NORTH-WESTERN JOURNAL OF ZOOLOGY 12 (1): 141-150 NwjZ, Oradea, Romania, 2016 [628124]

NORTH-WESTERN JOURNAL OF ZOOLOGY 12 (1): 141-150 ©NwjZ, Oradea, Romania, 2016
Article No.: e151707 http://biozoojournal s.ro/nwjz/index.html

Relationships between food provisioning patterns, stress and reproductive
parameters of Rhinopithecus roxellana (Milne-Edwards, 1870)

Liangliang YANG1, Shuqiang LIU1, Peilong YU2, Huiliang YU3 and Defu HU1*

1. College of Nature Conservation, Beijing Forestry University, Laboratory of Non-invasive Technology for Endangered Wildlife,
No. 35 Tsinghua East Road, Haid ian District, Beijing, 100083, China
2. Hubei Shennongjia National Nature Reserve, NO. 31 Chulin Road, Muyu, Shennongjia, Hubei, 442421, China
3. Sichuan Snub Nosed Monk ey Research Center, NO. 11 Chulin Road , Muyu, Shennongjia, Hubei, 442421, China
*Corresponding author, D. Hu, Te l.: 13811778288, Email: [anonimizat]

Received: 26. January 2015 / Accepted: 14. July 2015 / Available online: 29. May 2016 / Printed: June 2016

Abstract. Inadequate body condition in wild animals (e specially lactating and gestating females) may be
caused by intense physiological stress, which comp romises reproductive success, thereby reducing
population growth rates. Our study tr oop of Sichuan snub-nosed monkeys ( Rhinopithecus roxellana ) at the
Shennongjia Nature Reserve were subjected to two different food provisioning patterns: (i) an interactive
pattern (all family units fed together; 2006–2008) and (ii) an individualistic pattern (family units fed
separately; 2009-2012). We postulated that fecal glucoc orticoid metabolites (FGM) and birth rates would differ
significantly between monkeys subjected to these two fe eding patterns. Behavioral ranks were assigned by
Dominance Index (DI) values. A Machine Learning (ML) approach was used to assess correlations between
behavioral ranks and infant mortality. We collected 841 fecal samples from 12 adults (7 ♂, 5♀) and monitored
survival of infants borne by 16 females in the period 2006–2012. Infant survival rates were 78.26% % and 93.10
% when the troop was fed interactively and individual istically, respectively. FGM values obtained when
provisioning was interactive were significantly higher than when provisioning was individualistic. In cold
seasons, FGM values obtained when provisioning wa s individualistic were much reduced in comparison
with interactive provisioning. Low rank among females greatly increased the risk of infant death. Thus,
nutritional stress caused by provisio ning pattern is a major contributory factor to overall physiological stress
in Rhinopithecus roxellana females in the Shennongjia Nature Reserve.

Key words: Rhinopithecus roxellana, Fecal glucocorticoid metabolites (FGM), Birth rate, Provisioning pattern,
Shennongjia

Introduction

Wild animal populations face a variety of stresses generated by their physical environments and the biotic interactions within the communities of
which they are members. Although the mecha-
nisms generating stress responses are diverse, the physiological responses are very similar (Sands &
Creel 2004). In wild populations of Sichuan snub-
nosed monkeys ( Rhinopithecus roxellana ) seasonal
variation in food resources may shift foraging strategies and food preferences (Tie et al . 2010). In
well-provisioned groups, va riation in provisioning
pattern may cause similar shifts (Zhang et al . 2006,
Yu et al . 2009a). Furthermore, provisioning pat-
terns shape competition and the imbalance in food
distribution among the social units, thereby gen-
erating chronic physiological stress. Inevitably, food competition and imbalance lead to dietary deficiencies, and even nutritional stress, at the in-
dividual organism level (Pedro & Rutledge 2001,
Alejandro et al . 2014). The nutritional stress result-
ing from long-term food deficiency is the result of a concatenation of negative influences on the body
condition of individual an imals, such as retarded
physical development, slow recovery from ill-
nesses, and digestive dysfunction (Sapolsky 2005).
Individuals and groups of non-human pri-
mates commonly compete for resources (Wrangham & Waterman 1981, Van Schaik 1983,
Robinson 1988, Van Schaik & Van Noordwijk
1989, Radespiel et al . 1998, Digby 1999, Koenig
2002). Ranks in hierarchically organized non-human primate societies play an important role in
resource distribution (Zhang et al . 2006, Yu et al.
2009a), particularly food resources. The availabil-ity of food resources has a great influence on the
size and nutritional status of animal populations;
these effects have b een well studied (Munck et al .
1984, Van Schaik & Van Noordwijk 1989, Piatt & Anderson 1996, Radespiel et al . 1998, Digby 1999,
Koenig 2002, Chapman et al . 2006, Li 2005, Piatt &
Harding 2007, Kitaysky et al . 2010). High-ranking
individuals drive away those of lower rank when the two are feeding together (Scott & Lockard
2006). Because lower-ranking individuals are out-

