Quantifying Mineral Intake and the Role of Minerals on Food Selection in Angola Black and White Colobus Monkeys (Colobus angolensis palliatus)

Minerals are vital for many metabolic processes, and mineral deficiencies can adversely impact health and fitness. Mineral concentrations of food items are commonly reported in primate nutritional ecology studies and have been identified as important factors in primate food selection; however, very few studies have quantified daily mineral intake of free-ranging primates. We examined the concentration of 9 minerals (Ca, P, Mg, K, Na, Fe, Zn, Cu, and Mn) in foods consumed by <i>Colobus angolensis palliatus</i> inhabiting the Diani Forest of Kenya, and test whether individuals preferentially selected leaves in accordance with their mineral concentrations. We also examined the effects of sex, group, and season on daily mineral intake, quantifying both percentage-based and mass-based intakes. We then compared daily mineral intake values to published recommendations. Behavioral data and plant samples were collected from July 2014 to December 2015. We found that individuals preferred leaves with greater P content and lower Ca content. Daily mineral intake differed significantly between sexes and among groups and seasons. These results are interpretable via differences in time spent feeding and total energy intake. Intakes fell below percentage-based recommendations for P, Na, Fe, Cu, and Mn but met or exceeded mass-based recommendations for all minerals except Na. This discrepancy is likely explained by the conservative nature of percentage-based mineral recommendations and the difficulty of comparing and scaling mass-based mineral recommendations among primate species. Studies that quantify daily mineral intake are needed to better understand the role of minerals on dietary selection, more accurately identify potential mineral deficiencies, and provide more informed recommendations for captive primates.

Diet and Activity Budget in Colobus angolensis ruwenzorii at Nabugabo, Uganda: Are They Energy Maximizers?

<b><i>Introduction:</i></b> Colobine monkeys are specialized folivores that use foregut fermentation to digest leaves. The slow process of fermentation forces them to spend a lot of time resting and to minimize their energy expenditure to subsist on a lower-quality diet. <b><i>Methods:</i></b> We recorded the diet and activity budget of <i>Colobus angolensis ruwenzorii</i>, which form a three-tiered multi-level society, at Lake Nabugabo, Uganda, over 12 months using scan sampling on adults and subadults, to determine whether they utilize the energy minimization strategy typical of colobines. <b><i>Results:</i></b> We found that the annual diet was primarily comprised of high-quality food resources (young leaves 65% and fruit 31%), and fruits were the only plant part the monkeys<i></i>selected when available. Both the fruits and young leaves of some species were preferred food items in some months, and mature leaf consumption correlated negatively with preferred food availability. Mature leaves appear to be a fallback food for this population but are rarely relied upon (3%). The <i>C. a. ruwenzorii</i>at Nabugabo spent less time resting (40%) and more time moving (25%) than is typical for other species of black-and-white colobus. <b><i>Discussion/Conclusion:</i></b> The high-quality diet of this population appears to allow them to utilize an energy maximization strategy. Their reliance on food items that tend to be clumped in space and time likely explains the frequent fission-fusion behaviour that we observe between core units. Our findings demonstrate that the foraging strategies of colobines may be more flexible than was previously thought and illustrate how food availability and distribution can impact primate social organization.

Feeding competition inferred from patch depletion in a supergroup of Rwenzori black-and-white colobus monkeys (Colobus angolensis ruwenzorii) in Rwanda

Competition for food is often a cost associated with living in a group, and can occur in an indirect (scramble) or direct (contest) form. We investigated feeding competition in a supergroup of Rwenzori black-and-white colobus monkeys (Colobus angolensis ruwenzorii) in Rwanda, with the aim of establishing whether freedom from scramble competition allows these monkeys to form supergroups. We used the patch depletion method, measuring intake rate coupled with movement rate, to assess if food patches become depleted over the occupancy period. Resource depletion was evident when the colobus fed on young leaves, but not when feeding on mature leaves. Scramble competition was inferred from a negative correlation between group size and change in intake rate over patch occupancy. Between-group contest competition was inferred from displacement from patches. Although feeding competition exists for select resources, limited competition for mature leaves may enable Rwenzori colobus to live in a supergroup of hundreds of individuals in this montane forest.

The vocal repertoire of an African colobine, Colobus angolensis ruwenzorii: a multi-level society compared to congeners in stable groups

Vocal behaviour offers a window into understanding the social life and evolution of animals. Colobine monkeys show great interspecific and interpopulation variation in their social organization and behaviour. Recent research has shown that Rwenzori Angolan colobus (Colobus angolensis ruwenzorii) differ substantially from other black-and-white colobus in forming a multi-level society. No previous research has been conducted on the communication of C. a. ruwenzorii, but the social complexity hypothesis for communication suggests that more complex societies should evolve more complex communication repertoires. Our objective was to catalogue the vocal repertoire of C. a. ruwenzorii at Nabugabo, Uganda, and to compare it with the data available on congeners regarding intergroup tolerance, vocal repertoire size, and acoustic and behavioural features of vocal communication. Vocalizations were subject to spectrographic and behavioural analysis, and a descriptive analysis of each vocalization type was made. The influence of a few environmental and social factors on calling rates was also examined. We describe five vocalizations (i.e., the snort, roar, squeak, scream and pok) and one non-vocal signal (i.e., the tongue click) in this subspecies and their contexts. Distinct alarm calls are made for dogs, and these are given more often near the edge of the forest where humans frequent. We did not find that C. a. ruwenzorii showed a greater vocal repertoire than C. guereza or C. polykomos, which do not live in multi-level societies. Further, preliminary data do not indicate greater calling rates in larger core units of C. a. ruwenzorii compared to smaller units. These findings support the view that these primates’ vocalizations tend to be relatively conserved despite large differences in social organization.