Galapagos Penguin

Distribution / General:

The Galapagos Penguin is the smallest member of the genus Spheniscus, which also includes the closely related Humboldt Penguin, and the Magellanic and African Penguins. There is little doubt that it diverged from the Humboldt Penguin, yet the timing of this event is controversial. Based on studies of mitochondrial DNA and the RAG1 gene in various penguin species, the Humboldt and Galapagos Penguins were estimated to have diverged some 4 Million years ago (Baker et al. 2006. Proc. R. Soc. B. 273, p.11-17), whilst another study considering 6 different genetic loci places this point about 500,000 to 800,000 years ago (Akst et al. 2002. Conserv. Genet. 3, p.375-383). Due to the small and frequently fluctuating population it is difficult to determine the point of divergence accurately. It is thought that the small size of the Galapagos Penguin in comparison to other Spheniscids is an adaptation to the higher temperatures, especially on land, in its tropical range. The small size and less dense plumage allow better heat dissipation.

The Galapagos Penguin owes its existence on the Galapagos Islands to the localized upwelling of the cold nutrient-rich Equatorial Undercurrent. Perturbations in the upwelling system as observed during El Nino Southern Oscillation (ENSO) events can lead to high adult mortality and total breeding failure. Given current global warming trends and increased frequencies of ENSO events in recent years, the Galapagos Penguin is probably on the brink of extinction. It is currently officially characterized as endangered.

Colonies are generally small and are mainly found on Fernandina and Isabela Islands, with tiny populations on Floreana, Bartolome and Santiago.

The population size was estimated at about 1500 individuals in 2004 and 2008 (Jiminez-Uzcategui and Vargas 2008. CDF Peng. & Cormorant Survey).

Feeding:

Galapagos Penguins generally forage close to the coastline around their colonies. They tend to depart from their colonies at 5:00-7:00 and return again at 16:00-18:30. Between these times, they may spend short periods on land. Overnight foraging trips are not generally observed (but cannot be excluded), although the penguins may not return to land at their breeding colonies.

Swimming Galapagos Penguins	Entering water	Swimming Galapagos Penguins

Diet

The main prey items appear to be thin schooling fish of a length of 1-15 cm, largely around 10 cm long. Sardines (Sardinox sagax), Anchovy (Engraulis sp.), Mullet (Mugil sp.) and Piquitangas (Lile stolifera) are reported prey species. Based on observations of Galapagos Penguins foraging with Audubon Shearwaters, which feed on crustaceans, it is assumed that these may also form part of the diet of the penguins, although this has not been directly proven. Fish are normally swallowed whole, yet penguins have been rarely observed manipulating larger prey items at the surface.

Foraging Behaviour

Galapagos Penguins are not generally seen porpoising as they leave shore, possibly due to the scarcity of marine predators close to the colonies. However, this behaviour may be observed when they are travelling towards feeding aggregations. Generally underwater swimming involves the movement of the flippers through an arc of about 130'. During the upstroke the fronts of the flippers are tilted slightly upward to reduce resistance, whilst they are tilted downwards during the downstroke to generate maximum thrust forwards. During surface swimming, the flippers are only moved through a small angle and remain largely submerged.

Low water temperatures (below about 23'C) at Galapagos are associated with phases of high marine productivity. Accordingly, during such phases, penguins can be observed in large groups of more than 20 birds, occasionally more than 100. When temperatures are higher, birds are often observed foraging in pairs, scanning the area for small groups of fish. During periods of high productivity, multi-species feeding aggregations may be observed as little as a few meters from the coast. These aggregations, where many penguins may be present, form when large schools of small fish are present.

Multispecies feeding aggregations have been studied in detail at Galapagos (Mills 1998. Condor 100, p.277-285). Most occurred less than 150 meters off shore, with about 45% within 50 m. Galapagos Penguins, together with Brown Pelicans and Brown Noddies were most commonly associated with aggregations close to shore. Penguins tended to dive under the school of fish, picking off fish at the bottom of the school or feeding on the side of the school as they rose to the surface. This behaviour actually appears to fulfil a kind of shepherding role, since aggregations fed on by penguins were longer-lived (often many hours) than those fed on by plunge-divers, which tend to disperse fish.

