scholarly journals Does timing of birth affect juvenile and mare survival in wild plains zebra?

2021 ◽  
Author(s):  
Lucie Thel ◽  
Christophe Bonenfant ◽  
Simon Chamaillé-Jammes
Keyword(s):  
Population Dynamics ◽  
Food Resource ◽  
Dry Season ◽  
Observation Data ◽  
Wet Season ◽  
Large Herbivore ◽  
Large Herbivores ◽  
Annual Survival ◽  
Timing Of Births ◽  
Long Term Observation

In large herbivores, the timing of births is mainly driven by the seasonal availability of their food resource. Population dynamics is strongly influenced by juvenile survival and recruitment, which highly depend on whether individuals are born during a favourable period or not. If births often occur during the most suitable season in northern cyclical environments for many large herbivore species, zebra give birth year-round at Hwange National Park, Zimbabwe, a tropical bushland characterized by the succession of a favourable wet season and a less favourable dry season. We used capture-recapture models for analysing long term observation data collected between 2008 and 2019 in this zebra population. We investigated the effect of the season (as a categorical variable) and the time spent in dry season on three categories of juveniles (younger foals of less than six months old, older foals between six and twelve months old, and yearlings between one and two years old) and mares survival, according to their reproductive state. The season had no effect on any survival. Younger foals annual survival was not affected by the time spent in dry season, whereas older foals and yearlings annual survival decreased with an increasing exposure to the dry season. Mares annual survival also decreased with an increasing time spent in dry season, whatever the reproductive status, but to a large extend when non-reproducing. The timing of birth, by determining the external conditions experienced by the offspring and their mothers during critical phases of their life cycle, plays a determinant role in their survival. As climate change is expected to lead to more frequent droughts, longer and harsher dry seasons in tropical ecosystems, we hypothesize a detrimental effect on zebra population dynamics in the future.

scholarly journals Long-Term historical and Projected Herbivore Population Dynamics in Ngorongoro Crater, Tanzania

2019 ◽  
Author(s):  
Joseph O. Ogutu ◽  
Patricia D Moehlman ◽  
Hans-Peter Piepho ◽  
Victor A Runyoro ◽  
Michael B Coughenour ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Population Size ◽  
Dry Season ◽  
Climate Change Scenarios ◽  
Wet Season ◽  
Large Herbivore ◽  
Herbivore Species ◽  
Dry Seasons ◽  
Wet And Dry Seasons

The Ngorongoro Crater is an intact caldera with an area of approximately 310 km2. Long term records on herbivore populations, vegetation and rainfall made it possible to analyze historic and project future herbivore population dynamics. In 1974 there was a perturbation in that resident Maasai and their livestock were removed from the Crater. Vegetation structure changed in 1967 from predominately short grassland to mid and tall grasses dominating in 1995. Even with a change in grassland structure, total herbivore biomass remained relatively stable from 1963 to 2012, implying that the crater has a stable multi-herbivore community. However, in 1974, Maasai pastoralists were removed from the Ngorongoro Crater and there were significant changes in population trends for some herbivore species. Buffalo, elephant and ostrich numbers increased significantly during 1974-2012. The zebra population was stable from 1963 to 2012 whereas numbers of other eight species declined substantially between 1974 and 2012 relative to their peak numbers during 1974-1976. Numbers of Grant’s and Thomson’s gazelles, eland, kongoni, waterbuck (wet season only) declined significantly in the Crater in both seasons after 1974. Wildebeest numbers decreased in the Crater between 1974 and 2012 but this decrease was not statistically significant. In addition, some herbivore species were consistently more abundant inside the Crater during the wet than the dry season. This pattern was most evident for the large herbivore species requiring bulk forage, comprising buffalo, eland, and elephant. Analyses of rainfall indicated that there was a persistent annual cycle of 4.83 years. Herbivore population size was correlated with rainfall in both the wet and dry seasons. The relationships established between the time series of historic animal counts in the wet and dry seasons and lagged wet and dry season rainfall series were used to forecast the likely future trajectories of the wet and dry season population size for each species under three alternative climate change scenarios.

