Red wolves lying in the dirt in exhibit

Alexander Center for Applied Population Biology

Wild Puerto Rican parrot resting on a branch

The Alexander Center for Applied Population Biology studies the demographic, genetic, and ecological factors that make animal populations vulnerable to extinction, along with which management strategies will allow them to thrive. Center scientists use their analytical skills in partnership with field conservationists to help with the work of saving species. As biodiversity continues to decline worldwide, these efforts are critical for effective and impactful conservation.

The Alexander Center was established in 2005 through the generosity of Emily and John Alexander.

Areas of Focus

Conducting Population Viability Analyses

As populations become smaller and subject to threats like habitat loss, genetic isolation, climate change, and human pressures, they are more at risk of decline and extinction. Scientists at the Alexander Center conduct Population Viability Analyses using computer models that project what animal populations will look like in the future given their current known biology and the threats they face.

In collaboration with conservation managers, they use these models to identify the best management strategies to reduce extinction risk and maintain viable populations for the long-term. This results in actionable management advice for species in zoos and the wild, from eastern massasauga rattlesnakes to African elephants.

Advising Reintroduction Programs

Wildlife reintroductions—the release of individuals, often raised in zoos or breeding centers, to bolster an existing population or create a new population in the wild—are becoming increasingly common. The Alexander Center works with reintroduction programs to provide the population advising needed to maintain a species’ health and maximize the chances of species recovery.

This includes support for data management to best inform sound genetic and demographic management decisions about breeding and release strategies. Alexander Center scientists advise a wide range of programs, including those focusing on the greater sage grouse in Canada, Puerto Rican parrots, and red wolves in the U.S. This is done in partnership with local nongovernmental organizations (NGOs) as well as government agencies such as the U.S. Fish and Wildlife Service.

Science Advising to Support Field Conservationists

Alexander Center scientists use their statistical and modeling skills to support and facilitate the conservation work of partners. They advise partners on data management, develop training and tools to enhance reporting and evaluation, and collaborate on the analysis of long-term datasets.

Most analyses conducted by the Alexander Center are designed to clarify a species’ or population’s demography, genetics, ecological relationships, conservation status, and the influence of any threats or management actions on its ecology. Alexander Center scientists help partners develop reports and publications to share their findings with government and conservation agencies, the public, and the greater scientific community.

Research and Tool Development to Support Zoo Populations

Over the past several decades, the Alexander Center has developed multiple software packages to support zoo populations and their management (PopLink, ZooRisk, PMCTrack). Center staff continue to improve these software tools and harness them to conduct comparative analyses that can improve the management of zoo and aquarium populations.

Partner With Us

The Alexander Center is open to collaborations with conservation partners, especially those working in reintroduction and recovery programs or in other species-focused conservation projects. To talk more about collaboration opportunities, please contact us at

Freely Available Software

The Alexander Center creates tools to support the efforts of conservation managers and the wider scientific community. These tools help apply science-based approaches to the conservation and management of both zoo and wild populations.


PMCTrack is a website that evaluates outcomes of breeding and transfer recommendations for Species Survival Plans®, improving population planning in zoos and aquariums.

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PopLink is a computer program that helps scientists and managers track data on individual animals over their lifetime—and leverages that data to benefit their management.

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ZooRisk is a computer program that provides a quantitative assessment of a population’s risk of extinction due to the demographic, genetic, and management processes that affect it.

