State‐space modeling reveals habitat perception of a small terrestrial mammal in a fragmented landscape

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Movement patterns,home range size and habitat utilization of the bluespine unicornfish, <Emphasis Type="BoldItalic">Naso unicornis</Emphasis> (Acanthuridae) in a Hawaiian marine reserve

Synopsis We quantified bluespine unicornfish, Naso unicornis, movement patterns, home range size and habitat preferences in a small Hawaiian marine reserve. Bluespine unicornfish were site-attached to home ranges situated within the reserve boundaries and their movements were aligned with topographic features. Two different diel movement patterns (‘commuting’ and ‘foraying’) were observed. Commuters made crepuscular migrations of several hundred meters between daytime foraging areas and nighttime refuge holes. Foraying fish did not partake in crepuscular migrations and utilized refuge holes both day and night. Two bluespine unicornfish were also nocturnally active. There was little direct evidence of dispersal from the reserve but differences in bluespine unicornfish abundance and size among reef habitat zones were consistent with ontogenetic habitat shifts. The influence of habitat topography on bluespine unicornfish movements suggests that gross habitat characteristics could be used to predict reef fish movements. This could provide a simple method for setting marine reserve boundaries at sites for which empirical fish movement data are unavailable.     

Movements of the flying squirrel Pteromys volans in corridors and in matrix habitat

Elements of the landscape, such as patches of preferred habitat, matrix between patches, and corridors linking patches, differ as movement habitat for animals. To understand how landscape structure influences the movement and thus, population dynamics of animals, clear empirical knowledge on patterns of movement is needed. The Siberian flying squirrel inhabits spruce-dominated boreal forests from Finland to eastern Siberia. Numbers of flying squirrels have declined severely in Finland in past decades, probably due to modern forestry. We studied the movement of radio-collared adult flying squirrels in preferred (spruce forest) and in matrix habitat (open areas and other habitats with trees) in Finland 1997–2000, and determined whether the woodland strips connecting patches of preferred habitat could function as ecological corridors for flying squirrels.
Flying squirrels used woodland strips for inter-patch movements, but also used matrix with trees and were able to cross narrow open gaps. Males moved longer total distances and crossed edges more often than females. Males used matrix habitats for movement between spruce patches, and moved faster and more directly in the matrix than in the spruce forest. Females seldom changed spruce patches, but instead used the matrix for foraging. For both sexes probability of leaving the spruce forest patch correlated negatively with the size of the patch, but the type of connection the patch had to other patches did not affect the leaving probability. Due to efficient movement abilities of the flying squirrel and forest-dominated landscape structure of southern Finland, we suggest that conservation acts for maintaining viable populations of flying squirrels should focus on the quality of managed forest and the area of suitable breeding habitat (i.e. on habitat loss), but not necessarily on ecological corridors.     

Within-tree distribution of nest sites and foraging areas of ants on canopy trees in a tropical rainforest in Borneo

It has been argued that canopy trees in tropical rainforests harbor species-rich ant assemblages; however, how ants partition the space on trees has not been adequately elucidated. Therefore, we investigated within-tree distributions of nest sites and foraging areas of individual ant colonies on canopy trees in a tropical lowland rainforest in Southeast Asia. The species diversity and colony abundance of ants were both significantly greater in crowns than on trunks. The concentration of ant species and colonies in the tree crown seemed to be associated with greater variation in nest cavity type in the crown, compared to the trunk. For ants nesting on canopy trees, the numbers of colonies and species were both higher for ants foraging only during the daytime than for those foraging at night. Similarly, for ants foraging on canopy trees, both values were higher for ants foraging only during the daytime than for those foraging at night. For most ant colonies nesting on canopy trees, foraging areas were limited to nearby nests and within the same type of microhabitat (within-tree position). All ants foraging on canopy trees in the daytime nested on canopy trees, whereas some ants foraging on the canopy trees at night nested on the ground. These results suggest that spatial partitioning by ant assemblages on canopy trees in tropical rainforests is affected by microenvironmental heterogeneity generated by three-dimensional structures (e.g., trees, epiphytes, lianas, and aerial soils) in the crowns of canopy trees. Furthermore, ant diversity appears to be enriched by both temporal (diel) and fine-scale spatial partitioning of foraging activity.     

