How many juvenile Teal Anas crecca reach the wintering grounds? Flyway-scale survival rate inferred from wing age-ratios

Autumn postnuptial migration is critical in the dabbling duck annual cycle, when first-year birds in particular suffer high losses to natural and hunting mortality. Mortality rates in this age-class are generally unknown in Europe where winter ringing predominates. We used data from large-scale wing collections from hunters in Finland, Denmark and France to test the prediction that juvenile proportions among killed Teal (Anas crecca) would decline with distance along the flyway. As expected, this proportion decreased from 89% in Northern Finland to 58% in Western France. Potential biases linked with age determination from the wings, differential migration of age-classes, relative susceptibility to different forms hunting and gradual improvement of juvenile survival as they learn to avoid hunters could not explain the observed decline of juveniles in the shot population. This pattern was therefore considered to be genuine, the result of the cumulative depletion of first-years along the flyway, likely through hunting. On this assumption, combined with known adult monthly survival rates during August–November (94.2%), monthly juvenile survival rate was estimated at 52.8%, i.e. 14.7% (range 13.9–15.4% based on extreme values of adult survival) amongst Scandinavian juveniles reaching wintering quarters in Western France. Despite lack of precision in such estimates based on relative proportions, there is little doubt about the magnitude of autumn juvenile mortality and its consequences for the population dynamics of Teal. Lack of correlations between annual proportions of juveniles in the hunting bag and an index of Teal breeding success in Finland may result from such high and variable inter-annual mortality.     

Long-term trends of heron and egret populations in Italy, and the effects of climate, human-induced mortality, and habitat on population dynamics

Factors affecting bird population dynamics include climate, harvesting by humans, and habitat changes. Here, we describe the long-term (1972–2006) population trends of seven heron species in NW Italy, an area holding important European breeding populations of these species. Grey (Ardea cinerea), purple (Ardea purpurea), and squacco (Ardeola ralloides) herons, and little egrets (Egretta garzetta) exhibited a strong logistic increase, leveling off around year 2000 at 3–23 times their initial level. Black-crowned night herons (Nycticorax nycticorax) began by increasing like the former species but then dropped to initial levels. Such trends were found to be influenced by several candidate ecological factors, as assessed by ARIMA models. Specifically, grey herons increased following a decrease in human-induced mortality, as quantified by an index of hunting pressure, and an increase in winter temperatures. Little egrets increased mainly with the increase of the extent of ricefields, whereas squacco herons increased with increasing rainfall in the African wintering range. Black-crowned night herons were also positively affected by increasing African rainfall, but only during 1972–1988, whereas in later years competition with other herons could have affected the species’ decline. The improved protection of colony sites by special reserves was unlikely to be the primary trigger of the observed increase, although obviously important for the long-term population persistence. In conclusion, our study shows that heron populations of southern Europe are sensitive to environmental and climatic changes, as well as to temporal variation in human disturbance and changes in foraging habitats, though the importance of the different factors differs among species.     

Does habitat structure matter? Spatially explicit population modelling of an Iberian gypsum endemic

Habitat heterogeneity may influence plant demography because conditions for survival, growth, and reproduction vary within a species’ range. We assessed the role of microhabitat spatial structure on the demography of Helianthemum squamatum, a shrubby gypsum specialist endemic to the Iberian Peninsula. We evaluated the demographic effect of microhabitat spatial variation using an approach that combined cellular automata with matrix population models, and included environmental and demographic stochasticty. We collected data on seed bank (2003–2005), seedling emergence (2003–2006), and adult survivorship (2004–2007) for H. squamatum in two independent blocks with different grazing intensity in Belinchón (Cuenca, Spain). We built spatial scenarios for each block based on field data of cover and spatial pattern of four microhabitats: lichenic crust, litter, H. squamatum, and shrub. Seedling survivorship was affected by year, block, and microhabitat, with individuals emerging under conspecifics having the highest survival rate and on litter the lowest in both blocks, whereas the effect of crust and other shrubs differed across blocks. Our models indicated population increase in the block with low grazing, but population decline in the block with intense grazing. We hypothesize that higher pressure of livestock grazing and trampling leads to a shift in relative microhabitat suitability for crust and shrub. This potential effect of grazing on spatial demographic variation opens interesting questions for future research. We emphasize the importance of considering microhabitat spatial structure when evaluating management and conservation strategies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fission–Fusion Dynamics in Southern Muriquis (Brachyteles arachnoides) in Continuous Brazilian Atlantic Forest

