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Cameron W. Barrows Kathleen D. Fleming Michael F. Allen 《The Journal of wildlife management》2011,75(3):682-691
Anthropogenic habitat fragmentation typically precedes conservation planning; maintaining remaining linkages among core habitat areas can thus become a key conservation objective. Identifying linkages for dispersal and ensuring those linkages have long-term protection and management are challenging tasks for wildlife managers. These tasks can be especially daunting for smaller species with low mobility, termed corridor dwellers, which must maintain sustainable populations within corridors. Between May 2007 and June 2009, we collected occurrence locations for a corridor dweller, the Palm Springs pocket mouse (Perognathus longimembris bangsii), from museums, previous research, and our own field sampling. We used those data to model their suitable niche space and then identify suitable linkages between proposed conservation areas. We used a partitioned Mahalanobis D2 statistic to create a spatially explicit niche model describing the distribution of a suitable niche space, and we validated the model statistically, with live trapping and with burrowing owl (Athene cunnicularia) diets. Our model identified soil characteristics, topographic ruggedness, and vegetation as variables delimiting Palm Springs pocket mouse habitat; sand content of the soils was an especially important characteristic. Our historic distribution model identified 120,000–90,000 ha as historically potential Palm Springs pocket mouse habitat; roughly 39% of that has been lost to more recent development. Most of the remaining suitable habitat occurred in the northwestern portion of the valley. We modeled habitat within core reserves as well as within proposed linkages between those reserves as having high similarity to known occupied habitats. Live trapping in areas with high (≥0.95) Habitat Suitability Index (HSI) values resulted in captures at 66% of those locations and, along with burrowing owl diets, refined a qualitative model as to what constituted a suitable Palm Springs pocket mouse corridor. While most corridor analyses have focused on mobile species which may traverse corridors in hours, days, or weeks, linkages for corridor dwellers must include habitat for sustaining multi-generational populations. This requires evaluating whether continuous suitable habitat exists within proposed corridors. Our research demonstrates how niche modeling can provide a landscape-scale view of the distribution of suitable habitat to evaluate conservation objectives for connectivity. © 2011 The Wildlife Society. 相似文献
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Miguel A. Ordeñana Dirk H. Van Vuren John P. Draper 《The Journal of wildlife management》2012,76(8):1712-1717
Vegetation management on levees, especially removal of trees and shrubs, might affect burrowing mammals that are considered threats to levee integrity. We evaluated habitat associations of California ground squirrels (Otospermophilus beecheyi) and Botta's pocket gophers (Thomomys bottae) on levees in the Sacramento Valley to assess the effects of levee vegetation management on these species. Using burrows as an indirect measure of mammal presence, we found that the presence of trees had a negative effect on the occurrence and abundance of ground squirrels on levees, and on the location of their burrowing activities on the levee slope, potentially because visual occlusion caused by tall woody vegetation impedes detection of predators. Similarly, trees had a negative effect on the abundance of pocket gophers on levees and on the location of their burrowing activities on the levee slope, probably because of the effect of tree cover on food availability. The conversion of woodland habitats to grasslands on levees most likely will result in increased occurrence, abundance, or both of ground squirrels and pocket gophers, and thereby increase the potential threat that their burrowing activities pose to levee integrity. © 2012 The Wildlife Society. 相似文献
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Aim In order to understand how ground squirrels ( Spermophilus beecheyi ) may respond to future environmental change, we investigated five biotic and environmental factors potentially responsible for explaining body-size variation in this species across California. We examined the concordance of spatial patterns with temporal body-size change since the last glacial maximum (LGM).
Location California, western North America.
Methods We quantified body size of modern populations of ground squirrels ( n = 81) and used a model-selection approach to determine the best variables (sex, vegetation, number of congeners, temperature and/or precipitation) explaining geographical variation in body size among modern populations. We also quantified body size of one fossil population in northern California ( n = 39) and compared temporal body-size change in S. beecheyi at this location since the LGM with model predictions.
Results Body size of modern populations conformed to Bergmann's rule, with larger individuals in northern (wetter and cooler) portions of California. However, the models suggest that precipitation, rather than temperature or other variables, may best explain variation in body size across modern spatial gradients. Our conclusion is supported by the temporal data, demonstrating that the body size of S. beecheyi has increased in northern California since the LGM, concordant with precipitation but not temperature change in the region.
Main conclusions Precipitation, rather than temperature, vegetation or number of congeneric species, was the main factor explaining both spatial and temporal patterns of body-size variation in S. beecheyi . The integration of space and time provides a powerful mechanism for predicting how local populations may respond to current and future climatic changes. 相似文献
Location California, western North America.
Methods We quantified body size of modern populations of ground squirrels ( n = 81) and used a model-selection approach to determine the best variables (sex, vegetation, number of congeners, temperature and/or precipitation) explaining geographical variation in body size among modern populations. We also quantified body size of one fossil population in northern California ( n = 39) and compared temporal body-size change in S. beecheyi at this location since the LGM with model predictions.
