Image Credit: © Robert Zingg, Zoo Zurich
Image Credit: © Robert Zingg, Zoo Zurich

DNA of Tiny Lemurs Shows Big Changes in Madagascar’s Landscape

Image Credit: © Robert Zingg, Zoo Zurich
Image Credit: © Robert Zingg, Zoo Zurich

Scientists comparing the genes of five teeny lemur species found that, once upon a time, the animals’ disparate habitats were all connected. They published their findings in the Proceedings of the National Academy of Sciences.

All 24 species of mouse lemurs (genus Microcebus) are primates descended from a common ancestor in the forests of Madagascar more than 10 million years ago. In the intervening time, the species have scattered across the island. They still look a lot alike from the outside, but each species has adapted to its own environment—changes that left a mark in the lemurs’ genes.

Adorable, hardy, fast-breeding, and unique to their environment, mouse lemurs are a geneticist’s dream subject. Female mouse lemurs reach sexual maturity when they’re just 12 months old. This means that their generations are short; or, to put it another way, they evolve much more rapidly than many other mammals.

Paper co-author Steve Goodman of The Field Museum in Chicago has spent the last 30 years studying Madagascar’s wildlife. He and his colleagues are working to piece together the natural history of the island itself by studying the animals that live there. For this study, they compared the genetic codes of five different mouse lemur species. (One of those species, Microcebus lehilahytsara has special significance for Goodman: “lehilahytsara” is Malagasy for “good man.” In English, the species is called Goodman’s mouse lemur, for the biologist’s many scientific contributions on the island.)

Goodman's mouse lemur. Image Credit: © Robert Zingg, Zoo Zurich

Analysis of the lemurs’ DNA showed that the species were still genetically close to one another. “That suggests that their ancestors were able to disperse across forested habitat that no longer exists,” Goodman said. He and his colleagues believe the now-separate east and west sides of the island were likely linked by a patchwork of forests.

Looking back in time through changes in the lemurs' DNA, the researchers could identify when the species split from one another and, consequently, what might have been happening on the island to make that possible.

A longstanding theory of the island's biogeography holds that it was the arrival of humans thousands of years ago that triggered the ecological shift. Yet the lemurs' DNA showed that the species had clearly diverged long before then, indicating that the landscape was already on the move by the time we arrived. It seems that natural climate change had a hand in the slow geographic shift.

“Madagascar is one of the top conservation priorities in the world,” Goodman said. “All of the native land mammals on Madagascar occur nowhere else in the world. This study is important because it sheds light upon the long-term life history of Madagascar, before human colonization. It helps us understand change.”

Know of something you think we should cover? Email us at

Whale Sharks Can Live for More Than a Century, Study Finds

Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.

There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]


More from mental floss studios