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Grimm V, Berger U, Bastiansen F, Eliassen S, Ginot V, Giske J, Goss-Custard J, Grand T, Heinz SK, Huse G, Huth A, Jepsen JU, Jørgensen C, Mooij WM, Müller B, Pe’er G, Piou C, Railsback SF, Robbins AM, Robbins MM, Rossmanith E, Rüger N, Strand E, Souissi S, Stillman RA, Vabø R, Visser U, DeAngelis DL. A standard protocol for describing individual-based and agent-based models. Ecol Modell 2006. [DOI: 10.1016/j.ecolmodel.2006.04.023] [Citation(s) in RCA: 1080] [Impact Index Per Article: 56.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 10/24/2022]
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19 |
1080 |
2
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Svirsky MA, Robbins AM, Kirk KI, Pisoni DB, Miyamoto RT. Language development in profoundly deaf children with cochlear implants. Psychol Sci 2000; 11:153-8. [PMID: 11273423 PMCID: PMC3429133 DOI: 10.1111/1467-9280.00231] [Citation(s) in RCA: 402] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/28/2022] Open
Abstract
Although cochlear implants improve the ability of profoundly deaf children to understand speech, critics claim that the published literature does not document even a single case of a child who has developed a linguistic system based on input from an implant. Thus, it is of clinical and scientific importance to determine whether cochlear implants facilitate the development of English language skills. The English language skills of prelingually deaf children with cochlear implants were measured before and after implantation. We found that the rate of language development after implantation exceeded that expected from unimplanted deaf children (p < .001) and was similar to that of children with normal hearing. Despite a large amount of individual variability, the best performers in the implanted group seem to be developing an oral linguistic system based largely on auditory input obtained from a cochlear implant.
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25 |
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Zimmerman-Phillips S, Robbins AM, Osberger MJ. Assessing cochlear implant benefit in very young children. THE ANNALS OF OTOLOGY, RHINOLOGY & LARYNGOLOGY. SUPPLEMENT 2000; 185:42-3. [PMID: 11140998 DOI: 10.1177/0003489400109s1217] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Academic Contribution Register] [Indexed: 11/17/2022]
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25 |
106 |
4
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Robbins MM, Gray M, Fawcett KA, Nutter FB, Uwingeli P, Mburanumwe I, Kagoda E, Basabose A, Stoinski TS, Cranfield MR, Byamukama J, Spelman LH, Robbins AM. Extreme conservation leads to recovery of the Virunga mountain gorillas. PLoS One 2011; 6:e19788. [PMID: 21687709 PMCID: PMC3110611 DOI: 10.1371/journal.pone.0019788] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 09/07/2010] [Accepted: 04/15/2011] [Indexed: 11/19/2022] Open
Abstract
As wildlife populations are declining, conservationists are under increasing pressure to measure the effectiveness of different management strategies. Conventional conservation measures such as law enforcement and community development projects are typically designed to minimize negative human influences upon a species and its ecosystem. In contrast, we define “extreme” conservation as efforts targeted to deliberately increase positive human influences, including veterinary care and close monitoring of individual animals. Here we compare the impact of both conservation approaches upon the population growth rate of the critically endangered Virunga mountain gorillas (Gorilla beringei beringei), which increased by 50% since their nadir in 1981, from approximately 250 to nearly 400 gorillas. Using demographic data from 1967–2008, we show an annual decline of 0.7%±0.059% for unhabituated gorillas that received intensive levels of conventional conservation approaches, versus an increase 4.1%±0.088% for habituated gorillas that also received extreme conservation measures. Each group of habituated gorillas is now continuously guarded by a separate team of field staff during daylight hours and receives veterinary treatment for snares, respiratory disease, and other life-threatening conditions. These results suggest that conventional conservation efforts prevented a severe decline of the overall population, but additional extreme measures were needed to achieve positive growth. Demographic stochasticity and socioecological factors had minimal impact on variability in the growth rates. Veterinary interventions could account for up to 40% of the difference in growth rates between habituated versus unhabituated gorillas, with the remaining difference likely arising from greater protection against poachers. Thus, by increasing protection and facilitating veterinary treatment, the daily monitoring of each habituated group contributed to most of the difference in growth rates. Our results argue for wider consideration of extreme measures and offer a startling view of the enormous resources that may be needed to conserve some endangered species.
