Fragmented living: Behavioural ecology of primates in a forest fragment in the Lopé Reserve, Gabon

A 17-month study was made of the primates using a 9-ha “island” of forest, surrounded by savanna, in the northern part of the Lopé Reserve, Gabon. One group ofCercopithecus cephus (plus a young maleCercopithecus nictitans who was in permanent association with them) were resident in the fragment and groups of five other species of primates made visits during 127 days of observation:Pan troglodytes, 15 visits;Cercocebus albigena, 10;Colobus satanas, 3;Cercopithecus nictitans, 2;C. pogonias, 1. Visits were also made by lone males of three species,C. nictitans, Cercocebus albigena, andMandrillus sphinx. The eighth species of diurnal primate present at Lopé,Gorilla g. gorilla, did not visit the fragment during the study. Compared to conspecific groups in neighbouring continuous forest, primates in the fragment ate less fruit, seeds and flowers and more insects and leaves. The local population density of primates resident in the fragment was equivalent to that of the neighbouring continuous forest where all eight species occur, despite the diversity and abundance of fruit being less in the fragment. The costs imposed on the resident group by the reduced diversity and availability of preferred fruit foods appeared to be offset by a number of benefits that increased individual feeding efficiency for monkeys residing within a single fragment. These included lower travel costs, reduced feeding competition between individuals through group fission, and excellent knowledge of the location and quality of food resources in the small home range. It is also possible that the overall negative impact of inter-specific feeding competition was lower in fragments than in continuous forest and that micro-habitat differences resulted in an increased availability of palatable insect and leaf fallback foods in the fragment.     

Associations between the drill (Mandrillus leucophaeus) and sympatric monkeys in Korup National Park,Cameroon

Studies of polyspecific associations among African forest primates have primarily focused on arboreal Cercopithecus and Procolobus/Colobus species. We examined the association frequency of the terrestrial drill (Mandrillus leucophaeus) with six sympatric monkey species in Korup National Park, Cameroon, testing reports that Mandrillus associations are infrequent and transient. We conducted 3,284 km of trail walks for 12 months (February–June 2006; July 2007 to January 2008), recording species composition in 612 primate clusters. Using a Markov chain Monte Carlo test, we compared the observed frequency of dyadic associations against null models of “no association.” A novel conservative statistical approach which addresses possible dependence of observations close in time was also used, further strengthening confidence in our findings. Drills associated with all monkeys throughout the study period, and were with at least one other species (range 1–5) in half of the encounters. The association frequency of drills with red‐capped mangabeys (Cercocebus torquatus) was greater than expected by chance, which is interesting given the morphological adaptation of the Mandrillus‐Cercocebus clade for the exploitation of the same dietary niche, hard seeds. The difference we observed in the use of forest strata by drills and mangabeys may reflect a strategy to reduce food competition while in association. The nature and duration of observed drill associations varied. Although some associations seemed to be chance encounters, others lasted for hours with the involved species foraging together. Am. J. Primatol. 73:127–134, 2011. © 2010 Wiley‐Liss, Inc.     

Distribution and Forest Utilization of Saguinus and Other Primates of the Pando Department, Northern Bolivia

We carried out a 4-month census of primates in the Pando Department of northern Bolivia with special emphasis on Saguinus species. Contrary to a previous report by Izawa and Bejarano (1981), there was no evidence for the presence of the two populations of Saguinus mystax that they reported, or that Lagothrix occurs in the Pando. In addition, we found the distribution of Saguinus imperator to be more restricted than they suggested. We confirm the presence of Cebuella south of the Río Tahuamanu (cf. Brown and Rumiz, 1986) and report two new locations for Callimico goeldii. We present data on group sizes, habitat utilization, and locomotor behavior of the primates and compare them with previous studies in the Pando. Differences in body size, diet, foraging techniques, and vertical use of the forest appear to be key factors in both sympatry and in the formation of polyspecific associations.     

Polyspecific associations and niche separation of rain-forest anthropoids in Cameroon, West Africa

A 19 month field study of rain-forest anthropoids at Idenau and several other rain forests, and a similar 15 month study at Southern Bakundu were conducted in Cameroon, West Africa. The study areas and their primate fauna are described. Polyspecific associations of primates were temporary, but not random, some species occurring together more frequently than others, and with statistical significance. Seasonal environmental factors affecting the composition of polyspecific cercopithecid associations are described. Interspecific social behaviour was infrequent and hybridization rare; instances of each are described. Observations on vertical stratification, habitat preference, seasonal movements and food habits indicated that all these factors contribute to niche separation among five sympatric species of rain-forest Cercopithecus. The major predator of anthropoids in Cameroon is man. To a much lesser extent the Crowned hawk-eagle, Stephanoaëtus coronatus (Linnaeus) preys on Cercopithecus species. It is suggested that polyspecific associations, by increasing the effective group size, give advantages in food location and avoidance of predators without increasing interspecific competition for food and competition between males for females.     

