Contact the Gorilla Species Survival Plan®


The Gorilla SSP® Research Advisors are Dr. Nancy Hawkes and Dr. Elena Less. Along with them, the SSP is supported by several other research scientists that help guide important scientific-based management principles.



Elena Less,
Cleveland Metroparks Zoo
(photo by Susan Griffith)




Learn more about the
Gorilla Health Project.




Kiki, G.g. gorilla
Zoo New England
(photo by Ellen Slotnick)




How does research inform
animal management?
Read about AZA's
standardized guidelines project.





Muke, G.g. gorilla, Utah's Hogle Zoo
(photo by Jameson Weston)





Bahati, G.g gorilla,
Lincoln Park Zoo
(© Lincoln Park Zoo/Steve Ross)

The science of gorillas

The care of animals as complex as gorillas requires a sophisticated management strategy. Luckily, gorillas are among the most well-studied animals in the world, and the SSP® benefits from the wide range of behavioral research being conducted on wild and captive apes. But even with this vast array of information, there remain many unanswered questions that can help address issues of animal husbandry and well-being, as well as the conservation of the species in the wild.

Gorilla Ethogram

An ethogram is a catalog of a species' behavioral repertoire. The Gorilla Behavior Advisory Group of the Gorilla SSP has compiled a compilation of over 45 gorilla ethograms.

To cite this document (APA format):

Ogden, J., Schildkraut, D., Baker, A., Beck, B.B., Bennett, C., duBois, T. et al. (1991). Compilation of gorilla ethograms. Atlanta, Georgia: Gorilla Species Survival Plan, Gorilla Behavior Advisory Group.

Current Research

AZA Gorilla Research Overview
Gorillas in captivity provide opportunities both to learn about the species and to use science to improve the well-being of its captive members.
See a list of publications generated from research on gorillas in AZA zoos, 2002-2006.
Studies listed here are taken from AZA's Annual Report on Conservation and Science.


Submitting a Research Proposal to the SSP

Submitting a Proposal:
Any researcher may submit a proposal to the Gorilla SSP for endorsement/approval for the following reasons:
To encourage AZA institutions housing gorillas to participate in their research project
2. To obtain a letter of endorsement/approval of their research project to aid in receiving funding.
3. To gain access to the gorilla studbook.

Proposal Review Process:
1. Proposals are sent to the Chair of the Gorilla Species Survival Plan (Kristen Lukas, Ph.D) or to either of the two research co-advisors (Nancy Hawkes, Ph.D. and Elena Less, Ph.D.).
2. The chair and research advisors will either request more information from the principal investigator of the project or if satisfied with the research proposal, post it to the Gorilla SSP Management Group and Advisors Listserv.
3. The management group then votes on the classification that they feel is appropriate for the proposal.

Definitions of Voting Classifications for Proposals Submitted to the Gorilla SSP Management Group:

  • ENDORSE: High priority, good science; we highly encourage zoos to do whatever they can to accommodate project; furthers goals of the Gorilla SSP
  • APPROVE: Moderate priority, good science; institutions should participate if they can
  • PASS: Low priority, questionable science; not relevant to Gorilla SSP goals


(view completed projects)

Endorsed Projects

Anti-Müllerian Hormone (AMH) as an Indicator of Ovarian Reserve in Gorillas (Gorilla gorilla) in captivity
Anneke Moresco (Denver Zoo), Francis Pau (Oregon National Primate Research Center), Betsy Stringer, DVM (Denver Zoo), Michael Stern (Denver Zoo), and BJ Schoeberl (Denver Zoo)
Gorillas are a carefully managed species in captivity, with specific breeding recommendations each year in order to maintain the genetic diversity. However, implementing such recommendations is a labor and cost intensive process that is not always successful. Part of the lack of success in older females may be due to a low ovarian reserve and declining fertility. In women, such ovarian reserve is measured by assaying serum levels of anti-Müllerian hormone (AMH), a hormone produced by granulosa cells, the cells that surround developing oocytes. The amount of AMH correlates with the number of oocytes that are left in a woman's ovaries. If such a tool were available for gorillas, it would provide very useful information for managers when making decisions about lifetime reproduction of specific individuals as well as evaluating the population as a whole. This study aims to validate the assay to measure AMH in gorillas and to evaluate its usefulness in predicting ovarian reserve in gorillas. We aim to do this by using archived serum samples of adult gorillas known to be cycling, menopausal gorillas known to have stopped cycling and peri-menopausal gorillas known to be cycling irregularly (a feature associated with impending menopause).

