Large Wildlife Research Articles

Risk of tick-borne zoonoses in urban green areas: A case study from Turin, northwestern Italy

Ticks are increasingly reported in urban and peri-urban areas, such as city parks or peri-urban forests, across Europe. Land use changes, like the transformation of natural ecosystems into residential or recreational areas, and the restoration of natural areas connectivity for biodiversity purposes, facilitate human contact with these vectors. We evaluated the infestation by Ixodid ticks and their infection by zoonotic agents in two natural reserves (La Mandria and Stupinigi) in the urban area of Turin, northwestern Italy, near to densely inhabited suburbs and consistently frequented by people. We monthly performed dragging in 15 sites during a three-year period (2012–2014).Over 4000 ticks were collected, belonging to the species: Ixodes ricinus, I. acuminatus, Dermacentor marginatus, D. reticulatus, and Haemaphysalis concinna. The tick burden in La Mandria, a park very rich in wildlife, was higher than in Stupinigi, which is surrounded by a grid of roads and cultivated fields. The occurrence of I. ricinus nymphs was mainly related to habitat diversity and seasonal variation but weakly influenced by wildlife presence. Conversely, the density of I. ricinus nymphs were effectively estimated by vegetation coverage, micro-climatic conditions, and the presence of large wildlife. Molecular analyses showed the infections by Borrelia burgdorferi s.l. (24.1 %), Anaplasma phagocytophilum (2.9 %), and Spotted Fever Group rickettsiae (30.4 %) in I. ricinus. Tick-borne encephalitis virus, that is considered so far absent in northwestern Italy, was not detected. In La Mandria, the risk of encountering one I. ricinus nymph infected by Borrelia burgorferi s.l. in 100 m2 was 59.1 % (95% Confidence Interval [CI]: 36.3–83.0), and 71.3 % (95%CI: 44.5–93.0) for Rickettsia spp.Educational programs on personal protection and surveillance on tick-borne diseases should be enhanced to face the threat posed by tick vectors in green urban landscapes.

Biological based ecotourism potential in the complex of protected areas Oti-Keran-Mandouri (Togo, West Africa)

ABSTRACT In Togo, the Oti-Kéran-Mandouri (OKM) complex had important biological-oriented tourism activities in 1980s. However, degradation of ecosystems has negatively affected the biological resources of these protected areas. This study aims at analysing the current biological-based ecotourism potential of the OKM complex facing conservation challenges. To this end, a mixed approach combining fauna and flora inventories with ethnobotanical surveys was adopted.. Results showed that the floristic potential is characterized by 287 species distributed into 63 botanical families and 170 genera. A total of 26 and 19 woody species were identified as species with ‘high cultural value’ and ‘high attractive potential’, respectively. In terms of animal diversity, 11 species of the large wildlife, including emblematic species, have been recorded. Six of these animal and plant species are reported in the IUCN Red List. These findings provide insights on the great potential of OKM complex for ecotourism promotion in Togo.

Serological survey of epizootic hemorrhagic disease in European bison in Poland in 2017-2018

The European bison (Bison bonasus) is an endangered species whose restitution requires systematic health monitoring. The most practical way to test clinical material from large wildlife is by serological methods. Recently, the most serious health hazard faced by the European bison population was tuberculosis. However, climate change and globalization have resulted in the arrival of more exotic diseases, one of which is epizootic hemorrhagic disease (EHD), caused by the epizootic hemorrhagic disease virus (EHDV). EHD is an arthropodtransmitted viral disease noted mainly in ungulates, especially ruminants. Clinical signs vary depending on the virus serotype and host. The aim of this study was to determine the prevalence of EHD in European bison by serological testing for antibodies to EHDV. Serum samples were collected from 90 European bison living in different regions of Poland and tested with PrioCHECK™ EHDV Ab Serum Kit (Thermofisher, US). One of the bison (from the Knyszyńska Forest) had a positive result. It cannot be excluded, however, that the result was a false positive. There is a need for further EHDV serology monitoring in European bison and other wildlife, particularly in the Knyszyńska Forest.

