Table 2.

Ethograms of rat behavior in the home-cage.

Behavioral Element	Description
Social play	One animal approach and soliciting another (pouncing; attempt to nose or rub of the neck of the partner), chasing the partner, crawling over/under, boxing, wrestling, pinning (lying with the dorsal body surface on the floor with the other animal standing over it), and lateral display
Social investigation (sniffing)	Sniffing of the any part of the body of the cage-partner
Allogrooming	The grooming of one animal by another
Huddling	The presence of at least 2 animals, resting or sleeping while maintaining close physical contact with the partner
Following	Walking or running in the direction of the partner moving away
Self-grooming	Repeatedly cleaning the body fur using forelimbs beginning with the snout, progressing to the ears and ending with whole body grooming
Walking	Leg movement enabling the animal's slow pace across the floor
Solitary resting	Immobile and not in contact with cage partner
Rearing	Standing on the hind paws and stretching the body while sniffing the air from the upper part of the cage
Digging	Pushing, pulling or kicking bedding material away and around using the snout and/or both the forepaws and hind paws