The Experts below are selected from a list of 9648 Experts worldwide ranked by ideXlab platform
Jennifer Vonk - One of the best experts on this subject based on the ideXlab platform.
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Behavioral and hormonal responses to the availability of forage material in Western lowland Gorillas (Gorilla Gorilla Gorilla)
Zoo Biology, 2017Co-Authors: Grace Fuller, Jennifer Vonk, Molly Mcguire, Melissa Thueme, Anna Murray, Stephanie AllardAbstract:We investigated how forage material affects indicators of welfare in three male Western lowland Gorillas (Gorilla Gorilla Gorilla) at the Detroit Zoo. In addition to their maintenance diet and enrichment foods, the Gorillas generally received forage material four times a week. From this baseline, we systematically manipulated how much forage material the group received on a weekly basis, with either daily or bi (twice)-weekly presentation of browse (mulberry, Morus sp.) or alfalfa hay. We collected behavioral data (60 hr per Gorilla) and measured fecal glucocorticoid metabolites (FGM). Mixed models indicated that the presence of forage material significantly increased time feeding (F2,351 = 9.58, p < 0.001), and decreased rates of noncontact aggression (F2,351 = 3.69, p = 0.03), and regurgitation and reingestion (F2,353 = 4.70, p = 0.01). Regurgitation and reingestion were never observed during the condition when forage material was provided daily. When forage material was provided, time spent feeding was similar across Gorillas, compared to a disproportionately greater amount of time spent feeding by the dominant individual when forage material was absent. Providing forage material in addition to the regular diet likely created more opportunities for equitable feeding for the subordinate Gorillas. FGM concentrations did not vary based on the presence or type of forage material available and, instead, likely reflected group social dynamics. In general, alfalfa and mulberry had similar impacts on behavior, indicating that alfalfa can be an adequate behavioral substitute during times when browse is less readily available for Gorillas housed in seasonally variable climates.
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Using an ambiguous cue paradigm to assess cognitive bias in Gorillas (Gorilla Gorilla Gorilla) during a forage manipulation.
Animal Behavior and Cognition, 2017Co-Authors: Molly C. Mcguire, Jennifer Vonk, Grace Fuller, Stephanie AllardAbstract:In nonhumans, ‘optimism’ is often defined as responding to an ambiguous item in the same manner as to items previously associated with reward (or lack of punishment), and “pessimism” is defined as responding to an ambiguous item in the same manner as to items previously associated with a lack of reward (or with punishment). We measured the degree of “optimism” and “pessimism” in three captive male western lowland Gorillas (Gorilla Gorilla Gorilla) during four consecutive two-week periods in which the amount of available forage material (mulberry, Moraceae or alfalfa, Medicago sativa) was manipulated. We assessed cognitive bias using an ambiguous cue paradigm for the first time. Pairs of two-dimensional shapes were presented on a touch-screen computer in a forced choice task in which one shape was always reinforced (P), one was never reinforced (N), and one was reinforced half the time, making it ambiguous (A). The Gorillas were presented with an equivalent number of PA and NA pairs prior to testing, which also included probe trials of ambiguous items paired with novel items. During the limited forage phase, the Gorillas, as a group, selected the ambiguous stimulus (indicating optimism) at a level greater than chance; tests for all other phases were non-significant. The Gorillas displayed individual differences in learning PA and NA trials and in their choice of ambiguous items on test trials. Idiosyncratic preferences for particular stimuli suggest that the ambiguous cue paradigm may not be ideal for assessing cognitive bias in nonhumans
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Orangutans (Pongo abelii) and a Gorilla (Gorilla Gorilla Gorilla) match features in familiar and unfamiliar individuals
Animal Cognition, 2014Co-Authors: Jennifer Vonk, Jennifer HamiltonAbstract:Great apes can perceive images as representative of corresponding real-life objects. Coupled with the potential advantages of identifying specific members of one’s species and mounting evidence for individual recognition in other non-humans, it seems likely that great apes would have the ability to identify conspecifics in photographs. The ability of four orangutans and a Gorilla to match images of individuals of their own and a closely related but unfamiliar species was examined here for the first time. First, the subjects matched photographs of familiar conspecifics taken at various time points in a delayed matching-to-sample procedure (Experiment 1). Second, they matched different photographs of unfamiliar individuals of a different species (Experiment 2) at above chance levels. These results suggest that the subjects matched photographs by matching physical features, not necessarily by recognizing the identity of the individuals depicted. However, they also quickly learned to select photographs of familiar individuals when these photographs were paired with photographs of unfamiliar individuals of their own species (Experiment 3), and three subjects showed transfer to novel images of familiar and unfamiliar individuals. Thus, the findings support the idea that subjects attended to physical features to identify individuals that they could categorize on the basis of familiarity.
