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Funder: Sabine Plattner African Charities, The evolutionary origins of how modern humans share and use space are often modelled on the territorial-based violence of chimpanzees, with limited comparison to other apes. Gorillas are widely assumed to be non-territorial due to their large home ranges, extensive range overlap, and limited inter-group aggression. Using large-scale camera trapping, we monitored western gorillas in Republic of Congo across 60 km2. Avoidance patterns between groups were consistent with an understanding of the "ownership" of specific regions, with greater avoidance of their neighbours the closer they were to their neighbours' home range centres. Groups also avoided larger groups' home ranges to a greater extent, consistent with stronger defensive responses from more dominant groups. Our results suggest that groups may show territoriality, defending core regions of their home ranges against neighbours, and mirror patterns common across human evolution, with core areas of resident dominance and larger zones of mutual tolerance. This implies western gorillas may be a key system for understanding how humans have evolved the capacity for extreme territorial-based violence and warfare, whilst also engaging in the strong affiliative inter-group relationships necessary for large-scale cooperation.

Modern human societies show hierarchical social modularity (HSM) in which lower-order social units like nuclear families are nested inside increasingly larger units. It has been argued that this HSM evolved independently and after the chimpanzee–human split due to greater recognition of, and bonding between, dispersed kin. We used network modularity analysis and hierarchical clustering to quantify community structure within two western lowland gorilla populations. In both communities, we detected two hierarchically nested tiers of social structure which have not been previously quantified. Both tiers map closely to human social tiers. Genetic data from one population suggested that, as in humans, social unit membership was kin structured. The sizes of gorilla social units also showed the kind of consistent scaling ratio between social tiers observed in humans, baboons, toothed whales, and elephants. These results indicate that the hierarchical social organization observed in humans may have evolved far earlier than previously asserted and may not be a product of the social brain evolution unique to the hominin lineage.

Could new oral vaccine technologies protect endangered wildlife against a rising tide of infectious disease? We used captive chimpanzees to test oral delivery of a rabies virus (RABV) vectored vaccine against Ebola virus (EBOV), a major threat to wild chimpanzees and gorillas. EBOV GP and RABV GP-specific antibody titers increased exponentially during the trial, with rates of increase for six orally vaccinated chimpanzees very similar to four intramuscularly vaccinated controls. Chimpanzee sera also showed robust neutralizing activity against RABV and pseudo-typed EBOV. Vaccination did not induce serious health complications. Blood chemistry, hematologic, and body mass correlates of psychological stress suggested that, although sedation induced acute stress, experimental housing conditions did not induce traumatic levels of chronic stress. Acute behavioral and physiological responses to sedation were strongly correlated with immune responses to vaccination. These results suggest that oral vaccination holds great promise as a tool for the conservation of apes and other endangered tropical wildlife. They also imply that vaccine and drug trials on other captive species need to better account for the effects of stress on immune response.

Aim: To predict the distribution of suitable environmental conditions (SEC) for eight African great ape taxa for a first time period, the 1990s and then project it to a second time period, the 2000s; to assess the relative importance of factors influencing SEC distribution and to estimate rates of SEC loss, isolation and fragmentation over the last two decades. Location: Twenty-two African great ape range countries. Methods: We extracted 15,051 presence localities collected between 1995 and 2010 from 68 different areas surveyed across the African ape range. We combined a maximum entropy algorithm and logistic regression to relate ape presence information to environmental and human impact variables from the 1990s with a resolution of 5 9 5 km across the entire ape range. We then made SEC projections for the 2000s using updated human impact variables. Results: Total SEC area was approximately 2,015,480 and 1,807,653 km2 in the 1990s and 2000s, respectively. Loss of predicted SEC appeared highest for Cross River gorillas (_59%), followed by eastern gorillas (_52%), western gorillas (_32%), bonobos (_29%), central chimpanzees (_17%) and western chimpanzees (_11%). SEC for Nigeria-Cameroon chimpanzees and eastern chimpanzees was not greatly reduced. Except for Cross River and eastern gorillas, the number of SEC patches did not change significantly, suggesting that SEC loss was caused mainly by patch size reduction. Main conclusions: The first continent-wide perspective of African ape SEC distribution shows dramatic declines in recent years. The model has clear limitations for use at small geographic scales, given the quality of available data and the coarse resolution of predictions. However, at the large scale it has potential for informing international policymaking, mitigation of resource extraction and infrastructure development, as well as for spatial prioritization of conservation effort and evaluating conservation effectiveness.