Fission–fusion social dynamics, the spatiotemporal variance in subunit size, composition, and cohesion, are the subject of considerable interest owing to their complex nature and widespread appearance in the primate order. We here aim to describe the nature of fission–fusion dynamics in a population of egalitarian southern muriquis inhabiting a relatively undisturbed extension of mildly seasonal Brazilian Atlantic forest to provide insights into the functions of fission–fusion dynamics and to examine the constraints on and opportunities for associations among individuals. We collected instantaneous scan samples and ad libitum data over a total of 13 mo in 2 yr (1599 observation hours) on subunit size at 2 spatiotemporal scales (party and nomadic party), party composition, spatial cohesion, and the behavioral context of fission–fusion events. These southern muriquis exhibited high levels of fission–fusion with significant variation in party size, cohesion, and composition. The group was weakly cohesive with a small mean party size (3.74 adults, 5.32 all individuals) and nomadic party size (13.73 adults, 19.38 all individuals). Mixed parties were the most frequently observed party type, although the high frequency of all-male parties suggests strong relationships based on philopatry and a mating strategy under scramble competition. We compare fission–fusion dynamics across populations of Brachyteles and highlight the striking continuum of these dynamics in the genus. We make interspecific comparisons with Ateles and Pan, with well documented high levels of fission–fusion, and demonstrate interspecific variation and convergence in grouping patterns.     

Competitive reversals inside ecological reserves: the role of external habitat degradation

 Habitat degradation is the slow – and often subtle – deterioration in habitat quality that accompanies human activities through increases in road density, pesticide use, hunting pressure, etc. Such degradation is of particular concern in fragmented habitats where economic or jurisdictional boundaries rather than ecological ones determine the level of exploitation adjoining habitat patches endure. To examine the consequences habitat degradation might have on species interactions, we posited a patch of pristine habitat surrounded by “matrix” habitat whose degradation level was variable. Using a coupled pair of diffusive Lotka–Volterra competition equations with Robin (mixed) boundary conditions, we modeled the dynamics of two competing species inhabiting the pristine patch and incorporated matrix degradation through a tunable “hostility” parameter representing species’ mortality rates in the matrix. We found that the numerical range of competition coefficients over which one species is the competitive dominant and the other inferior may grow or shrink as matrix quality deteriorates. In some cases, degradation of the exterior habitat would bring about a complete competitive reversal inside the preserve. This result, wherein a formerly inferior species supplants a formerly dominant one – even inside the “protected” remnant patch itself – has policy implications for both nature reserve design and management of human activities outside park boundaries. Received: 30 April 1997     

Pintail and Mallard Survival in California Relative to Habitat,Abundance, and Hunting

