Ranging behavior and potential for territoriality in equatorial sakis (Pithecia aequatorialis) in Amazonian Ecuador

Abstract

ObjectivesTerritoriality refers to the consistent defense of an area within the home range (HR) against intrusions of conspecifics. It implies exclusive space use with low degree of overlap among neighboring groups, high site fidelity, specific ranging behavior such as high mobility relative to HR size and frequent visits of territory borders, and monitoring behavior. We examined ranging behavior and use of space to evaluate territoriality in Pithecia aequatorialis in Ecuador.Materials and methodsBetween 2005 and 2015, we monitored one main study group continuously and five additional groups for shorter periods (5 months to 2.5 years) at the Tiputini Biodiversity Station, in eastern Ecuador. We scored the location of the study groups at 20 min intervals during, on average, 5 days per month. We estimated saki HRs and core areas (CAs) using the fixed kernel density method (95 and 50%, respectively).ResultsThe average HR size was 57 ha and the average CA 14 ha. The degree of overlap between HRs of neighboring groups was low (2–9%). For the main study group, the average overlap between annual HRs was 82%. Mean daily path length across groups was 1,151 m; the defensibility index varied between 1.1 and 2.3 (values >1 are suggestive of territoriality), and the fractional monitoring rate varied between 0.06 and 0.15 (values >0.08 are suggestive of territoriality). Groups did not visit their HR borders (100 m inner buffer) more often than would be expected by chance. Travel speed and directness were comparable between the borders and the centers of groups' HRs.DiscussionOur multiyear study suggests that equatorial sakis show low degree of range overlap and high site fidelity and have the potential to be territorial, given their high mobility relative to HR size that allows for frequent border monitoring. Nevertheless, their movement patterns in border areas did not reveal evidence for monitoring behavior.

The evolution of pair‐living, sexual monogamy, and cooperative infant care: Insights from research on wild owl monkeys, titis, sakis, and tamarins

“…Similarly, in our studies of P. discolor and P. aequatorialis in Ecuador, we have been unable to adequately estimate the full extent of home range overlap between our study groups and all their neighboring groups because of the difficulty of habituating and following individuals in neighboring groups not under study. For these two species, the mean annual home range overlap between pairs of groups (sakis: mean = 5.0%, range = 3–8%, Van Belle et al, ; titis: mean = 4.8%, range = 0–13%, Van Belle et al, in preparation) is well below the mean of 21% (median = 17%) home range overlap calculated by Lukas and Clutton‐Brock () for “social monogamous” mammals and of 49% (median = 58%) for solitary females.…”

“…This was done either by using a GPS unit, by measuring the distance and direction of the location of the group or individual in relation to a previously georeferenced location nearby (i.e., a mapped feeding or sleeping tree or a trail point), or by extracting the group's location from an observer's own GPS track record when following a group. A quantitative evaluation of the accuracy of these methods indicated that the mean distance between pairs of points ( N = 4,451) obtained from the observers' GPS tracks and points taken with a GPS unit or measured relative to previously georeferenced markers was 9.0 m ( SD = 12.4; range = 0–109 m; median = 5.0 m: Van Belle et al, ). We used the fixed kernel density method (Seaman & Powell, ) to estimate home ranges as the 90 or 95% kernel isopleth of the set of location records (Figure , Huck & Fernandez‐Duque, ; Van Belle et al, ; Van Belle, Porter, Fernandez‐Duque, & Di Fiore, in preparation; Wartmann, Juárez, & Fernandez‐Duque, ).…”

“…The Socioecology of Monogamous Primates Project was started by AD and EFD in 2003 to study similarities and differences in the ecology and expression of pair‐living, male–female social relationships, and patterns of parental care in three genera of pair‐living and seemingly sexually monogamous platyrrhines ( Pithecia , Plecturocebus , and Aotus ) living in the same tropical environment, the lowland Amazon rainforest of the Yasuní Biosphere Reserve in Ecuador (Figures a and ). SVB joined this project in 2014 to work on aspects of range use and intergroup interactions, as well as on the genetic mating system of equatorial sakis ( Pithecia aequatorialis ) and red titis ( Plecturocebus discolor ) (Van Belle, Fernandez‐Duque, & Di Fiore, ; Van Belle, Porter, Fernandez‐Duque, & Di Fiore, ).…”

Long‐term movements and home‐range changes: Rapid territory shifts in meerkats

“…Changes in space use are then usually calculated as differences between these summaries across successive periods, typically years (e.g. Jolly & Pride, ; Keuling et al, ; Smulders et al, ; Van Belle, Porter, Fernandez‐Duque, & Di Fiore, ; Zengeya, Murwira, & Garine‐Wichatitsky, ). These measures are sometimes combined with the same measure over longer periods (e.g.…”

“…Most have found an absence of substantial range shifts. A recent study on equatorial sakis ( Pithecia aequatorialis ) for example found a high overlap between annual ranges and interpreted this high site fidelity as a product of territoriality (Van Belle et al, ). Similarly, a group of white‐handed gibbons ( Hylobates lar ) was found to show high stability of homeranges over a 10 year period (Bartlett, Light, & Brockelman, ).…”