Zoos aren’t Victorian-era throwbacks: they’re important in saving species



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A meerkat at the National Zoo and Aquarium in Canberra. The Zoo has recently announced an expansion that will double its size.
AAP Image/Stefan Postles

Alienor Chauvenet, The University of Queensland

The National Zoo and Aquarium in Canberra recently announced a new expansion that will double its size, with open range space for large animals like white rhinos and cheetahs.

As well as improving visitors’ experience, the expansion is touted as a way to improve the zoo’s breeding program for threatened animals. However, zoos have received plenty of criticism over their capacity to educate, conserve, or even keep animals alive.

But while zoos began as 19th-century menageries, they’ve come a long way since then. They’re responsible for saving 10 iconic species worldwide. Without captive breeding and reintroduction efforts, there might be no Californian Condor or Przewalski’s Horse – the only truly wild horse – left in the wild.

Australian zoos form part of a vital global network that keeps our most vulnerable species alive.

What is the role of zoos for conservation?

Although Canberra Zoo is relatively new compared with others in Australia – Melbourne zoo, for example, was opened in 1862 – it adds to a collection of conservation-orientated establishments.

In Australia, Taronga Conservation Society Australia, the Royal Melbourne Zoological Gardens, Adelaide Zoo and Perth Zoo are all members of the World Association of Zoos and Aquariums (WAZA). WAZA is an international organisation that aims to guide and support zoos in their conservation missions, including captive breeding, reintroductions into the wild, habitat restoration, and genetic management.

From the perspective of nature conservation, zoos have two major roles: educating the public about the plight of our fauna, and contributing to species recovery in the wild.

Conservation education is deeply embedded in the values of many zoos, especially in Australia. The evidence for the link between zoo education and conservation outcomes is mixed, however zoos are, above anybody else, aimed at children. Evidence shows that after guided experiences in zoos children know more about nature and are more likely to have a positive attitude towards it. Importantly, this attitude is transferable to their parents.

Zoos contribute unique knowledge and research to support field conservation programs, and thus species recovery. In Australia, zoos are directly involved in monitoring of free-ranging native fauna and investigations into emerging diseases. Without zoos many fundamental questions about a species’ biology could not be answered, and we would lack essential knowledge on animal handling, husbandry and care.

Through captive breeding, zoos can secure healthy animals that can be introduced to old or new habitats, or bolster existing wild populations. For example, a conservation manager at Taronga Zoo told me they’ve released more than 50,000 animals that were either bred on-site or rehabilitated in their wildlife hospitals (another important function of zoos).

Criticisms of captive breeding programs

The critics of captive breeding as a conservation strategy raise several concerns. Captive bred population can lose essential behavioural and cultural adaptations, as well as genetic diversity. Large predators – cats, bears and wolves – are more likely to be affected.

Some species, such as frogs, do well in captivity, breed fast, and are able to be released into nature with limited or no training. For others, there is usually a concerted effort to maintain wild behaviour.

There’s a higher chance of disease wiping out zoo populations due to animal proximity. In 2004 the largest tiger zoo in Thailand experienced an outbreak of H5N1 bird flu after 16 tigers were fed contaminated raw chicken; ultimately 147 tigers died or were put down.

However, despite these risks, research shows that reintroduction campaigns improve the prospects of endangered species, and zoos can play a crucial role in conservation. Zoos are continually improving their management of the genetics, behaviour and epidemiology of captive populations.

They are the last resort for species on the brink of extinction, such as the Orange-bellied Parrot or the Scimitar-horned Oryx, and for those facing a threat that we cannot stop yet, such as amphibians threatened by the deadly Chytrid fungus.

Orange-bellied parrots are ranked among the most endangered species on the planet – their survival depends on zoos.
Chris Tzaros/AAP

Zoos need clear priorities

A cost-benefit approach can help zoos prioritise their actions. Taronga, for example, uses a prioritisation system to decide which projects to take on, with and without captive breeding. Their aim is to a foresee threats to wildlife and ecosystems and implement strategies that ensure sustainability.

Developing prioritisation systems relies on clearly defined objectives. Is there value in keeping a species in captivity indefinitely, perhaps focusing only on education? Is contributing to a wild population the end goal, requiring both education and active conservation?

