The Pyrenean desman seeks shelter in rock crevices, caves, or the burrows of water rats, only rarely digging their own burrows. This species lives in pairs that are typically monogamous, with the male’s territory completely encompassing that of the female, although solitary adults also exist (6). Territories are scent-marked and will be defended to the death against intruders (5) (6). The breeding season is from January to May, during which females may breed up to three times (5) (6). Litters of one to five, usually three to four, young are born after a gestation period of about 30 days, and weaning probably takes place after around 30 days (5) (6). Sexual maturity is thought to be attained after approximately two years, but little else is known of the life history patterns of this enigmatic species (5).
The Pyrenean desman feeds nocturnally on a diverse array of crustaceans and insect larvae, including stoneflies and caddis fly larvae (1), although this amphibious mammal may also exhibit short periods of activity during the day (3). Ungainly on land (5), this species is a powerful swimmer and accomplished diver, primarily foraging by sifting through stream sediments with its forefeet and using its extremely tactile and sensitive long snout to search for prey (3). It has been suggested that the Pyrenean desman may also slap the surface of the water to produce noises useful in echolocation to help find its way around and locate underwater prey, but this is only speculation (5) (6).