scholarly journals Effects of livestock grazing on flocks of seed-eating birds in the central Monte desert, Argentina

2019 ◽  
Vol 97 (7) ◽  
pp. 606-611
Author(s):  
A. Zarco ◽  
V.R. Cueto ◽  
M.C. Sagario ◽  
L. Marone
Keyword(s):  
Structural Characteristics ◽  
Resource Depletion ◽  
Cattle Grazing ◽  
Livestock Grazing ◽  
Foraging Efficiency ◽  
Monte Desert ◽  
Management Actions ◽  
Animal Populations ◽  
Nuclear Species ◽  
Seed Eating

Animal populations often decline due to habitat disturbance, but the initial response of organisms to human-induced environmental change is usually behavioral. Intra- and inter-specific interactions can restrict or facilitate access to resources, resulting in changes to individual fitness, and resource depletion may affect the frequency and strength of interactions. In birds, it is often assumed that feeding in groups increases foraging efficiency. We assessed how the reduction of seed resources provoked by cattle grazing affected different properties of seed-eating bird flocks in woodlands having the same structural characteristics but differing in seed abundance. Under lower availability of grass seeds (i.e., under grazing), flocks were smaller and less rich and birds showed a lower flocking propensity. This pattern could be explained by three non-exclusive hypotheses. Food reduction caused by grazing (i) decreases the number of seed-eating birds and concomitantly generates smaller flocks; (ii) reduces the density of nuclear species, decreasing the group cohesion in large flocks; (iii) makes large flocks less attractive by increasing individual competence for food. Our results provide evidence that cattle grazing affect the interactions of seed-eating birds and suggest the importance of understanding flocking behavior to bring about management actions.

Bridled Quail-dove Geotrygon mystacea population assessment after hurricanes Irma and Maria, St. Eustatius, Caribbean Netherlands

2021 ◽  
pp. 1-12
Author(s):  
FRANK F. RIVERA-MILÁN ◽  
HANNAH MADDEN ◽  
KEVIN VERDEL
Keyword(s):  
National Park ◽  
Food Limitation ◽  
Distance Sampling ◽  
Population Status ◽  
Management Actions ◽  
Abundance Estimates ◽  
Detection Mode ◽  
Limited Food ◽  
Seed Eating ◽  
Free Ranging

Summary Structural vegetation damage and food limitation are important effects of major hurricanes, particularly for fruit/seed-eating, forest-dependent Caribbean birds with restricted distributions and small populations, such as the Bridled Quail-dove Geotrygon mystacea. Motivated by the lack of abundance estimates, corrected for detection probability, we conducted distance-sampling surveys inside and outside the Quill National Park each May in 2016-2019. Detection mode was the most important covariate, with others receiving no support from the data. Detectability of available single individuals and clusters of individuals within 60 m of transect centrelines averaged 0.957 ± 0.114 standard error for audio detections, 0.434 ± 0.052 for visual detections, and 0.693 ± 0.064 for detection modes combined. Availability averaged 0.475 ± 0.138 and the product of detectability and availability averaged 0.329 ± 0.098. Density averaged 1.459 ± 0.277 individuals ha-1 and population size averaged 642 ± 122 individuals in 440 ha. Density did not differ along and away from forest trails, but was higher inside than outside the park and at elevations within 201-400 m than 100-200 m and 401-600 m. Density declined by 76% after hurricanes Irma and Maria in 2017. We suggest that major hurricanes together with free-ranging livestock overgrazing degraded foraging habitats, limited food supply, and caused a population bottleneck. Our methodology can be implemented across the distribution range to assess population status and trends and evaluate the result of management actions at key conservation sites. Bridled Quail-dove populations probably were declining on most islands before the 2017 hurricanes and population status warrants revision.

scholarly journals Challenges and Opportunities Developing Mathematical Models of Shared Pathogens of Domestic and Wild Animals