Once this is defined, zoos can assess the benefit and costs of different actions, by asking sometimes difficult questions. Is a particular species declining in the wild? Can we secure a genetically diverse sample before it is too late? Will capturing animals impact the viability of the wild population? How likely is successful reintroduction? Can we provide enough space and stimulation for the animals, and how expensive are they to keep?

Decision science can help zoos navigate these many factors to identify the best species to target for active captive conservation. In Australia, some of the rapidly declining northern mammals, which currently do not have viable zoo populations, could be a good place to start.

Partnerships with governmental agencies, universities and other groups are essential to all of these activities. Zoos in Australia are experts at engaging with these groups to help answer and address wildlife issues.


The ConversationAlienor Chauvenet would like to acknowledge the contribution of Hugh Possingham to this article, and thank Nick Boyle and Justine O’Brien from Taronga Conservation Society Australia for the information they provided.

Alienor Chauvenet, Postdoctoral Research Fellow, The University of Queensland

This article was originally published on The Conversation. Read the original article.

Scientists are accidentally helping poachers drive rare species to extinction



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The beautiful Chinese cave gecko, or Goniurosaurus luii, is highly prized by poachers.
Carola Jucknies

Benjamin Scheele, Australian National University and David Lindenmayer, Australian National University

If you open Google and start typing “Chinese cave gecko”, the text will auto-populate to “Chinese cave gecko for sale” – just US$150, with delivery. This extremely rare species is just one of an increasingly large number of animals being pushed to extinction in the wild by animal trafficking.

What’s shocking is that the illegal trade in Chinese cave geckoes began so soon after they were first scientifically described in the early 2000s.

It’s not an isolated case; poachers are trawling scientific papers for information on the location and habits of new, rare species.

As we argue in an essay published today in Science, scientists may have to rethink how much information we publicly publish. Ironically, the principles of open access and transparency have led to the creation of detailed online databases that pose a very real threat to endangered species.

We have personally experienced this, in our research on the endangered pink-tailed worm-lizard, a startling creature that resembles a snake. Biologists working in New South Wales are required to provide location data on all species they discover during scientific surveys to an online wildlife atlas.

But after we published our data, the landowners with whom we worked began to find trespassers on their properties. The interlopers had scoured online wildlife atlases. As well as putting animals at risk, this undermines vital long-term relationships between researchers and landowners.

The endangered pink-tailed worm-lizard (Aprasia parapulchella).
Author provided

The illegal trade in wildlife has exploded online. Several recently described species have been devastated by poaching almost immediately after appearing in the scientific literature. Particularly at risk are animals with small geographic ranges and specialised habitats, which can be most easily pinpointed.

Poaching isn’t the only problem that is exacerbated by unrestricted access to information on rare and endangered species. Overzealous wildlife enthusiasts are increasingly scanning scientific papers, government and NGO reports, and wildlife atlases to track down unusual species to photograph or handle.

This can seriously disturb the animals, destroy specialised microhabitats, and spread disease. A striking example is the recent outbreak in Europe of a amphibian chytrid fungus, which essentially “eats” the skin of salamanders.

This pathogen was introduced from Asia through wildlife trade, and has already driven some fire salamander populations to extinction.

Fire salamanders have been devastated by diseases introduced through the wildlife trade.
Erwin Gruber

Rethinking unrestricted access

In an era when poachers can arm themselves with the latest scientific data, we must urgently rethink whether it is appropriate to put detailed location and habitat information into the public domain.

We argue that before publishing, scientists must ask themselves: will this information aid or harm conservation efforts? Is this species particularly vulnerable to disruption? Is it slow-growing and long-lived? Is it likely to be poached?

Fortunately, this calculus will only be relevant in a few cases. Researchers might feel an intellectual passion for the least lovable subjects, but when it comes to poaching, it is generally only charismatic and attractive animals that have broad commercial appeal.

But in high-risk cases, where economically valuable species lack adequate protection, scientists need to consider censoring themselves to avoid unintentionally contributing to species declines.

Restricting information on rare and endangered species has trade-offs, and might inhibit some conservation efforts. Yet, much useful information can still be openly published without including specific details that could help the nefarious (or misguided) to find a vulnerable species.

There are signs people are beginning to recognise this problem and adapt to it. For example, new species descriptions are now being published without location data or habitat descriptions.

