Red wolves lying in the dirt in exhibit 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 how different demographic, genetic, and management strategies affect populations in zoos and the wild. The goal of this research is to understand what puts animal populations at risk of extinction and find new management strategies to counteract those threats. As biodiversity continues to decline worldwide, these efforts are critical for effectively saving species.

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

Areas of Focus

Conducting Population Viability Analyses

As zoo and wild populations become smaller and more isolated, they are more at risk of decline and extinction. Scientists at the Alexander Center build computer models that project what animal populations will look like in the future as a result of their current biology and the threats they face. In collaboration with conservation managers, they then use these models to identify the best management strategies to reduce extinction risk and maintain viable populations for the long-term. They also give actionable advice for species in zoos and the wild, from eastern massasauga rattlesnakes to African elephants.

Advising Reintroduction Programs

Wildlife reintroductions—the release of individuals 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 plays a critical role in supporting the demographic and genetic management and reintroduction strategy for a range of animal species. This includes the greater sage grouse in Canada, Puerto Rican parrots, and red wolves in collaboration with the U.S. Fish and Wildlife Service. Efforts like these will play a vital role in conservation as more wildlife populations decline due to human influences.

Improving Conservation and Management

The Alexander Center conducts hypothesis-driven research and comparative analyses to find solutions in population biology and improve the management of both small zoo and wild populations. For example, the scientists study the demographic and genetic characteristics of animal populations to explore what makes some populations more successful than others, whether and how zoo populations are changing over time, and which management strategies are most effective for achieving healthy populations.

Freely Available Software

The Alexander Center creates tools to support the efforts of conservation managers and the wider scientific community. Staff build databases that aggregate essential population biology data, and they develop software to 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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The COMPADRE and COMADRE Matrix Database is an open-access repository of demographic data for thousands of plant and animal species around the world.

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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.