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Research Support, Non-U.S. Gov't |
14 |
85 |
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Robbins AM, Robbins MM, Gerald-Steklis N, Steklis HD. Age-related patterns of reproductive success among female mountain gorillas. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2006; 131:511-21. [PMID: 16941601 DOI: 10.1002/ajpa.20474] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Academic Contribution Register] [Indexed: 11/10/2022]
Abstract
A key goal of life history theory is to explain the effects of age and parity on the reproductive success of iteroparous organisms. Age-related patterns may be influenced by changes in maternal experience or physical condition, and they may reflect maternal investment trade-offs between current versus future reproduction. This article examines the influences of age and parity upon the interbirth intervals (IBI), offspring survival, and birth rates of 66 female mountain gorillas in the Virunga Volcano region from 1967-2004. Fertility was relatively low for females below age 12; improved as they matured; and then declined as they aged further. Primiparous mothers had 50% higher offspring mortality and 20% longer IBI than second-time mothers, though only the difference with IBI was statistically significant. The length of subsequent IBI was positively correlated with birth order but not with the mother's age. Mountain gorillas showed no evidence of an extended postreproductive lifespan. Age-related patterns seem most likely to reflect changes in the physical condition of the mother, but more detailed studies are needed to quantify those physical differences, and to obtain behavioral evidence that would provide more direct measures of maternal investment and experience.
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77 |
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Genest JJ, Ordovas JM, McNamara JR, Robbins AM, Meade T, Cohn SD, Salem DN, Wilson PW, Masharani U, Frossard PM. DNA polymorphisms of the apolipoprotein B gene in patients with premature coronary artery disease. Atherosclerosis 1990; 82:7-17. [PMID: 1972879 DOI: 10.1016/0021-9150(90)90138-9] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Academic Contribution Register] [Indexed: 12/29/2022]
Abstract
Elevated plasma levels of low density cholesterol and their major apolipoprotein (apo B) are associated with an increased risk of coronary artery disease (CAD). We have examined allele frequencies of restriction fragment length polymorphisms (RFLP) of the apo B gene in 111 male Caucasians with premature CAD (mean age 49 +/- 7 years) and in 122 elderly Caucasian males (mean age, 73 +/- 5 years), free of clinical cardiovascular disease. The rare allele (R1) of the EcoR1 RFLP in exon 29, resulting in an amino acid change (Glu----Lys4154) was seen more frequently in CAD than in controls (0.270 vs 0.207, P less than 0.05). The R1 RFLP and the MspI insertion polymorphisms (MI) within the 3' hypervariable region (HVR) were observed together in 87% and are likely in linkage disequilibrium. The MI RFLP were slightly more frequent in CAD than control (0.239 vs. 0.211, P = 0.08). A second MspI RFLP in exon 26 results in an amino acid change (Arg----Glu3611); the rare allele M2 was seen more frequently in patients than in controls (0.150 vs. 0.057, P less than 0.005). No significant differences in allele frequencies were observed for the Xba1 RFLP in exon 26 (0.500 vs. 0.529, P = ns) or for the PvuII RFLP near the 5' end (P2) (0.105 vs. 0.088, P = ns). No statistically significant differences in lipid, lipoprotein cholesterol or apolipoproteins A-I and B were observed in patients or in controls. Two of the RFLPs examined (R1 and M2) result in changes in amino acid sequence and their allele frequencies are increased in CAD cases when compared with controls. Genetic variability within the apo B gene may thus contribute to cardiovascular risk. The physiological effects of individual mutations within apo B remain to be determined. It is unlikely, however that the single site polymorphisms examined in this study, will impart further information about CAD risk than conventional lipid parameters.
