Katherine Ralls is a mammalogist and conservation biologist emerita at the Smithsonian Conservation Biology Institute's Center for Conservation Genomics. She was one of the first scientists hired at the Smithsonian's National Zoo and was one of the founders of the Society for Conservation Biology. Ralls studies the behavioral ecology, genetics and conservation of terrestrial and marine mammals. She has conducted field studies of sea otters, San Joaquin kit foxes and island foxes.

Ralls' research interests include:

• Genetic management of small captive and wild populations


• Behavioral ecology, genetics and conservation of mammals


• Field studies of sea otters and foxes


• Sexual dimorphism, mating systems, scent marking and tool-use

Ralls' early papers on scent marking and sexual dimorphism have been widely cited. Her pioneering work on inbreeding problems in zoo animals, along with SCBI's Jon Ballou, led to the genetic and demographic management of captive populations now practiced in zoos worldwide. Most recently, Ralls and Ballou were among the co-authors of the first textbook on the genetic management of fragmented wild animal and plant populations.

Ralls did her undergraduate work at Stanford University. She earned her master's degree at Radcliffe College and her doctorate in biology at Harvard University. Ralls was the 1996 recipient of the American Society of Mammalogist's C. Hart Merriam Award and the Society for Conservation Biology's Edward T. LaRoe Award. In 2006, she was named an Honorary Fellow of the Zoological Society of London, and in 2015 she was named an Honorary Member of the American Society of Mammalogists.