Perinatal Mortality in the Gorilla SSP
Pam Dennis (Cleveland Metroparks Zoo), Laura Scoda (The Ohio State University), and Elena Less (Cleveland Metroparks Zoo)
The recent deaths of several captive-born gorilla infants have prompted much discussion on possible causes of infant death in the captive western lowland gorilla (Gorilla gorilla gorilla) population. We wish to conduct a retrospective study examining one possible risk factor associated with pregnancy and neonatal death, i.e., decreased overall infant health due to maternal obesity. We request participation from all zoos that housed female gorillas that conceived or had breeding recommendations at any time during our proposed period of 1995 to present. We request copies of medical records (including any necropsy reports of dam or infant deaths), diet information, and ARKS specimen reports for each female for the time span of six months prior to conception through six months following the birth of the infant. We request the same information for each infant born (first six months post-parturition). In addition, we request a serum sample (if banked serum is available) from each female from within a one-year time period prior to conception. We will measure leptin, adiponectin, insulin, glucose, oxidized LDL, cholesterol, triglycerides, IGF-1, and prolactin. Elena Less uses these same parameters in her study on body condition of SSP gorillas. If an institution has already submitted samples that meet these criteria to Cleveland Metroparks Zoo for use in Elena's study, then we request permission to use the data from Elena's study rather than requesting an additional serum sample.

Understanding the Relationship between Reproductive Lifespan and Longevity in Zoo-housed Female Gorillas (Gorilla gorilla)
Sue Margulis (Canisius College) and Sylvia Atsalis (The San Diego Zoo's Institute for Conservation Research)
Between 2002 and 2009, Drs. Sue Margulis and Sylvia Atsalis conducted a study on reproductive aging in zoo-housed western lowland gorillas (Atsalis et al, 2004; Atsalis and Margulis 2006; Margulis et al., 2007; Atsalis and Margulis, 2008a; Atsalis and Margulis, 2008b). Results from the research demonstrated that gorillas may stop reproducing as early as 38 years of age, or may continue to cycle as late as 52 years of age. Since the completion of the study, many of the females from whom reproductive hormonal analyses were conducted and social and sexual behavioral data were collected have died. Thus, there is a unique opportunity to estimate the median length of post-reproductive lifespan in western lowland gorillas housed in zoos, where longevity conditions may be substantially enhanced compared to the wild. In order to do this, we need additional demographic and pathology records from the SSP and from participating zoos.
Specifically, we aim to address the following questions:
1. What is the post-reproductive lifespan of zoo-housed western lowland gorillas?
a. For those animals on which we have hormonal data, what was the duration of time between end of reproduction and end of life?
2. What is the lifetime reproductive success for zoo-housed western lowland gorillas?
a. Taking into consideration time during which females were contracepted, what is the fertility and fecundity of females in our study population?
3. Do females show signs of pathology similar to what is found in post-reproductive human females?
a. Ovarian pathology
b. Uterine pathology
c. Osteoporosis

Gorilla Personality and Subjective Well-Being Assessment
Alexander Weiss (University of Edinburgh)
This study's focus is on using gorilla personality as a measure of subjective well-being. The results of this study will be used to compare gorilla personality to that of other great ape species, including humans as well as analyze possible genetic, environmental or maternal influences on development of personality in gorillas.


Ongoing Long-Term Projects

San Diego Frozen Zoo
Ollie Ryder (San Diego Zoo- Conservation Research Center)
The Frozen Zoo®, begun in 1975, is a collection of bioresources including fibroblast cell lines, semen, oocytes, embryos, DNA, blood, and tissue representing about 1,000 mammalian, avian, reptilian and amphibian species/subspecies. Samples are obtained opportunistically from both captive and wild collections throughout the world. The scope of this project is large and covers a wide variety of species of interest in zoo/aquarium collections and affects many conservation interests.
Skin biopsies are processed for tissue culture, cryopreservation, and chromosome analyses to assess reproductive fitness for as many species as feasible. The documented impacts of mutations in managed populations, including dissimilar chromosomal complements or chromosomal heteromorphism, have compromised conservation breeding efforts for numerous species, including those in managed collections. Chromosomal and molecular studies, a crucial component of the Frozen Zoo® efforts, are conducted on an ongoing basis to address this issue, identifying hybrids, sterile individuals, and alerting researchers and curators to risk factors for population viability. Because case studies from the Frozen Zoo® represent the largest bank of comparative chromosomal data for nondomestic vertebrates in the world, this project covers species of interest in captive collections and impacts many conservation interests, including AZA population management initiatives. Information from these studies can also be used to benefit in situ populations. The genetic
analyses that assist in assessing reproductive fitness of animals in managed collections require a continuing effort to obtain samples and establish and freeze tissue cultures.

Evaluation of Risk Factors Associated with Cardiac Disease in Gorillas in AZA Institutions
Ilana Kutinsky (Beaumont Hospitals, MI), Suzan Murray (Smithsonian National Zoological Park), Tom Meehan (Chicago Zoological Society/ Brookfield Zoo), Hayley Murphy (Zoo New England), and Pam Dennis (Cleveland Metroparks Zoo)
Cardiac disease is a major cause of death for gorillas in AZA institutions. This project seeks to form a comprehensive database incorporating information from individual gorillas' medical, nutrition and husbandry records and to also address the diagnostic challenges associated with identifying heart disease in zoo gorillas.

