For the Future of the Humboldt Penguin (Spheniscus humboldti)
Tama Zoological Park
Tatsuya Yamamoto
The Eccentric “Penguin”
Penguins are classified into six genera and 18 species, and are widely distributed in various environments in the Southern Hemisphere (and some in the Northern Hemisphere) from Antarctica to the Galapagos Islands, just below the equator. Primitive penguins appeared in the waters around New Zealand over 60 million years ago, expanding their range along currents flowing from Antarctica. It is thought that penguins evolved from a common ancestor with its closely related order Procellariiformes, but its origin remains unclear.
Penguins have characteristics that deviate from flying birds and are a group that can be said to be “eccentric” among birds. At first glance, it may be hard to say that the penguin is a bird, with its characteristic body structure that has evolved by adapting to arctic regions and underwater life, such as its heavy and round body with stored fat, small and hard winds called flippers that are like boat oars, and short legs that support a heavy body and that look unsuited for walking. Birds have heightened their ability to fly in their evolution, whereas penguins have stopped flying, though the appearance of the latter in water is as though they were flying in water. The penguin is a bird that has changed their course of flight from the air to the water in its search for abundant food.
Japan, a penguin breeding powerhouse
The penguin is a very familiar bird to us Japanese people, who have seen them at least once in zoos and aquariums. Currently, over 4,000 penguins from 11 species across five genera are kept captive in domestic zoos and aquariums, which consists of a third of the penguins bred in zoos and aquariums worldwide. There is no other country worldwide that has as many penguins. New breeding methods are being researched for each species, and in this regard, Japan, which has some of the most advanced penguin breeding methods worldwide, can be said to be a penguin breeding powerhouse.
Here, I will introduce the conservation efforts being conducted in zoos and aquariums for the Humboldt penguin (Fig.1), which is the most bred species in Japan and for which I am overseeing pedigree management.
Current status of Humboldt penguins in the wild
The Humboldt penguin is distributed along the Pacific coast from Peru to Chile in South America, and its current population is estimated to be around 40,000 individuals. The species is listed in Appendix I of the Washington Convention and its international trade is restricted, and in the IUCN Red List, it is at risk of extinction, being classified as “Vulnerable”. Furthermore, although its habitats are protected by domestic law in both Peru and Chile, such measures remain insufficient. A particularly serious problem has been the destruction of breeding grounds. Many of their nesting sites have been lost due to the mining of fossilized soil layers for guano, which is the accumulation of seabirds (including penguin droppings and carcasses), for its use as fertilizer for agricultural products. Damage due to El Niño phenomena and impacts from fishing industries have also become serious issues.
Fig.1 Humboldt penguin
Conservation promoted by zoos and aquariums
What kind of conservation is conducted in zoos and aquariums in the first place? Currently, many of the animals kept in zoos and aquariums have the pedigrees of their populations managed using pedigree registration and population management software that are overseen by pedigree registration managers who are selected from each zoo. Each manager creates / promotes a breeding plan based on the data analysis results and aims to maintain the genetic diversity of captive animals as close possible to that of animals in the wild, advancing ex-situ conservation as an insurance population of the endangered wild animals. The formation of such genetically sound captive populations as well as the knowledge and techniques that were obtained while managing the populations’ captivity are also useful for in-situ conservation, greatly contributing to the reintroduction of species that were once driven to extinction, such as the Japanese crested ibis and the oriental stork.
Captivity and conservation of Humboldt penguins
There is a very long history of Humboldt penguin captivity, with the first living penguins introduced to Japan in 1915, when their captivity began in Japan. Unfortunately, all the individuals died during the Second World War, but new individuals were introduced after the war, and captivity was resumed. Pedigree registration ledgers show all individuals, numbering about 5,500, that were kept in captivity from the post-war period to the present day. The number of captive individuals in Japan has increased from 971 individuals in 1993, when pedigree registration was initiated, to 1,851 individuals across 80 zoos to the present day (end of 2016).
The Humboldt penguin is one of the few species that faces extinction in the wild and simultaneously is breeding well in captivity and increasing its number of individuals. The resemblance of the Japanese climate to that of Peru and Chile, where the penguins’ habitats are located, is also thought to contribute to the increase in the number of individuals. However, simply increasing the number of individuals does not lead to conservation. Promoting planned breeding and maintaining genetic diversity requires the exchange and transfer of individuals and prevention of incest. However, two major problems have emerged during the management of Humboldt penguin populations.
The first is the risk of death following the transfer of an individual. This species has an extremely high mortality rate after transfer, with up to 25% of individuals dying within a year of transfer in some cases. The reason for this was thought to be the large impact of stress from changes in the environment, but there are hardly any such cases with the cape penguin and Magellanic penguin, which belong to the same genus as the Humboldt penguin. Meanwhile, it has been observed in this species that individuals that are isolated due to reasons such as treatment often become less energetic and lost their appetite due to stresses from changes in their environment, with their condition becoming further exacerbated. Individuals that are separated from their pair have particularly noticeable symptoms, so much so that the individual will need to be isolated with its partner, even if the latter is healthy, during treatment. Follow-up surveys of transferred individuals after taking this fact into consideration showed that there was a low mortality rate among transferred individuals aged six years or younger, prior to pair formation. Given this, the transfer of young individuals prior to pair formation with high adaptability was promoted from 2014 onwards, and the result was that deaths within one year of transfer disappeared, enabling the transfer of individuals with the aim of more effective and reliable breeding.
The second is the problem of the origin of the founding individual of a population. The origin of some of the founding individuals that serve as the basis of the current population is unknown, therefore, there is a possibility that the entire captive population may have a considerably lower genetic diversity than that of wild populations. Therefore, blood samples were collected from about 1,800 individual Humboldt penguins that were kept across Japan, and their genetic diversity was analyzed using DNA testing and compared with those of wild populations. Results showed that when the individuals in Japan were considered as a single population, it retained the same genetic diversity as that of the wild population. Meanwhile, it was also shown that incest had been progressing in each facility, and systematically transferring individuals will be a future challenge in order to maintain better conditions.
International cooperation and the future of Humboldt penguins
Due to various problems, there is insufficient effort made for the conservation of Humboldt penguins in their original habitat. Under such circumstances, the Chilean National Zoo in Chile has focused on conservation efforts that are exclusively possible given their proximity to the penguins’ habitats, such as collecting nests with a high risk of submersion and hatching them using an incubator, and they are proceeding with efforts for the reintroduction of penguins into the wild. This zoo has a cooperative relationship with Japanese zoos and aquariums, and the latter has provided information to the former on artificial hatching and brooding techniques, research techniques for genetic diversity analysis, and breeding and populations. In this way, breeding techniques from Japan, a location far removed from the penguins’ original habitat, are being utilized in zoos that are protecting the species in local habitats. We hope that the continuation of such efforts in the future will provide a bright future for the Humboldt penguin.
Fig.2 An exhibit that imitates the original habitat of the Humboldt Penguin (Tokyo Sea Life Park)