Dung Counts Research Articles

Repeated clearing as a mechanism for savanna recovery following bush encroachment

Abstract Many savannas are experiencing increased cover of trees and shrubs, resulting in reduced herbaceous productivity, shifts in savanna functional structure and potential reductions in ecotourism. Clearing woody plants has been suggested as an effective management strategy to mitigate these effects and restore these systems to an open state with higher rates of grass production and herbivory. This study investigated the effectiveness of repeated shrub clearing as a tool to mitigate bush encroachment in a semi‐arid savanna in southern Africa. We present data from a 7‐year experiment in the Mthimkhulu Game Reserve bordering Kruger National Park, South Africa. Colophospermum mopane stems and resprouting shoots were basally cut 2–3 times per year (2015–2022) in three pairs of treatment and control plots of 60 × 60 m. We monitored changes in soil moisture, grass biomass and herbivore activity via dung counts. We assessed C. mopane physiological responses to repeated cutting using non‐structural carbohydrates and stable water isotopes to infer changes to energy storage and functional rooting depth, respectively. The cleared treatment had higher soil moisture and grass biomass than the control treatment. Dung counts showed impala and buffalo visited the cleared treatment more frequently than the control treatment. Repeated cutting had limited effects on C. mopane survival in the first 2–3 years after initial clearing, but 80% of individuals were dead after 7 years. Repeatedly cut C. mopane had lower belowground starch concentrations and used water from shallower soil depths than C. mopane in control plots. Synthesis and applications. Repeated cutting increased soil moisture availability and grass biomass, and attracted charismatic grazing herbivores. While more costly than once‐off clearing methods, this practice created more employment opportunities for a neighbouring rural community. Transforming portions of the ecosystem to a grass‐dominated state may increase ecotourism potential through improved game viewing in open systems.

Using density surface models to assess the ecological effectiveness of a protected area network in Tanzania

AbstractGiven recent global endeavors to increase protected area coverage, it is crucial to comprehensively evaluate the efficacy of various area‐based conservation strategies in effectively reducing biodiversity loss. Here, we investigated the responses of wildlife populations to different protection levels and environmental variables at the landscape scale in the Katavi–Rukwa Ecosystem, western Tanzania. To this end, we conducted line distance sampling surveys and counted the dung of six target mammal species (elephant, giraffe, buffalo, zebra, topi, and hartebeest) along foot transects within areas differing in protection levels (from strict to less‐strictly protected: national park, game reserve, forest reserve, game‐controlled area, and unprotected areas). Based on these dung counts, we modeled the spatial distribution of these six mammal species using a species‐specific density surface modeling framework. We found consistent effects of protection level and land use variables on the spatial distribution of the target mammal species: dung densities were highest in the national park and game reserves, intermediate in less‐strictly protected areas, and lowest in unprotected areas. Beyond species‐specific environmental predictors for dung densities, our results highlight consistent negative associations between dung densities of the target species and distance to cropland and avoidance of areas in proximity to houses. Our findings underpin differences in ecological effectiveness of protected areas within one ecosystem. Protection level and land use play crucial roles in moderating the spatial distribution of all considered mammal species. Our findings suggest that a landscape approach needs to guide effective conservation across the entire protection gradient of the Katavi–Rukwa Ecosystem.

Cross-scale analysis reveals interacting predictors of annual and perennial cover in Northern Great Basin rangelands.

Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors of annual grass prevalence and native perennial vegetation have been identified, there remains substantial uncertainty about how regional-scale and local-scale predictors interact to determine vegetation heterogeneity, and how associations between vegetation and cattle grazing vary with environmental context. Here, we conducted a regionally extensive, one-season field survey across burned and unburned, grazed, public lands in Oregon and Idaho, with plots stratified by aspect and distance to water within pastures to capture variation in environmental context and grazing intensity. We analyzed regional-scale and local-scale patterns of annual grass, perennial grass, and shrub cover, and examined to what extent plot-level variation was contingent on pasture-level predictions of site favorability. Annual grasses were widespread at burned and unburned sites alike, contrary to assumptions of annual grasses depending on fire, and more common at lower elevations and higher temperatures regionally, as well as on warmer slopes locally. Pasture-level grazing pressure interacted with temperature such that annual grass cover was associated positively with grazing pressure at higher temperatures but associated negatively with grazing pressure at lower temperatures. This suggests that pasture-level temperature and grazing relationships with annual grass abundance are complex and context dependent, although the causality of this relationship deserves further examination. At the plot-level within pastures, annual grass cover did not vary with grazing metrics, but perennial cover did; perennial grasses, for example, had lower cover closer to water sources, but higher cover at higher dung counts within a pasture, suggesting contrasting interpretations of these two grazing proxies. Importantly for predictions of ecosystem response to temperature change, we found that pasture-level and plot-level favorability interacted: perennial grasses had a higher plot-level cover on cooler slopes, and this difference across topography was starkest in pastures that were less favorable for perennial grasses regionally. Understanding the mechanisms behind cross-scale interactions and contingent responses of vegetation to grazing in these increasingly invaded ecosystems will be critical to land management in a changing world.

Modeling the drivers of large herbivore distribution in human‐dominated southern African savannas

AbstractAfrican savanna ecosystems are home to the world's richest large herbivore (LH) assemblages. However, its landscapes are changing faster than any other region on Earth due to human activities and natural events. Therefore, understanding the factors influencing the distribution of LH in these human‐dominated environments is crucial for decision‐making on wildlife and habitat management. We combined ecological aerial surveys, camera trap, and dung count data to investigate how ecological (habitat types, perennial rivers, and rainfall) and anthropogenic (human settlements and cattle grazing areas) factors influence the distribution of LH species in Limpopo National Park (LNP). We used generalized linear models fitting binary logistic regression models to distinguish 25‐km2 cells occupied (where the species were detected) by elephants (Loxodonta africana), buffalos (Syncerus caffer), zebras (Equus quagga), kudus (Tragelaphus strepsiceros), nyalas (Tragelaphus angasii), and impalas (Aepyceros melampus) from unoccupied regions (where the species were not detected) in the LNP landscape. We found that habitat type and rainfall were the most influential factors shaping the pattern of LH distribution in the LNP, except for elephants, whose prevalence was not associated with rainfall. The prevalence of zebras was positively associated with the proximity to perennial rivers, while kudus avoided these areas. While some species (zebras, kudus, and impalas) tended to avoid settlements, others (elephants, buffalos, and nyala) seemed attracted to settlements. Cattle grazing areas were the worst predictors of the distribution of all study species. Our results disclosed the role of ecological factors for the distribution of LH and showed that anthropogenic disturbances seemed to either (partially) prevent the occurrence of LH or show the potential for human–wildlife conflict risk in the study area. Therefore, the results highlight the need to investigate/quantify the potential human–wildlife conflict risk at finer spatial scales to improve future management.

Historical and current distribution and movement patterns of large herbivores in the Limpopo National Park, Mozambique

This study provides a first attempt to describe the historical distribution and movement patterns of selected large herbivore (LH) species in Limpopo National Park (LNP), an area in Mozambique today connected to a network of transboundary conservation areas. Between 1976 and the early 2000s, most LH species were absent in this area following the civil war in Mozambique followed by intense poaching due to weak law enforcement capacity. Through the reconstruction of the historical and current distribution and movement patterns of seven LH species in five periods, we investigate possible changes in distribution and movement patterns over time. Data collection is based on a systematic literature search, censuses reports, online databases, dung count transects, and camera trap surveys. We mapped all LH observations and movements using ArcGIS 10.1. Our results reveal a dramatic collapse of LH populations between the peak of the colonial period and the post-colonial/civil war period (1800–2001), followed by a slight recovery from the post-proclamation of Great Limpopo Transfrontier Park to the current period (2002–2021). While LH population decline applied to all seven species, there are species-specific differences in the process of restoration: African elephant (Loxodonta africana), African buffalo (Syncerus caffer), and plains zebra (Equus quagga) appear to recover to a greater extent than giraffe (Giraffa camelopardalis), eland (Tragelaphus oryx), blue wildebeest (Connochaetes taurinus), and white rhino (Ceratotherium simum). We found evidence of the functioning of proposed wildlife corridors in the LNP. The results give reason to assume that restoration of populations of LH is still in a very early and vulnerable state and that further efforts are necessary to strengthen the slowly increasing populations of LH. Our results highlight the importance of combining past and current data as a guide for the restoration of threatened species in African savannas impacted by human activities.

