, Volume 49, Issue 2, pp 149–152 | Cite as

Wild mixed groups of howler species (Alouatta caraya and Alouatta clamitans) and new evidence for their hybridization

  • Lucas M. AguiarEmail author
  • Marcio R. Pie
  • Fernando C. Passos
Short communication


Mixed species groups and hybridization are common among primates, yet these phenomena are rare and poorly understood for the genus Alouatta. In this study, we describe the composition of howler groups in a sympatric area of Alouatta caraya and Alouatta clamitans and provide new evidence for the occurrence of interspecific hybridization. Between October 2006 and April 2007, 11 howler groups were located in a 150-ha forest fragment: two monospecific groups of A. caraya, two monospecific groups of A. clamitans, two groups composed of A. clamitans and hybrid morphotypes (A. caraya × A. clamitans), and five groups composed of both species together with hybrid morphotypes (mixed species groups). The average size of the studied groups was 5.2 ± 1.2 individuals. Monospecific and mixed groups (mixed species groups + groups with hybrids) did not differ significantly in their sizes. In total, the sex/age ratios were 1 AM:1.5 AF:0.2 SAM:0.5 JUV:0.2 INF and the species ratios were 1 A. caraya:1.6 A. clamitans:0.4 A. caraya × A. clamitans. The ratio of immatures to 1AF was larger in the monospecific groups (0.75 immatures:1AF) than in mixed groups (0.29 immatures:1AF), possibly reflecting a lower viability in the latter. Two features of the hybrid morphotypes of the upper Paraná River support their status as true hybrids: the polymorphism of their coloration patterns and the extremely female-biased sex ratio. The effects of Haldane’s rule and population fragmentation on the interactions between both species are discussed.


Fragmentation Haldane’s rule Hybrid zone Sympatry Sex ratio 



We thank CNPq for a scholarship to LM Aguiar and for a research grant to FC Passos, APA Municipal de Alto Paraíso, Ilha Grande National Park, nine research assistants for help during field work, IBAMA for permit 261/2006, and two anonymous reviewers for helpful suggestions about the manuscript. JMD Miranda provided valuable statistical advice.


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Copyright information

© Japan Monkey Centre and Springer 2007

Authors and Affiliations

  • Lucas M. Aguiar
    • 1
    Email author
  • Marcio R. Pie
    • 2
  • Fernando C. Passos
    • 1
  1. 1.Programa de Pós-graduação em Zoologia, UFPR, Laboratório de Biodiversidade, Conservação e Ecologia de Animais Silvestres, Departamento de ZoologiaUniversidade Federal do ParanáCuritibaBrazil
  2. 2.Laboratório de Ecologia Molecular e Parasitologia Evolutiva, Departamento de ZoologiaUFPRCuritibaBrazil

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