Night Nests Research Articles

Habitual ground nesting in the Bugoma Forest chimpanzees (Pan troglodytes schweinfurthii), Uganda.

We report the presence of habitual ground nesting in a newly studied East African chimpanzee (Pan troglodytes schweinfurthii) population in the Bugoma Central Forest Reserve, Uganda. Across a 2-year period, we encountered 891 night nests, 189 of which were classified as ground nests, a rate of ~21%. We find no preliminary evidence of socio-ecological factors that would promote its use and highlight local factors, such as high incidence of forest disturbance due to poaching and logging, which appear to make its use disadvantageous. While further study is required to establish whether this behavior meets the strict criteria for nonhuman animal culture, we support the argument that the wider use of population and group-specific behavioral repertoires in flagship species, such as chimpanzees, offers a tool to promote the urgent conservation action needed to protect threatened ecosystems, including the Bugoma forest.

Decay rates of arboreal and terrestrial nests of Easternchimpanzees (Pan troglodytes schweinfurthii) in the Bugoma Central Forest Reserve, Uganda: Implications for population size estimates.

Chimpanzees were once thought to sleep primarily in the trees, but recent studies indicate that some populations also construct terrestrial night nests. This behavior has relevance not only to understanding the behavioral diversity of Pan troglodytes, but also to the conservation of the species, given that nest encounter rates are often used to estimate great ape population densities. A proper estimate of decay rates for ground nests is necessary for converting the encounter rate of nests to the density of weaned chimpanzees. Here we present the results of the first systematic comparative study between the decay rates of arboreal and terrestrial chimpanzee nests, from the Bugoma Central Forest Reserve in western Uganda. We followed the decay of 56 ground and 51 tree nests in eight nest groups between April 2020 and October 2021. For 15 of the ground and 19 of the tree nests, we collected detailed information on the condition of the nests every two weeks; we checked the remaining 73 nests only twice. On average, ground nests lasted 238days versus 276 days for tree nests (p = 0.05). Of the 107 total nests surveyed, 51% of tree and 64% of ground nests had disappeared after six months. Based on our results, we propose a modification of the formula used to convert nest density into chimpanzee density. Our results highlight the importance of taking into account potential differences in decay rates between ground versus tree nests, which will likely influence our understanding of the distribution of ground nesting behavior in chimpanzee across tropical Africa, as well as our estimations of the densities of ground nesting populations.

NESTING BEHAVIORAL ADAPTATIONS OF ORANGUTAN (PONGO PYGMAEUS MORIO) IN COAL MINING AREA IN EAST KALIMANTAN

Coal mining changed forest structure and composition, it caused large negative impacts on the orangutan. In order to mitigate those negative effects, it is crucial to understand their nesting behavior adaptation in mining area. We investigated 74 times nested event in coal mining rehabilition area (CMRA) in East Kutai and 123 times in the Kutai National Park (Prevab) from October 2013 to September 2014 and include only night nests. We compared both habitats. Orangutans in CMRA built the nest later than in Prevab and used 15 species of trees as nests sites intensively on Senna siamea and Gmelina arborea. In Prevab, 35 species with the higher frequencies on Eusideroxylon zwageri and Dracontomelon dao. The average diameter of nest trees in CMRA smaller than Prevab. The height of nest trees in CMRA with the highest frequency was in 10.1-15 m, while in Prevab was as in 20.1-25 m. Orangutans in CMRA nested at the height of <15 m, lower than in Prevab was >20 m. Reused nest in CMRA was higher than in Prevab. Orangutans in CMRA more often built nests at the peak and limb, while in Prevab at the limb and peak. Orangutans in CMRA had learned to utilize various species and dimensions of trees as the place to build nests.