Article

• Ralls, Katherine, Wilbert, Tammy, Cypher, Brian, Van Horn Job, Christine, and Maldonado, Jesus E. 2024. "Social and genetic relationships among individuals in urban kit fox social groups." Canadian journal of zoology, https://doi.org/10.1139/cjz-2024-0057. 2024
• Bertola, Laura D., Brüniche‐Olsen, Anna, Kershaw, Francine, Russo, Isa‐Rita M., MacDonald, Anna J., Sunnucks, Paul, Bruford, Michael W., Cadena, Carlos Daniel, Ewart, Kyle M., De Bruyn, Mark, Eldridge, Mark D. B., Frankham, Richard, Guayasamin, Juan M., Grueber, Catherine E., Hoareau, Thierry B., Hoban, Sean, Hohenlohe, Paul A., Hunter, Margaret E., Kotze, Antoinette, Kuja, Josiah, Lacy, Robert C., Laikre, Linda, Lo, Nathan, Meek, Mariah H., Mergeay, Joachim et al. 2023. "A pragmatic approach for integrating molecular tools into biodiversity conservation." Conservation Science and Practice, https://doi.org/10.1111/csp2.13053. 2023
• Parker, Lillian D., Campana, Michael G., Quinta, Jessica D., Cypher, Brian, Rivera, Isabel, Fleischer, Robert C., Ralls, Katherine, Wilbert, Tammy R., Boarman, Ryan, Boarman, William, I., and Maldonado, Jesus E. 2021. "An efficient method for simultaneous species, individual, and sex identification via in-solution single nucleotide polymorphism capture from low-quality scat samples." Molecular Ecology Resources, https://doi.org/10.1111/1755-0998.13552. 2021
• Parker, Lillian D., Campana, Michael G., Quinta, Jessica D., Cypher, Brian, Rivera, Isabel, Fleischer, Robert C., Ralls, Katherine, Wilbert, Tammy R., Boarman, Ryan, Boarman, William I., and Maldonado, Jesús E. 2021. "An efficient noninvasive method for simultaneous species, individual, and sex identification of sympatric Mojave Desert canids via in-solution SNP capture." Authorea, https://doi.org/10.22541/au.162818800.02355889/v1. 2021
• Moran, Brigid M., Thomas, Steven M., Judson, Jessica M., Navarro, Asako, Davis, Heidi, Sidak-Loftis, Lindsay, Korody, Marisa, Mace, Michael, Ralls, Katherine, Callicrate, Taylor, Ryder, Oliver A., Chemnick, Leona G., and Steiner, Cynthia C. 2021. "Correcting parentage relationships in the endangered California Condor: Improving mean kinship estimates for conservation management." Ornithological Applications, 123, (3). https://doi.org/10.1093/ornithapp/duab017. 2021
• Powers, Robyn M., Cypher, Brian L., Ralls, Katherine, Randall, Jan A., and Kelly, Erica C. 2021. "Ecological variation among island foxes relative to reproductive events." California Fish and Game, 107 400–415. https://doi.org/10.51492/cfwj.cesasi.24. 2021
• Larson, Shawn, Gagne, Roderick B., Bodkin, Jim, Murray, Michael J., Ralls, Katherine, Bowen, Lizabeth, Leblois, Raphael, Piry, Sylvain, Penedo, Maria Cecilia, Tinker, M. Tim, and Ernest, Holly B. 2021. "Translocations maintain genetic diversity and increase connectivity in sea otters, Enhydra lutris." Marine Mammal Science, https://doi.org/10.1111/mms.12841. 2021
• Ralls, Katherine, Sunnucks, Paul, Lacy, Robert C., and Frankham, Richard. 2020. "Genetic rescue: A critique of the evidence supports maximizing genetic diversity rather than minimizing the introduction of putatively harmful genetic variation." Biological Conservation, 251 108784–108784. https://doi.org/10.1016/j.biocon.2020.108784. 2020
• Crooks, Kevin R., Mills, L. Scott, Sanjayan, M., Ehrlich, Paul R., Ogden, John C., Allendorf, Fred W., Ralls, Katherine, Noss, Reed F., Mace, Georgina, Estes, James A., Doak, Daniel F., Terborgh, John, and Inouye, David W. 2020. "Reflections on Michael Soule, a visionary for conservation biology." Conservation Biology, https://doi.org/10.1111/cobi.13597. 2020