scholarly journals Fruiting phenology and consumption by birds in Ficus calyptroceras (Miq.) Miq. (Moraceae)

2002 ◽  
Vol 62 (2) ◽  
pp. 339-346 ◽  
Author(s):  
J. RAGUSA-NETTO
Keyword(s):  
Food Resource ◽  
Bird Species ◽  
Dry Season ◽  
Dry Forest ◽  
Wet Season ◽  
Frugivorous Birds ◽  
Fruiting Phenology ◽  
Dry Seasons ◽  
Seed Dispersers ◽  
Wet And Dry Seasons

Figs are a remarkable food resource to frugivores, mainly in periods of general fruit scarcity. Ficus calyptroceras Miq. (Moraceae) is the only fig species in a type of dry forest in western Brazil. In this study I examined the fruiting pattern as well as fig consumption by birds in F. calyptroceras. Although rainfall was highly seasonal, fruiting was aseasonal, since the monthly proportion of fruiting trees ranged from 4% to 14% (N = 50 trees). I recorded 22 bird species feeding on figs. In the wet season 20 bird species ate figs, while in the dry season 13 did. Parrots were the most important consumers. This group removed 72% and 40% of the figs consumed in the wet and dry seasons, respectively. No bird species increases fig consumption from dry to wet season. However, a group of bird species assumed as seed dispersers largely increases fig consumption from wet to dry season, suggesting the importance of this resource in the period of fruit scarcity. The results of this study points out the remarkable role that F. calyptroceras plays to frugivorous birds, in such a dry forest, since its fruits were widely consumed and were available all year round.

scholarly journals Drone Surveys Revealed Bottom-Up, And Not Top-Down, Effects On The Marsh Deer Local Abundance

2021 ◽  
Author(s):  
Ismael Verrastro Brack ◽  
Andreas Kindel ◽  
Douglas Oliveira Berto ◽  
José Luis Passos Cordeiro ◽  
Igor Pfeifer Coelho ◽  
...  
Keyword(s):  
Mixture Models ◽  
Negative Relationship ◽  
Dry Season ◽  
Relative Influence ◽  
Top Down ◽  
Large Herbivore ◽  
Large Herbivores ◽  
Bottom Up ◽  
Vegetation Greenness ◽  
Local Abundance

Abstract Context: Spatial variation in large herbivore populations can be highly affected by the availability of resources (bottom-up) but modulated by the presence of predators (top-down). Studying the relative influence of these forces has been a major topic of interest in ecological and conservation research, while it has also been challenging to sample large herbivores. Objective: i) Explore the use of spatiotemporally replicated drone-based counts analysed with N-mixture models to estimate abundance of large herbivores. ii) Evaluate the relative influence of bottom-up (forage and water) and top-down (jaguars) processes on the local abundance of the threatened marsh deer.Methods: We conducted spatiotemporally replicated drone flights in the dry season of Pantanal wetland (Brazil) and imagery was reviewed by either one or two observers. We fitted counts using N-mixture models (for single and double observer protocols) and modelled local abundance in relation to vegetation greenness, distance to water bodies, and jaguar density.Results: We found a positive relationship of marsh deer local abundance with vegetation greenness, a negative relationship with distance to water, but no relation with jaguar density. Individuals were concentrated in the lower and wetter region, even though it is the area expected to be more lethal from jaguar predation.Conclusions: Bottom-up processes are shaping the distribution of marsh deer in the dry season; the benefits of accessing high-quality areas outweigh predation risk from jaguars. Spatiotemporally replicated drone-based counts may serve as an accessible and cost-effective protocol for large herbivores abundance estimation and monitoring while accounting for imperfect detection.

scholarly journals Seasonal pattern of food habits of large herbivores in riverine alluvial grasslands of Brahmaputra floodplains, Assam