Results Body size of modern populations conformed to Bergmann's rule, with larger individuals in northern (wetter and cooler) portions of California. However, the models suggest that precipitation, rather than temperature or other variables, may best explain variation in body size across modern spatial gradients. Our conclusion is supported by the temporal data, demonstrating that the body size of S. beecheyi has increased in northern California since the LGM, concordant with precipitation but not temperature change in the region.
Main conclusions Precipitation, rather than temperature, vegetation or number of congeneric species, was the main factor explaining both spatial and temporal patterns of body-size variation in S. beecheyi . The integration of space and time provides a powerful mechanism for predicting how local populations may respond to current and future climatic changes. 相似文献
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Direct and indirect cues of predatory risk and patch use by fox squirrels and thirteen-lined ground squirrels 总被引：7，自引：0，他引：7
Thorson James M.; Morgan Robert A.; Brown Joel S.; Norman Jane E. 《Behavioral ecology》1998,9(2):151-157
We used giving-up densities in food patches to measure the effectsof several direct (left by the predator) and indirect (environmentalcorrelates of risk) cues of predatory risk on the foraging behaviorof free-living fox squirrels (Sciurus niger) and thirteen-linedground squirrels (Spermophihis tridtctmlineatus). Increasesin giving-up density in response to stimuli allow quantitativecomparisons of the effects of different types of cues. We usedolfactory (urine of red fox) and visual (plastic models of owls)direct cues. As indirect cues, we used mkrohabitat (near orfar from a refuge), background coloration (white, green, andbrown tarpaulins), and escape substrate (canvas tarpaulins versusnatural surrounding substrates). Both squirrel species respondedmost strongly to microhabitat Fox squirrels increased theirgiving-up density by 97% when feeding 4–6 m from a treecompared to feeding at the tree base. Thirteen-lined groundsquirrels increased giving-up densities 84% when feeding 2 mfrom their burrows compared to feeding at the burrow entry.In response to an unfavorable escape substrate (canvas versusgrass), fox squirrel giving-up densities increased 61%. Foxsquirrels and ground squirrels increased giving-up densities26% and 35%, respectively, in response to a plastic owL Backgroundcoloration had no demonstrable effect on the giving-up densitiesof fox squirrels. In contrast to other work on nocturnal mammalianherbivores and granivores, the diurnal fox squirrels did notrespond to olfactory cues. 相似文献
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Julissa I. Irizarry Jaime A. Collazo Stephen J. Dinsmore 《Diversity & distributions》2016,22(4):410-421
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The frequency of territory occupancy is a good indicator of territory quality. We studied territory occupancy in a Swiss population of the Wryneck Jynx torquilla , a declining farmland woodpecker, with the aim of identifying key habitat features for conservation management. Both static and dynamic approaches were applied using data on nest-site occupancy of 100 territories from six successive years. The static approach models the probability of territory occupancy; the dynamic approach estimates territory colonization and extinction. Frequently occupied territories were settled earlier in the season, suggesting that they may be of better quality, and birds settling in these territories had higher breeding success. Probability of territory occupancy increased with the area of old pear orchards and decreased with the area of vegetable cultivation. Both the area of old pear orchards and the presence of conspecifics within a territory were positively related to territory colonization, whereas territory extinction was negatively related to habitat heterogeneity. Old pear orchards were characterized by having both the highest density of ant nests and the greatest amount of bare ground. The latter is likely to facilitate access to ant prey. To ensure persistence of Wryneck populations in farmland, heterogeneous habitat matrices with high ant nest density and bare ground should be promoted. Finally, provision of artificial nesting cavities is likely to enhance territory occupancy. Providing that these key resources are present, Wrynecks are likely to persist even in intensively farmed areas. 相似文献
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Claudia Gutiérrez-Arellano;Elizabeth E. Crone;Nathalie Pettorelli;Jenny A. Hodgson; 《Diversity & distributions》2024,30(5):e13822
Stochastic patch occupancy models (SPOMs) are a type of spatial population simulation. They are arguably well-suited to guide conservation in human-altered landscapes, but their appropriateness for a wide range of species and landscape types has often been questioned. Here, we provide an overview of how SPOM research has expanded over the last three decades and discuss the untapped potential for these models to inform current conservation strategies. 相似文献
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Jennifer M. Duggan Edward J. Heske Robert L. Schooley Aimee Hurt Alice Whitelaw 《The Journal of wildlife management》2011,75(5):1209-1217