Biologists can take a lesson from other fields such as palaeontology, where important fossil sites are often kept secret to avoid illegal collection. Similar practices are also common in archaeology.

Restricting the open publication of scientifically and socially important information brings its own challenges, and we don’t have all the answers. For example, the dilemma of organising secure databases to collate data on a global scale remains unresolved.

For the most part, the move towards making research freely available is positive; encouraging collaboration and driving new discoveries. But legal or academic requirements to publish location data may be dangerously out of step with real-life risks.

The ConversationBiologists have a centuries-old tradition of publishing information on rare and endangered species. For much of this history it was an innocuous practice, but as the world changes, scientists must rethink old norms.

Benjamin Scheele, Postdoctoral Research Fellow in Ecology, Australian National University and David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University

This article was originally published on The Conversation. Read the original article.

The plan to protect wildlife displaced by the Hume Highway has failed



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Hundreds of large old trees were removed when the Hume Highway was widened.
Brian Yap/Flickr, CC BY-NC

David Lindenmayer, Australian National University; Martine Maron, The University of Queensland; Megan C Evans, The University of Queensland, and Philip Gibbons, Australian National University

It’s no secret that human development frequently comes at a cost to other creatures. As our urban footprint expands, native habitat contracts. To compensate for this, most Australian governments require developers to invest in biodiversity offsetting, where habitat is created or protected elsewhere to counterbalance the impact of construction.

Researchers monitored hundreds of nest boxes used to offset habitat loss.
Mason Crane, Author provided

Although biodiversity offsetting is frequently used in Australia – and is becoming increasingly popular around the world – we rarely know whether offsets are actually effective.

That’s why we spent four years monitoring the program designed to offset the environmental losses caused by widening the Hume Highway between Holbrook and Coolac, New South Wales. Our research has found it was completely ineffective.


Map courtesy Google/The Conversation, CC BY-ND

Trading trees for boxes

The roadworks required the removal of large, old, hollow-bearing trees, which are critical nesting sites for many animals, including several threatened species. To compensate for these losses, the developer was required to install one nest box for every hollow that was lost – roughly 600 nest boxes were installed.

Wild honeybees occupied many nest boxes.
Mason Crane, Author provided

Many of the boxes were specifically designed for three threatened species: the squirrel glider, the superb parrot and the brown treecreeper. We monitored the offset for four years to see whether local wildlife used the nest boxes.

We found that the nest boxes were rarely used, with just seven records of the squirrel glider, two of the brown treecreeper, and none of the superb parrot. We often saw all three species in large old tree hollows in the area around the boxes we monitored.

Even more worryingly, almost 10% of the boxes collapsed, were stolen or otherwise rendered ineffective just four years after being installed. Perversely, we found that invasive species such as feral bees and black rats frequently occupied the nest boxes.

The offset clearly failed to deliver the environmental outcomes that were promised. Indeed, researchers have been concerned for some time now that offsetting can be misused and abused.

What can be done?

It’s worth noting that research supports using nest boxes as a habitat replacement. However, they may never be effective for species such as the superb parrot. It’s not quite clear why some animals use nest boxes and others don’t, but earlier monitoring projects in the same area found superb parrots consistently avoid them.

Still, concrete steps can – and should – be taken to improve similar offset programs.

First, the one-to-one ratio of nest boxes to tree hollows was inadequate; far more nest boxes needed to be installed to replace the natural hollows that were lost.

There also was no requirement to regularly replace nest boxes as they degrade. It can take a hundred years or more for trees to develop natural hollows suitable for nesting wildlife. To truly offset their removal, thousands of boxes may be required over many decades.

An old hollow-bearing river red gum. Trees like this are vital habitat for many species.
Peter Halasz/Wikimedia commons, CC BY-SA

Second, nest boxes clearly cannot compensate for the many other key ecological values of large old trees (such as carbon storage, flowering pulses or foraging habitat). This suggests that more effort is needed at the beginning of a development proposal to avoid damaging environmental assets that are extremely difficult to replace – such as large old trees.

Third, where it is simply impossible to protect key features of the environment during infrastructure development, more holistic strategies should be considered. For example, in the case of the woodlands around the Hume Highway, encouraging natural regeneration can help replace old trees.