Diving behaviour was studied in two non-breeding male penguin using attached time-depth recorders (Mills 2000. Mar. Ornithol. 28, p.75-79). Travelling and foraging dives were not distinguished, since diving was extremely shallow and no significant transit phase was evident. Mean dive depths of 4 and 2 m, and durations of 25 and 9 sec, were measured for the birds at Fernandina and Bartolome, respectively. Mean distances offshore were 36 and 60 m, respectively, with maxima of only 100 and 300 m observed. Diving was almost continuous although slightly reduced in frequency around dusk and dawn, when light levels are poorer. At Fernandina, penguins were feeding on Sardines, whilst at Bartolome smaller groups of unidentified fish were being preyed on, often in extremely shallow water. The dive record from the Fernandina penguin showed periods of intense diving to relatively defined depth ranges. Whilst these were not necessarily benthic dives, they presumably were aimed at aggregations of fish at these particular depths. A maximum dive depth of 32 m and duration of over 3 min was reported, showing that Galapagos Penguins generally don't approach their physiological limits when diving.

A more extensive study, using GPS and dive loggers to monitor diving behaviour of male and female birds provisioning chicks, was performed in 2004 and 2005 at 3 nesting sites on south-western Isabela (Steinfurth et al. 2008. Endang. Species Res. 4, p.105-112). The penguins moved up to 23.5 km (mean 5.2 km) from their nest sites in foraging trips lasting a mean of 8.4 hours. Foraging was concentrated in coastal waters less than 500 m from the shore, with several birds approaching a distance of 1 km. As in the previous study, most dives were shallow, with 90% of time spent underwater at depths of less than 6 min. A maximum dive depth of 52 m was however recorded. Male birds tended to travel further than females and mean distances varied from site to site. The reason for the tendency of Galapagos Penguins to forage in close proximity to the coast, which is unique among penguins, was attributed by the authors to either prey preference or avoidance of predation by the numerous shark species around the Galapagos Islands. It is possibly to avoid competition in their limited foraging areas that Galapagos Penguin colonies are generally relatively small.

Adult Spheniscus Penguins in general have at least one black ring pattern around their bodies. This may be an adaptation to the pursuit of schooling fish, since one has shown that schools of Cape Anchovies tend to depolarize (break up) more frequently when presented with striped models compared to models without stripes (Wilson et al. 1987. Animal Behav. 35(5), p.1558-1560). Predators are thought to be more efficient at catching individual fish compared to fish in dense aggregations which are formed as a defensive strategy. Hence, the stripe may increase foraging efficiency. Its absence in the other genera of penguins which feed on different types of prey supports this notion.

Reproduction:

Nest & Partner Selection

Galapagos Penguins, especially females, often return to their previous nest sites for breeding. The sites are also frequently visited when no breeding is taking place. Nest burrows are largely found in natural cavities in coastal lava deposits, such as small lava tubes, or may be excavated in tuff, as at Elizabeth Bay. Few poorly-arranged objects such as feathers leaves or twigs line the nest and these are probably ritual gifts rather than functional objects in most cases. It is only necessarily to cushion the eggs when the base of the nest is rough, yet in lava cavities, guano from previous seasons usually smooths the base of the nests.

At the onset of a breeding period, unmated birds increasingly spend time visible near the shoreline, possibly in the hope of attracting a mate. Solitary birds are largely males, since these outnumber female birds. Unmated breeding-age females are rarely observed. Once a pair-bond has been established, it is frequently maintained. In years with base-line levels of mortality, 90% of pairs may be maintained from the previous season, with about 5% divorcing and 5% changing due to loss of a partner. Established pairs tend to spend less time on land prior to egg-laying than newly-formed pairs. Ultimately, it is thought that the female chooses its mate. Body size is not clearly correlated with mate selection. The selection criteria are presently unknown.

There are several forms of behaviour associated with courtship. The Galapagos Penguin does however not perform anything resembling an ecstatic display, which is a prominent form of behaviour in many penguin species, including the other Spheniscids.

Mutual preening (allopreening) is generally only observed around the breeding season. Standing near to each other, socializing individuals or established pairs initially preen themselves. After a brief pause, one of the birds starts to preen the other on the head or neck. The other bird may continue to preen itself or may reciprocate this behaviour.

