The cost of living in larger primate groups includes higher fly densities

Flies are implicated in carrying and mechanically transmitting many primate pathogens. We investigated how fly associations vary across six monkey species (Cercopithecus ascanius, Cercopithecus mitis, Colobus guereza, Lophocebus albigena, Papio anubis, and Piliocolobus tephrosceles) and whether monkey group size impacts fly densities. Fly densities were generally higher inside groups than outside them, and considering data from these primate species together revealed that larger groups harbored more flies. Within species, this pattern was strongest for colobine monkeys, and we speculate this might be due to their smaller home ranges, suggesting that movement patterns may influence fly-primate associations. Fly associations increase with group sizes and may thus represent a cost to sociality.

Energetic and physical limitations on the breaching performance of large whales

The considerable power needed for large whales to leap out of the water may represent the single most expensive burst maneuver found in nature. However, the mechanics and energetic costs associated with the breaching behaviors of large whales remain poorly understood. In this study we deployed whale-borne tags to measure the kinematics of breaching to test the hypothesis that these spectacular aerial displays are metabolically expensive. We found that breaching whales use variable underwater trajectories, and that high-emergence breaches are faster and require more energy than predatory lunges. The most expensive breaches approach the upper limits of vertebrate muscle performance, and the energetic cost of breaching is high enough that repeated breaching events may serve as honest signaling of body condition. Furthermore, the confluence of muscle contractile properties, hydrodynamics, and the high speeds required likely impose an upper limit to the body size and effectiveness of breaching whales.

Mammals repel mosquitoes with their tails

The swinging of a mammal's tail has long been thought to deter biting insects, which, in cows, can drain up to 0.3 liters of blood per day. How effective is a mammal's tail at repelling insects? In this combined experimental and theoretical study, we filmed horses, zebras, elephants, giraffes and dogs swinging their tails. The tail swings at triple the frequency of a gravity-driven pendulum, and requires 27 times more power input. Tails can also be used like a whip to directly strike at insects. This whip-like effect requires substantial torques from the base of the tail on the order of 101–102 N m, comparable to the torque of a sedan, but still within the physical limits of the mammal. Based on our findings, we designed and built a mammal tail simulator to simulate the swinging of the tail. The simulator generates mild breezes of 1 m s–1, comparable to a mosquito's flight speed, and sufficient to deter up to 50% of mosquitoes from landing. This study may help us determine new mosquito-repelling strategies that do not depend on chemicals.

Host mating system and coevolutionary dynamics shape the evolution of parasite avoidance in Caenorhabditis elegans host populations

Hosts exhibit a variety of defence mechanisms against parasites, including avoidance. Both host–parasite coevolutionary dynamics and the host mating system can alter the evolutionary trajectories of populations. Does the nature of host–parasite interactions and the host mating system affect the mechanisms that evolve to confer host defence? In a previous experimental evolution study, mixed mating and obligately outcrossing Caenorhabditis elegans host populations adapted to either coevolving or static Serratia marcescens parasite populations. Here, we assessed parasite avoidance as a mechanism underlying host adaptation. We measured host feeding preference for the coevolved and static parasites vs preference for Escherichia coli, to assess the evolution of avoidance behaviour within our experiment. We found that mixed mating host populations evolved a preference for E. coli relative to the static parasite strain; therefore, the hosts evolved parasite avoidance as a defence. However, mixed mating hosts did not exhibit E. coli preference when exposed to coevolved parasites, so avoidance cannot account for host adaptation to coevolving parasites. Further, the obligately outcrossing host populations did not exhibit parasite avoidance in the presence of either static or coevolved parasites. Therefore, both the nature of host–parasite interactions and the host mating system shaped the evolution of host defence.

Conservation Medicine: A Solution-Based Approach for Saving Nonhuman Primates

Challenges that threaten the long-term survival of nonhuman primates (NHP) include habitat fragmentation, hunting, and increasingly, infectious diseases. In addition to direct mortality from noninfectious diseases (e.g., hunting) and infectious diseases (e.g., Ebola), human-driven alterations of environments that support NHP often contribute to a decline in population viability. This decline is frequently the result of physiological stress, poor reproduction, decreased immunity, and exposure to novel pathogens. To better understand the diseases that threaten NHP populations, a conservation medicine approach—the application of medicine to augment the conservation of wildlife and ecosystems—is imperative so that we may provide management solutions to help ensure the long-term survival of NHP. Additionally, it is crucial that we gain a better understanding of pathogens at the interface of nonhuman and human primates since the zoonotic potential may create conservation challenges, or alternatively may provide the impetus for conservation actions to be practiced (e.g., minimize bushmeat trade).

