Norberto Asensio

Intragroup aggression, fission–fusion dynamics and feeding competition in spider monkeys

Scramble competition is related to animals depleting resources before others can use them, whereas contest competition is associated with the monopolization of resources and food-related aggression. One hypothesized major benefit of fission–fusion sociality is the reduction of scramble feeding competition between community members. We studied intragroup aggression in a community of spider monkeys. Despite seasonal variation in food availability, we found no seasonal difference in aggression rates, which, in combination with a basic lack of aggression among adult females, suggests that fission–fusion dynamics may reduce not only scramble, but also the intensity of contest competition. There were, however, numerous attacks from adult females towards subadult females, especially new immigrants. This aggression, although it occurred mainly during feeding, may not reflect contest competition. Instead, it may be used by resident females to limit scramble competition at the community level, which is ultimately affected by the number of community members. The aggressive harassment of subadult females by long-term resident females can be a means to encourage dispersal of natal subadult females and discourage immigration of new subadult females who are both potential future resource competitors.

Fissioning minimizes ranging costs in spider monkeys: a multiple-level approach

The adjustment to deal with intragroup food competition is probably the most plausible explanation of high levels of fission–fusion dynamics. However, studies did not always support expected relations between food availability, ranging costs, and subgroup size. We used several levels of analysis differing in the time and spatial scale in order to investigate this explanation in spider monkeys. In our study, subgroups were larger when food availability was higher across most levels of analyses used. We also found a fine-scale adjustment: compared to the food patch previously visited, spider monkeys traveled to larger patches just after fusions. This was not without an immediate travel cost: the interpatch distance and travel time after a fusion were longer than that before the fusion. This rapid adjustment shows the flexibility that fission–fusion dynamics can offer. Spider monkeys are in large subgroups only when food conditions are favorable, as evidenced by the fact that at all the other time-scale levels larger subgroups did not experience greater ranging costs than smaller subgroups. Our results indicate that on the whole spider monkeys successfully minimize ranging costs by fission and fusion of subgroups.

Gibbon travel paths are goal oriented

Remembering locations of food resources is critical for animal survival. Gibbons are territorial primates which regularly travel through small and stable home ranges in search of preferred, limited and patchily distributed resources (primarily ripe fruit). They are predicted to profit from an ability to memorize the spatial characteristics of their home range and may increase their foraging efficiency by using a ‘cognitive map’ either with Euclidean or with topological properties. We collected ranging and feeding data from 11 gibbon groups (Hylobates lar) to test their navigation skills and to better understand gibbons’ ‘spatial intelligence’. We calculated the locations at which significant travel direction changes occurred using the change-point direction test and found that these locations primarily coincided with preferred fruit sources. Within the limits of biologically realistic visibility distances observed, gibbon travel paths were more efficient in detecting known preferred food sources than a heuristic travel model based on straight travel paths in random directions. Because consecutive travel change-points were far from the gibbons’ sight, planned movement between preferred food sources was the most parsimonious explanation for the observed travel patterns. Gibbon travel appears to connect preferred food sources as expected under the assumption of a good mental representation of the most relevant sources in a large-scale space.

Foraging Habits of Alouatta palliata mexicana in Three Forest Fragments

The activity patterns and diet of howler monkeys (Alouatta palliata mexicana) were studied in 3 forest fragments in south-eastern Mexico: Playa Escondida (PLA), Agaltepec Island (AGA) and Arroyo Liza (LIZ). Intersite differences offered the opportunity to investigate the foraging adaptations of howler monkeys in response to population and habitat size. In the largest fragment (PLA), the howlers’ diet was based on high-quality items (fruit and young leaves). In AGA, where the density of howlers was the highest, their diet was mostly folivorous with a marked exploitation of uncommon food items such as vines, lianas, shrubs and herbs. The dietary differences in AGA were accompanied by more time spent travelling and less time spent resting. Although LIZ was the smallest fragment and had a high howler density, the small group size and the use of energy-minimizing strategies (less time spent travelling and more time spent resting) probably allowed howlers to maintain a frugivorous diet.

Variability in core areas of spider monkeys (Ateles geoffroyi) in a tropical dry forest in Costa Rica

Core areas are highly used parts of the home range on which the survival of solitary or group-living animals depends. We investigated the home range and core area size and area fidelity of a spider monkey community in a tropical dry forest over a 4-year period. Home ranges overlapped extensively across years, subgroup sizes, and seasons. In contrast, spider monkeys used core areas that varied in size and location across the study years, subgroup sizes, and seasons. These shifts in core areas suggest that the understanding of core areas, and thus the spatial requirements, of a species in a particular habitat may be limited if based on short-term studies. In this respect, our findings emphasize the importance of long-term studies of the spatial ecology of any species in a particular habitat. Our study also shows that the yearly home range basically includes all the core areas from different years, seasons, and subgroup sizes (i.e., the super-core area). This is conceptually important for territorial species, such as spider monkeys, which defend a stable home range as it contains not only the current, but also the future core areas.

