A story of prehistoric Crested Penguins

A story of prehistoric Crested Penguins

by Nataly H. Aranzamendi

Humans have caused the decrease of many island birds, but did humans cause the disappearance of some prehistoric penguins from New Zealand as well? Let’s find out.

Several members of the genus Eudyptes, known as crested penguins, live in the New Zealand archipelago. These species are: the Erect-crested Penguin, the Snares crested Penguin and the Tawaki (a.k.a. Fiordland Penguin). The isolated Pacific island is quite well-known for its stories of bird extinctions. Many taxa including birds and mammals have disappeared from New Zealand due to human pressure, excessive hunting and/or the presence of introduced predators.

The reason why island animals are so vulnerable to new pressures lies in the fact that they have evolved isolated, in a situation where many of them have lost their anti-predator defenses, becoming an easy target for introduced predators and hunters.

Photo Source: travelwayoflife [CC BY-SA 2.0 (https://creativecommons.org/licenses/by-sa/2.0)]

Are crested penguins more sensitive to decline than other penguins?

Due to several studies showing that crested penguins have been declining since the 20th century, many scientists have assumed that crested penguins have been susceptible to human disturbance possibly since historical times, when the first humans arrived to the archipelago.

In a recent study¹ using historic and modern DNA analyses from fossil records, scientists have tried to understand if the current distribution of crested penguins are due to extinction during prehistoric times caused by humans or due to range shift in the distribution of current species.

To test their hypotheses, the study used material from 84 prehistoric bone samples, initially identified as belonging to crested penguins. Those fossils were dug out in mainland New Zealand and right now are deposited in museum collections found in New Zealand and Australia.

How are prehistoric penguins being studied?

The analyses of crested penguins focused on the genetic diversity from genetic markers. The first analysis indicated that New Zealand had six prehistoric penguins inhabiting the island. Possibly, one of the new taxa identified corresponds to a previously undescribed lineage of crested penguin. Such findings indicate that New Zealand had a higher penguin diversity in the past.

The analyses found also that although the range of some penguins might have decreased in extent (e.g. Tawaki), their genetic diversity had remained relatively constant, meaning that it was probably not affected directly by humans. Similar findings were detected across the other species in relation to their genetic diversity. Such findings contrast with what has been found for other New Zealand animals, like fur seals or the Fouveaux shag, which were probably targeted by the first human settlers and that currently show reduced genetic diversity.

It is likely that the southern part of this island has remained relatively isolated and experienced less human pressure in comparison to the northern parts of the island, behaving as a refuge for penguins. In fact, no fossil record of New Zealand South Island endemic penguins exists in the archeological deposits from the North Island, ruling out that the Maori traded with penguins at that time.

The researchers argued that it is also likely that when European settlers arrived, many parts of the South Island were too isolated and remained inaccessible to them. This isolation could explain why the populations of Tawaki remained relatively stable.

Prehistoric penguins still remain a mystery.

The main cause of the disappearance of other prehistoric penguins remains a mystery. Most likely changes in environmental conditions or food sources might have played a big role in the likelihood of extinction of those species, just as it has been found for prehistoric penguins elsewhere.

This study highlights that some island species can be more resilient than others to human disturbances. It is really important for the future of any insular animal population to maintain adequate levels of genetic diversity.

More importantly, including genetic diversity assessments in future conservation proposals will secure the accurate management of species, as well as conservation decisions for penguins. The use of genetic tools in conservation biology has potentially a very bright future ahead.

As for crested penguins, we need to keep investigating which are the most immediate threats that are causing their decline. We want to see them “hopping” for many more centuries ahead.

What do you think after reading about New Zealand and crested penguins? Did you learn anything new? Read some other fun things about these animals we love:

Also, tell us what else you’d like to learn about penguins! We’re here for you.

