The morphology of female bopyrids is adapted to parasitism, but understanding the function of their thoracic and mouth appendages is hindered by their small size and cryptic lifestyle, limiting detailed examination. This study aimed to clarify the function of the first oostegites and maxillipeds in bopyrid isopods infesting the branchial chamber of caridean shrimp through behavioural observations and morphological examination. We tested whether the movement of these structures was exclusive to ovigerous female parasites during brood ventilation. The results revealed that the beating of the maxillipeds and flapping of the first oostegites were not restricted to ovigerous females. However, the frequency of these movements was significantly higher in ovigerous females than in non-ovigerous females. The frequency of maxilliped beating increased with embryonic development, whereas that of flapping the first oostegites exhibited the opposite trend. Microscopic observation using dye showed that the movements of the maxillipeds and the first oostegites expelled residual dye from the female brood chamber through the dorsal surface or beneath the first oostegites. The dye was then transported by the water current generated by the scaphognathite of the host shrimp. These findings suggest that these structures not only facilitate ventilation but also serve as a grooming mechanism for female parasites, which is critical for embryonic survival. The results of the present study represent the first observation of embryo grooming in bopyrid isopods. This study also provides new information on the functional morphology of bopyrid isopods, which is important for understanding their ecological dynamics and adaptation to parasitism.

Group-living creates stresses that, all else equal, naturally lead to group fragmentation, and hence loss of the benefits that group-living provides. How species that live in large stable groups counteract these forces is not well understood. I use comparative data on grooming networks and cognitive abilities in primates to show that living in large, stable groups has involved a series of structural solutions designed to create chains of ‘friendship’ (friends-of-friends effects), increased investment in bonding behaviours (made possible by dietary adjustments) to ensure that coalitions work effectively, and neuronally expensive cognitive skills of the kind known to underpin social relationships in humans. The first ensures that individuals synchronise their activity cycles; the second allows the stresses created by group-living to be defused; and the third allows a large number of weak ties to be managed. Between them, these create a form of multilevel sociality based on strong versus weak ties similar to that found in human social networks. In primates, these strategies appear successively at quite specific group sizes, suggesting that they are solutions to ‘glass ceilings’ that would otherwise limit the range of group sizes that animals can live in (and hence the habitats they can occupy). This sequence maps closely onto the grades now known to underpin the Social Brain Hypothesis and the fractal pattern that is known to optimise information flow round networks.

The effects of maternal and peer separation during infancy and juvenescence on adolescent and adult chimpanzee behaviour were studied. The aim was to provide an insight into the social development of the species and to investigate human influence on this process. Forty-three adolescent and adult chimpanzees (Pan troglodytes), from a variety of backgrounds, were studied at five zoos in the UK. Details of play and grooming interactions were recorded. Competence at initiating, maintaining and contributing to play and grooming interactions was assessed. It was predicted that, regardless of their present environment, captive chimpanzees that were reared without their mother would be less competent and complex in these social abilities than mother-reared chimpanzees. Results indicated that the chimpanzees' social skills showed few detrimental effects of maternal separation. Nevertheless, individuals that had been human-reared demonstrated more unsuccessful initiations of social interactions and fewer polyadic grooming interactions than their mother-reared peers. Therefore, rearing background may have only a limited effect on adult chimpanzees' social competence. Adult chimpanzees that were hand-reared or nursery-reared may be exhibiting a recovery of their social skills, or they may be unaffected by their rearing background; alternatively, the effects of rearing may have been masked by more significant factors, such as current management.

Previous studies have shown that male mink (Mustela vison) removed from their mothers at seven weeks of age develop more tail-biting than males left with their mothers until six months. Mink in the wild do not damage their own pelts in this way, and such behaviour may well be an indication of chronic stress.

The aim of this experiment was to investigate further the causes of tail-biting by considering female young as well as male, and by lowering the age at which the late-weaned ‘ mink were separated from their mother to 11 weeks, by which age their period of socialization should be complete. This was to generate results of more practical use to farmers, who cannot leave all young with their mothers until six months of age for reasons of space. Mink removed from their mothers at seven or eleven weeks of age did indeed differ in the incidence of tail-biting. Early-weaned ‘females were more likely than late-weaned females to have bitten their tails at six months of age. A similar result was evident as a trend for both sexes at ten months. Furthermore, at this age, some animals ‘ tail tips were completely bald and such animals were all early-weaned.

