Spotlight Amboseli: Elephant social relationships – both long and short terms matter
Some of the readers of this blog have commented on my evident enjoyment of my job. I’m glad it’s so obvious, and it’s true that anyone would be thrilled and privileged to spend so much time with the Amboseli elephants. Although there are some frustrations, there are few things more relaxing than spending time with a peacefully foraging elephant family in the quiet of an Amboseli afternoon.
For me as a researcher, more than the simple delight of spending time with elephants is the privilege of access to the Amboseli dataset. This is the longest running study of wild elephants anywhere in the world. For four decades, Dr. Cynthia Moss and the rest of the team have collected information about births, deaths, social relationships, genetics and behaviour. Every day we are in the field adds to the dataset, but maintaining and using these data is also a full-time job. After all, there is very little point spending thousands of man hours and dollars collecting years and years of information if it all rests in notebooks or computers, and isn’t used to help advance our understanding of elephants, protecting them and their habitats.
My first task when I started at Amboseli was to learn to identify all the elephants, and to learn how data is collected and organised in the project. Some of the questions we are trying to answer in this IFAW-supported social disruption study will be addressed by these data; such as which elephants are spending time together and the births and deaths that occur in the population.
We also had to decide out what other data we would need and how it should be collected. Thanks to Cynthia and the rest of the team, we already know a lot about the Amboseli elephants. My task was to focus in on the kind of the behaviour that reveals most about the relationships between females in a family.
Elephant society follows a fission-fusion pattern, similar to that of humans; family membership is constant over time, but family members are not always together. The degree of closeness between family members varies between families, and between individual females. Elephant social relationships are built on the value of individuals.
Knowing this, we decided that we had to restrict our data collection somehow. Interactions between animals can happen very fast, and you need to be able to track and monitor the location of everyone in the group. This isn’t possible for animals that you don’t know very well – I have to be able to look up from my notebook and know where everyone is instantly, as well as read the behaviour of the elephants. It’s also important to anticipate, to some extent, what the group is going to do next, to manoeuvre our vehicle into an appropriate position (and believe me, trying to identify elephant backsides gets old very quickly). Getting to know the elephants, and getting a feel for the families, was therefore a crucial next step.
We selected twelve study families who form the basis for our detailed data collection. These families suffered a mixture of fortunes in the 2009 drought. Some of them did reasonably well, others were devastated. Some of them, like the GB family, have already radically changed their family lives as a result of the drought and the losses they experienced; other families are in the process of change.
Previous research at Amboseli has shown that older females are better at discriminating threats, and responding appropriately to keep their families safe. These elegant playback experiments conducted by our colleagues Drs. McComb and Shannon played lion roars to families, to simulate a threat to the family. Our long-term data also show that families with older matriarchs have a higher reproductive output per female – that means that all the females in family have calves faster, and those calves are more likely to survive. We think this is because older females make smarter choices about where and when to move across the ecosystem. This means that everyone in the family benefits from the experience of these females, and the higher reproductive rate results because all the females are in better physical condition, and can reproduce faster. Scaling this up, this means that populations who have these older females are healthier.
So what happens when all these old, wise females die? This is exactly what happened in 2009, when 85% of the females over 50 died as a result of a terrible drought and an upsurge in poaching in Amboseli. Half of the elephant families lost their matriarchs, and some of these families lost a number of adult females too.
Although elephant families are led by matriarchs, they are not autocratic. Decisions to stay with or leave family members depend on a variety of factors, including the availability of food and the particular elephants in question. Each female is free to leave her family unit and go off by herself. It’s rare for this to happen in Amboseli, and usually lone females are either ill or in oestrus, when they get separated from their families whilst being pursued by keen males. Much more common is that families break down into smaller units composed of sisters, or mother/daughter pairs, with their dependent calves alongside. This happens when females disagree about where or how to spend their day, and is much more common in certain families than others.
Decisions about where to go are usually made by a process of consensus within the family. A resting family will usually be grouped around sleeping calves. Older females sleep standing up, often resting on one another. The waking-up process usually begins with younger adults, who stretch, yawn and shuffle about. One by one, the rest of the family will wake, and begin dust-bathing, or plucking a few mouthfuls of vegetation. Young calves are roused by a gentle nudge with the foot or trunk, which may elicit a groggy rumble of protest. Usually one female will move to the edge of the group, facing the direction she wants to travel. One by one, other females will join her, indicating their agreement. Another female might try and persuade the family to travel somewhere else, by moving to face a different direction. Disagreement is often accompanied by vocalisations, particularly contact calls. Or females might begin a greeting ceremony, to reinforce their relationship and elicit support for their choice of destination.
The matriarch is usually not part of this process, and often it appears she keeps herself quite aloof. The family does not move until she is ready, and certain females can keep the rest of the family waiting thirty minutes or more. If she agrees with the direction that has been chosen, she will move which prompts the family to begin travelling, usually with her at the rear. On the other hand, a whole period of negotiation by the rest of the family can be completely overruled when a matriarch disagrees with the destination. These are my favourite times, watching the ensuing “battle of wills”. Who wins is sometimes surprising.
This negotiation process may be repeated over the course of the day, as families change activity. The amount of time the process takes, who initiates, who responds and the outcome, all give indications of how efficiently families go through this process. We think that families who have experienced severe disruption might be less efficient, with consequences for their reproductive outputs: time spent debating with family members is time lost to feeding, socialising or resting activities.
Now I have learnt to identify the elephants, about half my time is spent with my study families, watching their negotiations. The other half is allocated to working on the long-term data. I’m exploring long-term changes in the relationships between the families, to understand what was happening in 2008 immediately before the drought which caused such upheaval. Coupling together the long-term changes with the short-term consequences will help us understand just how catastrophic the 2009 drought was for the elephants, and how it compares to previous drought events, and to the long-term variation and evolution of social relationships.
Of course, pulling together forty years of data doesn’t happen overnight. And it will be a while yet before I have enough data on the study families to begin any kind of formal analyses. But since patience is a virtue (see my last post), I’m looking forward to seeing what will happen. I’m definitely expecting a few surprises along the way.