• Brownell, Robert L., Jr., Reeves, Randall R., Read, Andrew J., Smith, Brian D., Thomas, Peter O., Ralls, Katherine, Amano, Masao, Berggren, Per, Chit, Aung Myo, Collins, Tim, Currey, Rohan, Dolar, M. Louella L., Genov, Tilen, Hobbs, Roderick C., Kreb, Danielle, Marsh, Helene, Zhigang, Mei, Perrin, William F., Phay, Somany, Rojas-Bracho, Lorenzo, Ryan, Gerry E., Shelden, Kim E. W., Slooten, Elisabeth, Taylor, Barbara L., Vidal, Omar et al. 2019. "Bycatch in gillnet fisheries threatens Critically Endangered small cetaceans and other aquatic megafauna." Endangered Species Research, 40 285–296. https://doi.org/10.3354/esr00994. 2019
• Wilbertl, Tammy R., Woollett, Deborah A. Smith, Westphal, Michael F., Whitelaw, Alice, Ralls, Katherine, and Maldonado, Jesús E. 2019. "Distribution, fine-scale subdivision, and population size of San Joaquin kit foxes in the Ciervo-Panoche Natural Area, California." Conservation Genetics, 20, (3) 405–417. https://doi.org/10.1007/s10592-018-1122-3. 2019
• Westall, Tory L., Cypher, Brian L., Ralls, Katherine, and Germano, David J. 2019. "Raising pups of urban San Joaquin kit fox: relative roles of adult group members." Western North American Naturalist, 79, (3) 364–377. https://doi.org/10.3398/064.079.0307. 2019
• Haslam, Michael, Fujii, Jessica, Espinosa, Sarah, Mayer, Karl, Ralls, Katherine, Tinker, M. Tim, and Uomini, Natalie. 2019. "Wild sea otter mussel pounding leaves archaeological traces." Scientific Reports, 9 Article 4417. https://doi.org/10.1038/s41598-019-39902-y. 2019
• Ralls, Katherine, Ballou, Jonathan D., Dudash, Michele R., Eldridge, Mark D. B., Fenster, Charles B., Lacy, Robert C., Sunnucks, Paul, and Frankham, Richard. 2018. "Call for a Paradigm Shift in the Genetic Management of Fragmented Populations." Conservation Letters, 11, (2). https://doi.org/10.1111/conl.12412. 2018
• Gagne, Roderick B., Tinker, M. T., Gustafson, Kyle D., Ralls, Katherine, Larson, Shawn, Tarjan, L. Max, Miller, Melissa A., and Ernest, Holly B. 2018. "Measures of effective population size in sea otters reveal special considerations for wide-ranging species." Evolutionary Applications, 11, (10) 1779–1790. https://doi.org/10.1111/eva.12642. 2018
• Westall, Tory L., Cypher, Brian L., Ralls, Katherine, and Wilbert, Tammy. 2018. "Observations of Social Polygyny, Allonursing, Extrapair Copulation, and Inbreeding in Urban San Joaquin Kit Foxes (Vulpes Macrotis Mutica)." Southwestern Naturalist, 63, (4) 271. https://doi.org/10.1894/0038-4909-63-4-271. 2018
• Fujii, Jessica A., Ralls, Katherine, and Tinker, M. T. 2017. "Food abundance, prey morphology, and diet specialization influence individual sea otter tool use." Behavioral Ecology, 28, (5) 1206–1216. https://doi.org/10.1093/beheco/arx011. 2017
• Pryor, Devon Lang and Ralls, Katherine. 2017. "Fourteen tail feathers: An autosomal recessive trait in california condors (Gymnogyps californianus)." Zoo biology, 36, (1) 1–4. https://doi.org/10.1002/zoo.21335. 2017
• Ralls, Katherine, McInerney, Nancy Rotzel, Gagne, Roderick B., Ernest, Holly B., Tinker, M. T., Fujii, Jessica, and Maldonado, Jesús E. 2017. "Mitogenomes and relatedness do not predict frequency of tool-use by sea otters." Biology Letters, 13, (3). https://doi.org/10.1098/rsbl.2016.0880. 2017
• Westall, Tory L., Cypher, Brian L., and Ralls, Katherine. 2016. "Efficacy of Three Methods for Collecting Behavioral Data on Urban San Joaquin Kit Foxes, Vulpes macrotis mutica." Western Wildlife, 3 1–7. 2016
• Hofman, Courtney A., Rick, Torben C., Maldonado, Jesús E., Collins, Paul W., Erlandson, Jon M., Fleischer, Robert C., Smith, Chelsea, Sillett, T. Scott, Ralls, Katherine, Teeter, Wendy, Vellanoweth, René L., and Newsome, Seth D. 2016. "Tracking the origins and diet of an endemic island canid (Urocyon littoralis) across 7300 years of human cultural and environmental change." Quaternary Science Reviews, 146 147–160. https://doi.org/10.1016/j.quascirev.2016.06.010. 2016