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35 |
75 |
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Miyamoto RT, Svirsky MA, Robbins AM. Enhancement of expressive language in prelingually deaf children with cochlear implants. Acta Otolaryngol 1997; 117:154-7. [PMID: 9105437 DOI: 10.3109/00016489709117758] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 02/04/2023]
Abstract
Expressive language skills were assessed in two groups of prelingually-deafened children using the Reynell Developmental Language Scales (RDLS). Results from a group of 89 unimplanted subjects provided cross-sectional data which suggested that profoundly deaf children without implants, on average, could only be expected to make 5 months of expressive language growth in one year. Twenty-three children who received cochlear implants made up the second group of subjects and were administered the RDLS at three intervals: preimplant, 6-, and 12-months postimplant. The scores obtained at the post-implant intervals were then compared to scores that would be predicted on the basis of maturation alone, without the implant (these predictions were formulated based on the data obtained from the unimplanted subjects). At the 12-month postimplant interval, the observed mean language score was significantly higher than the predicted score. Although the mean group data were extremely encouraging, wide inter- subject variability was observed. Although the implant subjects, as a group, were substantially delayed compared with their normal hearing peers, their rate of language growth was found to match that of hearing peers, following implantation. Thus, the gap between chronological age and language age, which normally widens over time in deaf children, remained constant. Preliminary analyses over the first 2.5 years post-implant are consistent with this trend. These results suggest that early implantation (before age 3) might be beneficial to profoundly deaf children because the language delays at the time of implantation would be much smaller.
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Miyamoto RT, Osberger MJ, Todd SL, Robbins AM, Stroer BS, Zimmerman-Phillips S, Carney AE. Variables affecting implant performance in children. Laryngoscope 1994; 104:1120-4. [PMID: 8072359 DOI: 10.1288/00005537-199409000-00012] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 01/28/2023]
Abstract
This study examined the variables that contribute to the large individual differences in the speech perception skills of children with the Nucleus multichannel cochlear implant. Sixty-one children were tested on four measures of speech perception: two tests of closed-set word recognition, one test of open-set recognition of phrases, and one open-set monosyllabic word test, scored on the basis of the percentage of phonemes as well as words identified correctly. The results of a series of multiple regression analyses revealed that the variables of processor type, duration of deafness, communication mode, age at onset of deafness, length of implant use, and age implanted accounted for roughly 35% of the variance on two tests of closed-set word recognition, and 40% of the variance on measures that assessed recognition of words or phonemes in an open set. Length of implant use accounted for the most variance on all of the speech perception measures.
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Abstract
English-language skills were evaluated in two groups of profoundly hearing-impaired children with the Reynell Developmental Language Scales, Revised. The first group consisted of 89 deaf children who had not received cochlear implants. The second group consisted of 23 children wearing Nucleus multichannel cochlear implants. The subjects without implants provided cross-sectional language data used to estimate the amount of language gains expected on the basis of maturation. The Reynell data from the group without implants were subjected to a regression by age. On the basis of this analysis, deaf children were predicted to make half or less of the language gains of their peers with normal hearing. Predicted language scores were then generated for the subjects with implants by using the children's preimplant Reynell Developmental Language Scale scores. The predicted scores were then compared with actual scores achieved by the subjects with implants 6 and 12 months after implantation. Twelve months after implantation, the subjects demonstrated gains in receptive and expressive language skills that exceeded by 7 months the predictions made on the basis of maturation alone. Moreover, the average language-development rate of the subjects with implants in the first year of device use was equivalent to that of children with normal hearing. These effects were observed for children with implants using both the oral and total-communication methods.