Great Ape Neuroscience Project
Bill Hopkins (Emory University), Chet Sherwood (George Washington University), and Mary Ann Raghanti (Kent State University)
The current proposal aims to extend the previous Great Ape Aging Project (GAAP), headed by Dr. Joseph Erwin. The long-term goal of this project is to characterize the neurobiological organization of the brains of all great apes by collecting post-mortem specimens from individuals who had been under the care of North American Zoos. Pragmatically, the aim of the project is to obtain a sufficient number of brains from different age and sex classes of gorillas, chimpanzees, bonobos, and orangutans that will provide statistical power to make strong comparisons among species, and with human specimens in the context of brain aging. Furthermore, although the PIs of this project have their own scientific interest in these brains, the larger goal is to provide a database and specimen bank for making tissue samples and magnetic resonance images of the brains available to the scientific community.

Approved Projects

Retrospective Classification and Management Assessment of Canine Fractures in Captive Managed Populations of Great Apes
Jill Moyse (Houston Zoo), Dr. Kathryn Gamble (Lincoln Park Zoo), Dianne Mohr (Lincoln Park Zoo), George Prevolos (Lincoln Park Zoo)
At this time, it is unknown how many individual great apes in the captive population have broken, fractured and or cracked canine teeth. As several approaches for treatment or repair are possible, it is not known which of these injuries correlate best with the available management options. Long-term effects of no treatment are not predictable. The retrospective project will survey the captive managed great ape population to assess the occurrence of injuries and what treatment was provided to the animal. Zoo veterinarians will be surveyed to document any great apes in their collection that have any incidents of breakage, cracked or fracture of the canine teeth in the last 10 years. We anticipate majority to full participation from the SSP institutions that house great apes and will be able to compile a inventory of all animals that currently have canine fractures, breaks or cracks, the treatment they received and if any common risk factors are associated with the canine fractures. With this information, it is anticipated that prospective guidance of treatment options can be provided to institutions, veterinarians and the great ape SSP when animals present a fracture, break or cracked canine.

Birth Sex Ratio Data and its Importance for the Management of Western Lowland Gorillas In Zoological Settings
Kate Schein (University of Vienna)
Zoological institutions worldwide are faced with the difficulty of housing a surplus of male gorillas. With a total of 856 gorillas living in human care at this time (2010 Studbook) and an almost even split between sexes, a polygynous species, such as the gorilla, poses a managerial challenge. The appropriate management of these individuals however is essential to increasing sustainability in this critically endangered species. In 2000 Faust et al. used a visual modelling program to predict the fate of these charismatic apes living within zoological settings and calculated that within the next 25 years 50 male gorillas will need to be housed in bachelor troops across North America; 12 years later the number of males currently in bachelor troops is almost double that number and this trend is not confined to the US. This study aims to use data on over 1300 individuals born into human care since 1973 to identify possible factors influencing birth sex ratios in Western Lowland Gorillas. The identification of these factors will further the appropriate management of this species and help with breeding recommendations to enhance reproduction.

A Socio-Ecological Comparison of Chimpanzees, Gorillas and Bonobos: Conspecific Proximity, Communication, Feeding Competition, and Implications for Conservation
Scott Milne (Kennesaw State University)
For this project we hypothesize that bonobo and gorilla tolerance of close conspecific proximity during feeding will be higher than the tolerance of chimpanzees, but that gorillas will be more likely to employ gestures as a way to regulate group spacing than bonobos and chimpanzees due to the higher probability of having conspecifics closer by and the decreased need to vocalize to individuals at a distance. Similarly, we would expect bonobos and chimpanzees vocalizing more often than gorillas in the presence of different types of food, suggesting that the absence of gorillas in bonobo habitats may have allowed for them retain vocal communication as well as group cohesiveness, while the presence of gorillas in chimpanzee habitats may have allowed chimpanzees to retain vocal communication but lose relatively cohesive social groups while feeding and allowed gorillas to maintain close social groups with a decreased use of vocal communcation. We predict that we will see these differences emerge as a result of different distributions and qualities of food, a potential reflection of the similarities and differences seen in the wild that are thought to be driven by tendencies of chimpanzees to maintain preferences for high quality ripe fruits in times of scarcity and tendencies of gorillas and bonobos to increase reliance on THV (terrestrial herbaceous vegetation) in times of fruit scarcity. In order to investigate this, we will collect proximity and communicative data on chimpanzees, gorillas, and bonobos housed at the Association of Zoos and Aquariums (AZA) accredited zoos during different feeding scenarios. The following project is proposed to determine if ecological factors play a significant role in the socio-communicative behaviors of gorillas, chimpanzees and bonobos and to determine if similarities can be seen among gorillas and bonobos in an attempt to imply the influence that the presence or absence of species-species competition has on the evolution of social strategies in species that exploit similar resources.

