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Habitat Complexity (habitat + complexity)

Distribution by Scientific Domains

Life Sciences	72%
Earth and Environmental Science	18%

Selected Abstracts

Quantifying habitat structure: surface convolution and living space for species in complex environments

OIKOS, Issue 12 2008
D. M. Warfe
Habitat complexity is often used to explain the distribution of species in environments, yet the ability to predict outcomes of structural differences between habitats remains elusive. This stems from the difficulty and lack of consistency in measuring and quantifying habitat structure, making comparison between different habitats and systems problematic. For any measure of habitat structure to be useful it needs to be applicable to a range of habitats and have relevance to their associated fauna. We measured three differently-shaped macrophyte analogues with nine indices of habitat structure to determine which would best distinguish between their shape and relate to the abundance and rarefied species richness of their associated macroinvertebrate assemblages. These indices included the physical, whole-plant attributes of surface area (SA) and plant volume (PV), the interstitial space attributes of average space size and frequency (ISI), average refuge space from predation (Sp/Pr), and total refuge space (FFV), and the degree of surface convolution at a range of scales (i.e. the fractal dimension at four spatial scales: 7.5×, 5×, 2.5× and 1× magnification). We found a high degree of inter-correlation between the structural indices such that they could be organised into two suites: one group describing interstitial space and surface convolution at coarse scales, the other describing whole-plant attributes and surface convolution at fine scales. Two of these indices fell into both suites: the average refuge space from predation (Sp/Pr) and the fractal dimension at 5× magnification. These two measures were also strongly related to macroinvertebrate abundance and rarefied species richness, which points to their usefulness in quantifying habitat structure and illustrates that habitat structure depends not just on shape, but on the space associated with shape. [source]

Habitat complexity modulates phenotype expression through developmental plasticity in the threespine stickleback

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010
MÓNICA V. GARDUÑO-PAZ
The expression of alternative phenotypes within a single species is often considered to be the result of ontogenetic processes and specifically phenotypic plasticity responses to exposure to different environmental conditions. In fish, which have been widely used to test such questions, exposure to different diets is the most frequently described initiator of plastic responses. The effect of physical characteristics of the habitat on fish morphology has not been fully explored. In the present study, a clear effect of habitat complexity on fish shape was found. Threespine sticklebacks were exposed to two different habitat treatments, simple and complex, over a 17-week period. The exposure to the habitats resulted in the expression of very significant differences in body and head morphologies and spine position, showing that the physical environment can modulate the expression of traits through phenotypic plasticity during ontogeny. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 407,413. [source]

Understanding the temporal dynamics of the wandering Renous River, New Brunswick, Canada

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2005
Leif M. Burge
Abstract Wandering rivers are composed of individual anabranches surrounding semi-permanent islands, linked by single channel reaches. Wandering rivers are important because they provide habitat complexity for aquatic organisms, including salmonids. An anabranch cycle model was developed from previous literature and field observations to illustrate how anabranches within the wandering pattern change from single to multiple channels and vice versa over a number of decades. The model was used to investigate the temporal dynamics of a wandering river through historical case studies and channel characteristics from field data. The wandering Renous River, New Brunswick, was mapped from aerial photographs (1945, 1965, 1983 and 1999) to determine river pattern statistics and for historical analysis of case studies. Five case studies consisting of a stable single channel, newly formed anabranches, anabranches gaining stability following creation, stable anabranches, and an abandoning anabranch were investigated in detail. Long profiles, hydraulic geometry, channel energy, grain size and sediment mobility variables were calculated for each channel. Within the Renous study area, the frequency of channel formation and abandonment were similar over the 54 years of analysis, indicating that the wandering pattern is being maintained. Eight anabranches were formed through avulsions, five were formed through the emergence of islands from channel bars and 11 anabranches were abandoned. The stable anabranch pair displayed similar hydraulic geometry and channel energy characteristics, while unstable anabranch pairs did not. The anabranch pair that gained stability displayed more similar channel energy characteristics than the anabranch pair that was losing stability (abandoning). It appears that anabranch pairs with similar energy characteristics are more stable than anabranches where these characteristics are out of balance. This is consistent with the hypothesis that anabranch pairs of similar length will be more stable than those with dissimilar lengths. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Species,energy relationships and habitat complexity in bird communities