L. Yang et al.
142
competed (Thierry et al . 2004) their fecal glucocor-
ticoid metabolites (FGM) levels can be relatively
elevated (in comparison with higher-ranking indi-
viduals) (Davis & Christian 1957, Manogue 1975, Sapolsky 1985, 1990, 2005, Bercovitch & Clarke
1995, Sands & Creel 2004). Higher-ranking females
may dominate those of lower rank (Ren et al .
2000); during the breeding season, low-ranking females have elevated FGM levels resulting from
the aggression of dominant females (Cavigelli et
al. 2003) .
The two genders of mammals have different
responsibilities in reproduction and infant care
(Trivers 1972). Females are more likely to be af-
fected by food competition than males (Koenig 2002), especially during parturition and lactation. Adult females are likely to lose infants due to nu-
tritional stress caused by food deficiencies (Trites
1991, Calkins et al . 1998). The effects of nutritional
deficiency stress on animal reproductive success and infant survival have been well studied (Cairns
1987, Robbins 1993, Sapolsky 1992b, Liptrap 1993,
Dobson & Smith 1994, Murray et al . 1998, Sapol-
sky et al . 2000, Kitaysky et al . 2007, Oro & Furness
2002, Grosbois & Thompson 2005, Sandvik et al .
2005, Kitaysky et al . 2010). Physiological and nu-
tritional stressors may have many harmful effects on females during breeding and lactation periods (Kennedy & Visness 1992, Wade & Schneider 1992,
McNeilly et al . 1994). Physiological stress can im-
pair the reproductive system (Liptrap 1993, Dob-son & Smith 1994, Kitaysky et al . 2010) and reduce
the survival rate of infants (Oro & Furness 2002,
Grosbois & Thompson 2005, Sandvik et al . 2005) of
wild animals, thereby impacting population growth rate (Colin et al. 2006). Other factors that
influence female primate body condition, such as
social bonds (Silk et al. 2003), social ranks and food availability (Van Noordwijk & Van Schaik 1999) may also affect infant survival. Reproductive
success rates of individual females are parameters
of population dynamic modeling (Robinson 1988, Romero & Wikelski 2000, Colin et al . 2006, Kitay-
sky et al . 2007, 2010).
Here we report on a study of Sichuan snub-
nosed monkeys ( Rhinopithecus roxellana ) living in a
provisioned troop with a territory of 300 km
2, in-
cluding a 300 m2 feeding area and a 220 km2 active
area (Yu et al . 2009b). These monkeys have two
types of social units: “one male units” (OMUs) and “all male units” (AMUs) (Chen 1989, Kirkpatrick 1995, Ren et al . 2000). Both OMUs and
AMUs were provisioned by rangers at the reserve.

Figure 1. Separation distances between family
units fed by interactive and individualistic pat-
tern provisioning (Interactions provisioning pat-
tern. Individualistic prov isioning pattern, Note:
▲ – units; ● – food piles).