Habitat Partitioning Among Primates in Maracá Island, Roraima, Northern Brazilian Amazonia

I studied a primate community on a tropical rainforest island, in the northernmost area of the Brazilian Amazonia. While walking through six distinct habitats along a 12-km trail, running toward the center of the island—a remote undisturbed area—I collected data on the use of the different forest types and forest strata by the primate community and the formation of either mixed groups or species assemblages. Five species are present: Cebus olivaceus, C. apella, Saimiri sciureus, Ateles belzubuth, and Alouatta seniculus. They seemed to be habitat generalists, using most habitat types. The five species used the higher strata more significantly, probably because Maracá does not present well-defined forest floors, which could be a result of being located in the transition between the great areas of savannah and the Amazonian seasonally dry forests. The five species all formed some polyspecific associations, which involved sharing the available food resource. Mixed groups were significantly more frequent and therefore possibly more important to Saimiri, which was not the case in relation to the other four species. Assemblages, defined as the presence in the same clumped resource, without coordinated activity, of 3 primate species, were recorded primarily in fruiting fig trees. I suggest that assemblages are impelled by food constraints, forcing cofeeding in large seasonal resources, highlighting the ecological importance of figs to these primates. Linear regression models show that the number of feeding bouts in each habitat type is positively related to the number of fruiting trees exploited, but the density of these fruit trees, diversity of plant species, tree height, and total basal area of each habitat type have no relationship to feeding.     

Why Do Dolphins Form Mixed‐Species Associations in the Azores?

Mixed‐species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed‐species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed‐species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed‐species groups were compared with those of single‐species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed‐species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed‐species groups depends on several environmental factors, and therefore may constitute an adaptive response.     

Mixed-species primate groups in the kibale forest: Ecological constraints on association

Five species of diurnal primates in the Kibale Forest of western Uganda— red colobus (Colobus badius),black- and- white colobus (Colobus guereza),redtail monkeys (Cercopithecus ascanius),blue monkeys (Cercopithecus mitis),mangabeys (Cercocebus albigena)-often associate in mixed- species groups that vary in size and composition from day to day. Across this range of species, we found no consistent effect of association on feeding rate. In addition, there is no systematic difference between the species- specific individual feeding rates when animals were in mixed- species groups feeding in a specific tree on one day and when individuals of one of the same species were feeding in the same individual tree on a subsequent day. If associating in a mixed- species group lowers the risk of predation, one might expect that the number of vigilant events would decrease in mixed- species groups. However, the only species to exhibit a consistent decrease in vigilant behavior when in association was the red colobus. Redtail monkeys were more vigilant when in association. We predicted that the density and distribution of food resources would both constrain the frequency of association and the size of mixed- species groups. Based on 22 months of data on food resources and bimonthly censuses, we found no relationship between the frequency of association (except mangabeys) or mean mixed- species group size and the density and distribution of food resources for all species. Finally, we examined the behavior of the monkeys in and out of association before and after the playback of a crowned hawk eagle call (Spizaetus coronatus),a known predator. When more species were in association, the amount of time they spent being vigilant following the playback was greater and the response more intense than when fewer species were in association or when the group was alone. The results of this study illustrate that the nature of the costs and benefits of polyspecific associations for these different monkey species are complex and vary from species to species.     

Time allocation of bison in meadow patches driven by potential energy gains and group size dynamics

Understanding the behavioural mechanisms involved in broad‐scale spatial organisation of grazing herbivores requires uncovering the factors controlling foraging decisions, such as patch residency time. Foraging theory specifies that rate maximizers must simultaneously consider both the optimal residency time in a food patch and the optimal diet. Specifically, resource depletion or spatial variation in food type availability should not influence food choice, but only patch residency time. Few studies, however, have tested these principles together, and none on free‐ranging large herbivores. We evaluated the combined effects of forage characteristics, predation risk, and group size on residency time by free‐ranging bison Bison bison in summer. We hypothesized that residency time in meadows would increase with the availability of Carex atherodes, a highly profitable plant species maximizing energy intake rate, but decrease with sward complexity (i.e. plant species composition and structure) within foraging stations. We also anticipated that predation risk and group size would influence the relationship between vegetation characteristics and residency time. Residency times were measured in 44 sites using cameras located at meadow edges. We determined that residency time in meadows varied with meadow area, group size, biomass of C. atherodes available on the area, and proportion of C. atherodes within foraging stations. We found that the likelihood of departure decreased with an increase in the total biomass of C. atherodes available over the meadow, an effect attenuated by an increase in group size. Residency time in meadows was also influenced by plant species composition, with higher accessibility of C. atherodes within feeding stations increasing residency time. We found little evidence, however, that sward structure and predation risk influenced residency time. Overall, our study demonstrated that the search for rapid energy gains, together with the constraints imposed by group living, can explain time allocation in habitat patches by large gregarious herbivores.     