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  • Che-Castaldo, J., Jones, O. R., Kendall, B. E., Burns, J. H., Childs, D. Z., Ezard, T. H. G., Hernandez-Yanez, H., Hodgson, D. J., Jongejans, E., Knight, T., Merow, C., Ramula, S., Stott, I., Vindenes, Y., Yokomizo, H., & 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., Terwilliger, L., Theis, M., Long, S., & 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, Early View.
  • Faust, L. J. 2019. What Keeps Me up at Night As a Zoo-Based Conservation Biologist. The Bulletin of the Ecological Society of America, 100(1), e01490.
  • Gray, S. M., Roloff, G. J., Dennhardt, A. J., Dotters, B. P., & Engstrom, T. T. 2019. Within-Patch Structures Influence Small Mammal Abundance in Managed Forests of Northern California, USA. Forest Science, , fxz037,
  • Montgomery R.A., Elliott K.C., Hayward M.W., Gray S.M., Millspaugh J.J., Riley S.J., Kissui B.M., Kramer D.B., Moll R.J., Mudumba T., Tans E.D., Muneza A.B., Abade L., Beck J.M., Hoffmann C.F., Booher C.R. & Macdonald D.W. 2018. Examining evident interdisciplinarity among prides of lion researchers. Frontiers in Ecology and Evolution 6(49): 1-13. doi: 10.3389/fevo.2018.00049
  • Allen, M.L., B. Wojcik, B.E. Evans, E.E. Iehl, R.E. Harris, M.E. Wheeler, B.E. Peterson, R.L. Dohm, M.A. Mueller, L. Olson, B. Ederer, M. Stewart, S. Crimmins, K. Pemble, E. Olson, J. Van Stappen, T.R. Van Deelen. 2018. Detection of endangered American martens (Martes americana) in Apostle Islands National Lakeshore, Wisconsin. American Midland Naturalist 179: 294-298
  • Hileman Eric T., King Richard B., & Faust Lisa J. 2018. Eastern massasauga demography and extinction risk under prescribed‐fire scenarios. The Journal of Wildlife Management, Early View.
  • Rosa, I. M. D., Rentsch, D., & Hopcraft, J. G. C. 2018. Evaluating Forest Protection Strategies: A Comparison of Land-Use Systems to Preventing Forest Loss in Tanzania. Sustainability, 10(12), 4476.
  • 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.
  • Che‐Castaldo, J., Che‐Castaldo, C., & Neel, M. C. 2018. Predictability of demographic rates based on phylogeny and biological similarity. Conservation Biology, (Early View).
  • 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.
  • Gray, S. M., Montgomery, R. A., Millspaugh, J. J., & Hayward, M. W. 2017. Spatiotemporal variation in African lion roaring in relation to a dominance shift. Journal of Mammalogy, 98(4), 1088–1095.
  • Allen, M. L., M. J. Morales, M. Wheeler, J. D. J. Clare, M. A. Mueller, L.O. Olson, K. Pemble, E. R. Olson, J. Van Stappen, and T. R. Van Deelen. 2017. Survey techniques and community dynamics of the carnivore guild in the Apostle Islands National Lakeshore (2014-2017). Final Report to the National Park Service
  • Moll, R. J., Redilla, K. M., Mudumba, T., Muneza, A. B., Gray, S. M., Abade, L., Hayward, M.W., Millspaugh, J.J., & Montgomery, R. A. 2017. The many faces of fear: A synthesis of methodological variation in characterizing predation risk. Journal of Animal Ecology, 86(4), 749–765.
  • Meyerson, R., D. Moore, S. Long, and J. Che-Castaldo. 2017. Welfare of captive polar bears and their value to in situ conservation efforts. In A. Butterworth, editor, Marine Mammal Welfare: Human Induced Change in the Marine Environment and its Impacts on Marine Mammal Welfare. pages 489–502. Springer
  • Hernández-Yáñez, H., J. Kos, M.D. Bast, J.L. Griggs, P.A. Hage, A. Killian, M.I. Loza, M.B. Whitmore, A.B. Smith. 2016. A systematic assessment of threats affecting the rare plants of the United States. Biological Conservation 203: 260-267
  • Salguero-Gómez, R., O.R. Jones, C.R. Archer, C. Bein, H. de Buhr, et al. 2016. COMADRE: A global database of animal demography. Journal of Animal Ecology 85(2):371-384
  • Gray, S. M., Killion, A. K., Roloff, G. J., Dotters, B. P., & Engstrom, T. T. 2016. Fine-Scale Correlates of Small Mammal Abundance in Industrial Forests of Northern California. Northwest Science, 90(3), 301–314.
  • 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
  • D.M. Evans, J.P. Che-Castaldo, D. Crouse, F.W. Davis, R. Epanchin-Niell, et al. 2016. Species recovery in the United States: Increasing the effectiveness of the Endangered Species Act. Issues in Ecology #20
  • Che-Castaldo, J.P. and M.C. Neel. 2016. Species-level persistence probabilities for recovery and conservation status assessment. Conservation Biology 30(16):1297-1306
  • 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
  • Wei, C.A., W.R. Burnside, and J.P. Che-Castaldo. 2015. Teaching socio-environmental synthesis with the case study approach. Journal of Environmental Studies and Sciences 5(1):42-49
  • Che-Castaldo, J.P. and D.W. Inouye. 2015. Interspecific competition between a non-native metal-hyperaccumulating plant (Noccaea caerulescens, Brassicaceae) and a native congener across a soil metal gradient. Australian Journal of Botany (special issue on Ultramafic Ecosystems) 63(2):141–151