We compared the effectiveness and cost of distribution surveys using livetrapping to those using detection dog-handler teams for a cryptic rodent (Franklin's ground squirrel [Poliocitellus franklinii]). We livetrapped at 62 sites in Illinois, Indiana, Iowa, Missouri, and Wisconsin for Franklin's ground squirrels in 2007–2009 and surveyed 40 of those sites using detection dogs in 2009. Independent surveys of a site by 2 dog-handler teams took <1 hr and yielded detection rates comparable to 2 daily livetrapping surveys (detection rate = 83–84%). However, false presences are a potential problem when detection dogs are trained to scent of a species that leaves little visual sign to confirm its presence. Surveys by 2 dog-handler teams cost >2 daily livetrapping surveys conducted by 2 technicians but more and larger sites can be surveyed by dog-handler teams in a shorter time. For surveys covering large spatial scales or when time is a limiting factor, number of false presences, and study costs can be reduced by employing a 2-stage survey protocol in which livetrapping is conducted only at sites where detection dog surveys indicate presence. We conclude a 2-stage strategy could be used effectively in large-scale surveys for a variety of rare and cryptic species. © 2011 The Wildlife Society. 相似文献
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By causing extinctions and altering community structure, anthropogenic disturbances can disrupt processes that maintain ecosystem integrity. However, the relationship between community structure and ecosystem functioning in natural systems is poorly understood. Here we show that habitat loss appeared to disrupt ecosystem functioning by affecting extinction order, species richness and abundance. We studied pollination by bees in a mosaic of agricultural and natural habitats in California and dung burial by dung beetles on recently created islands in Venezuela. We found that large-bodied bee and beetle species tended to be both most extinction-prone and most functionally efficient, contributing to rapid functional loss. Simulations confirmed that extinction order led to greater disruption of function than predicted by random species loss. Total abundance declined with richness and also appeared to contribute to loss of function. We demonstrate conceptually and empirically how the non-random response of communities to disturbance can have unexpectedly large functional consequences. 相似文献
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Cody J. Schank Michael V. Cove Marcella J. Kelly Eduardo Mendoza Georgina O'Farrill Rafael Reyna‐Hurtado Ninon Meyer Christopher A. Jordan Jose F. González‐Maya Diego J. Lizcano Ricardo Moreno Michael T. Dobbins Victor Montalvo Carolina Sáenz‐Bolaños Eduardo Carillo Jimenez Nereyda Estrada Juan Carlos Cruz Díaz Joel Saenz Manuel Spínola Andrew Carver Jessica Fort Clayton K. Nielsen Francisco Botello Gilberto Pozo Montuy Marina Rivero Jesús Antonio de la Torre Esteban Brenes‐Mora Oscar Godínez‐Gómez Margot A. Wood Jessica Gilbert Jennifer A. Miller 《Diversity & distributions》2017,23(12):1459-1471
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Bycatch in artisanal gill nets threatens the vaquita, Phocoena sinus, with extinction. In 2008 the Mexican government announced a conservation action plan for this porpoise, with three options for a protected area closed to gill net fishing. The probability of success of each of the three options was estimated with a Bayesian population model, where success was defined as an increase in vaquita abundance after 10 yr. The model was fitted to data on abundance, bycatch, and fishing effort, although data were sparse and imprecise. Under the first protected area option, the existing Refuge Area for the Protection of the Vaquita, bycatch was about 7% of population size, and probability of success was 0.08. Under the second option with a larger protected area, the probability of success was 0.35. The third option was large enough to eliminate vaquita bycatch and had a probability of success >0.99. Probability of success was reduced if elimination of vaquita bycatch was delayed or incomplete. Despite considerable efforts by the Mexican government to support vaquita conservation, abundance will probably continue to decline unless additional measures to reduce vaquita bycatch are taken, such as banning gill nets within the vaquita's range and developing effective alternative fishing gear. 相似文献
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Simon Ducatez Mathieu Giraudeau Christophe Thébaud Lisa Jacquin 《Global Change Biology》2017,23(8):3030-3039
Colour polymorphisms have played a major role in enhancing current understanding of how selection and demography can impact phenotypes. Because different morphs often display alternative strategies and exploit alternative ecological niches, colour polymorphism can be expected to promote adaptability to environmental changes. However, whether and how it could influence populations' and species' response to global changes remains debated. To address this question, we built an up‐to‐date and complete database on avian colour polymorphism based on the examination of available data from all 10,394 extant bird species. We distinguished between true polymorphism (where different genetically determined morphs co‐occur in sympatry within the same population) and geographic variation (parapatric or allopatric colour variation), because these two patterns of variation are expected to have different consequences on populations' persistence. Using the IUCN red list, we then showed that polymorphic bird species are at lesser risk of extinction than nonpolymorphic ones, after controlling for a range of factors such as geographic range size, habitat breadth, life history, and phylogeny. This appears consistent with the idea that high genetic diversity and/or the existence of alternative strategies in polymorphic species promotes the ability to adaptively respond to changing environmental conditions. In contrast, polymorphic species were not less vulnerable than nonpolymorphic ones to specific drivers of extinction such as habitat alteration, direct exploitation, climate change, and invasive species. Thus, our results suggest that colour polymorphism acts as a buffer against environmental changes, although further studies are now needed to understand the underlying mechanisms. Developing accurate quantitative indices of sensitivity to specific threats is likely a key step towards a better understanding of species response to environmental changes. 相似文献
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