The breeding of palm cockatoos Probosciger aterrimus was studied for 3 years from July 1999 to February 2002 in and around Iron Range National Park, Cape York Peninsula, Australia. Palm cockatoos were weakly seasonal breeders, with the peak of egg-laying occurring in September; 41 breeding attempts were monitored at 28 nesting hollows. Nearly all (27/28) nests were in tropical savanna woodland and an average distance of 320 m to rainforest. Males defended about four nest sites, only a subset of which were used for breeding. The typical active nest tree was in a near-vertical hollow with an opening that faced skywards; 62.1% of active nests were in living trees and the most common species of nest tree was Eucalyptus tetrodonta (48.3%). DNA fingerprinting revealed that some pairs reused the same nest hollow even when breeding attempts were separated by 1 or more years of no breeding activity, but that changes in hollow ownership also occurred. Nest usurpation, male territorial displays at the nest and evidence of interference competition by conspecifics suggest strong competition for nest sites, which is probably driven by variation in hollow quality and high investment in the nesting platform. Of active nests, 81% failed to produce a fledgling, thereby ranking the breeding success of palm cockatoos among the lowest reported for any species of parrot. They also invariably laid a single egg and seemed to breed infrequently, and thus they use an extremely slow life-history strategy. We suggest that this slow life history makes palm cockatoos on Cape York Peninsula sensitive to environmental perturbations, with fire being the most probable threatening process.

In sexually dimorphic ungulates, male reproductive success depends on fighting with other males for access to females during a brief rutting season. Large body size is necessary for success in intrasexual competition, and a few large-sized males are often able to monopolize access to female groups. Earlier studies have reported that reproductive effort increases with age until prime-age is reached, and one study that population density lowered effort in (older) males. No study has directly assessed whether there is within-age-class variation in effort resulting from varying levels of intra-male competition. It is reported here the weight loss during the rutting season of 54 individual male reindeer Rangifer tarandus coming from eight herds with varying density (3.3–6.0 deer/km2) and sex ratio (4–28% males). In agreement with earlier studies, reproductive effort was lower for young (1- to 2-year-old) than for prime-aged (3- to 5-year-old) males both on an absolute and relative scale. Among 1-year-old males (n=33), effort was lower as sex ratio became closer to even, but density during the rutting season had no effect. This suggests that yearling males take a more active role when prime-aged males are absent. In addition to the insight into male ungulate life history, understanding male rutting behaviour may also have implications for population dynamics.

The marsupial brushtailed phascogale Phascogale tapoatafa is a solitary, hollow-dependent, arboreal insectivore that occurs at low densities in open forests and woodlands of Australia. Data gathered from nest box surveys (4 years), and from radio-tracking phascogales to nest sites (3 years) in south-western Australia confirm solitary nesting after dispersal. However, in the winter of a single year, nest box surveys in one study area showed that 56% of individuals were nest sharing. On a neighbouring site, 81 group nests were also recorded among 18 radio-collared individuals. In both areas, groups comprised two to four individuals of any age/sex combination. The same phascogales tended to nest together and in a number of different sites. Nest sharing between females was restricted to territory boundaries and continued after the annual die-off of the males. Nest sharing coincided with prolonged drought conditions and in this year mature phascogales were significantly smaller than normal, i.e. males 25% less in weight, females 12% less. Communal nesting seemed to be a response to thermoregulatory difficulties posed by the three interrelated factors of low body mass, declining temperatures and declining food availability. Nest sharing in this species appeared to be a behavioural indicator of an energetics crisis, there was a population decline during the drought period and a population crash in the following year.

