Growth rates in the giant rosette plants Dendrosenecio adnivalis and Lobelia wollastonii on the Ruwenzori Mountains, Uganda

Stem lengths of Dendrosenecio adnivalis and Lobelia wollastonii were measured three times over 5.5 years in the Ruwenzori Mountains, Uganda. These are the only growth data for these two species. Both species had highly variable growth rates. Absolute growth rates in D. adnivalis were not related to the number of rosettes, inflorescences or initial height of plants. The D. adnivalis that were shorter at the beginning of the study grew proportionately faster than did taller individuals. Growth rate was positively associated with annual rainfall for D. adnivalis on the Ruwenzori Mountains, D. keniodendron on Mount Kenya, and D. battiscombei on the Aberdare Mountains. Lobelia wollastonii that were taller at the beginning of the study had greater absolute growth rates than did shorter plants. There was no significant relationship between the initial height and proportional increase in height for L. wollastonii. Growth rate and height are unreliable indicators of age for both species. Keywords: Dendrosenecio, Lobelia, growth rates, Ruwenzori Mountain

Two red-capped robin-chats Cossypha natalensis imitate antiphonal duet of black-faced rufous warblers Bathmocercus rufus

During my studies of primate behavioral ecology in the Kibale Forest, Uganda, I documented the first cases of red-capped robin-chats Cossypha natalensis imitating an antiphonal duet. In one case two individual robin chats imitated the entire duet of the black-faced rufous warbler Bathmocercus rufus, each giving both the male and female components. In a second case one robin chat gave the male components and another gave that of the female warbler. The lack of temporal separation between the male and female components of the warbler’s antiphonal duet indicates an unusually high level of auditory perception and response time and cognitive ability on the part of redcapped robin-chats.Keywords: auditory perception, response time, cognitive abilitie

Udzungwa Red Colobus Piliocolobus gordonorum Matschie 1900

No abstract available

Adolescent male chimpanzees (Pan troglodytes) form social bonds with their brothers and others during the transition to adulthood

Social relationships play an important role in animal behavior. Bonds with kin provide indirect fitness benefits, and those with nonkin may furnish direct benefits. Adult male chimpanzees (Pan troglodytes) exhibit social bonds with maternal brothers as well as unrelated adult males, facilitating cooperative behavior, but it is unclear when these bonds develop. Prior studies suggest that social bonds emerge during adolescence. Alternatively, bonds may develop during adulthood when male chimpanzees can gain fitness benefits through alliances used to compete for dominance status. To investigate these possibilities and to determine who formed bonds, we studied the social relationships of adolescent and young adult male chimpanzees (N = 18) at Ngogo in Kibale National Park, Uganda. Adolescent male chimpanzees displayed social bonds with other males, and they did so as often as did young adult males. Adolescent and young adult males frequently joined subgroups with old males. They spent time in proximity to and grooming with old males, although they also did so with their age peers. Controlling for age and age difference, males formed strong association and proximity relationships with their maternal brothers and grooming relationships with their fathers. Grooming bonds between chimpanzee fathers and their adolescent and young adult sons have not been documented before and are unexpected because female chimpanzees mate with multiple males. How fathers recognize their sons and vice versa remains unclear but may be due to familiarity created by relationships earlier in development.Adolescent male chimpanzees, by age 12 years, have as many strong grooming bonds as do young adults.Research HighlightsAdolescent male chimpanzees form social bonds with other males.Bonds were common between unrelated males, but frequent with maternal brothers, peers, old males, and fathers.Fathers may be important for male chimpanzees transitioning to adulthood.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/153616/1/ajp23091.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/153616/2/ajp23091_am.pd

Long‐term trends in fruit production in a tropical forest at Ngogo, Kibale National Park, Uganda

Fruit production in tropical forests varies considerably in space and time, with important implications for frugivorous consumers. Characterizing temporal variation in forest productivity is thus critical for understanding adaptations of tropical forest frugivores, yet long‐term phenology data from the tropics, in particular from African forests, are still scarce. Similarly, as the abiotic factors driving phenology in the tropics are predicted to change with a warming climate, studies documenting the relationship between climatic variables and fruit production are increasingly important. Here, we present data from 19 years of monitoring the phenology of 20 tree species at Ngogo in Kibale National Park, Uganda. Our aims were to characterize short‐ and long‐term trends in productivity and to understand the abiotic factors driving temporal variability in fruit production. Short‐term (month‐to‐month) variability in fruiting was relatively low at Ngogo, and overall fruit production increased significantly through the first half of the study. Among the abiotic variables, we expected to influence phenology patterns (including rainfall, solar irradiance, and average temperature), only average temperature was a significant predictor of monthly fruit production. We discuss these findings as they relate to the resource base of the frugivorous vertebrate community inhabiting Ngogo.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155479/1/btp12764.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155479/2/btp12764_am.pd

Sex-specific association patterns in bonobos and chimpanzees reflect species differences in cooperation

