Choice of nest site protects army ant colonies from environmental extremes in tropical montane forest

Unlike most social insects, Eciton burchellii army ants cannot thermoregulate through nest construction. Instead, army ants thermoregulate behaviorally by creating a living nest (bivouac), shifting its position and structure, and potentially through nest site selection. We hypothesized that bivouac site selection is critical to E. burchellii colony survival. We predicted elevation above sea level, with associated variation in local abiotic environments, would affect bivouac site selection by E. burchellii colonies. We also expected nest sites to buffer against ambient variation in abiotic conditions. We recorded bivouac site choice by E. burchellii colonies at sites ranging from lowland wet forests to montane forests and reviewed previously published data. We measured microclimatic variables associated with nest sites in high-elevation montane forests: temperature, relative humidity, and light levels. Bivouac site selection varied with elevation: as elevation increased, fewer bivouac sites were exposed, more were underground, and fewer were elevated (in trees). High-elevation bivouac sites moderated diurnal temperature variation and had higher relative humidity levels and lower light levels than ambient conditions. The buffering of ambient temperature and humidity decreased with elevation in montane forests, suggesting that abiotic extremes in bivouac sites at the highest elevations may contribute to the upper elevational range limits of E. burchellii.     

The role of geography and ecology in shaping the phylogeography of the speckled hummingbird (Adelomyia melanogenys) in Ecuador

The Andes of South America contain one of the richest avifaunas in the world, but little is known about how this diversity arises and is maintained. Variation in mitochondrial DNA and morphology within the speckled hummingbird (Adelomyia melanogenys) was used to elucidate the phylogeographic pattern along an Ecuadorian elevational gradient, from the coastal cordillera to the inland Andean montane region. We examined sequence, climatic/remote sensing and morphological data to understand the effects of topography and ecology on patterns of variation. Populations on either side of the Andes are genetically divergent and were separated during a period that corresponds to the final stages of Andean uplift during the Pliocene. Despite isolation, these two populations were found to be morphologically similar suggesting a strong effect of stabilizing selection across ecologically similar Andean cloud forests, as assessed using climatic and remote sensing data. In contrast, little genetic divergence was found between coastal and west-Andean individuals, suggesting recent interruption of gene flow between these localities. However, coastal populations were found to inhabit different habitats compared to Andean populations as shown by climatic and remote sensing variables. Furthermore, coastal individuals had significantly longer bills compared to their montane relatives, indicative of differential directional selection and the influence of habitat differences in shaping phenotypic variation. Results highlight the role of both isolation and ecology in diversification in Ecuadorian montane regions, while suggesting the two may not always act in concert to produce divergence in adaptive traits.     

The DNA history of a lonely oak: Quercus humboldtii phylogeography in the Colombian Andes

The climatic and geological changes that occurred during the Quaternary, particularly the fluctuations during the glacial and interglacial periods of the Pleistocene, shaped the population demography and geographic distribution of many species. These processes have been studied in several groups of organisms in the Northern Hemisphere, but their influence on the evolution of Neotropical montane species and ecosystems remains unclear. This study contributes to the understanding of the effect of climatic fluctuations during the late Pleistocene on the evolution of Andean mountain forests. First, we describe the nuclear and plastidic DNA patterns of genetic diversity, structure, historical demography, and landscape connectivity of Quercus humboldtii, which is a typical species in northern Andean montane forests. Then, these patterns were compared with the palynological and evolutionary hypotheses postulated for montane forests of the Colombian Andes under climatic fluctuation scenarios during the Quaternary. Our results indicated that populations of Q. humboldtii have high genetic diversity and a lack of genetic structure and that they have experienced a historical increase in connectivity from the last glacial maximum (LGM) to the present. Furthermore, our results showed a dramatic reduction in the effective population size followed by an expansion before the LGM, which is consistent with the results found by palynological studies, suggesting a change in dominance in Andean forests that may be related to ecological factors rather than climate change.     