Age‐Specific differences in Asian elephant defecation, dung decay, detection and their implication for dung count

AbstractIn vertebrate population estimation, converting faecal density into animal density requires information on the faecal production rate, decay rate and faecal density. Differences in the above factors for long‐lived species across age classes were not evaluated. We have evaluated these factors associated with the dung count of Asian elephants (Elephas maximus) in the tropical forest of southern India.The defecation rate of elephants was determined in semi‐wild elephants at the Mudumalai elephant camp. The relationship between dung bolus diameter and age was determined to estimate the age of the elephant. The total and age‐specific elephant density based on dung bolus diameter was estimated. A total of 24 transect lines of 2–4 km (125 km) were sampled in the study area. An experiment was conducted to assess the detection probability across the age classes of dung piles. The dung decay rates across age classes and seasons were determined by marking fresh dung piles (n = 1551). The dung‐based age structure assessment and its limitations were evaluated.The mean defecation rate was 13.51 ± 0.51 per day. The defecation rate was significantly lower for the younger age class and increased with the age of elephants. Defecation rates were significantly lower in the wet season than in the dry. The dung bolus diameter positively increased with the age of elephants, and the growth curve can be used to predict the age and age structure of elephant populations.The disparity in the dung production rate results in the lower availability of younger age class (juvenile and calf) dung in the transect for counting, which results in lower dung abundance. The detection probability of dung piles of younger age classes was low (0.58). The survival rates of dung piles of younger age classes were lower and increased with the age of elephants in the wet season. Hence, the demographic assessment of the population based on dung needs to consider age‐specific differences in dung production, decay and detection probability. Although the demographic assessment using dung provides insight into population age structure, it has limitations in predicting age structure for young elephants.

Elephant browsing impacts in a Zambezian Baikiaea woodland with a high density of pumped waterholes

Foraging by African savanna elephant ( Loxodonta africana ) and other herbivores tends to result in a piosphere effect around water sources, with increasing pressure on vegetation as distance to water decreases. This study aimed to investigate the impacts of pumped waterholes on woody vegetation in the southern portion of Zimbabwe’s Zambezi National Park, a Baikiaea woodland ecosystem characterised by high elephant densities. The recent rehabilitation and addition of pumped waterholes has resulted in a dense waterhole network in the park, prompting concerns around potential negative impacts on vegetation. Sampling plots were located at different distances from four pumped waterholes in Baikiaea plurijuga and Terminalia sericea woodlands. Elephant browsing levels and vegetation structure were assessed across three plant height classes (0.2 - < 1 m; 1 - < 3 m and ≥ 3 m). Elephant dung counts were also conducted to provide a relative measure of elephant occupancy. A decline in elephant browsing with distance to waterholes was evident in both woodland types, though browsing was consistently higher in the Terminalia woodland. Structural impacts of elevated elephant browsing around waterholes were limited in the Baikiaea woodland. However, substantial reductions in the basal area and canopy volume of trees were evident closer to waterholes in the Terminalia woodland, with widespread conversion of woodland to shrubland. Elephant dung decreased with distance from waterholes in both woodland types, confirming that elephant occupancy was higher closer to waterholes. Overall, clear effects of pumped waterholes were evident. The ecological integrity of the Terminalia woodland in particular appears to be under threat, especially as the current surface water regime places most of it within 3 km of waterholes. The cessation of pumping at some waterholes was thus recommended, to achieve a more heterogenous browsing regime in the area.

Experimental evidence that effects of megaherbivores on mesoherbivore space use are influenced by species' traits.

