Following in the footsteps of elephants
Imagine for a moment that you're 6,000 pounds, living in one of the wildest places on Earth, with no schedule, nowhere to be. How do you decide where to spend your time? Where to go next? Do you move where food is most plentiful? Is water your main priority?
These are some of the questions addressed by Duke Ph.D. candidate Amelia Meier and former postdoctoral researcher Dr. Chris Beirne in Dr. John Poulsen's lab. Their recent study published in Trends in Ecology and Evolution focused on the African forest elephant—the slightly smaller yet still undeniably huge cousin of the savanna elephant.
The team wanted to know what influences certain aspects of elephant behavior. Specifically, how much climate and resource availability drives elephant movement and influences their diet. To do this, the team looked at fruit abundance (a high-energy staple of elephants' diets), water availability from rainfall, and elephant identity and how those factors affect how an individual moves and eats.
One might think that such a massive animal is easy to spot in the forest. However, the dense vegetation of Central African rainforests can be an impenetrable wall, allowing the massive animals to move unseen through the forest, leaving broken branches and steaming dung piles in their wake.
To better track them, the researchers fitted individual elephants with GPS collars that turn an iPhone into an elephant-tracking tool. This also allowed trackers to follow the elephants at a distance and avoid conflict with the sometimes temperamental animals.
Meier, Beirne, and colleagues also wanted to know more about the diets of the tracked elephants to see if what they ate changed with how much fruit is available. This less-than-glamorous job was done by dissecting fresh dung piles, estimating the proportions of leafy and woody material, and counting the number of seeds in each one.
Tropical rainforests are lush, yet have patchy resources, making it important for many frugivores to have flexible diets. Some trees only produce fruit in the wet season. Others fruit every other year. To gauge fruit availability, the research team conducted "fruit-walks" at the beginning and end of each day of following an elephant, in which trackers counted all of the ripe fruit on the ground.
A key finding of the study was that the most important factor driving movement was an elephant's individuality; some respond to food or water availability differently and some simply move around more than others.
Interestingly, elephants appear to be affected by resources differently depending on the timescale the authors looked at. Water was important on both a day-to-day and month-to-month basis. Yet on a daily basis, fruit and water were more equally matched, with water still maintaining a slight lead.
Fruit availability was also critical in determining how much elephants moved and what they ate. When there was more fruit available, the elephants ate more fruit, as evidenced by the proportion of seeds in dissected dung piles.
Aside from being an awe-inspiring species, forest elephants are important to the health of their native ecosystems. They are unwitting gardeners, planting seeds of the fruits they consume in piles of dung and giving those seeds a better chance of survival. That's part of why understanding what motivates forest elephant movement is more than the satisfaction of an elephant enthusiast's curiosity; it is critical to managing and conserving a species that is vulnerable to multiple threats from humans.
Meier's dissertation research focuses on elephant social behavior and the effects of human disturbance on elephant social groups, allowing her to pursue her long-term interest in animal behavior with a practical conservation application.
"I was living in Congo and I knew I wanted to keep working in the region. There, you have elephants—this amazing, highly intelligent, social species that is surrounded by conflict."
Poachers seek elephants for their ivory tusks, which are valuable on the black market. The pachyderms are also prone to conflict with humans when they start foraging in village plantations, destroying crops and damaging livelihoods.
The team's findings open the way for new questions about why different elephants exhibit different patterns of movement. What underlying factors affect behavior, and why? Does it have to do with age? Sex? Their social environment?
These questions remain unanswered for now, but the work of Meier and colleagues represents a critical step in understanding elephant behavior to improve forest elephant management and conservation strategies.