Thanks to recent technological advances, it is now possible to track with an unprecedented precision and for long periods of time the movement patterns of many living organisms in their habitat. The increasing amount of data available on single trajectories offers the possibility of understanding how animals move and of testing basic movement models. Random walks have long represented the main description for micro-organisms and have also been useful to understand the foraging behaviour of large animals. Nevertheless, most vertebrates, in particular humans and other primates, rely on sophisticated cognitive tools such as spatial maps, episodic memory and travel cost discounting. These properties call for other modeling approaches of mobility patterns. We propose a foraging framework where a learning mobile agent uses a combination of memory-based and random steps. We investigate how advantageous it is to use memory for exploiting resources in heterogeneous and changing environments. An adequate balance of determinism and random exploration is found to maximize the foraging efficiency and to generate trajectories with an intricate spatio-temporal order. Based on this approach, we propose some tools for analysing the non-random nature of mobility patterns in general., Comment: 14 pages, 4 figures, improved discussion

Plasmodium falciparum is the most prevalent and lethal of the malaria parasites infecting humans, yet the origin and evolutionary history of this important pathogen remain controversial. Here we develop a single-genome amplification strategy to identify and characterize Plasmodium spp. DNA sequences in faecal samples from wild-living apes. Among nearly 3,000 specimens collected from field sites throughout central Africa, we found Plasmodium infection in chimpanzees (Pan troglodytes) and western gorillas (Gorilla gorilla), but not in eastern gorillas (Gorilla beringei) or bonobos (Pan paniscus). Ape plasmodial infections were highly prevalent, widely distributed and almost always made up of mixed parasite species. Analysis of more than 1,100 mitochondrial, apicoplast and nuclear gene sequences from chimpanzees and gorillas revealed that 99% grouped within one of six host-specific lineages representing distinct Plasmodium species within the subgenus Laverania. One of these from western gorillas comprised parasites that were nearly identical to P. falciparum. In phylogenetic analyses of full-length mitochondrial sequences, human P. falciparum formed a monophyletic lineage within the gorilla parasite radiation. These findings indicate that P. falciparum is of gorilla origin and not of chimpanzee, bonobo or ancient human origin. The evolutionary origin of Plasmodium falciparum, the most prevalent and lethal of the malaria parasites infecting humans, is much debated. Genetic analysis of thousands of fecal samples from wild-living African apes show that the parasites found in the western gorillas — rather than those of chimpanzees or bonobos — are most closely related to the human parasite. The data suggest that all extant human strains of the parasite evolved from a single host transfer event. The new findings are also relevant to the current antimalaria campaign, as they point to potential Plasmodium reservoirs in apes. The evolutionary origin of the human malaria parasite Plasmodium falciparum has been much debated. Genetic analysis of a large number of faecal samples from wild-living African apes now shows that Plasmodium parasites from Western gorillas are most closely related to the human parasite. The data suggest that human P. falciparum evolved from a gorilla parasite after a single host transfer event.

Hunting is the major driver of large mammal decline in Central African forests. In slowly reproducing species even low hunting pressure leaves spatial gradients with wildlife density increasing with distance from transport routes and human settlements. Park management can use this pattern formation to identify sources of threats, but also to discriminate between different threat scenarios, such as the impact of subsistence vs. commercial hunting. We conducted an ape survey in the mountainous Moukalaba Doudou National Park, Gabon, to evaluate whether potential population gradients would emanate from the three human population centers in the region or the villages surrounding the park. Using generalized linear modeling we found hill slope as a good predictor of ape nest occurrence probability and the distance to human population centers a better predictor of ape nest density and ape nest group size than distance to villages. In fact ape nest density was three times lower at the park borders close to the human population centers than in the park’s interior. The results indicate that Moukalaba’s ape population is more impacted by commercial than subsistence hunting and suggest that park management should focus conservation efforts on the human population centers. We conclude that in particular for slowly reproducing species geographic information on wildlife population gradients are of additional value for guiding protected area management. The hunting impact on those species might be easily underestimated, if derived only from market surveys or transport route controls, where they are only rarely found.

The abundance of large vertebrates is rapidly declining, particularly in the tropics where over-hunting has left many forests structurally intact but devoid of large animals. An urgent question then, is whether these ‘empty’ forests can sustain their biodiversity without large vertebrates. Here we examine the rol eo f forest elephant (Loxodonta africana cyclotis) seed dispersal in maintaining the community structure of trees in the Ndoki Forest, northern Congo. Analysis of 855 elephant dung piles suggested that forest elephants disperse more intact seeds than any other species or genus of large vertebrate in African forests, while GPS telemetry data showed that forest elephants regularly disperse seeds over unprecedented distances compared to other dispersers. Our analysis of the spatial distribution of trees from a sample of 5667 individuals showed that dispersal mechanism was tightly correlated with the scale of spatial aggregation. Increasing amounts of elephant seed dispersal was associated with decreasing aggregation. At distances of < 200 m, trees whose seeds are dispersed only by elephants were less aggregated than the random expectation, suggesting Janzen–Connell effects on seed/seedling mortality. At the landscape scale, seed dispersal mode predicted the rate at which local tree community similarity decayed in space. Our results suggest that the loss of forest elephants (and other large-bodied dispersers) may lead to a wave of recruitment failure among animal-dispersed tree species, and favor regeneration of the species-poor abiotically dispersed guild of trees.

