Portugal’s largest bat colony discovered at Alqueva

Portugal’s largest known colony of vulnerable greater mouse-eared bats (Myotis myotis) has been discovered in the Alqueva region, where more than 10,000 animals have been found in a former water mine, the Alqueva Development and Infrastructure Company (EDIA) has announced.

The discovery was made within the area influenced by the Alqueva Multiple Purpose Project, in a former water mine known as Abrigo Beja I. Recent surveys carried out in June confirmed the exceptional size of the colony, making it one of the country’s most significant sites for bat conservation.

The roost is also home to three other bat species classified as vulnerable in Portugal: the Schreiber’s bat (Miniopterus schreibersii), the Mehely’s horseshoe bat (Rhinolophus mehelyi) and the Greater horseshoe bat (Rhinolophus ferrumequinum).

According to EDIA, the presence of four vulnerable species in a single location underlines the site’s exceptional ecological value and its importance for the conservation of Portugal’s biodiversity.

The colony was first detected in April 2023 during an inspection to verify compliance with environmental conditions linked to the Alqueva project. Inspectors noticed a large concentration of bats through the mine’s ventilation shaft, prompting a programme of monitoring and conservation work that has now confirmed the site’s national significance.

EDIA said the discovery highlights the value of long-term environmental monitoring around the Alqueva development, helping to balance agricultural activity with the protection of wildlife.

Beyond its conservation importance, the colony also provides a significant ecological service. The bats are estimated to consume more than 100 kilograms of insects every night, helping to control agricultural pests and reduce the spread of insect-borne diseases across the surrounding farming landscape.

Abrigo Beja I forms part of a network of 21 bat roosts monitored by EDIA in partnership with the Institute for Nature Conservation and Forests (ICNF). Collectively, these colonies consume more than 600kg of insects each night, contributing to the sustainability of the Alqueva agricultural ecosystem through natural pest control.

The discovery adds to scientific knowledge of the wildlife supported by the Alqueva region and further demonstrates the ecological importance of habitats associated with one of Portugal’s largest infrastructure projects.

EDIA said continued monitoring will help safeguard the colony while ensuring farming and biodiversity conservation can coexist across the Alqueva landscape.

Source: EDIA

Inês Lopes

Newspaper editor at The Portugal Resident