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Quantity estimation and comparison in western lowland Gorillas (Gorilla Gorilla Gorilla)
Animal Cognition, 2013Co-Authors: Jennifer Vonk, Lauri Torgerson-white, Molly Mcguire, Melissa Thueme, Jennifer Thomas, Michael J. BeranAbstract:We investigated the quantity judgment abilities of two adult male western lowland Gorillas (Gorilla Gorilla Gorilla) by presenting discrimination tasks on a touch-screen computer. Both Gorillas chose the larger quantity of two arrays of dot stimuli. On some trials, the relative number of dots was congruent with the relative total area of the two arrays. On other trials, number of dots was incongruent with area. The Gorillas were first tested with static dots, then with dots that moved within the arrays, and finally on a task where they were required to discriminate numerically larger subsets within arrays of moving dots. Both Gorillas achieved above-chance performance on both congruent and incongruent trials with all tasks, indicating that they were able to use number as a cue even though ratio of number and area significantly controlled responding, suggesting that number was not the only relevant dimension that the Gorillas used. The pattern of performance was similar to that found previously with monkeys and chimpanzees but had not previously been demonstrated in Gorillas within a computerized test format, and with these kinds of visual stimuli.
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matching based on biological categories in orangutans pongo abelii and a Gorilla Gorilla Gorilla Gorilla
PeerJ, 2013Co-Authors: Jennifer VonkAbstract:Following a series of experiments in which six orangutans and one Gorilla discriminated photographs of different animal species in a two-choice touch screen procedure, Vonk & MacDonald (2002) and Vonk & MacDonald (2004) concluded that orangutans, but not the Gorilla, seemed to learn intermediate level category discriminations, such as primates versus non-primates, more rapidly than they learned concrete level discriminations, such as orangutans versus humans. In the current experiments, four of the same orangutans and the Gorilla were presented with delayed matching-to-sample tasks in which they were rewarded for matching photos of different members of the same primate species; golden lion tamarins, Japanese macaques, and proboscis monkeys, or family; gibbons, lemurs (Experiment 1), and subsequently for matching photos of different species within the following classes: birds, reptiles, insects, mammals, and fish (Experiment 2). Members of both Great Ape species were rapidly able to match the photos at levels above chance. Orangutans matched images from both category levels spontaneously whereas the Gorilla showed effects of learning to match intermediate level categories. The results show that biological knowledge is not necessary to form natural categories at both concrete and intermediate levels.
Linda Vigilant - One of the best experts on this subject based on the ideXlab platform.
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long term group membership and dynamics in a wild western lowland Gorilla population Gorilla Gorilla Gorilla inferred using non invasive genetics
American Journal of Primatology, 2018Co-Authors: Laura Hagemann, Martha M Robbins, Christophe Boesch, Mimi Arandjelovic, Tobias Deschner, Matthew Lewis, Graden Froese, Linda VigilantAbstract:The social organization of a group-living animal is defined by a balance between group dynamic events such as group formation, group dissolution, and dispersal events and group stability in membership and over time. Understanding these processes, which are relevant for questions ranging from disease transmission patterns to the evolution of polygyny, requires long-term monitoring of multiple social units over time. Because all great ape species are long-lived and elusive, the number of studies on these key aspects of social organization are limited, especially for western lowland Gorillas (Gorilla Gorilla Gorilla). In this study, we used non-invasive genetic samples collected within an approximately 100 km2 area of Loango National Park, Gabon to reconstruct group compositions and changes in composition over more than a decade. We identified 98 Gorillas and 11 mixed sex groups sampled during 2014-2017. Using published data from 85 individuals and 12 groups surveyed between 2005 and 2009 at the same locality, we tracked groups and individuals back in time. The identification of 11 silverbacks via parentage analyses and the genetic tracking of 39 individuals across studies allowed us to infer six group formations, five group dissolutions, and 40 dispersal events within 12 years. We also observed four groups persisting across the sampling periods with a maximum inferred existence of nearly 17 years and exhibiting variation in membership stability. Our results highlight the variation in composition and stability among groups of western lowland Gorillas and illustrate the power of non-invasive genetic sampling for long-term monitoring.