Assessing Stress in Western Lowland Gorillas (Gorilla gorilla gorilla) in Human Care Using Allostatic Load
Ashley Edes (The Ohio State University), Barbara Wolfe, DVM, PhD (The Ohio State University, Columbus Zoo and Aquarium, The Wilds), Douglas Crews, PhD (The Ohio State University)
Lifetime stress substantially contributes to both humans and nonhuman primates (NHP)
developing many chronic degenerative diseases. The allostatic load (AL) model has been successfully used in humans to measure cumulative lifetime stress and predict future health outcomes. AL incorporates numerous biomarkers of stress to determine a composite AL score reflective of current and future health. NHP stress research is typically limited to assessing stress from singular events and using biomarkers in isolation. We propose AL could be used among NHP with the goal of improving health and increasing lifespan. We obtained data from 27 Western lowland gorillas currently or previously housed at the Columbus Zoo and Aquarium. Biomarker values came from medical records and assays of banked serum. Stress events were counted from keeper records. We identified stress events as agonistic interactions with wounding, zoo transfers, and anesthetic events. We developed four exploratory iterations of AL and propose Model 4 AL best predicts stress events and future outcomes in this sample. Using Model 4 AL, sex and historical stress events significantly associate with AL while age closely approaches statistical significance. Using cholesterol, triglycerides, and creatinine as general indicators of health, AL significantly associates with creatinine and triglycerides but not with cholesterol. There is no association between AL and age at death. This research develops a possible path for better understanding long-term consequences of stress on NHP health. Additionally, comparative research on AL in humans and NHP will enhance understanding of similarities, differences, and evolutionary divergences during hominoid evolution.

Gorilla pedigree analysis and heart disease
Euan Ashley (Stanford University), Linda Lowenstine (University of California- Davis), and Ollie Ryder (Center for Reproduction of Endangered Species, San Diego Zoo)
We are requesting permission from the TAG and SSP coordinators and studbook keeper to utilize information in the studbook to map gorilla pedigrees. To identify gorillas with heart disease we will use the SSP pathology databases compiled by Dr. Linda Lowenstine, School of Veterinary Medicine, University of California Davis (Ape TAG, gorilla, orangutan and bonobo SSP pathology advisor) and Dr. Tom Meehan, Brookfield Zoo (a Gorilla SSP veterinary advisor) to identify gorillas that have died of heart disease. Gorillas currently on treatment for heart disease (database compiled by gorilla SSP veterinary advisors Drs. Pam Dennis and Hayley Murphy) will also be included. The pedigree analysis will be conducted through Dr. Euan Ashley, Stanford University, Department of Medicine, and Stanford Center for Inherited Cardiovascular Disease.

Using Zoo Gorilla DNA to Create Ebola Virus Vaccines
Michael Jarvis (Oregon Health and Science University)
The long-term goal of this project is to develop a cytomegalovirus (CMV)-based vaccine to interfere with Ebola virus (EBOV) transmission from wild great ape populations to humans. EBOV is highly pathogenic in great apes, with a similar disease course as observed in humans. Substantial 'die-offs' of great apes from EBOV infection are consistently observed in the wild prior to human outbreaks 4-6. Consequently, EBOV is regarded as a major threat to the survival of great apes in the wild. Every mammalian species has it's own highly adapted version of CMV. The immediate aim of the study is to clone gorilla CMV (GoCMV) from Western Lowland gorillas for use as a genetic background for a vaccine. Gorilla fibroblast cells (obtained from Coriell Institute, NJ) will be used as a permissive cell type to isolate and culture GoCMV from gorilla tissue samples.

Kinship and Early History and their Impact on Affiliative Behaviour between Males in Captive Breeder and Bachelor Groups of Western Lowland Gorillas (Gorilla gorilla gorilla)
Kirsten Pullen (Paignton Zoo Environmental Park), Nancy Priston (Oxford Brookes University), and Katie Quantrell (Oxford Brookes University)
This study will investigate social interactions between male western lowland gorillas housed in breeder and bachelor groups to examine the effects that kinship, rearing history and early familiarity have on the affiliative behaviours expressed between individual dyads within these groups. Existing behavioural data (comprising both of affiliative interactions and proximity data) from males in five captive bachelor groups and six captive breeder groups from multiple institutions will be analysed against the data extracted from international studbooks using mixed model ANOVA's. The findings will help to further understanding of the factors influencing the social dynamics of these captive bachelor groups and hopefully aid management decisions of individuals in these groups to enable successful formation of long-term cohesive groups.

Maternal Investment in Captive Western Lowland Gorillas
Tara Stoinski (Zoo Atlanta), Bonnie Perdue (Zoo Atlanta), and Michael Hoff (Dalton College)
We will use the studbook to gather information on infant sex, interbirth intervals (IBI), maternal age, maternal parity, and infant mortality. IBI data will be compared to IBI data from wild western lowland and mountain gorillas to further test the hypothesis that ecological conditions are a primary determinant of maternal investment. Infant sex data will be used to determine if there is a bias in the sex-ratio at birth in captive western lowland gorillas. IBI data will also be used to determine if there is sex biased post-natal investment. Maternal age, parity, IBI, and infant mortality will be used to determine the pattern of investment and reproductive success across the lifespan. We will use the dataset to compare predictions of the various theories related to age, parity, and maternal investment. These data will provide the first quantitative description of western lowland gorilla interbirth intervals, sex ratios, and infant mortality.




