AP Biology class blog for discussing current research in Biology

Tag: Carnivores

Trash, Crops, and Even Pets are on the Menu for these Carnivores

In a recent study, researchers at the University of Wisconsin-Madison and the University of New Mexico found that some of North America’s most prominent carnivores—wolves, mountain lions, bobcats, and foxes—are relying more and more on human sources of food such as trash, crops, and even small pets. In the study, the researchers used hair, fur, and bone samples to identify the diets of seven hundred carnivore species across the upper midwest region of the United States. To identify the diets, chemical isotopes of carbon were taken from these samples to distinguish between human-grown and naturally occurring foods.

Phillip Manlick, the lead author of the study, explains that “Isotopes are relatively intuitive: You are what you eat.” Thus, Human foods, heavy in corn and sugar, have their own distinctive carbon signatures in comparison to the carbon signatures of the diets of prey species in the wild. The ratio of these two isotope fingerprints from the predator samples informs the researchers what proportion of the predator’s diet came from human sources, either directly or from their prey that ate human food first. Our AP Biology class learned that carbon is an essential element in organic compounds. Organic compounds make up all living things which include the human food waste and crops these predators are consuming. Carbon is found in all four organic compounds (Carbohydrates, Proteins, Fats, Nucleic Acids), for carbon’s molecular structure allows for it to create multiple stable covalent bonds with different molecules. Carbon’s covalent bonds enable complex molecules, such as carbohydrates and proteins, that are found in food sources to be formed. 

According to the results of the study, foxes, coyotes, fishers, and martens were the most likely to eat from human food sources, getting about half their food by eating domesticated animals or by foraging in areas that have been disturbed by agriculture. But on average, more than “25 percent of all the carnivores’ diets came from human sources in the most human-altered habitats.”

The reliance on human food sources is not good for the ecosystem, for it increases the overlap in competition for food among these carnivores. There will be more conflicts between species for human food. Furthermore, the reliance on human food sources leaves carnivores susceptible to more human attacks or can change the way species of predators hunt. None of these effects are beneficial to the ecosystem and actually may potentially have harmful ecological consequences.

Personally, I find it a little upsetting that human action is having such interference on the ecosystem and food chain of these predators. In addition, it is even more upsetting to hear that there are very limited options to take that would reduce the reliance on human food sources for these carnivores. Other than securing garbage cans and keeping pets inside at night, there are not many more options. These carnivores are adapting to human urbanization, and this trend will continue as humans keep pushing into these carnivores territories and habitats.

Sweet Genes Not So Sweet

Do you enjoy eating foods that taste sweet? Do you also like to eat meat? Well, what would you do if you ate so much meat that your genes responsible for detecting the sweet taste suddenly stopped? Would you be upset? I certainly would be. Thankfully, humans do not have to worry about this problem yet, but a recent study shows that animals that are specialized carnivores have lost the power to taste sweetness.

Credit: Martin Heigan

The study analyzed twelve different mammals and their sweet detector gene Tas1r2. The researchers found that in seven out of the twelve animals, Tas1r2 experienced mutations. The gene carried disabling glitches in hyenas, otters, fossa, banded linsang, sea lions and two different kinds of seals. What these animals have in common is that they are all predators. The study’s coauthor Gary Beauchamp believes that this means that the mutations in Tas1r2 “could easily spread through populations.”

While these carnivores have lost their ability to taste sweetness, this loss is not universal among meat eaters. For example, animals like red wolves are fervent meat eaters, but have not lost their genetic sweet spot. Beauchamp believes that the carnivores that have not lost the function of this gene will soon lose it in the future due to evolution.

However, there are many arguments in opposition to Beauchamp’s proposal. Animals that do not specialize in meat may have also lost their ability to taste sweetness. Chickens eat both plant and animal foods, but do not seem to notice sweetness in their food and appear to lack a functional Tas1r2. Huabin Zhao of Wuhuan University in China believes that chickens are just one reason that Beauchamp’s conclusion is not convincing. Zhao suggests that “narrow diet specialization might be a better explanation” for the meat-eater sweet-loss scenario.

The only way to determine if Beauchamp’s conclusion is valid is

to see if there will be disabling genetic glitches in Tas1r2 in other types of carnivores in the future. If this does occur, then this genetic mutation has the potential to shape the evolution of carnivores. Similar to these carnivores, people have also had their “use-it-or-lose-it” sensory evolution. For example, humans are not great at detecting odors and even worse when it comes to noticing pheromones, the strong animal-to-animal chemical communications. Only time will tell if the mutations of Tas1r2 will spread to all carnivores, but let’s hope humans do not lose the functionality of their sweet detector gene because sweet food tastes too good!

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