My research focuses on understanding how ecological networks are rewiring in the Anthropocene. Starting local at the Jasper Ridge Biological Preserve, I have been exploring noninvasive DNA metabarcoding methods to capture the biodiversity of the area, identifying key species, and construct an ecological network (food web) to reveal patterns of trophic interactions and community structure, allowing for predictive impacts of shifting community dynamics. In the Democratic Republic of Congo, I scaled this model to study how the hybridization of one of the largest ecosystem engineers, the Savanna - Forest elephant, is impacting the ecological network through assessing diet and habitat use, the health of individuals (microbiome, parasites & stress), and the ecological structure of Garamba National Park. Hybridization can result in novel ecological interactions, which in turn can trigger a cascade of processes with ecological and evolutionary outcomes. I am working in collaboration with African Parks, an NGO working in protected areas across the African continent, to address these questions. My long-term research goals focus on improving rewilding efforts and landscape-scale ecosystem services by applying conservation genomic techniques and network theory.

Before joining the Hadly Lab, I worked as a behavioral endocrinologist focusing on the reproductive success and management of the African elephant and the black rhino. I co-founded Wildtrax Explorations, a suite of programs offering educational and volunteer opportunities in Africa to help train the next generation of conservationists.

Stanford Advisors

All Publications

  • Molecular Ecological Network Analyses: An Effective Conservation Tool for the Assessment of Biodiversity, Trophic Interactions, and Community Structure FRONTIERS IN ECOLOGY AND EVOLUTION Meyer, J. M., Leempoel, K., Losapio, G., Hadly, E. A. 2020; 8
  • Temporal shifts in activity of prey following large predator reintroductions BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY Tambling, C. J., Minnie, L., Meyer, J., Freeman, E. W., Santymire, R. M., Adendorff, J., Kerley, G. H. 2015; 69 (7): 1153–61
  • Scraping behavior of black rhinoceros is related to age and fecal gonadal metabolite concentrations JOURNAL OF MAMMALOGY Freeman, E. W., Meyer, J. M., Adendorff, J., Schulte, B. A., Santymire, R. M. 2014; 95 (2): 340–48
  • Impacts of environmental pressures on the reproductive physiology of subpopulations of black rhinoceros (Diceros bicornis bicornis) in Addo Elephant National Park, South Africa CONSERVATION PHYSIOLOGY Freeman, E. W., Meyer, J. M., Bird, J., Adendorff, J., Schulte, B. A., Santymire, R. M. 2014; 2 (1): cot034


    Black rhinoceros are an icon for international conservation, yet little is known about their physiology due to their secretive nature. To overcome these challenges, non-invasive methods were used to monitor rhinoceros in two sections of Addo Elephant National Park, South Africa, namely Addo and Nyathi. These sections were separated by a public road, and the numbers of elephants, predators and tourists were higher in Addo. Faecal samples (n = 231) were collected (from July 2007 to November 2010) from known individuals and analysed for progestagen and androgen metabolite (FPM and FAM, respectively) concentrations. As biotic factors could impact reproduction, we predicted that demographics, FPM and FAM would vary between sections and with respect to season (calendar and wet/dry), climate and age of the rhinoceros. Mean FPM concentrations from pregnant females were seven times higher (P < 0.05) than samples from non-pregnant rhinoceros. Positive relationships were found between monthly temperatures and FPM from non-pregnant females (r (2) = 0.25, P = 0.03) and the percentage of calves born (r = 0.609, P = 0.04). Although FAM peaked in the spring, when the majority of calves (40%) were conceived, no seasonal patterns in male androgen concentrations were found with respect to month of conception and parturition. Females in Addo had a longer inter-calving interval and were less likely to be pregnant (P < 0.05) compared with those in Nyathi. The biotic stressors (e.g. predators and more competitors) within Addo section could be affecting the reproductive physiology of the rhinoceros negatively. Enhanced knowledge about how black rhinoceros populations respond to environmental stressors could guide management strategies for improving reproduction.

    View details for DOI 10.1093/conphys/cot034

    View details for Web of Science ID 000209703800022

    View details for PubMedID 27293618

    View details for PubMedCentralID PMC4732468

  • Ovarian cycle activity varies with respect to age and social status in free-ranging elephants in Addo Elephant National Park, South Africa CONSERVATION PHYSIOLOGY Freeman, E. W., Meyer, J. M., Putman, S. B., Schulte, B. A., Brown, J. L. 2013; 1 (1): cot025


    Free-ranging African elephants live in a fission-fusion society, at the centre of which is the matriarch. Matriarchs are generally older females that guide their families to resources and co-ordinate group defense. While much is known about elephant society, knowledge is generally lacking about how age affects the physiology of wild elephants. Investigation of the ovarian activity of free-ranging elephants could provide insight into the reproductive ageing process, with implications for population management. Faecal samples were collected from 46 individuals ranging in age from 14 to 60 years for a 2-year period, and progestagen metabolite analyses were used to examine relationships between social status, age, season, and ovarian activity in female elephants in Addo Elephant National Park, South Africa. Social status was the strongest predictor of faecal progestagen metabolite concentrations in non-pregnant elephants, with grand matriarchs (n = 6) having the lowest values compared with matriarchs (n = 21) and non-matriarch females (n = 19). Likewise, social status and age were the strongest predictors of faecal progestagen metabolite concentrations in pregnant elephants (n = 27). The number of years since a non-pregnant female gave birth to her last calf (post-partum duration) was longer for older females with a higher social status, as well as during the dry season. Our results indicate that social standing and age of elephants are related to reproductive function, and that older females exhibit reductions in ovarian capacity. These results expand our understanding of reproduction and fertility throughout an elephant's lifespan, and the factors that impact gonadal function in free-ranging females. Given that possible over-abundance of elephants in areas such as Addo Elephant National Park is fuelling the debate over how best to manage these populations, knowledge about the reproductive potential of high-ranking females can provide managers with biological data to identify the best candidates for controlling growth through translocation or contraception.