Gorilla Population Histories
Linda Vigilant (Max Planck Institute for Evolutionary Anthropology) and Richard Bergl (North Carolina Zoological Park)
The specific aim of the project is to generate large amounts (> 50kb) of nuclear sequence data from western and eastern gorillas in order to improve the estimate of how long ago the two taxa diverged from one another, and estimate the amount, direction and duration of gene flow among these different populations. This project will also illuminate the extent to which the one-male mating system of gorillas has altered relative levels of genetic variation on the Y-chromosome, X-chromosome and autosomes relative to the levels found in chimpanzees and humans.

Thyroid Hormones, Thyroid Autoantibodies and Thyroid Histology in Gorillas with Non-Congenital Thyroid Dysfunction
Holly Aliesk (Cedars-Sinai Medical Center), Cynthia L. Courtney (Yerkes National Primate Research Center), Basil Rapoport (Cedars-Sinai Medical Center), and Sandra McLachlan (Cedars-Sinai Medical Center)

The great apes include, in addition to Homo, the genera Pongo (orangutans), Gorilla (gorillas), and Pan, the latter comprising two species, P. troglodytes (chimpanzees) and P. paniscus (bonobos). Adult-onset hypothyroidism was previously reported in 4 indiividual nonhuman great apes. However, there is scarce information on normal serum thyroid hormone levels and virtually no data for thyroid autoantibodies in these animals. Therefore, we examined thyroid hormone levels and TSH in all nonhuman great ape genera including adults, adolescents, and infants. Because hypothyroidism in humans is commonly the end result of thyroid autoimmunity, we also tested healthy and hypothyroid nonhuman great apes for antibodies to thryoglobulin (Tg), thryoid peroxidase (TPO), and the TSH receptor (TSHR). We established a thyroid hormone and TSH database for orangutans, gorillas, chimpanzees and bonobos (447 individuals). The most striking differences are the greatly reduced free-T4 and free-T3 levels in orangutans and gorillas vs chimpanzees and bonobos, and conversely, elevated TSH levles in gorillas vs Pan species. Antibodies to Tg and TPO were detected in only 2.6% of adult animals vs approximately 10% in humans. No animals with Tg, TPO, or TSHR thyroid antibodies exhibited thyroid dsyfunction. Conversely, hypothyroid nonhuman great apes lacked thyroid autoantibodies. Moreover, thyroid histology in necropsy tissues was similar in euthyroid and hypothyroid individuals, and lymphocytic infilitration was absent in 2 hypothyroid animals. In conclusion, free T4 and free T3 are lower in orangutans and gorillas vs chimpanzees and bonobos, the closest living human relatives. Moreover, thyroid autoantibodies are rare and hypothyroidism is unrelated to thyroid autoimmunity in nonhuman great apes.



An Analysis of Wounding Rates in Gorilla Groups: A Multi-Institutional Study
Austin Leeds (Cleveland Metroparks Zoo), Dawn Boyer (Saint Louis Zoo), Kristen Lukas (Cleveland Metroparks Zoo), and Steve Ross (Lincoln Park Zoo)
Although the research conducted by Kuhar et al. (2008) is beginning to dispel the myth that bachelor troops are more volatile than mixed-sex groups, a perception still exists among zoo managers that it is more dangerous for gorillas to be housed in all-male groups than mixed-sex groups. There is some evidence that injuries can be stressful and, at times, life-threatening for gorillas and veterinary decisions regarding wound management can have serious consequences for group stability or individual wellbeing. The Gorilla SSP Veterinary Advisor Team is currently developing wound management guidelines to assist zoos in making decisions when wounding events occur. To gather systematic data on wounding in gorillas, we would like to apply the same methods employed by Ross et al. (in press) in documenting and analyzing wounding rates in chimpanzees. Our goals are to describe the incidence of wounding in the North American Gorilla SSP population and test the following null hypotheses for gorillas:
1. Age: There is no difference in the wounding rate of groups containing males in the young SB range (14-18) and groups containing older BB males (11-14) or older SB male (18+).
2. Sex: There is no difference in the wounding rate of male vs. female gorillas.
3. Group: There is no difference in the wounding rate of all-male vs. mixed-sex gorilla groups.
4. Social unrest: There is no difference in the wounding rate of stable social groups versus those experiencing social introductions within one year of the data collection period.

Alcohol Metabolism, Primate Evolution and Paleogenetics
Matthew Carrigan (Foundation for Applied Molecular Evolution) and Steven Benner (Foundation for Applied Molecular Evolution)

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (AlDH) are two enzymes important in the detoxification of alcohols, including ethanol. We are a non-profit research foundation that has recently been funded by National Institute on Alcohol Abuse and Alcoholism (NIAAA) and the National Institute of Environmental Health Sciences (NIEHS), both part of the National Institutes of Health (NIH), to study the evolution of these proteins within the primate lineage. Ethanol was not always present in the environment, and it is therefore expected that evolutionary adaptation has occurred within these lineages since its introduction. We currently have the sequences of the ADH and AlDH genes for humans, Pan troglodytes, and Macaca mulatta (along with partial sequences for Pongo pygmaeus, Gorilla gorilla, and Papio hamadryas) through the NCBI genome database. We wish to expand upon the public database by sequencing the genes from as many other primates as possible, and to these ends, we seek the help of the larger zoo community. The exact species of the primates we use in our study is of less importance than obtaining genetic information from a wide diversity of primates, including representatives from each of the major evolutionary branches.

