My group's research is focused on understanding the relative importance of early vs. current environment on adult animal behaviour, with particular emphasis on behavioural flexibility and development of social and cognitive skills in captivity, as key to ensure optimal welfare and performance. We apply this knowledge to, for example, tackle abnormal behaviour in individuals under human management, and improve reproductive and reintroduction success in conservation breeding programmes. We work both on species of conservation interest, as well as domesticated species. Here are some of our current projects:

Understanding causes of abnormal reproductive behaviour in the critically endangered European mink (Mustela lutreola) (partially funded by the Estonian Research Council)
Captive-born European mink males miss out on mating opportunities with receptive females, either ignoring or attacking them, jeopardizing conservation breeding efforts. Our goal is to understand the causal basis underpinning this seemingly malfunctional behaviour - and welfare-related factors in particular - to devise practical ways to improve breeding performance and reintroduction success. Partners: Species Conservation Lab in Tallinn Zoological Gardens, Foundation for Research in Ethology and Biodiversity.

Maternal influences in the development of abnormal oral repetitive behaviour and its precursors in foals (Equus caballus) (partially funded by the RVC Internal Equine Fund)
In horses, abnormal oral repetitive behaviours such as crib biting raise welfare concerns and can affect foal trainability and value. We are working to understand how maternal characteristics - from behaviour to gut microbiome and personality - influence the development of crib-biting and its precursors in foals in order to develop early interventions to tackle these behaviours.

Welfare and reproductive success in zoo-housed Pallas's cats (Otocolobus manul) (partly funded by UFAW)
Surprisingly for a naturally wide-ranging carnivore, Pallas's cats in zoos have not been reported to perform abnormal repetitive behaviours such as pacing, yet their high susceptibility to toxoplasmosis and elevated infant mortality raise concerns about their welfare. We are working with EAZA and AZA to devise evidence-based guidelines to raise the standards of care for these felines.

Current group members: postdoctoral fellow Dr. Kairi Kiik, and PhD students Aline Bouquet and Andrea Marín Sierra. Contact me if you're interested in joining our research team!

In addition, we are involved in the following projects led by our collaborators:
Long-term effects of the early environment for mink kit performance, stress responsiveness and welfare (led by Dr. Rebecca Meagher at Dalhousie University, Canada, and funded by MITACS).

Selected peer reviewed publications and book chapters:

Lezana, L., Hernández-Soto, R., Díez-León, M., Ríos, M., Baquero, E., Galicia, D. 2022. The effect of early experiences in barn owl (Tyto alba) behaviour. Acquisition-expression time of neophobia and filial imprinting. Implications for management and conservation. Behavioural Processes 195: 104569.

Harrington, L., Díez-León, M., Gómez, A., Harrington, A., Macdonald, D., Maran, T., Põdra, M., Sugoto, R. 2021. American mink might pose a COVID threat. Frontiers in Ecology and the Environment 19: 266-267.

Polanco, A., Ahloy-Dallaire, J., Díez-León, M. 2021. Abnormal behavior. In: Sørensen, D.B., Gaskill, B. Animal-centric Care and Management - Enhancing Refinement in Biomedical Research”. Taylor and Francis, UK.

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