Trophic scaling and occupancy analysis reveals a lion population limited by top-down anthropogenic pressure in the Limpopo National Park, Mozambique

The African lion (Panthera Leo) has suffered drastic population and range declines over the last few decades and is listed by the IUCN as vulnerable to extinction. Conservation management requires reliable population estimates, however these data are lacking for many of the continent’s remaining populations. It is possible to estimate lion abundance using a trophic scaling approach. However, such inferences assume that a predator population is subject only to bottom-up regulation, and are thus likely to produce biased estimates in systems experiencing top-down anthropogenic pressures. Here we provide baseline data on the status of lions in a developing National Park in Mozambique that is impacted by humans and livestock. We compare a direct density estimate with an estimate derived from trophic scaling. We then use replicated detection/nondetection surveys to estimate the proportion of area occupied by lions, and hierarchical ranking of covariates to provide inferences on the relative contribution of prey resources and anthropogenic factors influencing lion occurrence. The direct density estimate was less than 1/3 of the estimate derived from prey resources (0.99 lions/100 km2 vs. 3.05 lions/100 km2). The proportion of area occupied by lions was Y= 0.439 (SE = 0.121), or approximately 44% of a 2 400 km2 sample of potential habitat. Although lions were strongly predicted by a greater probability of encountering prey resources, the greatest contributing factor to lion occurrence was a strong negative association with settlements. Finally, our empirical abundance estimate is approximately 1/3 of a published abundance estimate derived from opinion surveys. Altogether, our results describe a lion population held below resource-based carrying capacity by anthropogenic factors and highlight the limitations of trophic scaling and opinion surveys for estimating predator populations exposed to anthropogenic pressures. Our study provides the first empirical quantification of a population that future change can be measured against.KTE and LA were supported by the May and Stanley Smith Trust, The Wipplinger KL Bursary Found, Wilderness Wildlife Trust and Canada National Student Grants.http://www.plosone.orgam201

The influence of prey, pastoralism and poaching on the hierarchical use of habitat by an apex predator

As an apex predator, habitat selection by African lions, Panthera leo, is primarily determined by bottom-up processes; however, increasing anthropogenic pressures may alter these relationships. Using camera traps and track surveys in the Limpopo National Park, Mozambique, we collected detection/non-detection data of lions and their prey and combined these with occurrence data on bushmeat poaching activities and spatial data on agro-pastoralist land use and other landscape features. We used hierarchical modelling within an occupancy framework to determine the relative influences of ecological variables on resource use and non-use by lions at two spatial scales. Habitat use by lions was most strongly influenced by the occurrence of their preferred prey across both spatial scales. However, lions were strongly negatively predicted by bushmeat poaching at the finer spatial scale and generally negatively predicted by agro-pastoralist activities at the coarser scale. Restricting our analysis to the home-range scale would have greatly underestimated the impact of bushmeat poaching on the ecology of lions. The results of our study illustrate the trophic dependency of prey resources to lions and the importance of considering scale when investigating species habitat use. Importantly, our study also demonstrates the limiting influence of bushmeat poaching on the use of habitat by an apex predator.K.T.E. and L.A. were supported by the May and Stanley Smith Trust, The Wipplinger KL Bursary Found, Wilderness Wildlife Trust and Canada National Student Grants.http://www.sawma.co.zaam201

Use of site occupancy models for targeted monitoring of the cheetah

The cheetah Acinonyx jubatus has suffered dramatic range contractions and population declines as a result of habitat degradation, prey depletion and conflict with humans. Of further concern is that many of Africa’s remaining cheetah populations persist in human-dominated and highly fragmented landscapes, where their ecology is poorly understood and population data are lacking. Presence–absence surveys may be a practical means to collect these data; however, failing to account for detection error can lead to biased estimates and misleading inferences; potentially having deleterious consequences for species conservation. The goal of this study was to identify how an occupancy modelling technique that explicitly accounts for detectability could be used for quantifying cheetah status in humanimpacted landscapes. Replicated camera-trap and track surveys of 100-km2 sample units were used to estimate the proportion of area occupied by cheetahs and to determine the survey effort required to inform conservation planning. Based on our results, 16 km [±standard error (SE) = 12–22] of walking or 193 camera-trap nights (±SE = 141–292) are required to confirm cheetah absence at a given 100-km2 grid cell (with 95% certainty). Accounting for detection resulted in an overall cheetah occurrence estimate of 0.40 (SE = 0.13), which is 16% higher than the traditional presence–absence estimate that ignores detection error. We test a priori hypotheses to investigate factors limiting cheetahs using an occurrence probability model of their preferred prey. The results show that both cheetahs and their prey were strongly negatively influenced by human settlements. Our study provides an unbiased estimate of occurrence that can be used to compare status across different sites and as a basis for long-term monitoring. Based on our results, we suggest that track and/or camera-trap surveys coupled with site occupancy models may be useful for targeted monitoring of cheetahs across their distribution.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1469-7998hb201

Proopiomelanocortin Neurons in Nucleus Tractus Solitarius Are Activated by Visceral Afferents: Regulation by Cholecystokinin and Opioids