Food was supplied in two provisioning patterns
(Fig. 1): when food was supplied in a concentric
pattern at a single site prior to 2008, we identified
the pattern of provisioning as “interactive” (Yu et al. 2009b); when food was provided separately to
each social unit after 2008, we identified the pat-
tern as “individualistic” (Yu 2012). The amount of
food supplied to each individual animal was simi-lar between the two provisioning patterns. The provisioning pattern affected dominance behavior
during feeding (Yuan et al . 2009); thus, the interac-
tive pattern reduced the distances among units to 0.5–10 m (Zhang et al . 2003). Elevated psychologi-
cal suppression through eye and body contact fre-
quently escalated to aggr essive warning signaling
and fierce fighting among units (Zhang et al . 2003,
Yu et al . 2009b), which increased physiological
suppression among troop individuals. High levels
of stress caused by nutritional deficiency and ag-
gressive behaviors can reduce infant survival rates (Trites 1991).
In this study, we used an open-access data ap-
proach for transparency and repeatability to assess factors likely to be associated with physiological stress (i.e., FGM) in R. roxellana living in the Shen-
nongjia Nature Reserve. We used powerful data
searching and Machine Learning techniques (Jochum & Huettmann 2010) to test whether: 1) provisioning patterns affect physiological stress, 2)

Physiological stress induced by provisioning pattern influences reproductive success
143
nutritional stress caused by provisioning pattern
critically affects female physiological stress levels,
3) provision patterns affect the survival rate of in-
fants, and 4) ranks influence the survival rates of infants.

Materials and methods

Our research was performed at the Dalongtan observa-
tion site in Shennongjia National Nature Reserve, Hubei
province (31°22 ′–31°37′N, 110°03 ′–110°34′E). The site en-
compasses an area of 800 m2 (2160 m above sea level)
where the vegetation comprises dense mixed stands of
deciduous and evergreen broadleaf and coniferous trees
(Zhu & Shu 1999). Canopy de nsity was high. Water was
supplied abundantly by 2 rivers and 12 streams (Yuan et
al. 2009). The feeding ground (300 m2) of R. roxellana was
located on the banks of a river flowing through the study
area. The mean annual temperature was 11.0–12.2 °C;
highest temperatures of ca. 21.2–26.5 °C occurred in July,
and lowest temperatures of ca. –5.8 to –3.6 °C in January.
The period May–October had moderate temperatures; the
period January–December was cold. The annual mean
frost-free period was 173 d. For our study, we divided the
year into a warm season (May through October), with a
mean daily temperature ≥0 °C, and a cold season (No-
vember through April) with temperatures < 0 °C.

Sample collection
The study extended from 2006 to 2012. We collected 841
fecal samples from 12 Sichuan snub-nosed monkeys at the
study site and used infrared distance sensors to measure
the distances among the social units. Fecal samples were
collected at Dalongtan during two different time periods;
i.e., in the warm (July–August) and cold (November–
December) months of 2008. During 2008, we collected 620
fecal samples from 10 adults at intervals of 5 days (5 ♂,
5♀). In the second time period, we again made collections
in the warm (June–August, 2011) and cold months (No-
vember, 2011–February, 2012). In the period 2011–2012,
we collected 207 fecal sample s from 11 adult animals (2 ♂,
9♀) in two social units.
We also recorded the births and deaths of infants
borne by 16 females at the Dalongtan observation site in
the period 2006–2012, when 52 infants were born. Accord-
ing to the records of the reserve, 23 were born in the in-
teractive provisioning period (2006–2008); five deaths
were attributed to stillbirth and disease over 3 yr. Dates of
death were as follows: Decemb er 26, 2006 (infectious dis-
ease; poor health condition), March 11, 2008 (sick, lived
for 2 days), March 31, 2008 (stillbirth), April 5, 2008 (still-
birth), April 20, 2008 (s ick, lived for 1 day).
Twenty-nine infants were born to the same troop
during individualistic pattern provisioning period (2009–
2012), and four of these died. Replacement of the alpha
male resulted in the killing of two infants in the social
unit during April 2012. One in fant died during stillbirth
(January 19, 2012) and another from disease (April 5, 2012). Differences in provisioning patterns:

We adopted the interactive pattern for provisioning the R.
roxellana individuals in Dalongtan prior to 2009. All fam-
ily units gathered within the feeding area for forage; the
units were 0.5–10 m apart. After 2009, the units were fed
individualistically, and were spaced at distances of 5–15
m.