ABSTRACT The influence of habitat, waterfowl abundance, and hunting on winter survival of waterfowl is not well understood. We studied late August-March survival of 163 after-hatch-year (AHY) and 128 hatch-year (HY) female mallards (Anas platyrhynchos) radiotagged in Sacramento Valley (SACV) and 885 AHY female northern pintails (A. acuta) radiotagged throughout the Central Valley of California, USA, relative to flooded habitat (HAB), January abundance of each species (JMAL or JPIN), hunter-days (HDY), and a hunting pressure index (HPI) that combined these variables. From EARLY (1987–1994) to LATE (1998–2000), HAB increased 39%, JPIN increased 45%, JMAL increased 53%, HDY increased 21%, duck-hunting season increased from 59 days to 100 days, and the female daily bag limit doubled to 2 for mallards but remained 1 for pintails. Survival (± SE) was greater during LATE versus EARLY for pintails radiotagged in each region (SACV: 93.2 ± 2.1% vs. 87.6 ± 3.0%; Suisun Marsh: 86.6 ± 3.2% vs. 77.0 ± 3.7%; San Joaquin Valley: 86.6 ± 3.1% vs. 76.9 ± 4.1%) but not for SACV mallards (AHY: 70.6 ± 7.2% to 74.4 ± 7.7% vs. 80.1 ± 7.2% to 82.8 ± 5.6%; HY: 48.7 ± 9.1% [1999–2000 only] vs. 63.5 ± 8.8% to 67.6 ± 8.0%). Most pintail (72%) and mallard (91%) deaths were from hunting, and lower HPI and higher JPIN or JMAL were associated with reduced mortality. Increased HAB was associated with reduced winter mortality for pintails but not for SACV mallards. Pintail survival rates that we measured were within the range reported for other North American wintering areas, and during LATE were higher than most, even though our study duration was 68–110 days longer. Winter survival rates of SACV mallards were also within the reported range. However, with higher bag limits and longer seasons, mallard survival during LATE was lower than in most other wintering areas, especially during 1999–2000, when high winds on opening weekend resulted in high hunting mortality. Habitat conservation and favorable agriculture practices helped create a Central Valley wintering environment where natural mortality of mallards and pintails was low and survival varied with hunting mortality. We recommend regulations and habitat management that continue to minimize natural mortality while allowing sustainable harvest at a level that helps maintain strong incentive for management of Central Valley waterfowl habitats, including the large portion that is privately owned.     

Spatial Heterogeneity in Habitat Quality and Cross-Scale Interactions in Metapopulations

Abstract Integration of habitat heterogeneity into spatially realistic metapopulation approaches reveals the potential for key cross-scale interactions. Broad-scale environmental gradients and land-use practices can create autocorrelation of habitat quality of suitable patches at intermediate spatial scales. Patch occupancy then depends not only on habitat quality at the patch scale but also on feedbacks from surrounding neighborhoods of autocorrelated patches. Metapopulation dynamics emerge from how demographic and dispersal processes interact with relevant habitat heterogeneity. We provide an empirical example from a metapopulation of round-tailed muskrats (Neofiber alleni) in which habitat quality of suitable patches was spatially autocorrelated most strongly within 1,000 m, which was within the expected dispersal range of the species. After controlling for factors typically considered in metapopulation studies—patch size, local patch quality, patch connectivity—we use a cross-variogram analysis to demonstrate that patch occupancy by muskrats was correlated with habitat quality across scales ≤1,171 m. We also discuss general consequences of spatial heterogeneity of habitat quality for metapopulations related to potential cross-scale interactions. We focus on spatially correlated extinctions and metapopulation persistence, hierarchical scaling of source–sink dynamics, and dispersal decisions by individuals in relation to information constraints.     

Host plant pattern and variation in climate predict the location of natal grounds for migratory monarch butterflies in western North America

The breeding grounds of migrant generation monarch butterflies in eastern North America are well known. In stark contrast the location of natal grounds of western migrants has not been delineated. We show that 55% of the area within seven western states was potential breeding range based on: (1) the occurrence of milkweed host plant species with phenology making them available during late-summer and (2) regional thermal conditions supportive of adult reproductive activity and development of immature stages. We next used a series of spatially explicit “bottom-up” regression models to test this first-approximation natal origins distribution. We tested for associations between variation in moisture availability at putative natal habitat and inter-annual variation in monarch abundance at western wintering sites for a 10 year period (1998–2007). Variation in moisture availability, as measured by Palmer’s drought severity index (PDSI), across the western region predicted monarch abundance patterns. In contrast and as expected, PDSI across known eastern breeding grounds did not predict variation in western monarch migrant abundance. The pattern of moisture availability was not uniform between states or within states and permitted similar tests of association at a finer geographical level. PDSI for California, Idaho, Nevada, and Oregon (but not Arizona, Utah, or Washington) were each significantly associated with monarch wintering abundance patterns with California exhibiting the strongest relationship. At a more focused spatial scale we tested the local recruitment hypothesis. This is the notion that western coastal wintering monarch populations derive only from nearby coastal breeding habitat and that monarchs do not migrate from more distant natal grounds. Variation in moisture availability within a block of three contiguous central California climate divisions (Sacramento Drainage, San Joaquin Drainage, and Southeast Desert Basin) significantly predicted inter-annual abundance of migrant generation monarchs. In contrast PDSI patterns of three coastal California climate divisions, i.e., ones local to wintering sites, as well as that of climate divisions in western Nevada and Arizona did not predict variation in monarch abundance at this more focused spatial resolution. Our findings suggest that moisture regimes act as a strong bottom-up driver of monarch abundance pattern via resource availability in western USA.     