Bill duelling is often observed when one bird closely approaches another, sometimes after landing at the beach. The birds face each other and vigorously shake their heads from side to side, resulting in repeated clattering of the tips of the bills. Paired or unpaired penguins may perform this behaviour. In the former case the penguins remain close after performing this ritual and may either simply relax or alternatively flipper-patting and often copulation may follow.

Pair interaction (1)	Pair interaction (2)

Pair interaction (3)	Pair interaction (4), just before onset of bill duelling

Flipper-patting is performed by the male which rapidly pats his partner as he edges round to the back of her. The male then leans onto the female, gently forcing her to lie prone on the ground. The male climbs onto the back of the female and flipper-patting continues together with some bill interaction as the female penguin raises her bill and both turn their heads from side to side. The male positions itself so as to bring the cloaca in close proximity. For copulation to occur, the female lifts its tale up and the male rounds the back of his body to dip his cloaca onto that of the female. Cloacal contact and the associated sperm transfer may last for over 30 secs but is usually shorter. After attempted copulation, the male slips off and may walk aside the female often with its head bowed. Both penguins make shake their tails or make swallowing motions. Successful copulation is observed in under 50% of cases and is followed by similar behaviour.

Interestingly, copulation attempts have been observed in shallow water by the beach, although it is not known whether such events are productive.

Timing of Breeding

Galapagos Penguins are the only species without a clearly defined breeding season. Breeding has been observed at any time of year and rather than being seasonally determined appears to occur in response to suitable oceanic conditions, largely correlated with sea-surface temperatures of below about 24'C. Breeding does not commence, or ceases, when water temperatures are higher. Looking at past data, it appears that February-March may be a period with slightly reduced breeding frequency, with May-December being slightly elevated (Boersma 1978. Science 200, p.1481-1483), however these are very weak trends. Breeding may also not be synchronized between colonies at different locations.

Laying and Incubation

In the period before egg-laying, Galapagos Penguins spend an increasing amount of time on land. They are often seen standing near the nest site. The males tend to occupy the nests as egg-laying approaches and often are observed braying at dawn and dusk. Both birds generally remain by the nest when the first egg is approaching and the female often remains on the nest during the whole egg-laying period or performs one foraging trip before the second egg arrives 3-4 days after the first. First eggs are longer, whilst second eggs are wider, although there is no significant dimorphism in egg mass.

Incubation commences immediately after laying of the first egg. Most penguins only consistently incubate after arrival of the second egg.

Desertion rates of eggs are slightly elevated 12-20 days into incubation, although desertion can occur at any time albeit at lower frequency.

Incubation Duties

Incubation is shared between the pair, with mean lengths of male incubation periods being 1.9 days and of females 2.0 days. During optimal breeding conditions, daily alternation may take place. Absences of up to 10 days have been reported. Long absences are however often linked to nest desertion.

Incubation periods of the eggs are about 38 days. The first egg tends to hatch 2-3 days before the second. The second egg is slightly less likely to hatch, possibly due to lack of fertilization or poorer egg composition.

Brood / Guard Phase

Generally, both eggs hatch and the chicks are initially guarded for about 25-30 days, before being left alone at the nest site. During the first about 15 days, the chicks are brooded. After this time, the chicks are able to maintain their own body temperatures and the parents presence serves largely to protect against predation by the Sally Lightfoot Crab, Rice Rat or one of the Galapagos Snakes.

The guard phase may be slightly longer for single chicks. When conditions are good, provisioning usually occurs once a day as one of the parents returns to the nest in the evening. Observations of the provisioning of one chick revealed that it received about 20 fish of an estimated length of about 10 cm every evening after dark. The female fed more frequently, yet sometimes both mates fed on a single night. Weight gain by is generally around 35 g per day during productive breeding periods, with older chicks generally gaining weight slightly faster in most cases. Lone chicks gain weight even faster, although the differences are usually only a few grams. When water temperatures are higher, weight gain is generally reduced and differences between younger, older and lone chicks become more pronounced. Commonly, one of the chicks dies, often during the first 2-12 days after hatching, largely of starvation. It is thought that if parental birds are in poor condition they will initially focus on one chick, whilst abandoning the other. If the conditions remain poor, both chicks may be abandoned.

