Research

The overall goal of my research is to study the origin and conservation of biodiversity. I am an Affiliate of the Cleveland BioScience Alliance, and I conduct research in collaboration with the Cleveland Metroparks Zoo and the Cleveland Museum of Natural History. 

I conduct empirical research in animal welfare, ecology, evolution, neuroendocrinology, physiology, social behavior, and taxonomy and systematics, with a focus on freshwater fishes of North and South America. My applied research seeks to advance the social and psychological wellbeing of aquarium fishes and the management of non-native introduced species. 

Publications

(The articles listed below can be accessed by visiting the journals' websites or by visiting my ResearchGate profile at https://www.researchgate.net/profile/Ronald_Oldfield. Please email me if you need help accessing them.)

Photos and videos

https://digital.case.edu/islandora/object/ksl%3AHminckBehavior

Peer reviewed publications 

Oldfield, R.G., Thal, J.E., Zarlinga, N.J., Lukas, K.E., Wark, J.D. (202X) Behavior of Rio Sao Francisco Piranhas in response to changes in space and density. Submitted.

Fisher, K.J., Miller, M.E., Delomas, T.A., Oldfield, R.G., Dabrowski, K.R. (202X) Response to salinity challenge in hybrid Blood Parrot Cichlids (Vieja melanurus × Amphilophus citrinellus). Submitted.

Oldfield, R.G., Murphy, A.K.  (2024) Life in a fishbowl: Space and environmental enrichment affect behaviour of Betta splendens. Animal Welfare. 33:e1. 

Oldfield, R.G., Thal, J.E., Das, P., Zarlinga, N.J., Lukas, K.E., Wark, J.D. (2023) Agonistic behavior and feeding competition in the largest piranha species, Pygocentrus piraya, in a zoo. Journal of Ethology. 41:25-37.

Oldfield, R.G., Bonano, P.  (2023) Psychological and social well-being of bony fishes in zoos and aquariums. Zoo Biology. 42:185-193.  

Oldfield, R.G. (2022) You can’t betray a fish: One reason eating fish may cause less harm than eating cows. Journal of Animal Ethics. 12:51-58.

*See response by New York Times Best Selling Author Jonathan Balcombe: Balcombe, J.P. (2022) The Betrayed Fish: Reply to Oldfield. Journal of Animal Ethics. 12:59-62.

Cooley, S.M., Oldfield, R.G. (2021) Microhabitat partitioning is driven by preferences, not competition, in two Costa Rican millipede species. Journal of Tropical Ecology. 37:235-239.

Oldfield, R.G., Hooks, J., Sommer, J., McCain, S.C., Lutterschmidt, W.I., Lorenz, O.T., Cohen, A.E., Hendrickson, D.A. (2021) Response to salinity challenge in non-native cichlid fishes of the genus Herichthys introduced in the Gulf Coast Region of the United States. Ichthyology and Herpetology (formerly called Copeia). 109:587-597.

*Oldfield, R.G., Kakuturu, A., Lutterschmidt, W.I., Lorenz, O.T., Cohen, A.E., Hendrickson, D.A. (2021) Live color patterns diagnose species: A tale of two Herichthys. Miscellaneous Publications of the Museum of Zoology, University of Michigan. 209:1-19.

*Invited contribution in a special volume Festschrift for Dr. Gerald R. Smith.

Oldfield, R.G., Harris, R., Hofmann, H.A. (2015) Integrating resource defence theory with a neural nonapeptide pathway to explain territory-based mating systems. Frontiers in Zoology. 12(Suppl. 1): S16.

Krynak, K., Oldfield R.G., Dennis, P., Durkalec, M., Weldon, C. (2015) A novel field technique to determine ploidy in introduced Grass Carp (Ctenopharyngodon idella, Cyprinidae). Biological Invasions. 17:1931-1939.

Oldfield, R.G., Mandrekar, K., Nieves, M.X., Hendrickson, D.A., Chakrabarty, P., Swanson, B.O., Hofmann, H.A. (2015) Parental care in the Cuatro Ciénegas cichlid, Herichthys minckleyi (Teleostei: Cichlidae). Hydrobiologia. 748:233-257.

Oldfield, R.G., Harris, R., Hendrickson, D.A., Hofmann, H.A. (2013) Arginine vasotocin and androgen pathways are associated with mating system variation in North American cichlid fishes. Hormones and Behavior. 64:44-52.

