SE Valley Times

In one of the largest studies on cancer susceptibility across bird species, researchers at Arizona State University have identified a relationship between reproductive rates and cancer susceptibility. The study analyzed data from over 5,700 bird necropsies across 108 species and found that birds laying more eggs per clutch tend to have higher cancer rates.

The findings illuminate evolutionary trade-offs between reproduction and survival in birds, with potential implications for health and disease research across various species. By examining energy allocation strategies affecting cancer development in birds, researchers aim to gain insights relevant to human cancers. This understanding could lead to new strategies for preventing and treating cancer.

"Birds are exceptional for many reasons but one of them is the fact that birds get less cancer than mammals, and we don’t know why," says Carlo Maley, corresponding author of the study. "We’d like to understand how birds avoid getting cancer and see if we can use that to help prevent cancer in humans."

Maley directs the Arizona Cancer and Evolution Center, is a researcher with the Biodesign Center for Biocomputing, Security and Society, and is a professor with the School of Life Sciences at ASU.

The group’s findings appear in the Oxford Academic journal Evolution, Medicine, and Public Health.

Conducted by an interdisciplinary team from Arizona State University, the University of California Santa Barbara, North Carolina State University, and several European universities, the study brought together expertise in evolutionary biology, veterinary medicine, and cancer research.

While cancer is common among multicellular organisms, its risk factors in birds have not been as extensively studied as in mammals. Birds allocate limited energy resources to various functions; more energy devoted to reproduction leaves less available for maintaining health, potentially increasing disease risks including cancer.

Life history theory examines how evolutionary pressures shape trade-offs between life functions. In birds with high reproductive rates investing heavily in offspring raising may leave less energy for DNA repair making them more susceptible to cancer—a pattern possibly applicable to mammals too.

"It is interesting that depending on the reproductive trait that we focus on, the trade-off between reproduction and bodily maintenance is not always clear," says co-first author Stefania Kapsetaki. "For example, investing in a trait linked to increased reproduction does not always mean less investment in a trait linked with bodily maintenance."

Contrary to expectations regarding body size or lifespan correlating with cancer risk—highlighting Peto's paradox—the study found no significant correlation between these factors in birds. Previous research by Maley explored how large mammals developed sophisticated strategies of cancer suppression which may offer clues against human cancers.

The current study notes that larger clutch sizes correlate with higher malignant cancers suggesting a trade-off between reproduction and defense mechanisms against cancers. Other factors like incubation length or sex showed no significant association with cancer prevalence.

Adding evidence linking reproductive investment with disease risk in animals advanced statistical techniques helped account for evolutionary relationships among bird species revealing patterns likely shaped by natural selection rather than chance.

Data was derived from necropsies performed at 25 zoological institutions over 25 years while life history information came from existing scientific databases on bird biology emphasizing differences from wild populations might exist under human care conditions

Future investigations may explore molecular mechanisms underlying clutch size-cancer risk relationships ecological influences on wild populations' susceptibilities—and low-cancer rate species' prevention methods potentially impacting conservation efforts considering screening needs particularly for larger clutch-size species benefiting endangered population health management

Overall demonstrating evolutionary thinking's value applied towards studying different species managing risks uncovering prevention/treatment strategies beneficially spanning both human/veterinary medical fields