Life history traits and cancer prevalence in birds

Background and objectives: Cancer is a disease that affects nearly all multicellular life, including the broad and diverse taxa of Aves. While little is known about the factors that contribute to cancer risk across Aves, life history trade-offs may explain some of this variability in cancer prevalence. We predict birds with high investment in reproduction may have a higher likelihood of developing cancer. In this study, we tested whether life history traits are associated with cancer prevalence in 108 species of birds. Methodology: We obtained life history data from published databases and cancer data from 5,729 necropsies from 108 species of birds across 24 taxonomic orders from 25 different zoological facilities. We performed phylogenetically controlled regression analyses between adult body mass, lifespan, incubation length, clutch size, sexually dimorphic traits, and both neoplasia and malignancy prevalence. We also compared the neoplasia and malignancy prevalence of female and male birds. Results: Providing support for a life history trade-off between somatic maintenance and reproduction, we found a positive relationship between clutch size and cancer prevalence across Aves. There was no significant association with body mass, lifespan, incubation length, sexual dimorphism, and cancer. Conclusions and implications: Life history theory presents an important framework for understanding differences in cancer defenses across various species. These results suggest a trade-off between reproduction and somatic maintenance, where Aves with small clutch sizes get less cancer. Lay Summary Life history can help us understand cancer prevalence in birds. We examined potential life-history variables that may explain the variance in cancer prevalence across birds and found that species with larger clutch size, but not sexual dimorphism, larger weight, longer incubation length, or longer lifespan, have higher cancer prevalence.