The Philippine eagle, the country’s national bird, may have been living among other prehistoric animals like whales, marine turtles and crocodiles.
The evidence, according to a group of Filipino, German and Russian scientists, were discovered in the eagles themselves—the mites, the prehistoric feather mites that coevolved with the revered king of all birds of prey in the Philippines.
Jayson Ibañez, the director for Research and Conservation of the Philippine Eagle Foundation (PEF), said the recent discovery of feather mites on two captive Philippine raptors—including three specimens of the world’s largest bird of prey—strengthens the theory that the Philippine eagle is indeed the only one of its kind.
This conclusion was supported by a peer-reviewed paper published in the International Journal for Parasitology: Parasites and Wildlife (IJP-PAW) sponsored by the Australian Society for Parasitology.
The study reports the discovery of three species of feather mites found on three captive Philippine eagles and the Mindanao hawk eager at the Philippine Eagle Center in Davao City.
New to science
The feather mites, according to the scientists, are entirely new to science.
The journal publishes the results of original research on parasites of all wildlife, invertebrate and vertebrate.
It includes freeranging, wild populations, as well as captive wildlife, semidomesticated species and farmed populations of recently domesticated or wild-captured species.
The paper, which was accepted on March 16, was cowritten by Ibanez, Sergey V. Mironov, Boris D. Efeykin, Anna Mae T. Sumaya and Oleg O. Tolstenkov.
It was a result of the collaboration of the researchers’ various institutions namely the Philippine Eagle Foundation, University of the Philippines in Mindanao; the Zoological Institute, Russian Academy of Sciences; A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences; Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences; and Johann Wolfgang Goethe-University, Frankfurt; Buchmann Institute for Molecular Life Sciences and Institute of Biophysical Chemistry.
The feather mites, the paper said, coevolved with the eagles, which means they are the ancient ectoparasites, or external parasites, of the first Philippine eagle population.
The third and last feather mite species, the Pseudogabucinia nisaeti sp. n. (Kramerellidae), was from the Mindanao hawk eagle.
The Philippine eagle and the Mindanao hawk eagle are the top 2 most endangered birds in the Philippines.
The International Union for the Conservation of Nature (IUCN) lists the Philippine eagle as “critically endangered” species, while the Mindanao hawk eagle is listed as an “endangered” species.
Both birds are found only in the Philippines.
The feather mites of the Philippine eagles were found to be closely related to the mites found among several eagles of the family Circaetinae or the Serpent-eagle family.
According to the paper, such similarity in ectoparasites between the Philippine eagle and other serpent eagles further support the genetic relatedness between these two eagle groups.
“This means that the Philippine eagle is the Goliath kin of the world’s serpent or snake eagles,” the paper said.
Previously, eagles were thought to be relatives of the Harpy group of eagles, a bird family which contains the largest eagles of the world, such as the Harpy Eagle and Crested Eagle, until a DNA study by researchers from the University of Michigan in 2005, showed that the two groups are similar in their general appearances only because they feed on the same kind of animals (forest mammals) and that they live in the same kind of habitat (tropical forests).
Scientists call this phenomenon “convergent evolution.”
No chewing mites
According to the report, most of the bird species host several groups of ectosymbionts, or organisms living together on the surface, including obligatory feather mites and chewing lice species.
However, upon examination of the captive Philippine eagles, revealed the existence of the feather-mites species and no chewing lice.
“Although we sampled only three individuals of the great Philippine eagles, the fact that we found no chewing lice suggests that these insects are much more susceptible to the antiparasite treatment, and endemic lice will likely not survive on captive birds in the Philippine Eagle Center. The loss of chewing lice is not unusual for small populations of endangered species of birds conserved and bred in captivity,” the paper pointed out.
Based on the results of the examination, the feather mites are capable of surviving annual antiparasitic treatments for a longtime, citing one of the examined birds named “Thor,” which was captured in the wild in 1974, and at the day of examination in 2016 hosted a viable population of the mite, H. philippinensis.
“This fact, assuming this population of mites is endemic, suggests that these ectosymbionts have been able to survive 43 years in captivity,” the paper added.
Part of biodiversity
Asked about the significance of the discovery of the mites in the captive Philippine eagles, Tolstenkov of the Russian-based Severtsov Institute of Ecology and Evolution told the BusinessMirror in an e-mailed reply to a question that parasites are a significant part of biodiversity, plays important role in the ecosystem and have evolved together with their host species for millions of years.
Tolstenkov came to the Philippines in 2016 and joined the PEF staff in the regular physical checkup of the eagles, during which feather mite specimens were collected and preserved from the Philippine eagle and the Mindanao hawk eagle.