The nucleustractus solitarius (NTS) receives dense terminations from cranial visceral afferents, including those from the gastrointestinal (GI) system. Although the NTS integrates peripheral satiety signals and relays this signal to central feeding centers, little is known about which NTS neurons are involved or what mechanisms are responsible. Proopiomelanocortin (POMC) neurons are good candidates for GI integration, because disruption of the POMC gene leads to severe obesity and hyperphagia. Here, we used POMC– enhanced green fluorescent protein (EGFP) transgenic mice to identify NTS POMC neurons. Intraperitoneal administration of cholecystokinin (CCK) induced c-fos gene expression in NTS POMC–EGFP neurons, suggesting that they are activated by afferents stimulated by the satiety hormone. We tested the synaptic relationship of these neurons to visceral afferents and their modulation by CCK and opioids using patch recordings in horizontal brain slices. Electrical activation of the solitary tract (ST) evoked EPSCs in NTS POMC–EGFP neurons. The invariant latencies, low failure rates, and substantial paired-pulse depression of the ST-evoked EPSCs indicate that NTS POMC–EGFP neurons are second-order neurons directly contacted by afferent terminals. The EPSCs were blocked by the glutamate antagonist 2,3- dihydroxy-6-nitro-7-sulfonyl-benzo[f]quinoxaline. CCK increased the amplitude of the ST-stimulated EPSCs and the frequency of miniature EPSCs, effects attenuated by the CCK1 receptor antagonist lorglumide. In contrast, the orexigenic opioid agonists [D-Ala(2), N-Me-Phe(4), Gly-ol(5)]-enkephalin and met-enkephalin inhibited both ST-stimulated EPSCs and the frequency of miniature EPSCs. These findings identify a potential satiety pathway in which visceral afferents directly activate NTS POMC–EGFP neurons with excitatory inputs that are appropriately modulated by appetite regulators

Evidence for a resident population of cheetah in the Parque Nacional do Limpopo, Mozambique

Transboundary protected areas may be important for the conservation of large African carnivores because these species require large tracts of habitat to maintain viable population numbers and gene flow. Cheetah (Acinonyx jubatus Schreber, 1775), is a species that may benefit from transboundary conservation agreements. It occurs at naturally low population densities, makes use of large home ranges, and disperses over long distances, thus requiring large tracts of suitable habitat to maintain viable population numbers. Here we present the first scientific evidence of a breeding population of cheetah in Parque Nacional do Limpopo (PNL), Mozambique. We obtained data from camera-traps deployed during occupancy surveys conducted from 9 September 2011 to 31 August 2012 over a 3400 km2 study area located within the central third of PNL. These results highlight the importance of the Greater Limpopo Transfrontier Park (GLTFP) to the overall conservation of cheetah in Africa, and the potential value of transboundary protected areas for the conservation of wide-roaming terrestrial mammals.University of Pretoria, the Wilderness Trust and CIB

Evidence for a resident population of cheetah in the Parque Nacional do Limpopo, Mozambique

Transboundary protected areas may be important for the conservation of large African carnivores because these species require large tracts of habitat to maintain viable population numbers and gene flow. Cheetah (Acinonyx jubatus Schreber, 1775), is a species that may benefit from transboundary conservation agreements. It occurs at naturally low population densities,makes use of largehomeranges, and disperses over long distances, thus requiring large tracts of suitable habitat to maintain viable population numbers. Here we present the first scientific evidence of a breeding population of cheetah in Parque Nacional do Limpopo (PNL), Mozambique. We obtained data from camera-traps deployed during occupancy surveys conducted from 9 September 2011 to 31 August 2012 over a 3400 km2 study area located within the central third of PNL. These results highlight the importance of the Greater Limpopo Transfrontier Park (GLTFP) to the overall conservation of cheetah in Africa, and the potential value of transboundary protected areas for the conservation of wide-roaming terrestrial mammals.The University of Pretoria and the Wilderness Trusthttp://www.sawma.co.za/am201

Capsaicin- resistant arterial baroreceptors

BACKGROUND: Aortic baroreceptors (BRs) comprise a class of cranial afferents arising from major arteries closest to the heart whose axons form the aortic depressor nerve. BRs are mechanoreceptors that are largely devoted to cardiovascular autonomic reflexes. Such cranial afferents have either lightly myelinated (A-type) or non-myelinated (C-type) axons and share remarkable cellular similarities to spinal primary afferent neurons. Our goal was to test whether vanilloid receptor (TRPV1) agonists, capsaicin (CAP) and resiniferatoxin (RTX), altered the pressure-discharge properties of peripheral aortic BRs. RESULTS: Periaxonal application of 1 μM CAP decreased the amplitude of the C-wave in the compound action potential conducting at <1 m/sec along the aortic depressor nerve. 10 μM CAP eliminated the C-wave while leaving intact the A-wave conducting in the A-δ range (<12 m/sec). These whole nerve results suggest that TRPV1 receptors are expressed along the axons of C- but not A-conducting BR axons. In an aortic arch – aortic nerve preparation, intralumenal perfusion with 1 μM CAP had no effect on the pressure-discharge relations of regularly discharging, single fiber BRs (A-type) – including the pressure threshold, sensitivity, frequency at threshold, or maximum discharge frequency (n = 8, p > 0.50) but completely inhibited discharge of an irregularly discharging BR (C-type). CAP at high concentrations (10–100 μM) depressed BR sensitivity in regularly discharging BRs, an effect attributed to non-specific actions. RTX (≤ 10 μM) did not affect the discharge properties of regularly discharging BRs (n = 7, p > 0.18). A CAP-sensitive BR had significantly lower discharge regularity expressed as the coefficient of variation than the CAP-resistant fibers (p < 0.002). CONCLUSION: We conclude that functional TRPV1 channels are present in C-type but not A-type (A-δ) myelinated aortic arch BRs. CAP has nonspecific inhibitory actions that are unlikely to be related to TRV1 binding since such effects were absent with the highly specific TRPV1 agonist RTX. Thus, CAP must be used with caution at very high concentrations