Table 1.

Summary of biological and social functions of rat ultrasonic vocalizations.

Function of Vocalization	Type of Calls	Deduced Valence	Selected References
Mother–infant communication
Self-preservation function	Isolation calls	Negative	[22,24]
Locating function	Isolation calls	Negative	[30,31,32,33,34,36,48]
Protective function	Isolation calls	Negative	[53,56]
Non-agonistic adult social interactions
Phatic communication function	50 kHz calls	Positive	[60,61,63]
Affiliative function	50 kHz calls	Positive	[63,64,65,67,80]
Passive defensive function	22 kHz or 50 kHz	Negative or positive	[82]
Socio-coordinating function	Flat 50 kHz	Positive	[43,84]
Social buffering function	50 kHz calls	Positive	[66,80,81]
Investigative function	50 kHz calls and Short 22 kHz	Positive or negative	[100,102,103]
Social play and teamwork
Ludic function	FM 50 kHz calls	Positive	[99,103,104,107,108,109]
Conative function	50 kHz calls	Positive	[48,49]
Cooperative function	50 kHz calls	Positive	[121,122,123]
Intraspecies agonistic interactions
Agonistic function	22 kHz calls	Negative	[75,126,127,128,130]
Appeasement function	Long 22 kHz calls	Negative	[99,126,127,136,137]
Reproductive behavior
Mating function	50 kHz or 22 kHz	Positive or Negative	[73,123,139,140,141,147]
Social detachment function	Long 22 kHz calls	Negative	[123,148,149,150,151,152,153,154,155]
Alimentary behavior
Alimentary function	Flat 50 kHz calls	Positive	[164,166]
Food provisioning function	Flat 50 kHz calls	Positive	[167]
Defense against external threat
Alarming function	Long 22 kHz calls	Negative	[168,169,170,171,177,188]
Warning function	Long 22 kHz calls	Negative	[191,192,193,194,195,196,197,198,199,200,201]
Security function	Long 22 kHz calls	Negative	[205]
Expression of internal discomfort and frustration
Frustration expression function	Short 22 kHz calls	Negative	[148,157,213,214,215,216,217]