Culling Versus Density Effects in Management of a Deer Population

Abstract: Wildlife managers often manipulate hunting regulations to control deer populations. However, few empirical studies have examined the level of hunting effort (hunter-days) required to limit population growth and demographic effects through harvesting of females. Moreover, the relative importance of density effects on population growth has not been quantified. We reconstructed a sika deer [Cervus nippon] population over a period of 12 years (1990–2001) using age- and sex-specific harvest data. Using cohort analysis, we analyzed population dynamics, focusing on 1) the relationship between hunting effort and hunting-induced mortality rate, 2) relative contributions of hunting mortality and recruitment of yearlings to annual changes in population growth rate, and 3) annual variation in recruitment rate. Population size increased until 1998 and declined thereafter. The population growth rate changed more in response to annual changes in recruitment rate than hunting mortality rate. Temporal variation in recruitment rate was not controlled by birth rate alone; direct density dependence, intensities of hunting mortality for fawns, and for females (≥2 yr of age), which accounted for the fawn survival rate, were required as factors to explain temporal variation. Density effects on the recruitment rate were not strong enough to regulate the population within the study period; high hunting mortality, with intensive female harvesting, was necessary to prevent population growth. Hunting effort was a good predictor of the hunting mortality rate, and female harvest had a negative effect on the recruitment rate through fawn survival. We suggest that >3,500 hunter-days and prioritization of female harvesting are required to prevent increases in this deer population.     

Winter Survival of Female Ring-Necked Ducks in the Southern Atlantic Flyway

North American waterfowl harvest regulations are largely guided by the status of breeding populations. Nonetheless, understanding the demographics of wintering waterfowl populations can elucidate the effects of hunting pressure on population dynamics. The ring-necked duck (Aythya collaris) breeds and winters in all North American administrative flyways and is one of the most abundant and most harvested diving ducks in the Atlantic Flyway. But few studies have investigated the winter ecology of ring-necked ducks. We used a known-fate analysis to estimate period survival probability using data from 87 female ring-necked ducks marked with satellite transmitters in 2 regions of the southern Atlantic Flyway during winters of 2017–2018 and 2018–2019. Winter (128-day) survival probability was higher for individuals in the Red Hills region of southern Georgia and northern Florida (0.875, 95% CI = 0.691–0.952) than individuals in central South Carolina (0.288, 95% CI = 0.082–0.514). We attribute the regional disparity in winter survival probabilities to differences in hunting pressure, which are reflected in the number of harvests we observed in each region. Our findings warrant further investigation into regional variation in winter survival of southern Atlantic Flyway ring-necked ducks, and, specifically, the relationship between variable harvest pressure and winter survival and its influence on ring-necked duck population dynamics and adaptive harvest management decisions. © 2020 The Wildlife Society.     

Survival and cause-specific mortality of female Rocky Mountain elk exposed to human activity

