Leaf-pile pulling: an unusual play pattern in wild chimpanzees

Play in nonhuman animals has generally been viewed as being uniform among study sites. No studies have examined whether there are local variations in play. In this work we report an apparently locality-specific form of play that is basically solo locomotor play, but also has aspects of object play and social play. We describe this unusual "leaf-pile pulling" (LPL) pattern based on video footage of the chimpanzees of Mahale, Tanzania. Typically, when a party of chimpanzees moves in a procession down a slope in the dry season, a youngster will turn around and walk backward while raking many dry leaves with both hands. This activity accumulates many dry leaves while producing a lot of sound. After the player walks 1-15 m, he/she either turns around and walks forward or moves in a somersaulting fashion. The performer usually faces an individual that is immediately following him/her in the procession. The age of the performers ranges from 2 to 22 years, but 3-10 years are most typical. Compared to younger (< 8 years) individuals, older (> or = 8 years) individuals tend to cover longer distances during play, and to be more likely to play only on sloped surfaces and during travel. One of the authors (W.W.) has only seen the behavior exhibited by five different individuals on 10-15 occasions at Gombe. The behavior is exhibited less often at Gombe than at Mahale. To date, LPL has not been reported elsewhere. The absence of LPL at other sites may or may not be explained by environmental differences, such as differences in the availability of dead leaves and sloped terrain. Although the possibility that LPL is acquired by individual learning cannot be completely ruled out, the hypothesis that it is a tradition of the Mahale study group is more likely. This suggests that play may warrant more careful consideration in studies of nonhuman primate culture.     

Polymerase chain reaction detection of Clostridium perfringens in feces from captive and wild chimpanzees, Pan troglodytes

Background For veterinary management of non‐human primates in captivity, and conservation of wild‐living primates, management of their health risks is necessary. Incidences of pathogenic bacteria in the fecal specimens are considered as one of the useful indicators for non‐invasive health monitoring. Methods We carried out the detection of Clostridium perfringens in feces from captive and wild chimpanzees by the rapid polymerase chain reaction method. Results The bacterium was detected in most fecal specimens (80%) in captive chimpanzees. Contrarily, the detection rate in the wild chimpanzees was low, with 23% (n = 12) of 53 fecal samples from the Bossou group, Guinea, and 1.2% (1/81) in the Mahale group, Tanzania. Conclusions These results show that the intestinal microflora differs between Pan populations under various living conditions, being influenced by their diet and environment.     

Male sperm donation consequences in single and double matings in Anisopteromalus calandrae

Abstract. The number of spermatozoa that a male transfers to the female during copulation is a main component of its individual fitness, especially under the pressure of sperm competition. This paper presents experimental results on the direct relationship between the male's sperm investment and its paternity in the offspring of dual-mated females. An eye colour mutant (red-eyed) is used to study the differences in the mating and fertilization abilities of males through observation of single and dual matings of females in Anisopteromalus calandrae (Hymenoptera, Chalcidoidea, Pteromalidae). Experimentally, females accept dual matings only in the simultaneous presence of two males. Counts of spermatozoa in the seminal vesicles of virgin males show that red-eyed males have more sperm than wild-eyed ones (approximately 1.46-fold greater). Red- and wild-eyed males do not differ in their mating behaviour and females mate indifferently with both phenotypes. Compared with once-mated females, double-mated females increase neither sperm storage nor lifetime fecundity, and the offspring sex ratio is female-biased. Females mated with two males of different phenotypes produce offspring of both phenotypes throughout their reproductive life, whatever the order of males in the copulation sequence. Any mating pattern appears to produce more red- than wild-eyed offspring (between 1.45- and 1.88-fold greater). Thus, proportions of offspring of each male match the proportions of their sperm potential. With no preference of female for red-eye or wild-eye males being demonstrated at either behavioural or physiological levels, a male's investment in sperm quantity appears to determine its individual reproductive success, at least in these experimental conditions.     