The extinction of 80% of megaherbivore (>1,000kg) species towards the end of the Pleistocene altered vegetation structure, fire dynamics and nutrient cycling world-wide. Ecologists have proposed (re)introducing megaherbivores or their ecological analogues to restore lost ecosystem functions and reinforce extant but declining megaherbivore populations. However, the effects of megaherbivores on smaller herbivores are poorly understood. We used long-term exclusion experiments and multispecies hierarchical models fitted to dung counts to test (a) the effect of megaherbivores (elephant and giraffe) on the occurrence (dung presence) and use intensity (dung pile density) of mesoherbivores (2-1,000kg), and (b) the extent to which the responses of each mesoherbivore species was predictable based on their traits (diet and shoulder height) and phylogenetic relatedness. Megaherbivores increased the predicted occurrence and use intensity of zebras but reduced the occurrence and use intensity of several other mesoherbivore species. The negative effect of megaherbivores on mesoherbivore occurrence was stronger for shorter species, regardless of diet or relatedness. Megaherbivores substantially reduced the expected total use intensity (i.e. cumulative dung density of all species) of mesoherbivores, but only minimally reduced the expected species richness (i.e. cumulative predicted occurrence probabilities of all species) of mesoherbivores (by <1 species). Simulated extirpation of megaherbivores altered use intensity by mesoherbivores, which should be considered during (re)introductions of megaherbivores or their ecological proxies. Species' traits (in this case shoulder height) may be more reliable predictors of mesoherbivores' responses to megaherbivores than phylogenetic relatedness, and may be useful for predicting responses of data-limited species.

Forest Thinning in Ponderosa Pines Increases Carbon Use Efficiency and Energy Flow From Primary Producers to Primary Consumers

AbstractA better understanding of carbon use efficiency (CUE) and carbon allocation during disturbance is critical to improve simulations of the global carbon cycle and understanding future climate impacts. Forest thinning of high‐stem density, high elevation dry western US forests is becoming more common to reduce severe fire danger but there are uncertainties about how forest thinning may impact forest CUE, carbon allocation and energy flow through the food chain. In three, quarter ha stands with similar soils, elevation and climate along a forest thinning gradient near Flagstaff (AZ), we measured total net primary production (NPP of wood, fine root, and leaves), total autotrophic respiration (Ra of wood, rhizosphere, and canopy respiration), gross primary production (GPP = NPP + Ra) and large mammal herbivory (with camera traps and dung counts) over a ∼2‐year period. We found strong seasonality in all carbon cycling variables and herbivory, peaking during the warm, wet monsoon period. Carbon was produced more efficiently in the thinned stands, with carbon use efficiency (CUE = NPP/GPP) of ∼0.63, versus the unthinned stand with CUE of 0.38. GPP was similar in the two thinned stands (∼3.5 Mg C ha−1 yr−1) but was about 30% greater in the unthinned stands (5.0 Mg C ha−1 yr−1). Finally, the thinned stand had higher understory NPP, large herbivore consumption and had triple the total energy going into primary consumers. Overall, the thinning, and the return to a more natural prefire suppression forest structure, increased the CUE and energy flow from primary producers to primary consumers.

Population, distribution, and habitat of Bornean Elephant in Tulin Onsoi, Nunukan District, Indonesia based on dung counts

