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.
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.
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.
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.
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.
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.
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.
Tim Doherty, Deakin University; Aaron J. Wirsing, University of Washington; Chris Dickman, University of Sydney; Dale Nimmo, Charles Sturt University; Euan Ritchie, Deakin University, and Thomas Newsome, Deakin University
Humans and their canine companions share many close bonds. Wolves (Canis lupus) were the first animal domesticated by people, some time between 15,000 and 50,000 years ago.
There are now an estimated 1 billion domestic dogs across their near-global distribution.
Domestic dogs include feral and free-ranging animals (such as village and camp dogs), as well as those that are owned by and completely dependent on humans (pet dogs).
Our latest research reveals that the ecological “pawprint” of domestic dogs is much greater than previously realised.
Using the IUCN Red List of Threatened Species, we counted how many species are negatively affected by dogs, assessed the prevalence of different types of impacts, and identified regions with the greatest number of affected species.
We found that dogs are implicated in the extinction of at least 11 species, including the Hawaiian Rail and the Tonga Ground Skink. Dogs are also a known or potential threat to 188 threatened species worldwide: 96 mammal, 78 bird, 22 reptile and three amphibian species. This includes 30 critically endangered species, two of which are classed as “possibly extinct”.
These numbers place dogs in the number three spot after cats and rodents as the world’s most damaging invasive mammalian predators.
Even though dogs have an almost global distribution, the threatened species they are known to affect are concentrated in certain parts of the globe. South-East Asia, South America, Central America and the Caribbean each contain 28 to 30 threatened species impacted by dogs. Other hotspots include Australia, Micro/Mela/Polynesia and the remainder of Asia.
Predation was the most commonly reported impact of dogs on wildlife. The typically omnivorous diet of dogs means they have strong potential to affect a diversity of species. For instance, dogs killed at least 19 endangered Kagu (a ground-dwelling bird) in New Caledonia in 14 weeks. Threatened species with small population sizes are particularly vulnerable to such intense bouts of predation.
Aside from simply killing animals, dogs can harm wildlife in other ways, such as by spreading disease, interbreeding with other canids, competing for resources such as food or shelter, and causing disturbances by chasing or harassment. For example, contact with domestic dogs increases disease risk for endangered African Wild Dogs in Kenya.
Part of the problem is that when wild animals perceive dogs as a threat, they may change their behaviour to avoid them. One study near Sydney found that dog walking in parklands and national parks reduced the abundance and species richness of birds, even when dogs were restrained on leads.
None of the Red List assessments mentioned such indirect risk effects, which suggests that their frequency is likely to be much higher than reported.
Despite their widespread and sometimes severe impacts on biodiversity, dogs can also benefit some species and ecosystems.
For example, in Australia, the closely related dingo (Canis dingo) can suppress populations of introduced predators such as red foxes (Vulpes vulpes), and in doing so can benefit smaller native prey. It is possible that domestic dogs could perform similar ecological roles in some situations.
Dogs not only interact with wildlife, but can also attack and spread disease to humans, livestock and other domestic animals. As such, managing the problem requires looking at ecological, cultural and social perspectives.
Some of the regions with high numbers of species threatened by dogs are also hotspots for urbanisation and road building, which make it easier for dogs to access the habitats of threatened species. Urban development increases food waste, which feeds higher numbers of dogs. As dogs expand into new areas, the number of species they impact is likely to grow.
We can protect wildlife by integrating human health and animal welfare objectives into dog management. Vaccination and desexing campaigns can reduce disease risk and overpopulation problems. We should also focus on responsible dog ownership, removing dogs without owners, and reducing access to food waste.
Given the close relationship between humans and dogs, community engagement should form the basis of any management program. More research is needed to get a better picture of the scale of the problem, and of how dogs interact with other threats such as habitat loss. Such actions are critically important for ensuring the conservation of wildlife threatened by dogs around the world.
This article was co-authored by Dr Al Glen from Landcare Research, New Zealand and Dr Abi Vanak from the Ashoka Trust for Research in Ecology and the Environment, India. These institutions had no role in the design or funding of this research.