Nest desertion rates clearly correlate to higher water temperatures. Adults generally lose weight as chicks grow and present increasing food demands. It has been shown that adults with below-average weights desert their nests first. Desertion is evidently triggered by the need to forage and gain weight to avoid starvation. Where adults were observed to relieve each other at the nest daily, nest desertions were not observed. On the other hand, where one adult was absent from the nest site for 4 or more days on three occasions, nest failure always followed. Basically, long intervals between nest reliefs indicate food shortage and unwillingness to provision the chicks at the expense of own body condition. Not only the chicks suffer, but also the bird remaining on the nest will lose nearly 50 g per day. This is clearly not tenable over a long time-period.

Parents may be observed preening their chicks although this is not reciprocated. Pecking between siblings is common and is usually directed at the smaller one.

Creche Phase (Absent)

Unlike many other penguin species, including all surface-nesting species, Galapagos Penguin chicks do not form creches. They generally stay in or close to their own nests until shortly before fledging.

Accoustic Parent-Chick Recognition

Not studied in detail in the Galapagos Penguin. Importance may not be high compared to in some other penguin species, since the nest is the focal point for meeting the chick(s) and no creches form, necessitating recognition of the own chicks. Nevertheless, calls of Spheniscus Penguins are considered individually distinctive, including calls by adults and the so-called peep of the chicks.

Fledging

In good breeding seasons, 1.3 chicks per nest can reach fledging age, whereas in poor seasons total failure of nests can occur. By the time they fledge, juveniles have usually attained a body mass approximating to the mean mass of female adult birds. Most body parts approach adult size after 30-40 days, which accounts for the disproportionately large size of e.g. feet and flippers in young penguins.

Immature Galapagos Penguins can be recognized by the grey, as opposed to black, feathering on their backs. Further, they lack the body banding of adults and have greyish faces with whitish-coloured cheek patches. The first moult is often performed after about 6 months, after which the adult plumage is obtained. Diffentiation is then only possible based on bill, feet and eye colouration which initially differs from that of older adults.

	Juvenile Galapagos Penguin(s)

Adult (left), Juvenile (right)	Juvenile Galapagos Penguin	Adult (left), Juvenile (right)

The initial lack of body banding is common to juveniles of all Spheniscus species and may confer a selective disadvantage compared to adults when foraging. The black band has been shown to increase temporary dispersal of schooling fish, allowing easier predation (Wilson et al. 1987. Animal Behav. 35(5), p.1558-1560).

Pre-Breeding Moult

Galapagos Penguins moult before breeding. Unpaired males may however moult during the breeding period. The pre-breedng moult is probably an adaptation to the extreme fluctuations in food availability. The moulting period presents the greatest risk of starvation to adult penguins. Hence, it seems that during good conditions the moult is prioritized and performed first, shortly afterwards followed by breeding if conditions remain suitable. Moulting may also occur more than once in certain years. Possibly, avoiding waiting to moult at the last minute when the plumage is severely worn, means that the birds have more flexibility in adapting to changes in conditions. Alternatively, it has been suggested that plumage-wear is high due to the tropical sun and necessitates more frequent moulting.

Before moulting, Galapagos Penguins spend about a month foraging to gain weight in advance of the energy-consuming moult process. The mean pre-moult increase in body weight is approx. 400 g, whilst about 600 g are lost during the moult process. Moulting usually involves a period of 15 days on shore. Underweight penguins may return to sea after only 10 days in order to avoid starvation, although the insulation properties of their plumage is probably poor and together with their reduced fat layer they must suffer increased heat loss at sea. Few of these abortive moulters are likely to survive. Female birds are slightly smaller and lighter than males and this may account for their higher mortality during extreme ENSO events, which contributes to the generally higher proportion of males in the population.

Penguin (right) has removed most of old feathers and apparently continues to preen. This is relatively unusual.	Moulting Galapagos Penguins. Normally old feathers are gradually lost as in right-hand penguin.

	Moulting Galapagos Penguins

The plumage of males and females differs slightly, with male plumage involving slightly bolder markings. Individuals can be recognized by markings on the pink exposed skin at the base of the bill.

General Behaviour:

The most common and easily recognizable form of maintenance behaviour, preening, is shared by all penguin species. Galapagos Penguins often spend over an hour preening after returning from sea and may also be observed preening in shallow waters near the coastline. This behaviour serves to clean the plumage and spread the diester wax-rich preen oil exuded by the uropygial (preen) gland to maintain waterproofing. Various stretching motions are interspersed between the preening. In the both-wing stretch, the penguin leans forward, stretches its neck forwards whilst tipping the head upwards, and extends its wings backwards to above the body. The bill may be opened to perform a jaw-stretch. The tail is often wagged after bouts of preening, but also after excretion.

