More Like this

1. Less Is More: Lowering Cattle Stocking Rates Enhances Wild Herbivore Habitat Use and Cattle Foraging Efficiency

   https://doi.org/10.3389/fevo.2022.825689  

   Wells, Harry B.; Crego, Ramiro D.; Ekadeli, Jackson; Namoni, Mathew; Kimuyu, Duncan M.; Odadi, Wilfred O.; Porensky, Lauren M.; Dougill, Andrew J.; Stringer, Lindsay C.; Young, Truman P. (February 2022, Frontiers in Ecology and Evolution)

   Over a quarter of the world’s land surface is grazed by cattle and other livestock, which are replacing wild herbivores and widely regarded as drivers of global biodiversity declines. The effects of livestock presence versus absence on wild herbivores are well documented. However, the environmental context-specific effects of cattle stocking rate on biodiversity and livestock production are poorly understood, precluding nuanced rangeland management recommendations. To address this, we used a long term exclosure experiment in a semi-arid savanna ecosystem in central Kenya that selectively excludes cattle (at different stocking rates), wild mesoherbivores, and megaherbivores. We investigated the individual and interactive effects of cattle stocking rate (zero/moderate/high) and megaherbivore (>1,000 kg) accessibility on habitat use (measured as dung density) by two dominant wild mesoherbivores (50–1,000 kg; zebra Equus quagga and eland Taurotragus oryx ) across the “wet” and “dry” seasons. To explore potential tradeoffs or co-benefits between cattle production and wildlife conservation, we tested for individual and interactive effects of cattle stocking rate and accessibility by wild mesoherbivores and megaherbivores (collectively, large wild herbivores) on the foraging efficiency of cattle across both seasons. Eland habitat use was reduced by cattle at moderate and high stocking rates across both dry and wet seasons and regardless of megaherbivore accessibility. We observed a positive effect of megaherbivores on zebra habitat use at moderate, but not high, stocking rates. Cattle foraging efficiency (g dry matter step –1 min –1 ) was lower in the high compared to moderate stocking rate treatments during the dry season, and was non-additively reduced by wild mesoherbivores and high cattle stocking rates during the wet season. These results show that high stocking rates are detrimental to wild mesoherbivore habitat use and cattle foraging efficiency, while reducing to moderate stocking rates can benefit zebra habitat use and cattle foraging efficiency. Our findings demonstrate that ecosystem management and restoration efforts across African rangelands that involve reducing cattle stocking rates may represent a win-win for wild herbivore conservation and individual performance of livestock. 

   more » « less
2. The meta-gut: community coalescence of animal gut and environmental microbiomes

   https://doi.org/10.1038/s41598-021-02349-1  

   Dutton, Christopher L.; Subalusky, Amanda L.; Sanchez, Alvaro; Estrela, Sylvie; Lu, Nanxi; Hamilton, Stephen K.; Njoroge, Laban; Rosi, Emma J.; Post, David M. (November 2021, Scientific Reports)

   Abstract All animals carry specialized microbiomes, and their gut microbiota are continuously released into the environment through excretion of waste. Here we propose themeta-gutas a novel conceptual framework that addresses the ability of the gut microbiome released from an animal to function outside the host and alter biogeochemical processes mediated by microbes. We demonstrate this dynamic in the hippopotamus (hippo) and the pools they inhabit. We used natural field gradients and experimental approaches to examine fecal and pool water microbial communities and aquatic biogeochemistry across a range of hippo inputs. Sequencing using 16S RNA methods revealed community coalescence between hippo gut microbiomes and the active microbial communities in hippo pools that received high inputs of hippo feces. The shared microbiome between the hippo gut and the waters into which they excrete constitutes ameta-gutsystem that could influence the biogeochemistry of recipient ecosystems and provide a reservoir of gut microbiomes that could influence other hosts. We propose thatmeta-gutdynamics may also occur where other animal species congregate in high densities, particularly in aquatic environments. 

   more » « less
3. Wild and domestic savanna herbivores increase smaller vertebrate diversity, but less than additively

   https://doi.org/10.1111/1365-2664.13843  

   Wells, Harry B. M.; Kimuyu, Duncan M.; Odadi, Wilfred O.; Dougill, Andrew J.; Stringer, Lindsay C.; Young, Truman P.; du Toit, ed., Johan (February 2021, Journal of Applied Ecology)

