ObjectivesSeveral theories have been proposed to explain the impact of ecological conditions on d... more ObjectivesSeveral theories have been proposed to explain the impact of ecological conditions on differences in life history variables within and between species. Here we compare female life history parameters of one western lowland gorilla population (Gorilla gorilla gorilla) and two mountain gorilla populations (Gorilla beringei beringei).Materials and MethodsWe compared the age of natal dispersal, age of first birth, interbirth interval, and birth rates using long‐term demographic datasets from Mbeli Bai (western gorillas), Bwindi Impenetrable National Park and the Virunga Massif (mountain gorillas).ResultsThe Mbeli western gorillas had the latest age at first birth, longest interbirth interval, and slowest surviving birth rate compared to the Virunga mountain gorillas. Bwindi mountain gorillas were intermediate in their life history patterns.DiscussionThese patterns are consistent with differences in feeding ecology across sites. However, it is not possible to determine the evolu...
The earliest stone tool types, sharp flakes knapped from stone cores, are assumed to have played ... more The earliest stone tool types, sharp flakes knapped from stone cores, are assumed to have played a crucial role in human cognitive evolution. Flaked stone tools have been observed to be accidentally produced when wild monkeys use handheld stones as tools. Holding a stone core in hand and hitting it with another in the absence of flaking,free hand hitting,has been considered a requirement for producing sharp stone flakes by hitting stone on stone,free hand percussion. We report on five observations offree hand hittingbehavior in two wild western gorillas, using stone-like objects (pieces of termite mound). Gorillas are therefore the second non-human lineage primate showing free-hand hitting behavior in the wild, and ours is the first report for free hand hitting behavior in wild apes. This study helps to shed light on the morphofunctional and cognitive requirements for the emergence of stone tool production as it shows that a prerequisite for free hand percussion (namely, free hand h...
Studies of the evolutionary relationships among gorilla populations using autosomal and mitochond... more Studies of the evolutionary relationships among gorilla populations using autosomal and mitochondrial sequences suggest that male‐mediated gene flow may have been important in the past, but data on the Y‐chromosomal relationships among the gorilla subspecies are limited. Here, we genotyped blood and noninvasively collected fecal samples from 12 captives and 257 wild male gorillas of known origin representing all four subspecies (Gorilla gorilla gorilla, G. g. diehli, G. beringei beringei, and G. b. graueri) at 10 Y‐linked microsatellite loci resulting in 102 unique Y‐haplotypes for 224 individuals. We found that western lowland gorilla (G. g. gorilla) haplotypes were consistently more diverse than any other subspecies for all measures of diversity and comprised several genetically distinct groups. However, these did not correspond to geographical proximity and some closely related haplotypes were found several hundred kilometers apart. Similarly, our broad sampling of eastern gorill...
Primate populations are declining throughout tropical Africa. Great apes are threatened from exti... more Primate populations are declining throughout tropical Africa. Great apes are threatened from extinction despite the existence of wildlife laws that fully protect them in their range states. But, due to a lack of knowledge and understanding of these laws, they remain largely ineffective. There is, therefore, a crucial need to improve awareness of wildlife laws in Congo. We conducted an education campaign and tested the effectiveness of two communication tools (wildlife law flyer and gorilla/pet‐trade comic book) in increasing school children's knowledge in rural and urban settings using evaluation questionnaires. We found extremely low precampaign knowledge of wildlife laws but detected a moderate increase of knowledge attributed to our communication tools. We discuss the usefulness of different communication tools and their relevance for knowledge increase with different audiences. Our study provides insights into the design of education campaigns, most notably the use of flyers...
1. Department of Archaeology, University of Cambridge, Downing Street, Cambridge, CB2 3DZ 2. Mbel... more 1. Department of Archaeology, University of Cambridge, Downing Street, Cambridge, CB2 3DZ 2. Mbeli Bai Study, Wildlife Conservation Society Congo Program, B.P. 14537 Brazzaville, Republic of Congo 3. World Wide Fund for Nature, Reinhardtstrasse 18, 10117 Berlin, Germany 4. Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany 5. Apes Incorporated, 5301 Westbard Circle, Bethesda, MD 20816
Is it possible to slow the rate of aging, or do biological constraints limit its plasticity? We t... more Is it possible to slow the rate of aging, or do biological constraints limit its plasticity? We test this ‘invariant rate of aging’ hypothesis with an unprecedented collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifespan equality seen in humans. We next demonstrate that variation in the rate of aging within genera is orders of magnitude smaller than variation in pre-adult and age-independent mortality. Finally, we demonstrate that changes in the rate of aging, but not other mortality parameters, produce striking, species-atypical changes in mortality patterns. Our results support the invariant rate of aging hypothesis, implying biological constraints on how much the human rate of aging can be slowed.
Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We ... more Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We test the ‘invariant rate of ageing’ hypothesis, which posits that the rate of ageing is relatively fixed within species, with a collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifespan equality seen in humans. We next demonstrate that variation in the rate of ageing within genera is orders of magnitude smaller than variation in pre-adult and age-independent mortality. Finally, we demonstrate that changes in the rate of ageing, but not other mortality parameters, produce striking, species-atypical changes in mortality patterns. Our results support the invariant rate of ageing hypothesis, implying biological constraints on how much the human rate of ageing can be slowed.
Proceedings of the Royal Society B: Biological Sciences, 2019
Modern human societies show hierarchical social modularity (HSM) in which lower-order social unit... more 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 ...
We present a range-wide assessment of sympatric western lowland gorillas and central chimpanzees ... more We present a range-wide assessment of sympatric western lowland gorillas and central chimpanzees using the largest survey data set ever assembled for these taxa: 59 sites in five countries surveyed between 2003 and 2013, totaling 61,000 person-days of fieldwork. We used spatial modeling to investigate major drivers of great ape distribution and population trends. We predicted density across each taxon's geographic range, allowing us to estimate overall abundance: 361,900 gorillas and 128,700 chimpanzees in Western Equatorial Africa-substantially higher than previous estimates. These two subspecies represent close to 99% of all gorillas and one-third of all chimpanzees. Annual population decline of gorillas was estimated at 2.7%, maintaining them as Critically Endangered on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List. We quantified the threats to each taxon, of which the three greatest were poaching, disease, and habitat degradation. G...
Overexploitation is one of the main pressures driving wildlife closer to extinction, yet broad‐sc... more Overexploitation is one of the main pressures driving wildlife closer to extinction, yet broad‐scale data to evaluate species’ declines are limited. Using African pangolins (Family: Pholidota) as a case study, we demonstrate that collating local‐scale data can provide crucial information on regional trends in exploitation of threatened species to inform conservation actions and policy. We estimate that 0.4‐2.7 million pangolins are hunted annually in Central African forests. The number of pangolins hunted has increased by ∼150% and the proportion of pangolins of all vertebrates hunted increased from 0.04% to 1.83% over the past four decades. However, there were no trends in pangolins observed at markets, suggesting use of alternative supply chains. The price of giant (Smutsia gigantea) and arboreal (Phataginus sp.) pangolins in urban markets has increased 5.8 and 2.3 times respectively, mirroring trends in Asian pangolins. Efforts and resources are needed to increase law enforcement...
Human–elephant conflict is a common conservation problem throughout Africa, but poorly studied wh... more Human–elephant conflict is a common conservation problem throughout Africa, but poorly studied where forest elephants (Loxodonta cyclotis) occur. Here, we investigated people's perceptions towards the impact of elephants around Nouabalé‐Ndoki National Park, northern Congo. We aimed to understand the perceptual differences amongst residents of four villages that varied substantially in the degree of conservation benefits received. We used a multivariate analysis to investigate how socio‐economic variables, such as employment, wealth, education and ethnicity, influenced perceptions. Using both quantitative and qualitative data, we found that the majority of respondents experienced elephant impacts, mainly through crop raiding. Residents of the village where the local conservation project is based had significantly more positive perceptions of elephants, whereas perceptions of farmers were mostly negative. We identified some misunderstandings regarding the responsibilities of eleph...
