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The European mink (Mustela lutreola) is a species of mustelid declared “in danger of extinction” in Spain, according to the Spanish Catalogue of Threatened Species (CEEA). It has less than 500 individuals in our country, with the center of the Foundation for Research in Ethology and Biodiversity (FIEB) located in Casarrubios del Monte (Toledo) being the captive breeding center in Spain with the largest number of specimens. One of the biggest problems encountered in the breeding project is the reproductive inefficiency of European mink males born in captivity, which leads to the need to investigate the cause of this problem and how to minimize or avoid it.

To this end, the entity, based on the reduction of the stress produced by captivity and the stimulation of the presence of other individuals of the same species in the same territory, has proposed a series of changes in management and facilities that help the sexual maturation of males and increase their reproductive efficiency.

The main objective of the project has been to promote the captive breeding of the European mink and to achieve an increase in the reproductive success of males.

The specific objectives were as follows:

• Keeping and breeding in captivity of specimens of the species.
• Increased reproductive success of males associated with the minimization of stress and the enhancement of their natural instincts.
• Increase the ethological data of the species by improving the video surveillance system.
• Awareness, training and dissemination of the problems suffered by this species.

• Feeding and care of 18 specimens of European mink in captivity.
• Training of 8 breeding pairs and monitoring through video surveillance.
• Feeding and care of the new specimens born in the 2019 breeding season.
• Bibliographic search of reproductive problems in males of European mink and other species of carnivores, especially mustelids, such as the black-footed polecat, to design a behavioral study and thus be able to help improve the management focused on the reproductive improvement of males. A total of 19 scientific articles were consulted.
• Behavioral pilot study on the causes of reproductive failure in males.
• Increasing the contribution of live prey and analysis of the appetite for these foods for the species.
• Adaptation of the facilities for the random administration of live prey for captive breeding specimens.
• Creation of a management protocol to increase male stimulation.
• Improvements to the video surveillance system, with the purchase and installation of 19 new cameras. In addition, the quality of the cameras and the angle of view were improved to reach the complete facilities and to be able to analyze the behavior of the animal constantly.
• Implementation of an application that allows access to the video surveillance system to the center’s staff remotely.
• Recording, evaluation and analysis of the videos of the pairs obtained during the breeding season.
• Recording, evaluation and analysis of videos of males obtained in different periods, to assess the different types of behavior (activity, sniffing and sniffing) according to the stage of the year and to be able to correlate them with reproductive success.
• Dissemination and awareness of the project through publications on social networks and on the entity’s website, in addition to attendance at the international congress “Medicine and conservation applied to Wildlife Recovery Centres” (Barcelona, 9 and 10 March 2019) and the colloquium on mustelids in Portugal (8 to 11 October 2019) to disseminate the results of the research.

In general, the actions carried out have served to increase the number of European mink individuals as well as to improve the reproductive knowledge of the species, thus contributing to an improvement of the ex situ conservation strategy (i.e. outside the natural habitat of the species) so that it has a positive impact in the medium term.

Thus, the project has culminated with the best data obtained to date: 8 pregnancies and 20 new offspring have been incorporated into the captive breeding program of the species. In addition, the animals’ hunting instinct has been enhanced through various environmental enrichment techniques and the introduction of live prey (quail, rat, mouse, crayfish and fish).

On the other hand, with respect to the ethological studies carried out on males in captivity to optimize reproduction in captivity, the results are not conclusive, so it is a challenge for the coming years.