Observations on Sambar Rusa unicolor (Cetartiodactyla: Cervidae) stags during hard and
velvet stages of antler cycle in captivity
V.
Vishnu Savanth 1, P.C. Saseendran 2, K.S. Anil 3,
V. Ramnath 4, Justin Davis 5 & A. Prasad6
1 PhD
Scholar, 2 Professor and Head, 3 Associate Professor, 5,6Assistant
Professor, Department of Livestock Production Management, 4 Associate
Professor, Department of Veterinary Physiology,
College of
Veterinary and Animal Sciences, Thrissur, Kerala 680651, India
Email: 1vishnusavanth@rediffmail.com (corresponding author), 2 sasipcs@yahoo.co.in,3 anilkundukulam@hotmail.com, 4 drvrnath@gmail.com
Date of
publication (online): 26 October 2011
Date of
publication (print): 26 October 2011
ISSN
0974-7907 (online) | 0974-7893 (print)
Editor: L.A.K. Singh
Manuscript details:
Ms # o2672
Received 11 January 2011
Final received 09 September 2011
Finally accepted 15 September 2011
Citation: Savanth,
V.V., P.C. Saseendran, K.S. Anil, V. Ramnath, J. Davis & A. Prasad (2011).
Observations on Sambar Rusa unicolor (Cetartiodactyla:
Cervidae) stags during hard and velvet stages of antler cycle in captivity. Journal
of Threatened Taxa 3(10): 2128–2135.
Copyright: © V. Vishnu
Savanth, P.C. Saseendran, K.S. Anil, V. Ramnath, Justin Davis & A. Prasad
2011. Creative Commons Attribution 3.0Unported License. JoTT allows
unrestricted use of this article in any medium for non-profit purposes,
reproduction and distribution by providing adequate credit to the authors and
the source of publication.
Author
Details: V.V. Savanthis pursuing his PhD on non human primate reproduction. P.C.
Saseendran and K.S. Anilare working on hormonal population
control in non human primates, healthcare and management of captive elephants
and human-elephant conflict mitigation. V. Ramnath is undertaking
research on stress physiology and antioxidants, cancer biochemistry, molecular
biology, tumour immunology, radio biology and animal cell culture
technology. Justin Davis is delving to find
managemental interventions to improve dairy farming. A. Prasad is
working to explore climatological adaptation in mammals
Author
Contribution: The work was part of the MVSc research of
the first author. The co-authors guided with technical inputs for the research
as well as preparation of the manuscript.
Acknowledgements:The research was funded by Kerala Agricultural
University. We are thankful to The Director, Directorate of Museums and Zoos, Thiruvananthapuram
and the Superintendent of State Museum and Zoo, Thrissur for providing
facilities for the research. The help by Dr. Sunil, Veterinary Surgeon of the
State Museum and Zoo, is also acknowledged.
Abstract: This
research was carried out at the State Museum and Zoo, Thrissur, Kerala, India
from June to October, 2009. The objective was to observe and record the
physical and behavioural changes in Sambar Deer Rusa
unicolor stags linked to their territorial display during
various stages of the breeding cycle. In total, there were 70 Sambar in the
enclosure, at the commencement of the study, of which 22 were males including
16 adult stags. Six stags were selected for the study. Observations were made by
focal animal sampling technique. An ethogram was devised and behavioural
patterns were indicated on it. The behavioural score derived from the ethogram
was significantly higher in stags in their hard antler stage when compared to
the stags in the velvet stage. The stags in the hard antler stage were more
massive, had bigger antlers, darker coat colour, thicker neck, larger scrotum
and maintained a larger ‘harem’ in comparison to the velvet stage stags which
preferred a rather subdued life. The most dominant stags in the hard antler
stage had up to 17 female members in his territory. As the stags in velvet
entered the rut season, the dominant stag had up to 19 females in his
territory. The study is expected to be useful to evolve strategies to identify
and reduce a few males not contributing in breeding in any particular enclosure
and thus curtail expenses in management of cervids in captivity.
Keywords: Rusa
unicolor, captive management, dominance hierarchy, ethogram.
