Projektopgave, Cathrine Dyhr Sauer (KU-LIFE), Mikkel Stelvig

Aim of project
The EEP musk ox population will benefit form import of new founders to avoid future increase in the inbreeding level of the population and to maintain the high level of genetic diversity currently present in the population. The aim of this project is to compare the two import strategies ([male]: import of male founders only vs. [mix] : import of male and female founders) to see which of the two are most beneficial to the population's levels of inbreeding and genetic diversity, as well as population size.
The project will be a review of scientific literature published on the subject as well as computer simulations.

Discussion
The graphic results of population size for both strategies show an unexpected result. It seems that the decline in population size is merely displaced in a parallel manner for every time founders are added instead of increasing h when new genetic material is added to the population. This could be due to the fact that an increase in genetic diversity only makes a minor difference because the level of genetic diversity in the current population is already high (0,895). However, since the negative slope of the population size seem to persist in spite of improved genetics, it might imply that other factors limit the growth rate.
As mentioned previously, the main threats to captive populations are genetic and demographic factors. If the cause of the negative growth rate is not genetic, it must be demographic. Negative growth rate occurs when the number of deaths exceeds the number of births in a population.
Therefore, to increase the population size (or at least keep it stable) efforts should be made to reduce neonatal mortality, maximise the number of pregnancies and generally intensify management during oestrus, pregnancy, birth and weaning periods. Identifying and minimising causes of adult mortality will also improve the growth rate.
The above mentioned demographic factors can easily overshadow the positive effects of increased genetic variation, as it seems to be the case for this population.
Another reason why the modelled growth rate is negative in spite improved genetic diversity could be, that the growth rate value (l)is based on calculations from studbook data. The probability of breeding is calculated for each age class, based on reproductive recordings in the studbook. However, the studbook does not take the geographic location of individuals into considerations. Hence, if an individual has not reproduced due to the lack of a suitable mating partner, the probability of breeding will be reduced even though it does not reflect the true probability e.g., in Kolmirden Djurpark (Sweden) the current population consists of 5 males.
A third thing that could be affecting the modelled growth rate negatively is the fact that the inbreeding depression may have been estimated to high. This is due to the fact that some degree of inbreeding in the population is probably already reflected in the probability of breeding i.e., producing viable offspring.
Whether strategy [male] or strategy [mix] should be used for future imports of founders, depends on the main management goal for the population. Strategy [mix] is the least risky strategy. It increases the level of genetic diversity the most along with resulting in the lowest level of inbreeding. Strategy [male] has a more unpredictable outcome, yet the mean population size is higher than for strategy [mix] in spite of the fact that the growth rate is lower (h = 0,9971 for strategy [male]; 1 = 0,998 1 for strategy [mix]).

Conclusion
If the EEP population is to survive over the next 100 years, founders must be added. The strategy of importing of male founders only should be used, if the main goal is to maximise population size. However, the mixed import strategy fulfils the management goals best, if these are focusing on genetic aspects.