2018 ◽  
Vol 5 (4) ◽  
pp. 92 ◽  
Author(s):  
Kathryn Huyvaert ◽  
Robin Russell ◽  
Kelly Patyk ◽  
Meggan Craft ◽  
Paul Cross ◽  
...  
Keyword(s):  
Mathematical Models ◽  
Domestic Animals ◽  
Domestic Animal ◽  
Pathogen Transmission ◽  
Management Actions ◽  
Animal Populations ◽  
Challenges And Opportunities ◽  
Conservation Concern ◽  
Transmission Pathways ◽  
And Control

Diseases that affect both wild and domestic animals can be particularly difficult to prevent, predict, mitigate, and control. Such multi-host diseases can have devastating economic impacts on domestic animal producers and can present significant challenges to wildlife populations, particularly for populations of conservation concern. Few mathematical models exist that capture the complexities of these multi-host pathogens, yet the development of such models would allow us to estimate and compare the potential effectiveness of management actions for mitigating or suppressing disease in wildlife and/or livestock host populations. We conducted a workshop in March 2014 to identify the challenges associated with developing models of pathogen transmission across the wildlife-livestock interface. The development of mathematical models of pathogen transmission at this interface is hampered by the difficulties associated with describing the host-pathogen systems, including: (1) the identity of wildlife hosts, their distributions, and movement patterns; (2) the pathogen transmission pathways between wildlife and domestic animals; (3) the effects of the disease and concomitant mitigation efforts on wild and domestic animal populations; and (4) barriers to communication between sectors. To promote the development of mathematical models of transmission at this interface, we recommend further integration of modern quantitative techniques and improvement of communication among wildlife biologists, mathematical modelers, veterinary medicine professionals, producers, and other stakeholders concerned with the consequences of pathogen transmission at this important, yet poorly understood, interface.

scholarly journals Landscape associations of globally threatened grassland birds in the Aguapey river Important Bird Area, Corrientes, Argentina

2009 ◽  
Vol 20 (1) ◽  
pp. 62-73 ◽  
Author(s):  
ADRIAN S. DI GIACOMO ◽  
PETER D. VICKERY ◽  
HERNAN CASAÑAS ◽  
OSCAR A. SPITZNAGEL ◽  
CHRISTIAN OSTROSKY ◽  
...  
Keyword(s):  
River Basin ◽  
Grassland Birds ◽  
Livestock Grazing ◽  
Tall Grass ◽  
Point Counts ◽  
Landscape Characteristics ◽  
Bird Populations ◽  
Management Actions ◽  
Land Use Plan ◽  
Near Threatened

SummaryThe Aguapey river basin in the Pampas grasslands of Argentina is the last refuge for a complete assemblage of globally threatened and Near Threatened birds. We evaluated the influence of landscape characteristics on the occurrence and abundance of six globally threatened and Near Threatened passerines. We used point counts to census birds and vegetation and quantified landscape characteristics 1,000 m from the count centres using remote sensing tools. Strange-tailed Tyrants Alectrurus risora were associated with higher percentages of tall-grass Andropogon lateralis in lowland areas. Saffron-cowled Blackbirds Xanthopsar flavus and Black-and-white Monjitas Heteroxolmis dominicana were associated with rolling landscape with wet lowland grasslands and marshes linked with dry upland grasslands. Marsh Seedeater Sporophila palustris and Chestnut Seedeater S. cinnamomea were associated with tall grasslands and marshes. Rufous-throated Seedeater S. ruficollis was not clearly associated with any type of habitat. The Aguapey grasslands are used mainly for livestock grazing and afforestation. Since 1995, approximately 50% of the original grassland habitat has been planted with exotic trees. If this trend continues, Saffron-cowled Blackbirds are likely to become extinct in the Aguapey river basin which currently supports the largest population of this species in Argentina. We recommend guidelines for establishing future reserves and wildlife management actions based on the landscape responses detected in this study. Future action should consider: maintaining connectivity between the Aguapey grasslands and the Ibera Nature Reserve, creating a protected area, designing a land use plan for the basin, avoiding afforestation in large blocks, removal of government incentives for large afforestation projects, and studying the viability of threatened bird populations in extensive cattle ranching areas.