Wintering forest birds roost in areas of higher sun radiation

We analyze environmental determinants of roost site selection by tree gleaning passerines wintering in a Mediterranean montane oakwood at a craggy area of high variation in altitude and hill-shading pattern. We hypothesize that in temperate latitudes of cold winter climate, birds should spend the night in areas of low altitudes, higher temperatures, and higher solar radiation in order to minimize thermoregulation costs during resting time and to improve foraging conditions just before and after roosting. We study night occupation of woodland locations by the presence of feces in 159 wooden nest boxes (i.e., under identical controlled roosting situations). We employ GIS methods to quantify solar radiation at each location surrounding the nest boxes and data loggers to measure air temperature in the field. Birds prefer to roost in forest patches with higher solar radiation, where the period of light available for foraging is extended and thermoregulation costs during daytime are minimized. They also selected woodland patches with taller trees, a pattern consistent with their foraging preferences for trunks and branches. Other environmental variables played a negligible role in determining the selection of roost sites. Here, we show, for the first time, the importance of sun radiation determining where to spend the night in wintering birds and call attention on considering the thermal space in forest management. Forest management should preserve woodland patches with taller trees more exposed to solar radiation to enhance winter habitat suitability for birds in these Mediterranean oakwoods.     

The invasive Yellow Crazy Ant and the decline of forest ant diversity in Indonesian cacao agroforests

Throughout the tropics, agroforests are often the only remaining habitat with a considerable tree cover. Agroforestry systems can support high numbers of species and are therefore frequently heralded as the future for tropical biodiversity conservation. However, anthropogenic habitat modification can facilitate species invasions that may suppress native fauna. We compared the ant fauna of lower canopy trees in natural rainforest sites with that of cacao trees in agroforests in Central Sulawesi, Indonesia in order to assess the effects of agroforestry on occurrence of the Yellow Crazy Ant Anoplolepis gracilipes, a common invasive species in the area, and its effects on overall ant richness. The agroforests differed in the type of shade-tree composition, tree density, canopy cover, and distance to the village. On average, 43% of the species in agroforests also occurred in the lower canopy of nearby primary forest and the number of forest ant species that occurred on cacao trees was not related to agroforestry characteristics. However, A. gracilipes was the most common non-forest ant species, and forest ant richness decreased significantly with the presence of this species. Our results indicate that agroforestry may have promoted the occurrence of A. gracilipes, possibly because tree management in agroforests negatively affects ant species that depend on trees for nesting and foraging, whereas A. gracilipes is a generalist when it comes to nesting sites and food preference. Thus, agroforestry management that includes the thinning of tree stands can facilitate ant invasions, thereby threatening the potential of cultivated land for the conservation of tropical ant diversity.     

Magellanic woodpecker ( Campephilus magellanicus) abundance and foraging in Tierra del Fuego, Chile

The Magellanic woodpecker (Campephilus magellanicus) is a vulnerable and poorly studied bird in the sub-antarctic deciduous and evergreen beech (Nothofagus) forests of South America. On Tierra del Fuego island (Chile), we compared Magellanic woodpecker abundance and its foraging habitat in two forest types: pure N. pumilio and mixed forests composed by N. pumilio and N. betuloides, including managed and non managed stands. At a regional scale, abundance of woodpeckers was greater in landscapes including both forest types than in pure N. pumilio landscapes. When both forest types occurred together, woodpecker abundance did not differ between them. The number of trees with foraging signs was correlated with Magellanic woodpecker abundance and was also associated with N. betuloides and snag densities, but was not affected by forest management. Occurrence of pecking on foraging trees was greater in mixed Nothofagus than pure N. pumilio stands. Woodpeckers foraged disproportionately more on larger diameter and more decayed trees. Moreover, trees used for foraging were positively correlated with canopy cover and snag density and were negatively correlated with distance to nearby peatlands and beaver ponds. Direct observation revealed that the flying distance between trees was negatively correlated with proportion of trees with foraging signs. Woodpeckers chose trees that were visited before, suggesting a pattern of tree recognition within foraging territories.Communicated by F. Bairlein     