For figures, table -- click
here
Introduction
Behavioural
variation in ungulate populations is an area of research, which could provide
insights not only into the evolution of ungulate behaviour, but also more
generally, into the evolution of the process in individual decision-making
(Isvaran 2005). One such behaviour
is related to breeding, particularly in the context of dominance hierarchy,
factors enforcing changes in the hierarchy, the breeding cycle and maintenance
of healthy populations in captive conditions.
The
present study is an attempt to record dominance hierarchy vis-à-vis different
types of behaviour associated with body conditions and breeding display in a
population of Sambar Deer Rusa unicolormaintained in the State Museum and Zoo, Thrissur in Kerala, and it provides
some basal information that may be needed to evolve strategies to curtail the
exploding population and reduce the cost of maintenance in captivity.
METHODS
The
main study was carried out over a period of four months from June through to
October, 2009. As per the birth
register at the zoo this period records a high incidence of breeding activity
among Sambar. In a population of a
total of 70 Sambars in the enclosure there were 22 males including 16 adult
stags at the commencement of the study.
A
total of six stags were selected for the study under ‘focal animal sampling
technique’. In this technique a
single individual is observed for a specified period of time and all the
instances of different categories of its behaviour are duly recorded (Martin
& Bateson 1993). On the basis
of decreasing order of ‘dominance hierarchy’ three of the Sambars namely H1,
H2 and H3 were in the rut or hard antler stage, and others
namely V1, V2 and V3 were in the later stages
of velvet growth.
The
factors taken into account for ranking the Sambars were the body and antler
size, the ability of a stag to occupy vantage positions during feeding time,
its display leading to the ability to attract a larger number of females,
capacity to aggressively dictate to other stags of the herd, and carry out most
of the breeding activities in the herd.
Data
on behaviour of Sambar which could be linked to the breeding status of the
animal were used to design the ethogram (columns 2 and 3: Table 1). An ‘ethogram’, which is a set of terms
and descriptions of the behaviour of an animal may be comprehensive of all behaviours of a species or it
may be for only one sex, age group or type of behaviour (Lehner 1987). The ethogram presented in this study is
adapted with modifications over Roshin (2005) who conducted a similar study on
Spotted Deer Axis axis.
During
the four months of the main study, Sambars were observed for a total of 318
hours, and each animal received around 53 hours of observation. The observations were carried out from
0600 to 1800 hr to go with the normal activity schedule of the deer as well as
the zoo. The 12-hour study period
was divided into twelve segments of one hour duration each and each animal was
allotted two such segments every week. The stag and the time segment in which the observation was to be taken
were selected randomly. The
animals were observed and every activity of the deer during that particular
one-hour period was recorded in the ethogram.
The
number of times an animal exhibited a particular behaviour during its allotted
one hour was noted. The frequency
of exhibition of each behaviour was allotted a particular score as per the
standard score card presented in Table 1, columns 3 to 6 (adapted and modified
from Roshin 2005). The score was
higher for exhibiting a behaviour directly related to breeding, and the score
allotted was lower for behaviour less related to breeding. To obtain the ‘breeding behaviour score’
for any particular stag the score recorded for each hour of observation and for
each listed behaviour were added up.
The
stags were observed for various changes in the physical condition and the
number of females they led. The
physical changes observed were purely subjective and at no point of the study
were the animals restrained or immobilized as it could have led towards
behavioural aberrations. The
observations were mainly on the shifting of antler stages, size of the stag,
changes in the coat colour, and neck and testicular circumference. The changes seen in the behavioural
score of the stags were correlated to the shifting antler stages. Statistical
analysis was done as described by Snedecor & Cochran (1994).
RESULTS
Observation
of the stags before, during and after the four months study period revealed
that the antlers of the Sambar deer were in velvet growth for a span of 7–8
months. The complete shedding of
the velvet appearance took about 5–6 days.
Stag
H1 maintained a behavioural score of 42±11.73 during the hard antler
phase whereas during the velvet phase it slipped to 9.66±2.25 (Fig. 1). The weeks which show the lowest score
for H1 are between the 7th and 9th weeks of
the study. In this case the antler
was cast off during the 7th week.
The
behavioural score of stag H2 was 42.85±12.58 during the hard antler
stage and it reduced to 12.6±2.3 during the velvet period (Fig. 2). The weeks which show the lowest score
for H2 are between the 8th and 9th weeks. In this case the antler was cast off
during the 8th week.