The extraction and determination of cortisol:
Extraction proceeded with the addition of 5 ml of 90 %
ethanol to ca. 0.5 g of fres h fecal sample. Samples were
vortexed for 30 s, and then centrifuged at 4000 rpm/min
for 25 min. The supernatant was recovered, and the pellet
was re-suspended in an additi onal 5 ml of 90 % ethanol in
the original tube, vibrated for 30 s, and then centrifuged
for 20 min at 4000 rpm/min. Ethanol supernatants were
combined, taken to dryness in a water bath at 70 °C, and
then re-suspended in 1 ml of methanol. We added 1 ml of
diluent (NaH 2PO 4; Na 2HPO 4; NaCl in Milli-Q H 2O; pH =
7.0) and sonicated the mixture for 15 min using an ultra-
sonic wave device. Samples were stored at –20 °C until analysis.

FGM testing method:

We used an enzyme-linked immunoabsorbent assay
(EIA) to determine the concentration of FGM. The proce-
dure was initiated by coating plates with cortisol-3 anti-
body (M344, CalBioreagent) at a working concentration of
1:500 (vol/vol). The plates were kept at 4 °C for 24 h. A
standard solution was diluted 1 to 1024-fold in a step-by-
step procedure. High- and low-quality controls (binding at 30% and 70%) were prepared from a cortisol-3 HRP so-
lution (C133, CalBioreagent) at a working concentration
of 1:10,000 (vol/vol). Extractions were diluted to a con-
centration of 1:4 (vol/vol). Two wells in each multi-well
plate were left as blanks to remove zero disturbances. To
the other cells, we added (i) 50 μl of the standard dilution,
(ii) controls and (iii) HRP solution. After 1 hour combin-
ing at 35 °C, washed plates 3 times with wash solution
(NaCl: 43.83 g (Sigma, S9625) , Tween 20:2.5 ml (Sigma,
P1379), and H2O: 500 ml). Added 100 μl TMB solution for
15 minutes, then added 50 μl stop solution to each well.
Read the plates at 450 nm.
Cortisol-3 antibody (M344, CalBioreagent), standard
sample and cortisol-3 HRP (C133, CalBioreagent) are all
purchased from CalBioreagents Company; ELISA Plate is
NUNC C445101 Bottom Well. Working concentrations are
respectively as follows: Cortisol-3 antibody is diluted at
1:500 and cortisol-3 HRP at 1:15,000. The sensitiveness of
ELISA Plate is 0.5 ng/ml with 8-15% inter plates and 4-6%
inter plate.

Parallelism and recovery rate determination

We tested the validity of the assay by testing serial dilu-
tions of fecal extract against a FGM standard curve (y =
3.638 – 1.789(X); R2 = 0.988, r = 0.984; P < 0.01). For con-
centrations in the range 10–500 ng/ml, sensitivity was 50
pg/tube. The buffer blanks were below the limit of sensi-
tivity. The coefficients of variation (CV) within batches
were ＜5%; CV values among batches were ＜10%. The
average recovery rate was 85.19%.

L. Yang et al.
144
Determination of distance and behavioral monitoring
Infrared sensors were used to measure the intra-unit dis-
tances. Data prior to 2009 were obtained from Zhang et al .
(2003) and Yu et al . (2009b). Our behavioral sampling
procedure followed the methods of Li et al . (2006); we re-
corded the durations of aggressive (AT) and submissive
behaviors (ST) for each indi vidual studied. Animals were
observed and the data were compiled for 3 h on every
third day through the years 2008, 2011 and 2012. We de-fined the following as AT: driving away, lunging, chas-
ing, grasping and hitting, wrestling and biting. We de-
fined the following as ST: avoidance, crouching, retreat-ing and fleeing (Yan et al ., 2006). The Dominance Index
(DI) was calculated as DI= (%AT)/(%ST)×100 for each in-
dividual (as a reflection of social rank).