An overview of parasite-induced behavioral alterations – and some lessons from bats

An animal with a parasite is not likely to behave like a similar animal without that parasite. This is a simple enough concept, one that is now widely recognized as true, but if we move beyond that statement, the light that it casts on behavior fades quickly: the world of parasites, hosts and behavior is shadowy, and boundaries are ill-defined. For instance, at first glance, the growing list of altered behaviors tells us very little about how those alterations happen, much less how they evolved. Some cases of parasite-induced behavioral change are truly manipulative, with the parasite standing to benefit from the changed behavior. In other cases, the altered behavior has an almost curative, if not prophylactic, effect; in those cases, the host benefits. This paper will provide an overview of the conflicting (and coinciding) demands on parasite and host, using examples from a wide range of taxa and posing questions for the future. In particular, what does the larger world of animal behavior tell us about how to go about seeking insights – or at least, what not to do? By asking questions about the sensory–perceptual world of hosts, we can identify those associations that hold the greatest promise for neuroethological studies of parasite-induced behavioral alterations, and those studies can, in turn, help guide our understanding of how parasite-induced alterations evolved, and how they are maintained.

Genetic, individual, and group facilitation of disease resistance in insect societies

In this review, we provide a current reference on disease resistance in insect societies. We start with the genetics of immunity in the context of behavioral and physiological processes and scale up levels of biological organization until we reach populations. A significant component of this review focuses on Apis mellifera and its role as a model system for studies on social immunity. We additionally review the models that have been applied to disease transmission in social insects and elucidate areas for future study in the field of social immunity.

A comparative study of leukocyte counts and disease risk in primates

Little is known about how the risk of disease varies across species and its consequences for host defenses, including the immune system. I obtained mean values of basal white blood cells (WBC) from 100 species of primates to quantify disease risk, based on the assumption that higher baseline WBC counts will be found in species that experience greater risk of acquiring infectious disease. These data were used to investigate four hypotheses: disease risk is expected to increase with (1) group size and population density; (2) greater contact with soil-borne pathogens during terrestrial locomotion; (3) a slow life history; and (4) increased mating promiscuity. After controlling for phylogeny, WBC counts increased with female mating promiscuity, as reflected in discrete categories of partner number, relative testes mass, and estrous duration. By comparison, the social, ecological, and life-history hypotheses were unsupported in comparative tests. In terms of confounding variables, some WBC types were associated with body mass or activity period, but these variables could not account for the association with mating promiscuity. Several factors may explain why hypotheses involving social, ecological, and life-history factors went unsupported in these tests, including the role of behavioral counterstrategies to disease, restrictions on female choice of mating partners, and the effect of transmission mode on parasite strategies and host defenses.

Red howling monkey use of specific defecation sites as a parasite avoidance strategy

Red howling monkeys, Alouatta seniculusin the central Amazonian basin move to specific sites before defecating. Differences in the vegetation profile of behavioural sites, defecation sites and random sites within the ranging area of howler groups were examined. The defecation sites used differed in the number of leaf intercepts at the levels of the forest the monkeys used for foraging and travelling. Defecating in areas free of underlying vegetation decreases the likelihood of contaminating potential food sources or arboreal pathways. This defecation behaviour may be an important parasite avoidance strategy of red howling monkeys.

Intestinal parasites of sympatric gorillas and chimpanzees in the Lopé Reserve, Gabon

A coprological survey of intestinal parasites of wild chimpanzees (Pan t. troglodytes) and western lowland gorillas (Gorilla g. gorilla) was carried out in the Lopé Reserve in central Gabon. Most samples (69%) were positive but the prevalence of intestinal parasites in the 61 gorilla samples (84%) was higher than in the 66 chimpanzee samples (56%). At least 11 species of parasite were observed: six protozoan, one trematode and at least four nematodes. Six of the species were found in gorillas and chimpanzees but the remainder only occurred in chimpanzees. All but one parasite occurred at low prevalences. Entodiniomorph ciliates, which occurred frequently in both ape species (particularly in gorillas) in the Lopé survey and in all previous coprological surveys of wild apes, may be symbionts involved in cellulose digestion. The dietary and behavioural strategies of wild primates that serve to reduce infection by pathogenic parasites are reviewed.