Large mammal surveys are often based on indices of animal abundance such as dung or, for great apes, sleeping nests. They also tend to rely on the “steady state” assumption that the rate at which an index is deposited in the environment is exactly balanced by the rate at which it disappears (decays). Here we use a data set on western gorilla (Gorilla gorilla) sleeping nest decay rates to show that this assumption is likely to be strongly violated often and in ways that have serious implications for our ability to accurately survey and monitor a wide range of endangered species, particularly in tropical forests. We first fit the data using a model describing the daily probability of nest decay as a function of nest age and monthly rainfall. We then use this decay model to simulate time series of gorilla nest standing stock, given observed rainfall regimes from a series of sites in the equatorial African country of Gabon. These simulations suggest that, within a given site, the relationship between nest standing stock and true gorilla density fluctuates wildly and is, on average, tens of percent away from the mean nest decay time for the empirical data set. The behavior of nest standing stock is extremely sensitive to variability in rainfall, not just annual mean rainfall. Differences between sites in rainfall variability produce counterintuitive differences between sites in nest standing stock. Multiyear trends in the mean and variance of rainfall produce the spurious impression of trends in animal abundance. Furthermore, heterogeneity in rainfall exists at all spatial and temporal scales, so that attempts to use regression models based on rainfall measurements taken at one location or time are not likely to accurately predict the nest decay regime at other places or times. We close with some suggestions on alternative estimation methods that do not rely on extrapolations of environmental conditions from one time or place to another.

Here, we document the invasion of equatorial Africa by the little red fire ant (Wasmannia auropunctata). Commercial logging and other forms of natural resource extraction have catapulted W. auropunctata into the interior of Gabon at a rate 60 times faster than the unassisted rate we measured over 19 years at the Lope Reserve. We also present photographic evidence suggesting that W. auropunctata is negatively affecting the country's exceptionally rich and intact large mammal fauna.

Because rapidly expanding human populations have devastated gorilla (Gorilla gorilla) and common chimpanzee (Pan troglodytes) habitats in East and West Africa, the relatively intact forests of western equatorial Africa have been viewed as the last stronghold of African apes1. Gabon and the Republic of Congo alone are thought to hold roughly 80% of the world's gorillas2 and most of the common chimpanzees1. Here we present survey results conservatively indicating that ape populations in Gabon declined by more than half between 1983 and 2000. The primary cause of the decline in ape numbers during this period was commercial hunting, facilitated by the rapid expansion of mechanized logging. Furthermore, Ebola haemorrhagic fever is currently spreading through ape populations in Gabon and Congo and now rivals hunting as a threat to apes. Gorillas and common chimpanzees should be elevated immediately to ‘critically endangered’ status. Without aggressive investments in law enforcement, protected area management and Ebola prevention, the next decade will see our closest relatives pushed to the brink of extinction.

Significance Although infectious disease is now recognized as a major threat to wild gorillas and chimpanzees, safety fears have stifled the use of a powerful disease control tool, vaccination. To illustrate that safety can be rigorously evaluated before vaccines are used on wild apes, we conducted what is, to our knowledge, the first conservation-oriented vaccine trial on captive chimpanzees. We tested an experimental virus-like particle (VLP) vaccine against Ebola virus, a leading killer of wild apes. Our trial illustrates both the ape conservation value that will be lost if efforts to end vaccine trials on captive chimpanzee are successful and the broader potential that noninfectious VLP vaccines have in other wildlife applications.

We examined six historical specimens of the endangered North Atlantic right whale (Eubalaena glacialis) using DNA isolated from documented baleen plates from the late nineteenth and early twentieth centuries. Sequences from the mitochondrial DNA (mtDNA) control region from these samples were compared with those from a near-exhaustive survey (269 of approximately 320 individuals) of the remaining right whales in the western North Atlantic Ocean. Our results suggest that there has been only relatively modest change in maternal lineage diversity over the past century in the North Atlantic right whale population. Any significant reduction in genetic variation in the species most likely occurred prior to the late nineteenth century. One historical specimen was from the last documented female capable of propagating one of the maternal lineages in the population today; no females in the existing population have been found to carry this mtDNA haplotype. Analysis of the only specimens from the eastern North Atlantic right whale population ever to be examined revealed that eastern and western North Atlantic right whales may not have been genetically differentiated populations. Loss of gene diversity experienced by North Atlantic right whales over the last century has been modest, and the six decades of protection have been successful in maintaining much of the maternal lineage diversity that was present in the late nineteenth century. Resumen: Examinamos seis especimenes historicos de la ballena franca septentrional Eubalaena glacialis del Atlantico Norte, usando ADN aislado de placas de las barbas documentadas de finales de siglo diecinueve y principios del siglo veinte. Las secuencias del ADN mitocondrial (mtADN) de la region control de estas muestras comparadas con aquellas de una muestra casi exhaustiva (269 de aproximadamente 320 individuos) de las ballenas francas remanentes en el oceano Atlantico Norte Occidental. Nuestros resultados sugieren que solo ha habido ligeros cambios en la diversidad del linaje materno a lo largo del siglo pasado. Probablemente, cualquier reduccion en la variacion genetica en las especies ocurrio antes del final del siglo diecinueve. Uno de los especimenes historicos fue de la ultima hembra documentada capaz de propagar uno de los linajes maternos en la poblacion actual. Ninguna de las hembras en las poblaciones existentes ha sido identificada como portadora de este haplotipo de mtADN. El analisis de los especimenes de la poblacion de ballenas del Atlantico Norte Oriental examinados revelan que las ballenas francas del este y del oeste del Atlantico Norte podrian no haber sido poblaciones geneticamente diferentes. La perdida de diversidad genetica experimentada en las poblaciones de ballena franca del Atlantico Norte a lo largo del siglo pasado ha sido modesta y las seis decadas de proteccion han sido exitosas en el mantenimiento de la mayoria de la diversidad del linaje materno que estaba presente a finales del siglo diecinueve.