Data processing

For our multivariate Machine Learning analysis, we used
the robust TreeNet algorithm (a boosting tree analysis
procedure), which described patterns and details of the signals (Cushman & Huettmann 2010, Drew et al . 2011).
Unlike other statistical approa ches and software, TreeNet
allows assessments of statis tical interactions (Friedman
1999, 2002). Interactions ar e problematic for most linear
analyses and are currently not well resolved statistically.
However, they are inherent in all behavioral and wildlife
data, and they are essential components that should be
included in any complex anal ysis. The interactions pre-
sented here are two-way and based on classification trees,
boosting and bagging (Friedman 2002).
Our FGM data were not normally distributed, and
we therefore adopted non-parametric statistical proce-dures (two-sample Kolmogorov-Smirnov test performed
with SPSS ver. 17.0 software). Statistical significance was
recognized when P < 0.05. We used SigmaPlot 10.0 soft-
ware to plot the charts.

Ethical note and underlying open access data

This study was fully endorsed by both the Hubei Sichuan
Snub-nosed Monkey Research Center and the Shennong-
jia National Nature Reserve, and received final approval
from the Institutional Animal Care and Use Committee
(IACUC) at the College of Nature Conservation, Beijing
Forestry University. All of the sampling activities were
conducted in collaboration with technical staff of the
Shennongjia National Nature Reserve. We took particular
care to avoid disturbing the animals during fecal sam-
pling and behavioral observations. Thus, we spent about
2 weeks familiarizing the monkeys with our research
staff. We wore camouflage clothing to reduce animal
stress. Results

Food resources
In total 202 species of plan ts were selected as food
by R. roxellana in the Shennongjia region (Table 1).
The seasonal variation in food composition was
described by Tie (2009).

FGM levels comparison:
Average FGM values were 121.57±2.74 ng/g in the cold seasons and 125.21±3.29 ng/g in the warm
seasons when the troop was provisioned in the in-
teractive pattern (2006–2009). Values were not sta-tistically different between cold and warm seasons (N = 620, Z = 1.24, P = 0.092). However, when the
monkeys were provisioned in the individualistic
pattern, the average FGM values were 27.51±2.67 ng/g in cold seasons and 86.09±5.09 ng/g in warm
seasons (2009–2012). The difference was statisti-
cally significant ( N = 196, Z = 4.542, P < 0.001). The
overall FGM levels during interactive pattern pro-visioning were significantly higher than those dur-
ing individualistic pattern provisioning ( N = 801,
Z = 6.889, P < 0.001; two-sample Kolmogorov-
Smirnov test) (Fig. 2).

Figure 2. Fecal glucocorticoid metabolite (FGM) levels of
monkeys subjected to two patterns of food provisioning
in cold and warm seasons. Different lower case letters
indicate significant differences between seasons ( P <
0.01); different upper case letters indicate significant dif-
ferences between provisioning patterns ( P < 0.01).
(Note: a vs b (P<0.01); A vs B (P<0.01)).

Table 1. Numbers of food types used by Sichuan snub-nos ed Monkeys at the Shennongjia Nature Reserve.

Woody plants Season Trees Shrubs Climbers Herbaceous plants Lichens
Spring 73 57 21 15 4
Summer 51 56 15 13 4
Autumn 44 40 15 6 4
Winter 9 6 0 0 4
Year-round 91 69 21 17 4

Physiological stress induced by provisioning pattern influences reproductive success
145
Table 2. Infant births and deaths during the period 2006–2012.

Provisioning pattern Individual Infant birth Infant death Death rate
DaDa 1 1 100 %
JuZ 2 1 50 %
LL 1 1 100 % Interactive
HZ 2 2 100 %
HuanHuan 2 1 50 % Individualistic
XH 1 1 100 %

Figure 3. Total population size, numbers of live births
and infant deaths during the period 2006–2012 in the
group of Sichuan snub-nosed monkeys at the Dalongtan
observation site, Shennongjia Nature Reserve.

