Behavioural Correlates of Lemur Scent-Marking in Wild Diademed Sifakas (Propithecus diadema) in the Maromizaha Forest (Madagascar)

Abstract

Scent-marking through odours from excreta and glandular secretions is widespread in mammals. Among primates, diurnal group-living lemurs show different deployment modalities as part of their strategy to increase signal detection. We studied the diademed sifaka (Propithecus diadema) in the Maromizaha New Protected Area, Eastern Madagascar. We tested whether the scent-marking deposition occurred using a sequential rubbing of different body parts. We also tested if glands (i.e., deposition of glandular secretions) were more frequently rubbed than genital orifices (i.e., deposition of excreta) by comparing different kinds of rubbing behaviour. We then investigated if the depositor's rank and sex affected the sequence of rubbing behaviour, the height at which the scent-marking happened, and the tree part targeted. We found that glandular secretions were often deposited with urine, especially in dominant individuals. The probability of anogenital and chest marking was highest, but chest rubbing most frequently occurred in dominant males. Markings were deposited at similar heights across age and sex, and tree trunks were the most used substrate. Males exhibited long and more complex scent-marking sequences than females. Our results indirectly support the idea that diademed sifakas deploy a sex-dimorphic mixture of glandular secretions and excreta to increase the probability of signal detection by conspecifics.

Keywords: lemurs; olfactory communication; scent mixing; scent odour; sex-specific pattern.

Figure 1

Patterns of singular and sequential bouts characterizing the deposition of scent-marks in diademed sifakas. Behavioural components of the scent-marking events are represented as (A) sniffing, (B) tooth marking, (C) chest marking/rubbing, (D) anogenital marking/rubbing and (E) urine and/or faeces marking.

Figure 2

Boxplots showing the occurrence rate (per hour) of the scent-marking (SM) bouts in adult males (a–d) and females (e–h). We present here the patterns of singular (dark green) and sequential (purple) bouts in male (a,b) and females (e,f) and that of scent gland secretions (sequential bout) deposited in sequence with urine (light green) and faeces (grey) both in male (c,d) and female (g,h) depositors. Data of dominant (red) and subordinate (turquoise-green) individuals are pooled in (a,c for males; e,g for females). Three stars indicate statistical results with p-value < 0.001, and n.s. designates non-significant results with p-values > 0.05. Whiskers indicate 5th/95th percentiles, the horizontal line is the median, the box delineates the 25th/75th percentiles, and the open circles indicate outliers.

Figure 3

Plots highlighting the patterns of the occurrence frequency/probability of each sequence of scent-marking behaviour (MU: urine marking, MF: faeces marking, TM: tooth marking, GM: anogenital marking, CM: chest/sternal marking) within females’ (a) and males’ (b) scent-marking events and the effect of social rank on males’ glandular scent-marking act occurrence frequency (sternal and anogenital marking) (c). Colors denote particular scent-marking behaviors shown during the marking sequence. Whiskers indicate 5th/95th percentiles, the horizontal line is the median, the box delineates the 25th/75th percentiles, and the black dots indicate outliers. DOM: dominant depositor, SUB: subordinate individuals.

Figure 4

Flow diagrams showing the probability of succession between each behavioural sequence within a scent-marking event. Reported are the transition patterns of dominant (a) and subordinate males’ marking (b) and overmarking (respectively (c) and (d)), that of dominant (e) and subordinate females’ marking (f), as well as young males’ (g) and females’ (h) marking deposition. The coloured geometric shapes highlight a different group of behaviours: shared olfactory elements/sequences are represented by grey hexagons (MU: urine, MF: faeces, GM: anogenital markings); sex-specific sequences (both olfactory and non-olfactory elements) are highlighted by blue pentagons (CM: chest marking and TM: Tooth marking); the investigatory sniffing behaviour (non-olfactory element) is highlighted in pink ellipses (SNIFF). The numbers (in percent) beside each transition represent the probability of transitions between behaviours. The thick black arrows highlight statistically significant transitions (p < 0.05), and thin black arrows indicate non-significant transitions (p > 0.05); OVM: overmarking, M: marking; N: number of total transitions included.