A new decision support tool for collaborative adaptive vegetation management in northern Great Plains national parks

National Park Service (NPS) units in the northern Great Plains (NGP) were established to preserve and interpret the history of America, protect and showcase unusual geology and paleontology, and provide a home for vanishing large wildlife. A unifying feature among these national parks, monuments, and historic sites is mixed-grass prairie, which not only provides background scenery but is the very foundation of many park missions. As recognition of the prairie’s importance to park fundamental resources and values has grown, so too has the realization that invasive plants threaten these values by reducing native species diversity, altering food webs, and marring the visitor experience. Parks manage invasive species despite uncertainties in treatment effectiveness because management cannot wait for research to provide definitive answers. Under these circumstances, adaptive management (AM) is an appropriate approach. In the NGP, we formed a collaborative adaptive vegetation management team to apply AM towards reducing invasive species (with a focus on exotic annual grasses) and improving native vegetation conditions. In our AM framework, the team uses a Bayesian model built from NPS Inventory & Monitoring and Fire Effects monitoring data and experimental results to predict the effects of management actions on park management units, according to those units’ vegetation condition and management history. These predictions inform management decisions, which are then applied.

Mapping and assessing the impact of small‐scale ephemeral water sources on wildlife in an African seasonal savannah

In many savannah regions of Africa, pronounced seasonal variability in rainfall results in wildlife being restricted to floodplains and other habitats adjacent to permanent surface water in the dry season. During the wet season, rainfall fills small-scale, ephemeral water sources that allow wildlife to exploit forage and other resources far from permanent surface water. These water sources remain difficult to quantify, however, due to their small and ephemeral nature, and as a result are rarely included in quantitative studies of wildlife distribution, abundance, and movement. Our goal was to map ephemeral water in Bwabwata National Park in Namibia using two different approaches and to relate measures of ephemeral water to the abundance, distribution, and movement of two large wildlife species. We used high-resolution Google Earth and Esri World imagery to visually identify waterholes. Additionally, we used Sentinel-2 satellite imagery to map ephemeral water across the study area using the Normalized Difference Water Index. With these mapped waterhole layers and data from GPS-collared individuals of African elephant (Loxodonta africana) and African buffalo (Syncerus caffer), we evaluated the importance of ephemeral water in conditioning abundance and movement of these two species. The two approaches to mapping ephemeral water resulted in the visual identification of nearly 10,000 waterholes, and a predicted ephemeral water layer of ~76% accuracy. The inclusion of ephemeral water into models of abundance and movement resulted in improved goodness of fit relative to those without water, and water impacts on abundance and movement were among the strongest of all variables considered. The potential importance of ephemeral water in conditioning the movements and distributions of large herbivores in African savannahs has been difficult to quantify relative to vegetation drivers. Our results suggest research into ephemeral water impacts deserves more attention.

Hippopotamus are distinct from domestic livestock in their resource subsidies to and effects on aquatic ecosystems.

In many regions of the world, populations of large wildlife have been displaced by livestock, and this may change the functioning of aquatic ecosystems owing to significant differences in the quantity and quality of their dung. We developed a model for estimating loading rates of organic matter (dung) by cattle for comparison with estimated rates for hippopotamus in the Mara River, Kenya. We then conducted a replicated mesocosm experiment to measure ecosystem effects of nutrient and carbon inputs associated with dung from livestock (cattle) versus large wildlife (hippopotamus). Our loading model shows that per capita dung input by cattle is lower than for hippos, but total dung inputs by cattle constitute a significant portion of loading from large herbivores owing to the large numbers of cattle on the landscape. Cattle dung transfers higher amounts of limiting nutrients, major ions and dissolved organic carbon to aquatic ecosystems relative to hippo dung, and gross primary production and microbial biomass were higher in cattle dung treatments than in hippo dung treatments. Our results demonstrate that different forms of animal dung may influence aquatic ecosystems in fundamentally different ways when introduced into aquatic ecosystems as a terrestrially derived resource subsidy.