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  • Faust, L.J. 2023. Puerto Rican Parrot (Amazona vittata) Population Viability Analysis Report. Lincoln Park Zoo, Chicago.
  • Miller, P.S., A. Parsons, L. Faust, and A. Franklin. 2023. Population viability analysis of the red wolf (Canis rufus): Integrated management of in situ and ex situ populations in support of species recovery in a mixed canid landscape. Final report – 22 August 2023. Apple Valley, MN: IUCN SSC Conservation Planning Specialist Group.
  • Gray, S.M., Parsons, A.W., Andrews, J.E., Schad Eebes, K., Faust, L.J., & Che-Castaldo, J. (2023). Institutional networks in cooperative population management: Exploring patterns in transfer fulfillment. Zoo Biology, Early View.
  • Gray, S.M., Faust, L.J., Senner, P., Eebes, K.S., & Che-Castaldo, J.P. (2022). Influence of institutional attributes on fulfillment of transfer and breeding recommendations in zoos and aquariums. Zoo Biology, 42(1), 142–149.
  • Hernández-Yáñez, H., Kim, S.Y., Che-Castaldo, J.P. (2022). Demographic and life history traits explain patterns in species vulnerability to extinction. PLoS ONE, 17(2), e0263504.
  • Che-Castaldo, J., Gray, S.M., Rodriguez-Clark, K.M., Eebes, K.S., Faust, L.J. (2021). Expected demographic and genetic declines not found in most zoo and aquarium populations. Frontiers in Ecology and Environment. 19(8), 435–442.
  • Che-Castaldo, J.P., Havercamp, K., Watanuki, K., Matsuzawa, T., Hirata, S. & Ross, S.R.. (2021). Comparative survival analyses among captive chimpanzees (Pan troglodytes) in America and Japan. PeerJ, 9, e11913.
  • Che-Castaldo, J.P., Cousin, R., Daryanto, S., Deng, G., Feng, M.-L.E., Gupta, R.K., Hong … & S. Matteson (2021) Critical Risk Indicators (CRIs) for the electric power grid: A survey and discussion of interconnected effects. Environment Systems and Decisions, 41, 594–615.
  • Compagnoni, A., Levin, S., Childs, D., Harpole, S., Paniw, M., Römer, G., … & Knight, T. (2021). Herbaceous perennial plants with short generation time have stronger responses to climate anomalies than those with longer generation time. Nature Communications. 12(1), 1824.
  • Faust, L., Kuykendall, N., Spencer, R., and Oliver, J. (2021). PMCTrack: A website for monitoring breeding and transfer recommendations for AZA zoo populations. Version 2.0. Lincoln Park Zoo, Chicago, Illinois.
  • Gray, S.M., Faust, L.J., Kuykendall, N.A., Bladow, R.A., Schad Eebes, K., & Che-Castaldo, J.P. (2021). Reasons for unfulfilled breeding and transfer recommendations in zoos and aquariums. Zoo Biology, 41(2), 143–156.
  • Jenouvrier, S., Che-Castaldo, J.P., Wolf, S., Holland, M., Labrousse, S. , LaRue, M., … & Trathan, P.N. (2021). The call of the emperor penguin: Legal responses to species threatened by climate change. Global Change Biology, 27(20), 5008–5029.
  • Paniw, M., James, T.D., Archer, C.R., Römer, G., Levin, S., A. Compagnoni, … & Salguero-Gómez, R. (2021). The myriad of complex demographic responses of terrestrial mammals to climate change and gaps of knowledge: A global analysis. Journal of Animal Ecology, 90(6), 1398–1407.
  • Che-Castaldo, J., Jones, O.R., Kendall, B.E., Burns, J.H., Childs, D.Z., Ezard, T.H.G., … & Salguero-Gómez, R. (2020). Comments to “Persistent problems in the construction of matrix population models.” Ecological Modelling, 416, 108913.
  • Powell, D.M., Dorsey, C.L., & Faust, L.J. (2019). Advancing the science behind animal program sustainability: An overview of the special issue. Zoo Biology, 38(1), 5–11.
  • Che‐Castaldo, J., Johnson, B., Magrisso, N., Mechak, L., Melton, K., Mucha, K., … & Faust, L. (2019). Patterns in the long-term viability of North American zoo populations. Zoo Biology, 38(1), 78–94.
  • Che-Castaldo, J.P., Byrne, A., Perišin, K., & Faust, L.J. (2019). Sex-specific median life expectancies from ex situ populations for 330 animal species. Scientific Data, 6, 190019.
