title: Evolution: Big Bawls, Small Balls.
abstract: Males must carefully allocate the energy they devote to sex. A new study of howler monkeys shows that males who use vocalizations to ward off rivals invest less in producing large numbers of sperm.
authors.affiliation: Computational and Evolutionary Biology, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK. Electronic address: john.fitzpatrick@manchester.ac.uk.
authors.forename: John L
authors.initials: JL
authors.lastname: Fitzpatrick
authors.affiliation: Computational and Evolutionary Biology, Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK. Electronic address: sluepold@gmail.com.
authors.forename: Stefan
authors.initials: S
authors.lastname: Lüpold
mesh_terms: D000508:Alouatta; D000818:Animals; D005075:Biological Evolution; D013094:Spermatozoa