The Editors are pleased to report another successful year for the Journal of Zoology in 2003. During the year we received 257 submissions and published 140 papers in volumes 259–260; and our rejection rate for the period was 45%. Our aim to attract a truly international set of contributors has been met once again, with papers from 41 countries being submitted during 2003.

Some anurans have a peculiar casqued head with the skin co-ossified with the underlying bones. This type of skull usually is associated with phragmosis, a protective behaviour in which the animal enters a hole and closes it with the head. Although co-ossification of the head in lissamphibians frequently has been associated with water economy, recent studies of Corythomantis greeningi, a casque-headed tree frog from semi-arid areas in north-eastern Brazil, suggest that cranial co-ossification contributes little to conservation of water in the frog. Instead, during phragmotic behaviour, the co-ossified head protects the animal against predators and indirectly enhances water balance. Thus, the primary role of co-ossification is defence, a hypothesis that is the focus of this study, which describes the morphology of the head of C. greeningi with an emphasis on the co-ossification and the venom glands. We report on behavioural features and on the toxicity of the cutaneous secretion produced by the abundant venom glands that are associated with large spicules on the skull.

The small mammal fauna of a forest area in southern Nigeria is studied in order to understand the general patterns regulating the community composition. A set of different methods of trapping was used in order to evaluate the composition of the species at the level of both the ground-dwelling and the arboreal guilds. For the Insectivora, six shrew species were trapped, but only two (Crocidura nigeriae and C. poensis) appeared abundant and widespread in the various habitat types. No arboreal species were found. For the rodents, 17 species were captured, which were arranged by a Principal Component Analysis into four groups: (1) Rattus rattus and Anomalurus derbianus; (2) Xerus erythropus and Grammomys rutilans; (3) Graphiurus cf. murinus and Hylomyscus stella; (4) the remaining, more generalist species. For the ground-dwelling rodents, 14 species were found, which were arranged in three groups: (1) Malacomys edwardsi and Grammomys sp.; (2) Mylomys dybowskii and Rattus norvegicus; (3) all the other species, with stronger similarities between Praomys tullbergi, Mus musculoides, Aethomys sp. (unknown), and Lemniscomys striatus. Although an approximately equal number of species constituted the arboreal and ground-dwelling rodent fauna, the number of trapped animals was much higher on the ground than at the level of the arboreal guild (ratio 8.7: 1; total n=2322). The general implications of the patterns observed are discussed.

The honey badger, or ratel, Mellivora capensis has not been well studied and data on life-history variables have previously been incomplete and contradictory. Here we present data on life-history variables that were collected from visual observations as part of the first intensive study of free-living honey badgers (25 radio-marked individuals) and we make comparisons with other similarly sized mustelids (5–25 kg). The honey badger is a non-social species and only the mother rears the young. The data do not support delayed implantation as gestation was a maximum of 50–70 days with the unusually small litter size of one cub. The long time to independence of both male and female cubs (12–16 months) resulted in birth intervals longer than 12 months with no distinct breeding season. Overall the honey badger appears to have a more K-selected life history compared to other species within the Mustelidae.

Radio-tracking locations of 25 individuals (13 females; 12 males) and visual observations of nine habituated individuals were used to investigate the spatial organization and movement patterns of the honey badger Mellivora capensis in the southern Kalahari. The home ranges of adult male honey badgers (541±93 km2) were significantly larger than the home ranges of adult females (126±13 km2). Female home-range size was five times larger than predicted from body mass. The extensive home ranges of females were likely to be a function of relatively low prey availability in the semi-arid Kalahari and the long period of cub dependence (12–16 months). While mean home-range overlap in females was moderate (13%) and home-range centres were regularly spaced, females did not appear to actively defend a territory and no direct interactions between females were observed. Scent marking appears to mediate spatio-temporal separation and females show a loosely territorial spacing pattern. In contrast, males did not support the typical mustelid pattern of intra-sexual territoriality but instead encompassed the overlapping home ranges of up to 13 females. Males and females differed significantly in their rate of travel (3.8±0.3 km/h vs 2.7±0.2 km/h), straight line (6.2±0.5 km vs 2.4±0.2 km) and actual distance (13.8±0.9 km vs 7.7±0.7 km) moved during an active period but do not differ in the percentage of their home-range area traversed in a single day (3%). Young males tended to have smaller home ranges (151±45 km2) than adult males and showed a spacing pattern more similar to adult females than adult males. In common with other solitary mustelids, the spatial organization suggests a polygynous or promiscuous mating system.

