Estimating elephant density using motion-sensitive cameras: challenges, opportunities, and parameters for consideration

With extinction rates far exceeding the natural background rate, reliable monitoring of wildlife populations has become crucial for adaptive management and conservation. Robust monitoring is often labor intensive with high economic costs, particularly in the case of those species that are subject to illegal poaching, such as elephants, which require frequent and accurate population estimates over large spatial scales. Dung counting methods are commonly employed to estimate the density of elephants; however, in the absence of a full survey calibration, these can be unreliable in heterogeneous habitats where dung decay rates may be highly variable. We explored whether motion-sensitive cameras offer a simple, lower cost, and reliable alternative for monitoring in challenging forest environments. We estimated the density of African savanna elephants (Loxodanta africana) in a montane forest using the random encounter model and assessed the importance of surveying parameters for future survey design. We deployed motion-sensitive cameras in 65 locations in the Aberdare Conservation Area in Kenya during June to August in 2015 to 2017, for a survey effort of 967 days, and a mean encounter rate of 0.09 ± 0.29 (SD) images/day. Elephants were captured in 16 locations. Density estimates varied between vegetation types, with estimates ranging from 6.27/km2 in shrub, 1.1/km2 in forest, 0.53/km2 in bamboo (Yushania alpine), and 0.44/km2 in the moorlands. The average speed of animal movement and the camera detection zone had the strongest linear associations with density estimates (R = −0.97). The random encounter model has the potential to offer an alternative, or complementary method within the active management framework for monitoring elephant populations in forests at a relatively low cost

Rapid development of individual identification and presence systems for a critically endangered antelope, the Mountain bongo

Monitoring of species, particularly remnant populations requiring urgent conservation is often hampered by the lack of reliable tools for individual identification (using images or their spoor). Here, we develop rapid monitoring tools for individual animals of the Mountain bongo (Tragelaphus eurycerus isaaci), a critically endangered subspecies of the bongo only found in Kenya. We developed and tested an individual identification system using camera trap footage, as well as a quantitative tool to identify bongo spoor in the field, both useable by naïve observers. We implemented an information content approach to assess the importance of different visual elements in 61 individual bongos to optimise our identification system. We tested the reliability of the system with 15 naïve observers. We conclude that an optimal identification system should rely on three main visual features (stripe pattern, facial markings and horns appearance). We show that reliability amongst observers is high (κ = 0.64). We also developed a field scheme to identify footprint and spoor sign. Measurements of bongo footprints were compared with those of waterbuck (Kobus ellypsiprimnus), a syntopic antelope. Confusion occurs between spoor and footprints of both species. We find that differences in the aspect ratio of bongo and waterbuck footprints can identify the two species, 1.22 (±0.08) for bongo and 1.49 (±0.10) for waterbuck. The acquisition of reliable tools ensures monitoring activities are less dependent on individual expertise, which will allow consistent monitoring of bongo remnant populations in the future. The methods we used to develop these monitoring tools can help managers and field workers in the study of this and similar rare species where monitoring is a challenge

Corrigendum: Three spatially separate records confirm the presence of and provide a range extension for the giant pangolin Smutsia gigantea in Kenya (Oryx (2022) DOI: 10.1017/S0030605322000126)

In the original publication of this article, the list of authors was incomplete, with only the following authors listed: Tommy Sandri, Claire Okell, Stuart Nixon, Naomi Matthews, Fred Omengo, James Mathenge, Stephen Ndambuki, Daniel W.S. Challender and Bradley Cain. The correct author list is: Tommy Sandri, Claire Okell, Stuart Nixon, Naomi Matthews, Fred Omengo, James Mathenge, Stephen Ndambuki, Daniel W.S. Challender, Richard Chepkwony, Patrick Omondi, Shadrack Ngene and Bradley Cain The article has been updated to include the correct author details and add the ORCID iD of Shadrack Ngene

