Philippine eagle faces higher risk of extinction, study finds

MANILA, Philippines — The Philippine eagle has exceptionally low genetic diversity, making the critically endangered species fragile and more likely to face extinction when confronted by disease, environmental changes or other threats, scientists found in a study.

The study, led by Dr. Cynthia Saloma of the University of the Philippines Diliman College of Science’s National Institute of Molecular Biology and Biotechnology, found that Philippine eagles are highly similar to one another genetically, meaning they share nearly the same set of genes.

“The danger is that when there’s little variation, the species struggles to adapt to changes. For example, if a new disease appears or the environment shifts, most eagles would react the same way and have the same capacity to adapt — and if they’re vulnerable, the whole population could be wiped out,” the researchers said.

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“In short, low genetic diversity makes the Philippine Eagle fragile and more likely to face extinction when challenges arise,” they added.

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Genome study

The findings came from an analysis of the DNA of 35 Philippine eagles under the care of the Philippine Eagle Foundation in Davao City. The team used the samples to produce a draft genome for the species.

“A genome is a living organism’s complete set of genes,” the researchers said. “From the extracted DNA sequences, we were able to assemble a representative genome for the species.”

The team also includes researchers from the Philippine Genome Center, UP Los Baños, and Philippine Eagle Foundation.

The researchers said low genetic diversity also raises the risk of inbreeding, which occurs when closely related eagles mate because of small population size and fragmented habitats.

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Inbreeding makes harmful traits or genetic weaknesses more likely to appear in offspring and may lead to reduced fertility, weakened immune systems, and physical abnormalities that make survival more difficult, they said.

Small population

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The Philippine eagle (Pithecophaga jefferyi) is estimated to have fewer than 500 mature individuals left in the wild. More specific estimates put its population at around 392 breeding pairs, or about 784 individuals including immature birds.

Tracking the species precisely remains difficult because Philippine eagles are solitary apex predators that require vast forest territories.

The findings also suggest that the Philippine eagle population may have already been declining before widespread deforestation.

The researchers said one possible explanation is that long-term ecological changes, such as rising sea levels thousands of years ago, may have fragmented once-connected habitats in Mindanao and isolated eagle groups.

They said early human activities in the Philippines, including hunting or competition for prey, may also have placed pressure on the population.

Hypotheses, not certainties

The scientists clarified that these were hypotheses rather than certainties but said they could help explain why the decline appears to have begun before deforestation, which is often considered the main threat to the species.

“By applying a genomics-driven, genetically informed approach, our study offers a blueprint for safeguarding other threatened species across the archipelago, and demonstrates how modern DNA analysis and bioinformatics can be leveraged to strengthen biodiversity management,” the researchers said.

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The study, “Genomic analysis reveals recent population decline and exceptionally low genome-wide heterozygosity of the critically endangered Philippine eagle, Pithecophaga jefferyi (Aves: Accipitridae),” was published in BMC Genomics, a peer-reviewed, open-access journal that publishes research on genetics, genomics, and bioinformatics.