2025年6月英语四级（第1套 · 含听力）仔细阅读 Passage 1

New research suggests that pandas may be at risk of dying out because they are too comfortable. Experts say too much happiness can stop the bears from searching for new mates.
Environmentalists have long believed that building roads or homes near the bears may threaten their survival by reducing or fragmenting their natural habitat, The Times reported. But the new research suggests that a "modest degree of discomfort and fragmentation" may actually help preserve panda populations.
The research was conducted by scientists from Michigan State University. It concluded that pandas fail to wander off in search of new mates if they find their habitat too comfortable, resulting in a lack of vital genetic diversity.
For their study—outlined in a paper in the journal Conservation Biology—the team looked at genetic diversity and spread among a Chinese panda population. The ideal level of perfectly livable habitat was found to be only 80% of an area, with the remainder either too harsh or too affected by human activity.
The experts concluded that pandas should ideally "be happy enough to thrive, but not so content that they don't want to move around and find new mates".
Their conclusions about what The Guardian described as this "sweet spot" are in line with the so-called Goldilocks principle: that there can be just the right amount of something. The concept has been applied to a wide range of disciplines, from developmental psychology to economics and engineering.
Claudio Sillero, a professor of conservation biology at Oxford University, told the newspaper that the new findings could have implications beyond panda conservation.
"Most large animals that eat meat live in increasingly fragmented landscapes," said Sillero, who was not involved in the research. "It may well be that the messy nature of their relationship with human efforts induce more animals to scatter or travel further, and might result in greater genetic connectivity and enhanced population persistence."
The most recent count of pandas found that there were more than 1,800 left in the wild, putting them on the list of vulnerable, but not endangered, species.