  • Matthew C. Allender; Randall E. Junge; Sarah Baker-Wylie; Eric T. Hileman; Lisa J. Faust; and Carolyn Cray. In press. 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
  • Xu, C.C.Y., Yen, I.J., Bowman, D., & Turner C.R. 2015. Spider Web DNA: A New Spin on Noninvasive Genetics of Predator and Prey. PLoS ONE 10(11): e0142503.
  • Salguero-Gómez, R., O.R. Jones, C.R. Archer, Y.M. Buckley, J. Che-Castaldo et al. 2015. The COMPADRE plant matrix database: An open online repository for plant demography. Journal of Ecology 103(1): 202-218
  • Che-Castaldo, J.P. and D.W. Inouye. 2014. Field germination and survival of experimentally introduced metal hyperaccumulator Noccaea caerulescens (Brassicaceae) across a soil metal gradient. American Midland Naturalist 171(2): 229-245
  • Pellowe-Wagstaff, K. E. and J. L. Simonis 2014. The ecology and mechanisms of overflow-mediated dispersal in a rock-pool metacommunity. Freshwater Biology 59(6): 1161-1172
  • 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
  • Zeigler, S.L., J.P. Che-Castaldo, and M.C. Neel. 2013. Actual and potential use of population viability analysis in recovery of plant species listed under the U.S. Endangered Species Act.. Conservation Biology 27(6): 1265–1278
  • Belle, R.C., Belmaker, A., Couch, C.S., Marchetto, K.M., Simonis, J.L., Thomas, R.Q., Sparks, J.P., Brown, J.M., Francisco, K.S., Manuel, M.E. 2013. Effectiveness of Erythrina gall wasp biocontrol and implications for the recovery of threatened Wiliwili trees (Fabaceae: Erythrina sandwisensis). Journal of the Torrey Botanical Society, 140(2): 215-224
  • Simonis, J.L. 2013. Predator ontogeny determines trophic cascade strength in freshwater rock pools. Ecosphere, 4(5): 62
  • Neel, M.C. and J.P. Che-Castaldo. 2013. Predicting recovery criteria for threatened and endangered plant species based on past abundances and biological traits. Conservation Biology. 27(2): 385-397
  • Simonis, J.L. 2013. Prey (Moina macrocopa) population density drives emigration rate of its predator (Trichocorixa verticalis) in a rock-pool metacommunity. Hydrobiologia, 715(1): 19-27
  • Hernández-Yáñez, H., N. Lara-Rodriguez, C. Díaz-Castelazo & V. Rico-Gray. 2013. Understanding the complex structure of plant-floral visitor network from different perspectives in coastal Veracruz, Mexico. Sociobiology 3: 329-336
  • Simonis, J.L, D. Neuharth-Keusch, and I. Hewson. 2012. Aquatic bacterial assemblage variability in the supra littoral zone of Appledore Island, Gulf of Maine. FEMS Microbiology Ecology 80: 501-508
  • Simonis, J.L. 2012. Demographic stochasticity reduces the synchronizing effect of dispersal in predator-prey metapopulations. Ecology 93: 1517-1524
  • Sosa-López, J.R., J.E. Martínez-Gómez, H. Hernández-Yáñez, D.J. Menill. 2012. Description of the nest, eggs and parental behavior of the Clarion wren (Troglodytes tanneri), a vulnerable island-endemic songbird. Ornitologia Neotropical 23: 291-298
  • Faust, LJ, Bier, L, Schowe, K, and Gazlay, T 2012. PopLink 2.3 User’s Manual. Lincoln Park Zoo. Chicago, IL
    Faust, LJ, Bergstrom, YM, Thompson, SD, and Bier, L. 2012. Poplink Version 2.3. Lincoln Park Zoo. Chicago, IL
  • Simonis, J.L. 2012. Prey (Moina macrocopa) population density drives emigration of predator (Trichocorixa verticalis) in a rock-pool metacommunity. Hydrobiologia, DOI: 10.1007/s10750-012-1268-9
  • Che-Castaldo, J.P. and M.C. Neel. 2012. Testing surrogacy assumptions: Can threatened and endangered plants be grouped by biological similarity and abundances?. PLoS ONE 7(12): e51659
  • Capps, K.A., M.T. Booth, S.M. Collins, M.A. Davison, J.M. Moslemi, R.W. El-Sabaawi, J.L. Simonis, and A.S. Flecker. 2011. Nutrient diffusing substrata: a field comparison of commonly used methods to assess nutrient limitation. Journal of the North American Benthological Society 30: 522-532
  • Faust, LJ, Bergstrom, YM, and Thompson, SD, and Bier, L. 2011. PopLink Version 2.2. Lincoln Park Zoo. Chicago, IL
  • Faust, LJ, Bier, L, Schowe, K, and Gazlay, T. 2011. PopLink Version 2.2 User’s Manual. Lincoln Park Zoo. Chicago, IL
  • Faust, LJ, 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
  • Che-Castaldo, J.P. and D.W. Inouye. 2011. The effects of dataset length and mast seeding on the demography of Frasera speciosa, a long-lived monocarpic plant. Ecosphere 2: article 126
  • Earnhardt, J.M., K. Schowe, and J. McGill. 2011. The size and composition of release cohorts in avian reintroduction programs: implications for population recovery. In preparation
  • Ballou, J., Lees, C., Faust, L., Long, S., Lynch, C., Bingaman-Lackey, L., and Foose, T. 2010. Demographic and Genetic management of captive populations for conservation. Wild Mammals in Captivity. University of Chicago Press, Chicago, Illinois
