Pyrenean Desman

The Pyrenean desman is an endemic species of mountainous regions of the Pyrenees, the Cantabrian Mountains, and the Iberian Sistema Central. It occurs primarily along specific rivers and their tributaries (listed from north to south and from west to east):

France: Nivelle, Nive, Gave d'Aspe, Gave d'Ossau, Adour, Neste, Pique, Garonne, Hers-Vif, Salat, Arize, Ariège, Aude, Rébenty, Agly, Têt, and Tech; Spain: Bidasoa, Leitzaran, Deba, Artibai, Lea, Gobelas, Oka, Auritz, Irati, Aragon, Gállego, sierra de Guara, Ara, Cinca, Noguera Ribagorçana, Noguera Pallaresa, Segre, Ter, Oviedo, Pisuerga, Xallas, Tambre, Lérez, Oitavén, Sil, Tâmega, Arandilla, Duero; Portugal: Minho, Rio Âncora, Lima, Neiva, Cávado River, Ave, Rio Leça, Douro, Vouga, Mondego, Zêzere. Many of these rivers are separated by continental divides or belong to distinct and non-contiguous drainage basins; as a result, the species' distribution is highly fragmented. At a broad scale, the current range is considered a remnant of post-glacial expansion into newly available habitats, facilitated by terrestrial corridors and possibly a denser river network during the Holocene. At a finer scale, however, movements between neighbouring drainage basins may have occurred more recently.

Sexual activity occurs from December to May in males and from February to June in females, with timing varying by region according to temperature, climate, and altitude. There is no clearly defined breeding season, although three peaks in gestation have been identified in February, March, and May. Females may produce more than one litter per year, but this has not been conclusively demonstrated. The duration of gestation has not been directly observed, and neither gestation nor neonates younger than three months have been documented. By comparison with other members of the Talpidae family, gestation is estimated to last approximately 30–40 d (3,500 ks). Lactation is reported to last around four to five weeks. Parturition has not been observed directly but is presumed to take place in underground burrows. Litter size does not exceed five individuals and more commonly comprises three to four. Females possess eight teats: two pectoral, two abdominal, and four inguinal. Sexual maturity is reported to be reached within a few weeks.

The desman has a high metabolic rate and must consume approximately one-third to one-half of its body mass daily (20–30 g (0.71–1.06 oz)). During mid-winter, when water temperatures are lowest, daily intake may reach its entire body mass (60 g (2.1 oz)). The mountain winter period (January–April) coincides with both the reproductive phase and peak prey availability.

Analyses of stomach contents, faeces, and observations of captive individuals indicate that the diet consists primarily of benthic invertebrate larvae belonging to three insect orders: mayflies, stoneflies, and caddisflies. Early morphological studies characterised the species as a specialised predator. Molecular analyses of faeces conducted in the 2010s refined this assessment, showing that these three orders account for about 80% of prey items but represent only one-third of the identified prey species. Additional prey include dipteran larvae and crustaceans such as freshwater shrimp. A broad range of other taxa is consumed opportunistically, including beetles, lacewings, true bugs, moths, dragonflies, myriapods, arachnids, newts, snails, and occasionally fish.Strictly terrestrial prey, such as spiders, grasshoppers, and earthworms, account for around 10% of prey items and more than one-third of identified species. …

The generic name Galemys is derived from the Ancient Greek γαλῆ (galễ, meaning "weasel") and μῦς (mûs, meaning "mouse"). The term "desman" originates from the Swedish desman ("musk"), a diminutive of desmanrätte ("muskrat"). This word ultimately derives from Middle Low German Desem and Medieval Latin bisamum, both of which refer to musk.