A New Report of Chimpanzee Ant-fishing from the Issa Valley, Tanzania

Tool use in chimpanzees (Pan troglodytes) is widespread across their geographical distribution, having been documented in all populations studied to date. Ant-fishing, specifically, is less frequently observed, reported so far in only ten different communities. We describe the first observations of ant-fishing of Camponotus chrysurus by chimpanzees living in the mosaic landscape of the Issa Valley, western Tanzania. After two separate bouts, both occurring in the same position in a fig tree (Ficus lutea vahl), we recovered five ant-fishing tools made from the liana Dichapetalum crassifolium chodat. Tool types closely resemble those described for earlier reports of the same behavior in near-by Mahale Mountains chimpanzees, and thus may have implications for cultural diffusion of the habit across populations

Savanna chimpanzees adjust sleeping nest architecture in response to local weather conditions

Objectives Great ape nests are hypothesized to aid safe, secure sleep via providing thermoregulation or protection from predators and vectors. We aimed to describe and investigate variation in chimpanzee nest architecture across two populations in response to local weather conditions. Materials and methods We experimentally tested whether nests provide insulation by measuring heat loss within and outside nests, and took detailed measurements of the number, size, and type of materials used in nest building across two dry-habitat research sites (Fongoli, Senegal, and Issa, Tanzania). We tested application of principal components analysis (PCA) to extract composite quantitative measures of the key components of shape and architecture, before testing how PCs vary across populations with overnight weather conditions that reflect hypothesized thermoregulatory function. Results Heat loss is greater and occurs faster outside of nests. PCA allowed meaningful comparison of nests within and between sites. Nest variation at both sites revealed chimpanzees built thicker nests in cooler conditions and used more broken branches and support in moister conditions. Chimpanzees in Fongoli used more lining and mattress material in colder conditions, whilst in Issa nest depth and support branch size were larger in windier conditions. Discussion Shape and architectural measures reflected insulation and stability of nest structure. Chimpanzees in Fongoli and Issa may achieve the same functional goals by adjusting nest shape and architecture in different ways. These results suggest that wild chimpanzees show flexible building techniques in response to local, overnight weather conditions in making an insulating and stable, supportive platform for sleep

Passive acoustic monitoring reveals group ranging and territory use: a case study of wild chimpanzees (Pan troglodytes)

Background: Assessing the range and territories of wild mammals traditionally requires years of data collection and often involves directly following individuals or using tracking devices. Indirect and non-invasive methods of monitoring wildlife have therefore emerged as attractive alternatives due to their ability to collect data at large spatiotemporal scales using standardized remote sensing technologies. Here, we investigate the use of two novel passive acoustic monitoring (PAM) systems used to capture long-distance sounds produced by the same species, wild chimpanzees (Pan troglodytes), living in two different habitats: forest (Taï, Côte d’Ivoire) and savanna-woodland (Issa valley, Tanzania). Results: Using data collected independently at two field sites, we show that detections of chimpanzee sounds on autonomous recording devices were predicted by direct and indirect indices of chimpanzee presence. At Taï, the number of chimpanzee buttress drums detected on recording devices was positively influenced by the number of hours chimpanzees were seen ranging within a 1 km radius of a device. We observed a similar but weaker relationship within a 500 m radius. At Issa, the number of indirect chimpanzee observations positively predicted detections of chimpanzee loud calls on a recording device within a 500 m but not a 1 km radius. Moreover, using just seven months of PAM data, we could locate two known chimpanzee communities in Taï and observed monthly spatial variation in the center of activity for each group. Conclusions: Our work shows PAM is a promising new tool for gathering information about the ranging behavior and habitat use of chimpanzees and can be easily adopted for other large territorial mammals, provided they produce long-distance acoustic signals that can be captured by autonomous recording devices (e.g., lions and wolves). With this study we hope to promote more interdisciplinary research in PAM to help overcome its challenges, particularly in data processing, to improve its wider application

The importance of nutrient hotspots for grazing ungulates in a Miombo ecosystem, Tanzania

While movement patterns of grazing ungulates are strongly dependent on forage quality their use of nutrient hotspots such as termite mounds or grazing lawns has rarely been quantified, especially in savanna ecosystems where soil-nutrient quality is low. Additionally, few experiments have been conducted to determine the role of termite mound- and grazing lawn-derived soils in improving forage quality in the field. We studied wild ungulate grazing activities around ten termite mounds, six grazing lawns and their respective control sites in a Miombo system of Issa Valley, western Tanzania, in the same system. We used indirect observations (i.e., dung, tracks) to identify seasonal and spatial variations in habitat use of various wild mammalian grazers. Grazer visitation rates were nine and three times higher on termite mounds and grazing lawns, respectively, compared to control sites. During the rainy season, termite mounds were more frequently used than grazing lawns while the latter were used more often during the dry season. In an additional pot experiment with soils derived from different areas, we found that Cynodon dactylon in termite mound-derived soils had twice as high Nitrogen and Phosphorous contents and biomass compared to grasses planted in grazing lawn soils and control site soils. We highlight that both termite mounds and grazing lawns play a significant role in influencing seasonal nutrient dynamics, forage nutrient quality, habitat selectivity, and, hence, grazing activities and movement patterns of wild ungulate grazers in savannas. We conclude that termite mounds and grazing lawns are important for habitat heterogeneity in otherwise nutrient–poor savanna systems

