Duncan M KimuyuKaratina University · Natural Resource Management
Duncan M Kimuyu
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37
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Publications (37)
Ecological stability in plant communities is shaped by bottom-up processes like environmental resource fluctuations and top-down controls such as herbivory, each of which have demonstrated direct effects but may also act indirectly by altering plant community dynamics. These indirect effects, called biotic stability mechanisms, have been studied ac...
Do hotspots of plant biodiversity translate into hotspots in the abundance and diversity of large mammalian herbivores? A common expectation in community ecology is that the diversity of plants and animals should be positively correlated in space, as with the latitudinal diversity gradient and the geographic mosaic of biodiversity. Whether this pat...
Analysing temporal patterns in plant communities is extremely important to quantify the extent and the consequences of ecological changes, especially considering the current biodiversity crisis. Long‐term data collected through the regular sampling of permanent plots represent the most accurate resource to study ecological succession, analyse the s...
Fire, herbivores, and climatic factors are all major drivers of savanna and grassland dynamics, and they interact in complex ways, which are still in the process of being explored. In particular, herbivores can reduce fire intensity by removal of biomass, and this could be reinforced by herbivores’ attraction to recently burned sites, although gras...
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 o...
• Fire is a major selective force on arid grassland communities, favoring traits such as the smoke-induced seed germination response seen in a wide variety of plant species. However, little is known about the relevance of smoke as a cue for plants beyond the seedling stage.
• We exposed a fire-adapted savanna tree, Vachellia (=Acacia) drepanolobium...
Key message
The high mortality and low recruitment of the myrmecophytic Acacia drepanolobium are not consistent with the demographic rates of monodominant species. The positive conspecific density dependence observed from the spatial analysis is consistent with the defensive benefits conferred by symbiotic ants to trees when they grow close to each...
Analysing temporal patterns in plant communities is extremely important to quantify the extent and the consequences of ecological changes, especially considering the current biodiversity crisis. Long-term data collected through the regular sampling of permanent plots represent the most accurate resource to study ecological succession, analyse the s...
The extinction of 80% of megaherbivore (>1,000 kg) species towards the end of the Pleistocene altered vegetation structure, fire dynamics, and nutrient cycling worldwide. Ecologists have proposed (re)introducing megaherbivores or their ecological analogues to restore lost ecosystem functions and reinforce extant but declining megaherbivore populati...
Both termites and large mammalian herbivores (LMH) are savanna ecosystem engineers that have profound impacts on ecosystem structure and function. Both of these savanna engineers modulate many common and shared dietary resources such as woody and herbaceous plant biomass, yet few studies have addressed how they impact one another. In particular, it...
Excluding large native mammals is an inverse test of rewilding. A 25-year exclosure experiment in an African savanna rangeland offers insight into the potentials and pitfalls of the rewilding endeavor as they relate to the native plant community. A broad theme that has emerged from this research is that entire plant communities, as well as individu...
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 stock...
Both termites and large mammalian herbivores (LMH) are savanna ecosystem engineers that have profound impacts on ecosystem structure and function. Both of these savanna engineers modulate many common and shared dietary resources such as woody and herbaceous plant biomass, yet few studies have addressed how they impact one another. In particular, it...
Understanding animals’ use of space can shed valuable light on multiple other aspects of behavioral ecology, including social organization, dispersal, and foraging efficiency. Home ranges, territories, core areas, and home range overlaps have been widely studied, but unless animals are directly observed or are tracked remotely on a fine temporal sc...
Grassland and savanna ecosystems, important for both livelihoods and biodiversity conservation, are strongly affected by ecosystem drivers such as herbivory, fire, and drought. Interactions among fire, herbivores and vegetation produce complex feedbacks in these ecosystems, but these have rarely been studied in the context of fuel continuity and re...
Effects of large mammalian herbivores on woody vegetation tend to be heterogeneous in space and time, but the factors that drive such heterogeneity are poorly understood. We examined the influence of fine‐scale habitat heterogeneity on the distribution and browsing effects of two of the largest African terrestrial mammals, the elephant and giraffe....
Background
An estimated 59,000 people die from rabies annually, with 99% of those deaths attributable to bites from domestic dogs (Canis lupus familiaris). This preventable Neglected Tropical Disease has a large impact across continental Africa, especially for rural populations living in close contact with livestock and wildlife. Mass vaccinations...
Wild herbivore populations are declining in many African savannas, which is related to replacement by livestock (mainly cattle) and the loss of megaherbivores. Although some livestock management practices may be compatible with the conservation of native savanna biodiversity, the sustainability of these integrated wild herbivore/livestock managemen...
1.Savanna tree cover is dynamic due to disturbances such as fire and herbivory. Frequent fires can limit a key demographic transition from sapling to adult height classes in savanna trees. Saplings may be caught in a ‘fire trap’, wherein individuals repeatedly resprout following fire top‐kill events. Saplings only rarely escape the cycle by attaini...
On rangelands worldwide, cattle interact with many forms of biodiversity, most obviously with vegetation and other large herbivores. Since 1995, we have been manipulating the presence of cattle, mesoherbivores, and megaherbivores (elephants and giraffes) in a series of eighteen 4-ha (10-acre) plots at the Kenya Long-term Exclosure Experiment. We re...
Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint wer...
African savannas support an iconic fauna, but they are undergoing large-scale population declines and extinctions of large (>5 kg) mammals. Long-term, controlled, replicated experiments that explore the consequences of this defaunation (and its replacement with livestock) are rare. The Mpala Research Centre in Laikipia County, Kenya, hosts three su...
Although disturbance theory has been recognized as a useful framework in examining the stability of ant-plant mutualisms, very few studies have examined the effects of fire disturbance on these mutualisms. In myrmecophyte-dominated savannas, fire and herbivory are key drivers that could influence ant-plant mutualisms by causing complete colony mort...
Both wild and prescribed fire in savanna ecosystems influence habitat use by herbivores by creating or maintaining spatial and temporal heterogeneity in forage quality and vegetation cover. Yet little is known about how spatial scales influence long-term persistence of fire effects. We examined changes over a 6-year period in herbivore preference f...
In many savanna ecosystems worldwide, livestock share the landscape and its resources with wildlife. The nature of interactions between livestock and wildlife is a subject of considerable interest and speculation, yet little controlled experimental research has been carried out. Since 1995, we have been manipulating the presence and absence of catt...
Prescribed burning is used in tropical savannas to improve habitat conditions for domestic and wild herbivores, but its effects on the ecological interactions between these herbivore guilds have never been assessed experimentally. Understanding such effects will contribute towards more informed management of both guilds in landscapes where they sha...
Disturbance is a crucial determinant of animal abundance, distribution, and community structure in many ecosystems, but ways in which multiple disturbance types interact remain poorly understood. The effects of multiple-disturbance interactions can be additive, sub-additive, or super-additive (synergistic). Synergistic effects in particular can acc...
Background / Purpose:
Discourse around the understanding and management of rangelands often centers around the fundamental question as to whether domestic ungulates compete with wild ungulates. Yet few studies have attempted replicated experimental manipulations to test the exact nature of these interactions. This study summarizes lessons from 18...
Despite the importance of fire and herbivory in structuring savanna systems, few replicated experiments have examined the interactive effects of herbivory and fire on plant dynamics. In addition, the effects of fire on associated ant-tree mutualisms have been largely unexplored. We carried out small controlled burns in each of 18 herbivore treatmen...
Despite the importance of fire and herbivory in structuring savanna systems, few replicated experiments have examined the interactive effects of herbivory and fire on plant dynamics. In addition, the effects of fire on associated ant-tree mutualisms have been largely unexplored. We carried out small controlled burns in each of 18 herbivore treatmen...
Euclea divinorum, a fast establishing, unpalatable, and fire resistant bush is considered an invasive species in some parts of its range. In Ol Pejeta Conservancy (OPC), Kenya, E. divinorum bushes cover ˜27% of the total area (˜9470 ha.) and has been expanding in coverage and encroaching into A. drepanolobium woodlands, a key woody habitat for the...
Although livestock and wildlife share most of their ranges worldwide, little controlled experimental research has been done on their interactions. Since 1995 we have been manipulating the presence of cattle and large wild ungulates in a Kenyan savanna rangeland in order to better understand the nature of competition and coexistence between these tw...
Background/Question/Methods
The African savanna biome supports a higher diversity of herbivore species than is found in any other biome or continent. In order to maintain the habitats necessary to support a large diversity of wildlife species, much emphasis has traditionally been placed on the role of fire as a management tool. We hypothesize tha...
Data collected on a free ranging group of Tana River mangabeys (Cercocebus galeritus) indi-cates that this endangered primate species, which has previously been regarded as a seed predator, plays an important role in seed dis-persal and do contribute to the regeneration of a highly fragmented gallery forest. We observed fruit handling behavior and...
Survival and recruitment of the whistling thorn (Acacia drepanolobium Sjøstedt) seedlings was studied in Olpejeta Conservancy, Kenya, between 1999 and 2009. Seedlings were monitored for damage by drought and herbivores as well as survival and recruitment into adult trees. We determined variability in seedling damage, survival and recruitment before...
Questions
Questions (2)
Could someone point to me literature that examines how long after a single savanna burn do the effects of fire (especially herbivore preferences) last? What is the longest recorded time?
For how many years after a single savanna burn do the effects of fire (especially herbivore preferences) last?
Projects
Projects (3)
Dr. Kari Veblen, Dr. Corinna Riginos, and Dr. Truman Young are carrying out a long-term, large-scale herbivore exclusion experiment in Laikipia, Kenya. On arid and semi-arid range lands worldwide, livestock share the landscape with native plant and animal biodiversity. Much of this land suffers from degradation caused by inappropriate land management. Although there has been considerable research on the effects of stocking densities on range ecosystems, there has been relatively little research on the separate and combined effects of different herbivore guilds on each other and on the vegetation they share. As the value of biodiversity climbs, and the profitability of livestock production declines, we are seeking more innovative ways to manage and restore these landscapes. In 1995, we established 18 four-hectare exclosures that allow herbivory by six different combinations of cattle, wildlife, and mega-herbivores (elephants and giraffes). Along with our students and collaborators, we are monitoring soil, microbial, plant, invertebrate, and vertebrate responses to these experimental treatments. These exclosures also allow us to address fundamental issues in ecology, including induced defense, compensation, and competition.
