Effects of food availability and climate on the activity budget of Shortridge's langur (Trachypithecus shortridgei) in the Drung Valley, Gaoligong Mountains, China

Abstract

Food availability and climate represent environmental factors that affect species' social behavior, ranging patterns, diet, and activity budget. From August 2012 to September 2013, we examined the effects of seasonal changes in food availability, temperature, and rainfall on the diet and behavioral ecology of Shortridge's langur (Trachypithecus shortridgei) an Endangered primate species inhabiting moist evergreen broadleaf forests in the Eastern Himalayas. Our field site represents the northernmost latitudinal distribution of this species. Data were collected using scan sampling at 10 min intervals, and analyzed based on generalized linear models. The results indicate that the langurs experienced two feeding peaks (9:00 and 17:00) and two traveling peaks (10:00 and 19:00) during each day. Periods of rest, mainly occurred between 10:00 and 13:00, and overnight. Feeding accounted for 38.5% of the daily activity budget, followed by resting (35%), traveling (24.5%), and socializing (2%). During periods when young leaves were most available, the langurs increased feeding time on young leaves (35% vs. 4%). During periods of maximum fruit availability, the langurs decreased total time spent feeding (36.6% vs. 40.4%), devoted more time to traveling (28.1% vs. 21%), and increased time spent consuming fruit (49.1% vs. 11.8%). During the winter, the langurs increased their consumption of mature leaves (44.5%) and reduced time spent traveling (20.2% vs.

Activity budget and seasonal activity shifts in sympatric lemurs: Increased lean season effort in a cathemeral frugivore contrasts with energy conservation in a diurnal folivore

“…Many species will show seasonal shifts in the time spent active, and if researchers follow these cues, their sampling time will vary across months. These differences will all affect reported percentages, and may have hindered comparisons across studies (Zhang et al, 2023). At the very least, efforts should be made to use consistent sampling strategies across months and populations (Ferrari & Hilário, 2014); standardizing to a 24‐h activity budget (even if it means assuming rest at night) might be the best basis for comparison.…”

“…Many species will show seasonal shifts in the time spent active, and if researchers follow these cues, their sampling time will vary across months. These differences will all affect reported percentages, and may have hindered comparisons across studies (Zhang et al, 2023).…”

“…There is some suggestion that highly divergent responses occur; for example, some populations may try harder, increasing the time devoted to feeding, while others may “give up,” resting more and reducing energy expenditure (energy maximizers and time minimizers: Hixon, 1982). Already, some studies show increased feeding effort in the lean season (Masi et al, 2009; Zhang et al, 2023), while others show reduced effort (Chaves et al, 2011; Pichon & Simmen, 2015; Vasey, 2005) and still others show no change (Arseneau‐Robar et al, 2021; Porter, 2004); travel time can either follow the change in feeding effort, or move in an opposite direction. This variation seems to not align with phylogeny or primary diet type.…”

Effects of provisioning on the activity budget and foraging strategies of black‐and‐white snub‐nosed monkeys (Rhinopithecus bieti) in the Baima Snow Mountain Nature Reserve, Yunnan, China

“…An individual's activity budget can be influenced by a variety of factors such as age, sex (Li et al, 2015; Stevenson, 2006), dominance status, reproductive condition (Lodwick et al, 2004; Matsumoto‐Oda & Oda, 2001), and group size (Chapman & Chapman, 2000), as well as habitat type (Mekonnen et al, 2017; Neves et al, 2023), climate (Korstjens & Dunbar, 2006; Majolo et al, 2013), and the distribution and availability of food resources (Hilário et al, 2021; Bach et al, 2017). Given seasonal variation in patterns of rainfall, temperature, and the availability and distribution of preferred feeding sites, primate populations that only exploit wild foods are expected to show marked seasonal shifts in their activity budget and foraging effort (Majolo et al, 2013; Ni et al, 2015; Zhang et al, 2023). For example, during the dry season, when insects accounted for 72% of feeding time, the proportion of the activity budget that Guianan squirrel monkeys ( Saimiri sciureus ) devoted to feeding and foraging increased and time devoted to resting and socializing decreased.…”