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Shifts in the carbon dynamics in a tropical lowland river system (Tana River, Kenya) during flooded and non-flooded conditions

Rivers transport sediment and carbon (C) from the continents to the ocean, whereby the magnitude and timing of these fluxes depend on the hydrological regime. We studied the sediment and carbon dynamics of a tropical river system at two sites along the lower Tana River (Kenya), separated by a 385 km stretch characterized by extensive floodplains, to understand how the river regime affects within-river C processing as well as the C exchange between floodplain and river. Sampling took place during three different wet seasons (2012–2014), with extensive flooding during one of the campaigns. We measured the suspended sediment concentration, the concentration and stable isotope signature of three different carbon species (particulate and dissolved organic carbon, POC and DOC, and dissolved inorganic carbon, DIC) and other auxiliary parameters. During non-flooded conditions, the total C flux was dominated by POC (57–72%) and there was a downstream decrease of the total C flux. DIC was dominating during the flooded season (56–67%) and the flux of DIC and DOC coming from the inundated floodplains resulted in a downstream increase of the total carbon flux. Our data allowed us to construct a conceptual framework for the C dynamics in river systems, whereby nine major fluxes were identified. The application of this framework highlighted the dominance of POC during non-flooded conditions and the significant CO2 emissions during the flooded season. Furthermore, it identified the exchange of POC with the floodplain as an important factor to close the C budget of the river. © 2017, Springer International Publishing Switzerland.AFRIVA

Seasonal and inter-annual variations in carbon fluxes in a tropical river system (Tana River, Kenya)

The hydrological status of river systems is expected to change due to dam operations and climate change. This will affect the riverine fluxes of sediment and carbon (C). In rivers with strong seasonal and inter-annual variability, quantification and extrapolation of sediment and C fluxes can be a challenge as measurement periods are often too short to cover all hydrological conditions. We studied the dynamics of the Tana River (Kenya) from 2012 to 2014 through daily monitoring of sediment concentrations at three sites (Garissa, Tana River Primate Reserve and Garsen) and daily monitoring of C concentrations in Garissa and Garsen during three distinct seasons. A bootstrap method was applied to calculate the range of sediment and C fluxes as a function of annual discharge by using daily discharge data (1942–2014). Overall, we estimated that on average, sediment and carbon were retained in this 600 km long river section between Garissa to Garsen over the 73 years (i.e., fluxes were higher at the upstream site than downstream): integration over all simulations resulted in an average net retention of sediment (~ 2.9 Mt year− 1), POC (~ 18,000 tC year− 1), DOC (~ 920 tC year− 1) and DIC (~ 1200 tC year− 1). To assess the impact of hydrological variations, we constructed four different hydrological scenarios over the same period. Although there was significant non-linearity and difference between the C species, our estimates generally predicted a net increase of C retention between the upstream and downstream site when the annual discharge would decrease, for example caused by an increase of irrigation with reservoir water. When simulating an increase in the annual discharge, e.g. as a potential effect of climate change, we predicted a decrease in C retention.AFRIVA

Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters

Inland waters have been recognized as a~significant source of carbon dioxide (CO2) to the atmosphere at the global scale. Fluxes of CO2 between aquatic systems and the atmosphere are calculated from the gas transfer velocity and the water-air gradient of the partial pressure of CO2 (pCO2). Nowadays, direct measurements of water pCO2 remain scarce in freshwaters and most published pCO2 data are calculated from temperature, pH and total alkalinity (TA). Here, we compare calculated (pH and TA) and measured (Equilibrator and headspace) water pCO2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14.2 mmol L-1), pH (3.94 to 9.17), measured pCO2 (36 to 23 000 ppmv), and dissolved organic carbon (DOC) (29 to 3970 μmol L-1). Calculated pCO2 were > 10% higher than measured pCO2 in 60% of the samples (with a median overestimation of calculated pCO2 compared to measured pCO2 of 2560 ppmv) and were > 100% higher in the 25% most organic-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calculated pCO2 with respect to measured pCO2 are due to the combination of two cumulative effects: (1) a more significant contribution of organic acids anions to TA in waters with low carbonate alkalinity and high DOC concentrations; (2) a lower buffering capacity of the carbonate system at low pH, that increases the sensitivity of calculated pCO2 to TA in acidic and organic-rich waters. We recommend that regional studies on pCO2 should not be based on pH and TA data only, and that direct measurements of pCO2 should become the primary method in inland waters in general, and in particular in acidic, poorly buffered, freshwaters.AFRIVA