Animal populations are becoming increasingly exposed to human activity as human populations expand and demand for energy resources (e.g., coal, oil and natural gas) increases. We initiated this study to document survival and cause-specific mortality patterns of female Rocky Mountain elk (Cervus elaphus) exposed to increasing levels of human activity. We fitted 184 females with VHF or GPS collars over 4 years and used the Kaplan–Meier survival estimator to calculate annual survival rates. We used multinomial logistic regression to assess differences in cause-specific mortality and generalized linear mixed models to determine how probability of survival was structured during hunting season; both analyses examined a suite of 5 covariates (i.e., age, year, extent of space use, cover, and human footprint) as potentially influencing cause-specific mortality and survival probability. Annual probability of survival averaged 0.8 (±0.02 SE) over 4 years but averaged 0.91 (±0.03 SE) when harvest mortality was excluded, which was the most significant source of mortality in most years ( [`(x)] = 0.13 ±0.02 \textSE \bar{x} = 0.13 \pm 0.02\,{\text{SE}} ). We found no difference between cause-specific mortality sources relative to elk that survived during the hunting season (χ ₁₀² = 5.79, P = 0.832). The probability of a female surviving during hunting season was negatively influenced by age, year, extent of space use, cover, and human footprint. We found evidence that human activity may have influenced annual rates of natural survival (i.e., exclusive of hunting mortality) and probability of survival during the hunting season. We note that this study occurred largely on privately owned and managed residential and ranch land and focused on female elk; we acknowledge that survival rate and cause-specific patterns of mortality may vary as a function of land ownership (private vs. public), demographic status, and management and harvest practices. While temporal and spatial scales of 1 week may be sufficient to describe patterns of direct mortality during hunting season, broad temporal or spatial scale analyses may be needed to address natural mortality during other seasons.     

Endogenous reserve dynamics of northern common eiders wintering in Greenland

Endogenous reserves influence both survival and reproduction of many waterfowl species, but little is known about reserve levels of most species during the nonbreeding season, particularly those wintering at high latitudes. We investigated whether age, sex, and season were related to carcass composition of northern common eiders (Somateria mollissima borealis) wintering in southwest Greenland during 1999–2002. Adults carried more lipid and protein than juveniles during all winters. Among both age classes, males and females had similar fat levels but males carried slightly more protein. There was no dramatic seasonal variation in lipid or protein content. This suggests that during the period of this study, these eiders did not experience large-scale nutritional shortfalls. As predicted, Greenlandic eiders carried more lipid reserves than eider populations wintering in more temperate environments. Contrary to prediction, there was little relation between reserve levels and photoperiod, ambient temperature, or hunting disturbance intensity. Our results suggest that both sexes are equally capable of dealing with nutritional deficits, and that juvenile birds are more prone to nutritional stress as evidenced by their consistently poorer body condition.     

Coevolution at multiple spatial scales: Linum marginale–Melampsora lini – from the individual to the species

Coevolutionary processes are intrinsically spatial as well as temporal, and occur at many different scales. These range from single populations dominated by demographic and genetic stochasticity, to metapopulations in which colonisation/extinction dynamics have a large influence, and larger geographic regions where phylogenetic patterns and historical events become important. We present data for the genetically and demographically well-characterised plant host–pathogen interaction, the Linum marginale–Melampsora lini system, and use this to demonstrate the varying nature of resistance and virulence structure across these spatial scales. At the within population level, our results indicate considerable variability in resistance and virulence, but little evidence of coordinated changes in host and pathogen. Studies involving comparisons among multiple demes within a single metapopulation show that adjacent populations often have asynchronous disease dynamics and large differences in diversity and frequency of resistance and virulence phenotypes. Nevertheless, at this scale, there is also evidence of spatial structure in that more closely adjacent host populations are significantly more likely to have similar resistance phenotypes and mean levels of resistance. At larger scales, comparisons among adjacent metapopulations indicate that quantitative differences in host mating system and other life history features can have further major consequences for how host and pathogen variation is packaged. Finally, comparisons at continental and among host-species levels show variation consistent with specialisation and speciation in the pathogen. This revised version was published online in July 2006 with corrections to the Cover Date.     

Disentangling the effects of predation and oceanographic fluctuations in the mortality of two allopatric seabird populations

