Definition of "rrah"

Struhsaker has recorded at least five different distress calls by infant vervets related to mother-infant separation. As the distance between mother and infant increases the "rrah" call changes to "eee" or "rrr" with an increase in intensity.

1983, William C. Stebbins, The Acoustic Sense of Animals, page 140

Even the impressive vervet monkey has only thirty-six distinct vocal sounds in its repertoire. […] An infant separated from its mother gives the lost rrah cry.

2011, Jean Aitchison, The Articulate Mammal: An Introduction to Psycholinguistics, page 25