Anthropogenic disturbance and chimpanzee (Pan troglodytes) habitat use in the Masito-Ugalla Ecosystem, Tanzania

The habitat quality of chimpanzee (Pan troglodytes), including the availability of plant food and nesting species, is important to ensure the long-term survival of this endangered species. Botanical composition of vegetation is spatially variable and depends on soil characteristics, weather, topography, and numerous other biotic and abiotic factors. There are few data regarding the availability of chimpanzee plant food and nesting species in the Masito-Ugalla Ecosystem (MUE), a vast area that lies outside national park boundaries in Tanzania, and how the availability of these resources varies with human disturbance. We hypothesized that chimpanzee plant food species richness, diversity, and abundance decline with increasing human disturbance. Further, we predicted that chimpanzee abundance and habitat use is influenced negatively by human disturbance. Published literature from Issa Valley, Gombe, and Mahale Mountains National Parks, in Tanzania, was used to document plant species consumed by chimpanzees, and quantify their richness, diversity, and abundance, along 32 transects totaling 63.8 km in length across four sites of varying human disturbance in MUE. We documented 102 chimpanzee plant food species and found a significant differences in their species richness (H = 55.09, P 0.964). The least disturbed site exhibited the highest encounter rate of chimpanzee nests/km, with rates declining toward the highly disturbed sites. Our results show that severe anthropogenic disturbance in MUE is associated with the loss of chimpanzee plant food species and negatively influences chimpanzee habitat use, a relationship that threatens the future of all chimpanzee populations outside national parks

Vocal communication in wild chimpanzees: a call rate study

BACKGROUND: Patterns of vocal communication have implications for species conservation: a change in calling behaviour can, for instance, reflect a disturbed habitat. More importantly, call rate is a parameter that allows conservation planners to convert call density into animal density, when detecting calls with a passive acoustic monitoring system (PAM). METHODS: We investigated chimpanzee (Pan troglodytes schweinfurthii) call rate during the late dry season in the Issa Valley, western Tanzania by conducting focal follows. We examined the socio-ecological factors that influence call production rate of savanna woodland chimpanzees. RESULTS: We found that sex, proportion of time spent in a vegetation type, proportion of time spent travelling, time of the day, party size and swollen parous female presence had a significant effect on the call rate. Call rate differed among the different demographic classes with subadult and adult males vocalising twice as often as the subadult and adult females and three times as often as the juveniles. APPLICATIONS: The use of PAM and recent statistical developments to estimate animal density is promising but relies on our knowing individual call rate, often not available for many species. With the improvement in automatic call detection, we anticipate that PAM will increasingly be broadly applied to primates but also across taxa, for conservation

Observation of an Encounter between African Wild Dogs (Lycaon pictus) and a Chimpanzee (Pan troglodytes schweinfurthii) in the Issa Valley, Tanzania

There has been considerable discussion of chimpanzees (Pan troglodytes) as predators, most commonly of red colobus monkeys (Procolobus spp.). Far more infrequent are published descriptions of chimpanzees as prey. The paucity of direct observations of chimpanzee-predator encounters is an obstacle in situating chimpanzees in both predator and prey roles. For the first time, we describe an observation of an encounter between African wild dogs (Lycaon pictus) and a chimpanzee in the Issa Valley, Tanzania, one of the driest and most open chimpanzee habitats. Whilst the initiation of the encounter was missed, here we nonetheless interpret the data that we did record. Our observations of behavior in both parties suggest the possibility of an investigatory rather than predatory encounter on the part of the wild dogs

Deterring poaching in western Tanzania: The presence of wildlife researchers

Illegal poaching threatens wildlife across Africa. Historically and even today, conservationists have lobbied local and national governments to create and better manage protected lands to reduce this threat. In many cases, however, governments are either unable or unwilling to invest further resources in exclusive protected areas, such as national parks. In addition to traditional methods, or where such approaches are not feasible, a complimentary form of protection is researcher presence, which has been described recently to deter wildlife poaching. We present data over four years that assesses the impact of researcher presence on wildlife and snare encounter rate in an unprotected area in western Tanzania, where there is a mid-term chimpanzee study ongoing. We systematically collected spatiotemporal presence data on the nine, most common mammal species in the study area, as well as all snares. Snare encounter rates increased with distance from researcher base station, whilst overall mammal encounter rates decreased. Further, mammal encounter rates have increased each year since the arrival and permanence of researchers in this remote area. Our findings have implications for the benefits of researcher presence, namely in deterring poaching, especially in unprotected areas with minimal governmental surveillance

Leopard (Panthera pardus) predation on a red-tailed monkey (Cercopithecus ascanius) in the Issa Valley, western Tanzania.

Predation is predicted to be an important selection pressure for primates. Evidence for this hypothesis is rare, however, due to the scarcity of direct observations of primate predation. We describe an observation of leopard (Panthera pardus) predation on a red-tailed monkey (Cercopithecus ascanius schmidti) at the Issa Valley, a savanna-woodland mosaic landscape in western Tanzania. We compare rates of evidence of leopard presence between Issa and other primate study sites in sub-Saharan Africa. An increase in direct observations of leopards at Issa in recent years suggests that leopards may be habituating to researcher presence