• Dines, James P., Mesnick, Sarah L., Ralls, Katherine, May-Collado, Laura, Agnarsson, Ingi, and Dean, Matthew D. 2015. "A trade-off between precopulatory and postcopulatory trait investment in male cetaceans." Evolution, 69, (6) 1560–1572. https://doi.org/10.1111/evo.12676. 2015
• Fujii, Jessica A., Ralls, Katherine, and Tinker, Martin Tim. 2015. "Ecological drivers of variation in tool-use frequency across sea otter populations." Behavioral Ecology, 26, (2) 519–526. https://doi.org/10.1093/beheco/aru220. 2015
• Hofman, Courtney A., Rick, Torben C., Hawkins, Melissa T. R., Funk, W. C., Ralls, Katherine, Boser, Christina L., Collins, Paul W., Coonan, Tim, King, Julie L., Morrison, Scott A., Newsome, Seth D., Sillett, T. Scott, Fleischer, Robert C., and Maldonado, Jesús E. 2015. "Mitochondrial Genomes Suggest Rapid Evolution of Dwarf California Channel Islands Foxes (Urocyon littoralis)." PloS One, 10, (2) 1–15. https://doi.org/10.1371/journal.pone.0118240. 2015
• Wilbert, Tammy R., Woolett, Debora A., Whitelaw, Alice, Dart, Jason, Hoyt, Joseph R., Galen, Spencer, Ralls, Katherine, Meade, Daniel, and Maldonado, Jesús E. 2015. "Non-invasive baseline genetic monitoring of the endangered San Joaquin kit fox on a photovoltaic solar facility." Endangered Species Research, 27, (1) 31–41. https://doi.org/10.3354/esr00649. 2015
• Rick, Torben C., Sillett, T. Scott, Ghalambor, Cameron K., Hofman, Courtney A., Ralls, Katherine, Anderson, R. S., Boser, Christina L., Braje, Todd J., Cayan, Daniel R., Chesser, R. Terry, Collins, Paul W., Erlandson, Jon M., Faulkner, Kate R., Fleischer, Robert C., Funk, W. C., Galipeau, Russell, Huston, Ann, King, Julie, Laughrin, Lyndal, Maldonado, Jesús E., McEachern, Kathryn, Muhs, Daniel R., Newsome, Seth D., Reeder-Myers, Leslie, Still, Christopher et al. 2014. "Ecological Change on California's Channel Islands from the Pleistocene to the Anthropocene." Bioscience, 64, (8) 680–692. https://doi.org/10.1093/biosci/biu094. 2014
• Frankham, Richard, Lacy, Robert C., Ballou, Jonathan D., Dudash, Michele R., Eldridge, Mark D. B., Fenster, Charles B., Mendelson, Joseph R., III, Porton, Ingrid J., Ralls, Katherine, and Ryder, Oliver A. 2014. "Species concepts for conservation - Reply to Russello and Amato." Biological Conservation, 170 334–335. https://doi.org/10.1016/j.biocon.2013.12.039. 2014
• Curry, B. E., Ralls, Katherine, and Brownell, R. L. 2013. "Prospects for captive breeding of poorly known small cetacean species." Endangered Species Research, 19 223–243. 2013
• Ralls, Katherine, Sanchez, Jessica N., Savage, Jennifer, Coonan, Timothy J., Hudgens, Brian R., and Cypher, Brian L. 2013. "Social relationships and reproductive behavior of island foxes inferred from proximity logger data." Journal of mammalogy, 94, (6) 1185–1196. https://doi.org/10.1644/13-MAMM-A-057.1. 2013
• Regan, Tracey J., Taylor, Barbara L., Thompson, Grant G., Cochrane, Jean Fitts, Ralls, Katherine, Runge, Michael C., and Merrick, Richard. 2013. "Testing Decision Rules for Categorizing Species’ Extinction Risk to Help Develop Quantitative Listing Criteria for the U.S. Endangered Species Act." Conservation Biology, 27, (4) 821–831. https://doi.org/10.1111/cobi.12055. 2013
• Frankham, Richard, Ballou, Jonathan D., Dudash, Michele R., Eldridge, Mark D. B., Fenster, Charles B., Lacy, Robert C., Mendelson, Joseph R., III, Porton, Ingrid J., Ralls, Katherine, and Ryder, Oliver A. 2012. "Implications of different species concepts for conserving biodiversity." Biological Conservation, 153 25–31. https://doi.org/10.1016/j.biocon.2012.04.034. 2012
