Kimuyu D.M.,Karatina University |
Kimuyu D.M.,Mpala Research Center |
Sensenig R.L.,Mpala Research Center |
Sensenig R.L.,Goshen College |
And 6 more authors.
Ecological Applications | Year: 2014
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 treatment plots of the Kenya Long-term Exclosure Experiment (KLEE), where experimentally excluding elephants has resulted in 42% greater tree densities. The KLEE design includes six different herbivore treatments that allowed us to examine how different combinations of megaherbivore wildlife, mesoherbivore wildlife, and cattle affect fire temperatures and subsequent loss of ant symbionts from Acacia trees. Before burning, we quantified herbaceous fuel loads and plant community composition. We tagged all trees, measured their height and basal diameter, and identified the resident ant species on each. We recorded weather conditions during the burns and used ceramic tiles painted with fire-sensitive paints to estimate fire temperatures at different heights and in different microsites (under vs. between trees). Across all treatments, fire temperatures were highest at 0-50 cm off the ground and hotter in the grass under trees than in the grassy areas between trees. Plots with more trees burned hotter than plots with fewer trees, perhaps because of greater fine woody debris. Plots grazed by wildlife and by cattle prior to burning had lower herbaceous fuel loads and experienced lower burn temperatures than ungrazed plots. Many trees lost their ant colonies during the burns. Ant survivorship differed by ant species and at the plot level was positively associated with previous herbivory (and lower fire temperatures). Across all treatments, ant colonies on taller trees were more likely to survive, but even some of the tallest trees lost their ant colonies. Our study marks a significant step in understanding the mechanisms that underlie the interactions between fire and herbivory in savanna ecosystems. © 2014 by the Ecological Society of America.
Allert A.L.,U.S. Geological Survey |
Distefano R.J.,Conservation Research Center |
Fairchild J.F.,U.S. Geological Survey |
Schmitt C.J.,U.S. Geological Survey |
And 4 more authors.
Ecotoxicology | Year: 2013
The Big River (BGR) drains much of the Old Lead Belt mining district (OLB) in southeastern Missouri, USA, which was historically among the largest producers of lead-zinc (Pb-Zn) ore in the world. We sampled benthic fish and crayfish in riffle habitats at eight sites in the BGR and conducted 56-day in situ exposures to the woodland crayfish (Orconectes hylas) and golden crayfish (Orconectes luteus) in cages at four sites affected to differing degrees by mining. Densities of fish and crayfish, physical habitat and water quality, and the survival and growth of caged crayfish were examined at sites with no known upstream mining activities (i.e., reference sites) and at sites downstream of mining areas (i.e., mining and downstream sites). Lead, zinc, and cadmium were analyzed in surface and pore water, sediment, detritus, fish, crayfish, and other benthic macro-invertebrates. Metals concentrations in all materials analyzed were greater at mining and downstream sites than at reference sites. Ten species of fish and four species of crayfish were collected. Fish and crayfish densities were significantly greater at reference than mining or downstream sites, and densities were greater at downstream than mining sites. Survival of caged crayfish was significantly lower at mining sites than reference sites; downstream sites were not tested. Chronic toxic-unit scores and sediment probable effects quotients indicated significant risk of toxicity to fish and crayfish, and metals concentrations in crayfish were sufficiently high to represent a risk to wildlife at mining and downstream sites. Collectively, the results provided direct evidence that metals associated with historical mining activities in the OLB continue to affect aquatic life in the BGR. © 2013 Springer Science+Business Media New York (outside the USA).
Young H.C.,University of Calgary |
Reid T.G.,SNC - Lavalin |
Randall L.A.,Conservation Research Center |
Lachowsky L.E.,University of Calgary |
And 4 more authors.
International Journal of Zoology | Year: 2013
We propose that changes in movement behavior may be a proximate mechanism that influences the accumulation of animals at habitat edges. We tested this idea with a combination of empirical and simulation experiments in a resource-free landscape. The movements of individual flour beetles, Tribolium confusum, were tracked across a paper arena edged with invisible tape until beetles crossed the edge. Movement behavior (step lengths and turn angles) and cumulative occupancy were analyzed according to distance from the edge. We found that beetles took smaller steps with larger turn angles near edges than in the center of the arena and that beetle distribution was highly biased towards the edge of the arena. We then tested two agent-based simulation models for each beetle: an edge-independent model and an edge-dependent model. Both models predicted less time spent at the edge than was observed. The proportion of time spent at edges depended on the propensity to cross the edge, which could not be explained by beetle body size or energetic condition. The distribution of animals with respect to habitat edges depends on many factors, but we suggest that proximate mechanisms such as movement behavior should be explicitly considered when interpreting animal distributions. © 2013 Hilary C. Young et al.