Population history of chimpanzees introduced to Lake Victoria’s Rubondo Island

Between 1966 to 1969, Bernhard Grzimek (Frankfurt Zoological Society, FZS) introduced chimpanzees (Pan troglodytes) previously held in European institutions to Rubondo Island in Lake Victoria in Tanzania. Earlier publications report various numbers of released animals and that all founders originated from West Africa. We revise these assumptions through consultation of archived FZS records and genetic analyses of surviving descendants. Accordingly, 17 chimpanzees were transported to Africa in four waves, with male-female ratios of 3:8, 1:0, 1:0 and 2:2; one female died in transit. Thus, 16 chimpanzees were released in total. FZS and studbook records allocate a West African provenance to only 19% of the founders and a generic "Africa" origin to 56%. Still, studbook records render it unlikely that any of the founders were captive-born. In addition, our genetic analyses based on biological samples from the current descendants trace the geographical origin of their ancestors back to West Africa (P. t. verus) and Central Africa (P. t. troglodytes). Based on counts of individuals and night nests, we estimate that the population, since 1969, grew to around 35 individuals in 2014 (annual increase 3.3%). Thus, chimpanzees released onto a large forested island free from predators or hunting pressure, habitat destruction and conspecific competition can form a self-sustaining island population without human support.

Nesting behavior of reintroduced Bornean Orangutan in Bukit Batikap Conservation Forest, Central Kalimantan, Indonesia

Abstract. Nayasilana IN, Atmoko SS, Suyoko A, Hadisusanto S. 2020. Nesting behavior of reintroduced Bornean Orangutan in Bukit Batikap Conservation Forest, Central Kalimantan, Indonesia. Biodiversitas 21: 2088-2096. Great apes such as orangutans build a nest to rest in every night. Orangutan’s nest making skills correlate with their adaptability in a new habitat. Here we analyzed the nest skill on the reintroduced orangutan. Skills process and thought training there is a back to remembers in forest school and pre-release islands in the rehabilitation center. The study aimed to observe the skill adaptation of reintroduced orangutans (semi-wild and ex-rehabilitate) for nest building and the characteristic of the tree chosen for their nests in a new habitat. The study was 16 individuals (8 semi-wild and 8 ex-rehabilitate) from February 2012 to November 2014 at the release site of Bukit Batikap Conservation Forest, Central Kalimantan. The method used in the study was instantaneous focal animal sampling, which follows the behavior of each orangutan from the morning nest to the night nest. Non-parametric statistics test (Kruskal-Wallis) was used to nesting behavior, Canonical Correspondence Analysis (CCA) is used to determine the relationship between nesting behavior and nesting tree species, and ArcMap GIS 10.3 to find out the distribution of nest trees in the research location. The result of the study revealed that reintroduced orangutan prefers to build a nest to rest at night rather than day nest. Semi-wild orangutans prefer tree species with dense canopy and branching, while ex-rehabilitation orangutans pay less attention to this. Mostly, reintroduced Bornean orangutan created new nests rather than reusing and/or repairing old nests. Species of Syzygium sp. Lithocarpus sp. and Xanthophyllum sp. are a preferred species of the nest tree, the nest position of 2 (nests are constructed on the main side-branch) and 3 (the crown of the tree) is dominance. Orangutan prefer height tree species between 26-30m for day nests, are selectively determined as part of the adaptation process. However, each individual will choose the nest type species of tree, positions, and height according to their characteristics of the nest tree.

How to measure chimpanzee party size? A methodological comparison.

Chimpanzees (Pan troglodytes) live in fission-fusion societies where community members form temporary parties that frequently change in size and composition. Chimpanzee party size and composition have been widely studied to identify proximate causes of grouping patterns, and party size estimates are used to assess population sizes and densities. Numerous socio-ecological factors influence chimpanzee party size, but findings differ across studies. Various methods to measure party size exist, including direct observations, motion-triggered camera (MTC) observations, and nest counts. However, comparative analyses of these methods are lacking. Here, we assess relative differences in four commonly used party size methods and we examine socio-ecological factors influencing party size of unhabituated chimpanzees (P. t. verus) at Seringbara, Nimba, Guinea. We also assess which method(s) best reflect the influence of socio-ecological factors on party size. Using data collected over 69months, we show that night nest counts resulted in relatively larger party size estimates than the other methods, and day nest counts resulted in relatively smaller party size estimates. Direct and MTC observations did not differ in relative estimates of party size and composition. Both fruit abundance and presence of estrous females positively influenced party size, but this effect was only evident when measuring party size with MTCs. Methods thus differ in relative party size estimates and their ability to assess the impact of socio-ecological factors. We conclude that MTC observations best represent party size and the effect of socio-ecological factors at Nimba. MTCs show promising potential for studying grouping patterns in unhabituated chimpanzees.

