Inter-group consorting by a free-ranging female rhesus monkey (Macaca mulatta)

The behavior of a free-ranging female rhesus monkey (XJ) who emigrated from her natal group (J) to another (M) for 14 consecutive days is described. Hypotheses as to its function and motivation are considered.     

Copulatory behavior in a free-ranging population of stumptail macaques (Macaca arctoides) in Mexico

This paper presents copulatory data gathered on a free-ranging population of stumptail macaques (Macaca arctoides) in Mexico. The study found evidence for seasonal clumping of matings, with the peak in the month of February, and that matings are more common in the afternoon, when measuring diurnal changes. It also found that males require an average of one and a half mounts before ejaculating, and mating among females is distributed unequally, when the measurement is between those females that mated. Furthermore, male dominance rank and male-female affiliation are both positively correlated with mating frequency. Variations between this study and captive studies are minimal. The variances that do occur may be explained by differences in the research settings or the individual differences in the subjects' behavior across studies.     

Return-benefit spite hypothesis: An explanation for sexual interference in stumptail macaques (Macaca arctoides)

Sexual interference behavior (the phenomenon of intervening with the matings of others) appears selfish in that its primary function seems to be that of improving one's reproductive fitness relative to others. In stumptail macaques (Macaca arctoides), interference may be spiteful, and may contribute to the receipt of a return benefit. This is the focus of this paper. The subjects were 58 stumptail macaques in a single group with seven matrilines. They were free-ranging, habituated to human observation, and lived on the island of Tanaxpillo at Lake Catemaco in southeastern Mexico. During the study, tie durations (the periods where male and female genitalia remain connected following ejaculation) were significantly altered overall, being longer, on average, during matings with sexual interference, opposed to those without interference. When matings occurring in succession were divided in half, ties were significantly longer during the second half than the first half. Also, although the difference was not statistically significant, the average number of mounts required by males to reach ejaculation was greater during matings with interference than without interference. Such apparent social stress may reduce the fertility of the mating pair at some cost to the interferer. Some individuals that interfered also used alternative mating tactics. These matings were 27% of the total, and they received interference less often than normal matings. When alternative matings were interfered with, they received significantly less interference: alternative matings received nearly eight times less interference than normal matings. The average tie duration for alternative matings without interference was also significantly less than the average tie for normal matings with interference. Alternative mating tactics appear to elicit less social stress; this may contribute to increased reproductive fitness for individuals that practice both alternative mating and sexual interference, if the latter produces a return benefit.     

Acoustic detection and acoustic habitat characterisation of the critically endangered white-bellied heron (Ardea insignis) in Bhutan

1. Growing developmental activities, such as hydropower construction, farm roads, and other human activities, are affecting the critically endangered white-bellied heron (WBH). Out of a known global population of 60, 28 individuals inhabit the river basin area and freshwater lakes and ponds of Bhutan. Several constraints impede continuous monitoring of endangered species, such as the isolated and cryptic nature of the species and the remoteness of its habitat; to date, there are no long-term reference data or techniques implemented for continuous monitoring of this species.
2. In this study, we designed acoustic detection and habitat characterisation methods using long-duration recordings from three habitat areas in Bhutan. Acoustic indices were extracted and used to implement a species-specific call detector and to generate habitat soundscape representations. Using WBH calls annotated in month-long recordings from a known site, a novel indices-based detector was implemented and tested. A total of 960 hr of continuous audio recordings from three habitats in Bhutan were analysed.
3. We found that a species call detector implemented using a combination of acoustic indices (that includes measures of spectral and temporal entropy and different angles of spectral ridges) has a correct detection rate of 81%. Additionally, visual inspection of the species’ acoustic habitat using long-duration false-colour spectrograms enabled qualitative assessment of acoustic habitat structure and other dominant acoustic events.
4. This study proposes a combined approach of species acoustic detection and habitat soundscape analysis for holistic acoustic monitoring of endangered species. As a direct outcome of this work, we documented acoustic reference data on the critically endangered WBH from multiple habitat areas and have analysed its temporal vocalisation patterns across sites.