“They both host and parasites are coadapted, the race of reciprocal adaptations of parasites and hosts was called the red queen race. This process is going so far for some permanent parasites like feather mites that they cannot survive without their host. They cannot live on any other bird species. So, when species of host becomes endangered the parasites may disappear forever, too,” he explained.
According to Tolstenkov, some critically endangered species of birds were conserved and reintroduced due to the efforts of propagation centers and conservation enthusiasts, but they learned of same cases when parasites of this species were lost because of the need to treat the core captive population by antiparasitic drugs.
“The Californian condor can serve as an example of bird species which lost all their native parasites. However, we can lose not only the biodiversity of parasites. [It is] important to understand some exciting questions in the field of parasitology [not only] the evolution of parasites and host-parasite relations, but the very important information that helps to understand their host, too.
“Millions of years of coevolution made parasites the trackers of the host’s evolution history. We can get a lot of useful information of their host by analyzing, for example, the phylogeny of parasites and this information can be essential for the host conservation,” he explained.
Ibañez, who took up biology at the University of the Philippines-Los Baños and Zoology at the Ateneo de Davao University, for his part, said the unique mites on Philippine eagles indicate that it is a very ancient species.
“The fact that its [Philippine eagles] feathers became the habitat of at least two very unique mites suggests that the Philippine eagles have lived for so very long, perhaps way longer than the human species. The evolution of new species require very long years,” Ibañez, who earned his doctorate degree in Natural Resource Management, explained.
“Second, if the eagle [goes] extinct, so too will the mites. So you have a case here of what science calls coevolution: the life history of two species—in this case, the predator and its ectoparasite—are so entwined that the extinction of the host would mean the extinction of the other,” Ibañez said.
Last, Ibañez said a highly unique species like the Philippine eagle giving rise to another highly unique species, this time its mites, show the wonder of creation where uniqueness begets uniqueness.
“It underscores how miraculously and mysterious life really is,” he said.
No serious threat
According to Ibañez, the mites discovered on the captured Philippine raptors pose no serious threat.
“As long as the eagle is healthy and is able to preen and groom itself the effect of the mites would be benign. But if an eagle becomes sickly, and can no longer groom itself, then mites can overpopulate and eventually affect the bird,” he said.
“Together with the effect of sickness, individuals might perish. But this process is also important to make sure that the sickly and less fit animals are culled out of the population. So ectoparasites play an important role [in] making sure that only healthy birds survive in the wild. So survival of the fittest,” he explained.
The Philippine eagle is the largest bird of prey in the world. There are only around 400 to 500 breeding pairs of this bird species left in the wild.
Highly territorial, this bird of prey is the apex predator, within its range or territory, which covers a radius of 7 kilometers to 13 kilometers of lush forests and a healthy ecosystem, provides a life-support system for its favorite preys like monkeys, snakes, monitor lizards and flying lemurs.
In addition, the study, Ibañez said, showed that even after decades in captivity, endangered birds can maintain the native species of parasites that should encourage scientists around the globe to check the species of birds in the zoo collections and propagation centers for the feather mites.
Tolstenkov said feather mites are endosymbionts than parasites and do not have a major negative effect on the host’s fitness.
“They feed mostly on oil secretes that cover the feathers of birds. They do not damage the skin or feathers. However, this is relevant to native feather mites in the natural host species only,” Tolstenkov pointed out.
He pointed out that millions of years of coadaptation caused host-endosymbiont equilibrium when none of the participants in relationship lose a lot.
By some reason, for example for birds in captivity or domestic birds when alien parasites switch to the nonnatural host, they can cause troubles.
He cited an instance in Brazil when the feather mite species from the local passerine bird species became a severe problem for the chicken farms causing the death of domestic birds.
The species found on the Philippine eagles, however, do not pose serious threats to the eagles, as they are native to the eagles or natural symbionts.
Contribution to evolutionary history
Meanwhile, the spread in other species can be controlled or prevented, as they can be treated as most birds in captivity are treated annually by antiparasitic powder.
He, however, pointed out that feather mites are not a major problem for the health of their hosts.
The findings on the Philippine eagles, he said, allowed the scientists to contribute to the evolutionary history of both feather mites and the host.
Tolstenkov said feather mites are present on all wild eagles naturally as their endosymbionts.
“The ancestor of Philippine eagles feather mites came with the ancestors of Philippine eagles which are not really eagles as mentioned by Jayson [Ibañez] several million years ago when this species arrived on the Philippines. Later both the hosts and endosymbionts evolved into the present species on the islands,” he said.