Life-history traits of migratory seabirds are influenced by changing conditions at breeding and wintering grounds. Climatic conditions and predation are known to impact populations’ survival rates, but few studies examine their effect simultaneously. We used multievent capture–recapture models to assess mortality due to environmental conditions and predation in breeding European storm petrels (Hydrobates pelagicus) in two allopatric colonies (Mediterranean and Atlantic). Predatory mortality at the colonies showed annual variation, being around 0.05 in certain years. Mortality at sea differed between the two oceanic basins, and was lower in the Mediterranean colony [0.11, 95% CI (0.09, 0.14)] when compared to the Atlantic colony [0.18, 95% CI (0.15, 0.22)]. The Western Mediterranean Oscillation index (WeMOi) explained 57% of the temporal variability in mortality of Mediterranean breeders. In comparison, 43% of the temporal variability in mortality of Atlantic breeders was explained by the winter St Helena index (wHIX) and El Niño-Southern Oscillation index (wENSO). Our results suggest that Mediterranean breeders remain in this basin for wintering where they may face lower migratory costs and more favourable environmental conditions. In contrast, Atlantic breeders’ mortality may be due to higher cost of migration, changing upwelling conditions in the Benguela current and heavy storms over their migratory route during La Niña events. This study underlines the importance of modelling separately different causes of mortality when testing the effects of climatic covariates.     

Density dependence in northern ungulates: interactions with predation and resources

Variation in the abundance of animals has traditionally been explained as the outcome of endogenous forcing from density dependence and exogenous forcing arising from variation in weather and predation. Emerging evidence suggests that the effects of density dependence interact with external influences on population dynamics. In particular, spatial heterogeneity in resources and the presence of capable predators may weaken feedbacks from density dependence to growth of populations. We used the Kalman filter to analyze 23 time series of estimates of abundance of northern ungulate populations arrayed along a latitudinal gradient (latitude range of 40°–70°N) to evaluate the influence of spatial heterogeneity in resources and predation on density dependence. We also used contingency tables to test whether density dependence was independent of the presence of carnivores (our estimate of predation) and multiple regressions to determine the effects of spatial heterogeneity in resources, predation, and latitude on the strength of density dependence. Our results showed that the strength of density dependence of ungulate populations was low in the presence of large carnivores, particularly at northern latitudes with low primary productivity. We found that heterogeneity in elevation, which we assume acted as a surrogate for spatial heterogeneity in plant phenology, also reduced effects of density dependence. Thus, we show that external forces created by heterogeneity in resources and predation interact with internal feedbacks from population density to shape dynamics of populations of northern ungulates.     

Identification of source‐sink dynamics in mountain lions of the Great Basin

Natural and anthropogenic boundaries have been shown to affect population dynamics and population structure for many species with movement patterns at the landscape level. Understanding population boundaries and movement rates in the field for species that are cryptic and occur at low densities is often extremely difficult and logistically prohibitive; however genetic techniques may offer insights that have previously been unattainable. We analysed thirteen microsatellite loci for 739 mountain lions (Puma concolor) using muscle tissue samples from individuals in the Great Basin throughout Nevada and the Sierra Nevada mountain range to test the hypothesis that heterogeneous hunting pressure results in source‐sink dynamics at the landscape scale. We used a combination of non‐spatial and spatial model‐based Bayesian clustering methods to identify genetic populations. We then used a recently developed Bayesian multilocus genotyping method to estimate asymmetrical rates of contemporary movement between those subpopulations and to identify source and sink populations. We identified two populations at the highest level of genetic structuring with a total of five subpopulations in the Great Basin of Nevada and the Sierra Nevada range. Our results suggest that source‐sink dynamics occur at landscape scales for wide‐ranging species, such as mountain lions, and that source populations may be those that are under relatively less hunting pressure and that occupy refugia.     

The spatial scale of competition from recruits on an older cohort in Atlantic salmon

Competitive effects of younger cohorts on older ones are frequently assumed to be negligible in species where older, larger individuals dominate in pairwise behavioural interactions. Here, we provide field estimates of such competition by recruits on an older age class in Atlantic salmon (Salmo salar), a species where observational studies have documented strong body size advantages which should favour older individuals in direct interactions. By creating realistic levels of spatial variation in the density of underyearling (YOY) recruits over a 1-km stretch of a stream, and obtaining accurate measurements of individual growth rates of overyearlings (parr) from capture–mark–recapture data on a fine spatial scale, we demonstrate that high YOY density can substantially decrease parr growth. Models integrating multiple spatial scales indicated that parr were influenced by YOY density within 16 m. The preferred model suggested parr daily mass increase to be reduced by 39% when increasing YOY density from 0.0 to 1.0 m⁻², which is well within the range of naturally occurring densities. Reduced juvenile growth rates will in general be expected to reduce juvenile survival (via increased length of exposure to freshwater mortality) and increase generation times (via increased age at seaward migrations). Thus, increased recruitment can significantly affect the performance of older cohorts, with important implications for population dynamics. Our results highlight that, even for the wide range of organisms that rely on defendable resources, the direction of competition among age classes cannot be assumed a priori or be inferred from behavioural observations alone.     