scholarly journals Foraging loads of red wood ants:Formica aquilonia(Hymenoptera: Formicidae) in relation to tree characteristics and stand age

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2049 ◽  
Author(s):  
Heloise Gibb ◽  
Jon Andersson ◽  
Therese Johansson
Keyword(s):  
Large Diameter ◽  
Negative Relationship ◽  
Small Diameter ◽  
Resource Depletion ◽  
Foraging Efficiency ◽  
Stand Age ◽  
Resource Quality ◽  
Red Wood Ants ◽  
Wood Ants ◽  
Colony Level

Background.Foraging efficiency is critical in determining the success of organisms and may be affected by a range of factors, including resource distance and quality. For social insects such as ants, outcomes must be considered at the level of both the individual and the colony. It is important to understand whether anthropogenic disturbances, such as forestry, affect foraging loads, independent of effects on the quality and distribution of resources. We asked if ants harvest greater loads from more distant and higher quality resources, how individual efforts scale to the colony level, and whether worker loads are affected by stand age.Methods.First, we performed a fine-scale study examining the effect of distance and resource quality (tree diameter and species) on harvesting of honeydew by red wood ants,Formica aquilonia, in terms of crop load per worker ant and numbers of workers walking up and down each tree (ant activity) (study 1). Second, we modelled what the combination of load and worker number responses meant for colony-level foraging loads. Third, at a larger scale, we asked whether the relationship between worker load and resource quality and distance depended on stand age (study 2).Results.Study 1 revealed that seventy percent of ants descending trees carried honeydew, and the percentage of workers that were honeydew harvesters was not related to tree species or diameter, but increased weakly with distance. Distance positively affected load mass in both studies 1 and 2, while diameter had weak negative effects on load. Relationships between load and distance and diameter did not differ among stands of different ages. Our model showed that colony-level loads declined much more rapidly with distance for small diameter than large diameter trees.Discussion.We suggest that a negative relationship between diameter and honeydew load detected in study 1 might be a result of crowding on large diameter trees close to nests, while the increase in honeydew load with distance may result from resource depletion close to nests. At the colony level, our model suggests that very little honeydew was harvested from more distant trees if they were small, but that more distant larger trees continued to contribute substantially to colony harvest. Although forestry alters the activity and foraging success of red wood ants, study 2 showed that it does not alter the fundamental rules determining the allocation of foraging effort.

Cattle grazing effects on annual plants assemblages in the Central Monte Desert, Argentina

2009 ◽  
Vol 73 (4-5) ◽  
pp. 537-541 ◽  
Author(s):  
P.L. Sassi ◽  
P.A. Taraborelli ◽  
C.E. Borghi ◽  
R.A. Ojeda
Keyword(s):  
Cattle Grazing ◽  
Annual Plants ◽  
Monte Desert ◽  
Grazing Effects

scholarly journals Livestock grazing is associated with seasonal reduction in pollinator biodiversity and functional dispersion but cheatgrass invasion is not: variation in bee assemblages in a multi-use shortgrass prairie

2020 ◽  
Author(s):  
Khum Bahadur Thapa-Magar ◽  
Thomas Seth Davis ◽  
Boris C. Kondratieff
Keyword(s):  
Growing Season ◽  
Cattle Grazing ◽  
Soil Disturbance ◽  
Livestock Grazing ◽  
Native Plant ◽  
Native Plant Species ◽  
Shortgrass Prairie ◽  
Functional Dispersion ◽  
Bee Communities ◽  
Bee Abundance

