primary productivity (NPP) layers. Iterative testing and refinement of the model allowed for the creation of a predictive map of pre-Columbian archaeological sites over time. Results indicate proximity to freshwater wetlands, NPP, and reef size were important variables influencing habitat choice. Additionally, latitude (distance from the equator) was also a significant variable, indicating support for a proposed colonisation of the southern Lesser Antilles that began in the northern Caribbean, rather than the south. Lastly, we provide a site inventory and map of predicted site locations that can aid in the management of threatened archaeological resources within the study region.

Dynamics of spatially dispersed population under ideal free distribution

Dynamics of spatially dispersed population under ideal free distribution

The effect of travel costs on the ideal free distribution in stickleback

AbstractThe ideal free distribution (IFD) theory, which predicts that a population of individuals will match the distribution of a patchily distributed resource, is widely used in ecology to describe the spatial distribution of animals. While many studies have shown general support of its habitat matching prediction, others have described a systematic pattern of undermatching, where too many animals feed at patches with fewer resources, and too few animals feed in richer patches. These results have been attributed to deviations from several of the assumptions of the IFD. One possible variable, the cost of travelling between patches, has received little attention. Here, we investigated the impact on resource matching when travel costs were manipulated in a simple laboratory experiment involving two continuous input patches. This experiment allowed us to control for extraneous variables and decouple time costs from energetic costs of travel. Two experiments examined the impact of varying travel costs on movement rates between foraging patches and how these travel costs impact conformity to the IFD. Our data demonstrated that there was less movement between patches and greater discrepancies from the IFD predictions as the cost of travel increased.

Nonlinear Fokker-Planck equations with reaction as gradient flows of the free energy

We interpret a class of nonlinear Fokker-Planck equations with reaction as gradient flows over the space of Radon measures equipped with the recently introduced Hellinger-Kantorovich distance. The driving entropy of the gradient flow is not assumed to be geodesically convex or semi-convex. We prove new generalized dissipation inequalities, which allow us to control the relative entropy by its production. We establish the entropic exponential convergence of the trajectories of the flow to the equilibrium. Along with other applications, this result has an ecological interpretation as a trend to the ideal free distribution for a class of fitness-driven models of population dynamics. Our existence theorem for weak solutions under mild assumptions on the nonlinearity is new even in the absence of the reaction term.

Models and measures of animal aggregation and dispersal

The dispersal of individuals within an animal population will depend upon local properties intrinsic to the environment that differentiate superior from inferior regions as well as properties of the population. Competing concerns can either draw conspecifics together in aggregation, such as collective defence against predators, or promote dispersal that minimizes local densities, for instance to reduce competition for food. In this paper we consider a range of models of non-independent movement. We include established models, such as the ideal free distribution, but also develop novel models, such as the wheel. We also develop several ways to combine different models to create a flexible model of addressing a variety of dispersal mechanisms. We further devise novel measures of movement coordination and show how to generate a population movement that achieves appropriate values of the measure specified. We find the value of these measures for each of the core models described, as well as discuss their use, and potential limitations, in discerning the underlying movement mechanisms. The movement framework that we develop is both of interest as a stand-alone process to explore movement, but also able to generate a variety of movement patterns that can be embedded into wider evolutionary models where movement is not the only consideration.

Effects of habitat complexity, dominance and personality on habitat selection: Ideal despotic cichlids

AbstractHabitat structure can impede visibility and movement, resulting in lower resource monopolization and aggression. Consequently, dominant individuals may prefer open habitats to maximize resource gain, or complex habitats to minimize predation risk. We explored the role of dominance on foraging, aggression and habitat choice using convict cichlids (Amatitlania nigrofasciata) in a two‐patch ideal free distribution experiment. Groups of six fish of four distinct sizes first competed for shrimp in one‐patch trials in both an open and complex habitat; half the groups experienced each habitat type first. Following these one‐patch trials, each group then chose between habitat types in a two‐patch trial while competing for food. Finally, each fish underwent an individual behavioural assessment using a battery of “personality” tests to determine if behaviour when alone accurately reflected behaviour within a social context. In the one‐patch trials, dominant fish showed similar food consumption between habitats, but chased more in the complex habitat. In the two‐patch choice trials, dominants preferred and defended the complex habitat, forming an ideal despotic distribution with more than half the fish and competitive weight in the open habitat. Within the groups, individual fish differed in foraging and chasing, with repeatabilities of 0.45 and 0.23 across all treatments. Although a higher foraging rate during the individual assessment predicted foraging rate and use of the complex habitat during the group trials, aggression and boldness tests were not reflective of group behaviour. Across groups, heavier dominants and those with higher foraging rate in the open habitat used the open habitat more, suggesting that both risk and energetic state affect habitat preference in dominant convict cichlids.