ECOLOGY LETTERS, Issue 8 2004
Allen H. Hurlbert
Abstract Species,energy theory is a commonly invoked theory predicting a positive relationship between species richness and available energy. The More Individuals Hypothesis (MIH) attempts to explain this pattern, and assumes that areas with greater food resources support more individuals, and that communities with more individuals include more species. Using a large dataset for North American birds, I tested these predictions of the MIH, and also examined the effect of habitat complexity on community structure. I found qualitative support for the relationships predicted by the MIH, however, the MIH alone was inadequate for fully explaining richness patterns. Communities in more productive sites had more individuals, but they also had more even relative abundance distributions such that a given number of individuals yielded a greater number of species. Richness and evenness were also higher in structurally complex forests compared to structurally more simple grasslands when controlling for available energy. [source]

Influences of habitat complexity on the diversity and abundance of epiphytic invertebrates on plants

FRESHWATER BIOLOGY, Issue 4 2003
Hiromi Taniguchi
SUMMARY 1. The compound influence of habitat complexity and patch size on stream invertebrate assemblages associated with submerged macrophytes was investigated through field sampling of two natural macrophyte species with contrasting leaf morphologies (complex, Ranunculus yezoensis; simple, Sparganium emersum) and an experiment with two artificial plants with different levels of morphological complexity. 2. The artificial plant experiment was designed to separate the effects of habitat area (patch size) and habitat complexity, thus enabling a more rigorous assessment of complexity per se than in previous studies where only a single patch size was used. Simple and complex artificial plants were established with five different patch sizes corresponding to the range found in natural plants. 3. Invertebrates occurred on both complex and simple forms of natural and artificial plants at similar abundances with dipterans and ephemeropterans being predominant. Taxon richness was higher on structurally complex Ranunculus than on simple Sparganium and was similarly higher on the complex artificial plant than on the simple one, over the entire range of habitat patch sizes. Thus, architectural complexity affected the taxon richness of epiphytic invertebrates, independently of habitat scale. 4. On the natural plants there was no difference in the abundance (both number of individuals and biomass) of invertebrates between simple and complex forms, while on artificial plants more invertebrates occurred on complex than on simple forms. The amount of particulate organic matter, >225 ,m (POM) and chlorophyll a showed mixed patterns on natural and artificial plants, suggesting that the availability of these resources is not an overriding proximate factor controlling invertebrate abundance on plants. The difficulty of extrapolating from experimental results involving use of artificial plants is discussed, especially when considering the relationship between habitat structure and the occurrence of epiphytic invertebrates on natural plants. [source]

Biodiversity on land and in the sea

GEOLOGICAL JOURNAL, Issue 3-4 2001
Michael J. Benton
Abstract Life on land today is as much as 25 times as diverse as life in the sea. Paradoxically, this extraordinarily high level of continental biodiversity has been achieved in a shorter time and it occupies a much smaller area of the Earth's surface than does marine biodiversity. Raw palaeontological data suggest very different models for the diversification of life on land and in the sea. The well-studied marine fossil record appears to show evidence for an equilibrium model of diversification, with phases of rapid radiation, followed by plateaux that may indicate times of equilibrium diversity. The continental fossil record shows exponential diversification from the Silurian to the present. These differences appear to be real: the continental fossil record is unlikely to be so poor that all evidence for a high initial equilibrial diversity has been lost. In addition, it is not clear that the apparently equilibrial marine model is correct, since it is founded on studies at familial level. At species level, a logistic family-level curve probably breaks down to an exponential. The rocketing diversification rates of flowering plants, insects, and other land life are evidently hugely different from the more sluggish rates of diversification of life in the sea, perhaps as a result of greater endemism and habitat complexity on land. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Exploitation and habitat degradation as agents of change within coral reef fish communities