Ecoregional distribution of potentially useful species of Araceae and Bromeliaceae as non-timber forest products in Bolivia

In Bolivia, the plant families Araceae and Bromeliaceae offer numerous non-timber products, including ornamental plants, medicines, foods, and fibers. The economic potential for the utilization of these resources depends critically on the distribution of potentially useful species in different ecoregions in Bolivia. We conducted both a bibliographical revision of uses and ecological field work at 43 sites in the Bolivian Andes and lowlands to assess the potential for sustainable use as suggested by the Rapid Vulnerability Assessment method. The ecological criteria used for the evaluation were abundance (frequency), life form, geographical distribution, and habitat preference. We found that Bolivia has a striking number of potentially useful species of both families but that their potential use differs among ecoregions. Araceae were most species-rich and frequent in the humid lowland and montane forests. In these ecoregions, this family has a particular local importance mainly as traditional medicines and a great potential as ornamental plants. In contrast, economically useful bromeliads are best represented in seasonally dry forest habitats, especially for the production of fibres. Many species of bromeliads, which also occur in humid montane forests, although rare, are potentially important for commercialisation as ornamental species. This study shows that the uses of Araceae and Bromeliaceae are manifold and could be greatly increased through efficient management, although with different strategies according to the different ecoregions.     

Experimental transplants reveal strong environmental effects on the growth of non‐vascular epiphytes in Afromontane forests

Transplant studies can provide valuable information on the growth responses of epiphytic bryophytes and lichens to environmental factors. We studied the growth of six epiphyte species at three sites in moist Afromontane forests of Taita Hills, Kenya. With 558 pendant transplants, we documented the growth of four bryophytes and two lichens over 1 yr. The transplants were placed into the lower canopy of one forest site in an upper montane zone, and two forest sites in a lower montane zone. Several pendant moss species grew very well in the cool and humid environment of the upper montane forest, with some transplants more than doubling their biomass during the year. Conversely, all transplanted taxa performed poorly in the lower montane zone, presumably because of the unfavorable combination of ample moisture with excessive warmth and insufficient light which characterizes the lower canopy in dense lower montane forests. The results demonstrate that pendant transplants can be used for monitoring growth of non‐vascular epiphytes in tropical forests. The starting weight of 0.25 g for pendant transplants worked well and can be recommended for future studies.     

History meets ecology: a geographical analysis of ecological restriction in the Neotropical humid montane forests avifaunas

Aim To analyse the ecological patterns of distribution of the avifaunas of the Neotropical humid montane forests, by assessing the degree of habitat restriction among species through the calculation of a numerical index, analysing their relationships with adjacent habitat, and exploring the relative contribution of both higher and lower habitats in shaping the avian assemblages. Location The Neotropical humid montane forests, from Mexico to north‐western Argentina. Methods The degree of species’ restriction to the habitat was calculated through a restriction index based on published endemicity indexes. The index scores range from 0 to 1: a score of 1 indicates a totally endemic species (i.e. fully restricted to the habitat); values tending to 0 indicate a widespread species. Results In Mesoamerica, completely restricted species represent a lower proportion of the total avifauna than in South American humid montane forests; whereas species shared to other habitats showed a higher proportion of the avifauna with affinities to higher altitude forests (e.g. pine and pine‐oak forests). South America, on the other hand, holds assemblages with a high proportion of completely restricted species; species shared to other habitats showed a high proportion of taxa with affinities to lowland forests. Main conclusions The ecological distribution of the HMF's avifauna could be partitioned in three main components: the ecologically restricted avifauna, the high altitude species and, the lower altitude species, which are tightly associated to the floristic composition along the gradient. The history of formation of the HMF flora and the ecological distribution of different avian taxa suggest a common history. Finally, the restriction index allowed a detailed evaluation of the composition of avian assemblages, their degree of restriction to the habitat and of the affinities regarding adjacent habitats, as well as an accurate distinction between species richness and restricted species richness, which should be a fundamental step towards the establishment of conservation priorities.     

Comparative avian biodiversity of five mountains in northern Cameroon and Bioko

Larison, B., Smith, T.B., Fotso, R. & McNiven, D. 2000. Comparative avian biodiversity of five mountains in northem Cameroon and Bioko. Ostrich 71 (1 & 2): 269–276.