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Anita Devi ◽  
Syed Ainul Hussain ◽  
Monika Sharma ◽  
Govindan Veeraswami Gopi ◽  
Ruchi Badola
Keyword(s):  
Crude Protein ◽  
Management Practices ◽  
Feeding Habits ◽  
Seasonal Pattern ◽  
Dry Season ◽  
Imperata Cylindrica ◽  
Suitable Habitat ◽  
Wet Season ◽  
Large Herbivores ◽  
Management Interventions

AbstractJarman–Bell (1974) hypothesized that in the dry savanna of Africa, small-bodied herbivores tend to browse more on forage with high protein and low fibre content. This implies browsing on high nutritive forage by meso-herbivores, and grazing and mixed feeding on coarse forage by mega-herbivores. We tested this hypothesis in the riverine alluvial grasslands of the Kaziranga National Park (KNP), where seasonal flood and fire play an important role in shaping the vegetation structure. We analyzed the feeding habits and quality of major forage species consumed by three mega-herbivores, viz. greater one-horned rhino, Asian elephant, and Asiatic wild buffalo, and three meso-herbivores, viz. swamp deer, hog deer, and sambar. We found that both mega and meso-herbivores were grazers and mixed feeders. Overall, 25 forage plants constituted more than 70% of their diet. Among monocots, family Poaceae with Saccharum spp. (contributing > 9% of the diet), and, among dicots, family Rhamnaceae with Ziziphus jujuba (contributing > 4% of the diet) fulfilled the dietary needs. In the dry season, the concentration of crude protein, neutral detergent fibre, calcium, sodium, and phosphorous varied significantly between monocots and dicots, whereas only calcium and sodium concentrations varied significantly in the wet season. Dicots were found to be more nutritious throughout the year. Compared to the dry season, the monocots, viz. Alpinia nigra, Carex vesicaria, Cynodon dactylon, Echinochloa crus-galli, Hemarthria compressa, Imperata cylindrica, and Saccharum spp., with their significantly high crude protein, were more nutritious during the wet season. Possibly due to the availability of higher quality monocots in the wet season, both mega and meso-herbivores consume it in high proportion. We concluded that the Jarman–Bell principle does not apply to riverine alluvial grasslands as body size did not explain the interspecific dietary patterns of the mega and meso-herbivores. This can be attributed to seasonal floods, habitat and forage availability, predation risk, and management practices such as controlled burning of the grasslands. The ongoing succession and invasion processes, anthropogenic pressures, and lack of grassland conservation policy are expected to affect the availability of the principal forage and suitable habitat of large herbivores in the Brahmaputra floodplains, which necessitates wet grassland-based management interventions for the continued co-existence of large herbivores in such habitats.

Density-dependent body condition and recruitment in a tropical ungulate

2008 ◽  
Vol 86 (1) ◽  
pp. 24-32 ◽  
Author(s):  
N. Gaidet ◽  
J.-M. Gaillard
Keyword(s):  
Population Dynamics ◽  
Body Condition ◽  
Food Resource ◽  
High Density ◽  
Predation Pressure ◽  
Annual Rainfall ◽  
Large Herbivores ◽  
Density Dependent ◽  
Individual Level ◽  
The Individual

In tropical areas, annual rainfall and predation have been reported to drive population dynamics of most species of large herbivores studied so far, with little direct empirical evidence for density-dependent responses of life-history traits. We here investigated in a game ranch in Zimbabwe density-dependent responses of body condition and recruitment in an impala ( Aepyceros melampus (Lichtenstein, 1812)) population that underwent an experimental drastic reduction of density within 2 years under similar rainfall and predation pressure. Body condition of all sex and age classes was lower during the high-density year than during the low-density year, suggesting increased competition for restricted resources at high density. In addition, we observed a significant increase in population recruitment (from 0.47 to 0.80 juveniles/female) as population density declined. Our study provides a rare example of a direct density-dependent response of body condition at the individual level in a tropical ungulate species, and indicates that food resource variation controls population dynamics of impala under constant and moderate predation pressure as is commonly reported in temperate populations of large herbivores.