The influence of agricultural system,stand structural complexity and landscape context on foraging birds in oil palm landscapes

Functional diversity, an important element of avian biodiversity, can be examined by quantifying foraging guild composition. Understanding the ecological processes that underpin functional diversity of birds in oil palm Elaeis guineensis landscapes is important because different foraging guilds are likely to be influenced in different ways by land use practices. We surveyed birds at 55 sites within oil palm landscapes and at 20 sites within logged peat swamp forest, recording 208 species belonging to 19 foraging guilds. Oil palm landscapes supported a lower abundance of insectivorous, granivorous and omnivorous birds than did logged peat swamp forest despite the latter being severely degraded due to intensive timber extraction. However, abundances of other groups of foraging birds, such as raptors and wetland taxa, were higher in oil palm landscapes than logged peat swamp forest. Frugivorous species were more abundant in smallholdings than plantation estates, probably because of the presence of native trees. Foraging guild diversity was explained by stand‐level attributes such as stand age, vegetation cover, epiphyte persistence and canopy cover. However, each foraging guild exhibited unique responses to different oil palm management regimes and stand‐level attributes. Only arboreal omnivores and terrestrial frugivores were affected by the proximity of nearby natural forest. This diversity of responses implies that the occurrence of particular avian foraging guilds may not be a suitable ecological indicator of best‐practice palm oil production. Our study also suggests that multiple conservation measures will be needed in oil palm landscapes irrespective of management regimes, including: (1) the maintenance of ground layer vegetation cover; (2) the pruning of oil palm canopy to permit light penetration to the ground layer; (3) re‐vegetation of parts of oil palm landscapes with native trees; and (4) retention of natural and/or secondary forest patches within the boundaries of plantations.     

Influence of within‐patch habitat quality on high‐Andean Polylepis bird abundance

Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations.     

Home‐range size and habitat use of European Nightjars Caprimulgus europaeus nesting in a complex plantation‐forest landscape

In Europe, the consequences of commercial plantation management for birds of conservation concern are poorly understood. The European Nightjar Caprimulgus europaeus is a species of conservation concern across Europe due to population depletion through habitat loss. Pine plantation‐forest is now a key Nightjar nesting habitat, particularly in northwestern Europe, and increased understanding of foraging habitat selection is required. We radiotracked 31 Nightjars in an extensive (185‐km²) complex conifer plantation landscape in 2009 and 2010. Home‐range 95% kernels for females, paired males and unpaired males were an order of magnitude larger than song territories of paired males, emphasizing the importance of habitats beyond the song territory. Nightjars travelled a mean maximum distance of 747 m from the territory centre each night. Home‐range placement relative to landscape composition was examined by compositional analysis. Pre‐closure canopy forest (aged 5–10 years) was selected at all scales (MCP, 95% and 50% kernels), with newly planted forest (aged 0–4 years) also selected within 50% kernels. For telemetry fixes relative to habitat composition within 2 km of their territory centre, individuals again selected pre‐closure and newly planted forest, and also grazed grass heath. Open ungrazed habitat was not selected, with implications for open habitat planning for biodiversity conservation within public‐owned forests. Despite the Nightjars’ selection for younger growth, moth biomass was greater in older forest stands, suggesting that foraging site selection reflects ease of prey capture rather than prey abundance. Within large plantation‐forest landscapes, a variety of growth stages is important for this species and our results suggest that grazing of open habitats within and adjacent to forest will additionally benefit the European Nightjar.     

