Reproductive seasonality in wild northern pig-tailed macaques (Macaca leonina).

Macaque reproductive patterns range from strictly seasonal breeding to non-seasonal breeding, but factors explaining this variation are not fully understood. Valid reproductive seasonality data are also still lacking for many wild macaque populations because the majority of birth data are from captive animals living outside of their geographic range. We evaluated whether the reproductive seasonality of wild northern pig-tailed macaques falls as expected by the ecological (latitude) or phylogenetic inertia hypotheses in comparison with other macaque species. We recorded monthly occurrences of births (N = 22), copulations (N = 563), and females exhibiting sex skin swellings (N = 18) in one group at Khao Yai National Park (KYNP), Thailand. Births, copulations, and females exhibiting sex skin swellings were significantly different from a random distribution. Using measures of circular statistics and the van Schaik and colleagues' (Schaik et al. Lee (ed), Comparative primate socioecology, Cambridge University Press, Cambridge, 1999) seasonality categorizations, the population at KYNP is best characterized as moderately seasonal breeding. Despite some inconsistency, macaque reproductive seasonality was significantly influenced by latitudinal location. We broadly found that: (1) non-seasonal breeding macaque populations (birth r-vector < 0.3) lived at latitudes close to the equator between 1°S and 3°N, (2) moderately seasonal breeding macaque populations (0.3 < birth r-vector < 0.7) were found between 3°N and 14°N and at 5°S, and (3) strictly seasonal breeding macaque populations (birth r-vector > 0.7) ranged ≥ 12°N. A strong phylogenetic signal in reproductive seasonality on the macaque phylogeny was also detected. However, further studies of wild macaque populations are still needed to better characterize reproductive seasonality in this taxon.

Extractive foraging of toxic caterpillars in wild northern pig-tailed macaques (Macaca leonina).

Extractive foraging in nonhuman primates may involve different levels of technical complexity in terms of the number of actions that must be performed and the manual dexterity involved. We describe the extractive foraging of caterpillars in wild northern pig-tailed macaques (Macaca leonina) at Khao Yai National Park, Thailand. The study group, observed from May to December 2016 (n = 146 days), comprised 60-70 habituated individuals, including 3-4 adult males, 20-23 adult females, and 36-47 immatures. Four adult males and five adult females, observed from September to November 2016 for a total of 24 days, were selected for focal animal sampling. Northern pig-tailed macaques were observed eating at least two families (Erebidae and Limacodidae) and three genera (Macrobrochis sp., Phlossa sp. and Scopelodes sp.) of caterpillars. While the monkeys ate short and small caterpillars with stinging setae and non-setae caterpillars without processing, they performed extensive caterpillar-rubbing behavior on large and long caterpillars with stinging setae. Based on 61 extractive foraging bouts, we found that caterpillar rubbing was hierarchically organized into five stages and 12 elements. Five stages of behavior sequence started with picking the caterpillar up, transporting it to a substrate, rubbing it to remove stinging setae, ingesting it, and then cleaning hands and mouth. Only adult macaques were observed using a leaf to rub stinging caterpillars.