Diet and habitat-niche relationships within an assemblage of large herbivores in a seasonal tropical forest

2012 ◽  
Vol 28 (4) ◽  
pp. 385-394 ◽  
Author(s):  
Farshid S. Ahrestani ◽  
Ignas M. A. Heitkönig ◽  
Herbert H. T. Prins
Keyword(s):  
Seasonal Variation ◽  
Habitat Selection ◽  
South India ◽  
Niche Breadth ◽  
Niche Overlap ◽  
Dry Season ◽  
Wet Season ◽  
Large Herbivores ◽  
Axis Axis ◽  
Habitat Niche

Abstract:There is little understanding of how large mammalian herbivores in Asia partition habitat and forage resources, and vary their diet and habitat selection seasonally in order to coexist. We studied an assemblage of four large herbivores, chital (Axis axis), sambar (Cervus unicolor), gaur (Bos gaurus) and Asian elephant (Elephas maximus), in the seasonal tropical forests of Bandipur and Mudumalai, South India, and tested predictions regarding the species’ seasonal diet browse : graze ratios, habitat selection and habitat-niche preference and overlap. Field data collected for the study included the seasonal variation in grass quality, the seasonal variation in δ13C in the species’ faeces and the seasonal variation in the species’ habitat selection and overlap using a grid-based survey. Results of the δ13C analyses showed that the chital was more of a grazer in the wet season (−17.9‰ to −21.6‰), but that it increased the proportion of browse in its diet in the dry season (−25.6‰ to −27.7‰); the gaur was a grazer for most of the year (−15.3‰ to −18.6‰); the sambar preferred to browse throughout the year (−21.1‰ to −30.4‰); and that the elephant was a mixed feeder (−14.2‰ to −21.4‰). Elephant habitat-niche breadth was high (0.53 in wet and 0.54 in dry) and overlapped equally with that of the other species in both seasons (0.39–0.94). The gaur had the most restricted habitat-niche breadth in both seasons (0.25 in wet and 0.28 in dry), and it switched from the moist deciduous habitat in the dry season to the dry deciduous habitat in the wet season. These results offer the first insights into the seasonal variation in browse : graze diet ratios and the habitat-niche overlap amongst the common largest-bodied mammalian herbivore species found in South India.

scholarly journals Abundance and frugivory of the toco toucan (Ramphastos toco) in a gallery forest in Brazil's Southern Pantanal

2006 ◽  
Vol 66 (1a) ◽  
pp. 133-142 ◽  
Author(s):  
J. Ragusa-Netto
Keyword(s):  
Food Resource ◽  
Dry Season ◽  
Fleshy Fruit ◽  
Foraging Activity ◽  
Gallery Forest ◽  
Wet Season ◽  
Fruit Availability ◽  
Fleshy Fruits ◽  
Gallery Forests ◽  
Large Home Range

Unlike other toucan species, the Toco toucan (Ramphastos toco) - the largest Ramphastidae - usually inhabits dry semi-open areas. This conspicuous canopy frugivore uses a large home range that includes a variety of vegetation types, among which gallery forests are widely cited as important to this species. However, the factors relating to the occurrence of Toco toucans in such habitats are unclear. I studied the abundance of Toco toucans as well as the availability of fleshy fruit in a gallery forest in the southern Pantanal (sub-region of Miranda, Brazil), in order to assess the relationship between these parameters. Also, I examined toucan foraging activity to analyze its relationship with both toucan abundance and fruit availability. The presence of the Toco toucan was more common in the gallery forest from the middle to the end of the dry season and during the middle of the wet season. Toucans foraged for fleshy fruits, mainly Genipa americana, Ficus luschnatiana, and Cecropia pachystachya fruits, feeding mostly on G. americana (by far the favorite food resource) and F. luschnatiana fruits during the dry season, while C. pachystachya fruits were important in the wet season. Toco toucans foraged particularly heavily (> 80% of foraging activity) on G. americana fruits during the latter part of the dry season, when fleshy fruit availability declined sharply. Toco toucan abundance in the gallery forest was associated with the availability of the most commonly consumed fleshy fruits, and also with its foraging activity. This finding suggests that the Toco toucan moved to the gallery forest periodically in response to the availability of abundant food resources, especially the G. americana fruits widely available and exploited during the severely dry season. Therefore, these fruits potentially contribute to Toco toucan persistence in the South Pantanal during the harshest period of the year.