Does intraspecific competition among Allenby’s gerbils lead to an Ideal Free Distribution across foraging patches?

Employing the Ideal Free Distribution (IFD) principle as a tool, we investigated how Allenby’s gerbils (Gerbillus andersoni allenbyi) utilized food patches within and moved between connected quadrants (i.e., ‘habitats’) in a large outdoor semi-natural enclosure. These habitats differed in initial forager densities, but provided equal numbers of standardized food patches that provided equal rewards (i.e. food) and costs (i.e. predation risk, metabolic, and missed opportunity). We quantified the gerbils’ giving-up-densities (GUDs) within foraging patches and recorded their daily distribution between habitats. Individual gerbils were tagged with unique bar-coded numbers to compare their locations within and across habitats. The mean number of gerbil foragers (9.1 and 8.9 individuals, respectively) and GUDs evened out across habitats over time. Despite this, the distribution of gerbils did not remain static within foraging patches; instead, gerbils altered their use of patches across and within habitats on a nightly basis. This may be due to a combination of factors including, high levels of interference competition between foragers at patches, a lag effect before the gerbils perceived changes in competition intensity with the arrival and departure of individuals, and gerbils having imperfect knowledge of their environment. Furthermore, the pattern of microhabitat (open vs bush patches) use by gerbils differed over time, indicating that despite the distribution of gerbils and their GUDs evening out between habitats, they still preferred foraging from safer bush patches over riskier open patches. This study provides insights into how under low predation risk, strong levels of intraspecific competition can shape the distribution of foragers across and within habitats.

Remote Places As Post-Contact Refugia

ABSTRACTThe arrival of Europeans, and later Americans, to California in the eighteenth and nineteenth centuries led to complex social and economic turmoil for Native Americans. Throughout this period, Native Americans found myriad ways of resisting colonial influence and maintaining traditional ways. In this article, we explore how two places considered “remote” by colonial powers (San Clemente Island and the Coso Range in the Mojave Desert) served as ideal locations for those seeking to remove themselves from the colonial system. Although local cultural and economic circumstances were different, both locations were less desirable to Euroamerican settlers until relatively late in time. Using the ideal free distribution model as a theoretical framework, this article argues that the remoteness of these areas allowed Native cultures to continue in traditional ways until the 1850s on the Channel Islands and the 1870s in the Coso Range.

Pastoralist refugee crisis tests the resilience of open property regime in the Logone Floodplain, Cameroon

Previous studies have shown that the open property regime of mobile pastoralists in the Logone Floodplain, Cameroon works as a complex adaptive system in which individual movement decisions result in an ideal free distribution of grazing pressure over common-pool grazing resources. Recently, the humanitarian crisis in the Chad Basin caused by Boko Haram has resulted in the arrival of thousands of pastoralist refugees from Northeastern Nigeria in the Far North Region of Cameroon. In this paper, we examine the impact of pastoralist refugees on the resilience of the open property regime. First, we describe the migratory flight of pastoralists. Second, we examine whether and how the pastoralist refugee crisis affected the open property regime, in particular the distribution of pastoralists over grazing resources. Data were collected in a longitudinal and interdisciplinary study that integrated spatial and ethnographic approaches to describe and explain the distribution of pastoralists in the Logone Floodplain from 2008 to 2016. The results show that the number of pastoralist refugees from Nigeria exceeds 1000 households with an estimated 100,000 cattle. However, despite the large number of pastoralist refugees, we continue to find evidence of an ideal free distribution of pastoralists over grazing resources in the Logone Floodplain. Moreover, we found that pastoralists, while frustrated by the increasing grazing pressure, remained committed to the ethos of open access. The study offers evidence of the resilience of the open property regime and we discuss the reasons for the resilience of this complex adaptive system using the concept of panarchy.

Effect of interference and exploitative competition on associative learning by a parasitoid wasp: a mechanism for ideal free distribution?