Tree planting on farms can also make a significant contribution to biodiversity – and some of these may eventually become hollow-bearing trees. A combination of planting new trees and maintaining adequate artificial hollows while those trees mature might be a better approach.

Being accountable for failure

When an offset program fails, it’s unlikely anyone will be asked to rectify the situation. This is because developers are only required to initiate an offset, and are not responsible for their long-term outcomes.

In the case of the Hume Highway development, the conditions of approval specified that nest boxes were to be installed, but not that they be effective.

Despite the ecological failure of the offset (and over A$200,000 invested), the developer has met these legal obligations.

This distinction between offset compliance and offset effectiveness is a real problem. The Australian government has produced a draft policy of outcomes-based conditions, but using these conditions isn’t mandatory.

The poor results of the Hume Highway offset program are sobering. However, organisations like Roads and Maritime Services are to be commended for ensuring that monitoring was completed and for making the data available for public scrutiny – many agencies do not even do that.

The ConversationIndeed, through monitoring and evaluation we can often learn more from failures than successes. There are salutary lessons here, critical to ensuring mistakes are not repeated.

David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University; Martine Maron, ARC Future Fellow and Associate Professor of Environmental Management, The University of Queensland; Megan C Evans, Postdoctoral Research Fellow, Environmental Policy, The University of Queensland, and Philip Gibbons, Senior Lecturer, Australian National University

This article was originally published on The Conversation. Read the original article.

Thinking big gives top predators the competitive edge



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Dingoes can help manage devastating red fox and feral cat numbers, but only if we let enough of them live in key areas.
Bobby Tamayo, Author provided

Thomas Newsome, Deakin University

Dingoes could be the key to controlling red foxes and other invasive predators, but only if we encourage them in large enough numbers over a wide enough area, our research shows.

Interest in re-introducing or restoring top predators, like dingoes and wolves, has been fuelled by recent studies demonstrating their important roles in their ecosystems. They can especially be vital in suppressing the abundance of lower-order competitors or “mesopredators”, like red foxes and possibly feral cats (which can have devastating effects on native species).

But researchers have found top predators aren’t always successful in reducing mesopredator numbers. Until now, such variation has been linked to human presence, land-use changes and environmental factors such as landscape productivity.

However, our research, published yesterday in Nature Communications, found that a key factor for success is high numbers of dingoes and wolves across their natural range.

The density effect

If you look at how species are typically distributed across a landscape – their range – ecological theory predicts there’ll be lower numbers at the outer edges of their range.

If you do need large numbers of top predators to effectively suppress mesopredators, the core of their range is potentially the best place to look.

We tested this idea, looking at the dingo in Australia and the grey wolf in North America and Europe. The mesopredators included the red fox in Australia, the coyote in North America and the golden jackal in Europe.

We looked at three regions in our study. Predator distribution is shown for: a) coyotes (hashed) and grey wolves (orange) in Saskatchewan, North America (present day); b) golden jackals (hashed) and grey wolves (orange) in Bulgaria and Serbia (present day); and c) red foxes (hashed) and dingoes (orange) in Queensland, Australia (in the 1950s).
Predator images: Doug McLaughlin; Bobby Tamayo, Harley Kingston/flickr, Larry Lamsa/flickr

We used information from bounty hunting programs, as these provide data on predator numbers across a wide geographical area. In the case of Australia we used historic data from the 1950s, as this is the most recent reliable information about red fox and dingo distribution. The actual population numbers of red foxes and dingoes have changed substantially since then, but the nature of their interactions – which is what we were investigating – has not.

We determined that top predators exist in higher numbers at the core of their ranges in comparison to the edges. We then looked at mesopredator numbers across the range edges of their respective top predator.

Predator bounties and top predator range edges in each continent. The number of bounties (representing the number of animals killed) are given for each hunting unit in North America (collated from 1982 to 2011) and Europe (collated from 2000 to 2009), whereas each square in Australia represents the number of bounties in a 100-by-100km area (collated from 1951 to 1952). Top predators are in a–c. Mesopredators are in d–f. Darker colours within each hunting unit indicate greater bounty return numbers and, by inference, a higher abundance for the respective predator. Dashed black lines indicate top predator range edges. Australia was divided into two sections for the analysis (east and west) as shown.