  • Faust, L.J., Long, S.T., Perišin, K., & Simonis, J.L. (2019). Uncovering challenges to sustainability of AZA Animal Programs by evaluating the outcomes of breeding and transfer recommendations with PMCTrack. Zoo Biology, (38)1, 24–35.
  • Faust, L.J. (2019). What keeps me up at night as a zoo-based conservation biologist (2019). The Bulletin of the Ecological Society of America, 100(1), e01490.
  • Hileman, E.T., King, R.B., & Faust L.J. (2018). Eastern massasauga demography and extinction risk under prescribed‐fire scenarios. The Journal of Wildlife Management, 82(5).
  • Che-Castaldo, J.P., Grow, S.\A., & Faust, L.J. (2018). Evaluating the Contribution of North American Zoos and Aquariums to Endangered Species Recovery. Scientific Reports, 8(1), 9789.
  • Bradke, D.R., Hileman, E.T., Bartman, J.F., Faust, L.J., King, R. B., Kudla, N., & Moore, J.A. (2018). Implications of small population size in a threatened pitviper species. Journal of Herpetology, 52(4), 387–398.
  • Hileman, E. T., King, R. B., Adamski, J. M., Anton, T. G., Bailey, R. L., Baker, S. J., … Yagi, A. (2017). Climatic and geographic predictors of life history variation in Eastern Massasauga (Sistrurus catenatus): A range-wide synthesis. PLoS ONE, 12(2), e0172011.
  • Meyerson, R., Moore, D., Long, S., and Che-Castaldo, J. (2017). Welfare of captive polar bears and their value to in situ conservation efforts. In A. Butterworth, Ed., Marine Mammal Welfare: Human Induced Change in the Marine Environment and its Impacts on Marine Mammal Welfare (pp. 489–501). Springer.
  • Salguero-Gómez, R., Jones, O.R., Archer, C.R., Bein, C., de Buhr, H. Farack, C., … & Vaupel, J.W. (2016). COMADRE: A global database of animal demography. Journal of Animal Ecology, 85(2), 371–384.
  • Faust, L.J., Simonis, J.S., Harrison, R., Waddell, W., & Long, S. (2016). Red Wolf (Canis rufus) Population Viability Analysis – Report to U.S. Fish and Wildlife Service. Lincoln Park Zoo, Chicago.
  • Lankester, F.J., Wouters, P.A.W.M., Czupryna, A., Palmer, G. H., Mzimbiri, I., Cleaveland, S., … & Sonnemans, D.G.P. (2016). Thermotolerance of an inactivated rabies vaccine for dogs. Vaccine, 34(46), 5504–5511.
  • Allender, M.C., Junge, R.E., Baker-Wylie, S., Hileman, E.T.,Faust, L.J., Cray, C. (2015). Plasma electrophoretic profiles in the Eastern Massasauga (sistrurus catenatus) and influences of age, sex, year, location, and snake fungal disease. Journal of Zoo and Wildlife Medicine, 46(4), 767–773.
  • Salguero-Gómez, R., Jones, O.R., Archer, C.R., Buckley, Y.M., Che-Castaldo, J., Caswell, H. … & Vaupel, J.W. (2015). The COMPADRE plant matrix database: An open online repository for plant demography. Journal of Ecology 103(1), 202–218.
  • Earnhardt, J., Vélez-Valentín, J., Valentin, R., Long, S., Lynch, C., & Schowe, K. (2014). The Puerto Rican parrot reintroduction program: sustainable management of the aviary population. Zoo Biology 33(2), 89–98.
  • Faust, L.J., Bier, L., Schowe, K., & Gazlay, T. (2012). PopLink 2.3 User’s Manual. Lincoln Park Zoo. Chicago, Illinois.
  • Faust, L.J., Bergstrom, Y.M., Thompson, S.D., & Bier, L. (2012). PopLink Version 2.3. Lincoln Park Zoo. Chicago, Illinois.
  • Faust, L.J., Cress, D., Farmer, K., Ross, S.R., Beck, B. (2011). Predicting capacity demand on African chimpanzee sanctuaries. International Journal of Primatology, 32, 849–864.
  • Faust, L.J., Szymanski, J., Redmer, M. (2011). Range-wide extinction risk modeling for the eastern massasauga rattlesnake (Sistrurus catenatus catenatus). Technical Report to the U.S. Fish and Wildlife Service.
  • Ballou, J., Lees, C., Faust, L., Long, S., Lynch, C., Bingaman-Lackey, L., & Foose, T. (2010). Demographic and genetic management of captive populations for conservation. In D. Kleiman, K. Thompson, & C. Baer (Eds.), Mammals in Captivity: Principles and Techniques for Zoo Management (pp. 236-269). University of Chicago Press.
