Wild Boar (Sus scrofa) – Western Eurasia

The decay process of animal carcasses is a highly complex succession driven by abiotic and biotic variables and their interactions. As an underexplored ecological recycling process, understanding carrion decomposition associated with pandemics such as African swine fever is important for predicting the rate and post-mortem interval (PMI) variation of wild animal carcasses to improve disease management.
To model PMIs of wild Boar, we deployed 73 wild Boar carcasses in four different forest habitat types throughout a year and monitored the decomposition process, carrion beetles and blow fly larval populations. The 601 single observations were split randomly into 501 training data and 100 validation data.
A linear additive mixed model for log-transformed PMI values using the training data identified the decay stage, day of year, ambient temperature during sampling, habitat and prevalence of Oiceoptoma thoracicum (Silphidae) as predictive variables for time since death, but neither the initial body mass nor if a fresh or previous frozen carcass was used. Using the validation data, this model showed a high predictive power for log-transformed PMI values (R2 = 0.80).
This study aimed at improving the methodology of estimating the PMI of wild Boar carcasses based on important abiotic and biotic environmental factors that can be easily assessed in the field. Using only a small set of predictors, including a conspicuous beetle species, allowed prediction of the mean, minimum and maximum PMI of wild Boar carcasses. The strong effects of a few surrogates on PMI in our model suggest that this model can easily be transferred to wider regions of Central Europe by retraining the model with data from a broader environmental space and can thus be instrumental in assessing timing of disease introduction in areas newly affected by emerging diseases such as African swine fever.

In a study conducted in 2018-2020, we tested the hypothesis that the wolf in Osogovo Mtn was selecting its prey opportunistically, with a preference for the most abundant prey (apostatic selection). To achieve this, scat analysis was performed simultaneously with prey density assessment through objective camera traps data, Random Encounter Model (REM) and selectivity analysis. The results showed that the wild Boar was the most preferred prey by the wolf, complemented by the domestic horse. The Roe deer had a smaller, close to insignificant share. The selectivity index also confirmed the wild Boar dominance in the wolf diet, which was consistent through the years and seasons. The active selection towards wild Boar was anti-apostatic in nature as the wild Boar densities were 10-times lower than those of the Roe deer. Our results differed from those obtained by a previous study in the same region in 2002–2003, where the Roe deer accounted for 71.9% of the wolf diet. This study also showed anti-apostatic selection towards smaller prey probably formed by the decrease of the wild Boar abundance in the past.