Both-Wing Stretch Accompanied by Jaw Stretch	Galapagos Penguin Preening Flipper

Galapagos Penguin Preening Back / Accessing Preen Gland	Galapagos Penguin Scratching Head with Foot

Preening	Preening at Sea is Commonly Observed	Distributing Preen Gland Excretions on Flipper

Aggression and appeasement behaviours are well documented. When one penguin approaches another too closely aggressive behaviour may occur. This involves flattening of the feathers on top of the head, raising of neck feathers and pointing of the bill, possibly with the neck stretched forwards. It may also involved tipping of the head from side to side, similar to the alternative stare seen in some other penguins. The intruding penguin may return the threats and this may result in "yelling" of the birds at each other and ultimately pecking. On the other hand, the intruder may appease the threatening bird. This apparently involves certain head-movements which are unique, or at least far more pronounced, in Galapagos Penguins, compared to other species. Head-movements involve movement of the bill in an arc. Passing through a slightly lowered central position, the bill is swung about 45' to either side and is lifted to about 140' above the ground at each side of the arc. Penguins perform this behaviour before retreating and are not generally pecked in the process. Juveniles are pecked more than adults since they neither rapidly retreat, nor perform as many head movements as adults.

Galapagos Penguins sleep either with their flippers under the body or resting on the side of the body. They do not tuck their bills under their flippers.

Galapagos Penguin resting	Galapagos Penguins resting

Walking is relatively steady, involving less swaying from side to side than in many other penguins. Tobogganing is rare, due to the unsuitable substrate, and may be only accidental after stumbling when fleeing.

Several forms of behaviour associated with mating have been described under the heading "Nest and Partner Selection".

Threats:

Climate Change / ENSO Events

The greatest threat to the survival of the Galapagos Penguin is global warming. Galapagos Penguins are only able to exist around the equator due to the cold Equatorial Undercurrent (Cromwell Current) which flows eastwards through the Galapagos Archipelago and is forced upwards in the vicinity of Fernandina and Isabela Islands. El Nino Southern Oscillation (ENSO) events equally affect the upwelling of the Humboldt Current along the west coast of South America and the upwelling of the Cromwell Current at Galapagos. An increase in upwelling which may last for up to a year and causes high marine productivity generally precedes ENSO events due to strong southeast trade winds increasing circulation of the South Pacific subtropical gyre (Wyrtki 1975. J. Phys. Oceanogr. 5, p.572-584). However, upwelling is subsequently reduced to below normal levels, leading to high sea surface temperatures in the affected coastal waters and an associated decline in productivity. During intense ENSO events this may lead to severe mortality and breeding failure of seabird populations.

The Humboldt Penguin populations in Peru and Northern Chile suffer severely and the entire Galapagos Penguin population is threatened by such events. The magnitude of the problem has been illustrated by past ENSO events. On Fernandina, in 1971, 63 of 82 monitored nests successfully fledged at least one chick. This coincided with productive pre-ENSO conditions. However, during the ENSO event, breeding attempts in Dec. 1972 - Mar. 1973 and Aug. - Oct. 1973 resulted in a total of only one chick from 200 monitored nests (Boersma 1978. Science 200, p.1481-1483). The weight of adult birds was well below long-term average during the event and several starved adults were found weighing under 1.8 kg, although adult mortality was not extremely high (Boersma 1998. Condor 100, p.245-253). An even more severe ENSO event occurred in 1982-83 and led to huge adult mortality approximating to 77% of the pre-ENSO population (Valle and Coulter 1987. Condor 89, p.276-281). Recovery of the population after this event was slow. This can be attributed to the fact that since the 1980s, there has been a general trend to warmer water temperatures with few and weak El Nina events where water temperatures are lower and productivity is high (Boersma 1998. Condor 100, p.245-253). Thus, the population had not fully recovered when it was hit by a further extreme ENSO event in 1997-98 which reduced the remaining population by about 65%. Making matters worse, mortality of females was particularly high, leading to an excess of male birds which could not contribute to population recovery (Boersma 1998. Penguin Conserv. Nov. 98, p.10-11). In Humboldt Penguins, nest intrusion behaviour by unmated males resulted in several incidents of egg loss or chick mortality and was responsible for over 10% of breeding failure at a study colony (Taylor et al. 2001. Condor 103(1), p.162-165). If such behaviour also occurs in Galapagos Penguins, this could inhibit population recovery when there is a surplus of male birds.

