Reviving Rivers: The Remarkable Return of Eurasian Beavers to the Iberian Peninsula

Reviving Rivers: The Remarkable Return of European Beavers to the Iberian Peninsula

European beavers – Castor fiber – El castor europeo, have a fascinating history in the Iberian Peninsula, where the species was documented until the late 16th century before becoming extinct due to over hunting and persecution for its meat and fur.

In 2003, unauthorized beaver reintroductions occurred in the Ebro river basin in Spain. These beavers, protected since 2011, have since expanded into new areas, including the Douro and Tagus basins. Recently, there have been sightings of beavers in the Tormes river, near the Portuguese border, suggesting a potential return to Portugal after extinction in the Middle Ages.

Illegal re introductions in Spain of European beaver

In 2004, 18 European beavers from Bavarian farms were discovered near the Navarre-La Rioja border after they had been illegally released in March 2003.

in 2004 a biologist working on the banks of the river Aragón noticed tree trunks with teeth marks. It later transpired that the beavers had been smuggled in from central Europe in March 2003 and secretly released. The details are vague but the authorities suspected the activist Olivier Rubbers, who later admitted his involvement. (See further reading below)

Despite initial plans to remove them, the European Union recognized beavers as native to Spain. By 2020, beavers had successfully established themselves in regions such as La Rioja, Navarre, Zaragoza, Vitoria-Gasteiz, Pamplona, Mezalocha, and the province of Soria. In November 2021, a young beaver was even spotted outside the Ebro basin, in the upper Duero in Soria.

Beavers in Andalucia

Recent reports (spring and summer 2023) announced the presence of beavers in the Guadalquivir River basin close to the towns of Villatorres and Torreblascopedro in the province of Jaen.

Reviving Rivers: The Remarkable Return of Eurasian Beavers to the Iberian Peninsula
SECEM (Spanish society for the conservation and study of mammals) anouncement and paper regarding beavers in the Guadalquivir:

Tracks and tree gnawing were discovered on the riverbank. Some of these, due to their weathered appearance, suggest that the species has been present in the area for several months.

Reviving Rivers: The Remarkable Return of Eurasian Beavers to the Iberian Peninsula
The size of the tracks (18 cm foot length) and the gnaw marks on the trees rule out the possibility of them belonging to any other species of aquatic rodent. Coypu (Myocastor coypus) tracks are much smaller, with an average foot length of 11.4 cm, and their gnawing is always superficial.

The considerable distance between this area and the known distribution range in the Peninsula (365 km) suggests that their arrival in the Guadalquivir is the result of another irregular introduction. It is not possible to determine if the traces belong to the European beaver – which is more likely – or the American beaver, (Castor canadensis).

The study group go on to explain that “It would be highly interesting to identify the species specifically, especially given that the former is a protected species in Spain and the latter is an exotic species. It is also necessary to implement a monitoring protocol as soon as possible to assess the magnitude and population trends.”

Beavers, ecosystems and habits

Eurasian beavers play a vital role in their ecosystems. They create wetlands that serve as homes for various animals, including the European water vole, Eurasian otter, and Eurasian water shrew. By trimming waterside plants, beavers encourage their regrowth and provide shelter for birds and other creatures. Beaver dams help trap sediment, enhance water quality, recharge groundwater tables, and offer cover and food for trout and salmon. Additionally, they contribute to increased abundance and diversity of vespertilionid bats by creating gaps in forests that facilitate bat navigation.

Reviving Rivers: The Remarkable Return of Eurasian Beavers to the Iberian Peninsula
Beavers are keystone species providing food and habitat for a wealth of other species. Photo credit – Ark Nature:

In terms of reproduction, Eurasian beavers have one litter per year, typically occurring between late December and May, with a peak in January. Unlike most rodents, beaver pairs remain monogamous and stay together for multiple breeding seasons. The gestation period lasts approximately 107 days, resulting in an average of three kits per litter, though the number can range from two to six. Most beavers do not begin reproducing until they reach three years of age, although about 20% of two-year-old females can also reproduce.

As for their diet, European beavers are herbivores, consuming various water and riverbank plants, including tubers, myrtle rootstocks, cattails, water lilies, and even tree bark. Their unique digestive system allows them to break down cellulose in bark. They consume daily approximately 20% of their body weight in food.

A wildlife protection success story

The successful reintroduction of European beavers is a significant achievement, benefiting both the species and the broader ecosystem. Beavers are often referred to as “ecosystem engineers” due to their profound impact on the environment. Their ability to create wetlands and dams greatly contributes to biodiversity and water quality. The return of beavers to these regions has led to increased habitat availability for various wildlife species, improved river health, and a reduction in sediment and pollutants, benefiting both nature and humans.

This success story wouldn’t have been possible without the collaboration and support of local communities, conservation organizations, and governmental agencies. Efforts to protect and conserve beaver populations have fostered a greater appreciation for these industrious creatures and their role in maintaining healthy ecosystems. In some areas, community-led initiatives have embraced beaver-based ecotourism, providing economic benefits to local businesses while promoting environmental education and awareness.

While the return of beavers to these regions is undoubtedly a positive development, it also presents challenges that need to be managed responsibly. Some concerns include potential conflicts with human activities, such as flooding of agricultural land and damage to infrastructure caused by beaver dam-building. Conservationists and local authorities are working together to find sustainable solutions to mitigate these issues, often through the implementation of beaver management plans that balance the needs of both beavers and humans.

Ongoing scientific research and monitoring are critical components of this success story. Scientists are closely studying the behavior, ecology, and population dynamics of these reintroduced beavers to gain valuable insights into their adaptation to the Iberian Peninsula’s environment. The data collected helps inform conservation strategies and ensures the long-term viability of the species in these regions.

The successful beaver reintroduction in the Iberian Peninsula also has global significance. It serves as an inspiring example of how collaborative conservation efforts can lead to the recovery of keystone species and the restoration of ecosystems. This achievement encourages other regions to consider similar initiatives for the benefit of biodiversity and the environment.

Further reading about European beavers

This article is designed to help anyone researching the subject of beavers being re introduced in the Iberian peninsular

Some alternative titles for Eurpean beavers in Spain
  • Nature’s Architects: Beavers Reclaim the Iberian Peninsula
  • Eurasian Beavers: Conservation Success in Spain
  • Beaver Comeback: Restoring Balance in Iberian Ecosystems
  • The Resilient Return of Beavers to Iberian Waterways
  • Ecoheroes of the Iberian Peninsula: The Beavers’ Return
  • Beaver Reintroduction Triumphs in the Iberian Peninsula
  • From Extinction to Rebirth: Beavers in Iberia
  • Iberian Rivers Reawaken: The Beaver’s Second Chance
  • Beavers’ Resurgence: A Tale of Restoration in Spain
  • Nature’s Engineers: Beavers’ Return to Iberian Watersheds
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