Pilot project: a theoretical framework for the control of fertility in a population sample of red deer from El Monte de El Pardo (Spain)

Context. The present study aims to promote fertility control as a non-lethal means of managing wild animal populations, specifically red deer (Cervus elaphus) in a region of Spain. The control of fertility in cervids through the use of long-acting contraceptives or other sterilization approaches has been advocated as a reasonable tool in the face of the challenges posed by overpopulation, especially in areas close to urban spaces. Among the contraceptive methods known to date, immunocontraception appears to be the most effective and favorable methodology with respect to the welfare of the animals.Aims: This action plan proposes the use of a single dose injectable immunocontraceptive vaccine (GonaConTM Immunocontraceptive Vaccine) in red deer that inhabit Monte de El Pardo, accompanied by a follow-up study to determine: (1) determine the effectiveness of the GonaConTM vaccine over 3 years in the prevention of pregnancy, (2) determine the possible secondary effects (contraindications), (3) identify any weaknesses and drawbacks of the treatment and (4) propose improvements and future perspectives. As far as we know, it would be the first to establish theoretical bases for the first use of this vaccine in wild red deer in Spain.Methods: The vaccine will be injected into a total of 200 wild female reed deer of reproductive age in Monte de El Pardo. The control group will consist of 50 females who will not be vaccinated but will be evaluated in the same way. The treated individuals in the study will be marked and identified, and follow-up will be carried out for a period of 3 years. The effectiveness of GonaConTM will be quantified by measuring physiological and ethological parameters (behavioral observations). These data will be compared with the results of the control group.Key results. We expect to achieve an average inhibition of reproductive production of more than 80% over the three year period, and it is hoped that in the first year the effectiveness will reach 90-100%, without notable detrimental effects on the physiology or behavior of the individuals in relation to the control group. Similarly, no significant differences are expected between the results from the non-reproductive behavior of the treated deer and that of the control group, in individuals between the start of vaccination and 12 months later (Quy et al. 2014), in the subsequent sampling throughout the 3 years of the study. It is expected that the deer treated with GonaConTM will exhibit a secretion response of sufficient anti-GnRH antibodies to achieve an inhibition in their reproductive behavior and physiology and, therefore, in their fertility (of at least 80% average effectiveness over the 3 years). Implications. The development of this method of population control is essential in urban and suburban areas, where lethal control, by poisoning or capture compromises animal welfare, in addition to the potential risk for the human population. It is expected that stability in the number of deer present in Monte de El Pardo will reduce potential threats that derive directly from collisions with vehicles and transmission of diseases. We suggest that a greater effort to develop less invasive and non-lethal population control modalities is justifiable.