Hansen C.P.,University of Missouri |
Renken R.B.,Conservation Research Center |
Millspaugh J.J.,University of Missouri
River Research and Applications | Year: 2012
During the previous century, the wetland area in the lower Missouri River alluvial valley was reduced by 39% because of river channelization and bank stabilization projects. The Great Flood of 1993 reversed the trend of wetland loss by creating 466 new wetlands in the alluvial valley between Kansas City and St. Louis, Missouri. We estimated amphibian occupancy, detection probability and number of species exhibiting evidence of reproduction in eight flood-created and 16 pre-flood existing wetlands from 1996 through 1998. We also evaluated whether hydroperiod (the number of days any water was present in a wetland from 20 February through 31 August) and distance to river predicted those values. Detection probabilities for adult amphibian species were relatively constant across years and ranged from 0.013 [Great Plains toad (Anaxyrus cognatus)] to 0.280 [Woodhouse's toad (Anaxyrus woodhousii woodhousii)]. Occupancy of adult amphibians differed across years and was not correlated with habitat features. Estimated occupancy probabilities for amphibian species ranged from 0.126 [Plains spadefoot (Spea bombifrons)] to 0.896 [boreal chorus frog (Pseudacris maculata)]. Almost double the number of amphibian species showed evidence of reproduction in existing wetlands (wetlands created before the Great Flood of 1993) when compared with that in flood-created wetlands. Similarly, temporary wetlands had nearly double the number of amphibian species showing evidence of reproduction when compared with permanent wetlands. Finally, the highest number of species showed evidence of reproduction in wetlands with spring-summer hydroperiods between 135 and 140days. All these relationships suggest that the invasion and persistence of predators in wetlands negatively influence amphibian reproduction. If the Missouri River is allowed to reconnect with the alluvial valley, more predators may be introduced into wetlands, leading to reduced amphibian occupancy and reproduction. However, this connection will not likely occur over the entire alluvial valley and, therefore, should not adversely impact amphibians that find refuge in higher-elevation, non-connected regions of the alluvial valley. © 2011 John Wiley & Sons, Ltd.
Kitchen N.R.,University of Missouri |
Blanchard P.E.,Conservation Research Center |
Lerch R.N.,University of Missouri
Journal of Environmental Quality | Year: 2015
Nitrogen from agriculture is known to be a primary source of groundwater NO3-N. Research was conducted in a northeastern Missouri watershed to assess the impact of cropping systems on NO3-N for a loess and fractured glacial till aquifer underlying claypan soils. Three cropped fields with 10 yr of similar management were each instrumented with 20 to 25 monitoring wells, 3 to 15 m in depth, in 1991 to 1992. Wells were sampled and analyzed for NO3-N at least annually from 1991 to 2004. Initial NO3-N concentrations were variable, ranging from undetectable to > 24 mg L-1 but averaged 7.0 mg L-1. Groundwater NO3-N was significantly higher in Field 3, probably the result of concurrent applications of manure and N fertilizer before 1980. Overall changes in NO3-N levels in Fields 1 and 2 were generally small; however, NO3-N levels for Field 3 have decreased an average of 0.28 mg L-1 yr-1. Excessive loading of N into the matrix of the glacial till may have had a long-term impact on NO3-N for this field. Despite the presence of dissolved O2 in the aquifer, evidence of denitrification in some upper-landscape groundwater wells was found. The greatest decreases in NO3-N concentration occurred as groundwater moved through an in-field tree line or through a riparian zone. While overall conclusions were complicated by the long-term impact of past management, the capacity of the till to buffer changes, hydrogeologic variability found among wells, and the activity of biological processes, we conclude that cropping practices during this study did not increase glacial till NO3-N. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.
PubMed | Conservation & Research Center
Type: Journal Article | Journal: Zoo biology | Year: 2010
Surveys are being conducted to monitor the reproductive health of elephants managed by the TAG/SSP. This study summarizes results of a 2005 survey and compares data to one conducted in 2002. Surveys were returned for 100% and 79.0% of Asian and African elephants, respectively. Of those, 79.3% of Asian and 92.1% of African elephants had weekly progestagen data to assess ovarian cyclicity. For Asian elephants, acyclicity rates were similar between the 2002 and 2005 surveys (13.3% versus 10.9%), whereas irregular cycling increased in 2005 (2.6% versus 7.6%), respectively. For African elephants, the percentages of both acyclicity (22.0% versus 31.2%) and irregular cycling females (5.2% versus 11.8%) increased. In both species, ovarian inactivity was more prevalent in the older age categories (>30 years of age), but for African elephants also occurred in the reproductive aged groups. Reproductive tract pathologies did not account for the majority of acyclicity problems. Several females changed cyclicity status between the two surveys, including from noncycling to cycling, suggesting this is not an irreversible condition. However, seven African females went from cycling to abnormal or no cyclic activity. In summary, the incidence of ovarian acyclicity in Asian elephants is low and stable, but appears to be increasing in African females. These findings reinforce the need for long-term reproductive monitoring programs and continuous reproductive surveys, even for females not being considered for breeding. With more data we hope to determine what factors are related to changes in ovarian status and how to reverse the trend towards acyclicity.
PubMed | Conservation & Research Center
Type: Journal Article | Journal: Zoo biology | Year: 2010
Over a third of captive female African elephants in North America fail to exhibit normal estrous cycles based on long-term serum progestagen analyses. Why acyclicity occurs is unknown; however, the majority of noncycling females are ranked by keepers as the dominant individual within the group. To investigate the relationship between ovarian cyclicity status and keeper-determined social rank, observations were conducted on 33 female African elephants (18 cycling, 15 noncycling). Based on keeper evaluations, five cycling elephants were ranked dominant, seven in the middle and six as subordinate. In contrast, 10 noncycling elephants were ranked as dominate and five as subordinate with none ranked as middle. When comparing the behavior of the elephants by their keeper-determined rank, the dominant females dominant were significantly more likely to approach, displace and push. Similarly, keeper-determined subordinate females more frequently presented their hind end and held their ears erect. Behaviors initiated by one elephant toward another did not vary between cycling and noncycling females, except when the interaction with social rank was tested. Dominant, noncycling females initiated a higher percentage of approach and displace behaviors than both cycling and noncycling, subordinate elephants. Subordinate, noncycling elephants displayed the highest percentage of ears erect. Social rank drives the interactions of ex situ female African elephants more than ovarian cyclicity status. Thus, behavioral interactions cannot be used to predict which cycling elephants are most likely to become acyclic.