Tim Doherty, Research Fellow, Deakin University; Aaron J. Wirsing, Assistant Professor, School of Environmental and Forest Sciences, University of Washington; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Dale Nimmo, ARC DECRA Fellow, Charles Sturt University; Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Thomas Newsome, Fulbright Scholar and Postdoctoral Research Fellow, Deakin University
There a many reasons to be unhappy about the state of the environment. But we’ve recently found some good news: a conservation program that works.
You probably haven’t heard of the Environmental Stewardship Program (ESP). It was a market-based agri-environment program that ran between 2007 and 2012, which funded farmers to conserve threatened ecosystems on their property. Land managers were given contracts for up to 15 years to deliver results.
Overall, 297 land managers will receive about A$152 million over roughly 18 years to implement their conservation management plans. The last of these contracts will end in 2027. No new funding rounds are expected.
There’s been a variety of market-based programs for conservation on farmland in Australia, but we don’t know what the total investment is to date. And we are not aware of scientific monitoring that demonstrates their impact.
The box gum grassy woodlands of eastern Australia are home to several hundred species of native birds, including the iconic superb and turquoise parrots, thousands of native plants (such as the chocolate lily that leaves a deliciously rich and sweet aroma in native pastures), and beautiful mammals like the squirrel glider.
Box gum grassy woodlands have been 95% to 99% cleared for wheat and sheep grazing and are listed as nationally critically endangered.
Under the ESP, more than 150 farmers from southern New South Wales to southeast Queensland have been funded to conserve the box gum grassy woodland ecosystem. This is one of the largest projects of its type in the world.
Farmers undertake controlled grazing by livestock in woodland remnants, replant native woodland, avoid firewood harvesting, cease bushrock removal, and control weeds and feral animals.
But we can’t know if a conservation program is working unless we monitor it. Fortunately, soon after it started, the Australian National University was commissioned to design a monitoring program for the ESP. We have now been monitoring these efforts for six years – and the results are exciting.
So far, the data show that the farmers are doing a good job and it is money very well spent.
To find out if the program is working, we have to compare managed (conserved) areas with “control patches” – patches where land owners haven’t done anything. This comparison shows that funded management patches have fewer environmental weeds, greater native plant species richness, more natural regeneration of native plants, smaller areas of erodible bare ground, and more species of woodland birds.
In the space of six years, the Australian government, in concert with Australian farmers (through modest investment), has generated significant, positive environmental changes on farms. In fact, the box gum project can set the bar for many other conservation programs.
The positive impacts go beyond improvement of the environment, because there have been notable social benefits too.
Farmers are now highly motivated to deliver better environmental outcomes on their farms and showcase the integration of the multiple objectives of agricultural production and conservation.
The income stream they received also helped some survive the almost unprecedented hardships associated with the Millennium Drought in the mid- to late 2000s.
More generally, regular feedback and discussions between ANU field ecologists and landholders over the past six years has provided anecdotal evidence that farmers engaged in successful environmental programs suffer fewer problems with mental illness. This landholder goodwill and change in attitude towards land management is something that will far outweigh the 15-year investment in the program.
Despite its success, the program has not been without detractors who see the policy and monitoring as over-engineered or boutique. This is primarily because its design, implementation, and monitoring standards are politically and bureaucratically inconvenient. They are not well suited to a reactive, short-term focused society.
In the case of monitoring, some considered it wasteful to establish and monitor control sites (areas where there has been no management). Yet without the controls, we couldn’t tell this positive story.
This is an exciting example of successful private-public land conservation and how it can be integrated with agricultural production (the primary land use of much of Australia’s land surface).
The long-term funding model is a more sensible approach than one-off payments, and provides a realistic timeframe to achieve results.
The Australian government should be congratulated and encouraged to invest in more programs of this type. It has worked because it was designed specifically to link farmers, scientists and policy makers.
Billions of dollars are expended on the environment in Australia every year. Landscape recovery will span multiple governmental cycles and every dollar must be spent wisely. Programs like ESP give some guidance on how large-scale environmental programs can be more successful.
