Evolution: Big Bawls, Small Balls John L. Fitzpatrick, Stefan Lüpold  Current Biology  Volume 25, Issue 22, Pages R1084-R1086 (November 2015) DOI: 10.1016/j.cub.2015.09.060 Copyright © 2015 Elsevier Ltd Terms and Conditions

Figure 1 A howler monkey in the Brazilian Amazon. A male Spix’s red-handed howler monkey (Alouatta discolor) with clearly visible testes descending a tree in the south-eastern Amazon in Brazil. A recent study [5] sheds light on the evolutionary link between male investment in testes and vocalizations in howler monkeys. (Photo: Charles Cruze, Wikimedia Commons.) Current Biology 2015 25, R1084-R1086DOI: (10.1016/j.cub.2015.09.060) Copyright © 2015 Elsevier Ltd Terms and Conditions