The trends in the Galapagos Penguin population from 1970 to 2003 reveal that recovery following the steep ENSO-induced population declines continued to be slow into the 21st century (Vargas et al. 2005. Ibis 147, p.367-374). The census data, which is based on marking and resighting techniques involving subsequent extrapolation of the population size based on the proportion of marked birds amongst those birds resighted, can not provide exact figures, yet the population was estimated at 1350 individuals in 2003, compared to 4000 in 1971.

The Galapagos Penguin has survived ENSO events for many thousands of years. Several studies have addressed the past frequency of ENSO events by studying lake sediments. For example, the varying salinity of sedimentary strata in hypersaline Bainbridge Crater Lake on the Galapagos Islands was studied (Riedlinger et al. 2002 J. Paleolim. 27, p.1-27). Salinity falls during periods of heavy rainfall which are associated with ENSO events. The study concluded that ENSO events were present but infrequent between 6100 and 4000 yrs BP (before present), but occurred with increasing frequency and intensity in the last 4000 years. Significant fluctuations in frequency were observed with 152 moderate and 14 strong / very strong events from 2000-1000 BP (before present), but 5 moderate and 36 strong / very strong events in the last 1000 yrs. Another study analysed even older sediments in Laguna Pallcacocha in southern Ecuador (Rodbell et al. 1999. Science 283, p.516-519). Here, sediments were analysed on the basis of layers of material washed into the lake during periods of heavy rainfall. From 15000 to 7000 BP, periods of over 15 years separated periods of heavy rainfall. However, after this period, the frequency of events continually increased, reaching a periodicity of from 2 to 8.5 years by about 5000 BP. After this period, the long-term average frequency was considered similar to that seen at present.

The problem is that a relatively rapid increase in ENSO events has been recorded since the late 1960s (Trenberth and Hoar 1997. Geophys. Res. Lett. 34, p.3057-3060) and that there are fewer cool El Nina periods in between during which population levels can recover. Indeed, it appears that equatorial upwelling in general has been decreased by 25% after 1970, with an associated rise in mean sea temperatures of nearly 1'C (McPhaden and Zhang 2002. Nature 415, p.603-608).

The survival of the Galapagos Penguin has been modelled based on the continuation of the level and frequency of ENSO events measured in the period between 1964 and 2004 (Vargas et al. 2007. Biol. Conserv. 137, p.138-148). The model estimated a 30% chance of extinction within 100 years. If the frequency of strong ENSO events is doubled, the probability of extinction increases to 80%. Also, the model assumed a 1:1 sex ratio which is at least questionable, especially shortly after severe ENSO events. If the proportion of females is lower, as suggested by some authors, the outlook is even more bleak. Clearly, any further warming trend will reduce the penguins chances further by increasing mortality of adult and juvenile penguins, and by reducing the number of cool years when the population can recover. Most forecasts are presently pessimistic with regard to the issue of global warming, so it is possible that only captive populations will be able to survive in the foreseeable future (the author is presently not aware of the existence of captive populations).

Climatic warming may also be associated with increased wind-speeds and larger waves. Given that most nests are located within 2 m of sea-level, such waves may cause nest flooding. This has indeed been observed in 2004, when at least 4 nests were lost due to a particularly large wave (Vargas et al. 2006. Biol. Conserv. 127, p.107-114). Fishery activities around Galapagos are regulated, yet there is competition between commercial fisheries and penguins for sardines and mullets, which may exacerbate problems during ENSO years. Further, penguins are known to drown after getting caught in nets deployed to catch Mullet or Sharks.