Oldfield, R.G. (2012) [Review of] Sex determination and differentiation in fish. A. Cnaani (ed.) Copeia. 2012(4): 817-821.

Hagan, B., Oldfield, R.G. (2011) The aquatic animal community in the Chagrin River tributary at Case Western Reserve University’s Squire Valleevue Farm. Ohio Biological Survey Notes. 3:11-20.

 *Oldfield, R.G. (2011) Aggression and welfare in a common aquarium fish, the Midas cichlid. Journal of Applied Animal Welfare Science. 14: 340-360. 

*Reported by > 100 news agencies around the world including print editions of National Geographic magazine and the New York Times.

Oldfield, R.G. (2011) Gonad development in the Midas cichlid and the evolution of sex change in fishes. Evolution and Development. 13:352-360.

Oldfield, R.G., Hofmann, H.A. (2011) Neuropeptide regulation of social behavior in a monogamous cichlid fish. Physiology and Behavior. 102:296-303.

Oldfield, R.G. (2009) Captive breeding observations support the validity of a recently described cichlid species in Lake Apoyo, Nicaragua. University of Michigan Museum of Zoology Occasional Papers. 741:1-14.

Oldfield, R.G. (2009) Growth patterns in Midas cichlids are not consistent with a hypothesis of socially controlled sex determination. Copeia. 2009:71-77.

Mandrekar, K. and Oldfield, R.G. (2008) Chemical cues, 3-D structure, and social experience in contests between similar-sized juvenile Midas cichlids. Aqua. International Journal of Ichthyology. 14:141-148.

Oldfield, R.G. (2007) Behavioral interaction, body size, and sex determination in the Midas cichlid, Amphilophus citrinellus. Journal of Fisheries International. 2:242-249.

Chakrabarty, P., Oldfield, R.G., and Ng, H.H. (2006) Nandus prolixus, a new species of leaf fish from northeast Borneo (Teleostei: Perciformes: Nandidae). Zootaxa. 1328:51-61.

Oldfield, R.G., McCrary, J., and McKaye, K.R. (2006) Habitat use, social behavior, and female and male size distributions of juvenile Midas cichlids, Amphilophus cf. citrinellus, in Lake Apoyo, Nicaragua. Caribbean Journal of Science. 42:197-207.

Oldfield, R.G. (2005) Sexual lability and the evolution of sequential hermaphroditism in cichlid fishes. Fish and Fisheries. 6:93-110.

Non-peer reviewed publications

Oldfield, R.G. (2018) Duplication of natural polygynous mating behavior of male Cuatro Ciénegas Cichlid, Herichthys minckleyi, in an aquarium. Buckeye Bulletin. June:22-31.

Oldfield, R.G. (2013) Midas cichlids do not have sex determined by social conditions. Buntbarsche Bulletin. 273: 8-15.

Oldfield, R.G. (2007) Effects of behavioral interaction on sex determination in the Midas cichlid. Ph.D. dissertation, University of Michigan. 219 pp.

Oldfield, R.G. (2006) Fish species observed on the shipwrecks Regina and Sport in Lake Huron. American Currents. 32(2):29.

Oldfield, R.G. (2006) Museum hosts efforts to slow invasive species. The Display Case (newsletter of the University of Michigan Museum of Zoology). March-April:2.

Oldfield, R.G. (2005) Cichlid sex determination research at the University of Michigan. Buntbarsche Bulletin. 229:14-23.

Oldfield, R.G. (2005) Biology, husbandry, and reproduction of freshwater stingrays II. Tropical Fish Hobbyist. September:110-112.

Oldfield, R.G. (2005) Biology, husbandry, and reproduction of freshwater stingrays I. Tropical Fish Hobbyist. August:114-116.

Oldfield, R.G. (2004) Saltwater cichlids. Knowledge of salinity tolerance and preference may allow new species combinations and improved husbandry in aquaria. Freshwater and Marine Aquarium. August:98-104.

Oldfield, R.G. (2001) Choice of arm usage in a Giant Pacific Octopus, Enteroctopus dofleini (Hochberg, 1998), is based on relative proximity to object of interaction. The Cephalopod Page. http://www.thecephalopodpage.org/arms.php

Oldfield, R. (2000) ‘Pseudodoras niger’ (On-line), Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Pseudodoras_niger.html