Endemism among birds is widespread in the montane forests of western Cameroon and the Gulf of Guinea. The region includes some of the rarest and most threatened species in Africa. We conducted avian surveys of four previously unsurveyed montane sites in northern Cameroon, including Mt. Ngang-Ha, Hoséré Vokré, Tchabal Gandaba, and Tchabal Mbabo, as well as the northern slope of Caldera de Luba on the island of Bioko, Equatorial Guinea. We report here on avian species richness and relative abundance, and evaluate the conservation potential of each site based on avifaunal richness. The montane forest on both Tchabal Mbabo and Caldera de Luba is extensive, while on the other mountains, the vegetation is not characteristic of montane forest, and consists primarily of small gallery forests embedded in savanna. Tchabal Mbabo and Caldera de Luba had the greatest species richness and abundance of montane birds, while Tchabal Gandaba had the greatest overall avian species richness and abundance. Few montane species were noted on Mt. Ngang-Ha and Hosere Vokre, and avian abundance was quite low on both mountains. Of the mountains surveyed, Tchabal Mbabo and Caldera de Luba exhibit the greatest potential for conservation based on extent of montane forest, and montane species richness and abundance.     

Forest communities of the northern whitefish range, rocky mountains, Montana, U.S.A.

The montane and subalpine forests of a mountain range in northwestern Montana were investigated using phytosociological and numerical methods. Twelve associations and two subassociations were identified, of which eight are described here for the first time. The forest vegetation of valleys and lower slopes is strongly affected by repeated fire and is placed in the new orderCalamagrostio-Pseudotsugetalia glaucae, which includes temperate, low elevation forests in inland regions of northwestern North America. These forests bear only weak resemblance to forests traditionally assigned to the classVaccinio-Piceetea, and occupy the habitats filled by broad-leaved forests elsewhere at temperate latitudes. Montane and subalpine forest vegetation is moister and has longer snow duration and a shorter growing season. Upper montane vegetation more closely resembles that of other temperate montane forests of the classVaccinio-Piceetea.     

Phosphorus Fertilization Increases the Abundance and Nitrogenase Activity of the Cyanolichen Pseudocyphellaria crocata in Hawaiian Montane Forests

Nitrogen-fixing epiphytes (especially lichens with a cyanobacterial symbiont—cyanolichens) have the potential to contribute significant amounts of nitrogen (N) to montane tropical forests, which are typically low in N—but the factors controlling the abundance and distribution of epiphytic cyanolichens are poorly understood. In long-term fertilization experiments in montane forests on a 4.l million-yr-old Oxisol on the island of Kauà'i and on a 152-yr-old lava flow on the island of Hawai'i, the epiphytic cyanolichen Pseudocyphellaria crocata increased significantly in abundance in canopies of host trees fertilized with phosphorus (P). There was no response to fertilization with N or other essential elements. Nitrogen-fixation rates were also elevated in lichens in P-fertilized plots at both sites. Phosphorus supply to host trees may be an important factor controlling N inputs to montane tropical forests by N-fixing epiphytes.     

Seeing the wood despite the trees: Exploring human disturbance impact on plant diversity,community structure,and standing biomass in fragmented high Andean forests

High Andean forests harbor a remarkably high biodiversity and play a key role in providing vital ecosystem services for neighboring cities and settlements. However, they are among the most fragmented and threatened ecosystems in the neotropics. To preserve their unique biodiversity, a deeper understanding of the effects of anthropogenic perturbations on them is urgently needed. Here, we characterized the plant communities of high Andean forest remnants in the hinterland of Bogotá in 32 0.04 ha plots. We assessed the woody vegetation and sampled the understory and epiphytic cover. We gathered data on compositional and structural parameters and compiled a broad array of variables related to anthropogenic disturbance, ranging from local to landscape‐wide metrics. We also assessed phylogenetic diversity and functional diversity. We employed nonmetric multidimensional scaling (NMDS) to select meaningful variables in a first step of the analysis. Then, we performed partial redundancy analysis (pRDA) and generalized linear models (GLMs) in order to test how selected environmental and anthropogenic variables are affecting the composition, diversity, and aboveground biomass of these forests. Identified woody vegetation and understory layer communities were characterized by differences in elevation, temperature, and relative humidity, but were also related to different levels of human influence. We found that the increase of human‐related disturbance resulted in less phylogenetic diversity and in the phylogenetic clustering of the woody vegetation and in lower aboveground biomass (AGB) values. As to the understory, disturbance was associated with a higher diversity, jointly with a higher phylogenetic dispersion. The most relevant disturbance predictors identified here were as follows: edge effect, proximity of cattle, minimum fragment age, and median patch size. Interestingly, AGB was efficiently predicted by the proportion of late successional species. We therefore recommend the use of AGB and abundance of late successional species as indicators of human disturbance on high Andean forests.     