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Comparative Study |
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10
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Miyamoto RT, Kirk KI, Robbins AM, Todd S, Riley A. Speech perception and speech production skills of children with multichannel cochlear implants. Acta Otolaryngol 1996; 116:240-3. [PMID: 8725523 DOI: 10.3109/00016489609137832] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 02/01/2023]
Abstract
The acquisition of speech perception and speech production skills emerges over a protracted time course in congenitally deaf children with multichannel cochlear implants (CI). Only through comprehensive, longitudinal studies can the full impact of cochlear implantation be assessed. In this study, the performance of CI users was examined longitudinally on a battery of speech perception measures and compared with subjects with profound hearing loss who used conventional hearing aids (HA). The average performance of the multichannel cochlear implant users gradually increased over time and continued to improve even after 5 years of CI use. Speech intelligibility was assessed from recordings of the subjects' elicited speech and played to panels of listeners. Intelligibility was scored in terms of percentage of words correctly understood. The average scores for subjects who had used their CI for 4 years or more exceeded 40%.
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Comparative Study |
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Robbins AM, Gray M, Basabose A, Uwingeli P, Mburanumwe I, Kagoda E, Robbins MM. Impact of male infanticide on the social structure of mountain gorillas. PLoS One 2013; 8:e78256. [PMID: 24223143 PMCID: PMC3819382 DOI: 10.1371/journal.pone.0078256] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 03/02/2013] [Accepted: 09/11/2013] [Indexed: 12/02/2022] Open
Abstract
Infanticide can be a major influence upon the social structure of species in which females maintain long-term associations with males. Previous studies have suggested that female mountain gorillas benefit from residing in multimale groups because infanticide occurs when one-male groups disintegrate after the dominant male dies. Here we measure the impact of infanticide on the reproductive success of female mountain gorillas, and we examine whether their dispersal patterns reflect a strategy to avoid infanticide. Using more than 40 years of data from up to 70% of the entire population, we found that only 1.7% of the infants that were born in the study had died from infanticide during group disintegrations. The rarity of such infanticide mainly reflects a low mortality rate of dominant males in one-male groups, and it does not dispel previous observations that infanticide occurs during group disintegrations. After including infanticide from causes other than group disintegrations, infanticide victims represented up to 5.5% of the offspring born during the study, and they accounted for up to 21% of infant mortality. The overall rates of infanticide were 2-3 times higher in one-male groups than multimale groups, but those differences were not statistically significant. Infant mortality, the length of interbirth intervals, and the age of first reproduction were not significantly different between one-male versus multimale groups, so we found no significant fitness benefits for females to prefer multimale groups. In addition, we found limited evidence that female dispersal patterns reflect a preference for multimale groups. If the strength of selection is modest for females to avoid group disintegrations, than any preference for multimale groups may be slow to evolve. Alternatively, variability in male strength might give some one-male groups a lower infanticide risk than some multimale groups, which could explain why both types of groups remain common.
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research-article |
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Breuer T, Robbins AM, Boesch C, Robbins MM. Phenotypic correlates of male reproductive success in western gorillas. J Hum Evol 2012; 62:466-72. [PMID: 22386152 DOI: 10.1016/j.jhevol.2012.01.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 09/01/2011] [Revised: 01/09/2012] [Accepted: 01/12/2012] [Indexed: 11/25/2022]
Abstract
Sexual selection is thought to drive the evolution of sexually dimorphic traits that increase male reproductive success. Despite a large degree of sexual dimorphism among haplorhine primates, phenotypic traits that may influence the reproductive success of males are largely unstudied due to long life spans and the difficulties in quantifying such traits non-invasively. Here we employ digital photogrammetry of body length and crest size, as well as ranking of the gluteal muscle size, to test whether these sexually dimorphic traits are associated with long-term measures of male reproductive success in western gorillas. Among 19 adult male gorillas monitored for up to 12.5 years, we found that all three phenotypic traits were positively correlated with the average number of mates per male, but only crest size and gluteal muscle size were significantly correlated with offspring survival and the annual rate of siring offspring that survive to weaning age. We discuss why such sexually dimorphic traits might be under ongoing selection in gorillas and other species.