Four individuals were re-sampled in this
study [YY ( ♀), DWB ( ♀), BT (♂) and XX ( ♂)]. We
compared the FGM values of these four individu-
als between cold and warm seasons with two dif-ferent provisioning patterns. When the provision-ing pattern was interactive, FGM values for fe-
males were similar between seasons (YY: F =
2.880, P = 0.109; DWB: F = 2.344, P=0.144). How-
ever, when the provisioning pattern was indi-vidualistic, FGM values for females were signifi-
cantly higher in the cold season (YY: F = 7.847, P =
0.007; DWB: F = 10.603, P = 0.002) in the period
2008–2011. FGM values for males were seasonally
significant different with interactive pattern provi-
sioning (BT: F = 75.905, P < 0.001; XX: F = 10.603, P
= 0.002) and did not show any difference with in-dividualistic pattern provisioning (BT: F = 0.723, P
= 0.398 [one-way ANOVA]; XX: U = 866.00, P =
0.262 (Mann-Whitney U test).

Survival rate of newborn monkeys

During the period 2006–2012, 52 infants were born at the study site. Five died during interactive pat-
tern provisioning and two during individualistic
pattern provisioning (Table 2). Eighteen adult fe-males at the study site mated in the period till the end of 2008. The same proportion of females
mated in the later period till the end of 2012. The monkey population grew from 45 in 2006 to 65 in 2012 (Fig. 3). The average survival rate of infants
was 78.26% with interactive pattern provisioning
(2006–2008) and 93.10% with individualistic pat-tern provisioning (2009–2012).

Rank of female individuals

We used the DI values for 2008 to construct a
dominance hierarchy for the female monkeys in all
OMUs (Table 3) (Yu et al . 2009b). Adult females
that lost infants had the lowest rank within their
units. The units they belonged to were lower than
in the ones where no infants died. The relationship between behavioral rank, FGM and the number of infant deaths is depicted in Figure 4. Infant deaths
were elevated among females of low rank and
when FGM values exceeded 200 units. FGM val-ues between 40 and 200 units were negatively cor-related with infant death. Table 4 presents two-
way interactions between factors (based on classi-
fication trees). Rank in the dominance hierarchy had the highest importance value.

Discussion

When subjected to the interactive provisioning pattern, family units of the monkeys were forced to circle and compete for food at distances of 0.5–
10 m. This provisioning pattern led to an imbal-
ance in food distribution due to rank differences. Individuals fought for su fficient food, and aggres-
sive behaviors were clearly observable (Yu et al .
2009b). In the wild, the distances between Sichuan snub-nosed monkey troops are always 10–50 m, and aggressive behaviors are seldom observed (Lu
2007, Yu et al . 2009b). Complete visual exposure to
other family units during feeding may promote physical conflict. Frequent fighting and warning behaviors occur as a consequence of competition
for resources, particularly during reproductive
seasons (Zhang et al . 2003, Yu et al . 2009b). How-

L. Yang et al.
146

Table 3. Dominance hierarchy ranks of members in each family unit of Sichuan snub-nosed monkeys at the Dalongtan
observation site, Shennongjia Nature Reserve.