Geese have to satisfy the high energy demands of flight with a low-energy and bulky food. When feeding on food items that are concentrated and widespread, as is the case in geese, an individual's instantaneous intake rate is largely determined by its bite size. Inter-individual variation in bite size was measured in barnacle geese Branta leucopsis, with the hypotheses that bite size would scale with (sward height)a, where 0<a<1, and (bill length)b, where b=3.0, and that there would be a positive interaction between these explanatory variables. Using a generalized linear mixed modelling analysis, bite size was found not to vary over the measured sward heights, whilst bite size was found to scale with bill length to the power b=14.24 (SE=2.05). There was no significantly detectable interaction between these terms, indicating that barnacle geese with longer bills had larger bite sizes over the full range of sward heights studied. Bill length scaled with body mass to the power 0.21 (SE=0.01). Combining this with the scaling of bite size to bill length, we conclude that bite size scales with body mass to the power 2.99. Our results suggest that larger barnacle geese have a disproportionately larger bite size than smaller geese, which may explain the fitness advantages of larger geese observed in other studies. However, smaller geese may resist this selection pressure by selectively consuming more nutritious plant parts or altering their bite rates.

The ability of a living organism to perform specific actions such as prey capture or predator avoidance is a critical feature that should affect individual fitness. Snakes have an elongate morphology that lacks the regional variation associated with girdles found in limbed vertebrates. In this context, this group offers interesting opportunities to study specific forms and functions. In this study, we examined musculature in a medium-sized boid snake, the Colombian rainbow boa Epicrates cenchria maurus, by combining two methods: magnetic resonance imaging (MRI) and calliper measurements after axial palpation. The MRI demonstrated an important development of epaxial musculature consistent with the predatory mode of constriction. We showed that MRI and palpation data were strongly correlated, indicating that musculature is an easily measurable phenotypic feature in the studied species. The calliper method was then applied in combination with assessments of physical performance (constriction and defence capabilities) in a group of snakes after a prolonged fast and again after a re-feeding period. A clear relationship was detected between dorsal musculature and both maximal traction and constriction forces. Re-feeding significantly increased dorsal musculature and traction capabilities. While musculature assessments are classically difficult to achieve among tetrapods, this study suggests that snakes are interesting models for examining variation in musculature and performance in natural and experimental conditions.

Variation in life history is a central key to understanding population dynamics, and density dependence and climate are important factors in shaping life-history variation in ungulates. Early growth is often sensitive to adverse conditions and this may in turn affect juvenile survival and age at first reproduction. We report variation in body weight of 5079 reindeer Rangifer tarandus from North Ottadalen, a very productive reindeer area in Norway, sampled over 14 years in the period 1967–1989. The North Ottadalen reindeer herd was established in 1964 from a winter herd of some 500 semi-domestic reindeer, and allowed to grow to a peak of over 3300 reindeer in 1974, after which increased harvest decreased the population size. The proportion of lactating yearling females varied between 0% and 50%. Lactating females had lower autumn body weights than non-lactating females. A decline in body weight with age, i.e. senescence, was evident in both males and females from around 7 to 9 years of age. Body weights of all age and sex groups as well as the proportion of yearling females lactating decreased over time, and more so in younger than older males, although the population size declined markedly after the population peak in 1974. We found no effect of the North Atlantic Oscillation or local weather on body weight. The possible causes of the marked decline in performance with time in the North Ottadalen reindeer herd are discussed, and it is suggested that this may be related to the transition from being managed as semi-domestic to wild (i.e. hunted).

Variation in size of home range is among the most important parameters required for effective conservation and management of a species. However, the fact that home ranges can vary widely within a species makes data transfer between study areas difficult. Home ranges of Eurasian lynx Lynx lynx vary by a factor of 10 between different study areas in Europe. This study aims to try and explain this variation in terms of readily available indices of prey density and environmental productivity. On an individual scale we related the sizes of 52 home ranges, derived from 23 (9:14 male:female) individual resident lynx obtained from south-eastern Norway, with an index of density of roe deer Capreolus capreolus. This index was obtained from the density of harvested roe deer within the municipalities covered by the lynx home ranges. We found a significant negative relationship between harvest density and home-range size for both sexes. On a European level we related the sizes of 111 lynx (48:63 male: female) from 10 study sites to estimates derived from remote sensing of environmental productivity and seasonality. A multiple linear regression model indicated that productivity of the study site had a clear negative relationship with home-range size. At both scales, sex emerged as a significant explanatory variable with males having larger home ranges than females. In addition, the size of male home-ranges increased faster with decreasing prey density than for females. These analyses support widely held predictions that variation in home-range size is due to variation in prey density.