Where provided with plastic drinker dishes, early-weaned animals were also more likely to chew these. Thus weaning age had long-lasting effects on a number of oral behaviour patterns. These results suggest that young animals predisposed to tail-bite might be diverted by the provision of other objects to chew, and that if problems of over-crowding are avoided, leaving mink kits with their mothers until 11 weeks might improve their welfare.

We studied the distribution of ectoparasite species (an ixodid tick, a chigger mite, 7 mesostigmate mites, 5 fleas and 3 lice) on bodies of 5 species of rodent hosts from the marshlands in Argentina to establish whether arthropod ectoparasites are segregated across body parts of the same host individual. We asked (a) whether an individual ectoparasite species prefers certain parts of the body of its host and, if yes, whether these preferences overlap among ectoparasite species; (b) whether ectoparasite species composition differs among different parts of a host's body; and (c) whether co-occurrences of ectoparasite species within pre-defined body parts of a host are non-random and, if yes, whether ectoparasites co-occur in the same body part of a host either less or more often than expected by chance. It was found that, in general, ectoparasite species were not segregated across body parts of a host. Although some ectoparasites preferred certain body parts, these preferences were similar among ectoparasites belonging to different species and/or higher taxa resulting in similarity among host body parts in ectoparasite species composition. In addition, ectoparasite species demonstrated a tendency to co-occur on the same body parts of a host and not to be segregated among them. It was concluded that the distribution of ectoparasites on the body of a small mammalian host is driven mainly by their interaction with the host rather than by distinct preferences or interactions among ectoparasite species.

Behavioural patterns involved in avoiding, repelling, or removing parasites allow mammalian hosts to defend themselves from an array of parasites that threaten the host's fitness in the natural world. Some examples of behavioural defenses and the presumed target parasites are: grooming to remove ticks, grouping to reduce attack rate of biting flies, fly repelling movements to reduce parasitic flies, and selective grazing to reduce intake of faecal-borne parasites. These behavioural defenses are discussed with regard to effectiveness in controlling the target parasites. Parasites have sometimes evolved behavioural strategies of evading, penetrating or disabling these behavioural defenses. These parasite behavioural strategies, though less studied, are discussed. Also discussed is the possibility that host behavioural patterns that may defend against one parasite may be exploited by a different type of parasite to facilitate its own transmission. The interplay between host defensive strategies, the cost versus the effectiveness of such strategies, and a parasite's evasion or exploitation of such strategies, may be useful in understanding some aspects of host-parasite dynamics in nature.

Evidence suggests that behavioural defences, such as habitat selection and grooming behaviour, have evolved in animals in response to the costs associated with ectoparasites. Bat fly and mite densities were compared among wild-caught bats in Belize with different roosting preferences (cavity, foliage, or both), and grooming behaviour was analysed for bat species with high and low ectoparasite density. Ectoparasites of bats were removed using forceps, and bat grooming behaviour was recorded with a camcorder. Because bat flies pupate on the surface of host roosts, bats that use cavity roosts (a sheltered environment for the pupae) were predicted to have higher densities of bat flies than those that use foliage (exposed environment). Cavity-roosting species generally had higher densities of bat flies and mites, although the relationship was more evident for bat flies. The grooming behaviour of bats was predicted to differ among species with high or low ectoparasite densities. Although there was no difference in the frequency of grooming behaviours for individuals with and without bat flies, there were differences in grooming behaviour at the species level. Bat species with high ectoparasite densities scratched more than those with low ectoparasite densities. These results suggest that ectoparasite densities and grooming behaviour are related to roosting preferences in bats.

Amblyomma hebraeum differs from many ixodid tick species in that it is not susceptible to the direct effects of the host immune response. All stages of the life cycle are able to feed repeatedly on laboratory hosts and show no progressive declines in engorged weight. However, on cattle there are declines in the yield of engorged adult females over time, as animals become sensitized to the tick and grooming increases. In the field zebu, Bos indicus and sanga, B. indicus x B. taurus breeds of cattle become less heavily infested than B. taurus breeds. The apparent resistance of zebu and sanga breeds is the result of learned tick avoidance behaviour, skin sensitivity and the ability to dislodge ticks prior to attachment as well as grooming ability. Among other Amblyomma spp., the feeding of A. americanum is adversely affected by acquired host immunity, while that of A. variegatum is generally unaffected.