Primate Community Structure in Guyana: A Biogeographic Analysis

Studies of primate community structure increase our understanding of behavior, adaptation, and evolution. However, there are few biogeographic data on specific composition and association patterns in primate communities. I conducted a biogeographic analysis of the community structure of primate species at 16 sites in Guyana. I used data from 1725 km of line-transect censuses to determine specific composition and association patterns of 220 primate groups . Of the 18 polyspecific groups, 94.1% (N = 16) included squirrel monkeys. There was an overall trend towards positive specific associations among Guyanese primates. The only species that exhibited a negative pattern of interspecific associations were brown and wedge-capped capuchins. The sighting rate for wedge-capped capuchins at sympatric sites was particularly depressed compared to that for brown capuchins. Low plant productivity in Guyanese forests may reduce the diversity of feeding niches and result in a low incidence of polyspecific associations and scramble competition between wedge-capped and brown capuchins.     

Flight is the key to postprandial blood glucose balance in the fruit bats Eonycteris spelaea and Cynopterus sphinx

Excessive sugar consumption could lead to high blood glucose levels that are harmful to mammalian health and life. Despite consuming large amounts of sugar‐rich food, fruit bats have a longer lifespan, raising the question of how these bats overcome potential hyperglycemia. We investigated the change of blood glucose level in nectar‐feeding bats (Eonycteris spelaea) and fruit‐eating bats (Cynopterus sphinx) via adjusting their sugar intake and time of flight. We found that the maximum blood glucose level of C. sphinx was higher than 24 mmol/L that is considered to be pathological in other mammals. After C. sphinx bats spent approximately 75% of their time to fly, their blood glucose levels dropped markedly, and the blood glucose of E. spelaea fell to the fast levels after they spent 70% time of fly. Thus, the level of blood glucose elevated with the quantity of sugar intake but declined with the time of flight. Our results indicate that high‐intensive flight is a key regulator for blood glucose homeostasis during foraging. High‐intensive flight may confer benefits to the fruit bats in foraging success and behavioral interactions and increases the efficiency of pollen and seed disposal mediated by bats.     

Seasonal dynamics of resource partitioning among foliage-gleaning passerines in northern Finland

Summary The five most abundant species were included in a year-round study with respect to six foraging niche dimensions. Approximately full multidimensional utilization functions were used for niche metrics. During summer foraging overlaps were invariably high, but in other seasons periodically lower. Foraging site breadth was lower in winter, when fewer sites are profitable for foraging than in summer. Feeding posture versatility, by contrast, was highest in winter. Seasonal foraging shifts were very prominent, as great in fact as between-species differences. Often seasonal trends were parallel in different species. Niche axes of macrohabitat-type (e.g. tree) were more open for foraging variation and axes of microhabitat-type (tree part) more rigid. Among the resident species seasonal variation in foraging was greatest in Regulus regulus and Parus cristatus, whereas the foraging behaviour was more stable for P. montanus (an abundant species with broad niche), perhaps owing to greater intraspecific competition. In these northern forests foliage-gleaners must be versatile generalists to cope with the unpredictable resources, and thus they overlap broadly in their general resource niches which are determined by their genetically fixed cost and benefit relations to each resource type. Anyhow, presumably during periodical food shortage, the actual resource uses adjusted by resource availability and competition may overlap narrowly.     

Foraging Trade‐offs between Prey Size,Delivery Rate and Prey Type: How Does Niche Breadth and Early Learning of the Foraging Niche Affect Food Delivery?

Optimal foraging theory suggests that avian parents should prefer the most energetically efficient (largest) prey items when delivering food to offspring at a central place. However, during periods of high demand, selectivity of prey may decline, leading to the delivery of smaller and/or less nutritious items. We compared foraging trade‐offs between great tits (Parus major) which had a wider feeding niche than blue tits (Cyanistes caeruleus). We also compared the foraging efficiency of cross‐fostered young, which had learned the spatial foraging niche and prey size of the foreign species, to that of control conspecifics. Mean delivery rates did not differ between control and cross‐fostered parents of either species but as delivery rates increased, prey size declined for both species and both treatment groups. However, across the range of increasing delivery rates, parents were able to increase the total biomass of prey delivered. Cross‐fostering did not alter the proportion of different prey taxa in the diet, but cross‐fostered birds shifted the size of the prey taken to that of their foster species. Consistent with their broader feeding niche, great tits, but not blue tits, incorporated more unpalatable items (flies) as delivery rates increased. Although great tits foraged less efficiently in the blue tit niche, paradoxically, blue tits seem to deliver more prey biomass when foraging in the great tit niche.     