GLOBAL CHANGE BIOLOGY, Issue 12 2008
S. K. WILSON
Abstract Over-exploitation and habitat degradation are the two major drivers of global environmental change and are responsible for local extinctions and declining ecosystem services. Here we compare the top-down effect of exploitation by fishing with the bottom-up influence of habitat loss on fish communities in the most diverse of ecological systems, coral reefs. Using a combination of multivariate techniques and path analyses, we illustrate that the relative importance of coral cover and fishing in controlling fish abundance on remote Fijian reefs varies between species and functional groups. A decline in branching Acropora coral is strongly associated with a decline in abundance of coral-feeding species, and a decrease in coral-associated habitat complexity, which has indirectly contributed to reduced abundance of small-bodied damselfish. In contrast, reduced fishing pressure, brought about by declining human populations and a shift to alternate livelihoods, is associated with increased abundance of some piscivores and fisheries target species. However, availability of prey is controlled by coral-associated habitat complexity and appears to be a more important driver of total piscivore abundance compared with fishing pressure. Effects of both fishing and coral loss are stronger on individual species than functional groups, as variation in the relative importance of fishing or coral loss among species within the same functional group attenuated the impact of either of these potential drivers at the functional level. Overall, fishing continues to have an influence on Fijian fish communities; however, habitat loss is currently the overriding agent of change. The importance of coral loss mediated by climate change is expected to have an increasing contribution to fish community dynamics, particularly in remote locations or where the influence of fishing is waning. [source]

The effect of habitat complexity on the functional response of a seed-eating passerine

IBIS, Issue 3 2009
DAVID J. BAKER
Recent population declines of seed-eating farmland birds have been associated with reduced overwinter survival due to reductions in food supply. An important component of predicting how food shortages will affect animal populations is to measure the functional response, i.e. the relationship between food density and feeding rate, over the range of environmental conditions experienced by foraging animals. Crop stubble fields are an important foraging habitat for many species of seed-eating farmland bird. However, some important questions remain regarding farmland bird foraging behaviour in this habitat, and in particular the effect of stubble on farmland bird functional responses is unknown. We measured the functional responses of a seed-eating passerine, the Chaffinch Fringilla coelebs, consuming seeds placed on the substrate surface in three different treatments: bare soil, low density stubble and high density stubble. Stubble presence significantly reduced feeding rates, but there was no significant difference between the two stubble treatments. Stubble reduced feeding rates by reducing the maximum attack distance, i.e. the distance over which an individual food item is targeted and consumed. The searching speed, handling time per seed, proportion of time spent vigilant, duration of vigilance bouts and duration of head-down search periods were unaffected by the presence of stubble. The frequency of vigilance bouts was higher in the bare soil treatment, but this is likely to be a consequence of the increased feeding rate. We show the influence of a key habitat type on the functional response of a seed-eating passerine, and discuss the consequences of this for farmland bird conservation. [source]

Effects of predatory ants on lower trophic levels across a gradient of coffee management complexity

JOURNAL OF ANIMAL ECOLOGY, Issue 3 2008
S. M. Philpott
Summary 1Ants are important predators in agricultural systems, and have complex and often strong effects on lower trophic levels. Agricultural intensification reduces habitat complexity, food web diversity and structure, and affects predator communities. Theory predicts that strong top-down cascades are less likely to occur as habitat and food web complexity decrease. 2To examine relationships between habitat complexity and predator effects, we excluded ants from coffee plants in coffee agroecosystems varying in vegetation complexity. Specifically, we studied the effects of eliminating ants on arthropod assemblages, herbivory, damage by the coffee berry borer and coffee yields in four sites differing in management intensification. We also sampled ant assemblages in each management type to see whether changes in ant assemblages relate to any observed changes in top-down effects. 3Removing ants did not change total arthropod densities, herbivory, coffee berry borer damage or coffee yields. Ants did affect densities of some arthropod orders, but did not affect densities of different feeding groups. The effects of ants on lower trophic levels did not change with coffee management intensity. 4Diversity and activity of ants on experimental plants did not change with coffee intensification, but the ant species composition differed. 5Although variation in habitat complexity may affect trophic cascades, manipulating predatory ants across a range of coffee agroecosystems varying in management intensity did not result in differing effects on arthropod assemblages, herbivory, coffee berry borer attack or coffee yields. Thus, there is no clear pattern that top-down effects of ants in coffee agroecosystems intensify or dampen with decreased habitat complexity. [source]