Nontimber Forest Product Use in Two Human Populations from Northwest Patagonia: A Quantitative Approach

The ancestral tradition of gathering nontimber products in the Andean forests of Patagonia seems to be on the verge of disappearing. Edible wild plant knowledge and differential patterns of use have been compared in two populations of different economic and cultural backgrounds—a small rural Mapuche community (Rams), and an outlying population (El Frutillar). The first is located in an herbaceous steppe far from the nearest Andean forest while the second is located outside the town of Bariloche, near the forests of Nahuel Huapi National Park. Semistructured interviews and related ecological variables were compared in both communities. In the past, both communities utilized nontimber forest products from the Andean Temperate forests. However, today, cost and benefit trade-offs appear to affect when and what edible resources are collected. The people from El Frutillar gather fewer wild plants in spite of the high plant abundance and the notorious food scarcity they suffer. The Mapuche people use more nutritious resources, more native species, spend longer traveling to the gathering site, and longer handling time preparing edible plants.     

History of the montane forests of the northern Andes

From the vascular plant genera of the tropical Andean montane forests about 65% have a tropical-neotropical, 15% tropical-Andean, 5% amphi-pacific (Malayo-American), 5% Austral-antarctic and 10% Holarctic distribution. The explosive evolution of Andean centred taxa probably started in the lower Tertiary from tropical Gondwana stock, when in the area of the present day Andes, locally there may have been hills up to 1 000m. With the final upheaval between the Late Miocene and Late Pliocene, extensive areas with a montane climate were created and populated from the low mountain flora by evolutionary radiation. Taxa of Austral-antarctic origin migrated along the Andean chain to the tropics. At the same time the formation of the Panama isthmus connected N. and S. America, and enabled many plants to enter the tropical Andes from the north. First to cross were tropical to subtropical and warm-temperate species from the Tertiary Laurasian flora that had migrated southward during the period of Miocene cooling, taking refuge in the montane tropics. Because the same happened in SE. Asia there is a good number of amphi-pacific taxa known as fossils from Tertiary Laurasia but largely extinct in the present-day Holarctic (e.g.,Trigonobalanus). Later to cross were cool-temperate to cold elements that still exist in the Holarctic (e.g.,Alnus andQuercus).     

滇南勐宋热带山地雨林的物种多样性与生态学特征

 研究了鲜为人知的滇南勐宋地区的原始山地雨林植被, 根据分布生境、群落结构和种类组成特征,可将该山地雨林区分为沟谷和山坡两个类型, 分别定义为八蕊单室茱萸(Mastixia euonymoides)-大萼楠(Phoebe megacalyx)林和云南拟单性木兰(Parachmeria yunnanensis)-云南裸花(Gymnanthes remota)林。该山地雨林的外貌仍以单叶、革质、全缘、中叶为主的常绿中、小高位芽植物组成为特征,层间木质藤本植物仍较丰富,草本高位芽植物和附生植物丰富,但板根和茎花现象少见,属于热带山地垂直带上低山雨林或山地雨林植被类型。与该地区的典型热带季节雨林和赤道热带雨林相比, 勐宋的山地雨林群落中的大、中高位芽植物和藤本高位芽植物比例相对减少, 小、矮高位芽植物和草本高位芽植物比例相对增加,单叶、革质、非全缘叶和小叶比例相对增加,板根现象少见。与中国热带北缘-南亚热带地区（季风）常绿阔叶林比较, 勐宋的山地雨林有较多的附生植物和草本高位芽植物,相对较少的小高位芽植物和矮高位芽植物,小叶比例亦较少,非全缘叶和革质叶比例相对较低。故勐宋山地雨林是滇南热带北缘山地的一种较湿润生境的植被类型, 与所谓的季风常绿阔叶林不同。在物种多样性上,勐宋热带山地雨林在单位面积植物种数上并不比该地区的热带季节雨林低, 物种多样性指数与低丘季节雨林相当,比沟谷季节雨林低, 明显高于季风常绿阔叶林。     

