By Shermin de Silva
In the beginning…
Your jeep rolls up to a long lift-gate that swings up to reveal a seemingly vast grassland. The dirt track, just wide enough to fit two vehicles side-by-side, snakes along between the tall grass then branches off – to the left opens out an immense reservoir. When full, it resembles a good-sized lake. When empty, its banks grow a lush cover of short grass. Elsewhere, trees dot the landscape, with larger patches of forest here and there. This environment resembles what most of us might imagine to be an African savanna. Except, it’s in Sri Lanka. And the elephants that roam here are small-eared, shy, and nearly disappear into the tall grass.
This was Udawalawe National Park when we first started our work in 2006. The result of large-scale changes in the landscape brought about by the damming of the Walawe river, which cuts through the center of the park. Originally a tropical deciduous forest (also misleadingly known as tropical “dry” forest, despite the seasonally heavy monsoon rains), the grassland is what remains after plantations, agriculture, and small settlements cleared the area following governmental irrigation schemes. At the time, it was a haven for species that thrived in these grassy ecosystems – not only elephants, but also deer, large birds of prey and smaller open-habitat species, small lizards and star tortoises, countless insects, even leopards and jackals.
The elephants moved lazily through this ocean of grass. They were mostly in small groups of 1-3 adult females, along with their calves. Males also wandered about, usually solitary but for brief engagements with females or one another. But not infrequently there were larger groups, especially in dry seasons when they came out onto the open banks of the reservoir, or if there was an especially good patch of freshly sprouting grass following a fire. We noticed early on that females in this population shuffled around their companions quite a bit, but over time we could recognize that many belonged to social groups. Though we rarely, if ever, saw the groups in their entirety, we could tell that some individuals “belonged” together and that they didn’t always accept strangers into their midst, using subtle signals of dominance or avoidance to ensure there was no direct conflict or aggression.
Fast forward a little over a decade later, and we would still see the elephants going about their business much as they always had, in small groups of females and calves with males scattered about. On the surface, it would appear nothing had changed. But looks can be deceiving, and only a long-term perspective would reveal the surprising transformation that had taken place. As we report in our new study in the journal Science, led by postdoctoral researcher Anastasia Madsen together with the de Silva lab at UC San Diego and the Udawalawe Elephant Research Project, the elephant population seemed to have undergone a dramatic demographic and social transition.
A social tipping point follows a demographic tipping point
Although Udawalawe hosted north of a thousand elephants, which could be seen in the park all year round, we documented in multiple studies that the population actively circulated in and out of the national park (see here and here). While some elephants might have been resident, these were perhaps just a quarter of the whole population. There were always “new” individuals, who might have been immigrants (adults and groups that we had never seen before) as well as subadult females who were maturing to adulthood. There was also always death and emigration, through which individuals were lost. Between 2006-2012 the net balance of individuals coming into the population vs. those leaving the population was positive – there were more coming in than permanently going out. But the trendlines had been going in opposite directions and after 2012 this balance became negative. By 2018, in just 12 years, we had lost nearly 70% of the adult females who had been identified at the outset of the study.
This turned out to be a critical threshold, or tipping point, triggering a change in the social organization. We constructed social networks to represent these relationships, where nodes represent individual females and the lines connecting them, termed “edges,” represent social relationships. The thickness of these lines represents how often a pair is seen together, a proxy for the strength of their social bond. When we constructed social networks for each year, we saw something that made us catch our breath. Although we didn’t see much change in the group sizes we observed on a day-to-day basis, the formerly large and well-connected social communities had suddenly fragmented. They had crossed what we termed a “social tipping point”.
At the scale of the whole population (443 females), this happened immediately after the trendlines crossed. But what was more surprising, was that it also happened among the “residents,” (59 females), albeit a few years later. The “residents” were females who had been seen in every year of the study (though they too likely roamed outside the park).
This means that the fragmentation wasn’t simply a result of numerical loss in the population, even relationships among remaining individuals were being re-arranged. Weaker relationships were most likely to be lost or changed, whereas intermediate or strong relationships were preserved and sometimes even strengthened.