Adjusting trail cameras to improve monitoring of small open cup nesting birds

Camera traps are a valuable tool in wildlife monitoring. Despite their wide use to capture large or medium-sized species, modern techniques also allow them to capture small animals. However, customized cameras, which meet the challenging demands for this purpose during fieldwork, are still quite expensive and require a certain technical know-how. Here we present a way to modify commercial trail cameras to monitor open-nesting songbirds. In particular, we describe how to adjust focus and exposure in order to capture close-up situations of small animals which are very distinct from the default settings when capturing large wildlife. We illustrate the applicability of the modifications from data of a nest predation survey in the Blackcap (Sylvia atricapilla). Compared to pictures from a preliminary study using unmodified trail cameras of the same kind, the pictures were much improved in picture focus and in nocturnal exposure. In addition to improved species identification, the modifications also allowed the cameras to capture more details of life-history events (e.g. of hatching processes and feeding). The manipulation protocol offers a promising and cost-effective approach for nest monitoring as well as for different areas of “close-up” applications to study small endothermic animals.

Comparison of sampling precision for nearshore marine wildlife using unmanned and manned aerial surveys

Aerial surveys of large marine wildlife in nearshore areas can support management actions to ensure conservation of this megafauna. While most aerial surveys of marine wildlife have been carried out using manned aircraft, unmanned aerial systems (commonly known as drones) are being increasingly used. Here, we compare the relative accuracy and precision of marine wildlife surveys from a multirotor drone and a manned helicopter for the first time. At two locations on the east coast of Australia, we simultaneously surveyed sharks (including white sharks, Carcharodon carcharias), dolphins, rays, and sea turtles in nearshore coastal areas using a multirotor drone (DJI Inspire I) and a helicopter (Robinson 44 Clipper II) over 26 separate flights. Sampling included the real-time quantification of marine wildlife by an observer in the helicopter and the pilot of the drone. The video feed from the drone was then later re-sampled in the laboratory. Of the three methods, post-hoc analysis of drone video footage is likely to provide the most accurate and precise estimates of marine wildlife in nearshore areas. When real-time data are required (e.g., for shark-risk mitigation), manned helicopters (over larger stretches of coast) and drones (across localised beaches) will both be useful.

Tracing ancient animal husbandry in tropical Africa using the fossil spore assemblages of coprophilous fungi: a validation study in western Uganda

Fossil spores of coprophilous fungi preserved in lake and bog sediments are well-established palaeoecological tracers for the local history of pastoralism and other animal husbandry. However, applications in Africa are limited by the lack of information on the exact relationship between human activity and fungi growing on large-herbivore dung. Here we use 25 small crater-lake basins in western Uganda, which cover the complete regional gradient of natural vegetation and human impact intensity, as a natural laboratory to assess the relationship between coprophilous fungal spores recovered from recently deposited bottom sediments and the presence and abundance of large domestic herbivores in the surrounding crater basins. We find that the summed abundances of Sporormiella, Sordaria, Podospora and Delitschia, or of these four types plus Cercophora, are the most useful and robust fungal-spore indicators for the presence of domestic large herbivores in an East African context. Chaetomium could also be added to this list, particularly as it may help reduce stochasticity in the often low fossil counts of obligate coprophilous types. Our results suggest that domestic large herbivores, at least when associated with some degree of crop agriculture, leave a clearer signature on fungal-spore assemblages in the lakes’ sediments than large wildlife. Furthermore, they indicate that the typically small number of livestock kept by mixed-subsistence farmers leave a stronger imprint on fungal-spore assemblages than the much larger herds of specialist pastoralists occasionally visiting the lake to drink or bathe.