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Research Support, Non-U.S. Gov't |
13 |
44 |
13
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Robbins MM, Robbins AM. Variation in the social organization of gorillas: Life history and socioecological perspectives. Evol Anthropol 2018; 27:218-233. [PMID: 30325554 DOI: 10.1002/evan.21721] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 02/01/2018] [Revised: 07/18/2018] [Accepted: 08/06/2018] [Indexed: 01/29/2023]
Abstract
A focus of socioecological research is to understand how ecological, social, and life history factors influence the variability of social organization within and between species. The genus Gorilla exhibits variability in social organization with western gorilla groups being almost exclusively one-male, yet approximately 40% of mountain gorilla groups are multimale. We review five ultimate causes for the variability in social organization within and among gorilla populations: human disturbance, ecological constraints on group size, risk of infanticide, life history patterns, and population density. We find the most evidence for the ecological constraints and life history hypotheses, but an over-riding explanation remains elusive. The variability may hinge on variation in female dispersal patterns, as females seek a group of optimal size and with a good protector male. Our review illustrates the challenges of understanding why the social organization of closely related species may deviate from predictions based on socioecological and life history theory.
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Review |
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40 |
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Robbins MM, Robbins AM. Simulation of the population dynamics and social structure of the Virunga mountain gorillas. Am J Primatol 2004; 63:201-23. [PMID: 15300709 DOI: 10.1002/ajp.20052] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/06/2022]
Abstract
An agent-based model was developed to simulate the growth rate, age structure, and social system of the endangered mountain gorillas (Gorilla beringei beringei) in the Virunga Volcanoes region. The model was used to compare two types of data: 1) estimates of the overall population size, age structure, and social structure, as measured by six censuses of the entire region that were conducted in 1971-2000; and 2) information about birth rates, mortality rates, dispersal patterns, and other life history events, as measured from three to five habituated research groups since 1967. On the basis of the research-group data, the "base simulation" predicted a higher growth rate than that observed from the census data (3% vs. 1%). This was as expected, because the research groups have indeed grown faster than the overall population. Additional simulations suggested that the research groups primarily have a lower mortality rate, rather than higher birth rates, compared to the overall population. Predictions from the base simulation generally fell within the range of census values for the average group size, the percentage of multimale groups, and the distribution of females among groups. However, other discrepancies predicted from the research-group data were a higher percentage of adult males than observed, an overestimation of the number of multimale groups with more than two silverbacks, and an overestimated number of groups with only two or three members. Possible causes for such discrepancies include inaccuracies in the census techniques used, and/or limitations with the long-term demographic data set obtained from only a few research groups of a long-lived species. In particular, estimates of mortality and male dispersal obtained from the research groups may not be representative of the entire population. Our final simulation addressed these discrepancies, and provided a better basis for further studies on the complex relationships among individual life history events, group composition, population age structure, and growth rate patterns.
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Robbins MM, Robbins AM, Gerald-Steklis N, Steklis HD. Socioecological influences on the reproductive success of female mountain gorillas (Gorilla beringei beringei). Behav Ecol Sociobiol 2007. [DOI: 10.1007/s00265-006-0321-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 10/23/2022]
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18 |
37 |
16
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Osberger MJ, Todd SL, Berry SW, Robbins AM, Miyamoto RT. Effect of age at onset of deafness on children's speech perception abilities with a cochlear implant. Ann Otol Rhinol Laryngol 1991; 100:883-8. [PMID: 1746820 DOI: 10.1177/000348949110001104] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/28/2022]
Abstract
The speech perception abilities of 37 children with cochlear implants (single-channel or multichannel) were examined as a function of age at onset of deafness. There was no significant difference in the speech perception abilities of implanted children who were born deaf and those of implanted children who lost their hearing during the first 3 years of life. In contrast, the performance of children whose age at onset of deafness was 5 years or later was significantly better than that of the children with congenital or early-acquired deafness on tests of stress pattern categorization, closed-set word identification, open-set identification of common phrases, and lipreading enhancement.