Interactive pattern Individualistic pattern
Ranks HT Unita(DI) CM Unit (DI) BT Unit (DI) XX Unit (DI)
(Yu Yang, 2012) DDUnit (DI)
(Yu Yang, 2012) DY Unit (DI)
1 HT
(0. 50 ± 0.12) CM
(0. 50 ± 0. 09) BT
(0. 47 ± 0. 12) XX
(1.00 ±0.00) DD
(0. 99 ± 0. 14) DY
(0.97±0.12)
2 LN
(0. 34 ± 0. 29) JJ
(0. 41 ± 0. 12) TT
(0. 44 ± 0. 17) NN
(0. 83 ± 0. 17) JJ
(0. 77 ± 0. 18) HuHu
(0.86±0.21)
3 HuHu
(0. 34 ± 0. 21) JZ*
(0. 35 ± 0. 49) DWB
(0. 44 ± 0. 17) LL
(0. 62 ± 0. 20) LN
(0. 56 ± 0. 21) HuanHuan*
(0.58±0.13)
4 GP
(0. 31 ± 0. 29) HZ*
(0. 25 ± 0. 25) XWB
(0. 43 ± 0. 17) BB
(0. 51 ± 0. 21) YinYin
(0. 48 ± 0. 22) XH*
(0.45±0.20)
5 HuanHuan
(0. 29 ± 0. 18) YingYing
(0. 38 ± 0. 23) TianTian
(0. 33 ± 0. 21) XL
(0. 20 ± 0. 20)
6 QQ
(0. 27 ± 0. 26) NN
(0. 36 ± 0. 24) WF
(0. 16 ± 0. 12) GG
(0. 00± 0. 00)
7 HuiHui
(0. 25 ± 0. 29) HH
(0. 35 ± 0. 25) HongHaier
(0. 04 ± 0. 04)
8 BB
(0. 17 ± 0. 25) DaDa*
(0. 34 ± 0. 24)
9 DouDou
(0. 17 ± 0. 29) WF
(0. 29 ± 0. 27)
10 YinYin
(0. 14 ± 0. 24) LL*
(0. 25 ± 0. 29)
11 TianTian
(0. 06 ± 0. 18) XL
(0. 10 ± 0. 22)

* Individuals who lost infants; a, units are identified by th e dominant individual (e.g., HT); DI, dominance index;
individuals are identified by either two upper ca se letters or by their names (e.g., HT and HuHu)

(A)

(B)
.

Figure 4. Relationship between numbers of infant deaths, dominance ranks of females and fecal glu-
cocorticoid metabolites (FGM) determined by the Tr eeNet algorithm (Note: A: Rank was classified
from 1 to 11; 1 means highest rank and 11 means the lowest rank. The death of infants increased
with the rank reduced; B: Number of infants death increased with the FGM levels increased).

Physiological stress induced by provisioning pattern influences reproductive success
147
Table 4. Two-way interactions calculated by the
TreeNet algorithm (Friedman 1999, 2002).

Factor Importance Value
RANK 51.70
UNIT 24.85
FGM 16.82
SEASON 5.70
PROVISION PATTERN 0.31

RANK, female position in the do minance hierarchy (see Table 3);
UNIT, family unit, FGM, fecal glucocorticoid metabolites; SEA-
SON, cool and warm periods of the year; PROVISION PAT-TERN, interactive vs. individualistic pattern provisioning