How sampling‐based overdispersion reveals India's tiger monitoring orthodoxy

AbstractAgencies responsible for recovering populations of iconic mammals may exaggerate population trends without adequate scientific evidence. Recently, such populations were termed as “political populations” in the conservation literature. We surmise such cases are manifested when agencies are pressured to estimate population parameters at large spatial scales for elusive species. For example, India's tiger conservation agencies depend on an extrapolation method using index‐calibration models for estimating population size. A recent study demonstrated mathematically the unreliability of this approach in practical situations. However, it continues to be applied by official agencies in Asia and promoted further by global organizations working on tiger conservation. In this article, we aim to: (a) discuss the ecological oddities in the results of India's national tiger surveys, (b) contrast these survey approaches to known statistical approaches for large scale wildlife abundance estimation, (c) demystify the mathematics underlying the problems with the survey methodology, and (d) substantiate these arguments with results from India's national tiger survey of 2014. Our analyses show that the predictions of tiger abundance reported by the 2014 survey, and consequently on tiger population trends, are misleading because of the presence of high sampling‐based overdispersion and parameter covariance due to unexplained heterogeneity in detection probabilities. We plead for designing monitoring programs to answer clearly defined scientific or management questions rather than attempt to meet extraneous social or funding related expectations.

Effects of land-use change on community diversity and composition are highly variable among functional groups.

In order to understand how the effects of land-use change vary among taxa and environmental contexts, we investigate how three types of land-use change have influenced phylogenetic diversity (PD) and species composition of three functionally distinct communities: plants, small mammals, and large mammals. We found large mammal communities were by far the most heavily impacted by land-use change, with areas of attempted large wildlife exclusion and intense livestock grazing, respectively, containing 164 and 165 million fewer years of evolutionary history than conserved areas (~40% declines). The effects of land-use change on PD varied substantially across taxa, type of land-use change, and, for most groups, also across abiotic conditions. This highlights the need for taxa-specific or multi-taxa evaluations, for managers interested in conserving specific groups or whole communities, respectively. It also suggests that efforts to conserve and restore PD may be most successful if they focus on areas of particular land-use types and abiotic conditions. Importantly, we also describe the substantial species turnover and compositional changes that cannot be detected by alpha diversity metrics, emphasizing that neither PD nor other taxonomic diversity metrics are sufficient proxies for ecological integrity. Finally, our results provide further support for the emerging consensus that conserved landscapes are critical to support intact assemblages of some lineages such as large mammals, but that mosaics of disturbed land-uses, including both agricultural and pastoral land, do provide important habitats for a diverse array of plants and small mammals.

Roadkill distribution at the wildland‐urban interface

ABSTRACTThe growing wildland‐urban interface is a frontier of human‐wildlife conflict worldwide. Where natural and developed areas meet, there is potential for negative interactions between humans and wild animals, including wildlife‐vehicle collisions. Understanding the environmental and anthropogenic factors leading to these collisions can inform transportation and habitat planning, with an objective of reducing animal mortality and human costs. We investigated spatial, temporal, and species‐specific patterns of roadkill on Interstate‐280 (I‐280) in California, USA, and examined the effects of land cover, fencing, lighting, and traffic. The highway is situated just south of San Francisco, dividing a large wildlife refuge to the west from dense residential areas to the east, and therefore presents a major barrier to wildlife movement. Areas with a higher percentage of developed land east of I‐280 and areas with more open space on the west side of I‐280 were associated with an increase in overall roadkill, suggesting that hard boundaries at the wildland‐urban interface may be zones of high risk for dispersing animals. This pattern was especially strong for raccoons (Procyon lotor) and black‐tailed deer (Odocoileus hemionus). The presence of lighting correlated with increased roadkill with the exception of coyote (Canis latrans). Contrary to our expectations, we found weak evidence that fencing increases roadkill, perhaps because animals become trapped on roadways or because fencing is not sufficient to block access to the road by wildlife. Finally, we found strong evidence for roadkill seasonality, correlated with differences in movement and dispersal across life‐history stages. We highlight the value of citizen‐science datasets for monitoring human‐wildlife conflict and suggest potential mitigation measures to reduce the negative effects of wildlife‐vehicle collisions for people and wildlife. © 2019 The Wildlife Society.