Disease

A major potential threat to the population is also considered to be the introduction of disease, and this may exacerbate the population decline resulting from climatic factors. Galapagos Penguins are immunologically relatively naive. Studies have shown that the birds are seronegative for a wide variety of avian viruses, whilst most have antibodies to Chlamydophila psittaci which is generally asymptomatic in penguins. However, occasional outbreaks of highly virulent strains in captive penguins have been reported (Travis et al. 2006. J. Wildlife Dis. 42(3), p.625-632). Further, due to the small population size and associated levels of inbreeding, variation in the genes of the immune system is very low in the MHC loci which are instrumental in disease resistance (Bollmer et al. 2007. Immunogenet. 59, p.593-602). In general, the Galapagos Penguin has exceedingly low genetic diversity compared to the similar Magellanic or Humboldt Penguins and the population is homogenous in the sense that no subpopulations can be defined based on genetic analysis (Akst et al. 2002. Conserv. Genet. 3, p.375-383; Nims et al. 2008. Conserv. Genet. 9, p.1413-1420). The lack of diversity or subpopulation structure means that the whole population may be ill-equipped if presented with a new pathogen. Further, since the populations at different sites evidently mix, the probability of disease transmission between populations is high.

Human settlement and associated introduction of livestock or parasites bear the risks of exposing the penguins to new diseases. The mosquito Culex quinquefasciatus was first reported on the eastern islands of the Galapagos group in 1989 and has since then established itself and spread to other Islands (Whiteman et al. 2005. Ibis 147, p.843-847). This mosquito has the potential to carry avian malaria and West Nile Virus, in contrast to the native mosquito. Avian Malaria is a major threat to Spheniscus populations in general and can cause over 50% mortality in previously unexposed zoo populations (Cranfield et al. 1991. Sphenisc. Peng. Newslett. 4, p.5-7). It is implicated in the decline of many native forest birds in Hawaii following its introduction (Van Riper 1988. Ecol. Monographs 58, p.111-127).

Penguin blood samples taken in 1996 did not reveal evidence for avian malaria or the avian Herpesvirus Marek's Disease Virus (MDV), which had shortly before caused significant mortality in a Galapagos poultry farm (Miller et al. 2000. Mar. Ornithol. 29, p.43-46). MDV may not be able to infect penguins due to its limited host range, yet continued monitoring is required. Unfortunately, recent research analysing blood samples taken in 2003-2005 has revealed that avian malaria was now already established itself in the Galapagos Penguin population (Levin et al. 2009. Biological Conservation 142, p.3191-3195). Analysis of samples, as in the previous study, involved use of highly sensitive PCR technology which can detect the presence of even minute amounts of Malaria parasite (Plasmodium) DNA. The sequences recovered from the penguins showed little diversity, suggesting that they have recently arrived and had little time to differentiate. Further, they reveal similarity to the species Plasmodium elongatum which is known to cause acute and sometimes fatal infection in penguins. During 2003-2005, levels of Plasmodium infection fluctuated from 3-7% between different sampling periods. There was no obvious upward trend. Infected penguins were detected at various sites on Fernandina, Isabela, Santiago and Bartolome, so essentially the whole range is already affected. No obvious detrimental effects on health were evident and 2 infected birds were recaptured after over half a year. A major concern is how infection will affect penguins when these are weakened by other factors, such as ENSO events. This remains to be established. Further, the development or arrival of a highly virulent strain is a constant threat.

The transmission of disease from poultry is of increasing concern in view of the recent increase in back-yard or large commercial poultry operations on the Galapagos Islands. These provide food for the increasing population and tourist numbers. Seropositivity was found for a number of pathogens in Galapagos chicken stocks during 2001-2003, including Infectious Bursal Disease, Mycoplasma galliseptum, Avian Adenovirus Type I, Marek's Disease, Avian Encephalomyelitis, Infectious Bronchitis Virus and Newcastle Disease Virus (Gottdenker et al. 2005. Biol. Conserv. 126, p.429-439). Many of these are probably endemic in the population, although only few samples seropositive for Newcastle Disease Virus (Avian Paramyxovirus-1) were found, which is a known major threat to penguins. Disease may pass from poultry to wild bird populations via waste and run-off water from poultry farms but also via interaction between humans or wild animals and poultry that can easily occur in often disease-ridden back yard chicken operations.

Pigeons are also regarded as potential transmission sources for avian pathogens and are being actively eradicated (Phillips et al. 2003. Notic. de Galapagos 62, p.6-11).

