A central challenge to the study of animal aerodynamics has been the measurement of forces generated by flapping wings. Relative to wings of other birds, hummingbird wings are of particular interest in that the smaller species operate in more viscous regimes (5000<Re<10 000) for which substantial drag and reduced lift:drag coefficients might be expected. Lift and drag forces were measured on mounted hummingbird wings and wing models spinning in continuous tipwise revolution about the wing base. Lift coefficients tended to increase as wing models became more realistic (i.e. with sharpened leading edges and with substantial camber). Lift:drag ratios of real wings were substantially higher than those of wing models, suggesting morphological contributions of feathers to lift enhancement and drag reduction. At Re=5000, high values of the lift:drag ratio (8–16) at low angles of attack suggest that wings of hummingbirds are exceptionally good at producing lift.

Embryos of four ovoviviparous species of Australian onychophorans were examined to establish the process of their development, their reproductive cycle and to estimate the gestation period. The process of development is the same in all four species with, in the early embryo, segment halves separated by broad bands of extra-embryonic ectoderm and the embryos growing by the posterior addition of segments. Seven developmental stages (I–VII) can be clearly identified from external morphology. Analysis of the developmental stages of the embryos present in females collected throughout a calendar year has allowed estimation of the time taken for each developmental stage and demonstrated that there is an annual reproductive cycle with a total gestation period of c. 12 months. Stages I and VII are prolonged, the latter related to the late completion of midgut development. The simultaneous presence of stage I and stage VII embryos at certain times of year indicates an overlap of generations within the uteri, which is more extensive for some species than others. As the stage VII embryos of one cohort complete their development, enlarged oocytes are released from the ovaries to become fertilized as they pass the seminal receptacles and enter the uteri to start their embryonic development to form the next cohort. Cephalofovea clandestina, Phallocephale tallagandensis and Ruhbergia bifalcata have head structures in males, Euperipatoides rowelli does not. The presence of embryos at all times of year in the uteri of mature females has implications for mating and sperm storage that are discussed.

Nipponoclava gigantea is restricted to the tropical Western Pacific waters of southern Japan at depths of between 5 and 70 m and lives in coarse sand and gravel. In many respects, N. gigantea appears to be similar to other endobenthic penicillids in that there is a true shell, the margins of which, via the intermediary of a narrow ‘saddle’, are united with an adventitious tube. This has a large watering pot anteriorly and pleated ruffles, representing either growth or repair events, posteriorly. Nipponoclava gigantea differs from other penicillids, however, in that its true shell is large, i.e. ∼20 mm high as compared to 2–3 mm, and the angle of valve splay is ∼80° as opposed to 180°. Internally the shell has a wide pallial line and shallow pallial sinus and there are anterior adductor muscle scars. There are possibly posterior adductor muscle scars also. These are not present in the adult animal, however, although the anterior adductor is. Also present are paired anterior and (possibly) posterior pedal retractor muscles, the latter having a nervous union with the visceral ganglia to create simple stretch or tonus proprioreceptors. It is argued that N. gigantea provides clues about how the tube-dwelling lifestyle has evolved in the various taxa of the Penicillidae. It is suggested that through a process of heterochrony, in which the animal produces its adventitious tube at progressively earlier and earlier developmental stages, the true shell has become actually and relatively smaller and smaller and, hence, more splayed in more derived penicillids. Nipponoclava gigantea is thus an important link between an hypothetical lyonsiid ancestor and the more specialized penicillids and helps us to understand the adaptive radiation of this group of tube-dwelling bivalves.

Nesting hawksbill turtles Eretmochelys imbricata and their eggs and young were studied on Cousine Island, Seychelles from 1995 to 1999. Numbers of females known to nest (tagged individuals) on Cousine was 146. An average of 75% of emerging adults were intercepted, and this rose to 81.6% in 1999. Mean carapace lengths and widths of adult females were 81.2×60.8 cm, and included some of the longest carapace lengths known for hawksbill turtles. There were poor correlations between adult weight and carapace length or width, but better correlations between adult weight and the product of carapace length and width. Width to length carapace proportions averaged 0.75. The mean weight of nesting females before their first recorded nesting on Cousine was 65.6 kg (51.2–83.0 kg). These were the first recorded weights for nesting hawksbills from the Seychelles. Individuals lose 8.5–15% of their body weight after laying three to five clutches. Mean clutch size was 176.7, and clutch sizes for any season showed great variation for some individuals. Clutch sizes tended to decrease after the main nesting month for the population but not necessarily for the individual. The largest clutch size of 264 is the largest recorded for hawksbill turtles worldwide. Turtles with longer carapaces tended to lay larger clutches than those with shorter carapaces, and heavier turtles generally laid heavier clutches than did lighter turtles. Eggs were usually (85.6%) somewhat elongate, measuring on average 36.3×35.5 mm, and weights averaged 25.5 g. Very few ‘pea’ eggs were found. The average hatchling weight was 14.5 g and the average carapace length and width were 39.2 and 30.1 mm, giving a mean ratio of carapace length to width of 0.77.

Nesting hawksbill turtles Eretmochelys imbricata were studied on Cousine Island, Seychelles from 1995 to 1999. Mean overall incubation time averaged 58.1 days. Clutch size did not influence incubation periods. Following hatching, hatchlings took an average of 3.8 days to leave the nest. Mean hatchling emergence time was 60.4 days. Hatching success averaged 64.3% for the four seasons. During 1996–97 there were heavy, unexplained egg losses due to crab predation. Excluding that season, average hatching success was 70.9%. Overall hatchling success was 61.1%, translocated nests having a better success (69.3%) than natural nests (57.7%). Overall egg and hatchling losses were 35.8% and 3.1%, respectively, most egg losses being attributed to ghost crabs Ocypode cordimana (16.3% overall) and unknown causes (17.0% overall), which were mainly non-viable eggs. The high level of nest manipulation was believed to be justified by increasing the number of hatchlings entering the sea.