Andean bear Tremarctos ornatus natural history and conservation

• 1 A wealth of information has been generated for the Andean bear Tremarctos ornatus during the past four decades, and a thorough review of the species' natural history, ecology and conservation is provided here.
• 2 The Andean bear is the only remaining bear species in South America. Evolutionarily, it is the youngest of all ursids and the only remnant taxon within the subfamily Tremarctinae. The species is distributed throughout the Andes mountain range from Venezuela to Bolivia, but the limits of its current and past range are uncertain.
• 3 The species is polyestrous, capable of delayed implantation and a facultative seasonal breeder. Genetic information is scarce, and species‐specific markers need to be developed for a more appropriate assessment of the genetic structure of wild populations.
• 4 Andean bears inhabit a wide variety of habitats across the Andes including different forest types and high‐elevation grasslands. They are omnivorous with a frugivorous/folivorous emphasis that is reflected by adaptations of the typical tremarctine mandible.
• 5 Andean bears are vulnerable to extinction due to land conversion and poaching. Efforts have been made to protect them, but threats have not been reduced significantly. Therefore, the species is expected to move faster towards extinction than any other carnivore in the region.

     

Shifts in leaf litter breakdown along a forest–pasture–urban gradient in Andean streams

Tropical montane ecosystems of the Andes are critically threatened by a rapid land‐use change which can potentially affect stream variables, aquatic communities, and ecosystem processes such as leaf litter breakdown. However, these effects have not been sufficiently investigated in the Andean region and at high altitude locations in general. Here, we studied the influence of land use (forest–pasture–urban) on stream physico‐chemical variables (e.g., water temperature, nutrient concentration, and pH), aquatic communities (macroinvertebrates and aquatic fungi) and leaf litter breakdown rates in Andean streams (southern Ecuador), and how variation in those stream physico‐chemical variables affect macroinvertebrates and fungi related to leaf litter breakdown. We found that pH, water temperature, and nutrient concentration increased along the land‐use gradient. Macroinvertebrate communities were significantly different between land uses. Shredder richness and abundance were lower in pasture than forest sites and totally absent in urban sites, and fungal richness and biomass were higher in forest sites than in pasture and urban sites. Leaf litter breakdown rates became slower as riparian land use changed from natural to anthropogenically disturbed conditions and were largely determined by pH, water temperature, phosphate concentration, fungal activity, and single species of leaf‐shredding invertebrates. Our findings provide evidence that leaf litter breakdown in Andean streams is sensitive to riparian land‐use change, with urban streams being the most affected. In addition, this study highlights the role of fungal biomass and shredder species (Phylloicus; Trichoptera and Anchytarsus; Coleoptera) on leaf litter breakdown in Andean streams and the contribution of aquatic fungi in supporting this ecosystem process when shredders are absent or present low abundance in streams affected by urbanization. Finally, we summarize important implications in terms of managing of native vegetation and riparian buffers to promote ecological integrity and functioning of tropical Andean stream ecosystems.     

Spatial distribution as a measure of conservation needs: an example with Asiatic black bears in south-western China

Aim To create a fine‐scale map of the distribution of Asiatic black bears, identify landscape variables affecting the spatial range of this species and assess population trends using presence–absence data and opinions of local villagers. Location Sichuan Province, south‐western China. Methods We divided the province into 15 × 15 km cells, stratified them by forest cover, elevation and road density and randomly selected 494 cells (21% of province) for surveys. In each cell, we interviewed villagers and ground‐verified their reports of bear presence. We ground‐truthed reports of bear absence by conducting transects for bear sign in the best available habitat. We used logistic regression to identify key variables affecting presence of bears and predict their occurrence in unsampled cells. Results We detected bears in 360 cells (73%). Models correctly predicted bear occurrence in 90.3% of cells where we detected bears and 84.5% of sampled cells where bears were absent. Models predicted 42.7% of Sichuan to be occupied by bears. Bear occurrence was strongly related to forest cover throughout the province. Roads had a negative effect in western region of province. Agricultural lands had a negative effect only when they were distant from forests. Villagers were accurate in their knowledge of bear presence or absence. Interviewed villagers (n = 1816) thought that bears were increasing in 32%, stable in 10%, and decreasing in 58% of cells with bears. Where bear populations were perceived to be declining, villagers identified poaching as the most common cause. Main conclusions Our fine‐scale distribution map can be used for future monitoring and the key landscape factors related to occupancy by bears can be used in management plans for this species. Interviewing local villagers is an efficient and reliable means of assessing distribution, and changes therein, for animals such as bears that often interact with people and leave obvious signs.     

