Sperm-dependent parthenogenetic animals require sperm from an ‘altruistic’ mate in order to trigger embryogenesis, but without genetic contribution from the sperm donor. The stability of sperm donation is puzzling, particularly in populations that consist of sperm-dependent parthenogenetic hermaphrodites. Here, selection should favour total reduction of the male function, which would lead to population extinction. We investigated mating behaviour in a population of the sperm-dependent parthenogenetic, hermaphroditic flatworm Schmidtea polychroa. In this species, parthenogens possess a fully functional male reproductive system. We predicted that individuals should trade sperm and hence, only donate when receiving sperm from their partner. Results from 54 pairs indicate that conditional reciprocity is common, possibly even more so than in previously studied sexual conspecifics. In contrast to sexuals, however, parthenogens do not increase allocation to sperm with body size. Taken together, the data indicate that in order to receive sperm and ensure full maternal fertility, parthenogenetic S. polychroa must be able to produce and donate a minimum of self-sperm. As such, sperm trading contributes to the stability of apparently ‘altruistic’ sperm donation. This study is also the first convincing example of sperm trading in internally fertilizing hermaphrodites with a strong preference for the female role.

Journal of Zoology, Volume 258, Part 4, December 2002 (pages 459–468)

‘Effects of seed masting of bilberry, oak and spruce on sympatric populations of bank vole (Clethrionomys glareolus) and wood mouse (Apodemus sylvaticus) in southern Norway’, by Vidar Selås, Erik Framstad and Tor K. Spidsø

Echolocation calls of 10 species of rhinolophid and four species of hipposiderid bats were recorded in China. Close negative relationships were found within Rhinolophidae and Hipposideridae between call frequency and ear length. Multiple regression and residual analysis were used to evaluate the influences of forearm length and ear length on call frequency and ear size. Ear length proved to be a more important morphological parameter influencing the call frequency in rhinolophids but not in hipposiderids. Ears are largely shaped by echolocation calls in both families. The influence of body size on ear size was significant in rhinolophids but not in hipposiderids, and the enlarged ears of rhinolophids correlated with the lower frequencies that rhinolophids used relative to larger body size.

The effects of UV-A and UV-B (Cracow District, Poland, 50°04′N, 19°57′E; 220 m a.s.l.) on oxygen consumption were studied in common toad Bufo bufo (L.) tadpoles (Gosner stage 27). Ecologically relevant chronic doses of UV were simulated in the laboratory. Larvae separated for experiment were derived from UV-exposed or not exposed embryos. After hatching, tadpoles in stages 24–27 were treated with UV-A or UV-B. UV-A caused significant increases in oxygen consumption in larvae grown from untreated embryos, whereas no changes occurred in tadpoles irradiated with UV-A during embryonic and larval development. UV-B caused significant decreases in oxygen consumption in all exposed tadpoles. The changes were larger in larvae derived from eggs not exposed to UV-B than in tadpoles grown from UV-B-treated embryos. Our results suggest that ambient levels of UV-A and especially UV-B may affect the metabolic rate of common toad larvae living in shallow habitats. Affected respiration may retard development as well as increase the susceptibility of tadpoles to ecologically relevant pathogens. On the other hand, it seems that UV-irradiation induces some adaptive processes during embryonic development, which increase the resistance of the larval respiratory system to solar UV radiation.

The breeding biology and social system of the eclectus parrot Eclectus roratus, a species with a unique form of sexual dichromatism (red and blue females, green males) was examined. Our 4-year study at Iron Range National Park on Cape York Peninsula, Australia, showed that females guarded their nest hollows in emergent rainforest trees for up to 9 months each year, often starting well before they laid their first clutches early in the dry season. During this time they rarely left the nest and relied on males for food, both for themselves and their nestlings. Intrasexual competition for scarce hollows and the threat of egg destruction by other eclectus parrots may explain this extreme guarding behaviour. Reproductive success was low. The combined effects of egg and chick loss to conspecifics and predators, brood reduction and flooding of hollows from heavy rain meant that only 18% of eggs and 27% of clutches produced a fledgling. Over 4 years, reproductive success amongst females was strongly skewed: 39% of females were never successful, and only 29% produced more than one fledgling per year. Eclectus parrots were found to breed co-operatively with as many as five males feeding a single female at the nest. Multiple mating, involving one female and four males, was observed once. Despite an even sex ratio at fledging, the adult sex ratio was strongly male-biased, suggesting higher mortality of females. Our data shows that reproductive variance for females is high, and suggests that a shortage of tree hollows and eligible females may enforce co-operative breeding amongst males.