Use of the phylogenetic species concept in defining conservation units is based on the assumption that the fixation of a particular character state in a population is diagnostic of a long history of reproductive isolation. In practice, diagnosis is usually based on the character states of a small sample of individuals rather than the states of the entire population. Unfortunately, when sample sizes are small, samples in which all individuals share one character state can easily be drawn from populations that are actually polymorphic. I describe statistical methods for examining how much confidence can be placed in the diagnosis of a conservation unit, given the operative sample size. The methods estimate the probability of drawing a sample in which all individuals show the same state, if individuals with unsampled ( hidden) states actually exist in the population at some hypothetical frequency (e.g., 0.05). I considered finite and infinite population-size models. The infinite population-size model suggests that in order to reject with 95% confidence the hypothesis that 5% of individuals carry hidden character states, a sample of 59 individuals is necessary. Finite population-size models give slightly smaller critical sample sizes for diagnosis with 95% confidence. I describe methods for including the effect of uncertainty in estimating population size when calculating critical sample size, and I discuss extensions to multiple characters and the impact of spatial structuring of character states. My results suggest that confident diagnosis requires sample sizes much larger than those commonly used when the phylogenetic species concept is applied to defining conservation units. Resumen: El uso del concepto de especie filogenetica en la definicion de unidades de conservacion se basa en el supuesto de que la fijacion de una caracteristica particular en una poblacion sea un diagnostico de una larga historia de aislamiento reproductivo. En la practica, el diagnostico se basa por lo general en las caracteristicas de una muestra pequena de individuos y no en las condiciones de la poblacion en su totalidad. Desafortunadamente, cuando los tamanos de muestra son pequenos, las muestras en las que todos los individuos comparten una caracteristica pueden ser facilmente extraidas de poblaciones que son en realidad polimorficas. En este trabajo describo los metodos estadisticos para examinar cuanta confianza puede ser puesta en el diagnostico de una unidad de conservacion, dado el tamano poblacional operativo. Los metodos estiman la probabilidad de extraccion de una muestra en la cual todos los individuos muestran la misma caracteristica y existen individuos con una condicion no muestreada (escondida) en la poblacion a una frecuencia hipotetica ( por ejemplo, 0.05). Considere modelos con tamanos poblacionales finitos e infinitos. El modelo con tamano poblacional infinito sugiere que para rechazar con un 95% de confianza la hipotesis de que 5% de los individuos poseen caracteristicas escondidas, se necesita un tamano de muestra de 59 individuos. El modelo con tamano poblacional finito dio tamanos de muestra criticos ligeramente menores para un diagnostico con un 95% de confianza. Se describen los metodos para incluir el efecto de la incertidumbre en la estimacion del tamano poblacional cuando se calcula el tamano de muestra critico. Las extensiones a caracteristicas multiples y el impacto de la estructura espacial sobre las caracteristicas es tambien discutido. Mis resultados sugieren que un diagnostico confiable requiere de tamanos de muestra mucho mas grandes que aquellos comunmente usados cuando se aplica el concepto de especie filogenetica a la definicion de unidades de conservacion.