Soil‐based habitat partitioning in understorey palms in lower montane tropical forests

Aim Dispersal assembly and niche assembly are two competing theories proposed to explain the maintenance of species diversity in tropical forests. Dispersal theory emphasizes the role of chance colonization events and distance‐limited seed dispersal in explaining species abundance and distribution, whereas niche theory emphasizes differences among species in requirements for potentially limiting resources. Species distribution patterns in tropical forests often correlate with geology and topography, but tests of the relative importance of dispersal and niche partitioning have been hampered by an inadequate characterization of resource availability. The aim of this study was to explore how soil chemical and physical properties, climate, and geographic distance affect understorey palm communities in lower montane forests. Location Fortuna Forest Reserve, Chiriqui Province, and Palo Seco Forest Reserve, Bocas del Toro Province, in western Panama. Methods Understorey palms and soil nutrient concentrations were surveyed within 10 sites on different soil types across a 13‐km transect. Variation in palm community composition was examined in relation to spatial and environmental variables. Results The 25 understorey palm species recorded in the study were non‐randomly distributed among forests differing in soil nutrient availability. In support of dispersal theory, floristic similarity decreased predictably with increasing geographic distance. However, environmental and soil variables were also correlated with geographic distance. Floristic similarity was also highly associated with a subset of environmental variables. Variation in palm community similarity was most strongly correlated with inorganic nitrogen availability and cation concentration. A subset of soil variables had a stronger relationship with floristic similarity when geographic distance was controlled for than did geographic distance when differences in soils were controlled for. Main conclusions Both dispersal and niche processes affect palm species distribution patterns. Although spatially limited dispersal may influence species distribution patterns, soil‐based habitat associations, particularly with respect to soil nitrogen, cation availability and aluminium concentrations, remain important factors influencing palm community composition at the mesoscale level in this tropical montane forest.     

Environmental and genetic control of insect abundance and herbivory along a forest elevational gradient

Environmental conditions and plant genotype may influence insect herbivory along elevational gradients. Plant damage would decrease with elevation as temperature declines to suboptimal levels for insects. However, host plants at higher elevations may exhibit traits that either reduce or enhance leaf quality to insects, with uncertain net effects on herbivory. We examined folivory, insect abundance and leaf traits along six replicated elevational ranges in Nothofagus pumilio forests of the northern Patagonian Andes, Argentina. We also conducted a reciprocal transplant experiment between low- and high-elevation sites to test the extent of environmental and plant genetic control on insect abundance and folivory. We found that insect abundance, leaf size and specific leaf area decreased, whereas foliar phosphorous content increased, from low-, through mid- to high-elevation sites. Path analysis indicated that changes in both insect abundance and leaf traits were important in reducing folivory with increasing elevation and decreasing mean temperature. At both planting sites, plants from a low-elevation origin experienced higher damage and supported greater insect loads than plants from a high-elevation origin. The differences in leaf damage between sites were twofold larger than those between plant origins, suggesting that local environment was more important than host genotype in explaining folivory patterns. Different folivore guilds exhibited qualitatively similar responses to elevation. Our results suggest an increase in insect folivory on high-elevation N. pumilio forests under future climate warming scenarios. However, in the short-term, folivory increases might be smaller than expected from insect abundance only because at high elevations herbivores would encounter more resistant tree genotypes.     

Evaluation of Bear Rub Surveys to Monitor Grizzly Bear Population Trends

Abstract: Wildlife managers need reliable estimates of population size, trend, and distribution to make informed decisions about how to recover at-risk populations, yet obtaining these estimates is costly and often imprecise. The grizzly bear (Ursus arctos) population in northwestern Montana, USA, has been managed for recovery since being listed under the United States Endangered Species Act in 1975, yet no rigorous data were available to evaluate the program's success. We used encounter data from 379 grizzly bears identified through bear rub surveys to parameterize a series of Pradel model simulations in Program MARK to assess the ability of noninvasive genetic sampling to estimate population growth rates. We evaluated model performance in terms of 1) power to detect gender-specific and population-wide declines in population abundance, 2) precision and relative bias of growth rate estimates, and 3) sampling effort required to achieve 80% power to detect a decline within 10 years. Simulations indicated that ecosystem-wide, annual bear rub surveys would exceed 80% power to detect a 3% annual decline within 6 years. Robust-design models with 2 simulated surveys per year provided precise and unbiased annual estimates of trend, abundance, and apparent survival. Designs incorporating one survey per year require less sampling effort but only yield trend and apparent survival estimates. Our results suggest that systematic, annual bear rub surveys may provide a viable complement or alternative to telemetry-based methods for monitoring trends in grizzly bear populations.