Caddisfly diapause aggregations facilitate benthic invertebrate colonization

JOURNAL OF ANIMAL ECOLOGY, Issue 6 2003
Declan J. McCabe
Summary 1We used natural and manipulative field experiments to examine the effects of caddisfly (Trichoptera) diapause aggregations on benthic macroinvertebrates communities in a Vermont river. 2Natural substrates with aggregations of Neophylax and Brachycentrus (Trichoptera: Uenoidae and Brachycentridae) had higher species richness than did substrates lacking aggregations. Aggregations of caddisfly cases added to artificial substrates (bricks) also accumulated greater abundance, species density (number of species per unit area), and species richness (number of species per standard number of individuals) than did control bricks. 3Low-density, uniformly spaced, Brachycentrus cases accumulated higher species density and species richness than did an equivalent density of clumped cases. Similarly, empty Neophylax cases accumulated higher diversity than did cases still occupied by Neophylax pupae. 4Although natural substrates had higher species richness than artificial substrates, substrate type did not change qualitatively the effect of caddisfly aggregations on species richness. 5We subsampled individuals randomly from aggregations and control surfaces to provide an estimate of species richness unbiased by abundance. Expected species richness was higher in aggregations than on control surfaces. These results suggest that caddisfly aggregations increase species density by altering the shape of the species,abundance distribution as well as by accumulating individuals and species passively. 6We conclude that caddisfly diapause aggregations increase habitat complexity and facilitate colonization of other benthic species. [source]

Community effects of invasive macrophyte control: role of invasive plant abundance and habitat complexity

JOURNAL OF APPLIED ECOLOGY, Issue 2 2010
Katya E. Kovalenko
Summary 1. The control of invasive species has become a widespread management practice, yet information on the community effects of such efforts is very limited, there is no unified framework for monitoring their success and no guidelines exist to help minimize potential adverse impacts. 2. This study was conducted to determine how long-term efforts to control a widespread invasive macrophyte, Eurasian watermilfoil, affect native macrophytes, fish and macroinvertebrates. In addition, we examined how members of the aquatic fauna respond to changes in invasive macrophyte abundance and habitat complexity to understand the mechanisms underlying any potential community response. 3. Selective control of the invasive macrophyte had minor effects on habitat complexity due to timely recolonization by native macrophytes and it did not affect littoral fish richness and abundance. Macroinvertebrate communities were highly variable and some of that variation could be attributed to characteristics of the macrophyte community. Fish and macroinvertebrates were more affected by habitat complexity than by other attributes of the macrophyte assemblage. 4.Synthesis and applications. Management plans to control invasive species need to prioritize selective removal and timely restoration of the native assemblage. In this study, the invasive macrophyte was used by aquatic fauna, which emphasizes the need for immediate restoration of the native macrophyte community to mitigate for the lost habitat after invasive plant control efforts. As both fish and macroinvertebrates were more affected by complexity than other attributes of the macrophyte assemblage, re-establishment of habitat complexity appears to be a promising restoration strategy. On a more general note, we highlight the importance of assessing community response to the habitat provided by the invader and invader's function in the community when evaluating strategies to control invasive species. [source]

Anthropogenic impacts on lake and stream ecosystems, and approaches to restoration

JOURNAL OF APPLIED ECOLOGY, Issue 6 2007
MARTIN SØNDERGAARD
Summary 1Freshwater ecosystems have long been affected by numerous types of human interventions that have a negative impact on their water quality and ecological state. Fortunately, in most western countries the input of sewage to freshwater systems has been reduced, but hydromorphological alterations, eutrophication-related turbidity and loss of biodiversity remain major problems in many parts of the world. Such impacts prevent the achievement of a high or good ecological state, as defined by the European Water Framework Directive (WFD) or other standards. 2This paper synthesizes and links the findings presented in the seven papers of this special profile, focusing on the effects of anthropogenic stressors on freshwater ecosystems and on how to maintain and restore ecological quality. The papers cover a broad range of research areas and methods, but are all centred on the relationship between dispersal barriers, the connectivity of waterways and the restoration of rivers and lakes. 3The construction of dams and reservoirs disturbs the natural functioning of many streams and rivers and shore-line development around lakes may reduce habitat complexity. New methods demonstrate how reservoirs may have a severe impact on the distribution and connectivity of fish populations, and new techniques illustrate the potential of using graph theory and connectivity models to illustrate the ecological implications. Hydromorphologically degraded rivers and streams can be restored by addition of wood debris, but ,passive' restoration via natural wood recruitment may be preferable. The most cost-effective way to restore streams may also include information campaigns to farmers on best management practices. Removal of zooplanktivorous fish often has marked positive effects on trophic structure in lakes, but there is a tendency to return to turbid conditions after 8,10 years or less unless fish removal is repeated. 4Synthesis and applications. Development of new methods, as well as derivation of more general conclusions from reviewing the effects of previous restoration efforts, are crucial to achieve progress in applied freshwater research. The papers contained in this Special Profile contribute on both counts, as well as illustrating the importance of well-designed research projects and monitoring programmes to record the effects of the interventions. Such efforts are vital if we are to improve our knowledge of freshwater systems and to elaborate the best and most cost-effective recommendations. They may also help in achieving a good ecological state or potential in water bodies by 2015, as demanded by the European WFD. [source]