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Robbins AM, Bollard PM, Green J. Language development in children implanted with the CLARION cochlear implant. THE ANNALS OF OTOLOGY, RHINOLOGY & LARYNGOLOGY. SUPPLEMENT 1999; 177:113-8. [PMID: 10214814 DOI: 10.1177/00034894991080s423] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Academic Contribution Register] [Indexed: 11/16/2022]
Abstract
This study examined the development of language skills in 23 prelingually, profoundly deaf children following implantation with the CLARION Multi-Strategy Cochlear Implant. Language skills were assessed with the Reynell Developmental Language Scales (RDLS) preoperatively with hearing aids, and compared to postoperative performance after 6 months of Clarion use. The RDLS was administered in each child's preferred mode of communication, either spoken English alone or simultaneous spoken and signed English. Significant improvements were observed in average age-equivalent scores over time, both for receptive and expressive skills, although the absolute language levels of the implanted children remained delayed relative to those of hearing peers of the same chronological age. The children's rate of language growth in the first 6 months of implant use also was calculated. The results from this analysis showed that the Clarion children, on average, progressed at a rate that exceeded that of normal-hearing children of the same language age. There was no significant difference between the language performance of children who used oral versus total communication.
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Clinical Trial |
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37 |
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Robbins AM, Stoinski T, Fawcett K, Robbins MM. Lifetime reproductive success of female mountain gorillas. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2011; 146:582-93. [PMID: 21989942 DOI: 10.1002/ajpa.21605] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Academic Contribution Register] [Received: 08/31/2010] [Accepted: 07/28/2011] [Indexed: 11/09/2022]
Abstract
Studies of lifetime reproductive success (LRS) are important for understanding population dynamics and life history strategies, yet relatively little information is available for long-lived species. This study provides a preliminary assessment of LRS among female mountain gorillas in the Virunga volcanoes region. Adult females produced an average of 3.6 ± 2.1 surviving offspring during their lifetime, which indicates a growing population that contrasts with most other great apes. The standardized variance in LRS (variance/mean(2) = 0.34) was lower than many other mammals and birds. When we excluded the most apparent source of environmental variability (poaching), the average LRS increased to 4.3 ± 1.8 and the standardized variance dropped in half. Adult lifespan was a greater source of variance in LRS than fertility or offspring survival. Females with higher LRS had significantly longer adult lifespans and higher dominance ranks. Results for LRS were similar to another standard fitness measurement, the individually estimated finite rate of increase (λ(ind) ), but λ(ind) showed diminishing benefits for greater longevity.
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Research Support, Non-U.S. Gov't |
14 |
34 |
19
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Robbins AM, Stoinski TS, Fawcett KA, Robbins MM. Socioecological influences on the dispersal of female mountain gorillas—evidence of a second folivore paradox. Behav Ecol Sociobiol 2008. [DOI: 10.1007/s00265-008-0679-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 10/21/2022]
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22 |
20
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Grueter CC, Robbins AM, Abavandimwe D, Vecellio V, Ndagijimana F, Ortmann S, Stoinski TS, Robbins MM. Causes, mechanisms, and consequences of contest competition among female mountain gorillas in Rwanda. Behav Ecol 2015. [DOI: 10.1093/beheco/arv212] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 11/12/2022] Open
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10 |
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21
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Breuer T, Robbins AM, Olejniczak C, Parnell RJ, Stokes EJ, Robbins MM. Variance in the male reproductive success of western gorillas: acquiring females is just the beginning. Behav Ecol Sociobiol 2009. [DOI: 10.1007/s00265-009-0867-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 10/20/2022]
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16 |
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22
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Miyamoto RT, Osberger MJ, Robbins AM, Myres WA, Kessler K, Pope ML. Comparison of speech perception abilities in deaf children with hearing aids or cochlear implants. Otolaryngol Head Neck Surg 1991; 104:42-6. [PMID: 1900628 DOI: 10.1177/019459989110400109] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Indexed: 12/29/2022]
Abstract
The speech perception abilities of deaf children with a single- or multi-channel cochlear implant are compared with those of deaf children who derive substantial benefit from conventional hearing aids. The children with hearing aids have unaided pure-tone thresholds ranging from 90- to 110-dB HL through at least 2000 Hz, and aided thresholds of 30- to 60-dB HL. The group data show that the speech perception scores of the subjects with hearing aids were significantly higher than those of the subjects with implants on a range of speech perception measures. Although a few subjects with implants achieved scores as high as those who used hearing aids, the majority did not. Even though the children with implants receive substantial benefit from their devices, they continue to have limited auditory perception abilities relative to their peers who derive benefit from conventional hearing aids. The data highlight the importance of establishing hearing aid benefit in potential candidates for implant.