Forests do not limit bumble bee foraging movements in a montane meadow complex

1. Understanding the roles of habitat fragmentation and resource availability in shaping animal movement are integral for promoting species persistence and conservation. For insects such as bumble bees, their movement patterns affect the survival and reproductive potential of their colonies, as well as the pollen flow of plant species. However, the understanding of their mobility or the impact of putative barriers in natural environments is limited due to the technical difficulties of studying wild populations. 2. Genetic mark–recapture was used to estimate the foraging distance, resource use, and site connectivity of two bumble bee species in a montane meadow complex composed of open meadows within a matrix of forest. 3. There was no evidence that forests or changes in landcover function as barriers to the fine-scale movement for either species. Substantially greater colony-specific foraging distances were found for Bombus vosnesenskii (maximum: 1867 m) compared to Bombus bifarius (maximum: 362 m). Despite this difference in absolute range, both species were detected across putative forest barriers at frequencies expected by uninhibited movement. Siblings separated by greater distances were more likely to be foraging on different floral species, potentially suggesting a resource-based motivation for movement. 4. These results suggest that bumble bee foraging patterns are influenced by species-specific differences in movement capacity, with little influence of matrix composition between resource patches. They also support the perspective that habitat conservation for bumble bees should prioritise providing abundant and diverse patches of resources within species-specific movement radii with less emphasis on matrix composition.     

Roosting Requirements of Two Frugivorous Bats (Sturnira lilium and Arbiteus intermedius) in Fragmented Neotropical Forest1

As tropical forest fragmentation accelerates, scientists are concerned with the loss of species, particularly those that play important ecological roles. Because bats play a vital role as the primary seed dispersers in cleared areas, maintaining healthy bat populations is critical to natural forest regeneration. Observations of foraging bats suggest that many Neotropical fruit‐eating species have fairly general habitat requirements and can forage in many different kinds of disturbed vegetation; however, their roosting requirements may be quite different. To test whether or not general foraging requirements are matched by equally broad roosting requirements, we used radiotelemetry to locate roost sites of two common frugivorous bat species (Sturnira lilium and Artibeus intermedius) in a fragmented forest in southeastern Mexico. Sturnira lilium roosted inside tree cavities and selected large‐diameter roost trees in remnant patches of mature forest. Fewer than 2 percent of trees surveyed had a mean diameter equal to or greater than roost trees used by . S. lilium, Artibeus intermedius roosted externally on branches and vines and under palm leaves and selected roost trees of much smaller diameter. Compared to random trees, roost trees chosen by A. intermedius were closer to neighboring taller trees and also closer in height to these trees. Such trees likely provide cryptic roosts beneath multiple overlapping crowns, with sufficient shelter from predators and the elements. While males of A. intermedius generally roosted alone in small trees within secondary forest, females roosted in small groups in larger trees within mature forest and commuted more than three times farther than males to reach their roost sites. Loss of mature forest could impair the ability of frugivorous bats to locate suitable roost sites. This could have a negative impact on bat populations, which in turn could decrease forest regeneration in impacted areas.     

Ant assemblages in isolated trees are more sensitive to species loss and replacement than their woodland counterparts

Isolated trees possess an arthropod assemblage different to that found in woodland trees. While isolated trees become an increasingly dominant part of many landscapes, with ‘off reserve’ habitat conservation potential, we know little about the drivers of their assemblage structure. While sampling bimonthly for 12 months in the seasonally dry tropics of Mexico, we characterized the ant species most likely to occupy isolated trees in comparison to small woody patches (‘matorral’; 0.13–0.74 ha), and examined the influence of environmental variables on the respective ant assemblages at both canopy and ground level. Isolated trees possessed a predictable ant assemblage: when compared to the woodland patches, isolated trees were characterised by a lack of specialised arboreal species and an increase in generalised terrestrial species reaching the canopy. Arboreal woodland ant species were as affected by tree isolation as the terrestrial woodland ant fauna. Ant assemblages at isolated trees correlated with a series of microenvironmental (microclimate and biophysical) variables, but this was not the case for the ant assemblages in woodlands. This suggests that at very small habitat sizes (e.g., isolated trees), microenvironment influences assemblage composition by favouring more environmentally tolerant or opportunistic species. Although we were unable to identify alternative variables (e.g., patch area, connectivity) which correlated with assemblage composition in larger habitat patches, it appears that in such patches, local microenvironment is less closely associated with assemblage structure, and variables such as patch and landscape configuration become increasingly important. In a practical sense, micro-habitat restoration aimed at augmentation of vegetation surrounding isolated trees may therefore be an effective means of increasing matrix habitat quality and increasing the partitioning of the arboreal and terrestrial faunas, thereby conserving a broader range of species. More generally, movement of matrix species into habitat patches appears to apply universally over a range of scales and taxa, and provides a distinct contrast to the predictions based on the Theory of Island Biogeography.     