Admixture Between Historically Isolated Mitochondrial Lineages in Captive Western Gorillas:Recommendations for Future Management
Ivan Soto-Calderon (University of New Orleans, University of Antioquia), J. Larry Dew (Univesity of New Orleans), Richard Bergl (North Carolina Zoo), Michael Jensen-Seaman (Duquesne University), Nicola Anthony (University of New Orleans)
Although captive populations of western gorilla (Gorilla gorilla) have been maintained in the U.S. for over a century, little is known of the geographic origins and genetic composition of the current zoo population. Previous mitochondrial analyses have shown that natural populations of western gorillas exhibit substantial regional genetic structure. We combined pedigree records with mitochondrial sequence data from a subset of the U.S. captive gorillas to infer individual mitochondrial haplogroup affiliations, geographical origin of wild founders and assess the degree to which gorillas from historically isolated lineages have been inter-bred in captivity. The current U.S. captive population exhibits all major mitochondrial lineages within western lowland gorillas with levels of haplotype diversity comparable to that found in wild populations. However, the majority of crosses have occurred between individuals with different haplogroup affiliations. Although restricting crosses to individuals sharing the same haplogroup affiliation would preserve the phylogeographic structure present in the wild, without careful management such practice might also increase the risk of drift and inbreeding. Mitochondrial data are useful for tracking post-captive breeding history and document future admixture events. We recommend future releases to the wild take into account the mitochondrial affiliation and phylogeographic structure of wild populations.


Nutrition of the captive western lowland gorilla (Gorilla gorilla gorilla): a dietary survey.
Katie Smith, PhD (University of Houston), Melissa Remis, PhD (Purdue Univeristy), Ellen Dierenfeld, PhD (Animal Nutrition Consultant)
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.


Thyroid Hormones, Thyroid Autoantibodies and Thyroid Histology in Gorillas with Non-Congenital Thyroid Dysfunction
Sandra McLachlan (Cedars-Sinai Medical Center)
Adult-onset hypothyroidism was previously reported in 4 individual nonhuman great apes. However, there is scarce information on normal serum thyroid hormone levels and virtually no data for thyroid autoantibodies in these animals. Therefore, we examined thyroid hormone levels and TSH in all nonhuman great ape genera including adults, adolescents, and infants. Because hypothyroidism in humans is commonly the end result of thyroid autoimmunity, we also tested healthy and hypothyroid nonhuman great apes for antibodies to thyroglobulin (Tg), thyroid peroxidase (TPO), and the TSH receptor (TSHR). We established a thyroid hormone and TSH database in orangutans, gorillas, chimpanzees, and bonobos (447 individuals). The most striking differences are the greatly reduced free-T4 and free-T3 levels in orangutans and gorillas vs chimpanzees and bonobos, and conversely, elevated TSH levels in gorillas vs Pan species. Antibodies to Tg and TPO were detected in only 2.6% of adult animals vs approximately 10% in humans. No animals with Tg, TPO, or TSHR antibodies exhibited thyroid dysfunction. Conversely, hypothyroid nonhuman great apes lacked thyroid autoantibodies. Moreover, thyroid histology in necropsy tissues was similar in euthyroid and hypothyroid individuals, and lymphocytic infiltration was absent in 2 hypothyroid animals. In conclusion, free T4 and free T3 are lower in orangutans and gorillas vs chimpanzees and bonobos, the closest living human relatives. Moreover, thyroid autoantibodies are rare and hypothyroidism is unrelated to thyroid autoimmunity in nonhuman great apes.


Gorilla Contraception Survey
Sally Boutelle (AZA Wildlife Contraception Center)
The AZA Wildlife Contraception Center (WCC) is dedicated to bring contraceptive information for AZA animal populations, such as gorillas. As of April 2011, the Contraceptive Database holds over 26,500 records, 350 of which are for gorillas. With these data, analyses can be made on what products are effective, safe and reversible. The more information we gather, the more robust our data set. In 2010 it became apparent that more managers, veterinarians and keepers had questions specifically about brand name oral contraceptive pills and thus a full Gorilla Survey was created to address some of these inquiries. Birth control pills were the most commonly used form of contraception. Copulation is often observed while gorillas are contracepted and it is not common to see aggression increase after a female has been contracepted. Weight gain is common once a female gorilla is contracepted. For more information on this survey, please contact the AZA Wildlife Contraception Center.

Removal of Primate Chow from Gorilla Diets: The Impact on Behavior,
Adiposity and Health

Elena Hoellein Less (Cleveland Metroparks Zoo), Richard Bergl (North Carolina Zoo), Shana Lavin (Lincoln Park Zoo), Pam Dennis (Cleveland Metroparks Zoo), Sylvia Atsalis (CRES, The Zoological Society of San Diego), Kristen Lukas (Cleveland Metroparks Zoo), and Christopher Kuhar (Cleveland Metroparks Zoo)
The proposed study examines the influence of typical captive diets on gorilla behavior, obesity and overall health. In particular, we propose that for captive western lowland gorillas, replacing chow and fruit with larger quantities of plant material will reduce undesirable behaviors, increase activity and reduce adiposity. To test this hypothesis, we will: measure the amount of time engaged in physical activity (i.e. foraging, climbing, running, etc...) and the rate of feeding-related undesirable behaviors according to the two different diet types; determine concentrations of serum hormones related to adiposity and biological markers of inflammation; examine stool volatile fatty acids; and apply body measurement indices of physical condition in a sample of captive western lowland gorillas.
Update: The authors are preparing this study for publication, and more results will be available soon.

