The Roaring of Southern Brown Howler Monkeys (Alouatta guariba clamitans) as a Mechanism of Active Defence of Borders

Abstract

Our study aimed to understand the function(s) of roars of southern brown howler monkeys (Alouatta guariba clamitans). The study group called almost exclusively on its range borders and preferentially on early mornings, but with no dawn peak. Intergroup encounters were associated with 88% of all sessions. Predation deterrence and regulation of access to mating partners do not seem compatible with our findings, but more work is needed to reject the latter hypothesis. Their roars seem to be related to intergroup spacing, but through an active defence of borders, instead of mutual avoidance or regular advertisement of occupancy, as proposed for other howler monkey species.

Roaring Behavior of Two Syntopic Howler Species (Alouatta caraya and A. guariba clamitans): Evidence Supports the Mate Defense Hypothesis

“…Finally, howlers of both species at our study site had a low howling rate when compared to howler groups elsewhere (Chiarello 1995;da Cunha and Byrne 2006;da Cunha and Jalles-Filho 2007). This difference may result from the low population density at El Piñalito: 0.10 ind/ha for brown howlers and 0.15 ind/ha for black-and-gold howlers (Agostini et al 2010b).…”

Howling on the edge: Mantled howler monkey (Alouatta palliata) howling behaviour and anthropogenic edge effects in a fragmented tropical rainforest in Costa Rica

“…Seasonality affects howling patterns in other howler monkey species, with more howling during lower resource availability, potentially to defend available resources (ursine howler, Sekulic, ; black howler, Horwich & Gebhard, ; Guianan red howler, Drubbel & Gautier, ; brown howler, Chiarello, ). Howler monkeys also vary in howling behaviour within home ranges, with some species howling more often in core territory areas (black‐and‐gold howler, da Cunha & Byrne, ) and other species howling more often in border areas (black howler, Horwich & Gebhard, ; Guianan red howler, Drubbel & Gautier, ; brown howler, da Cunha & Jalles‐Filho, ). The mantled howler monkey howled at greater rates near home range borders (Altmann, ); however, Hopkins () found that howling bout responses were best understood in the light of inter‐group dominance interactions coupled with food availability, with monkeys more often approaching other howling groups during times of food scarcity, presumably to gain access to their food‐rich range area.…”

A flume experiment to examine underwater sound generation by flowing water

“…Indeed, sound has been subject of intense scientific research. For example, acoustic techniques have been successfully applied to determine constraints upon acoustic communication in the aerial environment (Ellinger and Hödl 2003), for studying social communication among organisms (Slater and Catchpole 1990;Ruiz-Miranda et al 2002;Da Cunha and Jalles 2007), and for determining the effect of anthropogenic noise on birds (Reijnen et al 1997;Forman et al 2002), bears (Gibeau et al 2002;Dyck and Baydack 2004), amphibians (Sun and Narins 2005), and squirrels (Rabin et al 2006). Research has also examined the human perception of sound (Southworth 1969;Carles et al 1999), coupling visual and acoustic preferences (Anderson et al 1983;Porteous and Mastin 1985;Yang and Kang 2005), in order to better understand noise as an impairing sound (Kariel 1990;Staples 1997;Gramann 1999).…”