Ranging and site fidelity in northern pigtailed macaques (Macaca leonina) over different temporal scales

Space‐use patterns are crucial to understanding the ecology, evolution, and conservation of primates, but detailed ranging data are scarce for many species, especially those in Southeast Asia. Researchers studying site fidelity to either home ranges or core areas have focused mainly on territorial species, whereas less information is available for non‐territorial species. We analyzed the ranging patterns and site fidelity of one wild troop of northern pigtailed macaques over 16 months at different temporal scales. We used characteristic hull polygons in combination with spatial statistics to estimate home ranges and core areas. The total home range and core areas were 449 ha and 190 ha, respectively. Average daily path length was 2,246 m. The macaques showed a high defendability index according to the expected ranging of a non‐territorial species in which movement does not theoretically permit the defense of a large territory. Overall, the study troop ranged more extensively than conspecific groups and closely related species studied elsewhere. These differences may reflect variable troop size, degree of terrestriality and habitat characteristics, but could also reflect methodological differences. The location, size and shape of home ranges and core areas, and extent of daily path lengths changed on a monthly basis resulting in low site fidelity between months. The macaques also showed clear shifts in the location of daily home ranges with low site fidelity scores between consecutive days. Daily home range and daily path length were related to seasonality, with greater values during the fruit‐abundant period. Low site fidelity associated with lack of territoriality is consistent with macaques structuring their movement based on available food sources. However, ranging patterns and site fidelity can also be explained by macaques feeding on the move, a foraging strategy that hinders frequent and long visits to the same location. Am. J. Primatol. 77:841–853, 2015.

Feeding encounters between a group of howler monkeys and white-nosed coatis in a small forest fragment in Los Tuxtlas, Mexico

Interactions between sympatric species are of particular interest for understanding the mechanisms that allow animal coexistence in the ecological community. The mantled howler monkey ( Alouatta palliata Gray) and the white-nosed coati ( Nasua narica Linnaeus) are similar-sized mammals with a sympatric distribution in the Neotropics (Nowak 1999). Since these two species are partly frugivorous (howler, Crockett & Eisenberg 1987; coati, Gompper 1997), and fruit is often limited (Laurance et al . 2003), howlers and coatis might be observed foraging from the same fruiting tree, but there is no information regarding this possibility. We studied the feeding encounters between these two species in a small forest fragment, and discuss the conditions under which these episodes occur.

Spatio-temporal patterns of leptospirosis in Thailand: is flooding a risk factor?

SUMMARY We studied the temporal and spatial patterns of leptospirosis, its association with flooding and animal census data in Thailand. Flood data from 2010 to 2012 were extracted from spatial information taken from satellite images. The incidence rate ratio (IRR) was used to determine the relationship between spatio-temporal flooding patterns and the number of human leptospirosis cases. In addition, the area of flood coverage, duration of waterlogging, time lags between flood events, and a number of potential animal reservoirs were considered in a sub-analysis. There was no significant temporal trend of leptospirosis over the study period. Statistical analysis showed an inconsistent relationship between IRR and flooding across years and regions. Spatially, leptospirosis occurred repeatedly and predominantly in northeastern Thailand. Our findings suggest that flooding is less influential in leptospirosis transmission than previously assumed. High incidence of the disease in the northeastern region is explained by the fact that agriculture and animal farming are important economic activities in this area. The periodic rise and fall of reported leptospirosis cases over time might be explained by seasonal exposure from rice farming activities performed during the rainy season when flood events often occur. We conclude that leptospirosis remains an occupational disease in Thailand.

Interactions of Howler Monkeys with Other Vertebrates: A Review

Understanding the way howler monkeys interact with other vertebrates has critical ecological, evolutionary, cognitive, and conservation implications. In this review, we completed an extensive search of the available data on interspecific howler encounters, including individual communications from field primatologists, in order to gain insight into how howlers share their habitat and interact with other species, the pressure that predators and potential competitors may exert on them, and the potential benefits and costs that howlers may represent for other species. Howlers interacted with several vertebrates throughout their distribution range, including birds and mammals, particularly capuchin monkeys, spider monkeys, and coatis. A great deal of these interactions occurred in fruiting trees and were, in general, pacific, although howlers were frequently harassed by other monkeys, and they were observed behaving aggressively with coatis and birds. Howlers were also targets of multiple predators. Among them, large felids and harpy eagles are ranked as the prevalent natural predators of this primate taxon. Finally, evidence indicates that the transformation of natural habitats can have important effects on the interaction patterns of howlers with other species. Fragmentation can increase competition for food and in extreme cases even force them to predate on eggs to compensate for the reduction in food availability. On the other hand, natural predators are often absent in anthropogenic landscapes, but there are increasing reports of predation by dogs and coyotes, which could potentially have very negative effects on the already highly threatened populations of howler monkeys in fragmented landscapes.

Quality and overlap of individual core areas are related to group tenure in female spider monkeys

In species with a high degree of fission‐fusion dynamics group members may differ in the use of the group home range to reduce food competition. Such differential use may result in distinct individual core areas. We studied core area quality and overlap among 21 female spider monkeys belonging to the same group over a period of 4 years. Core areas ranged between 62 and 161 ha with a mean overlap of 56% between any given two females. Only a small portion (mean = 3 ha) of each individual core area was used exclusively. No single part of the home range was used as core area by all females, and only an area of less than 1 ha was used as part of the core area by 20 of the 21 females. The time a female spent in the group (i.e., group tenure) was associated with characteristics of the core areas: the longer the group tenure, the better the quality of her core area. In addition, the longer the time two females spent together in the same group, the larger the overlap between their individual core areas. As this result was obtained while controlling for the time two females spent together in the same subgroup, females may reduce direct competition by using the same resource at different times. In sum, spider monkey females’ group tenure plays a central role in the quality and overlapping patterns of their individual core areas. Am. J. Primatol. 77:777–785, 2015.