One of the founder animals of the beaver population at the river Hase.

Emsland Beavers

Zur deutschen Version Beaver biology

Development of the kits


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After a gestation period of 100 to 110 days (105 days in average) between the beginning of April and the middle of July 1 to 5 (max. 6 pubs) completely furred pubs with open eyes and ears are born (Grzimek & Piechocki 1968; Freye 1978; Piechocki 1989; Nowak 1999; Grimmberger & Rudloff 2009). After Heidecke (1984) the mean number of pubs born per female amounts to 2.93 in the Elbe beaver (C. fiber albicus). In the Eurasian form, the birth weight of young beaver varies between 300 and 700 g with a head-body length between 30 to 35 cm (Wilsson 1971; Djoshkin & Safonov 1972; Freye 1978; Piechocki 1989; Nowak 1999; Grimmberger & Rudloff 2009).

Beavers are categorised as precocial, whereas in the low ossification rate of the skeleton they rather resemble altricical young (Freye 1978). Young beavers are already able to swim by the age of 4 days (Baker & Hill 2003), however, they can not leave the burrow on their own because this can only be achieved by diving, which pubs at this age are not able to do (Freye 1978). Moreover the fur of the beaver pubs in their first 3 to 4 weeks of life is not water repellent like in adult animals (Baker & Hill 2003). Therefore, the pubs are leaving the burrow only after an age of 4 to 6 weeks (Freye 1978). According to other data, young beavers can only be seen outside of the burrow for the first time at an age of 2 month (Wilsson 1971). At least for North-American beavers it is assumed, that they are only able to dive and stay under water for a longer time at this certain age (Baker & Hill 2003).

Development of the body mass of beaver kits after Wilsson (1971), Djoshkin & Safonow (1972) and Freye (1978).
Development of the body mass of
beaver kits after Wilsson (1971),
Djoshkin & Safonow (1972) and
Freye (1978).
The pubs are being nursed for about 2 month (C. canadensis up to 3 month; Nowak 1999), whereas they already start to feed on plants, which are carried into the burrow by the parents, at an age of about 8 to 14 days (Freye 1978; Piechocki 1989). At a dry substance content of approximately 30%, the breast milk contains 16 to 21% fat and 11 to 12% protein (the values are similar for Eurasian and North-American beavers; Freye 1978). With a weight gain of 40 to 50 g per day, the pubs are growing considerably fast within the first 2 month of age (Djoshkin & Safonow 1972), weighing already between 1.7 and 1.8 kg (max. 3.0 kg) after 1 month, 2.9 to 3.1 kg (max. 5.0 kg) after 2 month, and 3.9 to 4.2 kg (max. 6 kg) after 3 month of age. At an age of 6 month the young beavers reach a body weight of 6 to 7 kg, after 1 year they are weighing approx. 9 to 10 kg and at an age of 2 years the body mass reaches about 16 kg (data of caged animals after Wilsson 1971 and Freye 1978).
Sexual maturity is reached at a body weight of about 17 - 18 kg at an age of 2.5 to 3 years, whereas this is also the time the subadults are no longer tolerated within the parental territory (Djoshkin & Safonow 1972; Freye 1978). At an age of about 4 years the animals are full-grown (Freye 1978), although even in adult beavers the body mass can be subject to pronounced fluctuations depending on environmental conditions and food provision (see above).

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