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detection dog efficacy for collecting faecal samples from the critically endangered cross river Gorilla Gorilla Gorilla diehli for genetic censusing
Royal Society Open Science, 2015Co-Authors: Mimi Arandjelovic, Richard A Bergl, Romanus Ikfuingei, Christopher Jameson, Megan Parker, Linda VigilantAbstract:Population estimates using genetic capture–recapture methods from non-invasively collected wildlife samples are more accurate and precise than those obtained from traditional methods when detection and resampling rates are high. Recently, detection dogs have been increasingly used to find elusive species and their by-products. Here we compared the effectiveness of dog- and human-directed searches for Cross River Gorilla (Gorilla Gorilla diehli) faeces at two sites. The critically endangered Cross River Gorilla inhabits a region of high biodiversity and endemism on the border between Nigeria and Cameroon. The rugged highland terrain and their cryptic behaviour make them difficult to study and a precise population size for the subspecies is still lacking. Dog-directed surveys located more fresh faeces with less bias than human-directed survey teams. This produced a more reliable population estimate, although of modest precision given the small scale of this pilot study. Unfortunately, the considerable costs associated with use of the United States-based detection dog teams make the use of these teams financially unfeasible for a larger, more comprehensive survey. To realize the full potential of dog-directed surveys and increase cost-effectiveness, we recommend basing dog-detection teams in the countries where they will operate and expanding the targets the dogs are trained to detect.
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genetic analysis reveals population structure and recent migration within the highly fragmented range of the cross river Gorilla Gorilla Gorilla diehli
Molecular Ecology, 2006Co-Authors: Richard A Bergl, Linda VigilantAbstract:Recently developed methods of individual-based analysis of genetic data allow an unprecedented opportunity to understand the relationships among fragmented populations. By defining population structure and identifying migrant individuals, such analyses can provide a framework to aid in evaluating the threats posed by inbreeding and reduced genetic variability as a consequence of limited gene flow among fragments. Here we investigate population structure in the critically endangered Cross River Gorilla ( Gorilla Gorilla diehli ) by applying a suite of individual-based analyses to data obtained from between onequarter and one-third of the estimated total population through the use of noninvasively collected DNA samples. The population structure inferred using data from 11 autosomal microsatellite loci was broadly consistent with geography and habitat fragmentation, but showed no simple isolation-by-distance effects. In contrast to previous field surveys, which suggested that all Gorilla localities were isolated from one another, we infer low levels of gene flow and identify migrants between habitat fragments as well as individuals of admixed ancestry, suggesting persistent recent reproductive contact between many of the localities. These results are encouraging for the conservation of the Cross River Gorilla population. Conservation efforts should strive to maintain connectivity between subpopulations that are still in migratory contact and attempt to restore connectivity where it has been lost.
Richard A Bergl - One of the best experts on this subject based on the ideXlab platform.
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detection dog efficacy for collecting faecal samples from the critically endangered cross river Gorilla Gorilla Gorilla diehli for genetic censusing
Royal Society Open Science, 2015Co-Authors: Mimi Arandjelovic, Richard A Bergl, Romanus Ikfuingei, Christopher Jameson, Megan Parker, Linda VigilantAbstract:Population estimates using genetic capture–recapture methods from non-invasively collected wildlife samples are more accurate and precise than those obtained from traditional methods when detection and resampling rates are high. Recently, detection dogs have been increasingly used to find elusive species and their by-products. Here we compared the effectiveness of dog- and human-directed searches for Cross River Gorilla (Gorilla Gorilla diehli) faeces at two sites. The critically endangered Cross River Gorilla inhabits a region of high biodiversity and endemism on the border between Nigeria and Cameroon. The rugged highland terrain and their cryptic behaviour make them difficult to study and a precise population size for the subspecies is still lacking. Dog-directed surveys located more fresh faeces with less bias than human-directed survey teams. This produced a more reliable population estimate, although of modest precision given the small scale of this pilot study. Unfortunately, the considerable costs associated with use of the United States-based detection dog teams make the use of these teams financially unfeasible for a larger, more comprehensive survey. To realize the full potential of dog-directed surveys and increase cost-effectiveness, we recommend basing dog-detection teams in the countries where they will operate and expanding the targets the dogs are trained to detect.