Conservation success or increased crop damage risk? The Natura 2000 network for a thriving migratory and protected bird

Protected areas are important to support biodiversity and endangered species. However, they are often too small to fulfill the resource requirements of many large and mobile wildlife species, especially when congregating in large numbers. In such cases, wildlife may overflow onto surrounding human-dominated land and cause impacts. The aim of the EU Natura 2000 network is to increase supranational connectivity between protected areas for migratory and protected species such as the common crane (Grus grus). The crane population along the Western European flyway has been increasing rapidly in recent decades, with peaks of 200,000 cranes at specific Natura 2000 sites. We studied 32 GPS-tagged cranes over four migration periods, to test the use of the network by cranes and the potential for impacts on adjacent farmland. During the nighttime, the probability that roosting cranes were located on Natura 2000 sites was 97%. During daytime, the probability of foraging cranes being located on arable land was 68%. The probability of foraging cranes occurring on agricultural fields close to Natura 2000 sites decreased with distance. Such foraging patterns may fuel conflicts between conservation and agricultural objectives. To resolve these conflicts we suggest improved cross-boundary collaboration and policy development among involved states, combined with stakeholder participation to implement effective compensation and damage prevention strategies which are focused upon networks of protected areas.

Monitoring large and complex wildlife aggregations with drones

Abstract Recent advances in drone technology have rapidly led to their use for monitoring and managing wildlife populations but a broad and generalised framework for their application to complex wildlife aggregations is still lacking. We present a generalised semi‐automated approach where machine learning can map targets of interest in drone imagery, supported by predictive modelling for estimating wildlife aggregation populations. We demonstrated this application on four large spatially complex breeding waterbird colonies on floodplains, ranging from c. 20,000 to c. 250,000 birds, providing estimates of bird nests. Our mapping and modelling approach was applicable to all four colonies, without any modification, effectively dealing with variation in nest size, shape, colour and density and considerable background variation (vegetation, water, sand, soil, etc.). Our semi‐automated approach was between three and eight times faster than manually counting nests from imagery at the same level of accuracy. This approach is a significant improvement for monitoring large and complex aggregations of wildlife, offering an innovative solution where ground counts are costly, difficult or not possible. Our framework requires minimal technical ability, is open‐source (Google Earth Engine and R), and easy to apply to other surveys.

Death of a psychonaut: First French carfentanil fatality

Carfentanil (CaF) is a new synthetic opioid (NSO) solely approved for veterinary use (to incapacitate various species of large exotic wildlife) as it is 10,000 times more powerful than morphine. CaF has wildly recently appeared emerged in the NPS market and many overdose deaths have been reported in the USA since 2016. In December 2017, a 41-years-old polydrugs abuser for several years, especially of NPS purchased on the darkweb, is found dead in his room, a syringe planted under the tongue. His history includes recent carfentanyl intoxication treated with Nalscue ® . The prosecutor requires autopsy and toxicological analyzes. Autopsy specimens (blood and urine) were analyzed using standard laboratory techniques (GC-FID, GC-MS and LC-MS/MS). A LC-HRMS method was used to perform a broad and specific search for NSOs including Caf in blood, urine and hair samples. Blood and urine positive results include CaF, illicit (or not) drugs (see Table 1 ) and ethanol (BAC 0.5 g/L). In addition, these drugs were also identified in (brown, 9 cm length) hair sample together with additional drugs i.d. pharmaceuticals (cyamemazine, codeine, diazepam, quetiapine, sildenafil), illicit drugs (heroin, cocaine, MDMA), other NSOs (benzoylfentanyl and 4-fluobutyrylfentanyl) and other NPS (ethylhexedrone, diclazepam and methoxetamine). Observed CaF hair concentrations ranged from 54 to 166 pg/mg in the three 3-cm length hair segment. CaF use is here associated with other opioids, illicit drugs and psychotropic depressants of the respiratory system, like the other cases described in the literature. Blood concentration of CaF is of the same order or higher than those reported in cases of lethal poisoning described in the USA and recently in UK [1] , [2] . To our knowledge, this is the first identification of this fentanyl derivative in a fatality in France. Although hair results strongly suggest a significant tolerance of the victim to NSOs, the relatively high postmortem CaF concentration observed in the victim's blood (4.20 μg/L) together with the absence of metabolite (especially NorCaF) in blood or urine, suggest a sudden death immediately following a significant CaF dose intake (presumably injected).