The non-impact of hunting on moose <Emphasis Type="Italic">Alces alces</Emphasis> movement,diurnal activity,and activity range

Previous studies on moose Alces alces have suggested that interactions with humans may trigger anti-predator behaviors and generate a demographical cost. Therefore, we hypothesized that disturbances from small and big game hunting may have negative effects on moose movements, diurnal activity, and activity range. Using location data from 64 moose equipped with GPS collars from three populations (Low Alpine, Inland, Coastal) with different temporal human presence and spatial accessibility, we evaluated the impact of hunting on moose activity rhythms. On average, female moose in the low human population density (Low Alpine) area (<0.5/km²) had significantly lower movement rates during moose hunting season, but variation in movement rates among individuals were higher compared with female moose in regions with denser human populations (6–24/km²). We found no evidence that reproductive status influenced female moose sensitivity to disturbance. As expected, females used smaller activity ranges and were less active nocturnally than males. The high within-group variation suggests that current hunting disturbance levels do not alter moose population behavior in general. Our data indicate that alterations in movement were related to rutting activity, not human disturbance induced by hunting. In line with behavioral theory, our study suggests that some individuals were more sensitive to hunting disturbance than the general population. Our work suggests that individual moose may perceive human predation risk to be similar to other predation risks.     

Simple models for complex systems: exploiting the relationship between local and global densities

Simple temporal models that ignore the spatial nature of interactions and track only changes in mean quantities, such as global densities, are typically used under the unrealistic assumption that individuals are well mixed. These so-called mean-field models are often considered overly simplified, given the ample evidence for distributed interactions and spatial heterogeneity over broad ranges of scales. Here, we present one reason why such simple population models may work even when mass-action assumptions do not hold: spatial structure is present but it relates to global densities in a special way. With an individual-based predator–prey model that is spatial and stochastic, and whose mean-field counterpart is the classic Lotka–Volterra model, we show that the global densities and densities of pairs (or spatial covariances) establish a bi-power law at the stationary state and also in their transient approach to this state. This relationship implies that the dynamics of global densities can be written simply as a function of those densities alone without invoking pairs (or higher order moments). The exponents of the bi-power law for the predation rate exhibit a remarkable robustness to changes in model parameters. Evidence is presented for a connection of our findings to the existence of a critical phase transition in the dynamics of the spatial system. We discuss the application of similar modified mean-field equations to other ecological systems for which similar transitions have been described, both in models and empirical data.     

Distance decay of community dynamics in rocky intertidal sessile assemblages evaluated by transition matrix models

It is well known that the similarity in species composition between two communities decays with the geographic distance that separates them. It is thus likely that the similarity in the dynamics of two communities also decays with distance, because the distance–decay relationship is fundamental in nature. However, the distance–decay relationships of community dynamics have not yet been revealed. We used transition matrix models to evaluate distance–decay relationships of seasonal community dynamics (from spring to summer) in rocky intertidal sessile assemblages along the Pacific coast of Japan between 31°N and 43°N. We evaluated the distance–decay relationships of whole-community dynamics and of three dynamics-related components—recruitment, disturbance, and species interaction (competition and facilitation)—for communities separated by distances ranging from several meters to thousands of kilometers. The similarity of the recruitment dynamics among communities declined rapidly with distance within the fine spatial scale, but only moderately within larger scales. The similarity of the disturbance dynamics was independent of distance, and the similarity of species interaction declined slightly with increasing distance. The similarity of whole-community dynamics declined rapidly with distance at a fine spatial scale and moderately at larger scales. The fact that the distance–decay relationship of whole-community dynamics was similar to that of recruitment may suggest that recruitment processes are the most important determinant of spatial variability of community dynamics at our study sites during the study period.