Impacts of Selective Logging and Associated Anthropogenic Disturbance on Intact Forest Landscapes and Apes of Northern Congo

The tropical forests of Western Equatorial Africa are home to extraordinary biodiversity, including sympatric chimpanzees (Pan troglodytes troglodytes) and western lowland gorillas (Gorilla gorilla gorilla). The region is also comprised of significant stands of Intact Forest Landscapes (IFL) that are in rapid decline. As part of a regional monitoring effort, we partnered with local government officials, conservation NGOs, and the timber company working in the region to assess ape abundances in relation to habitat characteristics and anthropogenic disturbances and compare IFL and non-IFL areas in the Sangha Trinational landscape, Republic of Congo. We found that chimpanzees and gorillas occur at high densities in IFL, as well as non-IFL. To better understand how selective logging changes floristic factors, we compared herb and tree densities from botanical surveys conducted in IFL and non-IFL. IFL had higher tree stem densities and less terrestrial ground herbs than logged habitats. However, few ape resources were logged in this extraction cycle and areas with tree stems removed had higher abundances of ape preferred terrestrial herbs, which may contribute to the elevated ape abundance estimates. Floristic differences in logged forest were however identified to coincide with differences in ape resource use. The chimpanzee tree nesting niche was reduced in non-IFL as night nests were constructed significantly closer to the ground than in IFL. Whereas gorilla nest height locations did not differ significantly between IFL and non-IFL. To identify other potential anthropogenic impacts, we assessed direct and indirect impacts of road expansion and illegal hunting on wildlife in these remote areas. Increased access to IFL that facilitates illegal hunting raises concern for protecting wildlife across Western Equatorial Africa. We urge that the results of biodiversity assessments and strategic aspects of long-term protection should be taken into account when identifying conservation set-asides and maintaining diverse states of modified forests. Finally, the results of our monitoring efforts are provided as evidence of the value of long-term collaborations among local stakeholders, government officials, conservation agencies, and industrial partners to improve the implementation of certification standards and biodiversity conservation initiatives.

Nest height is affected by lamppost lighting proximity in addition to nestbox size in urban great tits

Both natural and artificial light have proximate influences on many aspects of avian biology, physiology and behaviour. To date artificial light at night is mostly considered as being a nuisance disrupting for instance sleep and reproduction of diurnal species. Here, we investigate if lamppost night lighting affects cavity‐nesting bird species inside their breeding cavity. Nest height in secondary cavity‐nesting species is the result of trade‐offs between several selective forces. Predation is the prevailing force leading birds to build thin nests to increase the distance towards the entrance hole. A thin nest may also limit artificial light exposure at night. Yet, a minimum level of daylight inside nesting cavities is necessary for adequate visual communication and/or offspring development. Against this background, we hypothesised that avian nest‐building behaviour varies in response to a change in night lighting. We monitored nest height of urban great tits Parus major during six years and found that it varied with artificial light proximity. The birds built thinner nests inside nestboxes of various sizes in response to increasing lamppost night light availability at the nest. In large nestboxes, the nests were also thinner when a lamppost was present in the territory. Whether this relationship between artificial night lighting and nest height reflects a positive or negative effect of urbanisation is discussed in the light of recent experimental studies conducted in rural populations by other research groups.

Nest location preferences in zoo-housed orangutans

Nest building is an advanced and complex activity that wild orangutans engage in, yet they do so on a daily basis and with potential safety consequences. Like their wild counterparts, zoo-housed orangutans also make nests when given adequate materials, yet comparatively little research has documented the nesting habits of captive orangutans, including potential social and environmental influences of nest site selections. We documented the night nesting behavior of six adult orangutans housed at the Smithsonian's National Zoological Park (NZP), identifying preferred nest locations and proximity to conspecifics, comparing observed patterns to those reported in a nest behavior survey of orangutan facilities throughout the Association of Zoos and Aquariums (AZA). Survey results reveal that in addition to several universal patterns of nesting behaviors, as in the wild, the sharing of night nests by captive adult orangutans occurs only rarely (2 of 31 surveyed facilities). Data collected at NZP indicate that night nearest neighbor associations among nesting conspecifics may be a useful proxy for actual nearest neighbor data taken during daytime social interactions and may offer a more feasible alternative for determining social relationships among large groups of socially housed orangutans.