Conservation education can play a vital role in increasing knowledge and changing attitudes towar... more Conservation education can play a vital role in increasing knowledge and changing attitudes towards the value of wildlife [Jacobsen et al., 2006]. When combined with other activities, such as law enforcement, access to alternative protein resources, and an increase in the standard of living conditions it can be an important long-term tool that reinforces behavioral changes needed to effectively protect great apes and other wildlife in Central Africa [Tutin et al., 2005]. Nature or wildlife clubs often act as an initial approach for providing environmental education [Dolins et al., this issue; McDuff & Jacobson, 2000]. Increasing the knowledge of children is a prerequisite to reduce the likelihood that the current generation will consume or trade great ape bushmeat in the future, because adult attitudes and behaviors are largely based on childhood experiences [e.g. Jacobsen et al., 2006; Kidd & Kidd, 1989; McDuff & Jacobson, 2000]. It has been shown that higher education and knowledge have a positive influence on attitudes of wildlife and conservation issues in northern Congo [Riddel, 2005]. But there is a substantial lack of knowledge of existing wildlife laws and environmental problems such as nonsustainable bushmeat consumption [e.g. Noss, 1997; Poulsen et al., 2009; Riddel, 2005]. Environmental education is not a priority in the school curriculum and teachers often lack basic knowledge of ecology and evolution, as well as relevant teaching materials. Educational approaches, such as learning by doing, are relatively new to the Congolese education curriculum. Instead learning-by-rote system (learning by memorizing and repetition) is common in Congo’s schools. With a few exceptions, schools fail to offer students basic educational skills such as writing and math, which makes it challenging to introduce concepts of sustainability and conservation. Classes most often have too many students per teacher to make education effective. Teachers in public schools are often absent from the school because they have to search for additional income or to provide basic subsistence needs. Many children (particularly Ba-Aka pygmies) do not even attend school or spend prolonged periods in the forest [Riddell & Daley, in preparation]. There exists a high drop out rate due to the lack of regular funding for school fees and material. In Congo, young children regularly fish and teenagers often hunt bushmeat to be able to pay for basic school materials or fees to cover the costs of private schools where they can receive a higherquality education [Riddell & Daley, in preparation]. Girls often leave school at a very young age to attend to responsibilities in their household [see also Kasenene & Ross, 2008].
ObjectivesSeveral theories have been proposed to explain the impact of ecological conditions on d... more ObjectivesSeveral theories have been proposed to explain the impact of ecological conditions on differences in life history variables within and between species. Here we compare female life history parameters of one western lowland gorilla population (Gorilla gorilla gorilla) and two mountain gorilla populations (Gorilla beringei beringei).Materials and MethodsWe compared the age of natal dispersal, age of first birth, interbirth interval, and birth rates using long‐term demographic datasets from Mbeli Bai (western gorillas), Bwindi Impenetrable National Park and the Virunga Massif (mountain gorillas).ResultsThe Mbeli western gorillas had the latest age at first birth, longest interbirth interval, and slowest surviving birth rate compared to the Virunga mountain gorillas. Bwindi mountain gorillas were intermediate in their life history patterns.DiscussionThese patterns are consistent with differences in feeding ecology across sites. However, it is not possible to determine the evolu...
The earliest stone tool types, sharp flakes knapped from stone cores, are assumed to have played ... more The earliest stone tool types, sharp flakes knapped from stone cores, are assumed to have played a crucial role in human cognitive evolution. Flaked stone tools have been observed to be accidentally produced when wild monkeys use handheld stones as tools. Holding a stone core in hand and hitting it with another in the absence of flaking,free hand hitting,has been considered a requirement for producing sharp stone flakes by hitting stone on stone,free hand percussion. We report on five observations offree hand hittingbehavior in two wild western gorillas, using stone-like objects (pieces of termite mound). Gorillas are therefore the second non-human lineage primate showing free-hand hitting behavior in the wild, and ours is the first report for free hand hitting behavior in wild apes. This study helps to shed light on the morphofunctional and cognitive requirements for the emergence of stone tool production as it shows that a prerequisite for free hand percussion (namely, free hand h...
Studies of the evolutionary relationships among gorilla populations using autosomal and mitochond... more Studies of the evolutionary relationships among gorilla populations using autosomal and mitochondrial sequences suggest that male‐mediated gene flow may have been important in the past, but data on the Y‐chromosomal relationships among the gorilla subspecies are limited. Here, we genotyped blood and noninvasively collected fecal samples from 12 captives and 257 wild male gorillas of known origin representing all four subspecies (Gorilla gorilla gorilla, G. g. diehli, G. beringei beringei, and G. b. graueri) at 10 Y‐linked microsatellite loci resulting in 102 unique Y‐haplotypes for 224 individuals. We found that western lowland gorilla (G. g. gorilla) haplotypes were consistently more diverse than any other subspecies for all measures of diversity and comprised several genetically distinct groups. However, these did not correspond to geographical proximity and some closely related haplotypes were found several hundred kilometers apart. Similarly, our broad sampling of eastern gorill...