The decision by the Convention on International Trade in Endangered Species (CITES) to condition a limited sale of ivory on the status of elephant poaching has brought into sharp focus the technical, organizational, and financial challenges inherent in setting up a continent-wide monitoring program. The task will be particularly arduous in central Africa, where forest elephant populations are difficult to monitor and the infrastructure necessary for population monitoring is lacking. The magnitude of effort that will be necessary is illustrated by an elephant survey done in the Gamba Complex, a network of protected areas on the southwest coast of Gabon. Implementing the survey required a large-scale program for training Gabonese nationals in field survey and analysis methods necessary for elephant monitoring. Field work carried out during the training program suggests that a combination of reconnaissance and line transects can produce statistically valid population estimates for a substantially lower effort than line transects alone. We illustrate statistical frameworks for comparing the efficiency of alternative sampling methods, and we analyze the sensitivity of current survey methods, which can detect abundance changes on the order of 15%, given fairly high effort levels. Although these training and methodological results are encouraging, they are just small steps in a complex and ongoing process. We argue that this process has many parallels with what needs to be done if the international conservation community is to respond to the challenge set for it by the 1997 CITES meeting. There must be a concerted effort focused both on improving survey methods and on developing the human resources and on-the-ground infrastructure necessary to implement these methods. Resumen: La decision del CITES de condicionar una venta limitada de marfil en base a la situacion de la caza furtiva de elefantes, ha conducido hacia un enfoque fino de los retos tecnicos, organizacionales y financieros inherentes al establecimiento de un programa de monitoreo a nivel continental. La tarea sera particularmente ardua en Africa central donde las poblaciones de elefantes en bosques son dificiles de monitorear y donde se carece de la infraestructura necesaria para el monitoreo de poblaciones. La magnitud del esfuerzo que se necesita es ilustrado por el estudio de elefantes llavado a cabo en el complejo Gamba, una red de areas protegidas de la costa suroeste de Gabon. La implementacion del estudio ha requerido de un programa de gran escala para el entrenamiento de ciudadanos gaboneses, en lo que respecta a monitoreo en campo y metodos de analisis necesarios para estudios de elefantes. El trabajo de campo llevado a cabo durante el entrenamiento sugiere que una combinacion de reconocimientos y transectos en linea puede producir estimaciones poblacionales estadisticamente validas para un esfuerzo sustancialmente mas bajo que los transectos en linea por si solos. Ilustramos marcos conceptuales estadisticos para comparar la eficiencia de metodos de muestreo alternativos y analizamos la sensibilidad de los metodos de muestreo actuales, los cuales pueden detectar cambios en la abundancia en un orden del 15%, dados valores de esfuerzo elevados. Aunque estos resultados de entrenamientos y metodologias son alentadores, son solo pequenos pasos de un proceso complejo continuo. Argumentamos que este proceso tiene mucho paralelismo con las necesidades que seran requeridas si la comunidad de conservacion internacional responde a los retos establecidos por la reunion del CITES 1997. Debera existir un esfuerzo concertado enfocado tanto al mejoramiento de tecnicas de muestreo como al desarrollo de recursos humanos y de infraestrcutura en sitio necesaria para implementar estos metodos.

Principles of self-organization play an increasingly central role in models of human activity. Notably, individual human displacements exhibit strongly recurrent patterns that are characterized by scaling laws and can be mechanistically modelled as self-attracting walks. Recurrence is not, however, unique to human displacements. Here we report that the mobility patterns of wild capuchin monkeys are not random walks and exhibit recurrence properties similar to those of cell phone users, suggesting spatial cognition mechanisms shared with humans. We also show that the highly uneven visitation patterns within monkey home ranges are not entirely self-generated but are forced by spatio-temporal habitat heterogeneities. If models of human mobility are to become useful tools for predictive purposes, they will need to consider the interaction between memory and environmental heterogeneities., 18 pages, 3 figures

Infectious disease has recently joined poaching and habitat loss as a major threat to African apes. Both “naturally” occurring pathogens, such as Ebola and Simian Immunodeficiency Virus (SIV), and respiratory pathogens transmitted from humans, have been confirmed as important sources of mortality in wild gorillas and chimpanzees. While awareness of the threat has increased, interventions such as vaccination and treatment remain controversial. Here we explore both the risk of disease to African apes, and the status of potential responses. Through synthesis of published data, we summarize prior disease impact on African apes. We then use a simple demographic model to illustrate the resilience of a well-known gorilla population to disease, modeled on prior documented outbreaks. We found that the predicted recovery time for this specific gorilla population from a single outbreak ranged from 5 years for a low mortality (4%) respiratory outbreak, to 131 years for an Ebola outbreak that killed 96% of the population. This shows that mortality rates comparable to those recently reported for disease outbreaks in wild populations are not sustainable. This is particularly troubling given the rising pathogen risk created by increasing habituation of wild apes for tourism, and the growth of human populations surrounding protected areas. We assess potential future disease spillover risk in terms of vaccination rates amongst humans that may come into contact with wild apes, and the availability of vaccines against potentially threatening diseases. We discuss and evaluate non-interventionist responses such as limiting tourist access to apes, community health programs, and safety, logistic, and cost issues that constrain the potential of vaccination.

Chimpanzees and gorillas are the only nonhuman primates known to harbor viruses closely related to HIV-1. Phylogenetic analyses showed that gorillas acquired the simian immunodeficiency virus SIVgor from chimpanzees, and viruses from the SIVcpz/SIVgor lineage have been transmitted to humans on at least four occasions, leading to HIV-1 groups M, N, O, and P. To determine the geographic distribution, prevalence, and species association of SIVgor, we conducted a comprehensive molecular epidemiological survey of wild gorillas in Central Africa. Gorilla fecal samples were collected in the range of western lowland gorillas ( n = 2,367) and eastern Grauer gorillas ( n = 183) and tested for SIVgor antibodies and nucleic acids. SIVgor antibody-positive samples were identified at 2 sites in Cameroon, with no evidence of infection at 19 other sites, including 3 in the range of the Eastern gorillas. In Cameroon, based on DNA and microsatellite analyses of a subset of samples, we estimated the prevalence of SIVgor to be 1.6% (range, 0% to 4.6%), which is significantly lower than the prevalence of SIVcpz Ptt in chimpanzees (5.9%; range, 0% to 32%). All newly identified SIVgor strains formed a monophyletic lineage within the SIVcpz radiation, closely related to HIV-1 groups O and P, and clustered according to their field site of origin. At one site, there was evidence for intergroup transmission and a high intragroup prevalence. These isolated hot spots of SIVgor-infected gorilla communities could serve as a source for human infection. The overall low prevalence and sporadic distribution of SIVgor could suggest a decline of SIVgor in wild populations, but it cannot be excluded that SIVgor is still more prevalent in other parts of the geographical range of gorillas.

