My research aims to understand how early housing environments impact adult behaviour and health, with the goal of improving the welfare and management of captive animals. In particular, I am interested in answering basic questions of how early housing environments and behaviour interact to impact individual welfare and performance, with an emphasis on environmental enrichment, brain development and behavioural flexibility. I am keen to translate this fundamental knowledge into one particular area of applied ethology: conservation breeding.

My past research (NSERC, Government of the Basque Country) has investigated how environmental enrichment affects stress physiology and brain function, and how these in turn impact the breeding success of a model carnivore, the American mink (Neovison vison). I have also used animal-based measures (e.g. preference tests) to investigate welfare implications of cage standards for this species (NSERC CRD), as well as the differential effects of physical enrichment vs. nesting materials on infant mortality (JMRC).

My current research includes two collaborative projects. The first one, in collaboration with colleagues at the University of Navarra and Tierra Rapaz, investigates how managing the early social environment of barn owls (Tyto alba) influences their fearful behaviour, and how fearfulness in captivity relates to reintroduction success. The second one, in collaboration with colleagues at the Species Conservation Lab in Tallinn Zoological Gardens and the Estonian University of Life Sciences, as well as the Foundation for Research in Ethology and Biodiversity, aims to understand the relative importance of early vs. current environment on the reproductive behaviour and reintroduction success of the critically endangered European mink (Mustela lutreola).

Díez-León, M., Kitchenham, L., Duprey, R., Bailey, C., Choleris, E., Lewis, M., Mason, G. 2019. Neurophysiological correlates of two types of stereotypic behaviour in male American mink (Neovison vison). Behavioural Brain Research 373: 11205.

Martin-Wintle, M., Wintle, N. Díez-León, M., Swaisgood, R., Asa, C. 2019. Improving the sustainability of captive populations with free mate choice. Invited submission to Zoo Biology: Special Issue: "Sustainability of AZA managed populations". Zoo Biology 38: 119-132.

Polanco, A., Díez-León, M., Mason, G. 2018. Stereotypic behaviours are heterogenous in their triggers and treatments in the American mink, Neovison vison, a model carnivore. Animal Behaviour 141: 105-114

Polanco, A., Campbell, D., Díez-León, M., & Mason, G. 2017. Towards a taxonomy of stereotypic behaviours in the American mink (Neovison vison): Homogeneous or heterogeneous?. Applied Animal Behaviour Science: 194: 95-103

Díez-León, M., Quinton, M., Mason, G. 2017. Preference for cage height in a model organism, the American mink (Neovison vison). Applied Animal Behaviour Science 192: 24-34

Díez-León, M., Bursian, S., Napolitano, A., Palme, R., Galicia, D., Mason, G. 2016. Environmentally enriching American mink (Neovison vison) increases lymphoid organ weight and skeletal symmetry, and reveals differences between two sub-types of stereotypic behaviour. Applied Animal Behaviour 177: 59-69

Díez-León, M., Mason, G. 2016. Effects of environmental enrichment on aspects of maternal behavior, and infant growth and mortality, in American mink (Neovison vison). Zoo biology 35:19-28

Díez-León, M., Miranda, R., Ariño, A. H., Galicia, D. 2015. Setting priorities for existing conservation needs of crayfish and mink. Conservation Biology 29: 599-601

Meagher, R., Dallaire, J., Campbell, D., Buob, M., Hansen, S., Díez-León, M., Palme, R., Mason, G. 2014. Benefits of a ball and chain: simple environmental enrichments improve welfare and reproductive success in farmed American mink (Neovison vison). PLOS ONE 9: e110589

Walker, M., Díez-León, M., Mason, G. 2014. Animal welfare science: recent publication trends and future research priorities. International Journal of Comparative Psychology 27:80-100

Díez-León, M., Bowman, J., Bursian, S., Filion, H., Galicia, D., Kanefsky, J., Napolitano, A., Palme, R., Schulte-Hostedde, A., Scribner, K., Mason, G. 2013. Captive rearing environments that induce stereotypies compromise copulatory performance in a model carnivore, the American mink (Neovison vison). PLoS ONE 8: e80494

Meagher, R. K., Bechard, A., Palme, R., Díez-León, M., Hunter, B., Mason, G. 2013. Sleeping tight or hiding in fright? The welfare implications of different subtypes of inactivity in mink. Applied Animal Behaviour Science 144: 138-146

Meagher, R. K., Bechard, A., Palme, R., Díez-León, M., Hunter, B., Mason, G. 2012. Decreased litter size in inactive female mink (Neovison vison): mechanisms and implications for overall productivity. Canadian Journal of Animal Science 92: 131-141

Dallaire, J., Meagher, R. K., Díez-León, M., Garner, J. P. & Mason, G. J. 2011. Recurrent perseveration correlates with abnormal repetitive locomotion in adult mink but is not reduced by environmental enrichment. Behavioural Brain Research 224: 213-222