Scientists and farmers are alarmed: Snake invasion on Mallorca | Focus on Europe

Key Concepts

• Invasive Species: Organisms that are not native to a particular ecosystem and can cause harm to the environment, economy, or human health.
• Horseshoe Whipsnake (Hemorrhois hippocrepis): The specific invasive snake species discussed in the transcript.
• Native Fauna: The animal species that naturally belong to a particular region.
• Ecological Balance: The equilibrium between the biotic (living) and abiotic (non-living) components of an ecosystem.
• Predator-Prey Relationship: The interaction where one organism (predator) hunts and kills another organism (prey) for food.
• Adaptation: The process by which organisms evolve traits that help them survive and reproduce in their environment.
• Biocontrol: The use of natural enemies to control populations of pests or invasive species.

Invasive Species Threat on Mallorca

The horseshoe whipsnake (Hemorrhois hippocrepis) has become a significant invasive species on the Balearic Island of Mallorca. This species, which is not native to the region, is spreading rapidly and poses a serious threat to the island's native fauna. Scientists and wildlife officers are actively working to manage and control its population.

Introduction and Spread of the Horseshoe Whipsnake

• Origin: The horseshoe whipsnake was likely introduced to the Balearic Islands accidentally, possibly arriving on ships from the mainland.
• Mode of Introduction: A probable pathway for their arrival is within the root balls of olive trees.
• Rapid Spread: The species is described as spreading rapidly, with observations of shed skins indicating their established presence.

Ecological Impact and Threats to Native Species

• Predation on Native Animals: Horseshoe whipsnakes are a threat because they prey on native animals.
• Impact on Agriculture: Farmers, like Andreu Andro, are concerned about the ecological consequences. The snakes hunt birds, which are natural predators of agricultural pests. A decrease in bird populations due to snake predation leads to an increase in pests, impacting organic farming practices.
• Vulnerability of Native Lizards: A specific concern is the threat to a unique lizard species endemic to Mallorca. These native lizards have not evolved defenses against new predators like the horseshoe whipsnake, making them easy prey. Miguel P, a biologist, highlights that native species "had always been safe from these predators. So they haven't adapted for survival. They have no defense mechanisms against new unfamiliar predators like these snakes. So they are easy prey."
• Lack of Natural Predators: Horseshoe whipsnakes have no natural predators on the Balearic Islands, and even birds of prey show little interest in them.

Management and Control Strategies

• Capture and Culling: The primary method of control involves trapping and killing the invasive snakes.
• Trapping Methodology:
  • Bait: Live mice are used as bait.
  • Mechanism: Snakes are lured into traps by the scent of the mouse. When the snake attempts to reach the mouse, a door falls shut, trapping the snake.
  • Mouse Safety: The mouse is kept safe on the other side of a screen, preventing it from being eaten by the snake.
• Trap Checks: Wildlife officers check the traps every two weeks.
• Distinguishing Native vs. Invasive: Native snakes found in traps are released, while horseshoe whipsnakes are killed.
• Scale of Operations: Wildlife officers trap approximately 3,000 snakes per year.
• Additional Invasive Species: The horseshoe whipsnake is not the only invasive snake species; three other snake species have also been introduced from the mainland.

Perspectives and Challenges

• Emotional Response: While acknowledging the necessity of killing the snakes for conservation, there is an expressed sentiment of pity: "I really feel sorry that we have to treat them like this. It's not their fault that they're here, but this is the only way to protect the native species on Mayora."
• Farmer's Experience: Andreu Andro, an organic farmer, describes the snakes as aggressive when cornered: "When they're trapped and you get close, they go wild and bite very quickly. That's a bit scary."
• Long-Term Outlook: Miguel P suggests that complete eradication may not be feasible. The focus might shift to slowing their spread and finding a balance: "I think we can only try to slow their spread to strike a balance between the native species here and the newcomers. But in the long term, we will probably have to get used to their presence."
• Uncertainty of Population Size: The exact number of horseshoe whipsnakes on the Balearic Islands is unknown, but it is understood that they are established and likely to remain.

Conclusion

The horseshoe whipsnake invasion on Mallorca presents a significant ecological challenge. The species' rapid spread, lack of natural predators, and predatory behavior threaten native fauna, particularly vulnerable lizard species, and disrupt agricultural ecosystems. Current management strategies focus on trapping and culling, with an estimated 3,000 snakes removed annually. While efforts are made to protect native species, the long-term presence of invasive snakes is anticipated, necessitating a shift towards managing their spread and coexisting with them.