   Abstract Cattle and other livestock graze more than a quarter of the world's terrestrial area and are widely regarded to be drivers of global biodiversity declines. Studies often compare the effects of livestock presence/absence but, to our knowledge, no studies have tested for interactive effects between large wild herbivores and livestock at varying stocking rates on small‐bodied wild vertebrates.We investigated the effects of cattle stocking rates (none/moderate/high) on the diversity of wildlife 0.05–1,000 kg using camera traps at a long‐term exclosure experiment within a semi‐arid savanna ecosystem in central Kenya. In addition, by selectively excluding wild ‘mesoherbivores’ (50–1,000 kg) and ‘megaherbivores’ (>1,000 kg; elephant and giraffe), we tested whether the presence of these two wild herbivore guilds (collectively, ‘larger wild herbivores’) mediates the effect of cattle stocking rate on habitat use and diversity of ‘smaller wildlife’ (mammals ranging between 10 and 70 cm shoulder height and birds).Our results show that cattle enhance alpha diversity of smaller wildlife (with or without larger wild herbivore presence) and of all wildlife 0.05–1,000 kg (with or without megaherbivore presence), by altering vegetation structure. However, for smaller wildlife, this effect is less pronounced in the presence of larger wild herbivores, which also shorten grass. In the absence of cattle, mesoherbivore‐accessible sites showed higher alpha diversity of smaller wildlife than sites excluding mesoherbivores.Smaller wildlife habitat use was increased by high cattle stocking rates and wild mesoherbivores more in the presence of the other.Synthesis and applications. Our findings imply that grazing, whether by livestock or wildlife, can enhance local savanna wildlife diversity. The biodiversity benefits of localised increases in herbivory are likely to be due to shortened grass and associated visibility improvements (for predator avoidance/foraging). This suggests that land managers can increase local biodiversity by shortening grass, with wild or domestic herbivores (or both), at least in patches within a taller grass matrix. 

   more » « less
4. Browsing wildlife and heavy grazing indirectly facilitate sapling recruitment in an East African savanna

   https://doi.org/10.1002/eap.2399  

   LaMalfa, Eric M.; Riginos, Corinna; Veblen, Kari E. (July 2021, Ecological Applications)

   Abstract Management of tree cover, either to curb bush encroachment or to mitigate losses of woody cover to over‐browsing, is a major concern in savanna ecosystems. Once established, trees are often “trapped” as saplings, since interactions among disturbance, plant competition, and precipitation delay sapling recruitment into adult size classes. Saplings can be directly suppressed by wildlife browsing and competition from adjacent plants, and indirectly facilitated by grazers, such as cattle, which feed on neighboring grasses. Yet few experimental studies have simultaneously quantified the effects of cattle and wildlife on sapling growth, particularly over long time scales. We used a series of replicated 4‐ha herbivore‐manipulation plots to investigate the net effects of wildlife and moderate cattle grazing onAcacia drepanolobiumsapling growth over 10 years that encompassed extended wet and dry periods. We also simulated more intense cattle grazing using grass removal treatments (0.5‐m radius around saplings), and we quantified the role of intraspecific tree competition using neighborhood tree surveys (trees within a 3‐m radius). Wildlife, which included elephants, had a positive effect on sapling growth. Wildlife also reduced neighbor tree density during the 10‐yr study, which likely caused the positive effect of wildlife on saplings. Although moderate cattle grazing did not affect sapling growth, grass removal treatments simulating heavy grazing increased sapling growth. Both grass removal and neighbor tree effects on saplings were strongest during above‐average rainfall years following drought. This highlights that livestock‐driven reductions in grass cover and catastrophic wildlife damage to trees during droughts present a need, or an opportunity, for targeted management of sapling growth and woody plant cover during ensuing wet periods. 

   more » « less
5. Cryptic Constituents: The Paradox of High Flux–Low Concentration Components of Aquatic Ecosystems

   https://doi.org/10.3390/w13162301  

   Olofsson, Malin; Power, Mary E.; Stahl, David A.; Vadeboncoeur, Yvonne; Brett, Michael T. (August 2021, Water)

   The interface between terrestrial ecosystems and inland waters is an important link in the global carbon cycle. However, the extent to which allochthonous organic matter entering freshwater systems plays a major role in microbial and higher-trophic-level processes is under debate. Human perturbations can alter fluxes of terrestrial carbon to aquatic environments in complex ways. The biomass and production of aquatic microbes are traditionally thought to be resource limited via stoichiometric constraints such as nutrient ratios or the carbon standing stock at a given timepoint. Low concentrations of a particular constituent, however, can be strong evidence of its importance in food webs. High fluxes of a constituent are often associated with low concentrations due to high uptake rates, particularly in aquatic food webs. A focus on biomass rather than turnover can lead investigators to misconstrue dissolved organic carbon use by bacteria. By combining tracer methods with mass balance calculations, we reveal hidden patterns in aquatic ecosystems that emphasize fluxes, turnover rates, and molecular interactions. We suggest that this approach will improve forecasts of aquatic ecosystem responses to warming or altered nitrogen usage. 

   more » « less