Nest site selection in middle and great spotted woodpeckers <Emphasis Type="Italic">Dendrocopos medius</Emphasis> &; <Emphasis Type="Italic">D. major</Emphasis>: implications for forest management and conservation

Success of species conservation depends to a large extent on comprehensive management that considers all critical aspects of a species’ niche. Many studies have examined habitat factors in relation to occurrence, abundance or foraging behaviour of European woodpecker species, while relatively little is known about nest site selection. I compared habitat structures used for nesting by middle and great spotted woodpeckers Dendrocopos medius and D. major with available structures in an oak forest in the Swiss lowlands. I first tested if nest trees were randomly selected among available trees by focusing on species, condition and diameter of nest trees, and on the presence of the fruiting body (hereafter sporophore) of polypores (wood-decomposing fungi). Second, I examined if the nesting niches of the two species were differentiated. Both species showed strong preferences for oaks, large trees, dead trees and for trees with sporophores. Nest sites of the two species differed most strongly with respect to the presence of sporophores, cavity age and tree condition, pointing towards interspecific competition for nest sites. Old living or dead trees with sporophores are central components of the nesting niche of middle and great spotted woodpeckers. Conservation plans for the threatened middle spotted woodpecker have so far mostly focused on the needs in terms of distribution and foraging; future conservation strategies and forest management must take into account the preference for dead and decaying trees with sporophores as another vital resource. This will also provide benefits for other woodpecker species as well as for the community of secondary cavity nesters.     

Chainsawing for conservation: Ecologically informed tree removal for habitat management

Summary In many ecosystems, increases in vegetation density and the resulting closure of forest canopies are threatening the viability of species that depend upon open, sunlight‐exposed habitats. Consequently, we need to develop management strategies that recreate open habitats while minimizing the impacts on non‐target areas. Selective logging creates canopy gaps, but may result in undesirable effects in other respects. Thus, chainsaws have not been a popular tool for conservation. We conducted a landscape‐scale experiment to test whether selective tree removal can restore patch‐level habitat quality for Australia’s most endangered snake (Hoplocephalus bungaroides) and its main prey (the lizard Oedura lesueurii). We selectively removed canopy trees surrounding 25 overgrown rock outcrops and compared the resultant habitat structure and abiotic conditions to 30 overgrown, shady outcrops and 20 open, sunny outcrops. Removing vegetation decreased canopy cover by 19% in experimental plots and increased incident radiation and thermal regimes. These changes increased the availability of suitable shelter sites for our target species by 131%. At the landscape scale, our manipulations had a trivial effect on forest habitat; by increasing the area of sun‐exposed outcrops, we decreased forest cover by <0.1%. Our results show that targeted canopy removal can increase the availability of sun‐exposed habitat patches for endangered species in biologically meaningful ways. Thus, selective tree felling may be an effective conservation tool for open‐habitat specialists threatened by vegetation overgrowth.     

Microhabitat associations of terrestrial insectivorous birds in Amazonian rainforest and second‐growth forests

ABSTRACT Across the Neotropics, small‐bodied terrestrial insectivores are sensitive to forest fragmentation and are largely absent from second‐growth forests. Despite their sensitivity to forest structure, the microhabitat relationships of these birds have not been quantified. From July 1994 to January 1995 in central Amazonia, we characterized habitat at sites where nine species of terrestrial insectivores were observed foraging, as well as at randomly selected sites in continuous forest and two types of 10–15‐yr‐old second‐growth forest common in Amazonia (Vismia‐ and Cecropia‐dominated). We used factor analysis to find suites of correlated variables. From each factor, we selected a representative variable that was relatively easy to measure. We used Bayesian analysis to estimate means and standard deviations of these variables for each species and for each type of habitat. All nine focal species were associated with ranges of microhabitat variables, such as leaf litter depth and tree densities, often absent in second‐growth forests. At least in the early stages of regeneration, neither type of second‐growth forest provides suitable structure for the terrestrial insectivores in our study. The large leaves of Cecropia trees that make up the thick leaf litter may preclude the use of Cecropia‐dominated second growth by our focal species, many of which manipulate leaves when foraging. The leaf litter in Vismia‐dominated second growth was also thicker than sites used for foraging by our focal species. In addition, Vismia‐dominated growth had more small trees and small nonwoody vegetation, perhaps impeding movement by terrestrial birds. In continuous forest, our focal species foraged in microhabitats with characteristics that generally overlapped those of randomly selected sites. Thus, our results are consistent with the hypothesis that microhabitat differences make second‐growth forests unsuitable for our focal species.     