Globally significant greenhouse gas emissions from African inland waters

© 2015 Macmillan Publishers Limited. Carbon dioxide emissions to the atmosphere from inland waters - streams, rivers, lakes and reservoirs - are nearly equivalent to ocean and land sinks globally. Inland waters can be an important source of methane and nitrous oxide emissions as well, but emissions are poorly quantified, especially in Africa. Here we report dissolved carbon dioxide, methane and nitrous oxide concentrations from 12 rivers in sub-Saharan Africa, including seasonally resolved sampling at 39 sites, acquired between 2006 and 2014. Fluxes were calculated from published gas transfer velocities, and upscaled to the area of all sub-Saharan African rivers using available spatial data sets. Carbon dioxide-equivalent emissions from river channels alone were about 0.4 Pg carbon per year, equivalent to two-thirds of the overall net carbon land sink previously reported for Africa. Including emissions from wetlands of the Congo river increases the total carbon dioxide-equivalent greenhouse-gas emissions to about 0.9 Pg carbon per year, equivalent to about one quarter of the global ocean and terrestrial combined carbon sink. Riverine carbon dioxide and methane emissions increase with wetland extent and upland biomass. We therefore suggest that future changes in wetland and upland cover could strongly affect greenhouse-gas emissions from African inland waters.status: publishe

Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters

© 2015 Author(s). Inland waters have been recognized as a significant source of carbon dioxide (CO 2 ) to the atmosphere at the global scale. Fluxes of CO 2 between aquatic systems and the atmosphere are calculated from the gas transfer velocity and the water-air gradient of the partial pressure of CO 2 (pCO 2 ). Currently, direct measurements of water pCO 2 remain scarce in freshwaters, and most published pCO 2 data are calculated from temperature, pH and total alkalinity (TA). Here, we compare calculated (pH and TA) and measured (equilibrator and headspace) water pCO 2 in a large array of temperate and tropical freshwaters. The 761 data points cover a wide range of values for TA (0 to 14 200 μmol L -1 ), pH (3.94 to 9.17), measured pCO 2 (36 to 23 000 ppmv), and dissolved organic carbon (DOC) (29 to 3970 μmol L -1 ). Calculated pCO 2 were >10% higher than measured pCO 2 in 60% of the samples (with a median overestimation of calculated pCO 2 compared to measured pCO 2 of 2560 ppmv) and were >100% higher in the 25% most organic-rich and acidic samples (with a median overestimation of 9080 ppmv). We suggest these large overestimations of calculated pCO 2 with respect to measured pCO 2 are due to the combination of two cumulative effects: (1) a more significant contribution of organic acids anions to TA in waters with low carbonate alkalinity and high DOC concentrations; (2) a lower buffering capacity of the carbonate system at low pH, which increases the sensitivity of calculated pCO 2 to TA in acidic and organic-rich waters. No empirical relationship could be derived from our data set in order to correct calculated pCO 2 for this bias. Owing to the widespread distribution of acidic, organic-rich freshwaters, we conclude that regional and global estimates of CO 2 outgassing from freshwaters based on pH and TA data only are most likely overestimated, although the magnitude of the overestimation needs further quantitative analysis. Direct measurements of pCO 2 are recommended in inland waters in general, and in particular in acidic, poorly buffered freshwaters.status: publishe