It's Not the Size, but How You Orient It: An Investigation of Parasite Effects on the Secondary Sexual Characteristics of the European Bison (Bison Bonasus)

Abstract

Parasite-mediated sexual selection (PMSS) suggests that secondary sexual characteristics such as horns can function as both practical weapons for contest and as honest indicators of parasitic infection, but is woefully understudied in ungulates given how famous they are for their huge diversity of horns and tusks. Horn measures and parasite loads of European bison (Bison bonasus) in Białowieża Forest in Northeast were compared to determine if PMSS is operating in this polygynous male-contest species. While horn size (volume) was not significantly impacted by various parasites, male horn orientation was altered by the presence of parasites, in particular the nematodes Ashworthius sidemi and Fasciola hepatica, while only one female measurement was negatively related to parasite richness, suggesting that PMSS is a driving force in bison contest and reproduction. This underscores the need to carefully monitor the health of this vulnerable ungulate, especially against virulent and invasive new parasites.