In 2004 the Ebola virus caused a drastic decline in western gorilla Gorilla gorilla abundance at Lokoue Bai, a clearing in Odzala National Park, Republic of Congo. This decline was detected by observations of gorillas visiting the clearing. We confirm that the sympatric chimpanzee Pan troglodytes population was also affected by the Ebola outbreak, and test whether the decline in the ape population would have been detected with line-transect surveys, the most commonly used wildlife monitoring methodology in Central Africa. We also evaluate the potential of transect surveys for describing the extent and pinpointing the timing of drastic population declines when this information is not known from other evidence. Both nest survey using the marked nest count method and standing stock survey of other signs of ape presence (dung, feeding remains, prints) were able to detect the decline. However, only nests and dung were reliable indices for estimating the magnitude of the decline and accurately pinpointing the timing. It was necessary to pool data across many survey replicates because of small samples sizes. Our results suggest that transects methods are able to detect drastic changes in ape abundance but that large sample sizes are necessary to achieve adequate statistical power. We therefore recommend that those intending to use transect methods as tools for monitoring large forest mammals evaluate in advance how much effort will be necessary to detect meaningful changes in animal abundance. © 2008 Fauna & Flora International.

Chimpanzees have been used extensively as a model system for laboratory research on infectious diseases. Ironically, we know next to nothing about disease dynamics in wild chimpanzee populations. Here, we analyze long-term demographic and behavioral data from two habituated chimpanzee communities in Tai National Park, Cote d'Ivoire, where previous work has shown respiratory pathogens to be an important source of infant mortality. In this paper we trace the effect of social connectivity on infant mortality dynamics. We focus on social play which, as the primary context of contact between young chimpanzees, may serve as a key venue for pathogen transmission. Infant abundance and mortality rates at Tai cycled regularly and in a way that was not well explained in terms of environmental forcing. Rather, infant mortality cycles appeared to self-organize in response to the ontogeny of social play. Each cycle started when the death of multiple infants in an outbreak synchronized the reproductive cycles of their mothers. A pulse of births predictably arrived about twelve months later, with social connectivity increasing over the following two years as the large birth cohort approached the peak of social play. The high social connectivity at this play peak then appeared to facilitate further outbreaks. Our results provide the first evidence that social play has a strong role in determining chimpanzee disease transmission risk and the first record of chimpanzee disease cycles similar to those seen in human children. They also lend more support to the view that infectious diseases are a major threat to the survival of remaining chimpanzee populations.

Most populations of colonial birds exhibit extensive variation in colony size. Field studies over the last decade have shown that individual birds breeding in colonies of certain sizes are apparently more successful than those settling in colonies of other sizes, yet size variation persists. Enough information is now available to suggest four explanations for how birds choose colonies and why colonies vary in size.

Summary Commercial hunting and habitat loss are major drivers of the rapid decline of great apes [1]. Ecotourism and research have been widely promoted as a means of providing alternative value for apes and their habitats [2]. However, close contact between humans and habituated apes during ape tourism and research has raised concerns that disease transmission risks might outweigh benefits [3–7]. To date only bacterial and parasitic infections of typically low virulence have been shown to move from humans to wild apes [8, 9]. Here, we present the first direct evidence of virus transmission from humans to wild apes. Tissue samples from habituated chimpanzees that died during three respiratory-disease outbreaks at our research site, Cote d'Ivoire, contained two common human paramyxoviruses. Viral strains sampled from chimpanzees were closely related to strains circulating in contemporaneous, worldwide human epidemics. Twenty-four years of mortality data from observed chimpanzees reveal that such respiratory outbreaks could have a long history. In contrast, survey data show that research presence has had a strong positive effect in suppressing poaching around the research site. These observations illustrate the challenge of maximizing the benefit of research and tourism to great apes while minimizing the negative side effects.

Over the past decade Ebola hemorrhagic fever has emerged repeatedly in Gabon and Congo, causing numerous human outbreaks and massive die‐offs of gorillas and chimpanzees. Why Ebola has emerged so explosively remains poorly understood. Previous studies have tended to focus on exogenous factors such as habitat disturbance and climate change as drivers of Ebola emergence while downplaying the contribution of transmission between gorilla or chimpanzee social groups. Here we report recent observations on behaviors that pose a risk of transmission among gorilla groups and between gorillas and chimpanzees. These observations support a reassessment of ape‐to‐ape transmission as an amplifier of Ebola outbreaks.