The social behaviour of symbiotic organisms is influenced by the density and distribution pattern of hosts. Herein we examined the host-use behaviour of the anemone-dwelling crab Allopetrolisthes spinifrons (Porcellanidae) in which adults usually live as solitary individuals on their hosts. Adults of this crab use two different sea anemone species, one intermediate-sized species that can be found at relatively high densities in the intertidal zone and another large one that occurs at significantly lower densities in the shallow subtidal zone along exposed rocky shores of the south-east Pacific. Mark–recapture experiments demonstrated that crabs in subtidal waters (low abundance of hosts) remained for long time periods on the same hosts while crabs in the intertidal environment (high abundance of hosts) frequently changed hosts. There were no differences in host fidelity between male and female crabs. In an immigration experiment in the intertidal zone, significantly more juveniles immigrated than had been present originally, indicating that host-use behaviour is age dependent. The sex ratio between resident and immigrated individuals did not change. In an additional experiment hosts were planted at two different densities (high and low) both in the shallow subtidal and the intertidal zone to test whether host fidelity of crabs depends on distance between hosts. At the subtidal site, about half the crabs remained on their sea anemones for 14 days while at the intertidal site most crabs disappeared within 1 day in both density treatments. At both sites crabs were seen changing hosts in high density treatments, but no such events could be witnessed at low densities of hosts. Although the results are not fully conclusive, they suggest that host movements are affected by host densities. This relationship may be mediated by host (anemone species, size, distance) and site-specific (predation pressure, exposure time) factors. In general, the present study indicates that host characteristics influence host fidelity of symbiotic organisms and thereby, their social behaviour.

Bentholyonsia teramachii has hitherto been described from Japan, but a conspecific specimen is herein recorded from Western Australian shelf waters at a depth of ∼100 m. Hitherto placed in the Lyonsiidae, B. teramachii is herein relocated in the Lyonsiellidae, alongside a second genus – Lyonsiella. Features of the anatomy of Bentholyonsiateramachii, including highly sensory siphons, reduced ctenidia unable to collect and transport particulate food, non-sorting labial palps, and a simplified Type II stomach and muscular gut all suggest that the species is a predator like Lyonsiella formosa. Other features of the anatomy, such as pallial taenioid muscles, radial mantle glands, and the structure of the ctenidia all point to a link between B. teramachii and the Lyonsiellidae and thus with the Verticordiidae and Parilimyidae and, therefore, with some of the oldest anomalodesmatans, the Pholadomyidae. In the possession by B. teramachii of a unique pair of antero-dorsal suspensory muscles, the link with fossil pholadomyoideans is reinforced. Bentholyonsia thus represents another genus of predatory bivalve, not only expanding our view of the prevalence of this feeding mode in the deep sea by this class but also helping us show how it evolved, in anatomical terms, from a suspension- (or deposit-) feeding ancestor.

Odonates (dragonflies) are well known for the ability of the males to displace sperm stored in the female's sperm-storage organs during copulation. By this means, copulating males are able to increase their fertilization success. This ability has been used as an example to illustrate a conflict of interests between the sexes in which males have evolved sperm-displacement mechanisms whilst females have presumably evolved means to avoid sperm displacement. The present review has four aims: (1) to describe the copulatory mechanisms used during sperm displacement; (2) to analyse the causes of sperm usage patterns; (3) to discuss this information using current hypotheses on conflict between the sexes; and (4) to illuminate topics for further research. Four copulatory mechanisms are described: sperm removal (physical withdrawal of stored sperm), sperm repositioning (‘pushing’ of rival sperm to sites where its use will be least likely), female sensory stimulation to induce sperm ejection, and sperm flushing (displacement of sperm using the copulating male's sperm). Sperm-precedence studies in Odonata are scarce and their values vary considerably between species. In those species in which sperm displacement is incomplete, the last copulating male obtains a high but variable short-term fertilization success which decreases with time. Some male and female factors affecting sperm precedence patterns are mentioned: (1) male variation in genital morphology; (2) duration of copulation influenced by the male (the longer the copulation, the more stored sperm displaced); (3) adaptations of the sperm-storage organs that allow the female to manipulate the sperm she has received (i.e. avoiding sperm displacement, re-distributing sperm masses, favouring sperm located in certain sites and ejecting sperm after copulation). We suggest that male and female odonates have co-evolved at the level of genital function with the control of stored sperm as the focus of the conflict. The benefits for males in this co-evolution lie in maximizing their fertilization success. However, it is not clear what females obtain from storing sperm and making it unreachable during sperm displacement. Two hypothetical benefits that females may obtain for which some evidence has been gathered are genetic diversity and viability genes. It is finally suggested that odonates can become excellent subjects of study for testing current ideas related to sexual conflict and speciation processes through sexual selection.