For further information on conservation programs like the Environmental Stewardship Program, see our new e-book
David Lindenmayer, Professor, The Fenner School of Environment and Society, Australian National University; Chloe Sato, Postdoctoral fellow in applied vegetation ecology, Australian National University; Dan Florance, Research officer, Fenner School of Environment & Society ANU College of Medicine, Australian National University, and Emma Burns, Executive Director, Long Term Ecological Research Network; Fenner School of Environment and Society, Australian National University
The link below is to an article that looks at the world’s most endangered primates.
An American trophy hunter has kicked off another social media furore after defending a recent giraffe kill in South Africa by claiming they were “very dangerous animals”. In one sense she is right – giraffes are big and strong and you certainly wouldn’t want one kicking you. But attacks on humans are very rare.
A more relevant question is whether hunting is a key threat to giraffes.
The International Union for the Conservation of Nature (IUCN) Red List assessment does not list legal hunting as a threatening process at all. However illegal hunting for meat and trophies is listed as threatening as it reduces the effective size of their protected areas and, if allowed to proceed unchecked, can cause the collapse of wildlife populations. Giraffes are popular among bushmeat poachers because of their size, high meat yield and the ease with which they can be hunted.
The giraffe is currently listed as “least concern” on the IUCN Red List, but this doesn’t present the full picture. Back in 1999 wildlife expert Rod East estimated there were 140,000 in Africa – today the Giraffe Conservation Foundation estimates there are only 80,000 left. Such a rapid decline suggests they may soon qualify as being vulnerable to extinction.
But why does a 40% drop in giraffe numbers not resonate worldwide? After all, everyone knows African elephants are threatened yet there are still 500,000 left in the world. So why is the giraffe being ignored?
Normally, it is the uncharismatic species that decline without much public sympathy, but that doesn’t apply here. Giraffes are one of the megastars of the African savannah. Tourists love them. Children who have never been to Africa know what a giraffe looks like. It is the world’s tallest animal despite having the same number of bones in its neck as we do. It is almost comical in appearance with its orange dappled pyjama onesie – although when you feel it, giraffe skin is thick and tough.
A drive through a well-managed protected area, such as Kruger National Park in South Africa, gives the impression that both elephants and giraffes are secure. You can sit at a waterhole and watch elephants cavorting in the water while a lone giraffe browses peacefully on the acacias nearby. In Zimbabwe’s Hwange National Park I once saw 32 giraffes without even turning my head. It could be that this familiarity has blinded society to the decline of the species, in addition to a lack of well-publicised trafficking busts that occurs with elephant ivory or rhino horn.
But the rapid decline of giraffes isn’t the only story – because in southern Africa, populations are increasing. A major reason for this increase has been the development of wildlife ranches and the reintroduction and protection of giraffes on those lands. There are significant numbers on wildlife ranches in South Africa, Botswana, Zimbabwe, and a recent study estimated that 23,000 giraffes occupy such lands in Namibia.
Ironically, many of those ranches only developed because there was potential for deriving income from trophy hunting, including giraffes. Elsewhere, though, other sub-species are faring far worse. The reticulated giraffe from Somalia, Kenya and Ethiopia has been reduced to just 5,000 individuals through illegal poaching and war. The West African giraffe in Niger had only 50 animals in the mid-1990s, but robust environmental protection has resulted in an increase to around 400 today.
The taxonomy of giraffes is currently being studied, and it may be that the dozen or so giraffe sub-species are elevated to distinct species, which would totally reform their conservation status assessments.
It seems clear that to protect giraffes, we need to prevent both habitat loss and illegal hunting. These targets can be achieved through adequate management of protected area estates and through the creation of incentives for conservation on lands outside of protected areas. Trophy hunting contributes to both in some countries by generating income from and for wildlife.
The controversy over the killing of Cecil the lion highlights how much is needed to make sure legal hunting industries are adequately managed. However, until an alternative to the income from trophy hunting is found, the answer lies not in banning the practice or on clamping down on trophy imports, but in helping African countries manage the industry better.