Indeed, when we looked more closely at how relationships among pairs of individuals were changing (termed “rewiring”) we saw that a large number of edges were being simply lost because individuals were disappearing. But there was also a substantial fraction of edges that got reshuffled among individuals who continued to be present all throughout. This means that there was either an indirect effect of these losses (e.g. if certain adults who disappeared acted as social glue) or some other factor that was affecting both sets of individuals.
Interestingly, a network property we termed “isolation” showed a spike before communities fragmented. Isolation is a measure of the proportion of relationships within a social unit as opposed to between units. The greater this proportion, the more isolated they are. This spike signals that social groups were first disconnecting from one another before further fragmenting themselves.
So, what happened?
Watching the elephants over this time, we could see the demographic changes taking place. Already in 2019, we published a study suggesting that the population might be in decline, but we didn’t know at the time whether it would be long-term. And although we have not yet conducted formal population estimates, I was surprised when some of our prime-aged females started dying or disappearing.
These were individuals who were reliably seen year to year and seemed in good shape, like Amali, who was the very first female in my catalogue in 2005 – ID number 001. Amali was hefty and stocky, along with her constant companion Rinkle. They were built like tanks. Their social groups had always had a lot of calves bouncing around.
That was no longer the case. The calves being born lately were looking thin and malnourished. The females themselves looked weaker with each passing year, ribs and backbones showing. Calves can also be an important social attractor, as seen in sperm whales. A very new study in Southern India has also found that calves act as social “magnets”. Perhaps there were simply not enough calves being produced around which social groups might form in our population.
A young female named Jasmine illustrates this process of social isolation and the possible roles of both elders and calves.
As we described in an earlier post, Jasmine had been loosely associated with a group we named with the letter “J”. The J’s were a seasonal group, known to range outside the park through the eastern corridor. An elder female named Janet, who we thought might be her mother, had been Jasmine’s close companion. But after Janet passed away, Jasmine seemed become more distant from her former companions, though she was still with them from time to time. She was not seen to produce a calf in ten years. Perhaps it was Janet’s death that precipitated Jasmine’s social separation, but the lack of any calves might have contributed to her remaining mostly on her own. This isolation might have become a liability. Sadly, Jasmine was shot and killed in 2022 while on the edge of the corridor connecting Udawalawe to a neighboring sanctuary, a place where she should have been safe.
We have little idea what consequences the social fragmentation itself might have. For instance, as one study suggests, larger cohorts of calves might be more resistant to viruses that are often fatal in captive populations (acquiring a sort of herd immunity, quite literally). Calves also need a social environment to learn life skills such as what to eat and where to go. And mothers need help taking care of calves so they can conserve their energy and focus on feeding.
As you might wonder, what is the underlying reason for these processes? Quite possibly, it is the changing environment itself. The windy, rippling grassland had all but disappeared by 2018 and much of the park was dotted with shrubs and small trees. A substantial portion of it had also been taken over by invasive species, including lantana camara. The original grasslands had been the result of forest clearing and cultivation. Absent these activities, the park was slowly returning to its original forested state – but with an understory of invasive species that were not eaten by elephants or many other herbivores. This gradual depletion of food might act in two mutually reinforcing ways – it can reduce the survival of elephants who are already present and limit the attractiveness of the park to any newcomers who at one time might have circulated through.
Dismantling the Ship of Theseus
The ‘Ship of Theseus’ paradox asks whether a ship whose planks are gradually replaced one by one remains the same ship. This classical philosophical challenge asks how some things can change while also remaining the same in some significant and meaningful way. Social communities are much the same. Societies are ever in flux. But how much change in its constituent members can a community withstand?
Stepping back a moment, think of your social relationships. You probably have some people you see and interact with all the time, and others with whom you spend less time. For humans, it’s not obvious that more time together necessarily means a stronger or more meaningful social relationships – after all, I might lecture to a classroom of over 200 students on a regular basis but don’t have personal relationships with any of them. On the other hand, I see my friends and family far less frequently, but these relationships are the most precious and valued.