Local,regional boundary shifts in oribatid mite (Acari: Oribatida) communities: species,area relationships in arboreal habitat islands of a coastal temperate rain forest, Vancouver Island, Canada

JOURNAL OF BIOGEOGRAPHY, Issue 9 2007
Zoë Lindo
Abstract Aim, This study investigates the species,area relationship (SAR) for oribatid mite communities of isolated suspended soil habitats, and compares the shape and slope of the SAR with a nested data set collected over three spatial scales (core, patch and tree level). We investigate whether scale dependence is exhibited in the nested sampling design, use multivariate regression models to elucidate factors affecting richness and abundance patterns, and ask whether the community composition of oribatid mites changes in suspended soil patches of different sizes. Location, Walbran Valley, Vancouver Island, Canada. Methods, A total of 216 core samples were collected from 72 small, medium and large isolated suspended soil habitats in six western redcedar trees in June 2005. The relationship between oribatid species richness and habitat volume was modelled for suspended soil habitat isolates (type 3) and a nested sampling design (type 1) over multiple spatial scales. Nonlinear estimation parameterized linear, power and Weibull function regression models for both SAR designs, and these were assessed for best fit using R2 and Akaike's information criteria (,AIC) values. Factors affecting oribatid mite species richness and standardized abundance (number per g dry weight) were analysed by anova and linear regression models. Results, Sixty-seven species of oribatid mites were identified from 9064 adult specimens. Surface area and moisture content of suspended soils contributed to the variation in species richness, while overall oribatid mite abundance was explained by moisture and depth. A power-law function best described the isolate SAR (S = 3.97 × A0.12, R2 = 0.247, F1,70 = 22.450, P < 0.001), although linear and Weibull functions were also valid models. Oribatid mite species richness in nested samples closely fitted a power-law model (S = 1.96 × A0.39, R2 = 0.854, F1,18 = 2693.6, P < 0.001). The nested SAR constructed over spatial scales of core, patch and tree levels proved to be scale-independent. Main conclusions, Unique microhabitats provided by well developed suspended soil accumulations are a habitat template responsible for the diversity of canopy oribatid mites. Species,area relationships of isolate vs. nested species richness data differed in the rate of accumulation of species with increased area. We suggest that colonization history, stability of suspended soil environments, and structural habitat complexity at local and regional scales are major determinants of arboreal oribatid mite species richness. [source]

Ecosystem engineering across ecosystems: do engineer species sharing common features have generalized or idiosyncratic effects on species diversity?

JOURNAL OF BIOGEOGRAPHY, Issue 2 2006
Ernesto I. Badano
Abstract Aim, To integrate the effects of ecosystem engineers (organisms that create, maintain or destroy habitat for other species) sharing the same archetype on species diversity, and assess whether different engineer species have generalized or idiosyncratic effects across environmentally similar ecosystems. Location, High-Andean habitats of Chile and Argentina, from 23° S to 41° S. Methods, We measured and compared the effects of eight alpine plants with cushion growth-form on species richness, species diversity (measured as the Shannon,Wiener index) and evenness of vascular plant assemblages across four high-Andean ecosystems of Chile and Argentina. Results, The presence of cushion plants always increased the species richness, diversity (measured as the Shannon,Wiener index) and evenness of high-Andean plant assemblages. However, while the presence of different cushion species within the same ecosystem controlled species diversity in the same way, these effects varied between cushion species from different ecosystems. Main conclusions, Results consistently supported the idea that increases in habitat complexity due to the presence of ecosystem engineers, in this case cushion plants, would lead to higher community diversity. Results also indicate that effects of the presence of different cushion species within the same ecosystem could be generalized, while the effects of cushion species from different ecosystems should be considered idiosyncratic. [source]

