The Common hamster, Cricetus cricetus, belongs to the rodent order (Rodentia) and the Cricetidae family, which includes voles, rats, and other small mammals. Within this family, it belongs to the Cricetinae subfamily, the true hamsters (Arctos, 2018). The species stands out because of its size. Adults reach 27–30 cm in length, including the short tail, and weigh between 160 and 600 grams (Ecopedia, 2024; Van Donink and Baert, 2023). This makes it the largest hamster species in the world (Weinhold, 2009; La Haye, 2020). Its typical features include rounded ears, a russet-brown coat, and a black belly with white spots (Schröder, 2014).

Outside the breeding season, males and females live solitary in their own underground burrows. dug to a depth of approximately 1 metre (maximum 2 metres) (Glas, 1961). Only loess and loam soils are suitable for digging burrows, as these soils are sufficiently firm and at the same time permeable to water, preventing moisture problems in the burrow (Piechocki, 1970; Niethammer 1982).

Hibernation takes place from November to March. In autumn, the hamster ensures that its burrow is well stocked with at least 1 to 2 kg of plant-based food, consisting mainly of grains (Wendt, 1991; Nechay, 2000). In the second half of May, the breeding season begins and females will temporarily tolerate the presence of males in their burrow. The polygamous male seeks out as much females as possible throughout the season. The population dynamics of the hamster follow the r-strategy, whereby many offspring are produced with a short lifespan. The gestation period is 17-18 days and the average litter size observed in captivity is 5-6 pups, but can be as high as 10-12 pups (Kuiters et al., 2010; La Haye, 2020).

From Abundant to Critically Endangered.

The Common hamster, also often called European hamster is a species that developped during the pleistocene to inhabit steppe landscapes of Europe and Asia (Niethammer, 1982). Several genetic lineages exist in Europe.

The populations in Belgium, the Netherlands, and North Rhine-Westphalia (Germany) form a separate western lineage called the “BNN-lineage.”

At the start of the 20th century, the European hamster still lived across Western Europe (Van Donink and Baert, 2023). Numbers of ten to eighty individuals per hectare were common, and peaks reached two thousand per hectare (Ruzic 1977, Surov et al., 2016). The hamster was then considered a pest species.

In recent decades its range shrank and long term monitoring shows a sharp drop in population sizes (Ambros et al. 2003, Bihari 2003, Ziomek & Banaszek 2007, Tkadlec et al. 2012, Korbut et al. 2013, Rusin et al. 2013, Hegyeli et al. 2015). Current estimates show a yearly decline that may be 50% (Banaszek et al. 2020). If this trend continues, the species may disappear from Europe around 2038 (Surov et al., 2016). In Belgium, the Netherlands and Nord Rhein Westfalen the decline is even worse and survival of the species solely depended on breeding and reïntroduction efforts.

This unfavourable and declining conservation status of the Common hamster resulted in the Bern Convention (Annex II) and the EU Habitats Directive (Annex IV) requiring Member States to support and restore its populations so they reach a good conservation status. Even despite this strict protection by the early 2000s, the populations in the BNN genetic lineage were on the brink of extinction and some completely disappeared.

In the Netherlands the hamster protection plan ran from 2000 – 2004 en started with the introduction of bred individuals from the BNN genetic lineage. Conservation efforts in Belgium en Germany took a slower start, which led to the European Commission sending reasoned opinions to Germany (2001) and Belgium (2005) for not protecting hamster breeding sites. This resulted in more National Species Protection Plans (SPPs), following the footsteps of the Netherlands. Using measures consisting of the breeding, introduction/ restocking of the species and enhancing the habitat by implementing Agri- Environment-Climate Measures (AECM).

Despite these SPPs the conservation status of the species did not improve. Legal action alone cannot stop the decline. Cross-border projects such as LIFE Cricetus must solve key problems and help Member States meet the Directive in a realistic way.