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Comparative Study |
34 |
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23
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Grueter CC, Robbins AM, Abavandimwe D, Vecellio V, Ndagijimana F, Stoinski TS, Robbins MM. Quadratic relationships between group size and foraging efficiency in a herbivorous primate. Sci Rep 2018; 8:16718. [PMID: 30425319 PMCID: PMC6233200 DOI: 10.1038/s41598-018-35255-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 05/30/2018] [Accepted: 10/18/2018] [Indexed: 11/23/2022] Open
Abstract
The effect of feeding competition on foraging efficiency is an important link between ecological factors and the social organization of gregarious species. We examined the effects of group size on daily travel distances, activity budgets, and energy intake of mountain gorillas in Rwanda. We measured daily travel distances of five groups, activity budgets of 79 gorillas in nine groups, and energy intake data for 23 adult females in three groups over a 16-month period. Travel distances and the proportion of time spent traveling increased with size for most groups, which would be expected if their foraging efficiency is limited by intragroup feeding competition. However, travel distances and times decreased for the largest group, which also had higher energy intake rates than intermediate sized groups. The improved foraging efficiency of the largest group may be explained by advantages in intergroup contest competition. The largest group had much lower home range overlap than the other study groups which may be due to groups avoiding one another as a result of male mating competition. Collectively, our results indicate that intermediate sized groups had the lowest foraging efficiency and provide a new twist on the growing evidence of non-linear relationships between group size and foraging efficiency in primates.
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Breuer T, Robbins AM, Robbins MM. Sexual coercion and courtship by male western gorillas. Primates 2016; 57:29-38. [PMID: 26483073 DOI: 10.1007/s10329-015-0496-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Academic Contribution Register] [Received: 07/02/2015] [Accepted: 10/06/2015] [Indexed: 11/29/2022]
Abstract
Sexual coercion and courtship are possible explanations for why male primates may direct agonistic behavior towards females. If so, then in species where females exhibit mate choice by transferring between males: (a) females who are not lactating (potential migrants) should receive more agonistic behavior than other females, (b) males should exhibit more agonistic behavior towards females during intergroup encounters than when no rival males are nearby, and (c) males should show more herding behavior when their group contains potential migrant females. We tested those hypotheses in a population of approximately 150 western gorillas at Mbeli Bai, northern Congo. We also tested whether difference in male phenotypic traits influenced their rates of agonistic behavior towards females. Of the 332 observed cases of male agonistic behavior towards females, 29% represented feeding competition, 7 % involved interventions in conflicts between females, and the remaining 64 % were considered potential evidence of sexual coercion and/or courtship. After excluding the cases of feeding competition and intervention, a multivariate analysis indicated that potential migrant females received agonistic behavior at a statistically significantly higher rate than other adult females. Females also received agonistic behavior at a significantly higher rate during intergroup encounters than at other times. Herding occurred during 22% of the 292 dyadic interunit encounters, and was significantly more likely to occur when the group contained a potential migrant female, but was not influenced by the number of adult females or the type of group encountered. Males with shorter body lengths had significantly higher rates of aggression, but phenotypic traits were not significantly correlated with herding. Collectively, our results are consistent with sexual coercion and/or courtship as an explanation for male-to-female agonistic behavior, but we are unable to distinguish between those two male mating strategies. Both types of behavior are likely due to a combination of perceived risks of female transfer and opportunity to advertise protector ability.
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