Effects of habitat type and trap placement on captures of bark (Coleoptera: Scolytidae) and longhorned (Coleoptera: Cerambycidae) beetles in semiochemical-baited traps

Two studies were conducted to determine the effect of habitat selection and trap placement on catches of Scolytidae and Cerambycidae (Coleoptera) in northeastern U.S. forests. In a nonreplicated case study, four habitat types--closed canopy hardwood stand, closed canopy conifer stand, a low-intensity thinned Pinus strobus L. stand, and a high-intensity thinned P. strobus stand--were surveyed using alpha-pinene, ethanol, ipsenol, ipsdienol, and lanierone. Average trap catches, species richness, and the number of unique species captured were all highest in at least one of the thinned habitats. A second experiment that was replicated evaluated the placement of traps in relation to habitat patches. Semiochemical-baited traps (alpha-pinene and ethanol) were placed under a closed canopy forest, along an edge, and in a clearing and tested for effects on Scolytidae and Cerambycidae trap catches. Abundance and species richness were generally higher in the closed canopy and edge placements compared with traps in the open area. The highest number of unique species were captured in the edge and clearing.     

Habitat-dependent thermal regimes of two hawaiian geckos (Reptilla: gekkonidae)

1. 1.Effects of habitat on the thermal regime were investigated in two diurno—nocturnal geckos in Hawaii.

2. 2.In trees Hemidactylus frenatus thermoregulated in daytime with body temperature (BT) above air temperture (AT); in houses some thermoregulated likewise in daytime but mainly the species thermoregulated at night, on electric lamps, to the same BT as in trees by day.

3. 3.Lepidodactylus lugubris in trees thermoregulated in daytime, its BT lower than in H. frenatus. In the rocks it had at night a BT resembling that in trees in daytime, because the thermal cycle in rock crevices lagged behind outside AT.

4. 4.The flexibility of these geckos in thermal regime and activity cycle preadapts them to both migration and invasion of houses.

Evaluating Residual Tree Patches as Stepping Stones and Short-Term Refugia for Red-Legged Frogs

Abstract: Temperate pond-breeding amphibians are vulnerable to forest fragmentation because they must access upland terrestrial sites during the nonbreeding season but are prone to desiccation in hot, dry environments without canopy cover. Harvesting techniques that retain live trees in the cut block are advocated for sustaining forest biodiversity, but the effects of these practices on amphibians are unknown. We studied red-legged frogs (Rana aurora) in movement trials to assess: 1) how short-term use of residual trees was affected by tree patch size, streams, and neighborhood features; 2) whether residual tree patches were used as stepping stones in negotiating cut blocks; 3) the effects of patch size and patch proximity in altering movement paths; and 4) the effects of retention level and patch size on interpatch distance. Residual tree patches were potentially valuable short-term refugia but their value was size dependent. Virtually all frogs released at the base of single trees or inside small tree clusters left within 72 hours, but the proportion leaving decreased curvilinearly with increasing patch size. Frogs were less likely to leave tree patches with a running stream or where neighborhood stream density was high. Residual tree patches did not systematically alter movement paths. Frogs intercepted residual tree patches mostly at random and had to be within 5-20 m of a tree patch before moving to it in greater proportions than expected by chance. However, amphibian movements were biased toward large (0.8 ha) patches and away from small (0.3 ha) patches 50 m away. Our results indicated that residual trees should not be retained singly but should be aggregated in groups between 0.8 ha and 1.5 ha, preferably in stream locations.