Pre-weaning pup mortality of grey seals Halichoerus grypus in a breeding colony (North Rona, Scotland, U.K.) was examined in relation to the density of local adult females over two breeding seasons. Accurate, fine-scale maps of daily seal locations within a GIS database permitted the extraction of measures of female density determined at a range of spatial scales from 5 to 50 m around each pup on the date of death. Adult densities around live pups provided the null distribution of adult densities, which were tested against the distribution of densities where deaths occurred. Pre-weaning pup mortality at this colony was not related to any of our density measures. The proportion of pups dying each day showed no seasonal trends. Analysis of topographic features from a sub-meter digital terrain model for locations where deaths occurred suggested that there were fewer mortalities in prime pupping habitats. This could have been a direct effect of habitat or the relative quality of mothers in these habitats. The distance separating mothers and pups tended to be greater on the periphery of the colony compared to more central areas. Pups in the peripheral areas may be more exposed to predation by gulls.

A description is given of the external morphology of a single young caecilian (gymnophionan) amphibian from the North Pare Mountains, Tanzania, referable to Scolecomorphus vittatus (Boulenger, 1895). This is the smallest known free-living Scolecomorphus, and it is characterized by many remarkable features previously unrecorded for any life-history stage of any caecilian. The cheeks have conspicuous, posteroventrally divergent paraoral processes that border a concavity on the ventral surface of the snout. The mandibles are very flexible about their articulation with the cranium, and they have a broader curvature than the upper jaw. The dentition is heterogeneous, with adult-like monocusped teeth in single rows, but also some supernumerary teeth, some of which are bicornute. The posterior parts of the paraoral processes bear a small number of monocuspid teeth that lie outside, and project away from, the mouth. The nuchal region of the body bears a distinctive concavity on the underside of the throat, bordered by longitudinal ridges that terminate in fleshy nipples. All of these features are unknown in adult Scolecomorphus, and many are unique for caecilians, and they suggest a highly distinctive life-history stage. The discovery and description of this specimen adds substantially to the currently meagre information on the life history of scolecomorphids and of the diversity of caecilian reproductive biology. Two modes of viviparity in caecilians are identified, with S. vittatus resembling the caeciliid Geotrypetes in giving birth to small altricial young that seem to require extended post-parturition parental care.

Plucking analysis is a standard method for assessing the breeding season diet of goshawks Accipiter gentilis. Results may be biased, however, due to differences in the detectability of remains of certain prey species and to selective prey transportation by hawks. This study investigated prey choice of three goshawk breeding pairs in the city of Hamburg, Germany, during 1997–99. Predation data obtained by continuous radio-monitoring of the adult males were used to quantify biases of simultaneous plucking analyses, which were conducted in the nesting territories of the corresponding breeding pairs. A comparison of estimated average food requirements with actual biomass intake observed in two of the monitored goshawks (with sufficient sample sizes) indicated that it was possible to record virtually all kills that occurred during tracking sessions. Therefore, radio-tracking data could be used to evaluate the accuracy of plucking analysis. Comparisons showed that the proportions of small birds and of feral pigeons Columba livia f. domestica were underestimated by the scanning method by 10% and 13%, respectively. The latter finding was unexpected as pigeons have large, conspicuously coloured feathers that are easy to detect. However, as goshawks plucked large prey more thoroughly at the capture site than smaller prey, a comparatively small number of their feathers were present in the nesting areas. This source of bias in plucking analysis has passed unnoticed in previous studies. It may have important implications for the interpretation of results of future projects that aim to estimate predation rates in goshawks and other bird-eating raptor species.

Growth in length and weight of a large sample of crabeater seals Lobodon carcinophagus collected over the period 1967–78 is reported. Growth in dorsal standard length of 1146 seals (490 males, 656 females) from 0.5 to 20 years of age was similar to the pattern seen in other phocid seals. Length was plotted against age and Gompertz curves fitted to the data. Growth rates were estimated from the derived equations: males, y = 231.9 − 58.7 e−0.55t; females, y = 236.8 − 63.6 e−0.44t. The asymptote is at approximate length 234 cm and age 10 years in both males and females. Body weights were recorded for 249 seals aged from 0.5 to 20 years, of which reliable age estimates for 230 (100 males, 130 females) were available. Rates of growth in body weight were estimated from the derived equations: males, y = 200.0 − 94.1 e−0.48t; females y = 212.4 − 116.2 e−0.40t. The best estimate of body weight from linear body measurements is obtainable from a predictive equation relating body weight, length and axillary girth, determined by maximum likelihood: W = 0.000046 LG2 (W, body weight; L, dorsal standard length; G, axillary girth). There was no significant difference between the sexes. Seasonal variations in body condition could not be determined because all animals were sampled in February and March. However, inter-year differences in recovery of body condition of adults, following the demands of breeding and moulting in the spring and summer, were observed. The data represent a unique time series covering the 1960s and 1970s. In terms of global climate change they should provide a valuable baseline for future studies.