AbstractLivestock grazing and non-native plant species affect rangeland habitats globally. These factors may have important effects on ecosystem services including pollination, yet, interactions between pollinators, grazing, and invasive plants are poorly understood. To address this, we tested the hypothesis that cattle grazing and site colonization by cheatgrass (Bromus tectorum) impact bee foraging and nesting habitats, and the biodiversity of wild bee communities, in a shortgrass prairie system. Bee nesting habitats (litter and wood cover) were marginally improved in non-grazed sites, though foraging habitat (floral cover and richness) did not differ among grazed, non-grazed, or cheatgrass colonized sites. However, floral cover was a good predictor of bee abundance and functional dispersion. Mean bee abundance, richness, diversity and functional diversity were significantly lower in cattle-grazed habitats than in cheatgrass-colonized or non-grazed habitats. Differences in bee diversity among habitats were pronounced early in the growing season (May) but by late-season (August) these differences eroded. Fourth-corner analysis revealed that sites with high floral cover tended to support large, social, polylectic bees; sites with high grass cover tended to support oligolectic solitary bees. Both cattle-grazed and cheatgrass-colonized sites were associated with lower abundances of above-ground nesting bees but higher abundance of below-ground nesters. We conclude that cheatgrass-invaded sites are not associated with reduced bee biodiversity or abundance, but cattle grazing was negatively associated with bee abundances and altered species composition. Although floral cover is an important predictor of bee assemblages, this was not impacted by grazing and our suggests that cattle likely impact bee communities through effects other than those mediated by forbs, including soil disturbance or nest destruction. Efforts aimed at pollinator conservation in prairie habitats should focus on managing cattle impacts early in the growing season to benefit sensitive bee species.

scholarly journals Additive effects of climate and fisheries drive ongoing declines in multiple albatross species

2017 ◽  
Vol 114 (50) ◽  
pp. E10829-E10837 ◽  
Author(s):  
Deborah Pardo ◽  
Jaume Forcada ◽  
Andrew G. Wood ◽  
Geoff N. Tuck ◽  
Louise Ireland ◽  
...  
Keyword(s):  
Mitigation Measures ◽  
Adult Survival ◽  
Anthropogenic Factors ◽  
Population Declines ◽  
Management Actions ◽  
Recovery Potential ◽  
Top Predators ◽  
Animal Populations ◽  
Multievent Models ◽  
Anthropogenic Drivers

Environmental and anthropogenic factors often drive population declines in top predators, but how their influences may combine remains unclear. Albatrosses are particularly threatened. They breed in fast-changing environments, and their extensive foraging ranges expose them to incidental mortality (bycatch) in multiple fisheries. The albatross community at South Georgia includes globally important populations of three species that have declined by 40–60% over the last 35 years. We used three steps to deeply understand the drivers of such dramatic changes: (i) describe fundamental demographic rates using multievent models, (ii) determine demographic drivers of population growth using matrix models, and (iii) identify environmental and anthropogenic drivers using ANOVAs. Each species was affected by different processes and threats in their foraging areas during the breeding and nonbreeding seasons. There was evidence for two kinds of combined environmental and anthropogenic effects. The first was sequential; in wandering and black-browed albatrosses, high levels of bycatch have reduced juvenile and adult survival, then increased temperature, reduced sea-ice cover, and stronger winds are affecting the population recovery potential. The second was additive; in gray-headed albatrosses, not only did bycatch impact adult survival but also this impact was exacerbated by lower food availability in years following El Niño events. This emphasizes the need for much improved implementation of mitigation measures in fisheries and better enforcement of compliance. We hope our results not only help focus future management actions for these populations but also demonstrate the power of the modelling approach for assessing impacts of environmental and anthropogenic drivers in wild animal populations.

Impact of grazing on fine fuels and potential wildfire behaviour in a non-native tropical grassland

2015 ◽  
Vol 21 (2) ◽  
pp. 126 ◽  
Author(s):  
Edward W. Evans ◽  
Lisa M. Ellsworth ◽  
Creighton M. Litton
Keyword(s):  
Cattle Grazing ◽  
Model Potential ◽  
Fire Frequency ◽  
Flame Length ◽  
Conclusive Evidence ◽  
Livestock Grazing ◽  
Ecological Processes ◽  
Native Grass ◽  
Fuel Loads ◽  
The Tropics