The results, which were consistent across the three continents, suggest that top predators can suppress mesopredators effectively (even completely) but only in the core of their geographic range, where their numbers are highest.

In other words, abundant top predators can exert disproportionate mesopredator control once their numbers increase past a certain point.

Example of the results from Australia (western side of Queensland). The blue lines indicate the abundance of each predator (note that the values on the y-axis are scaled so do not reflect actual numbers). The black dashed line indicates where there is a sharp change in predator abundance (the breakpoint). The red dashed lines indicate 95% confidence intervals (a measure of uncertainty) either side of the breakpoint. Distance values less than zero relate to areas outside the dingoes’ range, while distance values greater than zero relate to areas within the range. In summary, abundances of the red fox decline sharply as you move further into the range of the dingo.

The ‘enemy constraint hypothesis’

The relationship we uncovered is now formalised as the “Enemy Constraint Hypothesis”. It could apply to other predator dyads, where two animals compete for similar resources – even relationships involving parasites and pathogens.

Our findings are important for understanding species interactions and niches, as well as the ecological role of top predators. It could explain why other studies have found top predators have little influence on mesopredators: they were looking at the edge, not the core, of the top predators’ range.

This is a conceptual model of the Enemy Constraint Hypothesis. On the edge of a top predator’s range, mesopredator abundance should decline as top predator numbers increase. The breakpoint for the mesopredator indicates where their population nears zero. The breakpoint for the top predator indicates where their abundance starts to decline sharply on the edge of the range.

How many top predators do we need?

Dingoes can be vital for reducing red fox and possibly feral cat numbers. In our case studies the ranges of each top predator were limited primarily by human use of the land and intensive shooting, trapping and poisoning.

Killing pack animals like dingoes can fracture social groups, potentially altering their natural behaviour and interactions with other species. Future studies on predator interactions therefore need to consider the extent to which the animals are acting in response to human intervention.

If we want to benefit from the presence of top predators, we need to rethink our approach to management – especially where they are subjected to broad-scale control, as the dingo is in some parts of Australia.

The ConversationChanging our relationship with top predators would not come without its challenges, but high extinction rates around the world (and especially in Australia) clearly indicate that we urgently need to change something. If this includes restoring top predators, then we need to think big.

Thomas Newsome, Fulbright Scholar and Postdoctoral Research Fellow, Deakin University

This article was originally published on The Conversation. Read the original article.

Maybe we can, but should we? Deciding whether to bring back extinct species



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Immortalised on a stamp, New Zealand’s stout-legged wren went extinct in the 1990s.
Boris15/www.shutterstock.com

Gwenllian Iacona, The University of Queensland and Iadine Chadès, CSIRO

De-extinction – the science of reviving species that have been lost – has moved from the realm of science-fiction to something that is now nearly feasible. Some types of lost mammals, birds or frogs may soon be able to be revived through de-extinction technologies. The Conversation

But just because we can, does it mean we should? And what might the environmental and conservation impacts be if we did?

Prominent conservation biologist Stuart Pimm has been one of the vocal opponents of de-extinction because, among other concerns,

Without an answer to “where do we put them?” — and to the further question, “what changed in their original habitat that may have contributed to their extinction in the first place?” — efforts to bring back species are a colossal waste.

These are valid concerns, and difficult to consider in light of the many competing factors involved.

We’ve recently outlined a deliberate way to tackle this problem. Our new paper shows that an approach known as “decision science” can help examine the feasibility of de-extinction and its likely impact on existing environmental and species management programs.

Applied to the question of possible de-extinction programs in New Zealand, this approach showed that it would take money away from managing extant (still alive) species, and may lead to other species going extinct.

Solving complex problems

The potential to reverse species extinction is exciting from both a science and a curiosity perspective. But there is also great concern that in the passionate rush to implement new technology, we don’t properly consider environmental, economic and social issues.

Balancing these multiple objectives requires decision makers to understand how various project endpoints relate to all the different project goals.

Decision science methods simplify complex problems into parts that describe the benefit, cost and feasibility of the different possible solutions. They allow for “apples to apples” comparisons to be made about different but essential aspects of the projects being considered.

Decision science in action

When applied to de-extinction projects, decision science lets researchers:

  • compare different possible outcomes of de-extinction approaches
  • better understand future expected costs and benefits, and
  • see impacts of using de-extinction technology on other species that we care about.