scholarly journals Stem growth of woody species at the Nkuhlu exclosures, Kruger National Park: 2006–2010

Koedoe ◽  
2011 ◽  
Vol 53 (1) ◽  
Author(s):  
Peter F. Scogings
Keyword(s):  
Ecosystem Management ◽  
Growth Rates ◽  
Woody Species ◽  
Dry Season ◽  
Stem Growth ◽  
Wet Season ◽  
Conservation Areas ◽  
Large Herbivores ◽  
Chemical Defences ◽  
Conservation Implications

An important aspect of managing African conservation areas involves understanding how large herbivores affect woody plant growth. Yet, data on growth rates of woody species in savannas are scarce, despite its critical importance for developing models to guide ecosystem management. What effect do browsing and season have on woody stem growth? Assuming no growth happens in the dry season, browsing should reduce stem growth in the wet season only. Secondly, do functional species groups differ in stem growth? For example, assuming fine-leaved, spiny species’ growth is not compromised by carbon-based chemical defences, they should grow faster than broad-leaved, chemically defended species. Dendrometers were fixed at 20 cm in height on the main stems of 244 random plants of six woody species in three plots (all large herbivores excluded, partial exclusion, and control) and observed from late 2006 to early 2010. Average monthly increment (AMI) per dendrometer and season (dry, wet) was calculated and the interaction between plot and season tested per species, controlling for initial stem girth. AMIs of Combretum apiculatum, Dichrostachys cinerea and Grewia flavescens were zero in the dry season, whilst those of Acacia exuvialis, Acacia grandicornuta and Euclea divinorum were either positive or negative in the dry season. Wet-season AMI of D. cinerea and dry-season AMI of G. flavescens tended to be reduced by browser exclusion. Net AMI (sum of the seasonal AMIs) was tested per species, but results suggested that only D. cinerea tended to be affected by browser exclusion. The results also suggested that stem radial growth of some fast-growing species is more prone to reduction by browser exclusion than the growth of other species, potentially reducing their competitiveness and increasing their risk of extirpation. Finally, the usefulness of grouping woody species into simple functional groups (e.g. fine-leaved vs. broad-leaved) for ecosystem management purposes in savannas requires further consideration. Conservation implications: Growth rates of woody plants are important parameters in savanna models, but data are scarce. Monitoring dendrometers in manipulative situations over several years can help fill that gap. Results of such studies can be used to identify species prone to high risk of extirpation.

scholarly journals MODEL SEDERHANA 2-DIMENSI ARAH PERGERAKAN SEDIMEN DI SUNGAI PORONG JAWA TIMUR

2016 ◽  
Vol 9 (3) ◽  
pp. 175
Author(s):  
Huda Bachtiar ◽  
Franto Novico ◽  
Fitri Riandini
Keyword(s):  
Numerical Model ◽  
Water Level ◽  
River Mouth ◽  
Sediment Concentration ◽  
Dry Season ◽  
Observation Data ◽  
Wet Season ◽  
Level Data ◽  
Water Level Data ◽  
Mike 21

