Heterogeneity in host compatibility is one of the main hypotheses proposed to explain uneven resistance to parasites and uneven parasite load between hosts. It suggests that differences between hosts modulate their predispositions as suitable environments for their potential parasites. Interesting studies of antiparasitic behavior have reported the existence of behavioral traits that are capable of removing foreign particles and of reducing the success of parasitic infections. These traits favor host neatness, although little is known about the heterogeneity of neatness. We used a standardized pseudoinfection with pseudoectoparasites (PEPs) to test the effects of sex, age, and season on the loss of PEPs by hosts as a means of exploring the factors determining neatness in the Iberian ibex Capra pyrenaica. Behavioral observations were also performed to analyze investment in antiparasitic behavior in terms of sex, age, and season. The life span of PEPs peaked in the period December-January, decreased with host age, and was longer in females than in males. Investment in antiparasitic behavior is also associated with both sex and age and season but in a different pattern with interactions between such factors. Our results disagree with the hypothesis that small-bodied animals should be less compatible to carry contact-transmitted particles, such as ectoparasites, in comparison with larger animals. This preexisting hypothesis is thus an inadequate way of predicting host neatness. Consequently, our experiment underlines the importance that nonimmunological traits play in determining heterogeneity in host compatibility to contact-transmitted foreign bodies and helps improve understanding of neatness and of host-parasite systems.