Yellow-bellied marmots Marmota flaviventris were live-trapped and marked in the East River Valley of Colorado from 1962 to 1998. For females, static life tables were calculated each year from 1967, when ages were well known, to 1997. Population density was determined, and from life tables calculations were made of: survivorship of young, yearlings and adults; percentage of females producing litters; mean and variance of litter size; net reproductive rate (Ro); and generation length. From climate records a set of 14 annual weather variables was developed that described temperature, precipitation and lengths of growing season and winter. Data from 1981 and 1996 were not used since weather data contained extreme outliers in date of last snow cover. Univariate correlation matrices were calculated among weather variables, among demographic variables, and between weather and demographic variables. Mean temperature in 24 of 29 years was cooler than long-term average temperature. Generation length increased during the years of the study. Weather data were used as independent variables with each dependent demographic variable to calculate nine multiple correlation and regression models. Models explained from 0% to 58% of the variation in demography. Significant factors in each model were mostly interpreted as affecting availability of energy necessary for successful hibernation and reproduction.

Sex ratios of the American snapping turtle Chelydra serpentina are female-biased at cool temperatures, male-biased at moderate temperatures, and only females are produced at warm temperatures. The laboratory incubation of eggs at several constant temperatures yields patterns of skewed sex ratios. In this study, incubated eggs represented regional samples of C. serpentina from six different latitudes. The sample from the highest latitude yielded male-biased sex ratios across the broadest range of cool temperatures. This male-biased zone and those of the other five samples collectively contributed to a nested arrangement that is approximately symmetrical around a temperature of 24.5°C. Two indices of temperature-dependent sex determination (TSD) patterns (MF pivotal temperature, width of the male-biased zone) were significantly associated with latitude and with published data on several climatic variables (e.g. sunshine and rainfall). At high latitudes, females nest in exposed locations, locally the warmest places. At low latitudes females place their nests in shaded locations. Such nest site selection renders high latitude nests warmer than low latitude nests, even if only intermittently. Given that constant conditions show faster embryogenesis in high vs low latitude eggs, exposed nest sites seem to be an additional adaptation to hasten embryogenesis in high latitude nests. At low latitudes, shading prevents nests from overheating. We propose that a trade-off between evolution, (1) to balance sex ratio and (2) to maintain male-biased sex ratios in a temperature range that favours male fitness, leads to the observed arrangement of concentric TSD patterns centred around male production at 24.5°C.

In most species, females invest more in their offspring than males. In mammals, this also holds true after the birth of young since only mothers can lactate and fathers are thus more likely to desert and seek additional mating opportunities. These opportunities are largely dependent on resource distribution and the resulting distribution of females. The emerging social and mating systems of different species give rise to different benefits of investment in paternal care. Paternal care should have evolved in relation to the frequency of losing paternities to other males. Hence, in species living in one-male systems with little opportunity for female extra-pair copulations, paternal care should be more common than in those species living in multi-male groups. The guinea pigs (Caviinae) comprise closely related species exhibiting different social organizations and mating systems. The amount of paternal behaviour and offspring-directed aggression was investigated in three species kept under laboratory conditions: the polygynous Cavia aperea, the promiscuous Galea musteloides and a newly described monogamous species (Galea monasteriensis sp. nov.). All animals were kept in groups of one adult male and one adult female with their non-weaned offspring. Cavia aperea as well as G. monasteriensis males showed a high incidence of paternal behaviour, which consisted primarily of playing with offspring and grooming them. In contrast, G. musteloides males never engaged in paternal behaviour but directed more aggressive behaviour towards their offspring. Mating with multiple partners and multiple paternities are common in G. musteloides whereas in the former two species there is a much higher certainty of paternity. We conclude that paternal behaviour in guinea pigs probably co-evolved in alignment with the certainty of paternity that males of a species encounter under natural conditions.