Model numerik MIKE 21 modul transport sedimen digunakan untuk mengetahui respon pergerakan lumpur Sidoarjo pada saat musim hujan dan musim kemarau dan pengaruh tanggul yang berada di muara Sungai Porong. Data yang digunakan adalah pasang surut muka air laut, kedalaman air, debit sungai, arus dan konsentrasi sedimen. Simulasi dilakukan dengan membuat dua skenario, yaitu pada saat kondisi musim hujan dan pada saat musim kemarau. Hasil simulasi model hidrodinamika di verifikasi dengan data lapangan untuk mendapatkan nilai korelasi. Verifikasi meliputi data muka air dan kecepatan arus baik arah –x maupun –y. Berdasarkan hasil verifikasi didapatkan nilai korelasi muka air sebesar 0.8641 sementara arus bernilai 0.1493 untuk sumbu –x dan 0.1917 untuk sumbu –y. Selanjutnya hasil simulasi model menunjukkan konsentrasi sedimen pada tanggal 27 November 2007 merupakan puncak tertinggi dengan nilai 3.2x10-3 kg/m3 untuk musim hujan sementara untuk musim kemarau konsentrasi sedimen bernilai 0.0x10-3 kg/m3. Kata kunci : Model Numerik, Pergerakan Lumpur, Sungai Porong. Numerical model of MIKE 21 sediment transport module was applied to recognize the response of mud flow respective in rainy and dry season and also to get information of dike effect at the river mouth. Data that used in this simulation was tide, water depth, river discharge, current and sediment concentration. The simulations were created for two scenarios, therefore dry season and wet season. The result of the simulation model verified with observation data to see the correlation value. The verification are covering water level data and current magnitude of –x and –y axis. Based on the verification result, the correlation value of water level has a value 0.8641 meanwhile for the current the correlation value have magnitude 0.1493 of x-axis and 0.1917of y-axis. Moreover, the maximum value of sediment concentration could be seen at November 27th 2007 with 3.2x10-3 kg/m3 at the wet season and 0.0x10-3 kg/m3 for dry season. Keywords: Numerical Model, Mud Movement, Porong River

scholarly journals Another one bites the dust: faecal silica levels in large herbivores correlate with high-crowned teeth

2010 ◽  
Vol 278 (1712) ◽  
pp. 1742-1747 ◽  
Author(s):  
Jürgen Hummel ◽  
Eva Findeisen ◽  
Karl-Heinz Südekum ◽  
Irina Ruf ◽  
Thomas M. Kaiser ◽  
...  
Keyword(s):  
Dry Matter ◽  
Dominant Role ◽  
Silica Content ◽  
Dry Season ◽  
Feeding Strategies ◽  
Strong Positive Correlation ◽  
Wet Season ◽  
Large Herbivores ◽  
African Herbivores

The circumstances of the evolution of hypsodonty (= high-crowned teeth) are a bone of contention. Hypsodonty is usually linked to diet abrasiveness, either from siliceous phytoliths (monocotyledons) or from grit (dusty environments). However, any empirical quantitative approach testing the relation of ingested silica and hypsodonty is lacking. In this study, faecal silica content was quantified as acid detergent insoluble ash and used as proxy for silica ingested by large African herbivores of different digestive types, feeding strategies and hypsodonty levels. Separate sample sets were used for the dry ( n = 15 species) and wet ( n = 13 species) season. Average faecal silica contents were 17–46 g kg −1 dry matter (DM) for browsing and 52–163 g kg −1 DM for grazing herbivores. No difference was detected between the wet (97.5 ± 14.4 g kg −1 DM) and dry season (93.5 ± 13.7 g kg −1 DM) faecal silica. In a phylogenetically controlled analysis, a strong positive correlation (dry season r = 0.80, p < 0.0005; wet season r = 0.74, p < 0.005) was found between hypsodonty index and faecal silica levels. While surprisingly our results do not indicate major seasonal changes in silica ingested, the correlation of faecal silica and hypsodonty supports a scenario of a dominant role of abrasive silica in the evolution of high-crowned teeth.

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