• Frankham, Richard, Ballou, Jonathan D., Eldridge, Mark D. B., Lacy, Robert C., Ralls, Katherine, Dudash, Michele R., and Fenster, Charles B. 2011. "Predicting the Probability of Outbreeding Depression." Conservation Biology, 25, (3) 465–475. https://doi.org/10.1111/j.1523-1739.2011.01662.x. 2011
• Bozarth, Christine A., Alva-Campbell, Yvette R., Ralls, Katherine, Henry, Tammy R., Smith, Deborah A., Westphal, Michael F., and Maldonado, Jesús E. 2010. "An efficient noninvasive method for discriminating among faeces of sympatric North American Canids." Conservation Genetics Resources, 2, (1) 173–175. https://doi.org/10.1007/s12686-010-9215-4. 2010
• Ralls, Katherine, Sharma, Sandeep, Smith, Deborah A., Bremner-Harrison, Samantha, Cypher, Brian L., and Maldonado, Jesús E. 2010. "Changes in Kit Fox Defecation Patterns During the Reproductive Season: Implications for Noninvasive Surveys." Journal of Wildlife Management, 74, (7) 1457–1462. 2010
• Newsome, Seth D., Ralls, Katherine, Job, Christine Van Horn, Fogel, Marilyn L., and Cypher, Brian L. 2010. "Stable isotopes evaluate exploitation of anthropogenic foods by the endangered San Joaquin kit fox (Vulpes macrotis mutica)." Journal of Mammalogy, 91, (6) 1313–1321. https://doi.org/10.1644/09-MAMM-A-362.1. 2010
• Newsome, Seth D., Bentall, Gena B., Tinker, M. Tim, Oftedal, Olav T., Ralls, Katherine, Estes, James A., and Fogel, Marilyn L. 2010. "Variation in delta C-13 and delta N-15 diet-vibrissae trophic discrimination factors in a wild population of California sea otters." Ecological Applications, 20, (6) 1744–1752. https://doi.org/10.1890/09-1502.1. 2010
• Brownell, Robert L., Jr., Ralls, Katherine, Baumann-Pickering, S., and Poole, M. M. 2009. "Behavior of Melon-Headed Whales, Peponocephala Electra, Near Oceanic Islands." Marine Mammal Science, 25, (3) 639–658. https://doi.org/10.1111/j.1748-7692.2009.00281.x. 2009
• Bakker, V. J., Doak, D. F., Roemer, G. W., Garcelon, D. K., Coonan, T. J., Morrison, S. A., Lynch, C., Ralls, Katherine, and Shaw, R. 2009. "Incorporating Ecological Drivers and Uncertainty into a Demographic Population Viability Analysis for the Island Fox." Ecological Monographs, 79, (1) 77–108. https://doi.org/10.1890/07-0817.1. 2009
• Newsome, S. D., Tinker, M. T., Monson, D. H., Oftedal, Olav T., Ralls, Katherine, Staedler, M. M., Fogel, Marilyn L., and Estes, J. A. 2009. "Using stable isotopes to investigate individual diet specialization in California sea otters (Enhydra lutris nereis)." Ecology, 90, (4) 961–974. https://doi.org/10.1890/07-1812.1. 2009
• Murdoch, J. D., Ralls, Katherine, and Cypher, B. L. 2008. "Barking sequences in San Joaquin kit foxes (Vulpes macrotis mutica)." Southwestern Naturalist, 53 120–126. 2008
• Brownell, Robert L., Jr., Nowacek, D. P., and Ralls, Katherine. 2008. "Hunting cetaceans with sounds: a worldwide review." Journal of Cetacean Research and Management, 10 81–88. 2008
• Oftedal, Olav T., Ralls, Katherine, Tinker, M. T., and Green, A. S. 2008. "Nutritional constraints faced by sea otters: A comparison of diets within and among populations." Symposia of the Comparative Nutrition Society, 7 156–161. 2008
• Murdoch, James D., Ralls, Katherine, Cypher, Brian, and Reading, Richard. 2008. "Social Interactions among San Joaquin Kit Foxes Before, During, and After the Mating Season." Journal of mammalogy, 89, (5) 1087–1093. https://doi.org/10.1644/07-MAMM-A-152.1. 2008
• Jaramillo-Legorreta, A., Rojas-Bracho, L., Brownell, Robert L., Jr., Read, A. J., Reeves, R. R., Ralls, Katherine, and Taylor, Barbara L. 2007. "Saving the vaquita: Immediate action, not more data." Conservation Biology, 21, (6) 1653–1655. 2007
• Ralls, Katherine, Cypher, B., and Spiegel, L. K. 2007. "Social monogamy in kit foxes: formation, association, duration, and dissolution of mated pairs." Journal of Mammalogy, 88, (6) 1439–1446. https://doi.org/10.1644/06-MAMM-A-348R.1. 2007