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Regional action plan for the conservation of the cross river Gorilla (Gorilla Gorilla diehli)
2007Co-Authors: John F. Oates, Richard A Bergl, Jacqueline Sunderland-groves, Andrew Dunn, Aaron Nicholas, Ebai Takang, Fidelis Omeni, Inaoyom Imong, Roger Fotso, Louis NkembiAbstract:The Cross River Gorilla (Gorilla Gorilla diehli) is recognized by IUCN as Critically Endangered, and is the most threatened taxon of ape in Africa. Work during the last two decades has revealed that fewer than 300 Cross River Gorillas may remain, spread across an area of about 12,000 km2. The outlook for these apes is far from hopeless, but a concerted and sustained effort will be required if their long-term survival is to be assured. Implementation of the recommendations in this plan would significantly increase the survival prospects for this species.
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genetic analysis reveals population structure and recent migration within the highly fragmented range of the cross river Gorilla Gorilla Gorilla diehli
Molecular Ecology, 2006Co-Authors: Richard A Bergl, Linda VigilantAbstract:Recently developed methods of individual-based analysis of genetic data allow an unprecedented opportunity to understand the relationships among fragmented populations. By defining population structure and identifying migrant individuals, such analyses can provide a framework to aid in evaluating the threats posed by inbreeding and reduced genetic variability as a consequence of limited gene flow among fragments. Here we investigate population structure in the critically endangered Cross River Gorilla ( Gorilla Gorilla diehli ) by applying a suite of individual-based analyses to data obtained from between onequarter and one-third of the estimated total population through the use of noninvasively collected DNA samples. The population structure inferred using data from 11 autosomal microsatellite loci was broadly consistent with geography and habitat fragmentation, but showed no simple isolation-by-distance effects. In contrast to previous field surveys, which suggested that all Gorilla localities were isolated from one another, we infer low levels of gene flow and identify migrants between habitat fragments as well as individuals of admixed ancestry, suggesting persistent recent reproductive contact between many of the localities. These results are encouraging for the conservation of the Cross River Gorilla population. Conservation efforts should strive to maintain connectivity between subpopulations that are still in migratory contact and attempt to restore connectivity where it has been lost.
Melissa J. Remis - One of the best experts on this subject based on the ideXlab platform.
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Impacts of dietary modifications on the behaviour of captive western lowland Gorillas (Gorilla Gorilla Gorilla).
Journal of Zoo and Aquarium Research, 2020Co-Authors: B. Katherine Smith, Melissa J. Remis, Ellen S. DierenfeldAbstract:Behavioural profiles of captive and wild Gorilla Gorilla Gorilla have been shown to differ greatly, with captive Gorillas moving and foraging much less than their wild counterparts and often experiencing high levels of obesity and cardiovascular disease. Captive Gorillas are typically fed an energy dense diet and housed in relatively small enclosures compared to wild Gorillas that forage for large quantities of fibrous fruits and foliage over expansive home ranges. These differences could be one of the leading factors in behavioural and health problems observed among captive Gorillas. This study examined behavioural profiles of captive Gorillas fed experimental diets more nutritionally similar in both nutrient content and volume to those seen in the wild, particularly with the addition of woody browse and tamarind seed. We predicted that when Gorillas ate the experimental diets, they would display behavioural patterns more similar to their wild counterparts. We found that feeding woody browses led to a reduction in coprophagy and regurgitation/reingestion (R/R) behaviours, but the addition of tamarind seed led to increased rates of coprophagy. These findings could be an important addition to management strategies in improving health and well-being among captive Gorillas.
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nutrition of the captive western lowland Gorilla Gorilla Gorilla Gorilla a dietary survey
Zoo Biology, 2014Co-Authors: B. Katherine Smith, Melissa J. Remis, Ellen S. DierenfeldAbstract:The successful management of captive animals requires attention to multiple interconnected factors. One critical aspect of the daily life of a captive animal is the recommended and/or provisioned diet. This study focuses on the diets of zoo-housed Gorillas. A national survey of diets among zoo-housed Gorillas was conducted to examine diets being offered to captive Gorillas in the United States and Canada. This survey serves as a follow-up to a 1995 dietary survey of zoo-housed Gorillas and goes further to quantify nutritional profiles at responding institutions. Results are encouraging, as zoos have made clear improvements in dietary nutrient profiles offered over the past 15 years. However, we suggest that zoological and sanctuary institutions follow Gorilla Species Survival Plan (SSP) recommendations and work to continuously improve diets provided, which could improve Gorillas' health and well-being.