New Zealand and New South Wales are home to more than 1,100 threatened species of conservation concern between them.

Over the past decade their management agencies have built on a decision science approach to prioritise their conservation efforts, and increase the number of species they are able to put on the road to recovery.

New Zealand in particular is a prime candidate for considering de-extinction because they have had many recent extinctions, such as the huia.

The New Zealand native bird ‘huia’ went extinct in 1907.
Photographed by Kendrick, J. L. and with thanks from NZ Department of Conservation, Author provided

These lost species fit many of the criteria for species appropriate for de-extinction technologies.

A recent study took the process that was developed to rank New Zealand species according to priority for action, and included 11 possible candidates for de-extinction in the ranking process. These were birds, frogs and plants, including the little bush moa, Waitomo frog and laughing owl.

By applying a decision science process, the authors found that adding these species to the management worklist would reduce their ability to adequately fund up to three times the number of currently managed species, and essentially could lead to additional species going extinct.

The study also showed that private agencies wishing to sponsor the return of resurrected extinct species into the wild, could instead use the money to fund conservation of over eight times as many species, potentially saving them from extinction.

Crucially, this study could not examine the initial costs of using genetic technology to resurrect extinct species, which is unknown but likely to be substantial. If it could have included such costs, de-extinction would have come out as an even less efficient option.

The laughing owl went extinct in New Zealand in 1914.
Photographed by Kendrick, J. L. and with thanks from NZ Department of Conservation, Author provided

Could de-extinction ever be the right option?

The New Zealand example is not a particularly rosy picture, but it may not always be the case that de-extinction is a terrible idea for conservation.

Hypothetically, there are situations where the novelty and excitement of a de-extinct species could act as a “flagship species” and actually attract public interest or funding to a conservation project.

There also is an interesting phenomenon where even just the possibility of having a management action such as de-extinction may change how conservation problems are formulated.

Conservation management currently aims to do the best it can, while operating under the constraint that biodiversity is a non-renewable resource. With this constraint we can apply theory that is used for managing the extraction of non-renewable resources like oil or diamonds to determine the best strategy for management.

However, if extinction was no longer forever, the problem could be considered as one that would be managing a renewable resource, like trees or fish.

Of course, the ability to revive species is nowhere near as simple as regrowing trees, and a species being revived does not necessarily equate to conservation.

But changing the way that conservation managers think about the problem could present conservation gains in addition to losses.

Theoretically, different methods may be used for conservation benefit and there may be different strategies to produce the best outcomes. For example, species that could easily be de-extinct may get less funding attention that the ones for which the de-extinction technology isn’t available, or are too costly to produce.

This research does not advocate for or against de-extinction, rather, it provides strategies to deal with alternatives from the start with a clear representation of the trade-offs.

This work aims to step back and take a realistic look at the implications of new technology, including its costs and its risks, within the context of other conservation actions. Decision theory helps to do just that.

Gwenllian Iacona, Postdoctoral Research Fellow, The University of Queensland and Iadine Chadès, Leader of the Conservation Decisions Team and Senior research scientist, CSIRO

This article was originally published on The Conversation. Read the original article.

The lengthy childhood of endangered orangutans is written in their teeth



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A young Bornean orangutan nursing.
Erin Vogel, Author provided

Tanya M. Smith, Griffith University

Orangutan populations in the wild are critically endangered, and one of the things that may hamper their survival is the time they take to rear new offspring. The Conversation

An orangutan mother will not give birth again until she’s finished providing milk to her previous offspring. Nursing can take a long time and vary across seasons, as we found in research published today in Science Advances.

Primate mothers, including humans, raise only a few slow-growing offspring during their reproductive years.

Differences in infant development have a profound effect on how many children a female can have over the course of her life – the key marker of success from an evolutionary vantage point.

Great apes have a high-stakes strategy. Chimpanzee mothers nurse their offspring for five years on average, twice as long as humans in traditional small-scaled societies.

Orangutans have been suspected of having even longer periods of infant dependency, although determining just how long has been a particular challenge for field biologists.