Primate populations are declining throughout tropical Africa. Great apes are threatened from exti... more Primate populations are declining throughout tropical Africa. Great apes are threatened from extinction despite the existence of wildlife laws that fully protect them in their range states. But, due to a lack of knowledge and understanding of these laws, they remain largely ineffective. There is, therefore, a crucial need to improve awareness of wildlife laws in Congo. We conducted an education campaign and tested the effectiveness of two communication tools (wildlife law flyer and gorilla/pet‐trade comic book) in increasing school children's knowledge in rural and urban settings using evaluation questionnaires. We found extremely low precampaign knowledge of wildlife laws but detected a moderate increase of knowledge attributed to our communication tools. We discuss the usefulness of different communication tools and their relevance for knowledge increase with different audiences. Our study provides insights into the design of education campaigns, most notably the use of flyers...
1. Department of Archaeology, University of Cambridge, Downing Street, Cambridge, CB2 3DZ 2. Mbel... more 1. Department of Archaeology, University of Cambridge, Downing Street, Cambridge, CB2 3DZ 2. Mbeli Bai Study, Wildlife Conservation Society Congo Program, B.P. 14537 Brazzaville, Republic of Congo 3. World Wide Fund for Nature, Reinhardtstrasse 18, 10117 Berlin, Germany 4. Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany 5. Apes Incorporated, 5301 Westbard Circle, Bethesda, MD 20816
Is it possible to slow the rate of aging, or do biological constraints limit its plasticity? We t... more Is it possible to slow the rate of aging, or do biological constraints limit its plasticity? We test this ‘invariant rate of aging’ hypothesis with an unprecedented collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifespan equality seen in humans. We next demonstrate that variation in the rate of aging within genera is orders of magnitude smaller than variation in pre-adult and age-independent mortality. Finally, we demonstrate that changes in the rate of aging, but not other mortality parameters, produce striking, species-atypical changes in mortality patterns. Our results support the invariant rate of aging hypothesis, implying biological constraints on how much the human rate of aging can be slowed.
Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We ... more Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We test the ‘invariant rate of ageing’ hypothesis, which posits that the rate of ageing is relatively fixed within species, with a collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifespan equality seen in humans. We next demonstrate that variation in the rate of ageing within genera is orders of magnitude smaller than variation in pre-adult and age-independent mortality. Finally, we demonstrate that changes in the rate of ageing, but not other mortality parameters, produce striking, species-atypical changes in mortality patterns. Our results support the invariant rate of ageing hypothesis, implying biological constraints on how much the human rate of ageing can be slowed.
Proceedings of the Royal Society B: Biological Sciences, 2019
Modern human societies show hierarchical social modularity (HSM) in which lower-order social unit... more 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 ...
We present a range-wide assessment of sympatric western lowland gorillas and central chimpanzees ... more We present a range-wide assessment of sympatric western lowland gorillas and central chimpanzees using the largest survey data set ever assembled for these taxa: 59 sites in five countries surveyed between 2003 and 2013, totaling 61,000 person-days of fieldwork. We used spatial modeling to investigate major drivers of great ape distribution and population trends. We predicted density across each taxon's geographic range, allowing us to estimate overall abundance: 361,900 gorillas and 128,700 chimpanzees in Western Equatorial Africa-substantially higher than previous estimates. These two subspecies represent close to 99% of all gorillas and one-third of all chimpanzees. Annual population decline of gorillas was estimated at 2.7%, maintaining them as Critically Endangered on the International Union for Conservation of Nature and Natural Resources (IUCN) Red List. We quantified the threats to each taxon, of which the three greatest were poaching, disease, and habitat degradation. G...
Overexploitation is one of the main pressures driving wildlife closer to extinction, yet broad‐sc... more Overexploitation is one of the main pressures driving wildlife closer to extinction, yet broad‐scale data to evaluate species’ declines are limited. Using African pangolins (Family: Pholidota) as a case study, we demonstrate that collating local‐scale data can provide crucial information on regional trends in exploitation of threatened species to inform conservation actions and policy. We estimate that 0.4‐2.7 million pangolins are hunted annually in Central African forests. The number of pangolins hunted has increased by ∼150% and the proportion of pangolins of all vertebrates hunted increased from 0.04% to 1.83% over the past four decades. However, there were no trends in pangolins observed at markets, suggesting use of alternative supply chains. The price of giant (Smutsia gigantea) and arboreal (Phataginus sp.) pangolins in urban markets has increased 5.8 and 2.3 times respectively, mirroring trends in Asian pangolins. Efforts and resources are needed to increase law enforcement...