  • Foley, C.A.H., & Faust, L.J. (2010). Rapid population growth in an elephant Loxodonta africana population recovering from poaching in Tarangire National Park, Tanzania. Oryx, 44(2), 205–212.
  • Earnhardt, J.M. (2010). The role of captive populations in reintroduction programs. In D. Kleiman, K. Thompson, C. Baer (Eds.), Wild Mammals In Captivity: Principles and Techniques for Zoo Management (pp. 268–280). University of Chicago Press.
  • Earnhardt J., Faust, L.J., and Thompson, S.D. (2009). Extinction risk assessment for the Species Survival Plan® (SSP) population of the Bali mynah (Leucopsar rothschildi). Zoo Biology, 28(3), 230–252.
  • Earnhardt, J.M., Bergstrom, Y.M., Lin, A., Faust, L.J., Schloss, C.A., and Thompson, S.D. (2008). ZooRisk: A Risk Assessment Tool. Version 3.8. Lincoln Park Zoo. Chicago, Illinois.
  • Faust, L.J., Earnhardt, J.M., Schloss, C.A., and Bergstrom, Y.M. (2008). ZooRisk: A Risk Assessment Tool. Version 3.8 User’s Manual. Lincoln Park Zoo. Chicago, Illinois.
  • Faust L.J., Earnhardt, J.E., & Thompson, S.D. (2006). Is reversing the decline of Asian elephants in North American zoos possible? An individual-based modeling approach., Zoo Biology, 25(3), 201–218.
  • Cronin, K., Mitchell, M., Lonsdorf, E.V., & Thompson, S.D. (2006). One year later: evaluation of PMC-recommended births and transfers. Zoo Biology, 25(4), 267–278.
  • Faust, L.J., Jackson, R., Ford, A., Earnhardt, J.M., & Thompson, S.D. (2004). Models for management of wildlife populations: Lessons from spectacled bears in zoos and grizzly bears in Yellowstone. System Dynamics Review, 20(2), 163–178.
  • Earnhardt, J.M., Thompson, S.D., & Schad, K. (2004). Strategic planning for captive populations: projecting changes in genetic diversity. Animal Conservation, 7(1), 9–16.
  • Faust, L.J., & Earnhardt, J.M. (2004). Zoo Risk: A Risk Assessment Tool. User’s Manual. Lincoln Park Zoo. Chicago, Illinois.
  • Faust, L.J., Thompson, S.D., Earnhardt, J.M., Brown, E., Ryan, S., Sherman, M., & Yurenka, M. (2003). Using stage-based system dynamics modeling for demographic management of captive populations. Zoo Biology, 22(1), 45–64.
  • Ryan, S.J., Thompson, S.D., Roth, A., & Gold, K. (2002). Effects of hand-rearing on the reproductive success of western lowland gorillas in North America. Zoo Biology, 21(4), 389–402.
  • Ryan, S.J. & Thompson, S.D. (2001). Disease risk and inter-institutional transfer of specimens in cooperative breeding programs: Herpes and the elephant Species Survival Plans. Zoo Biology, 20(2), 89–101.
  • Earnhardt, J.M., Thompson, S.D., & Marhevsky, E. (2001). Interactions of target population size, population parameters, andpProgram management of viability of captive populations. Zoo Biology, 20(3), 169–183.
  • Faust, L.J., &Thompson, S.D. (2000). Birth sex ratio in captive mammals: Patterns, biases, and the implications for management and conservation. Zoo Biology, 19(1), 11–25.
  • Thompson, S.D. (1999). Data collection, record keeping, and population biology issues for species maintained as groups. Proceedings of the First Workshop on Colony Management.
  • Earnhardt, J.M. (1999). Reintroduction programmes: genetic tradeoffs for populations. Animal Conservation, 2(4), 279–286.
  • Earnhardt, J.M., Thompson, S.D., & Turner-Erfort, G. (1998). Standards for data entry and maintenance of North American zoo and aquarium animal records databases. Lincoln Park Zoo, Chicago, Illinois.
  • Thompson, S.D., Earnhardt, J.M. and Turner-Erfort, G. (1997). Guidelines for data entry and maintenance of AZA regional studbooks. Lincoln Park Zoo, Chicago, Illinois.
  • Earnhardt, J.M., Thompson, S.D., & Willis, K. (1995). Reply to Flesness et al. Zoo Biology, 14(6), 519–522.
  • Earnhardt, J., Thompson, S.D., & Willis, K. (1995). The ISIS database: An evaluation of records essential for captive management. Zoo Biology, 14(6), 493–508.
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