Infections with parasites such as Filarid nematodes are common in the penguin population but are generally considered subclinical or non-pathogenic. Nevertheless, the emergence of new parasites needs to be monitored. Males were preferentially parasitized in the Galapagos Penguins examined, yet no link between parasite load and body mass could be determined (Merkel et al. 2007. J. Parasitol. 93(3), p.495-503). Dirofilaria immitis can probably cause fatality in penguins and is present on Isabela, yet was not detected in the penguins. The chicken populations studied by Gottdenker et al. also had a number of nematode species and thus could be a source of infections.

Predation

Predation is not considered to pose a major threat at present. Observations suggest that adults or juveniles suffer occasional predation by Galapagos Hawks (Buteo galapagoensis) on land and by Sharks at sea. It is conceivable that owls could also prey on penguins, as well as Fur Seals, Sea Lions and Orcas, which are known to occasionally prey on other penguin species. Predation by feral house cats and dogs is an increasing problem since human settlements have grown in size in recent years. Rats, Snakes and Crabs may take young or eggs, yet these have generally been deserted beforehand. In fact, only a small percent of even deserted eggs disappear.

White-tipped Reef Sharks	Scar from bite	Galapagos Sea Lions

Sally Lightfoot Crab, most common crab on Galapagos	Galapagos Hawk

Volcanic Activity

Volcanic activity may also locally affect penguin populations. During the 1979 eruption of Cerro Azul on Isabela, lava reached the sea and caused an increase in the water temperature at Bahia Elizabeth. It has been suggested that this may have negatively affected penguins at this locality (Harcourt 1980. see Valle and Coulter 1987. Condor 89, p.276-281). However, whilst this may cause some disruption, it is unlikely to cause significant fatalities. Recent volcanism has generally been of a diffusive and relatively benign nature on Galapagos and since the Islands have been formed entirely by volcanic processes, the Galapagos Penguin actually owes its existence to these.

Impact of Tourism

The direct threat caused by tourism is difficult to ascertain. Whilst regulated tourism may have little direct impact on the penguins, rules have often been ignored in the past (De Groot 1983. Biol. Conserv. 26, p.291-300). The situation in this respect seems to be better now. However, the development of touristic infrastructure and need to sustain large numbers of tourists (see e.g. chicken farm issue) has an impact on the Galapagos environment. Further, the economic benefits of tourism have drawn more people to the islands and the local population continues to rise, with all of the problems generally associated with population growth in environmentally sensitive areas. About 27,000 people live on Galapagos and approx. 100,000 tourists visit annually (Boersma et al., 2005. Science 308, p.925). Many building sites around the periphery of the towns are testimony to the continuing population growth.

Where To See:

In order to protect the highly sensitive and unique wildlife of the Galapagos Islands, first wildlife reserves were established in 1934 and the whole archipelago, except for some areas of privately owned land, was designated a National Park in 1959.

Protection of the wildlife has necessitated strict regulation of visitor activities. Visitors may only visit designated areas and trails in the company of an official naturalist guide. Further, many sites have restrictions on the numbers of visitors. Visitor sites are found on all of the larger islands. Since most sites are only accessible from the sea, tourists generally book day trips by boat or multi-day cruises on small vessels (see e.g. www.angelitogalapagos.com) that travel from island to island. The number of penguins at different sites differs from year to year so it is difficult to suggest where best to view them. Many visitors seem to see small groups around Bartolome, although the less frequented sites on the west coast of Isabela and on Fernandina also offer opportunities. The main nesting sites on Isabela at Caleta Iguana, Playa de los Perros, Las Marielas (Mariela Islands) are not open to visitors, although it is possible to circle the Mariela Islands in a zodiac. There is a small island with a tiny rocky outcrop at the entrance of Puerto Villamil harbour, which frequently has penguins on it, especially at dusk. Puerto Villamil is one of several urban zones in Galapagos and has visitor accommodation. Small boats can be easily organized in the harbour to visit the site although a barrier prevents boats from getting closer than about 10 meters.

Penguin Rock, Puerto Villamil, Isabella, Galapagos	Galapagos Penguin, Bartholome Island, by Santiago Island, Galapagos

Galapagos Penguin breeding site - Mariela Islands, Isabella	Penguins on Mariela Island

If lucky enough to encounter the penguins, the guides should make sure that visitors keep at a reasonable distance and do not make any sudden movements or loud noises which may disturb the birds. Nest sites must not be disturbed and moulting birds should be left alone, since this is a critical time for the birds survival.

Penguin on rocks at Punta Moreno, Isabella	Penguin on rocks at Mariela Island