ever, these phenomena have rarely been observed
in wild troops (Lu 2007).
The individualistic provisioning pattern pro-
moted wide spacing between family units, each of
which had an independent feeding space. Eye, physical contact and aggressive behaviors de-creased greatly during feed ing. The overall stress
levels of the whole troop and the family units
were reduced compared to levels measured when provisioning was interactive.
We found that environmental factors (e.g.,
temperature and habitat quality) were unrelated
to high FGM values in cold seasons. The interac-tive provisioning pattern caused an imbalance in food distribution between high- and low-ranking
individuals. Artificial provisioning is the only
mechanism that provides adequate food supplies for these wild monkeys during winter when food resources are limited (Table 1) (Li 2006, Tie et al .
2010). When the troop was interactively provi-
sioned, low-ranking individuals found it difficult to obtain sufficient food within the 300-m
2 area
available at Dalongtan. Shortages of food pro-
moted fierce competition for resources and in-
creased the FGM level of the entire troop, causing high levels of chronic stress in pregnant and lactat-ing individuals. Mortality is high and the birth
rate is low among monkeys at Shennongjia during
winter (Li et al . 2005).
When the provisioning pattern was individu-
alistic, FGM values were significantly different be-
tween warm and cold months of the year (Fig. 2). The breeding seasons overlapped with the warm season. During the breeding seasons, males fought
for mating opportunities. The entire troop was in-
fluenced by this fierce competition, which was correlated with significan t increases in FGM val-
ues. When adequately provisioned, the monkeys
were more peaceful during the cold seasons. How-
ever, when the monkeys were provisioned in the interactive pattern, members of the troop com-
peted for food in the cold season and FGM values
o f t h e e n t i r e t r o o p w e r e a s h i g h a s t h o s e i n t h e
breeding (warm) seasons.
Rank was the most important factor influenc-
ing infant death rates. High-ranking individuals
h a d m o r e o p p o r t u n i t i e s t o a c c e s s f o o d r e s o u r c e s
and drove away those belonging to inferior rank (Ren et al . 2003, Zhang et al . 2003, Yu et al . 2009a).
A study on king colobus ( Colobus polykomos )
showed that competition among female individu-
als is correlated with food resource availability (Korstjens et al . 2006); thus, during the breeding
season the FGM levels of lower-ranking females
were elevated because they were exposed to more
aggression (Cavigelli et al . 2003). Koenig . (2002)
pointed out that in top-down hierarchical societies of non-human primates lower-ranking individuals
are inferior in the competition for resources and
breeding opportunities. Losing the competition for resources can elevate the FGM levels of lower-ranking individuals (Davis & Christian 1957,
Manogue 1975, Sapolsky 1985, 1990, 2005, Berco-
vitch & Clarke 1995, Sands & Creel 2004). Short-ages of food intensify the nutritional stress of low-
ranking individuals (Wrangham 1980, Whitten
1983, Thierry et al . 2004), thereby increasing
physiological stress and degrading body condi-
tion. Chapman et al . (2006) showed that nutri-
tional deficiency is the main cause of population
declines in colobus monkeys ( Procolobus rufomitra-
tus). Trites and Donnelly (2003) found that Steller’s
sea lions ( Eumetopias jubatus ) experienced nutri-
tional stress when food supplies were deficient,
with consequent reductions in the birth rate.
Low-ranking adult female Sichuan snub-
nosed monkeys may suffer stillbirth during partu-
rition due to food defic iencies and stress. Chronic
stress can damage the reproductive system (Ab-bott 1997, Carlstead & Brown 2005, Alejandro et al.
2014) and decrease the survival of offspring (Oro
& Furness 2002, Grosbois & Thompson 2005,
Sandvik et al . 2005). A low stress level guarantees
a high offspring survival rate and promotes popu-
lation growth (Colin et al . 2006). Feeding provi-
sion patterns have a direct influence on food dis-
tribution among individuals. When the distribu-tion is highly skewed, infants may die of nutri-tional deficiency and infectious diseases during
the lactation period. In our study, infant deaths
were restricted to the cold season (November to April), which is the period of the year when fe-males give birth and feed milk to their offspring.

L. Yang et al.
148
The pattern of food provisioning greatly influ-
enced the survival rate of infants: survival rates
were 78.26 % and 93.10 % when the provisioning
patterns were interactive and individualistic, re-spectively. Thus, the death of infants was closely
related to the peak of physiological stress imposed
by the different feeding patterns.
Conclusions

Based on our analysis we conclude that: 1) the
survival rate of infants increased from 78.26 % with interactive pattern provisioning to 93.10 % with individualistic pattern provisioning; 2) inter-
active pattern provisioning caused increases in the
troop FGM levels compared to individualistic pat-tern provisioning (Interac tive pattern provisioning
intensified aggressive behaviors, and exacerbated
imbalances in food distribution during cold sea-
sons, thereby increasing lev els of food deficiency
and physiological stress. Individualistic pattern
provisioning reduced conflict and competition
among family units and individuals to some de-
gree, which in turn reduced physiological stress); 3) Female rank markedly influenced infant death rates. Low-ranking female individuals suffered
severe nutritional stress, especially in cold seasons
when food was provided by interactive provision-
ing, and often lost new-born infants in conse-
quence; 4) Nutritional stress increased overall
physiological stress in females during cold sea-sons.

Acknowledgments. Funding for this project was
provided by the Special Fund for Forestry Scientific
Research in the Public Interest, Chinese Ministry of
Science and Technology (No. 201004054). We thank the
Shennongjia National Nature Reserve at Hubei Province
China for allowing us to pursue our research on their site;
we also thank Liao Mingyao, Zhao Benyuan and Yang
Jinglong for their assistance, and Zhang Dong and Eric
Isai for editing and providing advice on the manuscript.

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