Nowhere to hide.

The most poached and trafficked of all animals, pangolins could vanish before scientists really get to know them.

Don't poke the bear: using tracking data to quantify behavioural syndromes in elusive wildlife

Animal personality traits and the emergence of behavioural syndromes, i.e. between-individual correlation of behaviours, are commonly quantified from behavioural observations in controlled environments. Subjecting large and elusive wildlife to controlled test situations is, however, rarely possible, suggesting that ecologists should exploit alternative measures of behaviours for quantifying differences between individuals. Our goal was to test whether movement and space use data can be used to quantify behavioural syndromes in the wild. We quantified six behaviours from GPS and dual motion sensor tracking devices of 46 adult female brown bears followed in southcentral Sweden over the summer and early autumn. As well as daily travel distance, an indicator for activity, and daily displacement, an indicator for exploration, we quantified four behaviours that increase a bear's likelihood of encountering humans and could thus serve as indicators for boldness: diurnality, selection for roads and selection for two open habitat types, bogs and clearcuts, with low lateral cover. We tested (1) whether behaviours showed repeatable between-individual variation (animal personality) and (2) whether behaviours were correlated between individuals and thus formed a behavioural syndrome. Repeatability of behaviours ranged from 0.16 to 0.61 confirming between-individual variation in movement, activity and space use. A multivariate mixed model revealed significant positive correlations between travel distance, displacement and diurnality, suggesting the existence of an activity–exploration and potentially partial boldness syndrome in our bear population. Selection for exposed or human-frequented habitats were uncorrelated with the activity–exploration syndrome and with each other, albeit there was a trend for stronger road avoidance by bears that readily used clearcuts. We show that large tracking data sets can be used to quantify between-individual correlation in spatial behaviours. We suggest that delineating behavioural types from wildlife tracking data will be of increasing interest because of the importance of animal personality for ecological processes, wildlife conservation and human–wildlife coexistence.

Sustainable Fisheries Management and the Welfare of Bycaught and Entangled Cetaceans.

The incidental capture of cetaceans and other protected marine wildlife in fishing gear has significant welfare implications. Many thousands of cetaceans are bycaught in fishing gear in European waters and hundreds of thousands die globally. We can expect many more to survive, but suffer from such interactions. As marine policy focuses on “population level” impact assessments and “sustainability” of fishing to preserve fish populations, the impacts to the bycaught individual, and their wider social group, are often largely underestimated, despite the large numbers affected. The wide range of recorded injuries, including abrasions, cuts, bruising, and broken bones, along with the potential for panic associated with forced submersion, indicate that the welfare of bycaught cetaceans is, individually and collectively, very poor. Commercial fishing is the last human activity targeting wildlife (fish) on a grand scale where slaughter includes incidental killing of other large sapient wildlife on such a regular basis. Here, we review the compelling evidence of the short and long term welfare impacts of bycatch, and the progress made toward implementation of measures to understand and solve this significant welfare issue. We argue that policy decisions surrounding fishing do not adequately consider cetacean bycatch, including welfare impacts. Ultimately, there are welfare issues in all bycatch situations and suffering cannot plausibly be reduced without preventing bycatch. The well-documented welfare implications provide a strong argument for zero tolerance of cetacean bycatch and provide a compelling case for immediate action in fisheries where bycatch is taking place. The only way to reduce the suffering of bycaught cetaceans is to decrease, or ideally eliminate, the number of animals caught in fishing gear. Uncertainties around the scale of bycatch should not delay management, even where individual bycatch estimates are considered “sustainable.” Lack of monitoring of sub-lethal impacts on populations may result in flawed impact assessments. We urge that animal welfare considerations should become an integral part of management decision-making in relation to bycatch globally. Enhanced, robust and transparent management systems are urgently required for the range of fisheries within which cetacean bycatch occurs, with the aim to better document and most importantly, work toward eliminating cetacean bycatch altogether.