Competition among foraging individuals of the same species occurs for several resources including, but not limited to, food, mates, nesting sites and, in parasitoid wasps, hosts. Individuals should therefore adapt their resource exploitation decisions accordingly and learning ability has been shown to be used in intraspecific competition situations to optimize fitness. We investigated the effect of interference and exploitative competition on aversive learning of a parasitoid wasp Venturia canescens (Hymenoptera: Ichneumonidae) as a model. We studied the effect of the presence of one to five competitors and of prior competitors, that is, the presence of parasitized hosts, on olfactory learning of wasps based on a Pavlovian conditioning system. We found that the odour of peppermint, which was previously positively associated with the reward of an oviposition, was rejected by females that experienced this odour while exploiting a patch of unparasitized hosts in the presence of conspecific females. Unexpectedly, the number of competitors in cases of interference did not increase the level of aversion to the peppermint odour. Thus conditioned stimuli previously encountered during the exploitation of a patch of parasitized hosts were rejected when females oviposited in the presence of unparasitized hosts. Our results suggest that intraspecific competition, by interference and by exploitation, acts as motivation for females to avoid stimuli related to competition; this may explain how an ideal free distribution can be reached by learning processes.

Improving the interpretation of fishing effort and pressures in mixed fisheries using spatial overlap metrics

Managing mixed fisheries requires understanding fishers’ behaviour to allow predicting future fisheries distribution and impact on marine ecosystems. A new approach was developed to compare fine-scale fishing effort distribution of Eastern English Channel (EEC) bottom trawlers to the monthly and spatially resolved abundance distributions of commercial species. First, the added value of using species-specific spatial overlap metric to quantify effective fishing effort and improve the relationship between fishing effort and fishing mortality was assessed. Second, based on the Ideal Free Distribution (IFD) theory, the species-specific weights given by fishers to different species were estimated by maximizing the overlap between target species assemblage and effort distributions in October. At a seasonal scale, our results emphasized the importance of cuttlefish (Sepia officinalis) and red mullet (Mullus surmuletus) for the global distribution of EEC bottom trawlers. In October, cuttlefish and red mullet were clearly more determining fishers’ location choice than historically harvested species and also than the overall expected revenue. This is likely due to external constraints such as low cod (Gadus morhua) quota, causing IFD assumptions violated. This study evidenced the importance of getting good insights into spatiotemporal distributions of stocks and fleets to understand fishers’ behaviour and improve mixed fisheries management advice.

Evolutionarily stable movement strategies in reaction-diffusion models with edge behavior.

Many types of organisms disperse through heterogeneous environments as part of their life histories. For various models of dispersal, including reaction-advection-diffusion models in continuously varying environments, it has been shown by pairwise invasibility analysis that dispersal strategies which generate an ideal free distribution are evolutionarily steady strategies (ESS, also known as evolutionarily stable strategies) and are neighborhood invader strategies (NIS). That is, populations using such strategies can both invade and resist invasion by populations using strategies that do not produce an ideal free distribution. (The ideal free distribution arises from the assumption that organisms inhabiting heterogeneous environments should move to maximize their fitness, which allows a mathematical characterization in terms of fitness equalization.) Classical reaction diffusion models assume that landscapes vary continuously. Landscape ecologists consider landscapes as mosaics of patches where individuals can make movement decisions at sharp interfaces between patches of different quality. We use a recent formulation of reaction-diffusion systems in patchy landscapes to study dispersal strategies by using methods inspired by evolutionary game theory and adaptive dynamics. Specifically, we use a version of pairwise invasibility analysis to show that in patchy environments, the behavioral strategy for movement at boundaries between different patch types that generates an ideal free distribution is both globally evolutionarily steady (ESS) and is a global neighborhood invader strategy (NIS).

The generalized ideal free distribution model: Merging current ideal free distribution models into a central framework

Density-dependent habitat selection is a central theme in ecology. Empirical studies collect data with increasing resolution and provide greater opportunities for its testing. However, several different density-dependent habitat selection models exist in the literature incorporating many different scenarios. We attempt to unify some of these models in a single framework, to increase our predictive power, and assist researchers in making predictions from combinations of these models. To achieve this, we created the generalized ideal free distribution, an expansion of the ideal free distribution model. With this model, we synthesize many of the previous theoretical developments in habitat selection to better incorporate temporal dynamics. By using community matrices to represent the interaction between individuals, we demonstrated that thirteen scenarios represented in other studies can be combined into a single model. In addition, for four of these scenarios, our predictions are similar to the original studies that developed these scenarios. Additionally, we derived four novel predictions that take advantage of using community matrices to represent distribution. We discuss how this model creates a connection between community interactions and the distribution of individuals, and its uses in other subjects in ecology.