Environmental variables across Pan troglodytes study sites correspond with the carbon, but not the nitrogen, stable isotope ratios of chimpanzee hair.

Diet influences the stable isotope ratios of carbon and nitrogen (δ(13) C and δ(15) N values) in animal tissue; but here we explore the influences of particular aspects of the local environment on those values in chimpanzees (Pan troglodytes). In this article we present new δ(13) C and δ(15) N values in Gombe chimpanzees using hairs collected from night nests in 1989. Then, we explore the influence of environmental factors by comparing our Gombe data to those from eight additional Pan study sites with previously published stable isotope data. We compare chimpanzee δ(13) Chair and δ(15) Nhar values to specific characteristics of local site ecology (biome and ecoregion) and to local Mean Annual Precipitation (MAP) to test hypotheses based on known effects of these variables on the δ(13) C and δ(15) N values in plant tissues. The comparison shows that hair from chimpanzees living in savanna sites with lower MAP have higher δ(13) Chair values than do chimpanzees living in woodland and forested sites with higher MAP. These results demonstrate the potential of using δ(13) C values in primate tissue to indicate aspects of their local ecology in cases where the ecology is uncertain, such as samples collected early in the last century and in fossil hominins. In contrast to expectations, however, chimpanzee δ(15) Nhair values from some savanna sites with lower MAP are lower, not higher, than those living in more forested areas with higher MAP. It is likely that diet selectivity by chimpanzees affects δ(15) Nhair values to a greater extent than does the influence of precipitation on plants. Am. J. Primatol. 78:1055-1069, 2016. © 2015 Wiley Periodicals, Inc.

Wild orangutan males plan and communicate their travel direction one day in advance.

The ability to plan for the future beyond immediate needs would be adaptive to many animal species, but is widely thought to be uniquely human. Although studies in captivity have shown that great apes are capable of planning for future needs, it is unknown whether and how they use this ability in the wild. Flanged male Sumatran orangutans (Pongo abelii) emit long calls, which females use to maintain earshot associations with them. We tested whether long calls serve to communicate a male's ever-changing predominant travel direction to facilitate maintaining these associations. We found that the direction in which a flanged male emits his long calls predicts his subsequent travel direction for many hours, and that a new call indicates a change in his main travel direction. Long calls given at or near the night nest indicate travel direction better than random until late afternoon on the next day. These results show that male orangutans make their travel plans well in advance and announce them to conspecifics. We suggest that such a planning ability is likely to be adaptive for great apes, as well as in other taxa.

Ground Night Nesting in Chimpanzees: New Insights from Central Chimpanzees (Pan troglodytes troglodytes) in South-East Cameroon

Some chimpanzee populations exhibit ground night nesting, which occurs in different habitat types, is driven by a variety of interconnected factors, and may reflect cultural or social differences. This has important implications for ape conservation management, given that accurate nest builder identification is required to estimate density, crucial in monitoring, and allows inferences about environmental and social factors that may have contributed to the transition from tree to ground sleeping in early hominins. We conducted a 24-month marked nest count survey in La Belgique, Cameroon, and recorded the occurrence of chimpanzee tree and ground night nests, temperature and rainfall, predator and large mammal abundance, human activities, nesting tree species, and Uapaca spp. consumption. Ground night nesting occurred at a rate of 3.47% (n = 1,008), with more in swamps, in the dry season and with increasing human activities. We found no influence of leopard/elephant presence, but a possible influence of lack of nesting trees. We suggest chimpanzees visit swamps in the dry season (low water levels) for relief from hunting pressure and to consume Uapaca spp. fruits. Ground nesting may be enabled due to high abundance of terrestrial herbaceous vegetation, and may be favoured for inconspicuousness and safety from gun hunters.