Book

• Frankham, Richard, Ballou, Jonathan D., Ralls, Katherine, Eldridge, Mark, Dudash, Michele R., Fenster, Charles B., Lacy, Robert C., and Sunnucks, Paul. 2019. A Practical Guide for Genetic Management of Fragmented Animal and Plant Populations. 1 ed. Oxford University Press. 2019
• Frankham, Richard, Ballou, Jonathan D., Ralls, Katherine, Eldridge, Mark D. B., Dudash, Michele R., Fenster, Charles B., Lacy, Robert C., and Sunnucks, Paul. 2017. Genetic Management of Fragmented Animal and Plant Populations. Oxford, UK: Oxford University Press. https://doi.org/10.1093/oso/9780198783398.001.0001. 2017
• Oftedal, Olav T., Ralls, Katherine, Tinker, M. T., and Green, A. S. 2007. Nutritional constraints on the southern sea otter in the Monterey Bay National Marine Sanctuary and a comparison to sea otter populations at San Nicolas Island, California and Glacier Bay, Alaska : final report. Monterey, CA: Monterey Bay Sanctuary Foundation and the Marine Mammal Commission. 2007

Chapter

• Miller, B., Reading, Richard P., Ralls, Katherine, Clark, T., and Estes, J. 2010. "Variables influencing carnivore translocation." In Awakening Spirits: wolves in the southern Rockies. Reading, Richard P. and Phillips, Mike, editors. 61–75. Golden, CO: Fulcrum Publishing. 2010
• Ralls, Katherine and Mesnick, Sarah. 2009. "Sexual dimorphism." In Encyclopedia of marine mammals. Perrin, William F., Wuersig, Bernd, and Thewissen, J. G. M., editors. 1005–1011. Amsterdam, Boston: Academic Press. 2009
• Mesnick, S. L. and Ralls, Katherine. 2008. "Mating systems." In Encyclopedia of Marine Mammals. Perrin, William F., Wursig, B., and Thewissen, J. T. M., editors. 712–719. San Diego: Academic Press. Second 2008
• Ralls, Katherine and Mesnick, S. 2008. "Sexual Dimorphism." In Encyclopedia of Marine Mammals. Perrin, William F., Wuersig, Bernd, and Thewissen, J. G. M., editors. 1005–1011. Amsterdam, Boston: Academic Press. Second 2008

Dataset

• Moran, Brigid M., Thomas, Steven M., Judson, Jessica M., Navarro, Asako, Davis, Heidi, Sidak-Loftis, Lindsay, Korody, Marisa, Mace, Michael, Ralls, Katherine, Callicrate, Taylor, Ryder, Oliver A., Chemnick, Leona G., and Steiner, Cynthia C. 2021. [Dataset] Correcting parentage relationships in the endangered California condor: Improving mean kinship estimates for conservation management. Distributed by Dryad. https://doi.org/10.5061/DRYAD.T1G1JWT1V. 2021

Report

• Regan, Tracey, Taylor, Barbara, Thompson, Grant, Cochrane, Jean, Merrick, Richard, Nammack, Marta, Rumsay, Scott, Ralls, Katherine, and Runge, Michael. 2009. Developing a structure for quantitative listing criteria for teh US Endangered Species Act using performance testing. Phase 1 report. NMFS-SWFSC-437. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center. 2009