We might think the same is true of other species, but think again. We can use technology to overcome the lack of physical proximity to some extent. But this doesn’t mean physical proximity isn’t important – as anyone who has ever tried to maintain a long-distance relationship can tell you. For non-human animals, being physically together is even more critical – a social relationship is necessarily also a spatial relationship. As the environment has changed, it has also become more difficult to move in and out of the park. Multiple encroachments on corridors that connect the park to other areas, infrastructure developments, and land-use changes have been a constant challenge for the elephants to negotiate. An important lesson from this study, equally applicable to us, is that it’s important to be able to replace the social companions we lose in our lives.
Elephants evolved to live long lives and breed relatively slowly, so they cannot tolerate too much mortality among calves or breeding-aged females. But what we’re seeing here is that the effects of demographic turnover can also be more so subtle as to be unnoticeable on the ground. These social changes were not evident until we wrangled many years of data (laborious, resource intensive to collect) – a process that took several years in itself. This highlights a source of constant tension between science and on-the-ground conservation. Careful rigorous science often just moves too slowly to command attention and provide warnings in real-time. At the very least, for highly social species, we have to grapple with the possibility that simply counting the numbers (which is hard enough) is not enough. It will never be practical to monitor every elephant population, or indeed many species, in this way. So we urge a precautionary approach to intervene at the first sign of trouble. We cannot take these populations for granted any longer.
What’s next for us?
First, we want to drill down to the level of individuals and see exactly why certain relationships changed. We’re also not giving up on the Udawalawe elephants. One thing that’s been obvious for a while is that protected areas alone are inadequate for supporting elephant populations. Unless national parks are actively managed to mimic the disturbance patterns (clearing, weeding, burning) that created these ideal elephant ecosystems in the first place, there will likely be better habitat for elephants outside protected areas. But it can be dangerous, especially for the shy elephant herds that would rather prefer to avoid humans altogether. So for several years now our Coexistence Project has been working to trial elephant-resistant crops with farming communities around the perimeter of the park.
To us, neither the elephants nor the people are simply numbers on a spreadsheet – relationships matter, for all of us. We are hopeful that these agricultural lands can be more than a source of conflict: perhaps they will be the key to elephants’ survival in this landscape.
Only time will tell.
Want to do your part for conservation?
Here are some actions you can take:
- Support this work through Trunks & Leaves.
- A large share of our work was funded by the US Fish & Wildlife Service. These grants, known as the Multinational Species Conservation Funds, which have provided crucial support for many other conservation programs around the world, were suspended in 2025. The lead researcher, Anastasia Madsen, was supported by an NSF Postdoctoral Fellowship in Biology, which is threatened by changing priorities and cuts to science funding in the United States. Write to your congressional representative and urge them to work toward restoring these funding sources.
- Learn more about conservation efforts at Trunks & Leaves.org and the de Silva lab’s other research at elephantresearch.net
- Be a responsible consumer and an ethical traveler, knowing that your choices affect species and ecosystems half a world away.
- Last but not least, subscribe to updates below. Thanks!
References
Madsen, A.E., Pushmapkumara, T.V., Weerathunga, S.A., Weerakoon, D.K., de Silva, S. 2026. “Increased demographic turnover and isolation precede social fragmentation in Asian elephants”. Science 394,792-798(2026).DOI: 10.1126/science.aef6714
Madsen, A.E., C. Minge, T.V. Pushpakumara, et al. 2022. “Strategies of protected area use by Asian elephants in relation to motivational state and social affiliations.” Scientific Reports 12, 18490. DOI: 10.1038/s41598-022-22989-1
de Silva, S. and Leimgruber, P., 2019. Demographic tipping points as early indicators of vulnerability for slow-breeding megafaunal populations. Frontiers in Ecology and Evolution, 7, p.171. dOI: 10.3389/fevo.2019.00171
Hoornweg, T. E., Perera, V. P., Karunarathne, R. N., Schaftenaar, W., Mahakapuge, T. A., Kalupahana, A. W., … & De Haan, C. A. (2022). Young elephants in a large herd maintain high levels of elephant endotheliotropic herpesvirus‐specific antibodies and do not succumb to fatal haemorrhagic disease. Transboundary and emerging diseases, 69(5), e3379-e3385. DOI: 10.1111/tbed.14644