Cole, T.L., Rawlence, N.J., Dussex, N., Ellenberg, U., Houston, D.M., Mattern, T., Miskelly, C.M., Morrison, K.W., Paul Scofield, R., Tennyson, A.J.D., Thompson, D.R., Wood, J.R., Waters, J.M., Ancient DNA of crested penguins: Testing for temporal genetic shifts in the world’s most diverse penguin clade, Molecular Phylogenetics and Evolution (2018), doi: https://doi.org/10.1016/j.ympev.2018.10.025

Nataly H. Aranzamendi In Blog

How will climate change affect King Penguins?

by Nataly H. Aranzamendi

Recent changes in climate are impacting a variety of species worldwide, and penguins are certainly not immune. King Penguins in particular are extremely sensitive to these changes in their environment.

The King Penguin is considered an indicator species for climate change. With many of their major colonies declining in numbers in recent years, scientists have turned their attention to the causes and consequences of climate change on this species, and the potential actions that could save it from extinction.

Basic information about King Penguins

The King Penguin is an apex predator living in the sub-Antarctic region. King Penguins exclusively breed in year-round ice-free islands scattered throughout the Southern Ocean. To eat, they follow fish stocks around the Antarctic Polar Front, a boundary between colder, saltier water closer to Antarctica and the warmer less salty water of the South Atlantic Ocean.

King Penguins are central place foragers which means that they travel from their nesting sites to a distant foraging location, rather than just passing through an area exploring or traveling at random. Thus, King Penguins have foraging and breeding grounds distributed in a fragmented landscape.

A recent study¹ that monitored the current and ancient conditions of penguin distribution and prey availability has found that the foraging range of King Penguins is displacing southwardly, possibly in response to warming waters. As a result, penguins will have to travel farther to find their prey. This implies that for many populations located in islands in which the foraging range is shifting, there will be decreasing numbers in the future. For example, the Crozet Island population, one of the largest colonies of King Penguins, is already showing declines since the past decade.

When environmental factors change suddenly, species can adjust to these changes using behavioral plasticity (i.e. changing behaviors) or by rapidly evolving. For example, penguins could change behavior and colonize new islands (i.e. disperse) and/or could start traveling farther distances.

What does that changing climate mean for King Penguins?

However, scientists have found that penguins traveling further are putting their energetic balance at risk, eventually having lower reproductive success. If that balance is altered in several hundreds of individuals at a colony, it will be disastrous.

In order to predict what will happen with King Penguins in the upcoming decades, scientists had to first reconstruct a palaeohabitat of the species’ demography, based on old climatic records and genome information. This allowed them to understand the primary causes of population changes.

They found out that massive changes in the ocean’s primary productivity caused large population changes in the past for penguins. Therefore, prey availability would be the most important limiting factor for the King Penguin’s distribution in the future.

If the worst scenario of climate change occurs, many big colonies will witness dramatic declines in numbers, because the distance to their foraging grounds will increase considerably. Most of the colonies negatively impacted are located in the northern range of the species’ distribution. The colonies at the South of the Antarctic Front will probably be the best refugia for King penguins, places such as South Georgia Island. Potentially, there will also be new colonies that could be recolonized.

The low genetic diversity of this species as well as the long time to mature and produce offspring will most likely not allow rapid adaptive evolution in this species. Changes in foraging conditions would be required for penguins to survive. Eventually, the outcome for many individuals could be local extinction or dispersal to new islands (if available).

How does the future look for King Penguins?

The predictions that scientists made for total numbers are dramatic. In the worst scenario, up to 70% of the present breeding pairs of King Penguins could disappear. Moreover, almost 50% of the current world population could lose their habitat, especially those located in the largest and northernmost colonies. Such predictions do not even take into account possible simultaneous changes that could impact penguin prey.

In summary, recent data is providing more and more evidence of our negative impact in the natural world due to climate change. Many species will lose their habitat due to range shifts everywhere, not only King Penguins. It is our responsibility as human beings to work together in this climate crisis and not let our planet drift toward the worst scenario in the upcoming decades. King Penguins will be really thankful.

A King Penguin feeding its chick

Did you know this about King Penguins? What do you think and/or what did you learn by reading this?

Learn more about penguins by reading some of our other blogs:

References:

Cristofari, R., Liu, X., Bonadonna, F., Cherel, Y., Pistorius, P., Le Maho, Y., … & Trucchi, E. (2018). Climate-driven range shifts of the king penguin in a fragmented ecosystem. Nature Climate Change, 8(3), 245.