Dikerogammarus villosus, a freshwater invasive amphipod, exhibits conspicuous pigmentation polymorphism. This polymorphism is documented in two recently colonized areas, the Saône and Moselle rivers (north-eastern France), and some of the mechanisms by which pigmentation polymorphism can arise and be maintained are addressed. Body size, reproductive status, fecundity and mate choice are compared among morphs of D. villosus in field samples collected in summer 2001. Body size and female gonad developmental stage were comparable among the different morphs, suggesting that polymorphism is not the result of changes in pigmentation with age or moult-cycle. Fecundity and reproductive status (paired vs non-paired) were not affected by pigmentation morph either. A random combination of morphs in pre-copula pairs was observed, showing that the colour pattern does not play a major role in mate choice. A strong size-assortative pairing was found, and this pattern was similar among male morphs. Overall, our study shows that morph polymorphism is not related to different stages in the moult cycle or the life cycle, and is not maintained by morph-assortative pairing. Alternative explanations to the mate choice hypothesis for the maintenance of pigmentation polymorphism are discussed.

Insights into the reproductive strategies of crabeater seals Lobodon carcinophagus were obtained from satellite-linked dive recorders deployed during the breeding season. All of the three females and seven males on which instruments were deployed hauled out continuously for extended periods of up to 24 days. The duration of extended haulout is consistent with a lactation period of around 3 weeks. In two cases where dive recorders were deployed on a male and female in the same group, the two animals stayed together on the ice continuously and entered the water at exactly the same time when extended haulout ceased. In both cases the male and female became geographically separated within a short time after entering the water, indicating that the association did not last beyond the period on the ice. Some males had multiple periods of extended haulout, suggesting they may try to find more than one female with which to mate. An optimal reproductive strategy with regard to the time spent on the ice may balance the conflicting needs of a short time imposed by the availability of breeding habitat and a long time to increase the reproductive success of males and females by finding more, or choosing between, mates.

All else being equal, ectotherms should maintain body temperatures (Tbs) favourable for temperature-sensitive biological functions, such as digestion and locomotion. Physical environments in the temperate zone are often thermally variable, however, thus making it difficult to maintain optimum Tbs. Radiotelemetry and a semi-natural enclosure were used to monitor Tbs of grass snakes Natrix natrix at Canterbury, Kent, U.K. Operative temperatures (Tes) were measured using snake models (copper-pipe models) placed in a variety of microhabitats to determine availability of thermoregulatory opportunities. A modification of Huey & Slatkin's (1976) regression model, piecewise regression, was used to evaluate thermoregulatory behaviour. Grass snakes could achieve high mean Tbs (>30°C) most often during midday (08:00–20:00), but only for 55–61% of the study period. Overall, non-gravid snakes maintained higher and less variable mean daytime Tbs than gravid snakes. From piecewise regression, it was determined that grass snakes initiated thermoregulation at a Te of 38.44°C, corresponding to a Tb of 27.7°C. Three main conclusions can be drawn from this study: (1) thermoregulatory opportunities for grass snakes were limited; (2) nonetheless, when conditions were sufficiently warm, there was clear evidence that grass snakes could thermoregulate; (3) contrary to expectation, gravid females actually maintained lower and more variable Tbs than non-gravid females. The consequences of these thermoregulatory patterns for the fitness of snakes have yet to be determined.

Many species of lizard use tail autotomy to escape from potential predators. While frequency of tail loss is an unreliable indicator of predation intensity it may enable inter-populational comparisons of predation costs. This reasoning was applied to a study of the metallic skink Niveoscincus metallicus. A total of 368 lizards was sampled from across four populations to compare the frequency and position of tail loss and ultimately to examine whether the implications of tail autotomy differ between populations. The overall frequency of tail loss was 72%, although between populations the incidence of tail autotomy varied from 61.4% (Laughing Jack Lagoon) to 78.2% (Dynnyrne). No sexual differences were observed in the frequency of tail loss; however, the incidence of autotomy increased with age. The estimated position of tail loss did not vary between the sexes, although individuals from Dynnyrne experienced more proximal tail breaks than the other populations. This resulted in the predicted energetic cost of tail loss being significantly higher in the Dynnyrne population and, when combined with a high frequency of tail loss and relatively smaller body size, suggests that this population incurs relatively high costs as a result of autotomy. Overall, measures of tail loss in N. metallicus were found to be useful for examining inter-populational variation in the cost of tail autotomy.

Pup mortality and the timing of birth of South American sea lions Otaria flavescens were investigated to determine the possible relationship between fluctuations in prey availability in the Peruvian upwelling ecosystem and current and future reproductive success of sea lions during six consecutive breeding seasons. Our study from 1997 to 2002 encompassed the strongest El Niño on record and one La Niña event. Pup mortality ranged from 13% before El Niño to 100% during El Niño, and was negatively correlated with prey availability. Abortions were also more frequent when prey availability was low. However, pup mortality remained high following El Niño due to the punctuated short-term effects it had on population dynamics and subsequent maternal behaviour. Births occurred later in the season after years of low food availability and earlier following years of high food availability. The peak of pupping occurred around the peak of mortality in all years, and may have been the product of intensive competition between bulls at the peak of the breeding season. The stronger and more frequent El Niños that appear to be occurring along the Peruvian coast may produce significant stochastic changes in future births and pup mortality, which may place the vulnerable South American sea lion population in Peru at greater risk.

Journal of Zoology Volume 260 Part 4, August 2003 (pages 391–403)

Journal of Zoology Volume 263 Part 1, May 2004 (pages 31–39)