Effects of Human Presence on Chimpanzee Nest Location in the Lebialem-Mone Forest Landscape, Southwest Region, Cameroon

In several areas of Africa, great apes experience increasing predation pressure as a result of human activities. In this study, terrestrial and arboreal nest construction among chimpanzee (Pan troglodytes ellioti) populations was investigated in the Lebialem-Mone Forest Landscape (LMFL), Southwest Region, Cameroon, to examine the anthropogenic effects on nest location. Data on the height, distribution and approximate age of chimpanzee night nests were collected during two 4-week primate field surveys (July to August 2010; July 2011) at two field sites (Bechati and Andu) within the LMFL. Data were collected using the line transect method. Chimpanzee night nests were categorized by their location: arboreal versus terrestrial. During the two field surveys, arboreal night nests were the most frequently constructed nest type at both sites, and the only type of night nest constructed at Bechati. Terrestrial night nests were also constructed at Andu. The main difference between these two sites is the level of human predation and agricultural development. At Bechati chimpanzees inhabit forest regions around dense, expanding villages and are regularly hunted by humans. However, at Andu the chimpanzee populations are not under the same threat. Therefore, terrestrial night nest construction in the LMFL appears to be a behavior exhibited where there is less human presence.

Pan thanatology

Chimpanzees' immediate responses to the death of a group-member have rarely been described. Exceptions include maternal care towards dead infants, and frenzied excitement and alarm following the sudden, traumatic deaths of older individuals [1-5]. Some wild chimpanzees die in their night nest [6], but the immediate effect this has on others is totally unknown. Here, with supporting video material, we describe the peaceful demise of an elderly female in the midst of her group. Group responses include pre-death care of the female, close inspection and testing for signs of life at the moment of death, male aggression towards the corpse, all-night attendance by the deceased's adult daughter, cleaning the corpse, and later avoidance of the place where death occurred. Without death-related symbols or rituals, chimpanzees show several behaviours that recall human responses to the death of a close relative.

Modelling ranging behaviour of female orang-utans: a case study in Tuanan, Central Kalimantan, Indonesia

Quantification of the spatial needs of individuals and populations is vitally important for management and conservation. Geographic information systems (GIS) have recently become important analytical tools in wildlife biology, improving our ability to understand animal movement patterns, especially when very large data sets are collected. This study aims at combining the field of GIS with primatology to model and analyse space-use patterns of wild orang-utans. Home ranges of female orang-utans in the Tuanan Mawas forest reserve in Central Kalimantan, Indonesia were modelled with kernel density estimation methods. Kernel results were compared with minimum convex polygon estimates, and were found to perform better, because they were less sensitive to sample size and produced more reliable estimates. Furthermore, daily travel paths were calculated from 970 complete follow days. Annual ranges for the resident females were approximately 200 ha and remained stable over several years; total home range size was estimated to be 275 ha. On average, each female shared a third of her home range with each neighbouring female. Orang-utan females in Tuanan built their night nest on average 414 m away from the morning nest, whereas average daily travel path length was 777 m. A significant effect of fruit availability on day path length was found. Sexually active females covered longer distances per day and may also temporarily expand their ranges.

Orangutans

Orangutans

Nesting Behavior of Gorilla gorilla diehli at Kagwene Mountain, Cameroon: Implications for Assessing Group Size and Density

We recorded nesting data at 569 fresh night nest sites, comprising 7032 individual nests, of Cross River gorillas inhabiting the Kagwene Mountain in western Cameroon. The mean night nest group size was 12.4. Overall, 55% of night nests were constructed on the ground and 45% in trees. Significantly more arboreal nests were constructed in the wet season (69%), vs. the dry season (19%). Day nest construction was common at Kagwene (n = 260 nest sites, mean nest group size = 5.98) and we encountered significantly more day nest sites in the wet season. Nest site reuse was also common (35%), though not related to season. Our results of nesting habits concur with those from other western gorilla studies, in which rainfall influences arboreal nesting. However, we encountered wet season arboreal nesting, day nest construction, and overall nest site reuse more frequently than reported for other sites. Our observations have considerable implications when estimating group size and density using traditional nest count data. The gorillas at Kagwene inhabit the highest altitudinal range of all Cross River gorilla subpopulations and rainfall is also high; therefore other subpopulations may demonstrate different nesting characteristics. However, one should consider our findings when attempting to estimate Cross River gorilla density at other localities through nest site data.

