DNA metabarcoding reveals the dietary habits of elephants

The dietary habits of elephants have been a subject of study for biologists and conservationists. While it is commonly known that elephants eat plants, determining the specific types of plants they consume has been a complex task. However, a recent study conducted by a global team, including conservation biologists from Brown University, employed innovative methods to precisely analyze the dietary habits of two groups of elephants in Kenya.

The researchers aimed to understand the foraging behaviors of individual elephants within the groups and provide insights into conservation strategies that would not only keep elephants nourished but also satisfied. The study, published in the journal Royal Society Open Science, shed light on the importance of meeting the nutritional needs of animals to ensure their overall well-being.

Tyler Kartzinel, an assistant professor at Brown and one of the study authors, emphasized the significance of understanding what each individual elephant consumes in order to effectively manage iconic species like elephants, rhinos, and bison. By comprehending their dietary preferences, conservationists can implement sustainable approaches to support the growth of these populations.

The scientists employed DNA metabarcoding, an advanced genetic technique, as a key tool in their study. This technique enabled them to identify the specific plant species consumed by individual elephants within the groups. DNA fragments extracted from the elephants’ food were matched with a library of plant DNA barcodes, allowing for precise identification.

Brown University has been actively developing applications for DNA metabarcoding and bringing together researchers from molecular biology and computational fields to address challenges faced by conservationists in the field. This study marks the first use of DNA metabarcoding to investigate long-term questions related to social foraging ecology, particularly how social groups, such as elephant families, decide on their dietary choices.

Kartzinel highlighted the difficulty in obtaining a clear understanding of the diets of large mammals like elephants due to various factors. Observing these animals up-close can be challenging and dangerous, as they move over vast distances, feed at night, and frequent dense vegetation. Additionally, many of the plants they consume are small and challenging to identify even for experienced botanists.

Through the innovative application of DNA metabarcoding, this study provides valuable insights into the feeding habits of elephants. By gaining a comprehensive understanding of what these charismatic animals eat in their natural habitat, researchers and conservationists can develop effective strategies for their long-term conservation and well-being.

Understanding an elephant’s favorite foods

The research team conducted a comparison between the new genetic technique, DNA metabarcoding, and a method called stable isotope analysis, which involves chemically analyzing animal hair. Previous research by George Wittemyer at Colorado State University and Thure Cerling at the University of Utah had shown that elephants switch their diet from fresh grasses to trees during the long dry season. While stable isotope analysis provided broad-scale dietary patterns, it couldn’t discern specific plant types in the elephants’ diet.

The team had access to saved fecal samples collected almost 20 years ago during the stable isotope analysis, thanks to a collaboration with the non-profit organization Save the Elephants. Brian Gill, a former post-doctoral associate at Brown, determined that the samples were still usable despite their time in storage.

The scientists combined the analysis of carbon stable isotopes from both feces and hair samples with DNA metabarcoding, GPS tracking, and remote-sensing data to evaluate the dietary variation among individual elephants in two groups. They matched each unique DNA sequence to a reference collection of plants, developed with the expertise of Paul Musili from the National Museums of Kenya. By comparing the diets of individual elephants over time, they discovered that dietary differences among individuals were often more significant than previously assumed, even within family members foraging together.

This study addresses a longstanding question in wildlife ecology: how social bonds maintain cohesion within family groups when resources are limited. Despite elephants seemingly eating the same plants, competition for food doesn’t push them apart and force independent foraging. The researchers found that elephants vary their diets based on resource availability, individual preferences, and physiological needs. For instance, a pregnant elephant may have different cravings and nutritional requirements at different stages of pregnancy.

While the study didn’t focus on explaining social behavior, these findings contribute to theories on why elephants forage together in groups. Since individual elephants don’t always consume the exact same plants simultaneously, there is usually enough food to meet their needs.

These insights have implications for conservation biologists. To protect elephants and other large species and ensure successful reproduction and population growth, it is crucial to provide them with a diverse range of plants to eat. This can help reduce inter-species competition and prevent elephants from encroaching on human food sources, such as crops.

According to Kartzinel, wildlife populations require access to diverse dietary resources to thrive. Each elephant needs dietary variety to flourish, not just in terms of taste but also to maintain healthy feeding habits.

Source: Brown University

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