Adiposity in Captive Gorillas: Variance in BMI, Diet, and Activity Levels
Elena Hoellein Less (Cleveland Metroparks Zoo), Pam Dennis (Cleveland Metroparks Zoo), Kristen Lukas (Cleveland Metroparks Zoo), Christopher Kuhar (Cleveland Metroparks Zoo), and Mary Ann Raghanti (Kent State University)
The proposed study examines the influence of diet and activity level on gorilla adiposity. In particular, we propose that for captive western lowland gorillas, those gorillas that are fed a diet more similar to their wild counterparts and/or spend a large percentage of time active will have lower adiposity as reflected by body mass index and hormone levels. To test these hypotheses, we propose to survey the diet composition and feeding protocol along with activity levels in all gorillas housed in Association of Zoo and Aquarium institutions. In conjunction with assessing diet and activity we will measure (1) serum hormone concentrations related to adiposity, (2) biological markers of inflammation and (3) body measurement indices.

Update: The authors are preparing this study for publication, and more results will be available soon.

A Longitudinal Assessment of Gorilla Personality
Tara Stoinski (Zoo Atlanta), Bonnie Perdue (Zoo Atlanta), Chris Kuhar (Cleveland Metroparks Zoo), Kristen Lukas (Cleveland Metroparks Zoo), and Ken Gold (American Humane Association)
The Gorilla Behavior Index (GBI) is a measure of gorilla personality (Gold, 1993). Seven years later in 2000, Kuhar et al. (2006) replicated these dimensions in a sample of 119 male gorillas. A subset of 79 individuals was sampled at both time points, and we recently analyzed the stability of personality across time in those individuals (Perdue et al., 2009). Although this was the first analysis to examine stability in personality traits in apes, it had two limitations. First, it only looked for stability over a relatively short portion of a gorilla's lifespan (7 years). Thus, data are still needed to examine stability across the lifespan, and, in particular, from subadult to adulthood. Gathering personality data again now permits an analysis over a 16 year period (1993-2009), thus ensuring that all individuals assessed as infants or juveniles in 1993 are now fully adult. Second, the analysis only included males as the 2000 personality data were only collected on males. Since the original dataset included females, we would now like to also gather data on females to look for sex differences in personality stability.
Update: Data analysis is ongoing and results will be available soon.



Pan-African Sanctuary Alliance (PASA) Ape Modeling Project
Lisa Faust (Lincoln Park Zoo) and Ben Beck (Great Ape Trust)
This project's focus is on modeling the demography of representative great ape sanctuary populations using the captive population studbook to project the amount of space needed to house existing sanctuary specimens and accommodate new specimens being confiscated. The model should provide a valuable example of the time and resources required to maintain confiscated ape populations throughout their natural lifespan, giving sanctuaries a better understanding of the nature and extent of their commitment.
Update: Reports on gorilla dynamics were sent directly to sanctuary managers. Because more PASA sanctuaries contain chimpanzees, work on only chimpanzees was published:
Faust, LJ., Cress, D., Farmer, KH., Ross, SR., and Beck, BB. 2011. Predicting capacity demand on sanctuaries for African chimpanzees (Pan troglodytes). International Journal of Primatology: Published online 8 Mar 2011.


Cataloging Blood Types for SSP Populations of Great Apes
Kathryn Gamble (Lincoln Park Zoo) and Jill Moyse (Lincoln Park Zoo)
In humans and domestic mammals, blood typing plays an important role
in providing excellent medical care in critical care situations. It has been repeatedly demonstrated in the literature that humans and great apes have conserved identities within the standard blood typing categories of A-B-O and D(Rh factor). Development of simple table-top laboratories techniques to identify these most basic of blood groups in human patients may be applied to similar benefit in the great ape species.

Update: This study is complete and authors are currently preparing the study for publication. When available, we will post a summary of results.