Identifying a natural reservoir for Ebola virus has eluded researchers for decades [1,2]. Recently, Leroy et al. presented the most compelling evidence to date that three species of fruit bats (Hypsignathus monstrosus, Epomops franqueti, and Myonycteris torquata) may constitute a long-missing wildlife reservoir for Ebola virus Zaire (EBOVZ) [3]. These bats, caught near affected villages at the Gabon–Congo border, appear to have been asymptomatically infected and, in seven cases, yielded virus sequences that closely matched those found in the human outbreaks happening about the same time. Leroy et al.'s phylogenetic analysis of the partial sequences of the viral polymerase (L) gene derived from humans and bats emphasized the interspecific relationships to related filoviruses. Here, we show that (1) despite their short length (265 bp), these sequences also provide critical information about the intraspecific history of EBOVZ, and (2) based on the genetic data available so far, the association of the virus with fruit bats in the sampled area can only be traced back a few years. Consistent with previous analysis using glycoprotein (GP) gene sequences [4], results for the L gene show that viruses amplified from more recently collected samples appear to be direct descendents of viruses seen during previous outbreaks. This relationship is not only apparent for viruses found in 1976–1995 compared with those found in 2001–2003, but also within the latter group (Figure 1). In essence, this means that all genetic variation seen thus far in EBOVZ, including virus amplified from fruit bats, appears to be the product of mutations that have accumulated within the last 30 years. Finding such strong evidence for temporal structure by chance seems highly unlikely, especially given the concordance with our earlier results from the GP gene [4]. Although the lack of any mutational differences between the sequences Mayinga 1976 and Kikwit 1995 is perplexing in this context, it is most likely a stochastic artifact due to the short length of the sequence considered. Full-length sequences are available for both these isolates, which over the entire genome are 1.2% different. Over 19 years this yields an ad hoc evolutionary rate estimate of 6.2 × 10−4 substitutions per site per year, close to the rate we had previously estimated for the GP gene (~8.0 × 10−4) [4] and to the point estimate for all partial L sequences in the current analysis (1.1 × 10−3; 95% highest posterior density interval: 6.3 × 10−7 to 2.4 × 10−3). Thus, even though the L sequences are rather short, they yield evolutionary rate estimates similar to the longer GP sequences. Figure 1 Maximum Likelihood Tree from Partial L Sequences of Ebola Virus Zaire The temporal structure visible in the L gene genealogy implies that all viruses sampled from both humans and bats between 2001 and 2003 can be traced back to a very recent common ancestor, by which we mean a recent coalescence of genetic lineages, not an ancestral alternative reservoir species. In fact, according to our phylogenetic estimate, the partial L sequence of this genetic ancestor would have looked identical to that sampled from infected humans during outbreaks in late 2001 and early 2002 (Entsiami and Mendemba, Figure 1), suggesting that this ancestor could not be much older. This is in agreement with the previous analysis of the GP gene, which indicated that all viruses sampled from outbreaks since 2001 had a most recent common ancestor in 1999 (confidence region: 1998–2000) [4]. While these findings do not question whether fruit bats may represent a wild reservoir for EBOVZ, they do raise important issues. If the three identified fruit bat hosts were the natural reservoir for EBOVZ, the recent common ancestry of all sequences derived from them so far is surprising because, at least at first sight, it seems to contradict the idea of a long-established association of bat and virus. The most reasonable explanation for this result is that the virus experienced a recent genetic bottleneck. We present three alternative scenarios of what could have caused such a bottleneck. One possibility is that somewhere around 1999, the total number of infected bats within the sampled area became extremely small (likely much less than the peak 23% incidence determined by Leroy et al.). Under such a scenario, the most recent common ancestor could not be traced back further into the past because an extremely small, effective viral population size has caused the descendents of all but one of the previously existing viral lineages to be lost. Since no trapping study on bats was undertaken before 2001, we could not directly address this issue. However, some epidemiological and virological observations may account for this situation. The need to apply the very sensitive nested PCR to detect viral RNA suggests a very low viral load in organs of infected bats. Furthermore, the presence of a high prevalence rate of seropositive bats (16.7%, 4/24) compared with only 3.2% (2/63) that were PCR positive (but seronegative) just three months after the appearance of the first human cases in Mendemba, Gabon, indicates that viral replication within bats may be highly restricted and possibly only taking place prior to the onset of the host immune response. Especially if infections are synchronized, for example, by some environmental trigger, this may lead to periods with an extremely small number of productively infected bats, repeatedly forcing the virus population through a genetic bottleneck. Alternatively, the recent common ancestor could be explained by infected bats introducing the virus into the EBOVZ-affected area of Gabon and Congo around 1999. Previous results for the GP gene actually support this hypothesis by revealing a consistent signature of geographic spread within the spatial, temporal, and genetic data for EBOVZ over the last 30 years [4]. Similar genetic patterns associated with local founder events followed by spatial spread have also been documented from rabies virus in wildlife host populations [5]. Some observed epidemiological changes in sampled bat populations over time may also support this hypothesis. Leroy et al. found that during the first visit to one of their sampling locations, 23% (7/31) of the bats were PCR positive, whereas 0% (0/10) were seropositive. At a second visit five months later, these numbers had changed to 2% (4/184) and 8% (12/160) [3]. Again, no bats were positive by both PCR and serology. Though other factors may also explain these opposing trends, the observed temporal pattern is consistent with an infection wave moving through the sampled population, resulting in a high proportion of infectious individuals at first, followed by an increased proportion of seropositive animals. Given that the three implicated fruit bat species may not be the only reservoir for EBOVZ, as Leroy et al. were already careful to point out [3], another possible explanation for the existence of a common viral ancestor in the recent past is that the virus was introduced to these fruit bats around the same time it affected other wildlife populations and emerged in humans. It is important to note that this scenario does not rule out bats as reservoir species, a hypothesis for which there is additional independent support [6]. Instead, it would imply that the primary reservoir of EBOVZ, whether it involves additional bat species or representatives of other taxonomic groups, has yet to be found. We expect that distinguishing between these possible scenarios will become increasingly easier as more temporal, spatial, and genetic data are generated. Additional viral sequences from infected fruit bats and large-scale serological prevalence in bat populations both within and outside the affected area should give some much needed answers regarding the dynamics of the virus in its wild reservoir. Together with other viral sequences in human cases and vulnerable animal species, and a better understanding of the factors associated with its emergence in human and wildlife populations, these combined approaches will hopefully lead to new and more successful strategies for preventing and controlling outbreaks of EBOVZ in the near future.