For snakes, prey size and sex are two possible determinants of head and body size. In garter snakes Thamnophis sirtalis, females are generally longer and have greater body weights than males, and also have larger relative head sizes, which may facilitate foraging success. The selective pressures that account for sexual size dimorphism in garter snakes have not been unequivocally demonstrated. In this study, the body (length and mass) and head (head length, head width, jaw length, inter-ocular distance) sizes of garter snakes inhabiting two nearby but ecologically dissimilar sites with different types of available prey were compared. Overall, the adult female snakes were larger and had greater relative head sizes than males. Males from the two sites did not differ significantly in body or head sizes. However, the mean body length and mass of females from a site where vertebrates are included in the diet were greater than that of females feeding almost exclusively on earthworms. There were also significant site differences in all four head measurements in females, although the direction of the difference varied by site. Diet-induced morphological plasticity is well documented and was evident in this study, although the relative roles of genotype, ontogeny, and competing selective forces in the expression of such plasticity can only be ascertained through future experimental studies.

Eggs of Pelodiscus sinensis were incubated under one fluctuating and four constant temperatures, and hatchlings from different incubation temperatures were maintained under identical conditions to assess the effects of incubation temperature on sexual phenotype and hatchling growth. The incubation length decreased as temperature increased, but it did not differ between sexes within each temperature treatment. Hatching success was higher at intermediate temperatures (28 °C, 30 °C and the fluctuating temperature regime) than at low (24 °C) and high (34 °C) temperatures. The sex ratio of hatchlings did not differ from equality within each temperature treatment. Thus, our data support previous work that P. sinensis does not have temperature-dependent sex determination, and add evidence for the prediction that turtles within the Trionychidae have genotypic sex determination exclusively. Incubation temperature affected hatchling mass, with hatchlings from intermediate incubation temperatures being heavier than those from low (24 °C) and high (34 °C) incubation temperatures. Hatching size was not a predictor of post-hatching growth. Incubation temperature affected hatchling growth, with hatchlings from 24 °C overall growing faster than did hatchlings from higher incubation temperatures. The influence of incubation temperature on hatchling growth was well buffered within the range of constant temperatures from 28 °C to 34 °C. Fluctuating incubation temperatures augmented male growth but reduced female growth, as female embryos were more vulnerable to extremely high temperatures.

Patterns of growth of caudal vertebrae in the chameleon Chamaeleo dilepis were determined using principal component analysis, and compared to growth of the entire tail relative to snout–vent length. Despite significant positive allometry of the whole tail, growth rates of vertebrae differed along the length of the tail. Specifically, there was a proximal region that grew positively allometrically, and an extensive distal portion that grew with negative allometry. Intervening, was a short transitional region of approximate isometry. Positive allometry of the entire tail resulted from the extensive proximal region that grew in this manner. Although the region of positive allometry extended further caudad than the m. caudofemoralis longus, m. retractor penis magnus, and m. ischiocaudalis, its extent correlated more closely with the presence of neural spines (which are used as a proxy for the extent of the m. transversospinalis) and with tail coiling in this species. The positively allometric region housed the non-segmental musculature of the tail and did not bend, and the negatively allometric region identified the portion of the tail that was prehensile.

Procellariform seabirds provide a good model for studies of the causes and consequences of variability in avian egg size, because females can only adjust reproductive investment by breeding intermittently, or by altering the size of their single egg. Maternal characteristics such as age, breeding experience and body size, as well as environmental variability, can influence egg size, but the effect of these factors has rarely been assessed simultaneously in the same study. Previous studies in Scotland have shown that the egg size of northern fulmars Fulmarus glacialis increased in relation to breeding experience. At this colony the influence of breeding experience, body size and inter-annual variability upon egg size was tested simultaneously. Data collected over seven breeding seasons between 1975 and 2002 showed that egg size varied significantly both between years and in relation to the length of the breeding experience of females, but that female body size explained most variation in egg size. Inter-annual variability in egg size was not related to the winter North Atlantic Oscillation, which had recently been shown to influence other measures of reproductive success at this colony. Larger eggs also seem to be more likely to produce successful fledglings. These findings are discussed in relation to the relative contribution of egg quality and parental quality on increased reproductive success.