Rats Return to Dragonera — Who Will Stop the New Invasion?

Rats on Dragonera: A familiar threat resurfaces

Key question: How serious is the situation really — and what needs to change on the ground?

Early in the morning you stand in Sant Elm, look across the steel-blue bay at the silhouette of Dragonera, smell espresso from the kiosk and hear the gulls. Exactly where silence and a sense of protection prevailed years ago, rats have now been sighted again. Specialists from Vectobal and the Balearic Institute of Nature (Ibanat), as well as the director of the natural park, report that rodents have reestablished a foothold on the offshore island.

Before 2011, a major effort eliminated a rat problem on Dragonera: two aerial dispersals using a helicopter and a rodenticide wiped out the populations, with known side effects on some gulls. After that the island was considered rat-free — until now.

The report sounds alarming, but it raises as many questions as it answers. Critically, there is still no clear information about the origin and route of reintroduction: did the animals swim from Mallorca, arrive on boats — or is this a resurgent local population? For broader context on changing encounters with reptiles and other species in the region see Why Snakes Are Appearing More Often in Mallorca Now — Danger, Causes and What We Should Do.

The draft preliminary measures call for monitoring stations with non-toxic baits, snake traps and traps against invasive insects; that is good, but not sufficient, as recent island invasive-species reports underline the complexity, for example Alarm at the Malgrats: Invasive Snakes Threaten the Sargantana.

What has so far hardly appeared in the public debate is responsibility along the entire access chain. Fishermen, excursion boats, private yacht owners and suppliers are part of the problem — and often the point where reintroduction begins. Controls at ports like Sant Elm or the small marina in Andratx have so far been sporadic. Harbour works elsewhere have also highlighted pressure on local controls, see Construction begins in Cala Ratjada: Opportunity for the harbour or a disruption?.

In everyday life I often see pleasure boats leaving in the morning with trash cans and provisions on board — no wonder rats cling to ships, a problem echoed in Trash Chaos in s'Arenal: Residents Mobilize — Demonstration in Front of the Town Hall. Just last week a fisherman at the Sant Elm pier repaired his net while tourists took photos; such situations create opportunities.

Concrete solutions must be practical and long-term: more non-toxic, permanent monitoring points around the island, coupled with a mandatory reporting and inspection procedure for boats wanting to land. Boat owners should be required to prove their vessel is rat-free (especially after prolonged stays ashore). Mobile inspection teams, possibly with scent-detection dogs, could check harbors at night and in the early morning. All measures need a clearly allocated budget — neither volunteer work nor short-term project funding is enough.

Technically useful are genetic analyses of the animals found: these can show whether the population comes from Mallorca or another source. Seed and plant transports must be inspected; the updated catalog of invasive flora with its 33 species is a step forward, but it needs binding countermeasures at corridors such as boat landings and supply routes.

The 2011 decision for a poisoning action was politically and ecologically controversial because gulls were affected. We should learn from that: today the toolbox is broader. Traps, preventive measures at landings, education of the boating community and targeted, scientifically supervised interventions are more compatible if planned over the long term.

What must happen immediately: build a stable network of monitoring stations, regular patrol and inspection rounds, a reporting platform for sightings and a crisis budget that can be activated quickly. In the long term, binding rules are needed for commercial boat operators and cooperation with fishing associations and marinas — only then will biosecurity not remain a paper exercise.

Conclusion: The return of rats to Dragonera is not a natural event to be passively accepted. It is the result of missing controls along human routes. Whoever sits at the harbor in the morning, tasting the sea air and watching the sun over the island, senses this: without clear, regulated responsibilities and practical precautions the problem will repeat. It is time to move from emergency actions to lasting prevention — with boat checks, monitoring, genetic research and clear financing rules. Then Dragonera has a real chance to remain rat-free permanently.