  • Foley, C.A.H., and 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. Kleiman, DG, Thompson, KV, Baer, CK (editors). Wild Mammals In Captivity. University of Chicago Press, Chicago. p 268-280
  • 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). American Journal of Physical Anthropology (Suppl 44): 123-124
  • Hall, S.R., C. Becker, J.L. Simonis, M.A. Duffy, A.J. Tessier, and C.E. Cáceres. 2009. Friendly competition: evidence for a dilution effect among competitors in a planktonic host-parasite system. Ecology: 90 791-801
  • Faust, L.J., Bier, L., and Schowe, K. 2009. PopLink 2.1: User’s Manual. Lincoln Park Zoo. Chicago, IL
    Faust, L.J., Bergstrom, Y.M., Thompson, S.D., and Bier, L. 2009. PopLink Version 2.1. Lincoln Park Zoo. Chicago, IL
  • Hall, S.R., J.L. Simonis, R.M. Nisbet, A.J. Tessier, and C.E. Cáceres. 2009. Resource ecology of virulence in a planktonic host-parasite system: an explanation using dynamic energy budgets. American Naturalist 174: 149-162
  • Simonis, J.L., H.A. Raja, and C.A. Shearer. 2008. Extracellular enzymes and soft-rot decay: are ascomycetes important degraders in freshwater?. Fungal Diversity 31: 135-146
  • Earnhardt, JM, Bergstrom, YM, Lin, A, Faust, LJ, Schloss, CA, and Thompson, SD. 2008. ZooRisk: A Risk Assessment Tool. Version 3.8. Lincoln Park Zoo. Chicago, IL
  • Faust, LJ, Earnhardt, JM, Schloss, CA, and Bergstrom, YM. 2008. ZooRisk: A Risk Assessment Tool. Version 3.8 User’s Manual. Lincoln Park Zoo. Chicago, IL
  • Faust L.J., Earnhardt, J.E. and Thompson, S.D. 2006. Is reversing the decline of Asian elephants in captivity possible? An individual-based modeling approach. Zoo Biology, 25(3): 201-218
  • Cronin, K., Mitchell, M., Lonsdorf, E.V. and Thompson, S.D. 2006. One year later: evaluation of the PMC-recommended births and transfers. Zoo Biology, 25: 267-278
  • LeClerc, J.E., J.P. Che, J.P. Swaddle, and D.A. Cristol. 2005. Reproductive success and developmental stability of eastern bluebirds (Sialia sialis) on golf courses: evidence that golf courses can be productive. Wildlife Society Bulletin 33(2): 483-493
  • Faust, L.J. 2004. Animal Attractions: Nature on Display in American Zoos (Book Review). Quarterly Review of Biology, 79(4): 431
  • Faust, L.J., Jackson, R., Ford, A., Earnhardt, J. M. and 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. and Schad, K. 2004. Strategic planning for captive population: projecting changes in genetic diversity. Animal Conservation, 7: 9-16
  • Swaddle, J.P., J.P. Che, and R.E. Clelland. 2004. Symmetry preference as a cognitive by-product in starlings. Behaviour 141: 469-478
  • Faust, L.J. and Earnhardt, J.M. 2004. Zoo Risk: A Risk Assessment Tool. User’s Manual.. User’s Manual. Lincoln Park Zoo, Chicago, Illinois.
  • Faust, L.J., Thompson, S.D., Earnhardt, J.M., Brown, E., Ryan, S., Sherman, M. and Yurenka, M. 2003. Using stage-based system dynamics modeling for demographic management of captive populations. Zoo Biology, 22: 45-64
  • Ryan, S.J., Thompson, S.D., Roth, A. and Gold, K. 2002. Effects of hand-rearing on the reproductive success of western lowland gorillas in North America. Zoo Biology, 21: 389-402
  • Ryan, S.J. and Thompson, S.D. 2001. Disease risk and inter-institutional transfer of specimens in cooperative breeding programs: Herpes and elephant Species Survival Plans. Zoo Biology, 20: 89-101
  • Earnhardt, J.M., Thompson, S.D. and Marhevsky, E. 2001. Interactions of Target Population Size, Population Parameters, and Program Management of Viability of Captive Populations. Zoo Biology, 20: 169-183
  • Faust, L.J. and Thompson, S.D. 2000. Birth sex ratio in captive mammals: Patterns, bias, and the implications for management and conservation. Zoo Biology, 19: 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: 279-286
  • Faust, L.J. and Brown, J.M. 1998. Sexual selection via female choice in the gall-making fly Eurosta solidaginis Fitch (Diptera: Tephritidae) in Biology of Gall-inducing Arthropods. North Central Research Station, Forest Service U.S. Department of Agriculture, 82-90
  • Earnhardt, J.M., Thompsom, S.D. and 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 North American Regional Studbooks. Lincoln Park Zoo, Chicago, Illinois
  • Thompson, S.D. 1995. Captive breeding for wildlife conservation: A review of Creative Conservation: Interactive Management of Wild and Captive Animals. Zoo Biology, 14: 285-297
  • Earnhardt, J.M., Thompson, S.D. and Willis, K. 1995. Reply to Flesness et al. Zoo Biology, 14: 519-522
    Earnhardt, J., Thompson, S.D. and Willis, K. 1995. The ISIS database: An evaluation of records essential for captive management. Zoo Biology, 14: 493-508
  • Gray, S. M., Roloff, G. J., Montgomery, R. A., Beasley, J. C, & Pepin, K. M. . Invasive Wild Pigs in North America: Ecology, Impacts and Management (in press). Behaviors and Spatial Ecology. In K. C. VerCauteren, J. C. Beasley, S. S. Ditchkoff, J. J. Mayer, G. J. Roloff, and B. K. Strickland (Eds.)