Stag
H3 had a behavioural score of 44±14 during the rut season; it became
12.6±3.13 during the velvet stage (Fig. 3). The weeks which show the lowest behavioural score for H3are between the 8th and 10th weeks. In this case the antler was casted off
during the 8th week.
The
behavioural score of stag V1 was 23.16±12.84 during the velvet
stage, but as it entered the rut season, its score shot up to 51.81±5.54 (Fig.
4). The weeks which show the
highest score for V1 are between the 7th and 11thweeks. This is equal in duration
as observed for V2, but it onset early. In this case the velvet was shed during the 7th week.
Stag
V2 had a behavioural score of 24.85±13.83 during the velvet phase;
as it shifted to the hard antler stage, the score increased to 51.9±5.38 (Fig.
5). The weeks which show the
highest score for V2 are between the 8th and 12thweeks. This is a longer duration
than that observed for V3. In this
case the velvet was shed during the 8th week.
The
behavioural score of V3 was 30.33±14.76 during the velvet antler
stage, the shift to the rut took the score up to 53.75±4.83 (Fig. 6). The three weeks which show the highest
score for V3 are the 10th, 11th and 12thweeks. In this case the velvet was
shed during the 10th week.
Figures
7 and 8 show the comparison of behavioural scores of the hard antlered and the
velvet antlered groups, respectively. All three Sambars in each group follow a similar trend of behavioural
score, differing, however spatially. The lowest score was reached early by H1 which is the most
dominant in the group (Fig.7). The
peak score is attended early by V1 which is the most dominant in the
group (Fig.8).
The
behavioural scores were very high during the ‘hard antler’ stage for all six
stags in comparison with their own scores during the ‘velvet antler’ period.
Since Sambars are nocturnal in habit, mounting and service could not be
observed more than once, but other activities allied to breeding like chasing
of females, sniffing and Flehmen’s reaction were observed many times. Territorial behaviour, holding the head
high, fighting, spraying urine upon its own body and face were also observed
quite a few times.
The
stags seemed to be in peak size and had the best body condition during the
later stages of velvet growth. The
good body condition was maintained through the initial phases of the rut season
but, during the later stages of rut/ hard antler phase, the stags were seen in
a worn out state. Deteriorated
body condition was observed in those stags whose antlers were freshly cast; the
stags appeared skinny, emaciated, with coat thickness much less and some of
them carrying the gore wounds sustained during tussles for territory, hinds and
rations. The antler regrowth stage
was found to be a recuperating stage during which the stag prepared itself to
face the next rut. The scrotum
showed significant enlargement in the stags approaching the rut season. The coat colour was slightly darker in
shade in the hard antler stages in comparison to those in other stages. The neck musculature was blown up in
size during the rut season.
The
stag H1 possessed the largest ‘harem’ followed by H2 and
H3 with a membership of 17, 13 and seven individuals, respectively,
till they retained the hard antlers. Casting off the antlers brings in a sudden dissolve in the ‘harem’ size
as the members prefer to join any other male that is in rut. An antler cast male or one with a newly
growing antler was observed to be submissive even to the females in the herd on
various occasions.
As
V1, V2 and V3 entered the rut season, V1 formed
the largest harem, followed by V3 and V2 not lagging far
behind. These three stags enjoyed a membership of
19, 14 and 13 individuals, respectively.
DISCUSSION
The
antlers are indicative of the status of breeding activity of the male and are
important in dominancy display. Antler growth cycles are closely related to sexual cycles in stags and
are directly attributable to variations in seasonal photoperiod influencing
gonadal steroidogenic activity. Testosterone levels peak immediately before rut and it is the rapid
decline in its level that causes antler casting. Antler growth occurs at a low testosterone concentration and
is seen increasing when the antler growth nears completion.
The
hard antlers decorate the stags for the whole rut season which lasts for about
four to five months. This is followed by the antler casting stage wherein the
stag may lose its antler often in a fight or by hitting against a tree or a
fence. The stag may lose both the
antlers on the same day or there may be a gap of 2–3 days for the second
one to fall. This stage does not
last long, as antler growth is a rapid continuous cycle, and the initiation of
the next set of antlers would set in without much delay. Velvet shedding and antler hardening is
a consequence of high testosterone levels (Woodbury & Haigh 2007).
