Hank the Cowdog and Monkey Business is the 14th book in the Hank the Cowdog series written by John R. Erickson. It was published in 1990.
Plot
A convoy of circus trucks is passing through the ranch. The last truck in the column hits a bump and a large red box falls off and comes to rest in the pasture. Hank and Drover investigate the box and discover that it contains a circus monkey. Pete advises Hank not to open it, but Hank's curiosity gets the best of him.
References
Hank the Cowdog and Monkey Business Wikipedia(Text) CC BY-SA