Seasonality of group size, feeding, and breeding in wild red‐shanked douc langurs (Lao PDR)

Abstract

In Asian colobines, small one-male groups (OMG) seem to predominate alongside all-male groups (AMG), while larger multimale groups (MMG) are rare, but are reported for Hanuman langurs and red-shanked douc langurs. Recently, however, it has been speculated that the genus Pygathrix could have multilevel societies based on (1) a theoretical extension of the multilevel societies found in Rhinopithecus to all odd-nosed colobines and (2) first data for black-shanked douc langurs. This assumes bands composed of small OMG with a skewed adult sex ratio. Band size may vary with seasonal food availability resulting in smaller bands when feeding competition is increased. To investigate the social organization of red-shanked douc langurs and potential seasonal influences, we observed 2 unhabituated groups at Hin Namno National Protected Area, Lao PDR from March 2007 to August 2008 for 803 hr. We recorded births and performed group counts and scan sampling of feeding behavior. Most births (79% of N = 15) occurred from June-September, indicating a 4-month peak conception season from November to February. Group size averaged 24.5 individuals (range 17-45) with 2.45 adult males (range 1-4). Although the smaller group remained at a stable size (about 18 individuals), the larger group reduced from about 45 to 25 individuals during the 7-months long lean season, when less than 50% of the feeding time was spent on fruits. This suggests feeding competition as a potential cause of seasonal variation in group size. With 1.9 females per male the skew in adult sex ratio was much lower compared with Rhinopithecus, indicating MMG rather than multilevel societies. However, data on the spacing and interaction patterns between recognized individuals need to be collected and analyzed before the social organization can be determined. Detailed ecological data are furthermore required to investigate the basis for the seasonal changes in group size found.

Seasonality of reproductive events and early mortality in a colony of hamadryas baboons (Papio hamadryas hamadryas) over a 30‐year period: Capital breeding and life history patterns in a food‐provisioned population seasonally thermally stressed

“…In fact, if we use van Schaik et al's [] definition of moderate seasonality (i.e., 33–67% of reproductive events occurring within a 3‐month period), then we must conclude that the females from this study can be said to exhibit a moderate seasonal clustering of all four reproductive events. This pattern has also been described in wild baboons [e.g., Bercovitch & Harding, ; Cheney et al, ; Lycett et al, ] and in other primate species that share a similar capital breeding pattern [e.g., Bercovitch & Harding, ; Cheney et al, ; Crockett & Rudran, ; Furuichi et al, ; Lycett et al, ; Phiapalath et al, ; van Noordwijk & van Schaik, ; Wallis, ]. Actually, for all the reproductive events analyzed, the number of consecutive months during which they clustered together tended to be greater than 3 (Fig.…”

Bacterial community structure and function distinguish gut sites in captive red‐shanked doucs (Pygathrix nemaeus)

“…The red‐shanked douc, the focus of this study, is a species of Asian colobine that inhabits east‐central Lao People's Democratic Republic (PDR), northern and central Vietnam, and northern Cambodia. It is an endangered primate that is of great concern to conservationists (Heistermann, Ademmer, & Kaumanns, ; Nadler, Momberg, Dang, & Lormee, ; Phiapalath, Borrie, & Suwanwaree, ; Timmins & Duckworth, ). The specialized, sacculated foregut of colobines is unique amongst primates, as it allows not only for enzymatic digestion in the stomach but also mechanical and bacterial digestion (Nijboer et al, ).…”

“…Both are folivorous and have evolved a multichambered stomach, allowing them to consume a diet that is nutritionally unfavorable compared with other food sources. However, although foliage is less nutritionally dense, it is more abundant for longer portions of the year than other food items, such as fruit or meat (Phiapalath et al, ). The first chamber of this complex stomach acts as a fermentation chamber and is responsible for digestion of plant carbohydrates, which cannot be digested by animals with simple stomachs.…”

Surviving at the highest and coldest: Nutritional and chemical components of fallback foods for Yunnan snub‐nosed monkeys

“…( 2020 ) nemaeus Phiapalath et al. ( 2011 ) nigripes Rawson ( 2009 ), Roos et al. ( 2011 ) Rhinopithecus avunculus Rowe and Myers ( 2016 ), Hai ( 2012 ) bieti Present study; Rowe and Myers ( 2016 ) brelichi Xiang et al.…”