Abstract. Sukmantoro W, Suyitno A, Mulyadi, Gunaryadi D, Seno A, Kusuma AI, Darwis. 2021. Population, distribution, and habitat of Bornean Elephant in Tulin Onsoi, Nunukan District, Indonesia based on dung counts. Biodiversitas 22: 311-319. The survey on population, distribution, and habitat of Bornean elephants is very important because it reduces the information gap about Bornean elephants’ population and distribution. In more detail, the study can be used for updating information and the needs of local government in a spatial plan based on biodiversity conservation. The survey of Bornean Elephant was conducted in Tulin Onsoi Subdistrict, Nunukan District, North Kalimantan Province, Indonesia, starting in February 2018 to May 2019. The survey area’s scopes are Agison, Sibuda, Apaan, and Tampilon sub-water catchment areas in 34 (5 x 5 km2) grids with a total of 850 km2. The occupancy method with perpendicular line transect was used in this study. In the survey, the number of traces was 52 finding points with a total of 241 traces. The elephant dung identified in the dung piles (one-time defecation) was in 29 finding points with a total of 38 dung piles (0.22 dung piles per km). Based on Distance 6.0 and involved the formula of the elephant population’s density with standard defecation and dung decay ratio, the elephant population density in the Tulin Onsoi is between 4.8-5.7 individuals/100 km2. Minimum convex polygon (MCP)-qHull showed that the area of ​​the elephant habitat is 253.12 km2 in Tulin Onsoi sub-district. Generally, the habitat conditions for the location are old secondary forests (37 %). Meanwhile, other habitats included in the survey area are primary forest, shrubs, and plantations, including community agriculture and roads. In the strategy of managing the Bornean elephant, efforts to stabilize or increase population are important things to do. Conservation-based spatial planning and close monitoring for the protection of small populations of this species and its threats, are options that can be selected for present and future in North Kalimantan.

The role of browsers in maintaining the openness of savanna grazing lawns

Abstract In savannas, ruminant herbivores can have divergent impacts on tree recruitment and subsequent woody cover. Whereas heavy grazing by cattle results in woody thickening, intensive grazing by wildlife instead tends to be associated with lower woody cover. To disentangle why woody cover is low in areas heavily grazed by wildlife, we investigated (a) whether grazing lawns attract indigenous mammalian browsers, and if a preference for short‐grass habitat decreases with browser body mass as predator susceptibility decreases; and (b) whether browser attraction to grazing lawns translates into the suppression of woody plants, including seedlings and saplings, thus maintaining the openness of heavily grazed short‐grass areas. In Kruger National Park, South Africa, we contrasted browser abundance (using dung counts) on grazing lawns and on low‐herbivory sites characterised by tall grass. Additionally, a herbivore exclosure experiment was set up to investigate the combined impact of browser removal and grass height habitat type on seedling survival and sapling growth of a dominant woody plant species. Finally, in Hluhluwe‐iMfolozi Park (HiP), we examined the long‐term (10 years) impact of browser removal on the growth rates of a range of woody species, monitored across ten sites along a gradient of herbivory ranging from grazing lawn to tall grass. Steenbok and impala selected short‐ over tall grass as preferred browsing sites, while elephant preferred tall grass. Browser abundance on short grass decreased with browser body mass, indicating that predator avoidance might be a key factor driving mesoherbivores to utilise grazing lawns. Seedling survival was lowest on grazing lawns when browsers were present, with mortality occurring in two out of every three seedlings. Similarly, sapling growth was lowest on grazing lawns, although browser removal had no significant effect. Evidence for increased browser impact on grazing lawns was clearest from our long‐term herbivore exclosure experiment in HiP, which demonstrated that browsers strongly modify the growth rates of woody plants in short‐grass habitats. Synthesis. These results provide support for the hypothesis that browsers, particularly browsing mesoherbivores and mixed feeders, are attracted to short‐grass habitats, and that they help maintain grazing lawn openness by suppressing seedling survival and woody plant growth where grass is kept short by grazers.

Differential herbivore occupancy of fire-manipulated savannas in the Satara region of the Kruger National Park, South Africa