Sexual conflict and sexual selection: lost in the chase

The emergent field of evolutionary biology that studies disparities between the evolutionary interests of alleles expressed in the two sexes, or sexual conflict, promises to offer novel insights into male-female coevolution and speciation. Our theoretical understanding of basic concepts is, however, still incomplete. In a recent perspective paper, Pizzari and Snook provided a framework for understanding sexually antagonistic coevolution and for distinguishing this process from other models of male-female coevolution and suggested an experimental protocol to test for sexually antagonistic coevolution. Here, I show that the framework is flawed, primarily because it is built upon the mistaken assumption that male and female fitness can evolve independently. Further, while the empirical strategy advocated has indeed offered important insights in the past, it does not allow unambiguous discrimination between competing hypotheses.     

Bigger testes increase paternity in a simultaneous hermaphrodite,independently of the sperm competition level

Hermaphroditic animals face the fundamental evolutionary optimization problem of allocating their resources to their male vs. female reproductive function (e.g. testes and sperm vs. ovaries and eggs), and this optimal sex allocation can be affected by both pre‐ and post‐copulatory sexual selection. For example, local sperm competition (LSC) – the competition between related sperm for the fertilization of a partner's ova – occurs in small mating groups and can favour a female‐biased sex allocation, because, under LSC, investment into sperm production is predicted to show diminishing fitness returns. Here, we test whether higher testis investment increases an individual's paternity success under sperm competition, and whether the strength of this effect diminishes when LSC is stronger, as predicted by sex allocation theory. We created two subsets of individuals of the simultaneously hermaphroditic flatworm Macrostomum lignano – by sampling worms from either the highest or lowest quartile of the testis investment distribution – and estimated their paternity success in group sizes of either three (strong LSC) or eight individuals (weak LSC). Specifically, using transgenic focal individuals expressing a dominant green‐fluorescent protein marker, we showed that worms with high testis investment sired 22% more offspring relative to those with low investment, corroborating previous findings in M. lignano and other species. However, the strength of this effect was not significantly modulated by the experienced group size, contrasting theoretical expectations of more strongly diminishing fitness returns under strong LSC. We discuss the possible implications for the evolutionary maintenance of hermaphroditism in M. lignano.     

Temperature affects male and female potential reproductive rates differently in the sex-role reversed pipefish, Syngnathus typhle

The differences in potential reproductive rate between the sexescan be used to predict the operational sex ratio and the patternsand intensity of mating competition and hence sexual selectionin a population. This article describes how one environmentalcomponent, temperature, affects potential reproductive ratesof the two sexes in the paternally brooding, sex-role reversedpipefish (Syngnathus typhle). Males brooded embryos much longer(on average 58 days) in cold water (about 10°C) than inwarmer water (35 days at about 15°C). As a consequence,the potential reproductive rate (number of eggs brooded perday) of males was significantly higher in warm water. In females,however, potential reproductive rate, i.e., number of eggs producedper day given an unlimited access to mates, was not significantlydifferent between temperatures. In both sexes, potential reproductiverate was positively related to body size. At both temperatures,females had the potential to reproduce faster than males. Asa result, the operational sex ratio will become female biasedand sex-roles reversed, as is the case in this species. Sincetemperature differently influenced the potential reproductiverates of males and females, with the sexual difference largerat lower temperatures, more intense female-female competitionis predicted at low temperatures.     

Female polyandry and size‐assortative mating in isolated local populations of the Japanese common toad Bufo japonicus

In anurans, female polyandry under male harassment is distributed across taxa because of external aquatic fertilization. According to the sexual selection theory, male–male competition for access to females is affected by the operational sex ratio (OSR) and population density. The Japanese common toad, Bufo japonicus, is widespread in mainland Japan, and like the European common toad, B. bufo, it engages in explosive breeding. In this study, we observed the breeding behaviour of B. japonicus in isolated local populations for over four years in two breeding ponds with different population sizes and densities: large‐low (L‐pond) and small‐high (S‐pond). We analysed the relative polyandry ratio in egg clutches laid by females and estimated the size‐assortative mating pattern to be an indicator of male–male competition in the two ponds. Both ponds tended to exhibit a size‐assortative mating pattern; however, the frequency of polyandry was different in the two ponds (L‐pond = 20% and S‐pond = 90%). Our results showed that polyandry could occur without multiple amplexus with a high population density, i.e. eggs were often fertilized by free‐swimming sperm in the small shallow pond. We propose that high female polyandry ratios without continuous male harassment are generated because of a male‐biased OSR and a high population density in the small pond. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 236–242.