Basic HTML Version
S A V A C O N S E R V A T I O N
P A G E 1 3
V O L U M E 2 , I S S U E 1
Territorial Scent Marking in Wild Silky Sifakas
Continued
range perimeter and core areas (Heymann 2000; Ferrer et al. 2011). Moreover, recent improvements in GPS
technology offer more precise mapping of the spatial location of scent marks in rain forest habitats.
For those reasons, I conducted a 5 ½ month study of silky sifaka scent marking between July 13 and December 25
2012. The study was conducted in Marojejy National Park with our main silky sifaka study group at Camp 2 which at
the time was composed of six individuals: one adult male (LV), two
adult females (AF,BP), one subadult male (MB), one juvenile male
(WM), and one infant female (MS). Methods followed recent related
research in tamarins (Ferrer et al 2011). Two hour focal animal
sampling sessions were conducted all day on a single randomly chosen
individual. Data books were not used. Rather, all data was coded
directly into powerful handheld GPS units (Garmin GPSMAP 62s) and
immediately geo-referenced as waypoints. Location points were taken
instantaneously every 10 minutes in addition to points collected for all
scent mark types by the focal, the presence or absence of
accompanying urine, and the start/end of each focal session. GPS error
was generally between 5m and 10m which is quite good considering the
mountainous rainforest habitat. This group of silky sifakas exhibits a
greater elevational range (700m asl to 1100m asl) within their home
range than any other
Propithecus
group in Madagascar! All points with
more than 15m of error were excluded from spatial analyses.
Because we have been studying this well habituated group since
2001, a tremendous amount of data was collected efficiently by myself
and two research assistants. In total, 1549 scent marks were recorded
during 1390 focal hours. More than 8000 range points were collected
as well. The number of scent marks recorded in this study and the
number of focal hours exceeds that of most primate scent marking
studies. The majority of all marks were deposited by the adult male,
specifically: 52.4% by adult male LV, 14.9% by sudadult MB, 12.5% by
adult female AF, 9.2% by adult female BP, 8.7% by juvenile male WM,
and 2.3% by infant female MS. Urine accompanied 58% of all scent
marks. As expected, males were found to scent mark in three major
ways (chest marking, genital marking and combined chest-genital marking which is immediately preceded by bark-
biting) while females exclusively genital marked and never engaged in bark-biting. For the adult male, combined chest
-genital marking accounted for 40.1% of his scent marks, followed by genital marks at 35.3% and chest marks at
24.6%. Diademed sifaka males also mark most using combined chest-genital marking preceded by bark-biting (Irwin
2006). The mean focal scent mark rate for adult silky sifakas in this study was 1.64 marks per hour. The mean adult
male mark rate (3.6 marks/hr.) was more than 5 times higher than the adult females (.7 marks/hr.). Silky sifaka mark
rates are therefore much higher than Milne-Edwards’ sifakas (males: .57 marks/hr. and females: .27 marks/hr.) but
still lower than Verreaux’s sifakas (males: 6.9 marks/hr. and females: 4.2 marks/hr.) (Mertl 1979; Pochron et al. 2005).
The main goal of this study was to test the territorial function of silky sifaka scent marking. To fulfill such a
function, silky sifaka scent marks should be selectively deposited along the periphery of their home range. To test this
question, a variety of spatial analyses were conducted using the ExpertGPS and Garmin Basecamp software packages
as well as Google Earth to confirm certain points. First, the 100% minimum convex polygon (MCP) home range was
determined (as 46 hectares) using all range and scent mark GPS points. Secondly, a 25m x 25m grid was overlaid on
the home range and territory “periphery” and “core” cells were determined. All territory periphery cells were within
three cells or 75m of the 100% MCP line. Finally, the number of scent marks and range points per cell was counted.
Following Heymann (2000), expected values of scent marking in core and periphery cells were calculated based upon
the size of these zones and the intensity of use based upon the number of instantaneous range points collected. It
was important to control for both area and intensity of space use since 34.6% of the home range area was included in
the periphery but only 24.6% of range points occurred in the periphery. The
G
test with Yates’ correction was used to
compare observed and expected distributions.
Silky sifaka adult scent marks in relation to 100% MCP hom-
erange (46 ha) between July 13 and December 25 2012.
Top: 318 scent marks by two adult females. Bottom: 725
scent marks by one adult male.