The Kruger National Park’s (KNP) long-running experimental burn plots (EBPs) have a history of research projects, which improve the understanding of fire in savanna ecosystems. Using data from KNP’s aerial censuses (2005–2016) and in situ dung count data (2008–2017), this study assessed (1) herbivore densities on the Satara, N’Wanetsi and Marheya EBPs, on annual, triennial and no-burn treatments and across pre-, during and post-drought climate conditions; (2) herbivore densities of these EBPs relative to their non-manipulated surroundings and (3) the extent to which distance to water and rainfall influence ungulate densities. The results revealed that herbivore mean density differed significantly between the three EBPs of Satara and across their fire treatments. N’Wanetsi showed the highest density (0.30 animals/ha), whilst the lowest was found at Marheya (0.12 animals/ha). Overall, pre-drought density was higher on the annual plots (0.56 animals/ha), whilst higher post-drought density was evidenced on the triennial plots (0.80 animals/ha). On average, there were significantly higher herbivore densities on the EBPs (2.54 animals/ha) compared to the surrounding matrix at the larger scales of the Satara management section (0.15 animals/ha) and the central KNP (0.18 animals/ha). A positive correlation between herbivore mean density estimate and distance to water was shown. However, grazer mean density across fire treatments was strongly correlated to rainfall.Conservation implications: Given the variation in fire regimes and their application, and the non-uniform and elevated herbivore densities of the EBPs, inferences from the EBPs cannot be made to the larger KNP. The trials should rather be viewed as an isolated, fire herbivory experiment. It is also recommended to align the experiment with South African National Parks’ mandate by including biodiversity parameters like small mammals and insects in the monitoring of the plots.

Ivory Coast without ivory: Massive extinction of African forest elephants in Côte d'Ivoire.

In pre-colonial and colonial times Côte d'Ivoire probably hosted one of the largest elephant populations in West Africa, resulting in the country's name Côte d'Ivoire (in English Ivory Coast) by French settlers. Numbers declined and by the early 90s it was estimated that the total number of both savannah and forest elephants had reached 63 to 360 elephants in the entire country. Here we present updated information on the distribution and conservation status of forest elephant in Côte d'Ivoire based on multiple sources-dung counts on line transects, records of human-elephant conflict, media reports, sign and interview surveys-obtained during the period 2011-2017. We used Pearson correlation to determine the correlation between the presence of forest elephant and site variables (size of the forest, percentage of area converted into plantation, size of the forest left, size of human population inside the PA, poaching index, distance to the nearest road, population density in the Department, level of protection of the PA). To examine the effect of ecological traits on elephant extirpation, we used Principal Components Analysis (PCA) to check for multicollinearity among variables. Based on dung count elephant presence was confirmed in only 4 of the 25 protected areas surveyed. PAs with higher level of protection have higher probability to be home of elephant population. The viability of these populations is uncertain, since they have a small size and are isolated. Aggressive conservation actions including law enforcement for the protection of their remaining habitat and ranger patrolling are needed to protect the remaining forest elephant populations.

Sampling scale and season influence the observed relationship between the density of deer and questing Ixodes ricinus nymphs

BackgroundThe relationship between environmentally transmitted tick parasites, Ixodes spp., and their main reproductive host, deer, is generally thought to be positive. However, measuring host abundance and density directly can be challenging and indirect methods are often used. The observed relationship between the parasite and host may be affected by sampling scale and season, which could lead to different inferences being made. Here, we aimed to test the effect of sampling scale and season on the relationship between density of deer and the density of questing Ixodes ricinus nymphs.MethodsThe density of deer (primarily Dama dama) was estimated using line transect distance sampling of deer dung quantified in different seasons (winter and summer) and measured at three different nested scales (site, transect and observation level). Questing nymph density was measured using blanket drag methods and estimates were calculated at the same scales as deer density estimates. General linear models were used to evaluate the relationship between questing nymphs, deer density and other environmental variables at each sampling scale and each season deer density was measured at.ResultsWhile a positive relationship between deer density and questing nymph density was detected at the site and transect scale, no relationship was apparent at the observation level. This was likely due to increased variation and reduced precision of deer dung counts at the finest sampling scale. Seasonal changes in deer populations were observed likely reflecting seasonal shifts in habitat usage. The summer estimates of deer density explained questing nymph density whereas winter estimates did not.ConclusionsOur results show that the scale of sampling can affect the detectability of the positive association between host and vector species. Furthermore, such associations can be obscured if hosts exhibit seasonal changes in habitat use. Thus, both sampling scale and season are important to consider when investigating the relationship between host and vector species.