Background The spread of infectious diseases in wildlife populations is influenced by patterns of between-host contacts. Habitat “hotspots” - places attracting a large numbers of individuals or social groups - can significantly alter contact patterns and, hence, disease propagation. Research on the importance of habitat hotspots in wildlife epidemiology has primarily focused on how inter-individual contacts occurring at the hotspot itself increase disease transmission. However, in territorial animals, epidemiologically important contacts may primarily occur as animals cross through territories of conspecifics en route to habitat hotspots. So far, the phenomenon has received little attention. Here, we investigate the importance of these contacts in the case where infectious individuals keep visiting the hotspots and in the case where these individuals are not able to travel to the hotspot any more. Methodology and Principal Findings We developed a simulation epidemiological model to investigate both cases in a scenario when transmission at the hotspot does not occur. We find that (i) hotspots still exacerbate epidemics, (ii) when infectious individuals do not travel to the hotspot, the most vulnerable individuals are those residing at intermediate distances from the hotspot rather than nearby, and (iii) the epidemiological vulnerability of a population is the highest when the number of hotspots is intermediate. Conclusions and Significance By altering animal movements in their vicinity, habitat hotspots can thus strongly increase the spread of infectious diseases, even when disease transmission does not occur at the hotspot itself. Interestingly, when animals only visit the nearest hotspot, creating additional artificial hotspots, rather than reducing their number, may be an efficient disease control measure.

Your News in Brief item ‘Cancer forces Tasmanian devil onto endangered list’ highlights the plight of this carnivorous marsupial (Sarcophilus harrisii), driven towards extinction by devil facial-tumour disease, which is contagious

Over the past decade, the Zaire strain of Ebola virus (ZEBOV) has repeatedly emerged in Gabon and Congo. Each human outbreak has been accompanied by reports of gorilla and chimpanzee carcasses in neighboring forests, but both the extent of ape mortality and the causal role of ZEBOV have been hotly debated. Here, we present data suggesting that in 2002 and 2003 ZEBOV killed about 5000 gorillas in our study area. The lag between neighboring gorilla groups in mortality onset was close to the ZEBOV disease cycle length, evidence that group-to-group transmission has amplified gorilla die-offs.

There is an urgent need for information on western gorilla population sizes and distribution to improve present and plan future conservation actions. Researchers traditionally have estimated gorilla densities on the basis of nest counts despite demonstrated variation in nest production and decay rates. The variation may lead to large biases in estimates of gorilla abundance. We investigated the use of an alternate index of gorilla abundance, via defecation data collected from habituated gorillas at Bai Hokou, Central African Republic. Our sample of 274/370 defecation events/dung piles produced a production rate of ca. 5 dung piles/d: comparable to previous estimates based on much smaller sample sizes. Heuristic models that failed to account for imperfect dung pile detection produced a lower defecation rate estimate than that of a maximum likelihood model that explicitly modeled detection probability. Generalized linear modeling (GLM) showed that dung pile production rate was strongly linked to rainfall, suggesting that failure to correct for seasonal variation in dung pile production rates could lead to substantial biases in gorilla abundance estimates. In our study, failing to distinguish between the number of defecation events and the number of dung piles produced would lead to a ca. 31% overestimate of true gorilla numbers. The use of dung as an index of gorilla abundance shows potential, but more fieldwork and modeling on seasonal variation in dung production rates is required.

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International audience; Plasmodium vivax is the leading cause of human malaria in Asia and Latin America but is absent from most of central Africa due to the near fixation of a mutation that inhibits the expression of its receptor, the Duffy antigen, on human erythrocytes. The emergence of this protective allele is not understood because P. vivax is believed to have originated in Asia. Here we show, using a noninvasive approach, that wild chimpanzees and gorillas throughout central Africa are endemically infected with parasites that are closely related to human P. vivax. Sequence analyses reveal that ape parasites lack host specificity and are much more diverse than human parasites, which form a monophyletic lineage within the ape parasite radiation. These findings indicate that human P. vivax is of African origin and likely selected for the Duffy-negative mutation. All extant human P. vivax parasites are derived from a single ancestor that escaped out of Africa.