Human–elephant conflict is a common conservation problem throughout Africa, but poorly studied wh... more Human–elephant conflict is a common conservation problem throughout Africa, but poorly studied where forest elephants (Loxodonta cyclotis) occur. Here, we investigated people's perceptions towards the impact of elephants around Nouabalé‐Ndoki National Park, northern Congo. We aimed to understand the perceptual differences amongst residents of four villages that varied substantially in the degree of conservation benefits received. We used a multivariate analysis to investigate how socio‐economic variables, such as employment, wealth, education and ethnicity, influenced perceptions. Using both quantitative and qualitative data, we found that the majority of respondents experienced elephant impacts, mainly through crop raiding. Residents of the village where the local conservation project is based had significantly more positive perceptions of elephants, whereas perceptions of farmers were mostly negative. We identified some misunderstandings regarding the responsibilities of eleph...
Conservation education can play a vital role in increasing knowledge and changing attitudes towar... more Conservation education can play a vital role in increasing knowledge and changing attitudes towards the value of wildlife [Jacobsen et al., 2006]. When combined with other activities, such as law enforcement, access to alternative protein resources, and an increase in the standard of living conditions it can be an important long-term tool that reinforces behavioral changes needed to effectively protect great apes and other wildlife in Central Africa [Tutin et al., 2005]. Nature or wildlife clubs often act as an initial approach for providing environmental education [Dolins et al., this issue; McDuff & Jacobson, 2000]. Increasing the knowledge of children is a prerequisite to reduce the likelihood that the current generation will consume or trade great ape bushmeat in the future, because adult attitudes and behaviors are largely based on childhood experiences [e.g. Jacobsen et al., 2006; Kidd & Kidd, 1989; McDuff & Jacobson, 2000]. It has been shown that higher education and knowledge have a positive influence on attitudes of wildlife and conservation issues in northern Congo [Riddel, 2005]. But there is a substantial lack of knowledge of existing wildlife laws and environmental problems such as nonsustainable bushmeat consumption [e.g. Noss, 1997; Poulsen et al., 2009; Riddel, 2005]. Environmental education is not a priority in the school curriculum and teachers often lack basic knowledge of ecology and evolution, as well as relevant teaching materials. Educational approaches, such as learning by doing, are relatively new to the Congolese education curriculum. Instead learning-by-rote system (learning by memorizing and repetition) is common in Congo’s schools. With a few exceptions, schools fail to offer students basic educational skills such as writing and math, which makes it challenging to introduce concepts of sustainability and conservation. Classes most often have too many students per teacher to make education effective. Teachers in public schools are often absent from the school because they have to search for additional income or to provide basic subsistence needs. Many children (particularly Ba-Aka pygmies) do not even attend school or spend prolonged periods in the forest [Riddell & Daley, in preparation]. There exists a high drop out rate due to the lack of regular funding for school fees and material. In Congo, young children regularly fish and teenagers often hunt bushmeat to be able to pay for basic school materials or fees to cover the costs of private schools where they can receive a higherquality education [Riddell & Daley, in preparation]. Girls often leave school at a very young age to attend to responsibilities in their household [see also Kasenene & Ross, 2008].
Buffalo showed high site fidelity to open areas, including forest clearings. Forest buffalo herds... more Buffalo showed high site fidelity to open areas, including forest clearings. Forest buffalo herds (mean 12 ind. ± SD; range 3-24) were much smaller than records of savanna buffalo herds (mean 350 ind. ± SD; range 12-1500>), but also showed frequently fission-fusion patterns. Data from Mbeli Bai collected from 2006 to 2015 confirm a stable presence of two buffalo herds (range 7-9 ind.) with occasional visits by lone individuals. Observations from Dzanga Bai over a period of 23 years (1993-2016) confirm the occurrence of only one buffalo herd (range 1-27 ind.). In Bai-Hokou site, a single buffalo herd increased from 16 to 24 individuals during a three-year period (2001-2004). Finally in Lopé National Park (a mosaic of savanna and forest fragments), the mean group size for 18 herds monitored from 2002 to 2004 was 12±2 ind. (range of means 3–24). We analysed if herd size and herd stability are affected by clearing size, clearing type (e.g. marshy or sandy) and grass coverage across different sites and through time.
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Papers by Thomas Breuer