Quantifying nutrient re-distribution from nutrient hotspots using camera traps, indirect observation and stable isotopes in a miombo ecosystem, Tanzania

Nutrient hotspots strongly attract mammalian herbivores in nutrient-poor habitats such as savanna systems. However, little is known about their seasonal importance for mammalian herbivore species, particularly grazers. In addition, no study has fully quantified the potential re-distribution of nutrients into the surroundings of these hotspots. We assessed nutrient hotspot (i.e., grazing lawns and termite mounds) use by herbivores in a Miombo ecosystem of the Issa valley, Tanzania, using dung counts, camera traps and stable isotope analyses over a one year period, from May 2016 to October 2017. We conducted dung counts along four transects each radiating away from ten termite mounds and six grazing lawns as well as in 16 control sites 100 m away from each nutrient hotspot. In addition, we sprayed grasses around five termite mounds with urea and traced the isotopic signature back in grazing herbivore dung. Grazer dung deposition was twice as high in hotspot areas vs control sites. A total of 32 camera stations recorded 244 wildlife encounters, with mammalian herbivores using hotspot areas four times more frequently compared to control plots. Stable isotope analyses highlighted that dung deposited by mammalian grazers around hotspots likely originated from grasses within or close to hotspot areas, indicating that grazers are responsible for maintaining nutrient stability of these hotspots. We, therefore, emphasize the importance of grazing mammal species for the long-term persistence of hotspots and, thus, their contribution to the maintenance of a heterogeneous landscape within the Miombo ecosystem.

Savannah trees buffer herbaceous plant biomass against wild and domestic herbivores

AbstractQuestionsGiven the growing abundance and dominance of domestic herbivores in savannah ecosystems, can trees maintain plant herbaceous standing biomass under increasing herbivore pressure? Are there differences in the capacity of leguminous and non‐leguminous trees in sustaining understory herbaceous biomass? And finally, to what extent does plant community composition underneath trees modulate the effects of herbivore assemblage and abundance on herbaceous biomass?LocationPasturelands and protected areas along the borders of the Serengeti National Park, Tanzania, East Africa.MethodMonthly herbaceous biomass was monitored non‐destructively using a calibrated pasture disc. Measurements were taken within a network of paired exclosures and open plots, underneath large leguminous and non‐leguminous tree canopies and outside canopies. Herbivore community assemblage compositions and abundances were characterised using monthly dung counts, and herbaceous plant community composition was surveyed annually every wet season over two years.ResultsOverall, we found that trees promote herbaceous standing biomass, particularly in the presence of moderate herbivory rather than under herbivore exclusion. Greater herbivore abundance and livestock dominance reduced herbaceous plant biomass, but trees, particularly leguminous trees, limited these negative effects. This capacity for trees to limit the effect of herbivores was related to herbaceous plant species composition. Understory plant communities that were compositionally typical of protected areas sustained the highest plant biomass when found in pasturelands with high herbivore pressure.ConclusionOur findings give greater credence to the importance of preserving large trees in savannah landscapes increasingly dominated by high abundances of livestock. Moreover, our results highlight that park managers and pastoralists need to maintain the specialist herbaceous understory community beneath trees in order to benefit from facilitative tree–understory interactions.

Wild mammal dung abundance in Lake Mburo National Park is lower than in adjacent ranchlands

The establishment of livestock ranchlands adjacent to protected areas in savanna ecosystems is believed to threaten wild animals. Intensive competition for vegetative resources, water and poaching are considered to be immediate factors that reduce the capacity of protected areas to sustain wild mammals. The coexistence of wild mammals and ranchlands is common in Southern Africa but has rarely been suggested as a viable conservation option in East Africa. To assess the importance of ranchlands in conserving wild mammals, 36 plots of 20 × 20 m dimension were positioned along a 7240 m stretch from the boundary in Lake Mburo National Park (LMNP) and 36 plots of similar dimension were set within the ranchlands adjacent to the Park. The dung counts of different species recorded in the plots were used as a relative index of mammal abundance in the ranchlands and in LMNP. The results reveal 18 wild mammal species recorded in both sampled areas, 12 within LMNP and 17 in the adjacent ranchlands. The topi Damaliscus lunatus was only found in the park. Total dung count estimated in both ranchlands and LMNP was 2,586 with LMNP accounting for 29% and ranchlands 71%. In terms of wild mammal dung, ranchlands had a higher wild mammal dung count than LMNP (30% higher). The study points to the compatibility of the two land uses in conserving wild mammals and biodiversity in general, negating the common belief of competition and exclusion. Future research is needed on the compatibility of ranchlands with protected areas on biodiversity status of other species.

