Dogs in Madagascar’s Grasslands Eat Forest-Derived Foods

A new study shows that dogs who spend time in Madagascar’s grasslands typically consume forest-derived foods, including endemic species such as the tenrec.

Humans bring their dogs everywhere. Nowadays we bring them along to run errands and visit with friends and family, but in the past, humans also brought their dogs to help them settle in new environments. This is the case in Madagascar, where dogs were introduced millennia ago by human settlers from mainland Africa, likely at the same time as the introduction of livestock.

But just like any other non-native species, dog behavior and eating habits can impact the ecosystems they are introduced to. To better understand the impact that dog diets have on Madagascar’s remaining forests, researchers have collected and analyzed dog feces from grassland environments neighboring protected forests on the eastern side of the island. The results of the new study show that even dogs who live in grassland environments often eat forest-derived prey. 

To conduct the research, Sean Hixon of the Max Planck Institute for Geoanthropology worked with members of the Mad Dog Initiative, an organization that protects the wildlife of Madagascar through the humane management of domestic and feral dogs, to study 100 modern dog feces samples from the forest margins and derived grasslands surrounding Analamazoatra and Andasibe-Mantadia National Parks. To get an estimate of the breadth of dog diets, the samples were first inspected visually for plant remains, animal remains, and human trash, revealing highly fragmentary animal bones, portions of animal keratin, and at least one bird feather.

Although these initial signs point to at least some reliance on endemic forest species such as the tenrec (a small, hedgehog-looking animal), the team conducted stable carbon and nitrogen isotope analysis to better identify the environments dogs had been exploiting for food.

“The isotopes in feces actually provide a lot of clues about an animal’s diet,” says Hixon. “For example, stable carbon isotope values tend to be distinct in foods that come from open, grassy habitats versus closed, forested habitats. Also, predators and herbivores tend to have distinct nitrogen isotope values.”

Stable isotope analysis showed that most of the dogs in the study area relied mainly on forest-derived foods, with a relatively small reliance on foods from grasslands. These findings could have implications for local biodiversity and conservation efforts.

“Our study showed that dogs on the edges of forests primarily rely on forest-based foods, but we need further research to better determine their reliance on specific prey species,” says Hixon. “If dogs in forests mostly consume threatened endemic animals, and not introduced animals like rats, the exclusion of dogs from protected forests should be a priority.”

In addition to highlighting dogs’ potential impact on native species through predation, the study suggests that dogs move between cleared forest and protected forest, increasing the risk of spreading diseases or parasites.

The current study is a first step towards learning about dog diets in Madagascar and raises the next questions for researchers to investigate. Work is already under way to increase the resolution of prey identification using DNA analysis of feces. The team also has ideas for future observational studies, including radio collars to track dog movement. With a more detailed understanding of the ways that dogs in Madagascar impact forest ecology, wildlife management teams will be better able to assess where and how to control local dog populations.