Roberta S. Wallace, DVM
Senior Staff Veterinarian, Milwaukee County Zoo
The Humboldt penguin is native to the coastal waters of Chile and Peru. While once reported to number in the hundreds of thousands, the current population number is estimated to be at about 40,000. It is classified by the IUCN red list as vulnerable, and is listed as CITES I. Major colonies include Punta San Juan in Peru, and in Chile, Isla Chañaral, Isla Pájaros, Isla Cachagua and our study site, lslote Pájaro Niño, near Algarrobo, Central Chile. This study site was chosen in part because of its accessibility. To provide protection from rough waters for a yacht club under development, a causeway that joined the island to the mainland was built in the late 1970’s. With the island now attached to the mainland, if is frequently referred to as ex-islote Pájaro Niño.
Our first visit to the island was in 1992 when we collected blood samples from adult penguins for hematology, plasma chemistry and plasma vitamin levels. Reference values for this species were available, but only referencing the captive population. There were no values from healthy free-ranging Humboldt Penguins to use for comparison to assess whether the values from the captive population differed from the wild population or whether any differences signified health problems with the captive population.
After discussions with our Chilean colleagues during this project, we realized that the natural ecology of Humboldt penguins in Chile was little studied. Short term studies at a few islands and occasional censuses after El Niño years had been done, but a long-term study of various aspects of the biology of free-ranging Humboldt Penguins in Chile were non-existent. So in 1994 we embarked on a project to study the life history of the Humboldt Penguin colony at Pájaro Niño. It was designed to be a project that extended over many years because 1) the lifespan of Humboldt Penguins can be over 20 years, 2) Humboldt Penguins don’t reach sexual maturity until 4-5 years of age, 3) annual variation in climatic and oceanographic factors can severely affect breeding seasons and make extrapolation from data collected over 1-2 seasons unreliable.
Initial goals of the project were to: determine nest-site fidelity and nest type preference; determine mate fidelity; determine reproductive success; disease surveillance; develop a method for gender determination by DNA analysis and compare these results with morphometric data; and determine threats to the population.
We identified three main study areas on the island, and within each area we established a grid system consisting of contiguous, uniquely identified 10 X 10m grids. Nests located within each grid were given a unique number corresponding to the grids. Nest contents (number of adult birds, chicks and eggs) were recorded, adult birds were weighed and individually identified with transponder chips or flipper bands, and blood was collected for a variety of analyses. From 1994-2000 the nests were monitored monthly and then intermittently during the breeding seasons from 2001-2008. Semi-monthly monitoring occurred from 2009-2012.
Between 1994 and 2004, nearly 1400 penguins, including 294 chicks, were individually marked either with wing bands or microchips. Re-sightings of nesting birds have occurred up to 10 years after banding. Intense monitoring of the island to look for marked birds has not occurred since 2004.
In 1998, members of our research team were invited to participate in a Population and Habitat Viability Assessment (PHVA) sponsored by the IUCN and held in Olmué, Chile. The purpose of a PHVA is to assess the long-term sustainability of populations of a given species in the wild. At this PHVA, Humboldt Penguin and other penguin (Spheniscid) experts from around the globe attended by invitation. Our data provided information for the analysis, yet it was apparent that little information existed for Humboldt penguins across their range in Chile. The final assessment based on the knowledge at that time was grim: It is very likely the Humboldt Penguin will be extinct in the wild within the next 50-100 years.
Research needs were identified to help fill the gaps in knowledge so that more accurate population analyses could be performed in the future. Areas needing research included performing routine censuses of the Chilean Humboldt Penguin population, studying dispersal from the natal island for breeding, and determining threats from introduced species. Based the improved reproductive success of Humboldt Penguins utilizing artificial nests in Peru, design and installation of artificial nests at strategic locations in Chile was considered.
One of the main deficits in knowledge was that the size of the Humboldt Penguin population in Chile was unknown, with estimates varying widely. Censuses utilizing different methodologies had been done at individual colonies sporadically in previous years. Standard methods were developed at the PHVA. From 2000-2008, utilizing these methods, the Milwaukee County Zoo along with Zoological Society of Milwaukee and the penguin TAG and funded annual censuses to survey all the major colonies of roosting penguins along the Chilean coast from Tarapacá in the north, south to Islote Pájaro Niño. The census took place in February when penguins are on land to moult. Two passes approximately 18 days apart were made in an attempt to include as many birds as possible. The census shows a stable population of approximately 35,000-37,000 birds across several years. This is most likely an underestimate of the total population since small colonies may have been missed, and birds in inaccessible sea caves would not have been counted. However, these numbers do not represent the sub-population of reproductively active birds, which is important for assessing the sustainability of a population. Methods to accurately assess the size of this sub-population need to be developed and funds secured for performing the census.
Data collected over the course of this study have produced a wealth of information. Natural hybridization between free-ranging Magellanic and Humboldt Penguins resulting in live hybrid individuals was observed and reported. Effects of climatic factors on the breeding colony were recorded. The activity of introduced rat species was documented. Our most recent project was the placement of artificial burrows around the island. Artificial nests have been used successfully at Punta San Juan, Perú. Our hope was that the penguins might find these burrows more attractive than some of the less desirable natural nesting sites. Additionally, since the artificial nests are made of heavy duty plastic we hoped that they would be less likely to collapse in the rain or be trampled by other heavy sea birds such as pelicans. If a nest is collapsed or trampled, young chicks are frequently killed and the adults will usually abandon any eggs.
Threats to the general Humboldt Penguin population are many and varied: El Niño with its effects on rainfall and availability of food near nesting areas, introduced predators such as cats, dogs, rats, fox, and goats, natural predators such as sea lions, and people. Threats from people include unregulated ecotourism to sensitive islands, entanglements in fishing nets, outright poaching to use penguin meat as bait, and meat and eggs for human consumption, and development without regard for the effect of such development on nearby penguin colonies.
Unfortunately, both the general number of penguins and the number of nests on our study island has been declining over the years but the cause of this decline is unknown. We hope that it simply represents a shift of the penguins to other islands in response to the human population growth of the area and attendant increase in human activity around the island, rather than reflect a decrease in the overall Humboldt Penguin population in Central Chile.
Further research is needed to fully understand the biology of the Humboldt Penguin in central Chile. Continued investigations into juvenile dispersal and island fidelity (by visiting other islands in search of marked birds), and overall breeding success are warranted. Potential areas of new research include 1) radiotracking of adult and juvenile penguins to determine their feeding and travel zones, and 2) assessing the health status of the penguin population by toxicological and serologic survey. Finally, periodic censuses of the population of breeding Humboldt Penguins in Chile are vital for assessing the overall sustainability of the population.
For a complete list of publications related to this project, please visit the Zoological Society website at: www.zoosociety.org/MultiMedia/Stories/PenguinResearch.php