The worst drought in 50 years in a South African savannah: Limited impact on vegetation

AbstractSouth Africa experienced a severe multiyear drought from 2014 to 2016. Here, we explore the response of a South African savannah ecosystem to this drought focusing on tree and grass dynamics. We used open long‐term monitoring plots established in 2000 and distributed across broad rainfall gradients in the Hluhluwe‐iMfolozi Park in KwaZulu‐Natal. Analysis showed negligible tree mortality due to drought in 2016 (0.03%) and 2017 (0.49%). However, there was an apparent increase in the tree population especially among the small size classes (0.1–0.3 m) in 2016 and 2017 relative to the predrought 2012 census. Drought effects may be confounded with changes in browser populations. The impala population declined in a mesic savannah (Hluhluwe), as measured with dung counts; however, this decline started before the drought. Impala decline in a semi‐arid savannah (iMfolozi) was more coincident with drought. Grass biomass and cover decreased in 2016 compared to predrought 2012 but showed rapid recovery once rains began. In iMfolozi grass species, composition improved from a grazing perspective as a result of the recovery of the decreaser species, an increase in palatable species and a marked decline of unpalatable species. The minor changes in woody plants and grasses from before the drought until rain resumed and the rapid recovery of grasses suggest that this South African savannah ecosystem was resilient to severe drought.

Estimating Population Density of the White-Tailed Deer in Finland using Non-Invasive Genetic Sampling and Spatial Capture–Recapture

The white-tailed deer is an important game species in Finland. We evaluated the potential of estimating the white-tailed deer pre-harvest density using non-invasive DNA collection within a spatial capture–recapture (SCR) framework. We sampled faeces during three weekly visits in autumn 2015 from 180, 20 × 20 m plots clustered in groups of four. Individual identification was based on 12–14 microsatellites. Of the 245 faecal samples collected, an individual could be identified from only 36 (15%). We identified 27 white-tailed deer individuals of which seven were recaptured. The SCR model produced a plausible density estimate (3.5 indiv. km–2) which was similar to estimates based on dung count and large-scale national estimates, although a posteriori simulation showed the SCR estimate was likely positive biased. Although we found that SCR based on faecal DNA can provide pre-harvest density estimates of the white-tailed deer, the approach is not without challenges and we discuss these suggesting possible solutions.

Drought-response strategies of savanna herbivores.

Climate models predict increases in drought frequency and severity worldwide, with potential impacts on diverse systems, including African savannas. These droughts pose a concern for the conservation of savanna mammal communities, such that understanding how different species respond to drought is vital.Because grass decreases so consistently during droughts, we predict that grass‐dependent species (grazers and mixed feeders) will respond strongly to drought, whether by changing diets, seeking drought refugia, or suffering mortality.A recent severe but heterogeneous drought in Kruger National Park, South Africa, afforded a rare opportunity to test these hypotheses in situ—crucial, given the central role of landscape‐scale movement as a potential herbivore strategy. We used herbivore dung as a proxy, integrating spatial distributions (dung counts) with diet composition (carbon isotope analysis of dung).As predicted, browsers showed little response to drought. However, mixed feeders switched their diets to incorporate more C3 trees/forbs, but did not move. Meanwhile, grazers and megaherbivores instead moved toward drought refugia. Synthesis and applications: The responses we observed by savanna herbivores are largely amplifications of typical dry season strategies and reflect constraints imposed by body size and feeding ecology. Grazers may be at particular risk from increased drought frequency and spatial extent if drought refugia become decreasingly available. Conservation strategies should recognize these constraints and work to facilitate the diverse responses of herbivores to drought.