Non-native grass invasion has increased fuel loads and fire frequency in areas throughout the tropics, resulting in a non-native grass–wildfire cycle with negative impacts on native biodiversity and ecological processes. Megathyrsus maximus (guinea grass) invades dry and mesic ecosystems throughout the tropics, increasing fuel loads and wildfire intensity. Eradication of M. maximus is difficult, making effective wildfire management critical to the protection of adjacent developed areas and remnant native ecosystems. The use of domestic livestock grazing in non-native grass ecosystems may be effective at decreasing fine fuel loads and potential wildfire behaviour. Our objectives were to: (1) quantify live and dead fine fuel loads and moistures in a M. maximus–dominated ecosystem before and after cattle grazing, and (2) use these data to model potential wildfire behaviour in grazed and ungrazed M. maximus grasslands with the BehavePlus fire modelling system. Fine fuel loads and moistures, climate variables, and predicted wildfire behaviour were quantified at the same site (n = 1) over two 5-month periods (March–July 2009, ungrazed; March–July 2010, grazed) in the Wai‘anae Kai Forest Reserve on the Island of O‘ahu, Hawai‘i. Strong to conclusive evidence existed that cattle grazing in this system decreased dead and total fuel loads, but did not alter live fuel loads, or live and dead fuel moistures. Modelled wildfire behaviour under both low and average fuel moisture scenarios revealed that grazing decreased the potential rate of spread by 44–52% and flame length by 36–41%. These results demonstrate that cattle grazing may be an effective approach for reducing fuel loads and potential wildfire behaviour in non-native-dominated grasslands on tropical islands.

From Catastrophe to Recovery: Stories of Fishery Management Success

2019 ◽  
Keyword(s):  
Rainbow Trout ◽  
Brook Trout ◽  
Salmo Trutta ◽  
Fishery Management ◽  
Species Conservation ◽  
Livestock Grazing ◽  
Genetic Introgression ◽  
Genetic Management ◽  
Chemical Treatments ◽  
Management Actions

Abstract.—Native golden trout of California’s upper Kern River basin have inspired anglers and scientists alike with their beauty, ecology, and evolutionary history. Three Rainbow Trout <i>Oncorhynchus mykiss</i> subspecies comprise the golden trout complex: California Golden Trout <i>O. m. aguabonita</i>, Little Kern Golden Trout <i>O. m. whitei</i>, and Kern River Rainbow Trout <i>O. m. gilberti</i>. This chapter focuses on restoration and management of the first two subspecies, California Golden Trout and Little Kern Golden Trout. Agency biologists, other scientists, and citizens have all worked for more than 100 years to protect and save these subspecies from a range of threats, some of fishery managers’ own making and some threats evolving over time. Major problems have included overharvest by anglers, overgrazing of habitat by livestock, competition and predation by nonnative Brown Trout <i>Salmo trutta</i> and Brook Trout <i>Salvelinus fontinalis</i>, and hybridization with introduced nonnative forms of Rainbow Trout subspecies; these factors drove both species perilously close to extinction by the late 1960s. Little Kern Golden Trout were listed as threatened in 1978 under the U.S. Federal Endangered Species Act. That same year, the federal government designated large portions of California Golden Trout and Little Kern Golden Trout native watersheds as the Golden Trout Wilderness. Management actions to prevent extinction and conserve these subspecies have included angling regulations, livestock grazing restrictions, barrier construction, chemical treatments to remove nonnative trout, and research to identify and quantify genetic introgression of nonnative Rainbow Trout genes into native golden trout populations. Restoration efforts have, thus far, averted extinction, allowed populations to rebound, and provided several important lessons on genetic management of closely related subspecies, including pitfalls of a zero-introgression target for conservation, the potential need to continue management indefinitely, being responsive to emerging threats, recognizing that barriers to upstream fish movement can be useful, the caveats of using hatcheries for conservation, the potential role of native trout donor populations to facilitate restoration, and the need to harness public and stakeholder understanding and support for species conservation.

Sign in / Sign up

Export Citation Format

Share Document