Captive Great Apes and Their Interactions with Local Wildlife
Steve Ross (Lincoln Park Zoo) and Elizabeth Lonsdorf (Lincoln Park Zoo)
Although there are published reports of wild chimpanzees, bonobos, and orangutans hunting and consuming vertebrate prey, data pertaining to captive apes remain sparse. In this survey-based study, we evaluate the prevalence and nature of interactions between captive great apes and various indigenous wildlife species that range into their enclosures in North America. Our hypotheses were threefold: (a) facilities housing chimpanzees will report the most frequent and most aggressive interactions with local wildlife; (b) facilities housing orangutans and bonobos will report intermediate frequencies of these interactions with low levels of aggression and killing; and (c) facilities housing gorillas will report the lowest frequency of interactions and no reports of killing local wildlife. Chimpanzees and bonobos demonstrated the most aggressive behavior toward wildlife, which matched our predictions for chimpanzees, but not bonobos. This fits well with expectations for chimpanzees based on their natural history of hunting and consuming prey in wild settings, and also supports new field data on bonobos. Captive gorillas and orangutans were reported to be much less likely to chase, catch and kill wildlife than chimpanzees and bonobos. Gorillas were the least likely to engage in aggressive interactions with local wildlife, matching our predictions based on natural history. However unlike wild gorillas, captive gorillas were reported to kill (and in one case, eat) local wildlife. These results suggest that some behavioral patterns seen in captive groups of apes may be useful for modeling corresponding activities in the wild that may not be as easily observed and quantified. Furthermore, the data highlight the potential for disease transmission in some captive settings, and we outline the associated implications for ape health and safety.
Update: The authors wish to thank all zoos which participated in this study. The full results are published in:
Ross SR, Holmes AN, Lonsdorf EV. 2009. Interactions Between Zoo-Housed Great Apes and Local Wildlife. American Journal of Primatology 71(6):458-465.



Assessing the Prevalence and Characteristics of Hair Plucking Behavior in Captive Western Lowland Gorillas (Gorilla gorilla gorilla)
Elena Less (Cleveland Metroparks Zoo) and Kristen Lukas (Cleveland Metroparks Zoo)
This study's focus is on describing hair plucking behavior in captive gorillas, as well as evaluating risk factors that may predispose gorillas to exhibit this behavior. The results will be used to inform captive management decisions on ameliorating this behavior in the captive population.

Update: This survey is complete and data is currently being analyzed by the PI. The authors wish to thank the 38 zoos who participated.



Detection of SIVgor Infection in Captive Gorillas
Brandon Keele (University of Alabama) and Beatrice Hahn (University of Alabama)
There was recently reported in Nature evidence of a naturally occurring simian immunodeficiency virus infection in wild gorillas (G. g. gorilla) which was designated as SIVgor. The objective of this study is to determine if any captive gorillas are likewise infected. This study requests either plasma or fecal samples for each captive gorilla.

Update: No captive gorillas tested positive for SIVgor infection.



Assisted Reproduction Using Sex-Sorted Sperm: A Management Strategy for Captive Gorillas
Naida Loskutoff (Henry Doorly Zoo)

In light of the precarious state of gorillas in their natural habitats, the American Zoo and Aquarium Association (AZA) Gorilla Species Survival Plan (SSP) proposes the application of assisted reproductive technology as a means for allowing the genetic contributions of these animals to increase the likelihood of long-term genetic health and survival of the species. The aim of this research is to use the most recent advances in human assisted reproductive technologies as a model to develop methodology for producing female offspring from genetically underrepresented individuals in the Gorilla SSP. This study requests sperm samples from male gorillas and oocytes for female gorillas.
Update: We adapted flow cytometry technology for high-purity sorting of X chromosome-bearing spermatozoa in the western lowland gorilla (Gorilla gorilla gorilla). Our objectives were to develop methodologies for liquid storage of semen prior to sorting, sorting of liquid-stored and frozen-thawed spermatozoa, and assessment of sorting accuracy. In study 1, the in vitro sperm characteristics of gorilla ejaculates from one male were unchanged (P>0.05) after 8 hr of liquid storage at 15°C in a non-egg yolk diluent (HEPES-buffered modified Tyrode's medium). In study 2, we examined the efficacy of sorting fresh and frozen-thawed spermatozoa using human spermatozoa as a model for gorilla spermatozoa. Ejaculates from one male were split into fresh and frozen aliquots. X-enriched samples derived from both fresh and frozen-thawed human semen were of high purity, as determined by fluorescence in situ hybridization (FISH; 90.7%±2.3%, overall), and contained a high proportion of morphologically normal spermatozoa (86.0%±1.0%, overall). In study 3, we processed liquid-stored semen from two gorillas for sorting using a modification of methods for human spermatozoa. The sort rate for enrichment of X-bearing spermatozoa was 7.3±2.5 spermatozoa per second. The X-enriched samples were of high purity (single-sperm PCR: 83.7%) and normal morphology (79.0%±3.9%). In study 4 we examined frozen-thawed gorilla semen, and the sort rate (8.3±2.9 X-bearing sperm/sec), purity (89.7%), and normal morphology (81.4%±3.4%) were comparable to those of liquid-stored semen. Depending on the male and the type of sample used (fresh or frozen-thawed), 0.8-2.2% of gorilla spermatozoa in the processed ejaculate were present in the X-enriched sample. These results demonstrate that fresh or frozen-thawed gorilla spermatozoa can be flow cytometrically sorted into samples enriched for X-bearing spermatozoa.
Published in:
O'Brien, JK., Losuktoff, NM., et al. 2005. Flow cytometric sorting of fresh and frozen-thawed spermatozoa in the western lowland gorilla (Gorilla gorilla gorilla). American Journal of Primatology 66 (4): 297-315.

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