{
  "id": 98104,
  "title": "Invasive rats are stopping small mammals from returning to Madagascar's regenerating forests: Study",
  "url": "https://urgent.news/2026/08/03/invasive-rats-are-stopping-small-mammals-from-returning-to",
  "topic": "science",
  "section": "Science",
  "published": "2026-08-03T18:00:03.000Z",
  "source": {
    "name": "Phys.org",
    "slug": "phys-org",
    "url": "https://phys.org/news/2026-08-invasive-rats-small-mammals-madagascar.html"
  },
  "original_language": "en",
  "account": "In southeastern Madagascar, recovering forests may be hindered by invasive black rats, according to a recent study led by an interdisciplinary team of biologists from Canadian, American, and British universities collaborating with students from the University of Antananarivo. These forests, once cleared for farming and now slowly regenerating, rely not only on regaining tree cover but also on the return of native animal populations for proper ecosystem functioning. However, invasive species often outcompete native animals, making it challenging for recovering forests to regain their natural balance.\n\nThe researchers studied Ranomafana National Park, home to 12 species of Madagascar's famous lemurs, focusing on native small mammals such as brown mouse lemurs, tanala tufted-tail rats, and greater long-tailed shrew tenrecs. Contrary to expectations, these native species were scarce in regenerating forests, replaced instead by black rats, which are invasive alien mammals that have caused ecological havoc in various island and tropical ecosystems. These black rats, native to Southeast Asia, have traveled the world through trade, posing a threat to island and tropical environments.\n\nThe study found that forests with high black rat populations had fewer native species, while sites with fewer black rats had more native species, regardless of the forest's regeneration age. In mature forests within Ranomafana National Park, native species outnumbered invasive ones, with approximately 90% of small mammals being native. However, in regenerating forests, nearly 80% of small mammals were invasive black rats, indicating that invasive rats can dominate regenerating forests and prevent native species from returning.\n\nThe findings suggest that forest regeneration alone is insufficient to restore small mammal communities if invasive rat populations are left unchecked. While the research could not determine which specific species were present before deforestation, the study employed 25 plots, comparing five control sites within the protected area of Ranomafana National Park with 20 sites outside the protected region. To study the impact of invasive rats on native species, the researchers set up folding traps at each site for six nights every three months over a year, capturing, identifying, and releasing the animals without causing harm.\n\nMouse lemurs, key to rainforest regeneration, were found often enough to analyze their numbers in relation to invasive rat populations. While invasive rats did not directly affect mouse lemur abundance, they negatively impacted their weight, potentially due to competition for food resources. The study suggests that maintaining black rat numbers below 3.3 per 100 trap nights could allow brown mouse lemurs to coexist with invasive rats. However, fully eradicating black rats without endangering native species remains a challenge, as poisoned pellets have previously caused unintended harm to native birds. Trapping invasive rats in human settlements is a practical approach to curbing their spread into forests and mitigating their detrimental effects on both native species and human populations. The study emphasizes the importance of preserving old-growth forests for the long-term survival of native species.",
  "summary": "In southeastern Madagascar, patches of forest that were once cut down to make way for farms are slowly regenerating naturally after being left to lie fallow. But recovering a native forest needs more than just gaining tree cover. The animals that once lived in these forests also need to make their way back so that the forest can function the way it used to.",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}