Wild orangutan from Gunung Palung National Park, Borneo, Indonesia with her one month old infant. (Gunung Palung Orangutan Project)

Living high up in dwindling Southeast Asian forests, these apes are adept at evading observers. Their nursing behaviour is often concealed, particularly while juveniles cling to their mother or rest together in night nests.

Maintaining continuous field studies to track their development is expensive, and efforts are hindered by frequent forest fires and devastating deforestation for palm oil plantations.

Teeth tell the story

I have spent the past few decades studying how orangutans and other primates form their teeth. Amazingly, every day of childhood is captured during tooth formation, a record that begins before birth and lasts for millions of years.

Teeth also contain detailed dietary, health and behavioural histories, allowing biological anthropologists an unprecedented window into the human past.

I’ve also teamed up with researchers Manish Arora and Christine Austin, at Icahn School of Medicine at Mt Sinai in New York, who have pioneered methods to map the fine-scaled elemental composition of teeth, as well as primate lactation expert Katie Hinde at Arizona State University.

We have shown in a previous study that tiny amounts of the element barium are an accurate marker of mother’s milk consumption. Like calcium, barium is sourced from the mother’s skeleton, concentrated in milk, and ultimately written into the bones and teeth of her offspring.

Tooth growth creates daily lines (indicated by short white lines), as well as a neonatal line (NL) at birth. Growth starts at the junction between enamel and dentine, and progresses away from the junction and towards the root (arrows).
Christine Austin and Tanya Smith

Once animals start nursing after birth, their teeth show increases in barium values, which begin to decrease when solid food is added to the diet. These values drop further to pre-birth levels when primates stop nursing and are weaned.

We’ve recently used this approach to explore the nursing histories of wild orangutans in collaboration with orangutan expert Erin Vogel at Rutgers University. In order to do so, I borrowed teeth housed in natural history museums from individuals that had been shot many years ago during collection expeditions.

Wild Bornean orangutan mother and suckling 19-month old infant.
Paige Prentice, Author provided

Orangutan teeth show a gradual increase in barium values from birth through their first year of life, a time of increasing consumption of their mother’s milk. After 12-18 months, values decrease as infants begin eating solid foods consistently.

But surprisingly, barium levels then begin to fluctuate on an approximately annual basis. We suspect that this is due to seasonal changes in food availability. When fruit is in short supply, infants appear to rely more on their mother’s milk to meet their nutritional needs.

Light microscope image (left) of a wild orangutan molar contrasted with an elemental map of the same tooth (right) showing the distribution of barium. The timing of barium incorporation was determined from accentuated lines (in days of age on the left), which form during enamel and dentine secretion. Approximately annual bands of enriched barium are apparent in the dentine after the first year, likely due to seasonal increases in mother’s milk intake.
Smith et al. (2017) Science Advances

Hanging around

Another surprising finding is that nursing may continue for more than eight years, longer than any other wild animal.

This information is the first of its kind for wild Sumatran orangutans, as they have been especially difficult to study in their native habitat. Previous estimates from two wild Bornean orangutans suggested that juveniles nurse until about six to eight years of age.

Rather than spending so much time and energy breastfeeding their children, human mothers in traditional societies transition their infants onto soft weaning foods around six months of age, tapering them off milk a few years later.

Humans also benefit from having help such as older siblings and grandparents who lend a hand with childcare and enable women to energetically prepare for having their next child.

Orangutan mothers have it hard by comparison. They live alone in unpredictable environments with limited nutritional resources. In order to survive they use less energy than other great apes, raising their young more slowly.

Wild orangutan mother and 11-month old infant.
Tim Laman, Author provided

Vulnerable orangutans

Female orangutans begin reproducing around age 15 and can live until 50 years old in the most favourable of circumstances. They bear new offspring every six to nine years, producing no more than six or seven descendents over their lifetime.

Having a long nursing period and slow maturation makes orangutan populations especially vulnerable to environmental perturbations.

Recent work has also implicated poor habitat quality and the pet trade as additional factors in their rapidly declining numbers, which is underscored by their critically endangered status.

Research on collections housed in natural history museums provides timely evidence of how remarkable orangutans are, how much information we can retrieve from their teeth, and why conservation efforts informed by evolutionary biology are critical.

Tanya M. Smith, Associate Professor in the Australian Research Centre for Human Evolution, Griffith University

This article was originally published on The Conversation. Read the original article.