In several group-living species, individuals' social preferences are thought to be influenced by cooperation. For some societies with fission–fusion dynamics, sex-specific association patterns reflect sex differences in cooperation in within- and between-group contexts. In our study, we investigated this hypothesis further by comparing sex-specific association patterns in two closely related species, chimpanzees and bonobos, which differ in the level of between-group competition and in the degree to which sex and kinship influence dyadic cooperation. Here, we used long-term party composition data collected on five chimpanzee and two bonobo communities and assessed, for each individual of 10 years and older, the sex of its top associate and of all conspecifics with whom it associated more frequently than expected by chance. We found clear species differences in association patterns. While in all chimpanzee communities males and females associated more with same-sex partners, in bonobos males and females tended to associate preferentially with females, but the female association preference for other females is lower than in chimpanzees. Our results also show that, for bonobos (but not for chimpanzees), association patterns were predominantly driven by mother–offspring relationships. These species differences in association patterns reflect the high levels of male–male cooperation in chimpanzees and of mother–son cooperation in bonobos. Finally, female chimpanzees showed intense association with a few other females, and male chimpanzees showed more uniform association across males. In bonobos, the most differentiated associations were from males towards females. Chimpanzee male association patterns mirror fundamental human male social traits and, as in humans, may have evolved as a response to strong between-group competition. The lack of such a pattern in a closely related species with a lower degree of between-group competition further supports this notion

Rates of predation on mammals by gombe chimpanzees, 1972–1975

Rates of chimpanzee predation on mammals are calculated using data on 75 kills recorded during focal observation in Gombe National Park, Tanzania, from January 1972 to April 1975. The chimpanzees were members of two study communities (Kanyawara, or Northern, and Kahama, or Southern, community), and were observed as focal individuals for 14,583 hr by more than 30 researchers and field assistants working in pairs. The rate of predation by females was too low to allow reasonable estimates. For males, the mean rate of killing during the study period was 0.31 kills per male per 100 hr ( N =17 males), or 4.65 kills per 100 hr in the two communities. In contrast to results from Mahale Mountains, there was no difference in predation rate between wet and dry seasons. However, predation rates varied over time, increasing by four times between the first three and last four seasons of the sample period. In an average year the 15 adult and subadult male chimpanzees are calculated to have killed 204 prey per year in an area of 16 km 2 , varying between 99 and 420 prey per year in periods of low and high predation rate. Red colobus were the most frequent prey, followed by bushpig and bushbuck. Predation rates varied greatly on different prey species, and were not related to either the proportion of time spent within 200 m of male chimpanzees, or to their population densities. In relation to encounter rates and population density, baboons, blue monkeys, and redtail monkeys were killed at a fraction of the rate of red colobus monkeys, which suffered severe mortality from chimpanzee predation. Predation on bushpig and bushbuck also appears to have been high in relation to population density. The amount of food provided by predation is estimated to have averaged 600 kg per year for chimpanzees in the two communities (totalling 14–17 adult or subadult males, 18–20 adult of subadult females, and about 19 infants or juveniles). This suggests that adult males consumed around 25 kg of meat per year, although any average figure undoubtedly masks considerable individual variation. Present data suggest that chimpanzees in Gombe and Tai National Park, Ivory Coast, prey on mammals at rates higher than other populations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41607/1/10329_2006_Article_BF02380938.pd

Sexual Differences in Chimpanzee Sociality

Scientists usually attribute sexual differences in sociality to sex-specific dispersal patterns and the availability of kin within the social group. In most primates, the dispersing sex, which has fewer kin around, is the less social sex. Chimpanzees fit well into the pattern, with highly social philopatric males and generally solitary dispersing females. However, researchers in West Africa have long suggested that female chimpanzees can be highly social. We investigated whether chimpanzees in the Taï Forest (Côte d’Ivoire) exhibit the expected sexual differences in 3 social parameters: dyadic association, party composition, and grooming interactions. Though we found a significant sexual difference in each of the 3 parameters, with males being more social than females, the actual values do not reveal striking differences between the sexes and do not support the notion of female chimpanzees as asocial: females had dyadic association indices comparable to mixed-sex dyads, spent ca. 82% of their time together with other adult chimpanzees, and had a comparable number of grooming partners. Further, female associations can be among the strongest bonds within the community, indicating that both sexes can have strongly favored association partners. The findings are in contrast to reports on East African chimpanzees, the females of which are mainly solitary and rarely interact with other females. Our results suggest that researchers cannot generally regard chimpanzee females as asocial and need to redefine models deriving patterns of sociality from dispersal patterns to integrate the possibility of high female sociality in male philopatric systems

Long-term Site Fidelity and Individual Home Range Shifts in Lophocebus albigena

We investigated long-term site fidelity of gray-cheeked mangabey (Lophocebus albigena) groups in Kibale National Park, Uganda. Concurrently, we monitored shifts in home range by individual females and subadult and adult males. We documented home range stability by calculating the area of overlap in successive years, and by recording the drift of each group’s monthly centroid from its initial location. Home ranges remained stable for 3 of our 4 groups (overlap over 10 yr >60%). Core areas were more labile, but group centroids drifted an average of only 530 m over the entire decade. Deviations from site fidelity were associated with dispersal or group fission. During natal dispersal, subadult males expanded their home ranges over many months, settling ≤4 home ranges away. Adult males, in contrast, typically dispersed within a few days to an adjacent group in an area of home range overlap. Adult males made solitary forays, but nearly always into areas used by their current group or by a group to which they had previously belonged. After secondary dispersal, they expanded their ranging in the company of their new group, apparently without prior solitary exploration of the new area. Some females also participated in home range shifts. Females shifted home ranges only within social groups, in association with temporary or permanent group splits. Our observations raise the possibility that male mangabeys use a finder-joiner mechanism when moving into new home ranges during secondary dispersal. Similarly, females might learn new resource locations from male immigrants before or during group fission