Phorid parasitoids affect foraging activity of Solenopsis richteri under different availability of food in Argentina

1. In Argentina, six species of Pseudacteon parasitoids (Phoridae) attack Solenopsis richteri, one of the two species of South American fire ant that are exotic pests in North America. 2. The presence of these Pseudacteon species significantly reduces the number of ants at food resources in the field, as well as foraging activity generally. 3. Some Pseudacteon not only attack ants walking on trails or at feeding sites, but also at mound entrances, inhibiting workers from leaving to forage. 4. The average size of foraging ants (which prescribes their suitability as hosts) decreased in the presence of phorids. 5. The number of attacking phorids was correlated positively with the number of ants walking towards the food on the trail before the attack. 6. Solenopsis richteri workers responded to manipulations of food size and presence or absence of parasitoids in a risk-adjusting way, i.e. although more foragers were recruited to larger food items, attacking phorids reduced ant foraging activity by the same factor regardless of the size of the food offered. 7. The data suggest that S. richteri colonies juggle the needs to harvest food efficiently, reduce competition, and avoid excess risks from parasitoids in complex ways.     

地标对犬蝠空间记忆的影响

为了研究地标（landmarks）是否影响犬蝠（Cynopterus sphinx）的空间记忆,我们通过室内模拟试验研究犬蝠和地标在觅食过程中空间记忆形成的关系。实验组按照每天地标数分别为0、2、4、8、0的数目连续进行5天实验,对照组不设地标进行相同条件的实验。结果显示,两组犬蝠第一次取食所用的时间与实验天数之间极显著相关（Pearson Correlations: 实验组r=-0.593, P<0.01;对照组r=-0.581, P<0.01）;实验组取食成功率与实验天数之间无明显相关性（Pearson Correlations: r=0.177, P>0.05）;对照组取食成功率与实验天数之间显著相关（Pearson Correlations: r=0.445, P<0.05）。实验组与对照组犬蝠第一次取食的时间差异不显著（GLM: F_0.05,1=4.703, P>0.05）,两组间取食的成功率差异也不显著（GLM: F_0.05,1=0.849, P>0.05）。这些结果说明了随着时间增加,犬蝠对取食地的空间记忆逐渐形成,放置地标在犬蝠对取食地空间记忆形成的过程中无显著影响。     

In situ feeding tactics of short-nosed fruit bat (Cynopterus sphinx) on mango fruits: evidence of extractive foraging in a flying mammal

We report a sequence of behaviors exhibited by the short-nosed fruit bat Cynopterus sphinx while feeding on fruits of Mangifera indica. They peel off the outer skin to form a feeding area of about 3–6 cm diameter. Such food preparatory behaviors were more pronounced on larger mangoes. Bats competed among themselves to feed on the mangoes that had such feeding areas exposed. Individuals that spent a considerable amount of time on food preparatory behaviors actively secured the fruits. Altogether, these behaviors indicate that Cynopterus bats might have learnt, over evolutionary time, and developed behaviors that facilitate efficient processing and feeding of fruits such as mangoes. It appears that actions exhibited by C. sphinx in peeling off the outer skin of mangoes exemplify “extractive foraging”, a behavior that is prominently known in large-brained mammals. Thus, our findings will have implications on the distribution and evolution of extractive foraging and “technical intelligence” among mammalian lineages.     

What,where and when: spatial foraging decisions in primates

When exploiting the environment, animals have to discriminate, track, and integrate salient spatial cues to navigate and identify goal sites. Actually, they have to know what can be found (e.g. what fruit), where (e.g. on which tree) and when (in what season or moment of the year). This is very relevant for primate species as they often live in seasonal and relatively unpredictable environments such as tropical forests. Here, we review and compare different approaches used to investigate primate spatial foraging strategies: from direct observations of wild primates to predictions from statistical simulations, including experimental approaches on both captive and wild primates, and experiments in captivity using virtual reality technology. Within this framework, most of these studies converge to show that many primate species can (i) remember the location of most of food resources well, and (ii) often seem to have a goal‐oriented path towards spatially permanent resources. Overall, primates likely use mental maps to plan different foraging strategies to enhance their fitness. The majority of studies suggest that they may organise spatial information on food resources into topological maps: they use landmarks to navigate and encode local spatial information with regard to direction and distance. Even though these studies were able to show that primates can remember food quality (what) and its location (where), still very little is known on how they incorporate the temporal knowledge of available food (when). Future studies should attempt to increase our understanding of the potential of primates to learn temporal patterns and how both socio‐ecological differences among species and their cognitive abilities influence such behavioural strategies.     