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Nutritional Aspects of Western Lowland Gorilla (Gorilla Gorilla Gorilla) Diet During Seasons of Fruit Scarcity at Bai Hokou, Central African Republic
International Journal of Primatology, 2001Co-Authors: Melissa J. Remis, Ellen S. Dierenfeld, Christopher B. Mowry, R. W. CarrollAbstract:Traditionally, Gorillas were classified as folivores, yet 15 years of data on western lowland Gorillas (Gorilla Gorilla Gorilla) show their diet to contain large quantities of foliage and fruit, and to vary both seasonally and annually. The consumption of fruit by Gorillas at Bai Hokou, Central African Republic, is correlated with rainfall and ripe fruit availability (Remis, 1997a). We investigated the nutritional and chemical content of Gorilla foods consumed at Bai Hokou during two seasons of fruit scarcity as measured by phenological observations and compared our findings with the nutrient content of Gorilla foods at other African sites. We conclude that during lean times, Bai Hokou Gorillas consumed fruits with higher levels of fiber and secondary compounds than those of other populations of western lowland or mountain Gorillas. Conversely, leaves consumed by Bai Hokou Gorillas were relatively low in fiber and tannins. Bai Hokou Gorillas appeared to meet their nutritional needs by eating a combination of fruit and foliage. They ate fruits comparatively high in secondary compounds and fiber when necessary. While Gorillas are selective feeders, wherever and whenever preferred foods are scarce, their large body size and digestive anatomy enable them to consume and process a broader repertoire of foods than smaller bodied-apes.
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tree structure and sex differences in arboreality among western lowland Gorillas Gorilla Gorilla Gorilla at bai hokou central african republic
Primates, 1999Co-Authors: Melissa J. RemisAbstract:The aim of six months of research in 1995 on the Gorillas (Gorilla Gorilla Gorilla) at Bai Hokou, Central African Republic, was to study the effects of tree structure, relative numbers of arboreal feeding sites, and sex differences in body size on arboreal foraging. The analysis presented here also documents inter-annual variation in fruit availability and climbing by silverback Gorillas by comparing the 1995 results to those from earlier research, 1990–1992. This analysis suggests that female Gorillas maintain similar levels of arboreality in fruit-rich and fruit-poor seasons and years, but silverbacks may be more terrestrial when fruit is scarce or difficult to access. Trees of different shapes present different numbers of feeding sites to bigger males and smaller females. Male climbing is affected by the availability of fruit, and small trees with narrow crowns that lend easy access to fruit from the core. This study suggests that the energetics of vertical climbing and biomechanical constraints imposed by small branch feeding sites in the periphery of trees may constrain the arboreal behavior of male Gorillas. Fine-tuned comparisons of food availability, tree structure, and variation in social context of behavior across habitats, will assist efforts to understand differences in ecology among populations and species of African apes.
Jeffrey Rogers - One of the best experts on this subject based on the ideXlab platform.
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genomics Gorilla Gorilla Gorilla
Nature, 2012Co-Authors: Richard A Gibbs, Jeffrey RogersAbstract:The Gorilla genome reveals that genetic similarities among humans and the apes are more complex than expected, and allows a fresh assessment of the evolutionary mechanisms that led to the primate species seen today. See Article p.169
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genomics Gorilla Gorilla Gorilla
Nature, 2012Co-Authors: Richard A Gibbs, Jeffrey RogersAbstract:The Gorilla genome reveals that genetic similarities among humans and the apes are more complex than expected, and allows a fresh assessment of the evolutionary mechanisms that led to the primate species seen today. See Article p.169 The genome of the Gorilla has been sequenced, making it possible to compare the DNA of the four surviving hominid genera: human, chimpanzee, Gorilla and orang-utan. The data — mainly from a female western lowland Gorilla named Kamilah, but also from other Gorillas representing both the western lowland and eastern lowland sub-species — imply that in almost one-third of its genome, the Gorilla is closer to the human or chimpanzee than the human and chimp are to each other. Around 500 genes show accelerated evolution in Gorilla, human and chimpanzee lineages, and there is evidence for parallel acceleration, particularly in genes associated with hearing. On the basis of genetic and fossil evidence, the authors suggest that the human–chimpanzee and human–chimpanzee–Gorilla speciation events occurred at around 6 million and 10 million years ago respectively, whereas the two Gorilla species diverged around 1.75 million years ago.