Plant choice in the construction of night nests by gorillas in the Bwindi Impenetrable National Park, Uganda

We investigated the choice of plants in nest sites and individual night nests of a group of gorillas (Gorilla beringei) in Bwindi Impenetrable National Park, Uganda. Most of the nests were built on the ground in secondary forest or canopy gaps. The gorillas used 62 plant genera in their nests out of a possible 108 plant genera available in the immediate environment. This group of Bwindi gorillas chose nest sites nonrandomly with respect to habitat type and selected nest sites in which Pteridium spp. or Mimulopsis spp. were the dominant plants. The Bwindi gorillas selected Pteridium spp. and Ipomea spp. to construct their individual night nests in greater quantities compared to their proportional availability in the immediate environment.

Inventory of large and medium-sized mammals in south-western Cameroon / Inventaire des mammifères de moyenne et de grande taille dans le sud-ouest Cameroun

The results of an inventory of large and medium-sized mammals in the Campo and Ma'an Forests in southwestern Cameroon are presented. In 24 months between 1997 and 2000, observations of live animals, tracks, faeces and night nests of apes were recorded on a total of 665.5 km of line transects. The presence of 33 species, including 12 diurnal and three nocturnal primate species, eight ungulates and five carnivores, was confirmed. Hunters confirmed the occurrence of 15 additional species. In the Campo Forest, the species diversity and density of most mammals were higher than in the Ma'an Forest, although a large part of the Campo Forest has been logged. Only three guenon species and chimpanzees were found at the same or even higher densities in the as yet unlogged Ma'an Forest. Gorillas, elephants, buffaloes and mangabeys were extremely rare in the Ma'an Forest. High hunting pressure in the Ma'an Forest seems to have led to a drastic population decline for most species. In the Campo Forest, mammal densities were lower in the northern and western parts of the area subjected to high levels of habitat destruction by logging and hunting than in the less exploited southern and eastern areas of the logging concession and within the National Park.

MINIREVIEW: The influences of animal diggings and runoff water on the vegetation in the Negev Desert of Israel

There is interaction between porcupines that create diggings and the vegetation in a desert biome. Dense patches of diggings may be found in large areas in the Negev and other deserts such as those of South Africa. Porcupines create diggings from 5 to 25 cm deep in the Negev in order to consume subterranean organs of about 18 species of geophytes and hemicryptophytes. There are two main strategies of consumption of these plants: (a), destruction by total consumption of only 20 to 25% of a patch of plants, which are then renewed from seeds; (b), partial consumption of almost all the plants in a patch so that parts of the plants remain below the bottom of the digging and later continue to grow there. In addition to porcupines, there are many other creatures in deserts, such as insects, reptiles, birds, rodents, gazelles, and ibex, that create diggings, depressions, or wallows in the soil for the consumption of subterranean parts of plants or as night beds or nests. In desert soils with low water infiltration, even a rainfall of about 7 mm may cause runoff water. In a 25-cm-deep depression the runoff equivalent to a 250-mm rainfall may accumulate, whereas only 2-4 mm may penetrate the soil in the area surrounding the digging. Diggings may act as wind traps for seeds and organic matter, and their accumulation, together with large amounts of runoff water, make them favorable microhabitats. Seeds of plant species that are consumed, as well as seeds of other species, germinate, and the plants develop in these diggings in large numbers. A succession of events relating to the emergence of annuals in the diggings occurs according to the percentage of filling-in of the digging by soil erosion. In the diggings there is a gradual increase in plant density, plant biomass, species diversity, and seed yield, up to 50% of filling-in. Then there is a gradual decrease of all these factors until the digging is 100% filled-in. During the filling-in process, plant species dominance changes from plant species with wind-dispersed seeds to those with rain-dispersed seeds.