Quantified
trends have been observed as behavioural scores in relation to antler stage,
stage after shedding of antlers or transition from velvet to hard-antler
stage. This shows the significance
of antlers in territorial display are linked to breeding.
Findings
in the case of Sambar stag in this study are similar to observations made on
other deer species. Komers et al.
(1997) suggested that dominance rank is the most important factor in
determining the level of reproductive behaviours exhibited. As per Mulley (2007), Fallow Deer bucks
will fight vigorously during the pre rut to establish dominance. Skinner & Harrington (2003) had
supportive observations that in a group of Sika Deer the activities directly
associated with mating were significantly different between the territorial and
non territorial groups. Pereira et
al. (2005) observed that breeding behaviour of male Pampas Deer during rut was
characterized by predominately ano-genital sniffing, flehmen, urine sniffing,
chasing and mounting.
In
this study, good body condition was maintained in the initial phases of the rut
season but, during the later stages of rut/hard antler phase, the stags were
seen in a worn out condition which is indicative of the hardships undergone
during the rut for maintenance of the harem as well as the dominance
quotient. Asher et al. (1987)
reported that Fallow Deer bucks exhibited pronounced live weight gains over
spring and summer months, to reach a peak mean weight and rapid live weight
losses over the rutting period with a minimum mean live weight. Monfort et al. (1993) reported that
antler length, body weight and chest girth were maximal during pre-rut in Eld’s
Deer which was in complete agreement with the findings of the present study.
The
study showed significant enlargement of the scrotum in the stags approaching
the rut season. The stags in the
hard antler stage had much larger testes than those in antler cast or velvet
growth stages. Monfort et al. (1993) observed maximal scrotal circumference and
combined testes volume in mid winter. Georitz et al.(2003) also supported the findings with the claim that all reproductive organs
were highly developed during the rut only. This finding was supported by Haigh
(2007) who stressed that the scrotal circumference increased markedly and
peaked at about the same time of the onset of the rutting season in Wapiti and
Red Deer.
The
coat colour was observed to be slightly darker in shade in hard antler stags in
comparison with those in other stages. The neck musculature was blown up in size during the rut season. Similar
were the findings of Gomez et al.(2006) who claimed that in case of Iberian Red Deer, neck circumference showed
a time course reaching the highest values during the days of decreasing
photoperiod. Blake et al. (2007)
observed the neck muscles thicken during the rut season in the Reindeer also.
In
a population of captive Sambar Deer, males are known to control the group led
by the alpha male which is identified by its good physical appearance, sharp
and long antlers, positioning at vantage points to take the major share of feed
and its mates (Saseendran et al. 2003). Achieving a high social rank may be advantageous for individuals at high
population densities, because dominance status may determine the priority of
access to limited resources and reduce individual loss of body mass. The establishment of dominance
relationships between individuals involves variable levels of aggressiveness
that can be influenced by resource availability (Taillon & Cote 2007).
The
stag H1 at Thrissur Zoo possessed the largest harem followed by H2and H3 with a membership of 17, 13 and 07 individuals
respectively. But the status of
being the leader of the harem continued only till they retained the antlers,
the casting of antlers by these males and the coming to rut of the till then
velvet stags lead to a large dropout in the harem membership of the former
stags who preferred to join the harems of V1, V2 and V3.
Among these stags, V1 owned the largest harem, followed by V3,and V2. The mentioned stags enjoyed a membership
of 19, 14 and 13 individuals respectively.
Fraser
& Broom (1997) avowed that the strongest stags are able to command the
largest ‘harems and enjoy the most copulation which was supportive of the
results of the present study. McElligott et al. (2001) reported that larger mature Fallow bucks have
advantages over other males when competing for mating. Yoccoz et al. (2002) claimed that
prime-aged males are most often the harem holders among Red Deer.
Observations
made by Semiadi et al. (1994) on Rusa unicolor maintained
in captivity at Flock House Agricultural Centre, Bulls, Manawatu, New Zealand,
indicated that although the dominant rutting Sambar stag collected a harem, the
dominant stag displayed a high degree of tolerance toward the presence of other
stags in hard antler within the harem.