Relationships between fish assemblages, macrophytes and environmental gradients in the Amazon River floodplain

JOURNAL OF FISH BIOLOGY, Issue 3 2003
P. Petry
During the flood season of 1992,1993, 139 species of fishes were collected from a floodplain lake system in the central Amazon Basin. Fish species distribution was examined relative to abiotic variables in seven vegetation strata on Marchantaria Island, Solimões River. Both environmental variables and species distributions were influenced by a river channel to floodplain-interior gradient. Species diversity was significantly higher in vegetated areas than in unvegetated areas, with deeper water Paspalum repens stands harbouring the highest diversity. As a result, species richness and catches were positively related to habitat complexity, while catch was also negatively related to dissolved oxygen (DO) and water depth. Low DO and shallow waters appeared to act as a refuge from predation. Fish assemblages were related to water chemistry, but species richness was not. Canonical correspondence analysis provided evidence that floodplain fish assemblages formed by the 76 most common species were influenced by physical variables, macrophyte coverage and habitat complexity, which jointly accounted for 67% of the variance of fish species assemblages. Omnivores showed no pattern relative to the river channel to floodplain-interior gradient while detritivores were more likely to be found at interior floodplain sites and piscivores closer to the river. Piscivores could be further separated into three groups, one with seven species associated with free-floating macrophytes in deep water, a second with five species found in shallow waters with rooted grasses and a third with six open water orientated species. The results suggest that fish assemblages in the Amazon floodplain are not random associations of species. [source]

Spiders (Araneae) associated with downed woody material in a deciduous forest in central Alberta, Canada

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2001
Christopher M. Buddle
Abstract 1,Spiders (Araneae) were collected on and near downed woody material (DWM) in a Populus -dominated forest to determine if spiders utilize wood surfaces, and to ascertain the importance of DWM habitat and wood elevation for spider assemblages. 2,Over 10 000 spiders representing 100 species were collected. Although more spiders were collected on the forest floor, spider diversity was higher in traps located on wood surfaces than on the forest floor, and 11 species were collected more frequently on wood surfaces. 3,Spiders utilized DWM at different stages in their development. Female Pardosa mackenziana (Keyserling) (Lycosidae) carrying egg sacs were caught most often on the surface of DWM, possibly to sun their egg sacs. Additionally, the proportion of immature spiders was higher on the wood surface than on the forest floor. 4,Spiders collected on logs with and without bark were compared to assemblages collected on telephone poles to assess what features of DWM habitat may be important. Web-building species were seldom collected on telephone poles, suggesting that they depend on the greater habitat complexity provided by DWM. In contrast, hunting spiders did not distinguish between telephone poles and logs. 5,Fewer spiders and a less diverse fauna utilized elevated compared to ground-level wood. Additionally, Detrended Correspondence Analysis revealed that the spider community from elevated wood was distinguishable from the spider community from ground-level wood, and from the forest floor spider community. [source]

Effects of predation and habitat structure on the population dynamics of house mice in large outdoor enclosures

OIKOS, Issue 3 2005
Anthony D. Arthur
This paper examines the effect of different levels of protection from predation on feral house mice. Mice were contained in eight 50×50 m outdoor enclosures. Enclosures allowed access to a suite of freeliving vertebrate predators from the surrounding area, including feral foxes, feral cats and Australian raptors. A 10,15% cover of small, felled cypress pine trees was added in strips to low grassland to increase habitat complexity. Mice were not protected from predation when compared with low grassland pens, possibly because predators were able to focus their hunting activity in the strips. However, when felled trees were covered with wire netting, hence providing higher quality refuge, mouse populations achieved higher densities than in low grassland pens. A predator exclusion treatment was used to confirm the refuge effect was due to a reduction in the impact of predation. Survival rates under the different treatments were generally consistent with population level responses, with mice having lower survival in low grassland pens than in high refuge pens. This is the first study with mammals that confirms the importance of refuges from predators for prey populations. [source]