Trophic rewilding: impact on ecosystems under global change.

Human-induced global change is increasingly affecting life on our planet, including living conditions for humans themselves as well as the resources we depend on [1,2]. As a result, species diversity is strongly declining [3–5]. The Living Planet Index shows a 58% global decline in populations of amphibians, fish, reptiles, mammals and birds between 1970 and 2012, varying from 36 to 38% in terrestrial and marine ecosystems to 81% in freshwater habitat [6]. Habitat loss or degradation and overexploitation are the main causes of these steep declines. Since the worldwide expansion of modern humans ( Homo sapiens ) began, humans have overexploited vertebrates, with a bias to the largest animals being extirpated first, from the Late Pleistocene extinctions of terrestrial megafauna to the ongoing declines of terrestrial, marine and freshwater large-bodied animals [7–11]. There is increasing evidence that this global wildlife loss, or defaunation, does not only imply the loss of charismatic animals but also the functions they have in ecosystems [12–16]. To restore these missing functions, a novel ecological restoration technique has emerged, referred to as rewilding [17]. Rewilding aims to restore natural processes in ecosystems in general, and often focuses on re-introduction of missing large wildlife species or, in case these went extinct, their proxies [18]. Rewilding is increasingly implemented in practice globally, with a strong emphasis on Europe and the re-introduction of large herbivores [19,20]. Rewilding has recently been described as ‘a captivating, controversial, twenty-first century concept to address ecological degradation’ [20]. Most rewilding initiatives fit the concept of trophic rewilding, defined as an ecological restoration strategy that uses species introductions to restore top-down trophic interactions and associated trophic cascades to promote …

Organic matter and nutrient inputs from large wildlife influence ecosystem function in the Mara River, Africa.

Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion, and carcasses, and the stoichiometry and bioavailability of these inputs likely interact with characteristics of the recipient ecosystem to determine their effects on ecosystem function. We studied the influence of hippopotamus excretion/egestion and wildebeest carcasses, and their interactions with discharge, in the Mara River, Kenya. We measured nutrient dissolution and decomposition rates of wildlife inputs, the influence of inputs on nutrient concentrations and nutrient limitation in the river and the influence of inputs on biofilm growth and function in both experimental streams and along a gradient of inputs in the river. We found that hippopotamus excretion/egestion increases ammonium and coarse particulate organic matter in the river, and wildebeest carcasses increase ammonium, soluble reactive phosphorus, and total phosphorus. Concentrations of dissolved carbon and nutrients in the water column increased along a gradient of wildlife inputs and during low discharge, although concentrations of particulate carbon decreased during low discharge due to deposition on the river bottom. Autotrophs were nitrogen limited and heterotrophs were carbon limited and nitrogen and phosphorus colimited upstream of animal inputs but there was no nutrient limitation downstream of inputs. In experimental streams, hippo and wildebeest inputs together increased biofilm gross primary production (GPP) and respiration (R). These results differed in the river, where low concentrations of hippo inputs increased gross primary production (GPP) and respiration (R) of biofilms, but high concentrations of hippo inputs in conjunction with wildebeest inputs decreased GPP. Our research shows that inputs from large wildlife alleviate nutrient limitation and stimulate ecosystem metabolism in the Mara River and that the extent to which these inputs subsidize the ecosystem is mediated by the quantity and quality of inputs and discharge of the river ecosystem. Thus, animal inputs provide an important ecological subsidy to this river, and animal inputs were likely important in many other rivers prior to the widespread extirpation of large wildlife.