Even
though the hormonal and the reproductive cycle follow different patterns in
case of seasonal temperate deer and the non seasonal tropical deer, the
behavioural and the physical observations were quite similar. Only difference was that there were
males in rut throughout the year and births were taking place at any time of
the year unlike the temperate deer which breed only during a particular
season. The adversaries caused by
the overactive deer in rut season in terms of attack on fellow members or the
animal keepers and on road encounters in case of wild deer will be present
throughout the year, only consolation being that not every male deer will be in
rut at the same time unlike the deer from temperate countries.
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EDITORIAL
COMMENTS:
Sambar Rusa
unicolor and the Spotted Deer Axis
axis are two common species of deer maintained in captive
facilities in India. The paper by
Savanth et al. on captive sambar of Thirssur presents two points that are
noteworthy—about the breeding season in Sambar and a suggestion to the
management for maintaining breeding population that ensures sound breeding,
safety of animals and economy in cost of maintenance.
Literature
indicates that breeding by natural and introduced population of Sambar is
widespread through the year, and it is also known in general that in protracted
captive populations the breeding activities may get prolonged. Peak calving in
Sambar in the zoo at Thrissur is June to October, when all behaviour related to
rutting, territorial displays, etc. were also recorded for publication.
Sankar &
Acharya (2004) have reviewed the details about sambar. The peak rutting season of Sambar
occurs between October and December (Lydekker 1916; Schaller 1967). Sankar (1994) reported from Sariska in
Rajasthan of western India that there the Sambars are in peak rut in winter,
when all the stags carried antlers. For Nepalese populations of Sambar, Mishra
(1982) reported peak calving time as close to the monsoon season or June–July. Semiadi et al. (1994)
reported calving by a semi-domesticated herd of Sambar in Manawatu, New Zealand
(40014’S & 175016’E) from January to November, with a
peak in April/May.
In Similipal
Tiger Reserve, Orissa, eastern India, the main breeding season for sambar is
the rainy season, i.e., September–October, and the frequency of sighting
very young fawns is very high from the last week of March to the end of
April. Occasionally, discarded
full-grown embryonic fawns have been seen at abandoned Akhand Shikar camps.
This confirms that peak calving season in Sambar coincides around the time ‘Akhand
Shikaar’ takes place. This type of
shikar is a traditional practice of mass hunting of wild animals by tribal
people in Similipal which the entire district administration gears up to
thwart.
During the breeding season the male Sambar
exhibits lekking and attracts nearby females. Territory concept in Sambar is not
rigid. For aggregation of females ‘harem’ is a loosely used
term. The aggregations dissolve or
change when a particular hierarchical structure changes. During such
transition in hierarchical status male-male fight is common.
These bits of
information, read with information from wild populations confirm that calving
in Sambar, peaks seasonally, but the species mate and reproduce round the
year. Unplanned or unrestricted
breeding of deer, and allowing too many male deer to remain in one enclosure
are likely to increase the cost of maintenance, and create problems of
congestion and intra-specific fights which may be fatal.
The
availability of the choice of more numbers of male deer in a population is one
of the factors for ensuring better progeny. In a population in the wild because
of the process of natural selection and survival of the fittest, maintenance of
a healthy and stable population is a natural order, but in captivity a manager
has to decide the process towards this goal through appropriate selection,
segregation and environment enrichment. Timing of segregation is important and a site-specific knowledge on
breeding behaviour is necessary for the manager. Therefore, research towards ethological records on exhibited
species should always be encouraged.
Mishra,
H. R. (1982). The ecology and behaviour of Chital Axis
axis in the Royal Chitawan National Park, Nepal, with
comparative studies of Hog Deer Axis
porcinus, Sambar Rusa
unicolor and Barking Deer Muntiacus
muntjak. Unpublished PhD Thesis, University of
Edinburgh, Edinburgh, United Kingdom.
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K. (1994). The ecology of three large sympatric
herbivores (chital, sambar and nilgai) with special reference for reserve
management in Sariska Tiger Reserve, Rajasthan. PhD Thesis. University of
Rajasthan, Jaipur.
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K. & B. Acharya (2004). Sambar, pp. 163–170. In: Ungulates
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G.B. (1967). The
Deer and the Tiger: A Study of Wildlife in India. The University of Chicago Press,
Chicago, 370pp.
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R. (1916). Wildlife
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