2.1. Rumen Tissue
Deer rumen tissue samples were obtained during the annual culls in Phoenix Park, Dublin, between November 2019 and November 2021. Culling was performed by the Office of Public Works (OPW), the government body responsible for managing the deer herd and keeping it at a sustainable level. Phoenix Park is a walled park of 700 hectares, with no natural predators present and little chance to disperse considering that the park is surrounded by densely populated areas of Dublin city. Samples were obtained from a total of 101 deer, each within two hours of death. This included the 17 adult male deer (> 4 years old) utilized for this current study. For each rumen, four or five ventral sac samples of ~25cm2 were obtained and stored at -20oC until required. The papillae density measurement was obtained by counting the number of papillae (mean result of three counts) of a thoroughly washed 1 cm2 section of tissue. To determine average papillae length and width for each deer, six randomly selected papillae were measured by hand using a ruler and the mean value calculated. Details of the behaviour studies that produced the different feeding category for each animal and allowed for categorization into consistent or rare beggar groups have been published previously (Griffin et al., 2022a; Griffin et al., 2022b; McClaughlin et al., 2002). It is important to note that >80% of this population is ear-tagged at birth (Amin et al., 2021) and that deer are monitored over time, including their level of interactions with park visitors (Griffin et al., 2022a; Griffin et al., 2022b). Culling operations were carried out at random by professional stalkers, with no indication given by researchers of which individuals were to be shot. Instead, the professional stalkers received a culling plan with number of individuals to be shot split on sex and age class, with no indication of deer identity. Data on individually recognized deer (ear tags) and their tendency to accept food from humans (Griffin et al., 2022a; Griffin et al., 2022b) have been matched to the ear tag codes recorded from shot individuals from which we sampled rumen tissues.