Nest-building behaviour in male rats from three inbred strains: BN/HsdCpb, BDIX/Or1Ico and LEW/Mol
Three inbred strains of male laboratory rat (BN/HsdCpb, BDIX/Or1Ico and LEW/Mol) were provided with nest boxes and nest materials, and were observed for nest-building activity. After 7 days, each cage and nest box was examined. Each nest was weighed and scored for complexity, and returned
to the cage. This was repeated after a further 7 days and the nest removed completely. This routine was repeated three times. All three strains of rat built nests inside the nest box and showed the same stages of construction. There was a significant increase in nest complexity between day
7 and day 14 in the strains BN and BDIX. Furthermore, BDIX rats used significantly more material for the nests, compared with the BN and LEW rats. In a second experiment, using the same rats, nest material was offered in four different ways. LEW rats used nesting material irrespective of where
it was placed; BN rats only used straw placed on the top of the cage when no alternative was provided in the cage, and would not use the nest box roof when it was covered with bedding; whereas BDIX rats would only use nest material placed within the cage and would not use straw placed on the
cage lid. BN rats also used nest material to cover the entrance to the nest box, a practice not carried out by the other strains. This study demonstrates that these rat strains have retained their natural nest-building behaviour. We suggest that the correct stimuli must be provided in order
for this behaviour to be exhibited; in addition, the way in which the nest materials are provided must be in accordance with strain-specific characteristics.