    View details for DOI 10.1093/conphys/cot025

    View details for Web of Science ID 000209703700012

    View details for PubMedID 27293609

    View details for PubMedCentralID PMC4806622

  • Characterizing Sleep Behavior of the Wild Black Rhinoceros (Diceros bicornis bicornis) SLEEP Santymire, R., Meyer, J., Freeman, E. W. 2012; 35 (11): 1569–74


    The objectives of this study were to characterize sleep patterns and determine factors, including sex, age, season, and environmental pressures, that influence sleep in the endangered black rhinoceros (rhino; Diceros bicornis bicornis).To noninvasively observe sleep behavior of wild rhinos, digital infrared cameras were erected on poles at two bedding sites from September 2009 to March 2010.The study site was located in South Africa's Addo Elephant National Park (AENP) in the Main Camp (Addo) and Nyathi sections.A total of 2,417 photos captured rhino sleep behavior on eight individual rhinos during 40 separate sleeping bouts (Addo, n = 15; Nyathi, n = 25).N/A.Results demonstrated that age and season did not affect rhino sleep behavior (P > 0.05); however, sex did influence the length of sleep bouts with males (n = 27; mean, 105.6 ± 11.3 min; range, 14.0-202.0 min) sleeping longer (F(1,48) = 6.93, P = 0.01) than females (n = 13; mean, 58.6 ± 10.4 min; range, 11.0-132.0 min). Park section did not influence the length of sleep episodes, but did affect (rw(40) = 0.88; P < 0.025) the time at which rhinos slept (Addo, 20:00-24:00; Nyathi, 20:00-04:00).This is the first study to characterize sleep behavior in wild black rhinos. This study resulted in a greater understanding of the biologic factors that affect sleep in wild rhinos and can provide information to assist their management and conservation.

    View details for DOI 10.5665/sleep.2212

    View details for Web of Science ID 000310578200018

    View details for PubMedID 23115406

    View details for PubMedCentralID PMC3466804

  • Using a simplified field progestagen method to assess ovarian activity in female African elephants BIOLOGICAL CONSERVATION Freeman, E. W., Meyer, J. M., Putman, S., Schulte, B. A., Brown, J. L. 2011; 144 (8): 2105–11
  • A simplified method for monitoring progestagens in African elephants under field conditions METHODS IN ECOLOGY AND EVOLUTION Freeman, E. W., Abbondanza, F., Meyer, J. M., Schulte, B. A., Brown, J. L. 2010; 1 (1): 86–91
  • Intrasexual chemical communication and social responses of captive female African elephants, Loxodonta africana ANIMAL BEHAVIOUR Meyer, J. M., Goodwin, T. E., Schulte, B. A. 2008; 76: 163–74
  • Comparisons of state and likelihood of performing chemosensory event behaviors in two populations of African elephants (Loxodonta africana) Schulte, B. A., Bagley, K. R., Groover, M., Loizi, H., Merte, C., Meyer, J. M., Napora, E., Stanley, L., Vyas, D. K., Wollett, K., Goodwin, T. E., Rasmussent, L. L., Hurst, J. L., Beynon, R. J., Roberts, S. C., Wyatt, T. D. SPRINGER. 2008: 81-+
  • Species and fetal gender effects on the endocrinology of pregnancy in elephants GENERAL AND COMPARATIVE ENDOCRINOLOGY Meyer, J. M., Walker, S. L., Freeman, E. W., Steinetz, B. G., Brown, J. L. 2004; 138 (3): 263–70


    Quantitative and temporal progestin profiles vary during gestation in the elephant, sometimes making it difficult to determine if a pregnancy is progressing normally. The aim of the present study was to determine if circulating progestin variability was related to species or fetal gender effects. A similar comparison also was conducted for secretory profiles of prolactin, relaxin, and cortisol. Overall mean progestin concentrations during gestation in Asian (n = 19) and African (n = 8) elephants were similar; however, the temporal profiles differed (P < 0.001). Concentrations were higher in African elephants during the first half of pregnancy, but then declined to levels below those observed in Asian elephants (P < 0.05). There also was a fetal gender effect in Asian, but not African elephants. Progestin concentrations were higher in Asian cows carrying male calves (n = 9) as compared to those carrying females (n = 10) (P < 0.001). Overall prolactin concentrations were higher in Asian than in African elephants between 8 and 15 months of gestation ( P< 0.001). There were no species differences in the secretory patterns of relaxin. Cortisol was relatively stable until the end of gestation when significant surges were observed, mainly between 8 and 11 days before parturition, and again on the day of birth. In sum, a comparison of progestin patterns between Asian and African elephants identified notable differences related to species and fetal gender. A role for cortisol in the initiation of parturition also was inferred from these data. From a practical standpoint, understanding the factors affecting gestational hormone characteristics and recognizing what the species differences are will help ensure that data used in diagnosing and monitoring elephant pregnancies are properly interpreted.

    View details for DOI 10.1016/j.ygcen.2004.06.010

    View details for Web of Science ID 000224088200009

    View details for PubMedID 15364209