Nataly H. Aranzamendi In Blog

Magellanic Penguins Are Exemplar Parents

Magellanic Penguins Are Exemplar Parents

by Nataly H. Aranzamendi

The number of chicks produced and that survive their first life stages determines the success of penguin parents. This has important consequences for populations. Let’s discover how Magellanic Penguins decide to distribute food among their babies.

Year to year variation in reproduction is a central theme in population biology with important consequences on the emographics of any animal species.

Each breeding season, parents have to provide quality food to their offspring in order to guarantee their survival. While some birds produce only one chick per season, others can produce more. In this case, it is expected that parents will distribute food evenly among their offspring.

One thing that has puzzled biologist for decades is that many birds seem to produce an amount of eggs that is larger than what they can successfully raise. Also, these birds lay their eggs in an asynchronous fashion. As a result, asynchronous chicks hatch several days apart, showing a visible difference in size, i.e. the first chick tends to be heavier than the last one. Thus, biologists have suggested that these asymmetries between siblings could facilitate a reduction in the number of offspring.

Do penguins use a brood reduction strategy?

The “brood reduction hypothesis” says that when food is limiting, parents would preferentially care for the offspring with more chances of survival, which is usually the heavier chicks. Brood reduction can also occur via sibling competition, as bigger chicks can succeed more in obtaining their parent’s attention and outcompete their smaller siblings 1.

In a new study 2 , a group of scientists tested the brood reduction hypothesis for three breeding seasons in Magellanic Penguins in Punta Tombo, Argentina.

Magellanic Penguins generally lay 2 eggs four days apart from each other. The first chick hatches with a 2-day advantage from the second, therefore, the chances for the smaller chick to survive are generally lower.

Scientists compared the feeding frequency of parents of two-egg broods vs. parents of single-egg broods, and checked if they were distributing food evenly or differently between their offspring.

The results show that once chicks have survived their first weeks of life, parents with two chicks fed them evenly despite their differences in size. Interestingly, the heavier sibling does not try to outcompete or interrupt its lighter sibling.

An indicator that chicks are hungry is the rate of begging. As soon as parents approached the nests, chicks started begging to request food. The results show that the rate of begging was also the best predictor of the amount of food nestlings were going to receive.

By Liam Quinn from Canada – Magellanic Penguin chicks, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=24446501

How do Magellanic Penguins compare to other penguin species?

But what does this mean for Magellanic Penguins and how does it compare to other species? It is possible that in this species, neglecting any offspring could be very disadvantageous decision for a parent. Since feedings occur every 3 to 5 days, denying even one opportunity to be fed would mean a certain death for the smaller nestling.

This also most likely means that the period in which the researchers measured these behaviors coincided with a time when parents had already invested too much in their chicks survival.

In other birds with asynchronous chicks, parents can sometimes switch their strategy and preferentially feed the smaller chicks once they have passed their first day’s threshold. However, this switch was not observed in Magellanic Penguins.

Other penguins show different behaviors towards their offspring at the time of feeding. Chinstrap and Adélie penguins, for example, motivate their chicks with a chase prior to feeding, then they only feed the chick that passed the test and behaved more motivated.

African Penguins, which are close relatives of Magellanic Penguins, have offspring constantly interfering with each other at the moment of eating. Thus, older siblings eventually reduce the survival of younger siblings. One possible explanation for this difference in behaviors between the two species could be the fact that the starvation peak period for both species differs. It occurs earlier for Magellanic Penguins and later for African Penguins.
In any case, it is plausible that these observations were made in years of greater food availability, which could have helped the initial survival of the smaller chicks. Most interestingly, we have learned that Magellanic Penguins seem to be fair parents when it’s time to distribute food.

What do you think about these Magellanic parents? Let us know! And, have you read some of our other recent penguin blogs?

References:

https://en.wikipedia.org/wiki/Brood_reduction

Wagner, E. L., & Boersma, P. D. (2019). Food allocation and feeding
behaviours of Magellanic penguin, Spheniscus magellanicus, adults and
chicks. Animal Behaviour, 148, 161-168.

March 2019