Advantages of social foraging in crab spiders: Groups capture more and larger prey despite the absence of a web

Among group‐living spiders, subsocial representatives in the family of crab spiders (Thomisidae) are a special case, as they build protective communal leaf nests instead of extensive communal capture webs. It could thus be inferred that antipredator benefits (e.g., enhanced protection in larger nests) rather than foraging‐related advantages (e.g., capture of more and larger prey) promote sociality in this family. Nonetheless, subsocial crab spiders do share prey, and if this behaviour does not reflect mere food scramble but has a cooperative character, crab spiders may offer insights into the evolution of social foraging applicable to many other cooperative predators that hunt without traps. Here, we performed a comparative laboratory feeding experiment on three of the four subsocial crab spider species—Australomisidia ergandros, Australomisidia socialis and Xysticus bimaculatus—to determine if crab spiders derive advantages from foraging in groups. In particular, we tested artificially composed groups of five sibling spiderlings vs. single siblings in terms of prey capture success and prey size preference. Across species, groups had higher prey capture success (measured in terms of capture rates and capture latency) and were more likely to attack large, sharable prey—dynamics leading to reduced food competition among group members in favour of living and foraging in groups. Within groups, we further compared prey extraction efficiency among the three applied social foraging tactics: producing, scrounging and feeding alone. In A. ergandros, individuals were exceptionally efficient when using the non‐cooperative scrounger tactic, which entails feeding on the prey provided by others. Thus, our multispecies comparison confirms foraging advantages in maintaining a cooperative lifestyle for crab spiders, but also demonstrates the relevance of research into exploitation of cooperative foraging in this family.     

Taxonomic status of the Forest Buzzard Buteo oreophilus trizonatus

The foraging efficiencies of four sympatric southern African seed-eating birds, namely Bronze Mannikin Spermestes cucullatus, Cape Sparrow Passer melanurus, Southern Red Bishop Euplectes orix and Thick-billed Weaver Amblyospiza albifrons, and a domesticated species, the Bengalese Finch Lonchura domestica, were measured and compared using giving-up densities (the amount of food remaining following patch exploitation) in experimental food patches. Foraging efficiency was quantified using giving-up densities by offering individual birds equal foraging opportunities. A low giving-up density displays the ability of a forager to profitably harvest food at low resource densities and to gainfully exploit the foraging opportunities overlooked by a less efficient forager. Ten individuals of each of the five species were allowed to forage on six different seed types. Thick-billed Weavers had significantly lower giving-up densities for all seed types except the smallest, namely red manna. Bronze Mannikins showed the converse trend, foraging most efficiently on the smallest seeds. The results of the present study revealed that Thick-billed Weavers were the most efficient foragers (i.e. had the lowest giving-up densities on seeds in feeding trays).     

Long-Term Habitat Use by Mountain Gorillas (Gorilla gorilla beringei). 2. Reuse of Foraging Areas in Relation to Resource Abundance, Quality, and Depletion

Resource depression caused by current feeding and the rate of resource renewal should influence foragers' decisions about when to revisit foraging areas. Adjustment of foraging paths and revisit rates should be particularly important when resources renew slowly. Foragers can also benefit by returning more often to highly profitable than to less profitable foraging areas. Many highly frugivorous primates seem to time revisits to fruit sources so as to harvest fruit efficiently and, also, use efficient search paths. Fewer data on non-frugivores exist. Mountain gorillas are folivores that eat mostly perennially available, continuously growing herbs and vines. Vegetation regenerates slowly from the effects of gorilla trampling, though trampling can also facilitate food species productivity, at least in the short term. Adjustment of intervals between visits to foraging areas to the extent of previous use and to resource renewal rates should increase gorilla foraging efficiency. Long-term data on habitat use by 6 mountain gorilla social units show that revisit intervals vary in association with variation in the extent of previous use and in plant productivity. However, they also revisit areas more often, the higher the biomass and nutritional quality of food there. These data are generally consistent with the hypothesis that the gorillas crop resources on a sustained-yield basis, though more precise data on areal revisits and complementary long-term data on vegetation composition would be needed to test the hypothesis.